Apparatus for simultaneously disreefing a centrally reefed clustered parachute system
Johnson, Donald W.
1988-01-01
A single multi-line cutter is connected to each of a cluster of parachutes by a separate short tether line that holds the parachutes, initially reefed by closed loop reefing lines, close to one another. The closed loop reefing lines and tether lines, one from each parachute, are disposed within the cutter to be simultaneously cut by its actuation when a central line attached between the payload and the cutter is stretched upon deployment of the cluster. A pyrotechnic or electronic time delay may be included in the cutter to delay the actual simultaneous cutting of all lines until the clustered parachutes attain a measure of stability prior to being disreefed. A second set of reefing lines and second tether lines may be provided for each parachute, to enable a two-stage, separately timed, step-by-step disreefing.
Apparatus for simultaneously disreefing a centrally reefed clustered parachute system
Johnson, D.W.
1988-06-21
A single multi-line cutter is connected to each of a cluster of parachutes by a separate short tether line that holds the parachutes, initially reefed by closed loop reefing lines, close to one another. The closed loop reefing lines and tether lines, one from each parachute, are disposed within the cutter to be simultaneously cut by its actuation when a central line attached between the payload and the cutter is stretched upon deployment of the cluster. A pyrotechnic or electronic time delay may be included in the cutter to delay the actual simultaneous cutting of all lines until the clustered parachutes attain a measure of stability prior to being disreefed. A second set of reefing lines and second tether lines may be provided for each parachute, to enable a two-stage, separately timed, step-by-step disreefing. 13 figs.
Coral mucus fuels the sponge loop in warm- and cold-water coral reef ecosystems
Rix, Laura; de Goeij, Jasper M.; Mueller, Christina E.; Struck, Ulrich; Middelburg, Jack J.; van Duyl, Fleur C.; Al-Horani, Fuad A.; Wild, Christian; Naumann, Malik S.; van Oevelen, Dick
2016-01-01
Shallow warm-water and deep-sea cold-water corals engineer the coral reef framework and fertilize reef communities by releasing coral mucus, a source of reef dissolved organic matter (DOM). By transforming DOM into particulate detritus, sponges play a key role in transferring the energy and nutrients in DOM to higher trophic levels on Caribbean reefs via the so-called sponge loop. Coral mucus may be a major DOM source for the sponge loop, but mucus uptake by sponges has not been demonstrated. Here we used laboratory stable isotope tracer experiments to show the transfer of coral mucus into the bulk tissue and phospholipid fatty acids of the warm-water sponge Mycale fistulifera and cold-water sponge Hymedesmia coriacea, demonstrating a direct trophic link between corals and reef sponges. Furthermore, 21–40% of the mucus carbon and 32–39% of the nitrogen assimilated by the sponges was subsequently released as detritus, confirming a sponge loop on Red Sea warm-water and north Atlantic cold-water coral reefs. The presence of a sponge loop in two vastly different reef environments suggests it is a ubiquitous feature of reef ecosystems contributing to the high biogeochemical cycling that may enable coral reefs to thrive in nutrient-limited (warm-water) and energy-limited (cold-water) environments. PMID:26740019
Coral mucus fuels the sponge loop in warm- and cold-water coral reef ecosystems.
Rix, Laura; de Goeij, Jasper M; Mueller, Christina E; Struck, Ulrich; Middelburg, Jack J; van Duyl, Fleur C; Al-Horani, Fuad A; Wild, Christian; Naumann, Malik S; van Oevelen, Dick
2016-01-07
Shallow warm-water and deep-sea cold-water corals engineer the coral reef framework and fertilize reef communities by releasing coral mucus, a source of reef dissolved organic matter (DOM). By transforming DOM into particulate detritus, sponges play a key role in transferring the energy and nutrients in DOM to higher trophic levels on Caribbean reefs via the so-called sponge loop. Coral mucus may be a major DOM source for the sponge loop, but mucus uptake by sponges has not been demonstrated. Here we used laboratory stable isotope tracer experiments to show the transfer of coral mucus into the bulk tissue and phospholipid fatty acids of the warm-water sponge Mycale fistulifera and cold-water sponge Hymedesmia coriacea, demonstrating a direct trophic link between corals and reef sponges. Furthermore, 21-40% of the mucus carbon and 32-39% of the nitrogen assimilated by the sponges was subsequently released as detritus, confirming a sponge loop on Red Sea warm-water and north Atlantic cold-water coral reefs. The presence of a sponge loop in two vastly different reef environments suggests it is a ubiquitous feature of reef ecosystems contributing to the high biogeochemical cycling that may enable coral reefs to thrive in nutrient-limited (warm-water) and energy-limited (cold-water) environments.
Microbial and sponge loops modify fish production in phase-shifting coral reefs.
Silveira, Cynthia B; Silva-Lima, Arthur W; Francini-Filho, Ronaldo B; Marques, Jomar S M; Almeida, Marcelo G; Thompson, Cristiane C; Rezende, Carlos E; Paranhos, Rodolfo; Moura, Rodrigo L; Salomon, Paulo S; Thompson, Fabiano L
2015-10-01
Shifts from coral to algae dominance of corals reefs have been correlated to fish biomass loss and increased microbial metabolism. Here we investigated reef benthic and planktonic primary production, benthic dissolved organic carbon (DOC) release and bacterial growth efficiency in the Abrolhos Bank, South Atlantic. Benthic DOC release rates are higher while water column bacterial growth efficiency is lower at impacted reefs. A trophic model based on the benthic and planktonic primary production was able to predict the observed relative fish biomass in healthy reefs. In contrast, in impacted reefs, the observed omnivorous fish biomass is higher, while that of the herbivorous/coralivorous fish is lower than predicted by the primary production-based model. Incorporating recycling of benthic-derived carbon in the model through microbial and sponge loops explains the difference and predicts the relative fish biomass in both reef types. Increased benthic carbon release rates and bacterial carbon metabolism, but decreased bacterial growth efficiency could lead to carbon losses through respiration and account for the uncoupling of benthic and fish production in phase-shifting reefs. Carbon recycling by microbial and sponge loops seems to promote an increase of small-bodied fish productivity in phase-shifting coral reefs. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.
Reefing Line Tension in CPAS Main Parachute Clusters
NASA Technical Reports Server (NTRS)
Ray, Eric S.
2013-01-01
Reefing lines are an essential feature to manage inflation loads. During each Engineering Development Unit (EDU) test of the Capsule Parachute Assembly System (CPAS), a chase aircraft is staged to be level with the cluster of Main ringsail parachutes during the initial inflation and reefed stages. This allows for capturing high-quality still photographs of the reefed skirt, suspension line, and canopy geometry. The over-inflation angles are synchronized with measured loads data in order to compute the tension force in the reefing line. The traditional reefing tension equation assumes radial symmetry, but cluster effects cause the reefed skirt of each parachute to elongate to a more elliptical shape. This effect was considered in evaluating multiple parachutes to estimate the semi-major and semi-minor axes. Three flight tests are assessed, including one with a skipped first stage, which had peak reefing line tension over three times higher than the nominal parachute disreef sequence.
A Bayesian-based system to assess wave-driven flooding hazards on coral reef-lined coasts
Pearson, S. G.; Storlazzi, Curt; van Dongeren, A. R.; Tissier, M. F. S.; Reniers, A. J. H. M.
2017-01-01
Many low-elevation, coral reef-lined, tropical coasts are vulnerable to the effects of climate change, sea level rise, and wave-induced flooding. The considerable morphological diversity of these coasts and the variability of the hydrodynamic forcing that they are exposed to make predicting wave-induced flooding a challenge. A process-based wave-resolving hydrodynamic model (XBeach Non-Hydrostatic, “XBNH”) was used to create a large synthetic database for use in a “Bayesian Estimator for Wave Attack in Reef Environments” (BEWARE), relating incident hydrodynamics and coral reef geomorphology to coastal flooding hazards on reef-lined coasts. Building on previous work, BEWARE improves system understanding of reef hydrodynamics by examining the intrinsic reef and extrinsic forcing factors controlling runup and flooding on reef-lined coasts. The Bayesian estimator has high predictive skill for the XBNH model outputs that are flooding indicators, and was validated for a number of available field cases. It was found that, in order to accurately predict flooding hazards, water depth over the reef flat, incident wave conditions, and reef flat width are the most essential factors, whereas other factors such as beach slope and bed friction due to the presence or absence of corals are less important. BEWARE is a potentially powerful tool for use in early warning systems or risk assessment studies, and can be used to make projections about how wave-induced flooding on coral reef-lined coasts may change due to climate change.
A Bayesian-Based System to Assess Wave-Driven Flooding Hazards on Coral Reef-Lined Coasts
NASA Astrophysics Data System (ADS)
Pearson, S. G.; Storlazzi, C. D.; van Dongeren, A. R.; Tissier, M. F. S.; Reniers, A. J. H. M.
2017-12-01
Many low-elevation, coral reef-lined, tropical coasts are vulnerable to the effects of climate change, sea level rise, and wave-induced flooding. The considerable morphological diversity of these coasts and the variability of the hydrodynamic forcing that they are exposed to make predicting wave-induced flooding a challenge. A process-based wave-resolving hydrodynamic model (XBeach Non-Hydrostatic, "XBNH") was used to create a large synthetic database for use in a "Bayesian Estimator for Wave Attack in Reef Environments" (BEWARE), relating incident hydrodynamics and coral reef geomorphology to coastal flooding hazards on reef-lined coasts. Building on previous work, BEWARE improves system understanding of reef hydrodynamics by examining the intrinsic reef and extrinsic forcing factors controlling runup and flooding on reef-lined coasts. The Bayesian estimator has high predictive skill for the XBNH model outputs that are flooding indicators, and was validated for a number of available field cases. It was found that, in order to accurately predict flooding hazards, water depth over the reef flat, incident wave conditions, and reef flat width are the most essential factors, whereas other factors such as beach slope and bed friction due to the presence or absence of corals are less important. BEWARE is a potentially powerful tool for use in early warning systems or risk assessment studies, and can be used to make projections about how wave-induced flooding on coral reef-lined coasts may change due to climate change.
NASA Astrophysics Data System (ADS)
Kourafalou, V. H.; Androulidakis, Y. S.; Kang, H.; Smith, R. H.; Valle-Levinson, A.
2018-07-01
The Pulley Ridge and Dry Tortugas coral reefs are among the most pristine, but also fragile, marine ecosystems of the continental United States. Understanding connectivity processes between them and with surrounding shelf and deep areas is fundamental for their management. This study focuses on the physical processes related to the connectivity of these reefs. Unprecedented in situ time series were used at these specific reef locations, together with satellite observations and numerical simulations, to investigate the dynamics controlling local circulation on the Southwestern Florida Shelf (SWFS) under oceanic influence. The approach of the Loop Current and Florida Current (LC/FC) system to the SWFS slope can induce 0.5 to 1 m/s offshore flows impacting the Pulley Ridge and Dry Tortugas reefs. On the other hand, when the LC/FC system retreats from the slope, onshore flows can carry open-sea waters over the coral reefs. Local formation of cyclonic eddies is possible near the Dry Tortugas reefs in the LC approach case and passage of upstream LC Frontal Eddies is possible in the LC retreat case. Offshore currents ∼1 m/s over the SWFS slope were also found during periods of anticyclonic LC Eddy separation. A novel finding is the shedding and northward propagation of mesoscale anticyclonic eddies from the core of the LC along the West Florida Shelf. Eddy shedding may have a broader effect on the dynamics of the shelf around the study reef areas. Long periods of LC/FC domination over these coral reefs (reaching several weeks to months) are characterized by strong (∼1 m/s) along-shelf currents and continuous upwelling processes, which may weaken the slope stratification and bring colder, deeper waters over the shelf-break and toward the shallower shelf region.
Williamson, David H.; Ceccarelli, Daniela M.; Evans, Richard D.; Hill, Jos K.; Russ, Garry R.
2014-01-01
No-take marine reserves (NTMRs) are increasingly being established to conserve or restore biodiversity and to enhance the sustainability of fisheries. Although effectively designed and protected NTMR networks can yield conservation and fishery benefits, reserve effects often fail to manifest in systems where there are high levels of non-compliance by fishers (poaching). Obtaining reliable estimates of NTMR non-compliance can be expensive and logistically challenging, particularly in areas with limited or non-existent resources for conducting surveillance and enforcement. Here we assess the utility of density estimates and re-accumulation rates of derelict (lost and abandoned) fishing line as a proxy for fishing effort and NTMR non-compliance on fringing coral reefs in three island groups of the Great Barrier Reef Marine Park (GBRMP), Australia. Densities of derelict fishing line were consistently lower on reefs within old (>20 year) NTMRs than on non-NTMR reefs (significantly in the Palm and Whitsunday Islands), whereas line densities did not differ significantly between reefs in new NTMRs (5 years of protection) and non-NTMR reefs. A manipulative experiment in which derelict fishing lines were removed from a subset of the monitoring sites demonstrated that lines re-accumulated on NTMR reefs at approximately one third (32.4%) of the rate observed on non-NTMR reefs over a thirty-two month period. Although these inshore NTMRs have long been considered some of the best protected within the GBRMP, evidence presented here suggests that the level of non-compliance with NTMR regulations is higher than previously assumed. PMID:25545154
Evaluation of tire reefs for enhancing aquatic communities in concrete-lined canals
Mueller, Gordon; Liston, Charles R.
1994-01-01
Large earthen canals in the arid southwest are being lined with concrete to reduce seepage and conserve limited water supplies. Lining reduces habitat and increases operational velocities (relative to unaltered streams), which are detrimental to aquatic communities. Fish communities that become reestablished in these waterways exhibit lower species diversity, densities, and biomass than they did in the former earthen canals. Placement of low-profile tire reefs in the Coachella Canal, California, and the Hayden-Rhodes Aqueduct, Arizona, reversed these trends. Comparative sampling revealed that invertebrate and fish densities were 3 and 20 times higher, respectively, in reef areas than in typical canal sections without reefs. Tire reefs are recommended as an effective means of enhancing aquatic communities in concrete canals.
Coral mucus functions as an energy carrier and particle trap in the reef ecosystem.
Wild, Christian; Huettel, Markus; Klueter, Anke; Kremb, Stephan G; Rasheed, Mohammed Y M; Jørgensen, Bo B
2004-03-04
Zooxanthellae, endosymbiotic algae of reef-building corals, substantially contribute to the high gross primary production of coral reefs, but corals exude up to half of the carbon assimilated by their zooxanthellae as mucus. Here we show that released coral mucus efficiently traps organic matter from the water column and rapidly carries energy and nutrients to the reef lagoon sediment, which acts as a biocatalytic mineralizing filter. In the Great Barrier Reef, the dominant genus of hard corals, Acropora, exudes up to 4.8 litres of mucus per square metre of reef area per day. Between 56% and 80% of this mucus dissolves in the reef water, which is filtered through the lagoon sands. Here, coral mucus is degraded at a turnover rate of at least 7% per hour. Detached undissolved mucus traps suspended particles, increasing its initial organic carbon and nitrogen content by three orders of magnitude within 2 h. Tidal currents concentrate these mucus aggregates into the lagoon, where they rapidly settle. Coral mucus provides light energy harvested by the zooxanthellae and trapped particles to the heterotrophic reef community, thereby establishing a recycling loop that supports benthic life, while reducing loss of energy and nutrients from the reef ecosystem.
From artificial structures to self-sustaining oyster reefs
NASA Astrophysics Data System (ADS)
Walles, Brenda; Troost, Karin; van den Ende, Douwe; Nieuwhof, Sil; Smaal, Aad C.; Ysebaert, Tom
2016-02-01
Coastal ecosystems are increasingly recognized as essential elements within coastal defence schemes and coastal adaptation. The capacity of coastal ecosystems, like marshes and oyster reefs, to maintain their own habitat and grow with sea-level rise via biophysical feedbacks is seen as an important advantage of such systems compared to man-made hard engineering structures. Providing a suitable substrate for oysters to settle on offers a kick-start for establishment at places where they were lost or are desirable for coastal protection. Accumulation of shell material, through recruitment and growth, is essential to the maintenance of oyster reefs as it provides substrate for new generations (positive feedback loop), forming a self-sustainable structure. Insight in establishment, survival and growth thresholds and knowledge about the population dynamics are necessary to successfully implement oyster reefs in coastal defence schemes. The aim of this paper is to investigate whether artificial Pacific oyster reefs develop into self-sustaining oyster reefs that contribute to coastal protection. Reef development was investigated by studying recruitment, survival and growth rates of oysters on artificial oyster reefs in comparison with nearby natural Pacific oyster reefs. The artificial reef structure successfully offered substrate for settlement of oysters and therefore stimulated reef formation. Reef development, however, was hampered by local sedimentation and increasing tidal emersion. Tidal emersion is an important factor that can be used to predict where artificial oyster reefs have the potential to develop into self-sustaining reefs that could contribute to coastal protection, but it is also a limiting factor in using oyster reefs for coastal protection.
Global microbialization of coral reefs.
Haas, Andreas F; Fairoz, Mohamed F M; Kelly, Linda W; Nelson, Craig E; Dinsdale, Elizabeth A; Edwards, Robert A; Giles, Steve; Hatay, Mark; Hisakawa, Nao; Knowles, Ben; Lim, Yan Wei; Maughan, Heather; Pantos, Olga; Roach, Ty N F; Sanchez, Savannah E; Silveira, Cynthia B; Sandin, Stuart; Smith, Jennifer E; Rohwer, Forest
2016-04-25
Microbialization refers to the observed shift in ecosystem trophic structure towards higher microbial biomass and energy use. On coral reefs, the proximal causes of microbialization are overfishing and eutrophication, both of which facilitate enhanced growth of fleshy algae, conferring a competitive advantage over calcifying corals and coralline algae. The proposed mechanism for this competitive advantage is the DDAM positive feedback loop (dissolved organic carbon (DOC), disease, algae, microorganism), where DOC released by ungrazed fleshy algae supports copiotrophic, potentially pathogenic bacterial communities, ultimately harming corals and maintaining algal competitive dominance. Using an unprecedented data set of >400 samples from 60 coral reef sites, we show that the central DDAM predictions are consistent across three ocean basins. Reef algal cover is positively correlated with lower concentrations of DOC and higher microbial abundances. On turf and fleshy macroalgal-rich reefs, higher relative abundances of copiotrophic microbial taxa were identified. These microbial communities shift their metabolic potential for carbohydrate degradation from the more energy efficient Embden-Meyerhof-Parnas pathway on coral-dominated reefs to the less efficient Entner-Doudoroff and pentose phosphate pathways on algal-dominated reefs. This 'yield-to-power' switch by microorganism directly threatens reefs via increased hypoxia and greater CO2 release from the microbial respiration of DOC.
Baselines and Degradation of Coral Reefs in the Northern Line Islands
Sandin, Stuart A.; Smith, Jennifer E.; DeMartini, Edward E.; Dinsdale, Elizabeth A.; Donner, Simon D.; Friedlander, Alan M.; Konotchick, Talina; Malay, Machel; Maragos, James E.; Obura, David; Pantos, Olga; Paulay, Gustav; Richie, Morgan; Rohwer, Forest; Schroeder, Robert E.; Walsh, Sheila; Jackson, Jeremy B. C.; Knowlton, Nancy; Sala, Enric
2008-01-01
Effective conservation requires rigorous baselines of pristine conditions to assess the impacts of human activities and to evaluate the efficacy of management. Most coral reefs are moderately to severely degraded by local human activities such as fishing and pollution as well as global change, hence it is difficult to separate local from global effects. To this end, we surveyed coral reefs on uninhabited atolls in the northern Line Islands to provide a baseline of reef community structure, and on increasingly populated atolls to document changes associated with human activities. We found that top predators and reef-building organisms dominated unpopulated Kingman and Palmyra, while small planktivorous fishes and fleshy algae dominated the populated atolls of Tabuaeran and Kiritimati. Sharks and other top predators overwhelmed the fish assemblages on Kingman and Palmyra so that the biomass pyramid was inverted (top-heavy). In contrast, the biomass pyramid at Tabuaeran and Kiritimati exhibited the typical bottom-heavy pattern. Reefs without people exhibited less coral disease and greater coral recruitment relative to more inhabited reefs. Thus, protection from overfishing and pollution appears to increase the resilience of reef ecosystems to the effects of global warming. PMID:18301734
Development of A 2,000-10,000-Lb Improved Container Delivery System
2010-04-01
System. The fourth airdrop system within the program is the Skirt Reefed G-12. The Skirt Reefed G-12 is intended to be a HV airdrop system...UNCLASSIFIED 5 D. Skirt Reefed G-12 System The Skirt Reefed G-12 System utilizes the G-12 parachute packed in accordance with Humanitarian Airdrop...Procedures2 with a slight variation in the reefing line material used. After several tests and many failures, the 9/16- inch tubular nylon and 2 turns of
Ecological limitations to the resilience of coral reefs
NASA Astrophysics Data System (ADS)
Mora, Camilo; Graham, Nicholas A. J.; Nyström, Magnus
2016-12-01
The decline of coral reefs has been broadly attributed to human stressors being too strong and pervasive, whereas biological processes that may render coral reefs fragile have been sparsely considered. Here we review several ecological factors that can limit the ability of coral reefs to withstand disturbance. These include: (1) Many species lack the adaptive capacity to cope with the unprecedented disturbances they currently face; (2) human disturbances impact vulnerable life history stages, reducing reproductive output and the supply of recruits essential for recovery; (3) reefs can be vulnerable to the loss of few species, as niche specialization or temporal and spatial segregation makes each species unique (i.e., narrow ecological redundancy); in addition, many foundation species have similar sensitivity to disturbances, suggesting that entire functions can be lost to single disturbances; and (4) feedback loops and extinction vortices may stabilize degraded states or accelerate collapses even if stressors are removed. This review suggests that the degradation of coral reefs is due to not only the severity of human stressors but also the "fragility" of coral reefs. As such, appropriate governance is essential to manage stressors while being inclusive of ecological process and human uses across transnational scales. This is a considerable but necessary upgrade in current management if the integrity, and delivery of goods and services, of coral reefs is to be preserved.
Code of Federal Regulations, 2013 CFR
2013-10-01
...: Interior Office of the Secretary of the Interior KEY LARGO CORAL REEF PRESERVE § 15.1 Scope. The State of Florida has established a similar coral reef preserve on an area situated shoreward of a line three geographic miles from Key Largo and contiguous to the Key Largo Coral Reef Preserve. It is the policy of the...
Code of Federal Regulations, 2014 CFR
2014-10-01
...: Interior Office of the Secretary of the Interior KEY LARGO CORAL REEF PRESERVE § 15.1 Scope. The State of Florida has established a similar coral reef preserve on an area situated shoreward of a line three geographic miles from Key Largo and contiguous to the Key Largo Coral Reef Preserve. It is the policy of the...
Code of Federal Regulations, 2012 CFR
2012-10-01
...: Interior Office of the Secretary of the Interior KEY LARGO CORAL REEF PRESERVE § 15.1 Scope. The State of Florida has established a similar coral reef preserve on an area situated shoreward of a line three geographic miles from Key Largo and contiguous to the Key Largo Coral Reef Preserve. It is the policy of the...
Code of Federal Regulations, 2010 CFR
2010-10-01
...: Interior Office of the Secretary of the Interior KEY LARGO CORAL REEF PRESERVE § 15.1 Scope. The State of Florida has established a similar coral reef preserve on an area situated shoreward of a line three geographic miles from Key Largo and contiguous to the Key Largo Coral Reef Preserve. It is the policy of the...
Code of Federal Regulations, 2011 CFR
2011-10-01
...: Interior Office of the Secretary of the Interior KEY LARGO CORAL REEF PRESERVE § 15.1 Scope. The State of Florida has established a similar coral reef preserve on an area situated shoreward of a line three geographic miles from Key Largo and contiguous to the Key Largo Coral Reef Preserve. It is the policy of the...
The effectiveness of coral reefs for coastal hazard risk reduction and adaptation
Ferrario, Filippo; Beck, Michael W.; Storlazzi, Curt D.; Micheli, Fiorenza; Shepard, Christine C.; Airoldi, Laura
2014-01-01
The world’s coastal zones are experiencing rapid development and an increase in storms and flooding. These hazards put coastal communities at heightened risk, which may increase with habitat loss. Here we analyse globally the role and cost effectiveness of coral reefs in risk reduction. Meta-analyses reveal that coral reefs provide substantial protection against natural hazards by reducing wave energy by an average of 97%. Reef crests alone dissipate most of this energy (86%). There are 100 million or more people who may receive risk reduction benefits from reefs or bear hazard mitigation and adaptation costs if reefs are degraded. We show that coral reefs can provide comparable wave attenuation benefits to artificial defences such as breakwaters, and reef defences can be enhanced cost effectively. Reefs face growing threats yet there is opportunity to guide adaptation and hazard mitigation investments towards reef restoration to strengthen this first line of coastal defence. PMID:24825660
The effectiveness of coral reefs for coastal hazard risk reduction and adaptation.
Ferrario, Filippo; Beck, Michael W; Storlazzi, Curt D; Micheli, Fiorenza; Shepard, Christine C; Airoldi, Laura
2014-05-13
The world's coastal zones are experiencing rapid development and an increase in storms and flooding. These hazards put coastal communities at heightened risk, which may increase with habitat loss. Here we analyse globally the role and cost effectiveness of coral reefs in risk reduction. Meta-analyses reveal that coral reefs provide substantial protection against natural hazards by reducing wave energy by an average of 97%. Reef crests alone dissipate most of this energy (86%). There are 100 million or more people who may receive risk reduction benefits from reefs or bear hazard mitigation and adaptation costs if reefs are degraded. We show that coral reefs can provide comparable wave attenuation benefits to artificial defences such as breakwaters, and reef defences can be enhanced cost effectively. Reefs face growing threats yet there is opportunity to guide adaptation and hazard mitigation investments towards reef restoration to strengthen this first line of coastal defence.
The effectiveness of coral reefs for coastal hazard risk reduction and adaptation
Ferrario, Filippo; Beck, Michael W.; Storlazzi, Curt D.; Micheli, Fiorenza; Shepard, Christine C.; Airoldi, Laura
2014-01-01
The world’s coastal zones are experiencing rapid development and an increase in storms and flooding. These hazards put coastal communities at heightened risk, which may increase with habitat loss. Here we analyse globally the role and cost effectiveness of coral reefs in risk reduction. Meta-analyses reveal that coral reefs provide substantial protection against natural hazards by reducing wave energy by an average of 97%. Reef crests alone dissipate most of this energy (86%). There are 100 million or more people who may receive risk reduction benefits from reefs or bear hazard mitigation and adaptation costs if reefs are degraded. We show that coral reefs can provide comparable wave attenuation benefits to artificial defences such as breakwaters, and reef defences can be enhanced cost effectively. Reefs face growing threats yet there is opportunity to guide adaptation and hazard mitigation investments towards reef restoration to strengthen this first line of coastal defence.
Flow Encountering Abrupt Topography
2013-09-30
Colin at the Coral Reef Research Foundation and Paul Collins, who has extensive experience with such data). Helen Reef Concerted UCTD measurements...sensors, weights , 45 m of line, and a float) which were arrayed around Helen Reef nominally on the 90-m isobath using Revelle’s workboat. Colin (CRRF...the main islands of Palau and diverts around the south and north ends of the island group (Figure 1, left and right; Section ). At Helen Reef and Toby
Habitat degradation negatively affects auditory settlement behavior of coral reef fishes
Harding, Harry R.; Wong, Kathryn E.; Merchant, Nathan D.; Meekan, Mark G.; Radford, Andrew N.; Simpson, Stephen D.
2018-01-01
Coral reefs are increasingly degraded by climate-induced bleaching and storm damage. Reef recovery relies on recruitment of young fishes for the replenishment of functionally important taxa. Acoustic cues guide the orientation, habitat selection, and settlement of many fishes, but these processes may be impaired if degradation alters reef soundscapes. Here, we report spatiotemporally matched evidence of soundscapes altered by degradation from recordings taken before and after recent severe damage on Australia’s Great Barrier Reef. Postdegradation soundscapes were an average of 15 dB re 1 µPa quieter and had significantly reduced acoustic complexity, richness, and rates of invertebrate snaps compared with their predegradation equivalents. We then used these matched recordings in complementary light-trap and patch-reef experiments to assess responses of wild fish larvae under natural conditions. We show that postdegradation soundscapes were 8% less attractive to presettlement larvae and resulted in 40% less settlement of juvenile fishes than predegradation soundscapes; postdegradation soundscapes were no more attractive than open-ocean sound. However, our experimental design does not allow an estimate of how much attraction and settlement to isolated postdegradation soundscapes might change compared with isolated predegradation soundscapes. Reductions in attraction and settlement were qualitatively similar across and within all trophic guilds and taxonomic groups analyzed. These patterns may lead to declines in fish populations, exacerbating degradation. Acoustic changes might therefore trigger a feedback loop that could impair reef resilience. To understand fully the recovery potential of coral reefs, we must learn to listen. PMID:29712839
Jarrett, B.D.; Hine, A.C.; Halley, R.B.; Naar, D.F.; Locker, S.D.; Neumann, A.C.; Twichell, D.; Hu, C.; Donahue, B.T.; Jaap, W.C.; Palandro, D.; Ciembronowicz, K.
2005-01-01
The southeastern component of a subtle ridge feature extending over 200 km along the western ramped margin of the south Florida platform, known as Pulley Ridge, is composed largely of a non-reefal, coastal marine deposit. Modern biostromal reef growth caps southern Pulley Ridge (SPR), making it the deepest hermatypic reef known in American waters. Subsurface ridge strata are layered, lithified, and display a barrier island geomorphology. The deep-water reef community is dominated by platy scleractinian corals, leafy green algae, and coralline algae. Up to 60% live coral cover is observed in 60-75 m of water, although only 1-2% of surface light is available to the reef community. Vertical reef accumulation is thin and did not accompany initial ridge submergence during the most recent sea-level rise. The delayed onset of reef growth likely resulted from several factors influencing Gulf waters during early stages of the last deglaciation (???14 kyr B.P.) including; cold, low-salinity waters derived from discrete meltwater pulses, high-frequency sea-level fluctuations, and the absence of modern oceanic circulation patterns. Currently, reef growth is supported by the Loop Current, the prevailing western boundary current that impinges upon the southwest Florida platform, providing warm, clear, low-nutrient waters to SPR. The rare discovery of a preserved non-reefal lowstand shoreline capped by rich hermatypic deep-reef growth on a tectonically stable continental shelf is significant for both accurate identification of late Quaternary sea-level position and in better constraining controls on the depth limits of hermatypic reefs and their capacity for adaptation to extremely low light levels. ?? 2004 Elsevier B.V. All rights reserved.
50 CFR 622.2 - Definitions and acronyms.
Code of Federal Regulations, 2014 CFR
2014-10-01
... where coral growth abounds, including patch reefs, outer bank reefs, deep water banks, and hard bottoms... muscle tissue, of a spiny lobster along the top middorsal line (middle of the back) to the rearmost...
Onondage pinnacle reefs in New York State
DOE Office of Scientific and Technical Information (OSTI.GOV)
Friedman, G.M.
1995-09-01
Onondaga pinnacle reefs, part of the Onondaga Formation, developed in an epeiric setting of the lowermost Middle Devonian (Eifelian). The reefs were initiated as coral-crinoidal mounds in the Edgecliff Member of the formation. Whereas most Devonian reefs are composed of rugose corals. Coral is the predominant kind of fossil, followed by crinoids, brachiopods, mollusks, undifferentiated skeletal debris, and possible sponges. The initial mineralogy of the corals is inferred to have been calcite. The porosity of these reefs is almost unique among reef reservoirs. most reefs produce from secondary or diagenetic porosity; by contrast Onondaga reefs display primary intracoralline or frameworkmore » porosity. Between framework builders and/or skeletal particles cryptocrystalline/microcrystalline cement fills pores. As observed in modern reefs this kind of cement resembles micrite, but probable formed as high-magnesian calcite in a high-energy setting. Syntaxial or rim cement common lines crinoid particles. Some of these pinnacle reefs, formerly gas producers, are presently under development as gas-storage reservoirs.« less
Fishing down the largest coral reef fish species.
Fenner, Douglas
2014-07-15
Studies on remote, uninhabited, near-pristine reefs have revealed surprisingly large populations of large reef fish. Locations such as the northwestern Hawaiian Islands, northern Marianas Islands, Line Islands, U.S. remote Pacific Islands, Cocos-Keeling Atoll and Chagos archipelago have much higher reef fish biomass than islands and reefs near people. Much of the high biomass of most remote reef fish communities lies in the largest species, such as sharks, bumphead parrots, giant trevally, and humphead wrasse. Some, such as sharks and giant trevally, are apex predators, but others such as bumphead parrots and humphead wrasse, are not. At many locations, decreases in large reef fish species have been attributed to fishing. Fishing is well known to remove the largest fish first, and a quantitative measure of vulnerability to fishing indicates that large reef fish species are much more vulnerable to fishing than small fish. The removal of large reef fish by fishing parallels the extinction of terrestrial megafauna by early humans. However large reef fish have great value for various ecological roles and for reef tourism. Copyright © 2014 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Diedrich, A.
2007-12-01
Marine recreational tourism is one of a number of threats to the Belize Barrier Reef but, conversely, represents both a motivation and source of resources for its conservation. The growth of tourism in Belize has resulted in the fact that many coastal communities are in varying stages of a socio-economic shift from dependence on fishing to dependence on tourism. In a nation becoming increasingly dependent on the health of its coral reef ecosystems for economic prosperity, a shift from extractive uses to their preservation is both necessary and logical. Through examining local perception data in five coastal communities in Belize, each attracting different levels of coral reef related tourism, this analysis is intended to explore the relationship between tourism development and local coral reef conservation awareness and support. The results of the analysis show a positive correlation between tourism development and coral reef conservation awareness and support in the study communities. The results also show a positive correlation between tourism development and local perceptions of quality of life, a trend that is most likely the source of the observed relationship between tourism and conservation. The study concludes that, because the observed relationship may be dependent on continued benefits from tourism as opposed to a perceived crisis in coral reef health, Belize must pay close attention to tourism impacts in the future. Failure to do this could result in a destructive feedback loop that would contribute to the degradation of the reef and, ultimately, Belize’s diminished competitiveness in the ecotourism market.
Habitat degradation negatively affects auditory settlement behavior of coral reef fishes.
Gordon, Timothy A C; Harding, Harry R; Wong, Kathryn E; Merchant, Nathan D; Meekan, Mark G; McCormick, Mark I; Radford, Andrew N; Simpson, Stephen D
2018-05-15
Coral reefs are increasingly degraded by climate-induced bleaching and storm damage. Reef recovery relies on recruitment of young fishes for the replenishment of functionally important taxa. Acoustic cues guide the orientation, habitat selection, and settlement of many fishes, but these processes may be impaired if degradation alters reef soundscapes. Here, we report spatiotemporally matched evidence of soundscapes altered by degradation from recordings taken before and after recent severe damage on Australia's Great Barrier Reef. Postdegradation soundscapes were an average of 15 dB re 1 µPa quieter and had significantly reduced acoustic complexity, richness, and rates of invertebrate snaps compared with their predegradation equivalents. We then used these matched recordings in complementary light-trap and patch-reef experiments to assess responses of wild fish larvae under natural conditions. We show that postdegradation soundscapes were 8% less attractive to presettlement larvae and resulted in 40% less settlement of juvenile fishes than predegradation soundscapes; postdegradation soundscapes were no more attractive than open-ocean sound. However, our experimental design does not allow an estimate of how much attraction and settlement to isolated postdegradation soundscapes might change compared with isolated predegradation soundscapes. Reductions in attraction and settlement were qualitatively similar across and within all trophic guilds and taxonomic groups analyzed. These patterns may lead to declines in fish populations, exacerbating degradation. Acoustic changes might therefore trigger a feedback loop that could impair reef resilience. To understand fully the recovery potential of coral reefs, we must learn to listen. Copyright © 2018 the Author(s). Published by PNAS.
46 CFR 7.100 - Florida Reefs and Keys from Miami, FL to Marquesas Keys, FL.
Code of Federal Regulations, 2014 CFR
2014-10-01
... latitude 24°27.7′ N. longitude 81°48.1′ W. (Key West Entrance Lighted Whistle Buoy); thence to Cosgrove... 46 Shipping 1 2014-10-01 2014-10-01 false Florida Reefs and Keys from Miami, FL to Marquesas Keys... TO THE PUBLIC BOUNDARY LINES Atlantic Coast § 7.100 Florida Reefs and Keys from Miami, FL to...
46 CFR 7.100 - Florida Reefs and Keys from Miami, FL to Marquesas Keys, FL.
Code of Federal Regulations, 2012 CFR
2012-10-01
... latitude 24°27.7′ N. longitude 81°48.1′ W. (Key West Entrance Lighted Whistle Buoy); thence to Cosgrove... 46 Shipping 1 2012-10-01 2012-10-01 false Florida Reefs and Keys from Miami, FL to Marquesas Keys... TO THE PUBLIC BOUNDARY LINES Atlantic Coast § 7.100 Florida Reefs and Keys from Miami, FL to...
46 CFR 7.100 - Florida Reefs and Keys from Miami, FL to Marquesas Keys, FL.
Code of Federal Regulations, 2010 CFR
2010-10-01
... latitude 24°27.7′ N. longitude 81°48.1′ W. (Key West Entrance Lighted Whistle Buoy); thence to Cosgrove... 46 Shipping 1 2010-10-01 2010-10-01 false Florida Reefs and Keys from Miami, FL to Marquesas Keys... TO THE PUBLIC BOUNDARY LINES Atlantic Coast § 7.100 Florida Reefs and Keys from Miami, FL to...
46 CFR 7.100 - Florida Reefs and Keys from Miami, FL to Marquesas Keys, FL.
Code of Federal Regulations, 2011 CFR
2011-10-01
... latitude 24°27.7′ N. longitude 81°48.1′ W. (Key West Entrance Lighted Whistle Buoy); thence to Cosgrove... 46 Shipping 1 2011-10-01 2011-10-01 false Florida Reefs and Keys from Miami, FL to Marquesas Keys... TO THE PUBLIC BOUNDARY LINES Atlantic Coast § 7.100 Florida Reefs and Keys from Miami, FL to...
46 CFR 7.100 - Florida Reefs and Keys from Miami, FL to Marquesas Keys, FL.
Code of Federal Regulations, 2013 CFR
2013-10-01
... latitude 24°27.7′ N. longitude 81°48.1′ W. (Key West Entrance Lighted Whistle Buoy); thence to Cosgrove... 46 Shipping 1 2013-10-01 2013-10-01 false Florida Reefs and Keys from Miami, FL to Marquesas Keys... TO THE PUBLIC BOUNDARY LINES Atlantic Coast § 7.100 Florida Reefs and Keys from Miami, FL to...
Questions raised about benefits of artificial reefs
NASA Astrophysics Data System (ADS)
Showstack, Randy
Twenty-seven subway cars lined on a barge awaited their fate off the coast of Delaware, about 26 kilometers east of the Indian River Inlet, on August 22.A priest blessed the dark-red cars donated by the New York City Transit Authority, and prayed for the safety of all creatures using them. The song, “Sidewalks of New York” filled the festivities: “East side, west side, all around the town…” A woman tossed tokens from those subway lines into the sea. Then, down went the cars, having first been scrubbed clean, with windows removed for better circulation. Shoved by a bulldozer, the cars were deployed in 35 minutes to join a heap of military vehicles, old tires, and other used materials already accumulated at Reef Site 11, a 1.3-square-nautical-mile artificial reef.
Black reefs: iron-induced phase shifts on coral reefs.
Kelly, Linda Wegley; Barott, Katie L; Dinsdale, Elizabeth; Friedlander, Alan M; Nosrat, Bahador; Obura, David; Sala, Enric; Sandin, Stuart A; Smith, Jennifer E; Vermeij, Mark J A; Williams, Gareth J; Willner, Dana; Rohwer, Forest
2012-03-01
The Line Islands are calcium carbonate coral reef platforms located in iron-poor regions of the central Pacific. Natural terrestrial run-off of iron is non-existent and aerial deposition is extremely low. However, a number of ship groundings have occurred on these atolls. The reefs surrounding the shipwreck debris are characterized by high benthic cover of turf algae, macroalgae, cyanobacterial mats and corallimorphs, as well as particulate-laden, cloudy water. These sites also have very low coral and crustose coralline algal cover and are call black reefs because of the dark-colored benthic community and reduced clarity of the overlying water column. Here we use a combination of benthic surveys, chemistry, metagenomics and microcosms to investigate if and how shipwrecks initiate and maintain black reefs. Comparative surveys show that the live coral cover was reduced from 40 to 60% to <10% on black reefs on Millennium, Tabuaeran and Kingman. These three sites are relatively large (>0.75 km(2)). The phase shift occurs rapidly; the Kingman black reef formed within 3 years of the ship grounding. Iron concentrations in algae tissue from the Millennium black reef site were six times higher than in algae collected from reference sites. Metagenomic sequencing of the Millennium Atoll black reef-associated microbial community was enriched in iron-associated virulence genes and known pathogens. Microcosm experiments showed that corals were killed by black reef rubble through microbial activity. Together these results demonstrate that shipwrecks and their associated iron pose significant threats to coral reefs in iron-limited regions.
NASA Astrophysics Data System (ADS)
Suomalainen, Juha; Mucher, Sander; Kooistra, Lammert; Meesters, Erik
2014-05-01
The Dutch Caribbean island of Bonaire is one of the world's top diving holiday destinations much due to its clear waters and healthy coral reefs. The coral reefs surround the western side of the island as an approximately 50-150m wide band. However, the general consensus is that the extent and biodiversity of the Bonarian coral reef is constantly decreasing due to anthropogenic pressures. The last extensive study of the health of the reef ecosystem was performed in 1985 by Van Duyl creating an underwater atlas. In order to update this atlas of Bonaire's coral reefs, in October 2013, a hyperspectral mapping campaign was performed using the WUR Hyperspectral Mapping System (HYMSY). A dive validation campaign has been planned for early 2014. The HYMSY consists of a custom pushbroom spectrometer (range 450-950nm, FWHM 9nm, ~20 lines/s, 328 pixels/line), a consumer camera (collecting 16MPix raw image every 2 seconds), a GPS-Inertia Navigation System (GPS-INS), and synchronization and data storage units. The weight of the system at take-off is 2.0kg allowing it to be mounted on varying platforms. In Bonaire the system was flown on two platforms. (1) on a Cessna airplane to provide a coverage for whole west side of the island with a hyperspectral map in 2-4m resolution and a RGB orthomosaic in 15cm resolution, and (2) on a kite pulled by boat and car to provide a subset coverage in higher resolution. In this presentation we will present our mapping technique and first results including a preliminary underwater atlas and conclusions on reef development.
Coral reefs as the first line of defense: Shoreline protection in face of climate change.
Elliff, Carla I; Silva, Iracema R
2017-06-01
Coral reefs are responsible for a wide array of ecosystem services including shoreline protection. However, the processes involved in delivering this particular service have not been fully understood. The objective of the present review was to compile the main results in the literature regarding the study of shoreline protection delivered by coral reefs, identifying the main threats climate change imposes to the service, and discuss mitigation and recovery strategies that can and have been applied to these ecosystems. While different zones of a reef have been associated with different levels of wave energy and wave height attenuation, more information is still needed regarding the capacity of different reef morphologies to deliver shoreline protection. Moreover, the synergy between the main threats imposed by climate change to coral reefs has also not been thoroughly investigated. Recovery strategies are being tested and while there are numerous mitigation options, the challenge remains as to how to implement them and monitor their efficacy. Copyright © 2017 Elsevier Ltd. All rights reserved.
Black reefs: iron-induced phase shifts on coral reefs
Kelly, Linda Wegley; Barott, Katie L; Dinsdale, Elizabeth; Friedlander, Alan M; Nosrat, Bahador; Obura, David; Sala, Enric; Sandin, Stuart A; Smith, Jennifer E; Vermeij, Mark J A; Williams, Gareth J; Willner, Dana; Rohwer, Forest
2012-01-01
The Line Islands are calcium carbonate coral reef platforms located in iron-poor regions of the central Pacific. Natural terrestrial run-off of iron is non-existent and aerial deposition is extremely low. However, a number of ship groundings have occurred on these atolls. The reefs surrounding the shipwreck debris are characterized by high benthic cover of turf algae, macroalgae, cyanobacterial mats and corallimorphs, as well as particulate-laden, cloudy water. These sites also have very low coral and crustose coralline algal cover and are call black reefs because of the dark-colored benthic community and reduced clarity of the overlying water column. Here we use a combination of benthic surveys, chemistry, metagenomics and microcosms to investigate if and how shipwrecks initiate and maintain black reefs. Comparative surveys show that the live coral cover was reduced from 40 to 60% to <10% on black reefs on Millennium, Tabuaeran and Kingman. These three sites are relatively large (>0.75 km2). The phase shift occurs rapidly; the Kingman black reef formed within 3 years of the ship grounding. Iron concentrations in algae tissue from the Millennium black reef site were six times higher than in algae collected from reference sites. Metagenomic sequencing of the Millennium Atoll black reef-associated microbial community was enriched in iron-associated virulence genes and known pathogens. Microcosm experiments showed that corals were killed by black reef rubble through microbial activity. Together these results demonstrate that shipwrecks and their associated iron pose significant threats to coral reefs in iron-limited regions. PMID:21881615
Digital Reef Rugosity Estimates Coral Reef Habitat Complexity
Dustan, Phillip; Doherty, Orla; Pardede, Shinta
2013-01-01
Ecological habitats with greater structural complexity contain more species due to increased niche diversity. This is especially apparent on coral reefs where individual coral colonies aggregate to give a reef its morphology, species zonation, and three dimensionality. Structural complexity is classically measured with a reef rugosity index, which is the ratio of a straight line transect to the distance a flexible chain of equal length travels when draped over the reef substrate; yet, other techniques from visual categories to remote sensing have been used to characterize structural complexity at scales from microhabitats to reefscapes. Reef-scale methods either lack quantitative precision or are too time consuming to be routinely practical, while remotely sensed indices are mismatched to the finer scale morphology of coral colonies and reef habitats. In this communication a new digital technique, Digital Reef Rugosity (DRR) is described which utilizes a self-contained water level gauge enabling a diver to quickly and accurately characterize rugosity with non-invasive millimeter scale measurements of coral reef surface height at decimeter intervals along meter scale transects. The precise measurements require very little post-processing and are easily imported into a spreadsheet for statistical analyses and modeling. To assess its applicability we investigated the relationship between DRR and fish community structure at four coral reef sites on Menjangan Island off the northwest corner of Bali, Indonesia and one on mainland Bali to the west of Menjangan Island; our findings show a positive relationship between DRR and fish diversity. Since structural complexity drives key ecological processes on coral reefs, we consider that DRR may become a useful quantitative community-level descriptor to characterize reef complexity. PMID:23437380
Digital reef rugosity estimates coral reef habitat complexity.
Dustan, Phillip; Doherty, Orla; Pardede, Shinta
2013-01-01
Ecological habitats with greater structural complexity contain more species due to increased niche diversity. This is especially apparent on coral reefs where individual coral colonies aggregate to give a reef its morphology, species zonation, and three dimensionality. Structural complexity is classically measured with a reef rugosity index, which is the ratio of a straight line transect to the distance a flexible chain of equal length travels when draped over the reef substrate; yet, other techniques from visual categories to remote sensing have been used to characterize structural complexity at scales from microhabitats to reefscapes. Reef-scale methods either lack quantitative precision or are too time consuming to be routinely practical, while remotely sensed indices are mismatched to the finer scale morphology of coral colonies and reef habitats. In this communication a new digital technique, Digital Reef Rugosity (DRR) is described which utilizes a self-contained water level gauge enabling a diver to quickly and accurately characterize rugosity with non-invasive millimeter scale measurements of coral reef surface height at decimeter intervals along meter scale transects. The precise measurements require very little post-processing and are easily imported into a spreadsheet for statistical analyses and modeling. To assess its applicability we investigated the relationship between DRR and fish community structure at four coral reef sites on Menjangan Island off the northwest corner of Bali, Indonesia and one on mainland Bali to the west of Menjangan Island; our findings show a positive relationship between DRR and fish diversity. Since structural complexity drives key ecological processes on coral reefs, we consider that DRR may become a useful quantitative community-level descriptor to characterize reef complexity.
Structure and Dynamics of Cool Flare Loops Observed by the Interface Region Imaging Spectrograph
NASA Astrophysics Data System (ADS)
Mikuła, K.; Heinzel, P.; Liu, W.; Berlicki, A.
2017-08-01
Flare loops were well observed with the Interface Region Imaging Spectrograph (IRIS) during the gradual phase of two solar flares on 2014 March 29 and 2015 June 22. Cool flare loops are visible in various spectral lines formed at chromospheric and transition-region temperatures and exhibit large downflows which correspond to the standard scenario. The principal aim of this work is to analyze the structure and dynamics of cool flare loops observed in Mg II lines. Synthetic profiles of the Mg II h line are computed using the classical cloud model and assuming a uniform background intensity. In this paper, we study novel IRIS NUV observations of such loops in Mg II h and k lines and also show the behavior of hotter lines detected in the FUV channel. We obtained the spatial evolution of the velocities: near the loop top, the flow velocities are small and they are increasing toward the loop legs. Moreover, from slit-jaw image (SJI) movies, we observe some plasma upflows into the loops, which are also detectable in Mg II spectra. The brightness of the loops systematically decreases with increasing flow velocity, and we ascribe this to the effect of Doppler dimming, which works for Mg II lines. Emission profiles of Mg II were found to be extremely broad, and we explain this through the large unresolved non-thermal motions.
Structure and Dynamics of Cool Flare Loops Observed by the Interface Region Imaging Spectrograph
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mikuła, K.; Berlicki, A.; Heinzel, P.
Flare loops were well observed with the Interface Region Imaging Spectrograph ( IRIS ) during the gradual phase of two solar flares on 2014 March 29 and 2015 June 22. Cool flare loops are visible in various spectral lines formed at chromospheric and transition-region temperatures and exhibit large downflows which correspond to the standard scenario. The principal aim of this work is to analyze the structure and dynamics of cool flare loops observed in Mg ii lines. Synthetic profiles of the Mg ii h line are computed using the classical cloud model and assuming a uniform background intensity. In thismore » paper, we study novel IRIS NUV observations of such loops in Mg ii h and k lines and also show the behavior of hotter lines detected in the FUV channel. We obtained the spatial evolution of the velocities: near the loop top, the flow velocities are small and they are increasing toward the loop legs. Moreover, from slit-jaw image (SJI) movies, we observe some plasma upflows into the loops, which are also detectable in Mg ii spectra. The brightness of the loops systematically decreases with increasing flow velocity, and we ascribe this to the effect of Doppler dimming, which works for Mg ii lines. Emission profiles of Mg ii were found to be extremely broad, and we explain this through the large unresolved non-thermal motions.« less
NASA Astrophysics Data System (ADS)
Storlazzi, C. D.; Cheriton, O. M.; Messina, A. M.; Biggs, T. W.
2018-06-01
Water circulation over coral reefs can determine the degree to which reef organisms are exposed to the overlying waters, so understanding circulation is necessary to interpret spatial patterns in coral health. Because coral reefs often have high geomorphic complexity, circulation patterns and the duration of exposure, or "local residence time" of a water parcel, can vary substantially over small distances. Different meteorologic and oceanographic forcings can further alter residence time patterns over reefs. Here, spatially dense Lagrangian surface current drifters and Eulerian current meters were used to characterize circulation patterns and resulting residence times over different regions of the reefs in Faga'alu Bay, American Samoa, during three distinct forcing periods: calm, strong winds, and large waves. Residence times varied among different geomorphic zones of the reef and were reflected in the spatially varying health of the corals across the embayment. The relatively healthy, seaward fringing reef consistently had the shortest residence times, as it was continually flushed by wave breaking at the reef crest, whereas the degraded, sheltered, leeward fringing reef consistently had the longest residence times, suggesting this area is more exposed to land-based sources of pollution. Strong wind forcing resulted in the longest residence times by pinning the water in the bay, whereas large wave forcing flushed the bay and resulted in the shortest residence times. The effect of these different forcings on residence times was fairly consistent across all reef geomorphic zones, with the shift from wind to wave forcing shortening mean residence times by approximately 50%. Although ecologically significant to the coral organisms in the nearshore reef zones, these shortened residence times were still 2-3 times longer than those associated with the seaward fringing reef across all forcing conditions, demonstrating how the geomorphology of a reef environment sets a first-order control on reef health.
STS-32 Earth observation of the western Coral Sea and the Great Barrier Reef
NASA Technical Reports Server (NTRS)
1990-01-01
STS-32 Earth observation taken onboard Columbia, Orbiter Vehicle (OV) 102, is of the western Coral Sea and the Great Barrier Reef. The scene shows phytoplankton or algal bloom in the northwest Coral Sea. The western Coral Sea and the Great Barrier Reef waters offshore Queensland, Australia are the sites of some of the larger concentrations or 'blooms' of phytoplankton and algae in the open ocean. In the instance illustrated here, the leading edge of a probable concentration of algae or phytoplankton is seen as a light irregular line and sheen between the offshore Great Barrier Reef and the Queensland coast. Previous phytoplankton concentrations in this area have been reported by ships at sea as having formed floating mats as thick as two meters.
NASA Astrophysics Data System (ADS)
Locker, Stanley D.; Reed, John K.; Farrington, Stephanie; Harter, Stacey; Hine, Albert C.; Dunn, Shane
2016-08-01
Shelf-margin carbonate mounds in water depths of 116-135 m in the eastern Gulf of Mexico along the central west Florida shelf were investigated using swath bathymetry, side-scan sonar, sub-bottom imaging, rock dredging, and submersible dives. These enigmatic structures, known to fisherman as the "Sticky Grounds", trend along slope, are 5-15 m in relief with base diameters of 5-30 m, and suggest widespread potential for mesophotic reef habitat along the west Florida outer continental shelf. Possible origins are sea-level lowstand coral patch reefs, oyster reefs, or perhaps more recent post-lowstand biohermal development. Rock dredging recovered bioeroded carbonate-rock facies comprised of bored and cemented bioclastics. Rock sample components included calcified worm tubes, pelagic sediment, and oysters normally restricted to brackish nearshore areas. Several reef sites were surveyed at the Sticky Grounds during a cruise in August 2010 with the R/V Seward Johnson using the Johnson-Sea-Link II submersible to ground truth the swath-sonar maps and to quantify and characterize the benthic habitats, benthic macrofauna, fish populations, and coral/sponge cover. This study characterizes for the first time this mesophotic reef ecosystem and associated fish populations, and analyzes the interrelationships of the fish assemblages, benthic habitats and invertebrate biota. These highly eroded rock mounds provide extensive hard-bottom habitat for reef invertebrate species as well as essential fish habitat for reef fish and commercially/recreationally important fish species. The extent and significance of associated living resources with these bottom types is particularly important in light of the 2010 Deepwater Horizon oil spill in the northeastern Gulf and the proximity of the Loop Current. Mapping the distribution of these mesophotic-depth ecosystems is important for quantifying essential fish habitat and describing benthic resources. These activities can improve ecosystem management and planning of future oil and gas activities in this outer continental shelf region.
Locker, Stanley D.; Reed, John K.; Farrington, Stephanie; Harter, Stacey; Hine, Albert C.; Dunn, Shane
2016-01-01
Shelf-margin carbonate mounds in water depths of 116–135 m in the eastern Gulf of Mexico along the central west Florida shelf were investigated using swath bathymetry, side-scan sonar, sub-bottom imaging, rock dredging, and submersible dives. These enigmatic structures, known to fisherman as the “Sticky Grounds”, trend along slope, are 5–15 m in relief with base diameters of 5–30 m, and suggest widespread potential for mesophotic reef habitat along the west Florida outer continental shelf. Possible origins are sea-level lowstand coral patch reefs, oyster reefs, or perhaps more recent post-lowstand biohermal development. Rock dredging recovered bioeroded carbonate-rock facies comprised of bored and cemented bioclastics. Rock sample components included calcified worm tubes, pelagic sediment, and oysters normally restricted to brackish nearshore areas. Several reef sites were surveyed at the Sticky Grounds during a cruise in August 2010 with the R/V Seward Johnson using the Johnson-Sea-Link II submersible to ground truth the swath-sonar maps and to quantify and characterize the benthic habitats, benthic macrofauna, fish populations, and coral/sponge cover. This study characterizes for the first time this mesophotic reef ecosystem and associated fish populations, and analyzes the interrelationships of the fish assemblages, benthic habitats and invertebrate biota. These highly eroded rock mounds provide extensive hard-bottom habitat for reef invertebrate species as well as essential fish habitat for reef fish and commercially/recreationally important fish species. The extent and significance of associated living resources with these bottom types is particularly important in light of the 2010 Deepwater Horizon oil spill in the northeastern Gulf and the proximity of the Loop Current. Mapping the distribution of these mesophotic-depth ecosystems is important for quantifying essential fish habitat and describing benthic resources. These activities can improve ecosystem management and planning of future oil and gas activities in this outer continental shelf region.
Present status of grouper fisheries at waters of Kotania Bay, Western Seram District Maluku Province
NASA Astrophysics Data System (ADS)
Huliselan, N. V.; Wawo, M.; Tuapattinaja, M. A.; Sahetapy, D.
2017-10-01
Study on present status of groupers fishes at waters of Kotania Bay was conducted from 2016 to 2017. Survey and Participatory Rural Appraisal (PRA) method were used to collect and examine data and information concerning species potential and utilization of these species. The result shows that there are 35 species of grouper fishes inhabit Kotania Bay waters. From six genera recorded, Epinephelus found to have more varieties species richness compared to other five genera. In general, main habitat of adult grouper is coral reef, whilst mangrove and seagrass are habitat for nursery and grow out. The potency of the Epinephelus, Cephalopholis and Plectropomus genus tend to decrease started in 2000 up to 2017. At the same period, the production of these genera was also declined. Species potency and production declined was attributable to habitat (coral reef) degradation and high fishing intensity as a result of high market demand. Hand line, bottom long line and trap net are general fishing gear used in harvesting of theses fishes. Fishing activities took place all year round except for bottom long line which only lasted from June to October (East monsoon). Spatial fishing ground distribution is predominantly at coral reef ecosystem of Kotania Bay.
Fishing-gear restrictions and biomass gains for coral reef fishes in marine protected areas.
Campbell, Stuart J; Edgar, Graham J; Stuart-Smith, Rick D; Soler, German; Bates, Amanda E
2018-04-01
Considerable empirical evidence supports recovery of reef fish populations with fishery closures. In countries where full exclusion of people from fishing may be perceived as inequitable, fishing-gear restrictions on nonselective and destructive gears may offer socially relevant management alternatives to build recovery of fish biomass. Even so, few researchers have statistically compared the responses of tropical reef fisheries to alternative management strategies. We tested for the effects of fishery closures and fishing gear restrictions on tropical reef fish biomass at the community and family level. We conducted 1,396 underwater surveys at 617 unique sites across a spatial hierarchy within 22 global marine ecoregions that represented 5 realms. We compared total biomass across local fish assemblages and among 20 families of reef fishes inside marine protected areas (MPAs) with different fishing restrictions: no-take, hook-and-line fishing only, several fishing gears allowed, and sites open to all fishing gears. We included a further category representing remote sites, where fishing pressure is low. As expected, full fishery closures, (i.e., no-take zones) most benefited community- and family-level fish biomass in comparison with restrictions on fishing gears and openly fished sites. Although biomass responses to fishery closures were highly variable across families, some fishery targets (e.g., Carcharhinidae and Lutjanidae) responded positively to multiple restrictions on fishing gears (i.e., where gears other than hook and line were not permitted). Remoteness also positively affected the response of community-level fish biomass and many fish families. Our findings provide strong support for the role of fishing restrictions in building recovery of fish biomass and indicate important interactions among fishing-gear types that affect biomass of a diverse set of reef fish families. © 2017 Society for Conservation Biology.
Observation of a system of linear loops formed by re-growing hairs on rat skin.
Liu, Li-Yuan; Guo, Dong-Sheng; Xin, Xiu-Yu; Fang, Jin
2008-07-01
This paper details linear hair re-growth patterns observed in rats. Adult rats were shaved and observed. The first wave of hair re-growth did not distribute everywhere, but along specific craniocaudally-oriented lines. The hair-lines were 2-15 mm wide and ran from the head, through the torso to the limbs, and were symmetrical along the left and right sides of the body. The symmetric hair-lines from both sides of the body converged around the mouth, nose, and at the pubic region or ventral midline to form a system of hair-loop-lines (HLLs). The loops can be differentiated into four main patterns. The Dorsal Loop and the Lateral Dorsal Loop run along the dorsum and hindlimb. The Ventral Loop and Lateral Ventral Loop travel along the thorax, abdomen, and forelimb. These hair-lines coincide with our previously observed sympathetic-substance lines (SSLs) in the rat's skin. Histological observation indicates that rat hair follicles along the hair-lines were at anagen phase. The catecholamine histofluorescent check showed abundant sympathetic nerve fibers beneath the hair-lines. After the rats' hairs were dyed, and selected portions shaved, re-growth was only observed on the shaved portions, indicating that the linear hair growth closely correlated with the shaving. Lastly we examine the cause of the preferential re-growth and briefly discuss the purpose and physiological role of the HLL. (c) 2008 Wiley-Liss, Inc.
36 CFR 7.46 - Virgin Islands Coral Reef National Monument.
Code of Federal Regulations, 2014 CFR
2014-07-01
... Hurricane Hole and blue runner (hardnose) line fishing in the area south of St. John. The Superintendent... landfall of the hurricane to 48 hours following passage of the hurricane. (5) No lines or ropes shall be...
36 CFR 7.46 - Virgin Islands Coral Reef National Monument.
Code of Federal Regulations, 2013 CFR
2013-07-01
... Hurricane Hole and blue runner (hardnose) line fishing in the area south of St. John. The Superintendent... landfall of the hurricane to 48 hours following passage of the hurricane. (5) No lines or ropes shall be...
36 CFR 7.46 - Virgin Islands Coral Reef National Monument.
Code of Federal Regulations, 2012 CFR
2012-07-01
... Hurricane Hole and blue runner (hardnose) line fishing in the area south of St. John. The Superintendent... landfall of the hurricane to 48 hours following passage of the hurricane. (5) No lines or ropes shall be...
Evaluation and application of new AVIRIS data for the study of coral reefs in Hawaiian Islands
NASA Astrophysics Data System (ADS)
Wei, J.; Lee, Z.
2017-12-01
During the HyspIRI Hawaii campaign in early 2017, we collected hyperspectral remote sensing reflectance over coral reef environments in Kaneohe Bay in Oahu and the coastal waters of Maui Island. Based on in-situ measurements, we evaluated the data quality of reflectance measurements by the Airborne Visible-Infrared Imaging Spectrometer (AVIRIS). Further, these data were used to refine the remote sensing algorithms for identification of live corals, water bathymetry, and water clarity for the entire flight lines. Our results suggested great improvement in our understanding and capabilities of using HyspIRI-like data to observe and monitor coral reef environments.
Community Structure Of Coral Reefs In Saebus Island, Sumenep District, East Java
NASA Astrophysics Data System (ADS)
Rizmaadi, Mada; Riter, Johannes; Fatimah, Siti; Rifaldi, Riyan; Yoga, Arditho; Ramadhan, Fikri; Ambariyanto, Ambariyanto
2018-02-01
Increasing degradation coral reefs ecosystem has created many concerns. Reduction of this damage can only be done with good and proper management of coral reef ecosystem based on existing condition. The condition of coral reef ecosystem can be determined by assessing its community structure. This study investigates community structure of coral reef ecosystems around Saebus Island, Sumenep District, East Java, by using satellite imagery analysis and field observations. Satellite imagery analysis by Lyzenga methods was used to determine the observation stations and substrate distribution. Field observations were done by using Line Intercept Transect method at 4 stations, at the depth of 3 and 10 meters. The results showed that the percentage of coral reef coverage at the depth of 3 and 10 meters were 64.36% and 59.29%, respectively, and included in fine coverage category. This study found in total 25 genera from 13 families of corals at all stations. The most common species found were Acropora, Porites, and Pocillopora, while the least common species were Favites and Montastrea. Average value of Diversity, Uniformity and Dominancy indices were 2.94, 0.8 and 0.18 which include as medium, high, and low category, respectively. These results suggest that coral reef ecosystems around Saebus Island is in a good condition.
The percentage of coral reef cover in Saonek Kecil Island, Raja Ampat, West Papua
NASA Astrophysics Data System (ADS)
Wiguna, D. A.; Masithah, E. D.; Manan, A.
2018-04-01
Raja Ampat archipelago is located in the heart of the world’s coral triangle which is the center of the richest tropical marine biodiversity in the world. The Saonek Kecil Island has a location close to the Waisai Harbour (±2 km of sea routes). The Island that has no inhabitants and has a location close to harbour activities potentially damage coral reefs. This research was conducted by Line Intercept Transect (LIT) method that calculate the length of each colony form of growth (life form) of coral reefs on the line transect which stretched along the 50 metres parallel to the coastline at each station to obtain the percentage cover data, diversity index, uniformity index, and dominance index. The results of research precentage cover of coral reeef in the waters of Small Saonek Island reach 68.80% – 79.30% by category according to the decision of the Minister of State for the Environment number 4 of 2001 about the damage the reefs criteria included in the category of good – very good. As for the value of diversity index (H’) of 0.487 – 0.675 (medium-high), uniformity index (J) 0.437 – 0.606 (medium-high), and dominance index (C) 0.338 – 0.502 (medium-high).
THERMAL STRUCTURE OF CORONAL LOOPS AS SEEN WITH NORIKURA CORONAGRAPH
DOE Office of Scientific and Technical Information (OSTI.GOV)
Prasad, S. Krishna; Singh, Jagdev; Ichimoto, K., E-mail: krishna@iiap.res.in
2013-03-10
The thermal structure of a coronal loop, both along and across the loop, is vital in determining the exact plasma heating mechanism. High-resolution spectroscopic observations of the off-limb corona were made using the 25 cm Norikura coronagraph, located at Norikura, Japan. Observations on a number of days were made simultaneously in four forbidden iron emission lines, namely, the [Fe XI] 7892 A line, the [Fe XIII] 10747 A and 10798 A lines, and the [Fe XIV] 5303 A line and on some days made only in the [Fe XI] 7892 A and [Fe X] 6374 A lines. Using temperature sensitivemore » emission line ratios [Fe XIV] 5303 A/[Fe XIII] 10747 A and [Fe XI] 7892 A/[Fe X] 6374 A, we compute the electron temperatures along 18 different loop structures observed on different days. We find a significant negative temperature gradient in all of the structures observed in Fe XIV and Fe XIII and a positive temperature gradient in the structures observed in Fe XI and Fe X. Combining these results with the previous investigations by Singh and his collaborators, we infer that the loop tops, in general, appear hotter when observed in colder lines and colder when observed in relatively hotter lines as compared to their coronal foot points. We suggest that this contrasting trend observed in the temperature variation along the loop structures can be explained by a gradual interaction of different temperature plasma. The exact mechanism responsible for this interaction must be investigated further and has the potential to constrain loop heating models.« less
Monroe, Alison A; Ziegler, Maren; Roik, Anna; Röthig, Till; Hardenstine, Royale S; Emms, Madeleine A; Jensen, Thor; Voolstra, Christian R; Berumen, Michael L
2018-01-01
Coral bleaching continues to be one of the most devastating and immediate impacts of climate change on coral reef ecosystems worldwide. In 2015, a major bleaching event was declared as the "3rd global coral bleaching event" by the United States National Oceanic and Atmospheric Administration, impacting a large number of reefs in every major ocean. The Red Sea was no exception, and we present herein in situ observations of the status of coral reefs in the central Saudi Arabian Red Sea from September 2015, following extended periods of high temperatures reaching upwards of 32.5°C in our study area. We examined eleven reefs using line-intercept transects at three different depths, including all reefs that were surveyed during a previous bleaching event in 2010. Bleaching was most prevalent on inshore reefs (55.6% ± 14.6% of live coral cover exhibited bleaching) and on shallower transects (41% ± 10.2% of live corals surveyed at 5m depth) within reefs. Similar taxonomic groups (e.g., Agariciidae) were affected in 2015 and in 2010. Most interestingly, Acropora and Porites had similar bleaching rates (~30% each) and similar relative coral cover (~7% each) across all reefs in 2015. Coral genera with the highest levels of bleaching (>60%) were also among the rarest (<1% of coral cover) in 2015. While this bodes well for the relative retention of coral cover, it may ultimately lead to decreased species richness, often considered an important component of a healthy coral reef. The resultant long-term changes in these coral reef communities remain to be seen.
Ziegler, Maren; Roik, Anna; Röthig, Till; Hardenstine, Royale S.; Emms, Madeleine A.; Jensen, Thor; Voolstra, Christian R.; Berumen, Michael L.
2018-01-01
Coral bleaching continues to be one of the most devastating and immediate impacts of climate change on coral reef ecosystems worldwide. In 2015, a major bleaching event was declared as the “3rd global coral bleaching event” by the United States National Oceanic and Atmospheric Administration, impacting a large number of reefs in every major ocean. The Red Sea was no exception, and we present herein in situ observations of the status of coral reefs in the central Saudi Arabian Red Sea from September 2015, following extended periods of high temperatures reaching upwards of 32.5°C in our study area. We examined eleven reefs using line-intercept transects at three different depths, including all reefs that were surveyed during a previous bleaching event in 2010. Bleaching was most prevalent on inshore reefs (55.6% ± 14.6% of live coral cover exhibited bleaching) and on shallower transects (41% ± 10.2% of live corals surveyed at 5m depth) within reefs. Similar taxonomic groups (e.g., Agariciidae) were affected in 2015 and in 2010. Most interestingly, Acropora and Porites had similar bleaching rates (~30% each) and similar relative coral cover (~7% each) across all reefs in 2015. Coral genera with the highest levels of bleaching (>60%) were also among the rarest (<1% of coral cover) in 2015. While this bodes well for the relative retention of coral cover, it may ultimately lead to decreased species richness, often considered an important component of a healthy coral reef. The resultant long-term changes in these coral reef communities remain to be seen. PMID:29672556
NASA Astrophysics Data System (ADS)
Storlazzi, C. D.; Griffioen, D.; Cheriton, O. M.
2016-12-01
Coral reefs have been shown to significantly attenuate incident wave energy and thus provide protection for 100s of millions of people globally. To better constrain wave dynamics and wave-driven water levels over fringing coral reefs, a 4-month deployment of wave and tide gauges was conducted across two shore-normal transects on Roi-Namur Island and two transects on Kwajalein Island in the Republic of the Marshall Islands. At all locations, although incident wave (periods <25 s) heights were an order of magnitude greater than infragravity wave (periods > 250 s) heights on the outer reef flat just inshore of the zone of wave breaking, the infragravity wave heights generally equaled the incident wave heights by the middle of the reef flat and exceeded the incident wave heights on the inner reef flat by the shoreline. The infragravity waves generally were asymmetric, positively skewed, bore-like forms with incident-band waves riding the infragravity wave crest at the head of the bore; these wave packets have similar structure to high-frequency internal waves on an internal wave bore. Bore height was shown to scale with water depth, offshore wave height, and offshore wave period. For a given tidal elevation, with increasing offshore wave heights, such bores occurred more frequently on the middle reef flat, whereas they occurred less frequently on the inner reef flat. Skewed, asymmetric waves are known to drive large gradients in velocity and shear stress that can transport material onshore. Thus, a better understanding of these low-frequency, energetic bores on reef flats is critical to forecasting how coral reef-lined coasts may respond to sea-level rise and climate change.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Van Tyne, A.M.
1995-09-01
Seven subsurface Onondaga reefs have been found in southwestern New York (6) and northwestern Pennsylvania (1). These reefs have had a maximum thickness of about 200 feet and cover an area of a few hundred acres. They are similar to nearly 30 smaller reefs in the same geologic section which have previously been found along the Onodaga outcrop. The discovery well for Onodaga reef gas, although not recognized as such at the time, was the No. 1 Quinlan Oil. The well was drilled in 1933 in the Town of Olean, Cattaraugus County, New York near the New York-Pennsylvania State line.more » The first of the more recent Onondaga reef discoveries occurred in 1967 at Wyckoff in the Town of Jasper, Steuben County, New York. This discovery touched off a leasing and seismic exploration boom in this area of New York. As a result of these studies, two more reefs were discovered in 1971, two in 1974 and the last so far in 1981. These seven reefs have produced 7.1 billion cubic feet of gas. The smallest, Flatstone, has production to data of about 700 million cubic feet. The Onondaga reefs are of basal Onondaga, or Edgecliff, age. The Edgecliff is a light gray, coarsely crystalline, biostromal limestone. Onondaga reefs may have begun forming on somewhat higher parts of the sea floor in crinoid thickets. Because the Onondaga is considerably thicker in that area these so-called {open_quotes}reefs{close_quotes} are buried entirely within the total Onondaga section. They have been called reefs mainly because gas shows have been encountered in the lower Onondaga when it was drilled through by wells aiming for deeper Medina sandstones gas production. Nevertheless, gas production from them has been minimal. The seal consists of surrounding and overlapping black and gray middle Devonian Hamilton shales. The basal portions are surrounded by onlapping upper Onondaga limestones. The source of the gas is believed to be the highly organic Hamilton shale.« less
Hannak, Judith S.; Kompatscher, Sarah; Stachowitsch, Michael; Herler, Jürgen
2011-01-01
Shallow reefs (reef flats <1.5 m) in the northern Red Sea are impacted by growing tourism that includes swimmers, snorkellers and reef walkers but have largely been neglected in past studies. We selected a fringing reef along the lagoon of Dahab (Sinai, Egypt) as a model for a management strategy. Point-intercept line transects were used to determine substrate composition, coral community and condition, and the coral damage index (CDI) was applied. Approximately 84% of the coral colonies showed signs of damage such as breakage, partial mortality or algal overgrowth, especially affecting the most frequent coral genus Acropora. Questionnaires were used to determine the visitors’ socio-economic background and personal attitudes regarding snorkelling, SCUBA-diving and interest in visiting a prospective snorkelling trail. Experiencing nature (97%) was by far the strongest motivation, and interest in further education about reef ecology and skill training was high. Less experienced snorkellers and divers – the target group for further education and skill training – were those most prepared to financially support such a trail. We therefore recommend a guided underwater snorkelling trail and restricting recreational use to a less sensitive ‘ecotourism zone’ while protecting the shallow reef flat. Artificial structures can complete the trail and offer the opportunity to snorkel over deeper areas at unfavourable tide or wind conditions. This approach provides a strategy for the management and conservation of shallow-water reefs, which are facing increasing human impact here and elsewhere. PMID:21708420
Hannak, Judith S; Kompatscher, Sarah; Stachowitsch, Michael; Herler, Jürgen
2011-10-01
Shallow reefs (reef flats <1.5 m) in the northern Red Sea are impacted by growing tourism that includes swimmers, snorkellers and reef walkers but have largely been neglected in past studies. We selected a fringing reef along the lagoon of Dahab (Sinai, Egypt) as a model for a management strategy. Point-intercept line transects were used to determine substrate composition, coral community and condition, and the coral damage index (CDI) was applied. Approximately 84% of the coral colonies showed signs of damage such as breakage, partial mortality or algal overgrowth, especially affecting the most frequent coral genus Acropora. Questionnaires were used to determine the visitors' socio-economic background and personal attitudes regarding snorkelling, SCUBA-diving and interest in visiting a prospective snorkelling trail. Experiencing nature (97%) was by far the strongest motivation, and interest in further education about reef ecology and skill training was high. Less experienced snorkellers and divers--the target group for further education and skill training--were those most prepared to financially support such a trail. We therefore recommend a guided underwater snorkelling trail and restricting recreational use to a less sensitive 'ecotourism zone' while protecting the shallow reef flat. Artificial structures can complete the trail and offer the opportunity to snorkel over deeper areas at unfavourable tide or wind conditions. This approach provides a strategy for the management and conservation of shallow-water reefs, which are facing increasing human impact here and elsewhere. Copyright © 2011 Elsevier Ltd. All rights reserved.
Salcedo-Sanz, S; Del Ser, J; Landa-Torres, I; Gil-López, S; Portilla-Figueras, J A
2014-01-01
This paper presents a novel bioinspired algorithm to tackle complex optimization problems: the coral reefs optimization (CRO) algorithm. The CRO algorithm artificially simulates a coral reef, where different corals (namely, solutions to the optimization problem considered) grow and reproduce in coral colonies, fighting by choking out other corals for space in the reef. This fight for space, along with the specific characteristics of the corals' reproduction, produces a robust metaheuristic algorithm shown to be powerful for solving hard optimization problems. In this research the CRO algorithm is tested in several continuous and discrete benchmark problems, as well as in practical application scenarios (i.e., optimum mobile network deployment and off-shore wind farm design). The obtained results confirm the excellent performance of the proposed algorithm and open line of research for further application of the algorithm to real-world problems.
Salcedo-Sanz, S.; Del Ser, J.; Landa-Torres, I.; Gil-López, S.; Portilla-Figueras, J. A.
2014-01-01
This paper presents a novel bioinspired algorithm to tackle complex optimization problems: the coral reefs optimization (CRO) algorithm. The CRO algorithm artificially simulates a coral reef, where different corals (namely, solutions to the optimization problem considered) grow and reproduce in coral colonies, fighting by choking out other corals for space in the reef. This fight for space, along with the specific characteristics of the corals' reproduction, produces a robust metaheuristic algorithm shown to be powerful for solving hard optimization problems. In this research the CRO algorithm is tested in several continuous and discrete benchmark problems, as well as in practical application scenarios (i.e., optimum mobile network deployment and off-shore wind farm design). The obtained results confirm the excellent performance of the proposed algorithm and open line of research for further application of the algorithm to real-world problems. PMID:25147860
Plasma dynamics above solar flare soft x-ray loop tops
DOE Office of Scientific and Technical Information (OSTI.GOV)
Doschek, G. A.; Warren, H. P.; McKenzie, D. E.
2014-06-10
We measure non-thermal motions in flare loop tops and above the loop tops using profiles of highly ionized spectral lines of Fe XXIV and Fe XXIII formed at multimillion-degree temperatures. Non-thermal motions that may be due to turbulence or multiple flow regions along the line of sight are extracted from the line profiles. The non-thermal motions are measured for four flares seen at or close to the solar limb. The profile data are obtained using the Extreme-ultraviolet Imaging Spectrometer on the Hinode spacecraft. The multimillion-degree non-thermal motions are between 20 and 60 km s{sup –1} and appear to increase withmore » height above the loop tops. Motions determined from coronal lines (i.e., lines formed at about 1.5 MK) tend to be smaller. The multimillion-degree temperatures in the loop tops and above range from about 11 MK to 15 MK and also tend to increase with height above the bright X-ray-emitting loop tops. The non-thermal motions measured along the line of sight, as well as their apparent increase with height, are supported by Solar Dynamics Observatory Atmospheric Imaging Assembly measurements of turbulent velocities in the plane of the sky.« less
Triple loop heat exchanger for an absorption refrigeration system
Reimann, Robert C.
1984-01-01
A triple loop heat exchanger for an absorption refrigeration system is disclosed. The triple loop heat exchanger comprises portions of a strong solution line for conducting relatively hot, strong solution from a generator to a solution heat exchanger of the absorption refrigeration system, conduit means for conducting relatively cool, weak solution from the solution heat exchanger to the generator, and a bypass system for conducting strong solution from the generator around the strong solution line and around the solution heat exchanger to an absorber of the refrigeration system when strong solution builds up in the generator to an undesirable level. The strong solution line and the conduit means are in heat exchange relationship with each other in the triple loop heat exchanger so that, during normal operation of the refrigeration system, heat is exchanged between the relatively hot, strong solution flowing through the strong solution line and the relatively cool, weak solution flowing through the conduit means. Also, the strong solution line and the bypass system are in heat exchange relationship in the triple loop heat exchanger so that if the normal flow path of relatively hot, strong solution flowing from the generator to an absorber is blocked, then this relatively, hot strong solution which will then be flowing through the bypass system in the triple loop heat exchanger, is brought into heat exchange relationship with any strong solution which may have solidified in the strong solution line in the triple loop heat exchanger to thereby aid in desolidifying any such solidified strong solution.
NASA Astrophysics Data System (ADS)
do Nascimento Silva, Luzia Liniane; Gomes, Moab Praxedes; Vital, Helenice
2018-05-01
Submerged reefs, referred to as the Açu Reefs, have been newly observed on both sides of the Açu Incised Valley on the northeastern equatorial Brazilian outer shelf. This study aims to understand the roles of shelf physiography, its antecedent morphologies, and its inter reef sedimentation on the different development stages of the biogenic reef during last deglacial sea-level rise. The data sets consist of side-scan sonar imagery, one sparker seismic profile, 76 sediment samples, and underwater photography. Seven backscatter patterns (P1 to P7) were identified and associated with eleven sedimentary carbonate and siliciclastic facies. The inherited relief, the mouth of the paleo incised valley, and the interreef sediment distribution play major controls on the deglacial reef evolution. The reefs occur in a depth-limited 25-55 m water depth range and in a 6 km wide narrow zone of the outer shelf. The reefs crop out in a surface area over 100 km2 and occur as a series of NW-SE preferentially orientated ridges composed of three parallel ridge sets at 45, 35, and 25 m of water depth. The reefs form a series of individual, roughly linear ridges, tens of km in length, acting as barriers in addition to scattered reef mounds or knolls, averaging 4 m in height and grouped in small patches and aggregates. The reefs, currently limited at the transition between the photic and mesophotic zones, are thinly covered by red algae and scattered coral heads and sponges. Taking into account the established sea-level curves from the equatorial Brazilian northeastern shelf / Rochas Atoll and Barbados, the shelf physiography, and the shallow bedrock, the optimal conditions for reef development had to occur during a time interval (11-9 kyr BP) characterized by a slowdown of the outer shelf flooding, immediately following Meltwater Pulse-1B. This 2 kyr short interval provided unique conditions for remarkable reef backstepping into distinct parallel ridge sets. Furthermore, the Açu Reefs have trapped relict siliciclastic sediments within the three sets of reefs, west of the Açu Incised Valley and adjacent coasts. Lines evidence of easterly nearshore currents carried sediments from the old Açu Incised Valley and adjacent coasts. These incipiently drowned reefs influence the water circulation patterns of the modern shelf system, its carbonate sedimentation, and sediment transport. This study provides a new example of reef occurrence which might be more commonly observed on similar equatorial continental shelves.
NASA Astrophysics Data System (ADS)
Kramer, S.; Nelson, P.
2016-02-01
Wave energy converters (WECs) and tidal energy converters (TECs) are only beginning to be deployed along the U.S. West Coast and in Hawai'i, and a better understanding of their ecological effects on fish, particularly on special status fish is needed to facilitate project siting, design and environmental permitting. The structures of WECs and TECs placed on to the seabed, such as anchors and foundations, may function as artificial reefs that attract reef associated fishes, while the midwater and surface structures, such as mooring lines, buoys, and wave or tidal power devices, may function as fish aggregating devices (FADs). We evaluated these potential ecological interactions by comparing them to surrogate structures, such as artificial reefs, natural reefs, kelp vegetation, floating and sunken debris, oil and gas platforms, anchored FADs deployed to enhance fishing opportunities, net cages used for mariculture, and piers and marinas. We also conducted guided discussions with scientists and resource managers to provide unpublished observations. Our findings indicate the structures of WECs and TECs placed on or near the seabed in coastal waters of the U.S. West Coast and Hawai`i likely will function as small scale artificial reefs and attract potentially high densities of reef associated fishes and the midwater and surface structures of WECs placed in the tropical waters of Hawai`i likely will function as de facto FADs.
How models can support ecosystem-based management of coral reefs
NASA Astrophysics Data System (ADS)
Weijerman, Mariska; Fulton, Elizabeth A.; Janssen, Annette B. G.; Kuiper, Jan J.; Leemans, Rik; Robson, Barbara J.; van de Leemput, Ingrid A.; Mooij, Wolf M.
2015-11-01
Despite the importance of coral reef ecosystems to the social and economic welfare of coastal communities, the condition of these marine ecosystems have generally degraded over the past decades. With an increased knowledge of coral reef ecosystem processes and a rise in computer power, dynamic models are useful tools in assessing the synergistic effects of local and global stressors on ecosystem functions. We review representative approaches for dynamically modeling coral reef ecosystems and categorize them as minimal, intermediate and complex models. The categorization was based on the leading principle for model development and their level of realism and process detail. This review aims to improve the knowledge of concurrent approaches in coral reef ecosystem modeling and highlights the importance of choosing an appropriate approach based on the type of question(s) to be answered. We contend that minimal and intermediate models are generally valuable tools to assess the response of key states to main stressors and, hence, contribute to understanding ecological surprises. As has been shown in freshwater resources management, insight into these conceptual relations profoundly influences how natural resource managers perceive their systems and how they manage ecosystem recovery. We argue that adaptive resource management requires integrated thinking and decision support, which demands a diversity of modeling approaches. Integration can be achieved through complimentary use of models or through integrated models that systemically combine all relevant aspects in one model. Such whole-of-system models can be useful tools for quantitatively evaluating scenarios. These models allow an assessment of the interactive effects of multiple stressors on various, potentially conflicting, management objectives. All models simplify reality and, as such, have their weaknesses. While minimal models lack multidimensionality, system models are likely difficult to interpret as they require many efforts to decipher the numerous interactions and feedback loops. Given the breadth of questions to be tackled when dealing with coral reefs, the best practice approach uses multiple model types and thus benefits from the strength of different models types.
NASA Astrophysics Data System (ADS)
Khan, J. I.; Fletcher, L.; Nitta, N. V.
2006-07-01
We report what we believe are the first direct and unambiguous observations of simultaneous coronal magnetic flux loop shrinkage and expansion during the decay phase of a solar flare. The retracting and expanding loops were observed nearly face-on (i.e., with the loop major axis approximately orthogonal to the line of sight) in emission in imaging data from the Yohkoh Soft X-ray Telescope (SXT). The retracting loop is observed to shrink with a speed of 118 ± 66 km s-1. The faint outward moving loop-like feature occurred ~200´´ above the shrinking loop during the time of the shrinking loop. We estimate the speed of the outward moving loop was ~129 ± 74 km s-1. We interpret the shrinking loop and simultaneous outward moving loop as direct evidence for reconnected magnetic field lines during a flare.
NASA Astrophysics Data System (ADS)
Cheriton, O. M.; Storlazzi, C. D.; Rosenberger, K. J.
2016-02-01
Low-lying, reef-fringed islands are susceptible to sea-level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, wave gauges and a current meter were deployed for 5 months across two shore-normal transects on Roi-Namur, an atoll island in the Republic of the Marshall Islands. These observations captured two large wave events that had maximum wave heights greater than 6 m and peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly-skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, exceeded 3.7 m at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3-hr time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along atoll and fringing reef-lined shorelines, such as island overwash. These observations lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of both extreme shoreline runup and island overwash, threatening the sustainability of these islands.
NASA Astrophysics Data System (ADS)
Cheriton, Olivia M.; Storlazzi, Curt D.; Rosenberger, Kurt J.
2016-05-01
Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.
Cheriton, Olivia; Storlazzi, Curt; Rosenberger, Kurt
2016-01-01
Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04–0.004 Hz) and very low frequency (0.004–0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.
NASA Astrophysics Data System (ADS)
Krissinel, Boris
2018-03-01
The paper reports the results of calculations of the center-to-limb intensity of optically thin line emission in EUV and FUV wavelength ranges. The calculations employ a multicomponent model for the quiescent solar corona. The model includes a collection of loops of various sizes, spicules, and free (inter-loop) matter. Theoretical intensity values are found from probabilities of encountering parts of loops in the line of sight with respect to the probability of absence of other coronal components. The model uses 12 loops with sizes from 3200 to 210000 km with different values of rarefaction index and pressure at the loop base and apex. The temperature at loop apices is 1 400 000 K. The calculations utilize the CHIANTI database. The comparison between theoretical and observed emission intensity values for coronal and transition region lines obtained by the SUMER, CDS, and EIS telescopes shows quite satisfactory agreement between them, particularly for the solar disk center. For the data acquired above the limb, the enhanced discrepancies after the analysis refer to errors in EIS measurements.
NASA Astrophysics Data System (ADS)
Betta, R. M.; Peres, G.; Reale, F.; Serio, S.
2001-12-01
We revisit a well-studied solar flare whose X-ray emission originating from a simple loop structure was observed by most of the instruments on board SMM on November 12, 1980. The X-ray emission of this flare, as observed with the XRP, was successfully modeled previously. Here we include a detailed modeling of the transition region and we compare the hydrodynamic results with the UVSP observations in two EUV lines, measured in areas smaller than the XRP rasters, covering only some portions of the flaring loop (the top and the foot-points). The single loop hydrodynamic model, which fits well the evolution of coronal lines (those observed with the XRP and the Fe XXI 1354.1 Å line observed with the UVSP) fails to model the flux level and evolution of the O V 1371.3 Åline.
Dual-tracer method to estimate coral reef response to a plume of chemically modified seawater
NASA Astrophysics Data System (ADS)
Maclaren, J. K.; Caldeira, K.
2013-12-01
We present a new method, based on measurement of seawater samples, to estimate the response of a reef ecosystem to a plume of an additive (for example, a nutrient or other chemical). In the natural environment, where there may be natural variability in concentrations, it can be difficult to distinguish between changes in concentrations that would occur naturally and changes in concentrations that result from a chemical addition. Furthermore, in the unconfined natural environment, chemically modified water can mix with waters that have not been modified, making it difficult to distinguish between effects of dilution and effects of chemical fluxes or transformations. We present a dual-tracer method that extracts signals from observations that may be affected by both natural variability and dilution. In this dual-tracer method, a substance (in our example case, alkalinity) is added to the water in known proportion to a passive conservative tracer (in our example case, Rhodamine WT dye). The resulting plume of seawater is allowed to flow over the study site. Two transects are drawn across the plume at the front and back of the study site. If, in our example, alkalinity is plotted as a function of dye concentration for the front transect, the slope of the resulting mixing line is the ratio of alkalinity to dye in the added fluid. If a similar mixing line is measured and calculated for the back transect, the slope of this mixing line will indicate the amount of added alkalinity that remains in the water flowing out of the study site per unit of added dye. The ratio of the front and back slopes indicates the fraction of added alkalinity that was taken up by the reef. The method is demonstrated in an experiment performed on One Tree Reef (Queensland, Australia) aimed at showing that ocean acidification is already affecting coral reef growth. In an effort to chemically reverse some of the changes to seawater chemistry that have occurred over the past 200 years, we added sodium hydroxide to increase alkalinity in the plume and controlled for dilution with Rhodamine WT dye. Preliminary data will be presented and analyzed using the approach described above.
Geographic extent and variation of a coral reef trophic cascade.
McClanahan, T R; Muthiga, N A
2016-07-01
Trophic cascades caused by a reduction in predators of sea urchins have been reported in Indian Ocean and Caribbean coral reefs. Previous studies have been constrained by their site-specific nature and limited spatial replication, which has produced site and species-specific understanding that can potentially preclude larger community-organization nuances and generalizations. In this study, we aimed to evaluate the extent and variability of the cascade community in response to fishing across ~23° of latitude and longitude in coral reefs in the southwestern Indian Ocean. The taxonomic composition of predators of sea urchins, the sea urchin community itself, and potential effects of changing grazer abundance on the calcifying benthic organisms were studied in 171 unique coral reef sites. We found that geography and habitat were less important than the predator-prey relationships. There were seven sea urchin community clusters that aligned with a gradient of declining fishable biomass and the abundance of a key predator, the orange-lined triggerfish (Balistapus undulatus). The orange-lined triggerfish dominated where sea urchin numbers and diversity were low but the relative abundance of wrasses and emperors increased where sea urchin numbers were high. Two-thirds of the study sites had high sea urchin biomass (>2,300 kg/ha) and could be dominated by four different sea urchin species, Echinothrix diadema, Diadema savignyi, D. setosum, and Echinometra mathaei, depending on the community of sea urchin predators, geographic location, and water depth. One-third of the sites had low sea urchin biomass and diversity and were typified by high fish biomass, predators of sea urchins, and herbivore abundance, representing lightly fished communities with generally higher cover of calcifying algae. Calcifying algal cover was associated with low urchin abundance where as noncalcifying fleshy algal cover was not clearly associated with herbivore abundance. Fishing of the orange-lined triggerfish, an uncommon, slow-growing by-catch species with little monetary value drives the cascade and other predators appear unable to replace its ecological role in the presence of fishing. This suggests that restrictions on the catch of this species could increase the calcification service of coral reefs on a broad scale. © 2016 by the Ecological Society of America.
NASA Astrophysics Data System (ADS)
MacIntyre, I. G.; Glynn, P. W.; Toscano, M. A.
2007-12-01
Formerly attributed to human activity, the demise of a bank-barrier reef off southeastern Barbados known as Cobbler’s Reef is now thought to be largely the result of late Holocene, millennial-scale storm damage. Eleven surface samples of the reef crest coral Acropora palmata from nine sites along its 15-km length plot above the western Atlantic sea-level curve from 3,000 to 4,500 cal years ago (calibrated, calendar 14C years). These elevated clusters suggest that the reef complex suffered extensive storm damage during this period. The constant heavy wave action typical of this area and consequent low herbivory maintain conditions favoring algal growth, thereby limiting the reestablishment of post-storm reef framework. Site descriptions and detailed line surveys show a surface now composed mainly of reworked fragments of A. palmata covered with algal turf, macroalgae and crustose coralline algae. The reef contains no live A. palmata and only a few scattered coral colonies consisting primarily of Diploria spp . and Porites astreoides, along with the hydrocoral Millepora complanata. A few in situ framework dates plot at expected depths for normal coral growth below the sea-level curve during and after the period of intense storm activity. The most recent of these in situ samples are 320 and 400 cal years old. Corals of this late period likely succumbed to high turbidity associated with land clearance for sugarcane agriculture in the mid-1600s.
Donohue, M J; Boland, R C; Sramek, C M; Antonelis, G A
2001-12-01
Marine debris threatens Northwestern Hawaiian Islands' (NWHI) coral reef ecosystems. Debris, a contaminant, entangles and kills endangered Hawaiian monk seals (Monachus schauinslandi), coral, and other wildlife. We describe a novel multi-agency effort using divers to systematically survey and remove derelict fishing gear from two NWHI in 1999. 14 t of derelict fishing gear were removed and debris distribution, density, type and fouling level documented at Lisianski Island and Pearl and Hermes Atoll. Reef debris density ranged from 3.4 to 62.2 items/km2. Trawl netting was the most frequent debris type encountered (88%) and represented the greatest debris component recovered by weight (35%), followed by monofilament gillnet (34%), and maritime line (23%). Most debris recovered, 72%, had light or no fouling, suggesting debris may have short oceanic circulation histories. Our study demonstrates that derelict fishing gear poses a persistent threat to the coral reef ecosystems of the Hawaiian Archipelago.
Deployable radiator with flexible line loop
NASA Technical Reports Server (NTRS)
Keeler, Bryan V. (Inventor); Lehtinen, Arthur Mathias (Inventor); McGee, Billy W. (Inventor)
2003-01-01
Radiator assembly (10) for use on a spacecraft (12) is provided including at least one radiator panel assembly (26) repeatably movable between a panel stowed position (28) and a panel deployed position (36), at least two flexible lines (40) in fluid communication with the at least one radiator panel assembly (26) and repeatably movable between a stowage loop (42) and a flattened deployed loop (44).
Reguero, Borja G; Beck, Michael W; Agostini, Vera N; Kramer, Philip; Hancock, Boze
2018-03-15
Coastal communities in tropical environments are at increasing risk from both environmental degradation and climate change and require urgent local adaptation action. Evidences show coral reefs play a critical role in wave attenuation but relatively little direct connection has been drawn between these effects and impacts on shorelines. Reefs are rarely assessed for their coastal protection service and thus not managed for their infrastructure benefits, while widespread damage and degradation continues. This paper presents a systematic approach to assess the protective role of coral reefs and to examine solutions based on the reef's influence on wave propagation patterns. Portions of the shoreline of Grenville Bay, Grenada, have seen acute shoreline erosion and coastal flooding. This paper (i) analyzes the historical changes in the shoreline and the local marine, (ii) assess the role of coral reefs in shoreline positioning through a shoreline equilibrium model first applied to coral reef environments, and (iii) design and begin implementation of a reef-based solution to reduce erosion and flooding. Coastline changes in the bay over the past 6 decades are analyzed from bathymetry and benthic surveys, historical imagery, historical wave and sea level data and modeling of wave dynamics. The analysis shows that, at present, the healthy and well-developed coral reefs system in the southern bay keeps the shoreline in equilibrium and stable, whereas reef degradation in the northern bay is linked with severe coastal erosion. A comparison of wave energy modeling for past bathymetry indicates that degradation of the coral reefs better explains erosion than changes in climate and historical sea level rise. Using this knowledge on how reefs affect the hydrodynamics, a reef restoration solution is designed and studied to ameliorate the coastal erosion and flooding. A characteristic design provides a modular design that can meet specific engineering, ecological and implementation criteria. Four pilot units were implemented in 2015 and are currently being field-tested. This paper presents one of the few existing examples available to date of a reef restoration project designed and engineered to deliver risk reduction benefits. The case study shows how engineering and ecology can work together in community-based adaptation. Our findings are particularly important for Small Island States on the front lines of climate change, who have the most to gain from protecting and managing coral reefs as coastal infrastructure. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.
Lidz, Barbara H.; Reich, Christopher D.; Shinn, Eugene A.
2007-01-01
The fragile coral reefs of the Florida Keys form the largest living coral reef ecosystem in the continental United States. Lining the shallow outer shelf approximately 5 to 7 km seaward of the keys, the reefs have national aesthetic and resource value. As recently as the 1970s, the coral reefs were the heart of a vibrant ecosystem. Since then, the health of all ecosystem components has declined markedly due to a variety of environmental stressors . Corals are succumbing to bleaching and diseases. Species that are the building blocks of solid reef framework are increasingly being replaced by species that do not construct reef framework. Algal proliferation is increasing competition for space and hard surfaces needed by coral larvae for settlement. Decline of the coral reef ecosystem has significant negative implications for economic vitality of the region, ranging from viability of the tourism industry attracted by the aesthetics to commercial fisheries drawn by the resources. At risk of loss are biologic habitats and reef resources, including interconnected habitats for endangered species in shoreline mangroves, productive nearshore marine and wetland nurseries, and economic offshore fisheries. In 1997, the U.S. Geological Survey's Coastal and Marine Geology Program undertook a comprehensive 7-year-long mission to consolidate, synthesize, and map new (1997) and existing geologic and biologic information into a digitized regional database and one-volume reference source on the geologic history of the Florida Keys reef tract (this report). The project was conducted in cooperation with the National Oceanic and Atmospheric Administration's National Marine Sanctuary Program. The purpose was to examine the natural evolution and demise of several coral reef ecosystems over the past 325,000 years, with an eye toward gaining a better understanding of the cause of the reef decline observed today. Scientific data and datasets presented in this report are intended for use by others in ongoing efforts to delineate which components of reef decline in the Florida Keys may be natural and which may be a result of human activities. Beyond scientific baseline datasets, this report also incorporates environmental, social, and historical aspects of the Florida Keys, including the impact of exploratory oil wells on benthic habitats off Florida.
Oyster reef restoration supports increased nekton biomass and potential commercial fishery value
2015-01-01
Across the globe, discussions centered on the value of nature drive many conservation and restoration decisions. As a result, justification for management activities increasingly asks for two lines of evidence: (1) biological proof of augmented ecosystem function or service, and (2) monetary valuation of these services. For oyster reefs, which have seen significant global declines and increasing restoration work, the need to provide both biological and monetary evidence of reef services on a local-level has become more critical in a time of declining resources. Here, we quantified species biomass and potential commercial value of nekton collected from restored oyster (Crassostrea virginica) reefs in coastal Louisiana over a 3-year period, providing multiple snapshots of biomass support over time. Overall, and with little change over time, fish and invertebrate biomass is 212% greater at restored oyster reefs than mud-bottom, or 0.12 kg m−2. The additional biomass of commercial species is equivalent to an increase of local fisheries value by 226%, or $0.09 m−2. Understanding the ecosystem value of restoration projects, and how they interact with regional management priorities, is critical to inform local decision-making and provide testable predictions. Quantitative estimates of potential commercial fisheries enhancement by oyster reef restoration such as this one can be used directly by local managers to determine the expected return on investment. PMID:26336635
Oyster reef restoration supports increased nekton biomass and potential commercial fishery value
Humphries, Austin T.; LaPeyre, Megan K.
2015-01-01
Across the globe, discussions centered on the value of nature drive many conservation and restoration decisions. As a result, justification for management activities increasingly asks for two lines of evidence: (1) biological proof of augmented ecosystem function or service, and (2) monetary valuation of these services. For oyster reefs, which have seen significant global declines and increasing restoration work, the need to provide both biological and monetary evidence of reef services on a local-level has become more critical in a time of declining resources. Here, we quantified species biomass and potential commercial value of nekton collected from restored oyster (Crassostrea virginica) reefs in coastal Louisiana over a 3-year period, providing multiple snapshots of biomass support over time. Overall, and with little change over time, fish and invertebrate biomass is 212% greater at restored oyster reefs than mud-bottom, or 0.12 kg m−2. The additional biomass of commercial species is equivalent to an increase of local fisheries value by 226%, or $0.09 m−2. Understanding the ecosystem value of restoration projects, and how they interact with regional management priorities, is critical to inform local decision-making and provide testable predictions. Quantitative estimates of potential commercial fisheries enhancement by oyster reef restoration such as this one can be used directly by local managers to determine the expected return on investment.
NASA Astrophysics Data System (ADS)
Streich, M.; Wetz, J. J.; Ajemian, M. J.; Stunz, G. W.
2016-02-01
The goal of our study was to evaluate the relative abundance, size and age structure of Red Snapper among three different habitat types (standing oil and gas platforms, artificial reefs [rigs-to-reefs], and natural banks) in the northwestern Gulf of Mexico. From May 2013 - January 2015, we conducted 140 vertical line sets and captured 1538 Red Snapper ranging in size from 251 to 855 mm TL. Ages determined for 801 of these fish ranged from 2-30 years. No differences were detected in Red Snapper CPUE among the three habitats. However, a comparison of TL and TW distributions suggested that natural banks supported a greater proportion of larger fish than artificial reefs or standing platforms (K-S test, p<0.001). Mean TW-at-age regressions for the most common age groups (ages 3-7) suggested that Red Snapper grew faster at artificial reefs and standing platforms than natural bank habitats (ANCOVA, p<0.05). Mean age was positively correlated with capture depth (r=0.79) suggesting spatial variation in age composition. These results have important implications for artificial reef development and Red Snapper management in the GOM. Further use of standardized, fishery-independent surveys and additional biological data will help elucidate the role artificial structures play in maintaining the Red Snapper population.
Dermatoglyphs in carriers of a balanced 15;21 translocation.
Rodewald, A; Zankl, M; Zankl, H; Zang, K D
1980-08-01
Cytogenetic and dermatoglyphic features were studied in a large family with an inherited 15;21 translocation. Of 35 healthy members of the family, 21 carried the translocation chromosome and 14 were chromosomally normal. There were six members with Down's syndrome who had the translocation. Dermatoglyphic studies showed that carriers of this balanced translocation had the following peculiarities significantly more often than the general population. On the hands, they had ulnar loops on the fingertips, symmetrical high terminations of the A line, symmetrical ulnar loops on the hypothenar areas, distal loops in the 3rd interdigital areas, open fields in the 4th interdigital areas, axial triradii in the distal position, and single transverse palmar creases (Sydney lines). On the feet, they had small distal loops on the hallucal area and distal loops in the 4th interdigital areas. The translocation carriers also had significantly more often than non-carrier relatives symmetrical high terminations of the A line, open fields in the 4th interdigital areas, distal axial triradii, and Sydney lines. On the feet, they had small distal loops on the hallucal areas, distal loops in the 4th interdigital areas, and tibial loops on the proximal hypothenar areas. The data obtained from this study, and especially the values of the Walker and general indices, indicate that some of the dermatoglyphic stigmata of Down's syndrome are directly associated with the 15;21 translocation carrier state and can therefore be used for predicting that state.
Using multiple lines of evidence to assess the risk of ecosystem collapse
Regan, Tracey J.; Dinh, Minh Ngoc; Ferrari, Renata; Keith, David A.; Lester, Rebecca; Mouillot, David; Murray, Nicholas J.; Nguyen, Hoang Anh; Nicholson, Emily
2017-01-01
Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment. PMID:28931744
Using multiple lines of evidence to assess the risk of ecosystem collapse.
Bland, Lucie M; Regan, Tracey J; Dinh, Minh Ngoc; Ferrari, Renata; Keith, David A; Lester, Rebecca; Mouillot, David; Murray, Nicholas J; Nguyen, Hoang Anh; Nicholson, Emily
2017-09-27
Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment. © 2017 The Authors.
Belcaro, G; Cesarone, M R; Ledda, A; Cornelli, U; Dugall, M; Di Renzo, A; Hosoi, M; Stuard, S; Vinciguerra, G; Pellegrini, L; Gizzi, G
2008-10-01
Fingerprints (FP), characteristic of humans, are impressions due to skin marks (ridges) on fingertips. Ridges are present on fingers/hands forming curved lines of different sizes/patterns. The point where a line stops or splits is defined typica' (their number/amount constitute identification patterns). FP are permanent and unique. This study compared FP patterns with cardiovascular risk factors: 7 main types of FP were used: 1. Arch: lines form waves from one site to the other side. 2. Tentarch: like arches but with a rising stick in the middle. 3. Loop: lines coming from one site returning in the middle to the same site. 4. Double loop: like loops but with two loops inside: one standing, one hanging. 5. Pocked loop: like the loop but with a small circle in the turning point. 6. Whorl: lines make circles. 7. Mixed figure: composed of different figures. There are two kinds of real typica: A. Ending line; B. Splitting lines (bifurcations). Several combinations may result. Ultrasound evaluation of carotid/femoral arteries in asymptomatic subjects. Arteries were evaluated with high-resolution ultrasound at the bifurcations. Four classes were defined: 1: normal intima-media (IMT) complex; 2: IMT thickening; 3: non-stenosing plaques (<50% stenosis); 4: stenosing plaque (>50%). Subjects in classes 1, 2, 3 were included into the analysis made comparing FP patterns and ultrasound. For each FP pattern: A. the main proportion of subjects with cardiovacular risk factors (91%) had arches (41.2%) and loops (either single, 38.2% or double 11.7% for a total of 49.9%). B. The remaining classes were statistically less important. C. The number of ridges per square mm was comparable in all pattern classes. D. The analysis of typica and other ridges characteristics requires a more elaborated system. Future research must define simple, low cost screening methods for preselection of subjects at higher cardiovascular risk or for exclusion of low risk subjects. The evaluation of fingerprint pattern may be useful to define risk groups.
Gardner, James V.; Mayer, Larry A.; Hughes-Clarke, John E.; Dartnell, Peter; Sulak, Kenneth J.
2001-01-01
A zone of deep-water reefs is thought to extend from the mid and outer shelf south of Mississippi and Alabama to at least the northwestern Florida shelf off Panama City, Florida (Figure 1, 67kb). The reefs off Mississippi and Alabama are found in water depths of 60 to 120 m (Ludwick and Walton, 1957; Gardner et al., in press) and were the focus of a multibeam echosounder (MBES) mapping survey by the U.S. Geological Survey (USGS) in 2000 (Gardner et al., 2000; in press). If this deep-water-reef trend does exist along the northwestern Florida shelf, then it is critical to determine the accurate geomorphology and type of the reefs that occur because of their importance as benthic habitats for fisheries. Precisely georeferenced high-resolution mapping of bathymetry is a fundamental first step in the study of areas suspected to be critical habitats. Morphology is thought to be critical to defining the distribution of dominant demersal plankton/planktivores communities. Fish faunas of shallow hermatypic reefs have been well studied, but those of deep ahermatypic reefs have been relatively ignored. The ecology of deep-water ahermatypic reefs is fundamentally different from hermatypic reefs because autochthonous intracellular symbiotic zooxanthellae (the carbon source for hermatypic corals) do not form the base of the trophic web in ahermatypic reefs. Instead, exogenous plankton, transported to the reef by currents, serves as the primary carbon source. Thus, one of the principle uses of the morphology data will be to identify whether any reefs found are hermatypic or ahermatypic in origin. Community structure and trophodynamics of demersal fishes of the outer continental of the northeastern Gulf of Mexico presently are the focus of a major USGS reseach project. A goal of the project is to answer questions concerning the relative roles played by morphology and surficial geology in controling biological differentiation. Deep-water reefs are important because they are fish havens, key spawning sites, and are critical early larval and juvenile habitats for economically important sport/food fishes. It is known that deep-water reefs function as a key source for re-population (via seasonal and ontogenetic migration) of heavily impacted inshore reefs. The deep-water reefs south of Mississippi and Alabama support a lush fauna of ahermatypic hard corals, soft corals, black corals, sessile crinoids and sponges, that together form a living habitat for a well-developed fish fauna. The fish fauna comprises typical Caribbean reef fishes and Carolinian shelf fishes, plus epipelagic fishes, and a few deep-sea fishes. The base of the megafaunal invertebrate food web is plankton, borne by essentially continuous semi-laminar currents generated by eddies, spawned off the Loop Current, that periodically travel across the shelf edge. A few, sidescan-sonar surveys have been made of areas locally identified as Destin Pinnacles, Steamboat Lumps Marine Reserve (Koenig et al., 2000; Scanlon, et al., 2000; 2001), Twin Ridges (Briere, et al., 2000; Scanlon, et al., 2000), and Madison-Swanson Marine Reserve (Koenig et al., 2000; Scanlon, et al., 2000; 2001). However, no quantitative and little qualitative information about the geomorphology and surficial geology can be gained from these data. Existing bathymetry along the northwestern Florida shelf suggests the existence of areas of possible isolated deep-water reefs. NOAA bathymetric maps NOS NH16-9 and NG16-12 show geomorphic expressions that hint of the presence of reefs in isolated areas rather than in a continuous zone. There has been no systematic, high-resolution bathymetry collected in this area, prior to this cruise. After the successful mapping of the deep-water reefs on the Mississippi and Alabama shelf (Gardner et al., 2000; in press), a partnership composed of the USGS, Minerals Management Service, and NOAA was formed to continue the deep-reef mapping to the northwest Florida mid shelf and upper slope. This cruise is the first fruit of that partnership.
Spectroscopic Study of a Dark Lane and a Cool Loop in a Solar Limb Active Region by Hinode/EIS
NASA Astrophysics Data System (ADS)
Lee, K.; Imada, S.; Moon, Y.; Lee, J.
2012-12-01
We investigate a cool loop and a dark lane over a limb active region on 2007 March 14 by the Hinode/EUV Imaging Spectrometer (EIS). The cool loop is clearly seen in the EIS spectral lines formed at the transition region temperature (log T = 5.8). The dark lane is characterized by an elongated faint structure in coronal spectral lines (log T = 5.8 - 6.1) and rooted on a bright point. We examine their electron densities, Doppler velocities, and non-thermal velocities as a function of distance from the limb using the spectral lines formed at different temperatures (log T = 5.4 - 6.4). The electron densities of the cool loop and the dark lane are derived from the density sensitive line pairs of Mg VII, Fe XII, and Fe XIV spectra. Under the hydrostatic equilibrium and isothermal assumption, we determine their temperatures from the density scale height. Comparing the scale height temperatures to the peak formation temperatures of the spectral lines, we note that the scale height temperature of the cool loop is consistent with a peak formation temperature of the Mg VII (log T = 5.8) and the scale height temperature of the dark lane is close to a peak formation temperature of the Fe XII and Fe XIII (log T = 6.1 - 6.2). It is interesting to note that the structures of the cool loop and the dark lane are most visible in these temperature lines. While the non-thermal velocity in the cool loop slightly decreases (less than 7 km {s-1}) along the loop, that in the dark lane sharply falls off with height. The variation of non-thermal velocity with height in the cool loop and the dark lane is contrast to that in off-limb polar coronal holes which are considered as source of the fast solar wind. Such a decrease in the non-thermal velocity may be explained by wave damping near the solar surface or turbulence due to magnetic reconnection near the bright point.
Evidence for two-loop interaction from IRIS and SDO observations of penumbral brightenings
NASA Astrophysics Data System (ADS)
Alissandrakis, C. E.; Koukras, A.; Patsourakos, S.; Nindos, A.
2017-07-01
Aims: We investigate small scale energy release events which can provide clues on the heating mechanism of the solar corona. Methods: We analyzed spectral and imaging data from the Interface Region Imaging Spectrograph (IRIS), images from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatoty (SDO), and magnetograms from the Helioseismic and Magnetic Imager (HMI) aboard SDO. Results: We report observations of small flaring loops in the penumbra of a large sunspot on July 19, 2013. Our main event consisted of a loop spanning 15'', from the umbral-penumbral boundary to an opposite polarity region outside the penumbra. It lasted approximately 10 min with a two minute impulsive peak and was observed in all AIA/SDO channels, while the IRIS slit was located near its penumbral footpoint. Mass motions with an apparent velocity of 100 km s-1 were detected beyond the brightening, starting in the rise phase of the impulsive peak; these were apparently associated with a higher-lying loop. We interpret these motions in terms of two-loop interaction. IRIS spectra in both the C II and Si iv lines showed very extended wings, up to about 400 km s-1, first in the blue (upflows) and subsequently in the red wing. In addition to the strong lines, emission was detected in the weak lines of Cl I, O I and C I, as well as in the Mg II triplet lines. Absorption features in the profiles of the C II doublet, the Si iv doublet and the Mg II h and k lines indicate the existence of material with a lower source function between the brightening and the observer. We attribute this absorption to the higher loop and this adds further credibility to the two-loop interaction hypothesis. Tilts were detected in the absorption spectra, as well as in the spectra of Cl I, O I, and C I lines, possibly indicating rotational motions from the untwisting of magnetic flux tubes. Conclusions: We conclude that the absorption features in the C II, Si iv and Mg II profiles originate in a higher-lying, descending loop; as this approached the already activated lower-lying loop, their interaction gave rise to the impulsive peak, the very broad line profiles and the mass motions. Movies associated to Figs. A.1-A.3 are available at http://www.aanda.org
Jordán-Dahlgren, Eric; Maldonado, Miguel Angel; Rodríguez-Martínez, Rosa Elisa
2005-01-25
We documented the prevalence of diseases, syndromes and partial mortality in colonies of the Montastraea annularis species complex on 3 reefs, and tested the assumption that a higher prevalence of these parameters occurs when reefs are closer to point-sources of pollution. One reef was isolated from the impact of local factors with the exception of fishing, 1 potentially influenced by local industrial pollutants, and 1 influenced by local urban pollution. Two reefs were surveyed in 1996 and again in 2001 and 1 in 1998 and again in 2001. In 2001, colonies on all reefs had a high prevalence of the yellow-band syndrome and a relatively high degree of recent partial mortality, while the prevalence of black-band and white-plague diseases was low although a new sign, that we named the thin dark line, had relatively high prevalence in all reefs. As no direct relationship was found between disease prevalence and local environmental quality, our results open the possibility that regional and/or global factors may already be playing an important role in the prevalence of coral disease in the Caribbean, and contradict the theory that coral disease prevalence is primarily related to local environmental degradation. Reasons that may partially explain these findings are the high level of potential pathogen connectivity within the Caribbean as a result of its circulation patterns coupled to the large land-derived pollutants and pathogens input into this Mediterranean sea, together with the surface water warming effects which stress corals and enhance pathogen activity.
Work, Thierry M.; Aeby, G.S.; Maragos, J.E.
2008-01-01
Coral reefs can undergo relatively rapid changes in the dominant biota, a phenomenon referred to as phase shift. Various reasons have been proposed to explain this phenomenon including increased human disturbance, pollution, or changes in coral reef biota that serve a major ecological function such as depletion of grazers. However, pinpointing the actual factors potentially responsible can be problematic. Here we show a phase shift from coral to the corallimorpharian Rhodactis howesii associated with a long line vessel that wrecked in 1991 on an isolated atoll (Palmyra) in the central Pacific Ocean. We documented high densities of R. howesii near the ship that progressively decreased with distance from the ship whereas R. howesii were rare to absent in other parts of the atoll. We also confirmed high densities of R. howesii around several buoys recently installed on the atoll in 2001. This is the first time that a phase shift on a coral leef has been unambiguously associated with man-made structures. This association was made, in part, because of the remoteness of Palmyra and its recent history of minimal human habitation or impact. Phase shifts can have long-term negative ramification for coral reefs, and eradication of organisms responsible for phase shifts in marine ecosystems can be difficult, particularly if such organisms cover a large area. The extensive R. howesii invasion and subsequent loss of coral reef habitat at Palmyra also highlights the importance of rapid removal of shipwrecks on corals reefs to mitigate the potential of reef overgrowth by invasives.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Colgan, M.W.; Hollander, D.
1987-05-01
In March 1954, along the west-central coast of Isabela Island, an upward movement of magma suddenly raised Urvina Bay over 6 m and exposed several square kilometers of carbonate deposits covering a young aa lava flow (around 1000 years old). Results from 6 transect lines across the uplift, 30 cores, and 10 trenches describe the sedimentologic and ecologic transition from barren basalt to diverse carbonate sediments with small coral reefs. Along horizontal transects spanning from 0 to 7 m paleowater depth, there is a seaward progression from beaches, mangroves, and basalt to thick deposits (> 1.6 m) of carbonate sandsmore » and small coral reefs. Variation in water depth, degree of wave exposure, and irregularity of the aa lava topography provided many microhabitats where coral, calcareous algae, and mollusks settled and grew. Eight hermatypic coral species are found throughout the shelf, and three species (i.e., Pavona clavus, Pocillopora damicornis, and Porites lobata) produced five small, isolated, monospecific, coral-reef frameworks. The vertical section seen in cores and trenches shows that calcium carbonate increased upward, whereas volcanic sediments decreased; however, episodic layers occur with high concentrations of basaltic sands. In vertical samples from the central portion of the shelf, the coral population changed from small, isolated colonies of Psammocora (Plesioseris) superficalis near the basalt basement to large reef-forming colonies of Pocillopora damicornis farther upsection. Reefs of the Galapagos Islands are small and less diverse than most Pacific reefs. Nonetheless, understanding their temporal successional development should throw light on the origin and history of larger oceanic reefs in the Pacific.« less
NASA Astrophysics Data System (ADS)
Hongo, Chuki; Kurihara, Haruko; Golbuu, Yimnang
2018-03-01
Tropical cyclones (TCs) and sea level rise (SLR) cause major problems including beach erosion, saltwater intrusion into groundwater, and damage to infrastructure in coastal areas. The magnitude and extent of damage is predicted to increase as a consequence of future climate change and local factors. Upward reef growth has attracted attention for its role as a natural breakwater, reducing the risks of natural disasters to coastal communities. However, projections of change in the risk to coastal reefs under conditions of intensified TCs and SLR are poorly quantified. In this study we projected the wave height and water level on Melekeok reef in the Palau Islands by 2100, based on wave simulations under intensified TCs (significant wave height at the outer ocean: SWHo = 8.7-11.0 m; significant wave period at the outer ocean: SWPo = 13-15 s) and SLR (0.24-0.98 m). To understand effects of upward reef growth on the reduction of the wave height and water level, the simulation was conducted for two reef condition scenarios: a degraded reef and a healthy reef. Moreover, analyses of reef growth based on a drilled core provided an assessment of the coral community and rate of reef production necessary to reduce the risk from TCs and SLR on the coastal areas. According to our calculations under intensified TCs and SLR by 2100, significant wave heights at the reef flat (SWHr) will increase from 1.05-1.24 m at present to 2.14 m if reefs are degraded. Similarly, by 2100 the water level at the shoreline (WLs) will increase from 0.86-2.10 m at present to 1.19-3.45 m if reefs are degraded. These predicted changes will probably cause beach erosion, saltwater intrusion into groundwater, and damage to infrastructure, because the coastal village is located at ˜ 3 m above the present mean sea level. These findings imply that even if the SWHr is decreased by only 0.1 m by upward reef growth, it will probably reduce the risks of costal damages. Our results showed that a healthy reef will reduce a maximum of 0.44 m of the SWHr. According to analysis of drilled core, corymbose Acropora corals will be key to reducing the risks, and 2.6-5.8 kg CaCO3 m-2 yr-1, equivalent to > 8 % of coral cover, will be required to keep a healthy reef by 2100. This study highlights that the maintaining reef growth (as a function of coral cover) in the future is effective in reducing the risk of coastal damage arising from wave action. Although the present study focuses on Melekeok fringing reef, many coral reefs are in the same situation under conditions of intensified TCs and SLR, and therefore the results of this study are applicable to other reefs. These researches are critical in guiding policy development directed at disaster prevention for small island nations and for developing and developed countries.
Conformal blocks from Wilson lines with loop corrections
NASA Astrophysics Data System (ADS)
Hikida, Yasuaki; Uetoko, Takahiro
2018-04-01
We compute the conformal blocks of the Virasoro minimal model or its WN extension with large central charge from Wilson line networks in a Chern-Simons theory including loop corrections. In our previous work, we offered a prescription to regularize divergences from loops attached to Wilson lines. In this paper, we generalize our method with the prescription by dealing with more general operators for N =3 and apply it to the identity W3 block. We further compute general light-light blocks and heavy-light correlators for N =2 with the Wilson line method and compare the results with known ones obtained using a different prescription. We briefly discuss general W3 blocks.
NASA Astrophysics Data System (ADS)
Plaisance, L.; Knowlton, N.; Paulay, G.; Meyer, C.
2009-12-01
The cryptofauna associated with coral reefs accounts for a major part of the biodiversity in these ecosystems but has been largely overlooked in biodiversity estimates because the organisms are hard to collect and identify. We combine a semi-quantitative sampling design and a DNA barcoding approach to provide metrics for the diversity of reef-associated crustacean. Twenty-two similar-sized dead heads of Pocillopora were sampled at 10 m depth from five central Pacific Ocean localities (four atolls in the Northern Line Islands and in Moorea, French Polynesia). All crustaceans were removed, and partial cytochrome oxidase subunit I was sequenced from 403 individuals, yielding 135 distinct taxa using a species-level criterion of 5% similarity. Most crustacean species were rare; 44% of the OTUs were represented by a single individual, and an additional 33% were represented by several specimens found only in one of the five localities. The Northern Line Islands and Moorea shared only 11 OTUs. Total numbers estimated by species richness statistics (Chao1 and ACE) suggest at least 90 species of crustaceans in Moorea and 150 in the Northern Line Islands for this habitat type. However, rarefaction curves for each region failed to approach an asymptote, and Chao1 and ACE estimators did not stabilize after sampling eight heads in Moorea, so even these diversity figures are underestimates. Nevertheless, even this modest sampling effort from a very limited habitat resulted in surprisingly high species numbers.
Observable Signatures of Energy Release in Braided Coronal Loops
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pontin, D. I.; Janvier, M.; Tiwari, S. K.
We examine the turbulent relaxation of solar coronal loops containing non-trivial field line braiding. Such field line tangling in the corona has long been postulated in the context of coronal heating models. We focus on the observational signatures of energy release in such braided magnetic structures using MHD simulations and forward modeling tools. The aim is to answer the following question: if energy release occurs in a coronal loop containing braided magnetic flux, should we expect a clearly observable signature in emissions? We demonstrate that the presence of braided magnetic field lines does not guarantee a braided appearance to themore » observed intensities. Observed intensities may—but need not necessarily—reveal the underlying braided nature of the magnetic field, depending on the degree and pattern of the field line tangling within the loop. However, in all cases considered, the evolution of the braided loop is accompanied by localized heating regions as the loop relaxes. Factors that may influence the observational signatures are discussed. Recent high-resolution observations from Hi-C have claimed the first direct evidence of braided magnetic fields in the corona. Here we show that both the Hi-C data and some of our simulations give the appearance of braiding at a range of scales.« less
Lidz, Barbara H.
2001-01-01
Introduction In recent years, the health of the entire coral reef ecosystem that lines the outer shelf off the Florida Keys has declined markedly. In particular, loss of those coral species that are the building blocks of solid reef framework has significant negative implications for economic vitality of the region. What are the reasons for this decline? Is it due to natural change, or are human activities (recreational diving, ship groundings, farmland runoff, nutrient influx, air-borne contaminants, groundwater pollutants) a contributing factor and if so, to what extent? At risk of loss are biologic resources of the reefs, including habitats for endangered species in shoreline mangroves, productive marine and wetland nurseries, and economic fisheries. A healthy reef ecosystem builds a protective offshore barrier to catastrophic wave action and storm surges generated by tropical storms and hurricanes. In turn, a healthy reef protects the homes, marinas, and infrastructure on the Florida Keys that have been designed to capture a lucrative tourism industry. A healthy reef ecosystem also protects inland agricultural and livestock areas of South Florida whose produce and meat feed much of the United States and other parts of the world. In cooperation with the National Oceanic and Atmospheric Administration's (NOAA) National Marine Sanctuary Program, the U.S. Geological Survey (USGS) continues longterm investigations of factors that may affect Florida's reefs. One of the first steps in distinguishing between natural change and the effects of human activities, however, is to determine how coral reefs have responded to past environmental change, before the advent of man. By so doing, accurate scientific information becomes available for Marine Sanctuary management to understand natural change and thus to assess and regulate potential human impact better. The USGS studies described here evaluate the distribution (location) and historic vitality (thickness) of Holocene reefs in South Florida, relative to type of underlying bedrock morphology, and their varied natural response to rising sea level. These studies also assess movement and accumulation of sands, relative to direction of prevailing energy, and origin of the component sand grains. Geophysical data collected with highresolution sound-wave instruments that provide pictures of the sediment and bedrock are used to interpret sediment thickness. Reef thickness is determined by collecting limestone rock cores by drilling. Drill cores through reefs are used to identify the coral species that built them and to determine how reefs reacted to rising sea level. These data are supplemented by using isotope-dating techniques to derive the carbon-14 (C14) age of the corals and mangrove peat in the cores. Mangrove peat forms in very shallow water and at the shoreline but is found today buried beneath offshore reefs.
STS-32 Earth observation of the western Coral Sea and the Great Barrier Reef
1990-01-20
STS032-520-014 (9-20 Jan. 1990) --- STS-32 astronauts took this 70mm scene showing phytoplankton oralgal bloom in the northwest Coral Sea. The Western Coral Sea and the Great Barrier Reef waters offshore Queensland, Australia are the sites of some of the larger concentrations or "blooms" of phytoplankton and algae in the open ocean. In the instance illustrated here, the leading edge of a probable concentration of algae or phytoplankton is seen as a light irregular line and sheen between the offshore Great Barrier Reef and the Queensland coast. Previous phytoplankton concentrations in this area have been reported by ships at sea as having formed floating mats as thick as two meters. This picture was used by the STS-32 astronauts at their Jan. 30, 1990 post-flight press conference.
The Palmyra Atoll Research Consortium
Suchanek, Thomas H.
2012-01-01
Palmyra functions as a living laboratory. It is a low-lying coral atoll located about 1,800 kilometers south/southwest of Hawaii near the equator in the central Pacific Ocean (latitude 5°53'N, longitude 162°05'W). Palmyra Atoll and nearby Kingman Reef are U.S. territories and represent the northern atolls/reefs of the U.S. Line Islands. Palmyra also is one of the nine sovereign territories of the United States commonly referred to as the U.S. Pacific Remote Island Areas (PRIAs) that straddle the equator (fig. 1). Palmyra Atoll and nearby Kingman Reef also were included as part of the seven territories that comprise the Pacific Remote Islands Marine National Monument set aside by President Bush in 2009 (Proclamation 8336), which includes the same territories as the PRIAS, except Rose Atoll and Midway Atoll.
Microbial communities in the reef water at Kham Island, lower Gulf of Thailand.
Somboonna, Naraporn; Wilantho, Alisa; Monanunsap, Somchai; Chavanich, Suchana; Tangphatsornruang, Sithichoke; Tongsima, Sissades
2017-01-01
Coral reefs are among the most biodiverse habitats on Earth, but knowledge of their associated marinemicrobiome remains limited. To increase the understanding of the coral reef ecosystem in the lower Gulf of Thailand, this study utilized 16S and 18S rRNA gene-based pyrosequencing to identify the prokaryotic and eukaryotic microbiota present in the reef water at Kham Island, Trat province, Thailand (N6.97 E100.86). The obtained result was then compared with the published microbiota from different coral reef water and marine sites. The coral reefs at Kham Island are of the fringe type. The reefs remain preserved and abundant. The community similarity indices (i.e., Lennon similarity index, Yue & Clayton similarity index) indicated that the prokaryotic composition of Kham was closely related to that of Kra, another fringing reef site in the lower Gulf of Thailand, followed by coral reef water microbiota at GS048b (Cooks Bay, Fr. Polynesia), Palmyra (Northern Line Islands, United States) and GS108b (Coccos Keeling, Australia), respectively. Additionally, the microbial eukaryotic populations at Kham was analyzed and compared with the available database at Kra. Both eukaryotic microbiota, in summer and winter seasons, were correlated. An abundance of Dinophysis acuminata was noted in the summer season, in accordance with its reported cause of diarrhoeatic shellfish outbreak in the summer season elsewhere. The slightly lower biodiversity in Kham than at Kra might reflect the partly habitat difference due to coastal anthropogenic activities and minor water circulation, as Kham locates close to the mainland and is surrounded by islands (e.g., Chang and Kut islands). The global marine microbiota comparison suggested relatively similar microbial structures among coral sites irrespective of geographical location, supporting the importance of coral-associated marine microbiomes, and Spearman's correlation analysis between community membership and factors of shore distance and seawater temperature indicated potential correlation of these factors ( p -values < 0.05) with Kham, Kra, and some other coral and coastal sites. Together, this study provided the second marine microbial database for the coral reef of the lower Gulf of Thailand, and a comparison of the coral-associated marine microbial diversity among global ocean sites.
NASA Technical Reports Server (NTRS)
Choudhary, Debi Prasad; Gary, Allen G.
1998-01-01
The high-resolution H(sub alpha) images observed during the decay phase of a long duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas, all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long duration flare was observed in the region of low magnetic shear at the photosphere. The H(sub alpha) loop activity started soon after the maximum phase of the flare. There were few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 deg with the east-west axis. Gradually, increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue-shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to the chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H(sub alpha) loops. The height of the H(sub alpha) loops were derived by comparing them with the computed field lines. From the temporal evolution of the H(sub alpha) loop activity, we derive the negative rate of appearance of H(sub alpha) features as a function of height. It is found that the field lines oriented along one of the neutral lines was sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long duration flare.
NASA Astrophysics Data System (ADS)
Lee, K.; Imada, S.; Moon, Y.; Lee, J.
2013-12-01
We investigate spectral properties of a cool loop and a dark lane over a limb active region on 2007 March 14 by the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in coronal spectral lines and rooted on a bright point. We determine their electron densities, Doppler velocities, and non-thermal velocities with height over the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII and Fe XIV spectra. Under the hydrostatic equilibrium and isothermal assumption, we determine their temperatures from the density scale height. Comparing the scale height temperatures to the peak formation temperatures of the spectral lines, we note that the scale height temperature of the cool loop is consistent with a peak formation temperature of the Fe XII and the scale height temperatures of the dark lane from each spectral lines are much lower than their peak formation temperatures. The non-thermal velocity in the cool loop slightly decreases along the loop while that in the dark lane sharply falls off with height. The variation of non-thermal velocity with height in the cool loop and the dark lane is contrast to that in off-limb polar coronal holes which are considered as source of the solar wind. Such a decrease in the non-thermal velocity may be explained by wave damping near the solar surface or turbulence due to magnetic reconnection near the bright point.
NASA Astrophysics Data System (ADS)
Davies, Sarah W.; Strader, Marie E.; Kool, Johnathan T.; Kenkel, Carly D.; Matz, Mikhail V.
2017-09-01
Remote populations can influence connectivity and may serve as refugia from climate change. We investigated two reef-building corals ( Pseudodiploria strigosa and Orbicella franksi) from the Flower Garden Banks (FGB), the most isolated, high-latitude Caribbean reef system, which, until recently, retained high coral cover. We characterized coral size-frequency distributions, quantified larval mortality rates and onset of competence ex situ, estimated larval production, and created detailed biophysical models incorporating these parameters to evaluate the source-sink dynamics at the FGB from 2009 to 2012. Estimated mortality rates were similar between species, but pre-competency differed dramatically; P. strigosa was capable of metamorphosis within 2.5 d post-fertilization (dpf) and was competent at least until 8 dpf, while O. franksi was not competent until >20 dpf and remained competent up to 120 dpf. To explore the effect of such contrasting life histories on connectivity, we modeled larval dispersal from the FGB assuming pelagic larval durations (PLD) of either 3-20 d, approximating laboratory-measured pre-competency of P. strigosa, or 20-120 d, approximating pre-competency observed in O. franksi. Surprisingly, both models predicted similar probabilities of local retention at the FGB, either by direct rapid reseeding or via long-term persistence in the Loop Current with larvae returning to the FGB within a month. However, our models predicted that short PLDs would result in complete isolation from the rest of the Caribbean, while long PLDs allowed for larval export to more distant northern Caribbean reefs, highlighting the importance of quantifying larval pre-competency dynamics when parameterizing biophysical models to predict larval connectivity. These simulations suggest that FGB coral populations are likely to be largely self-sustaining and highlight the potential of long-PLD corals, such as endangered Orbicella, to act as larval sources for other degraded Caribbean reefs.
NASA Astrophysics Data System (ADS)
Johns, E. M.; Smith, R. H.; Lamkin, J. T.; Birbriezca, L. C.; Vasquez-Yeomans, L.; Cordero, E. S.
2008-05-01
The coastal waters of south Florida, including the coral reefs of NOAA's Florida Keys National Marine Sanctuary (FKNMS), are directly connected by means of strong ocean currents with upstream waters of the western Caribbean Sea and the Gulf of Mexico. The Caribbean Current and the Loop Current provide a rapid conduit for transport from Mexican and Belizean coral reefs, located off the eastern shore of the Yucatan Peninsula, to nearshore regions of northern Cuba, Florida, and the Bahamas. Interdisciplinary cruise data collected in August 2002, March 2006 and January 2007 aboard the NOAA Ship Gordon Gunter, in combination with satellite-tracked surface drifter trajectories and remote sensing imagery, clearly show the highly variable and dynamic nature of the regional current regimes and provide a means of quantifying the potential pathways and transport rates of the coastal waters and their biological and chemical constituents from one region to another. Results from these cruises and ancillary data show that the study areas are connected with rapid transport time scales, and that frontal eddies and gyres play an important role in establishing the time and length scales of this connectivity. Such direct physical connectivity between the coral reef biota of these geographically separated spawning grounds via ocean currents may have an important influence on the degree of biological connectivity between regional larval populations. Initial analyses of ichthyoplankton surveys and inshore collections along the Yucatan mesoamerican reef suggest large scale variability in both local recruitment and large scale spatial distribution. Despite strong northward flowing currents, inshore collections indicate that local recruitment in some areas is strongly influenced by small scale circulation patterns. However, the distribution of spawning aggregations along the Yucatan coast suggests a larger role for the Caribbean Current. Determining the interactions between the larger scale circulation patterns and the smaller scale biological processes is a key research objective for understanding the observed regional population connections.
Possible return of Acropora cervicornis at Pulaski Shoal, Dry Tortugas National Park, Florida
Lidz, Barbara H.; Zawada, David G.
2013-01-01
Seabed classification is essential to assessing environmental associations and physical status in coral reef ecosystems. At Pulaski Shoal in Dry Tortugas National Park, Florida, nearly continuous underwater-image coverage was acquired in 15.5 hours in 2009 along 70.2 km of transect lines spanning ~0.2 km2. The Along-Track Reef-Imaging System (ATRIS), a boat-based, high-speed, digital imaging system, was used. ATRIS-derived benthic classes were merged with a QuickBird satellite image to create a habitat map that defines areas of senile coral reef, carbonate sand, seagrasses, and coral rubble. This atypical approach of starting with extensive, high-resolution in situ imagery and extrapolating between transect lines using satellite imagery leverages the strengths of each remote-sensing modality. The ATRIS images also captured the spatial distribution of two species once common on now-degraded Florida-Caribbean coral reefs: the stony staghorn coral Acropora cervicornis, a designated threatened species, and the long-spined urchin Diadema antillarum. This article documents the utility of ATRIS imagery for quantifying number and estimating age of A. cervicornis colonies (n = 400, age range, 5–11 y) since the severe hypothermic die-off in the Dry Tortugas in 1976–77. This study is also the first to document the largest number of new colonies of A. cervicornis tabulated in an area of the park where coral-monitoring stations maintained by the Fish and Wildlife Research Institute have not been established. The elevated numbers provide an updated baseline for tracking revival of this species at Pulaski Shoal.
A rotating, expanding disk in the Wolf-Rayet star EZ Canis Majoris?
NASA Technical Reports Server (NTRS)
Schulte-Ladbeck, R. E.; Nordsieck, K. H.; Nook, M. A.; Magalhaes, A. M.; Taylor, M.
1990-01-01
The discovery of linear polarization changes across the extended wings of He II lines, mainly the strong 4-3 transition at 4686 A, in the WN5 star EZ CMa, is reported. When the polarization across the line profiles is plotted in the Stokes parameters plane, it traces loops clockwise from the blue wing through line center to the red, rather than straight lines. Such polarization loops are reminiscent of what is observed in the Balmer lines of Be stars. The continuum polarization in EZ CMa can be understood by an axisymmetric, electron-scattering envelope, with the decrease in polarization in He II being caused by an increase in absorptive opacity in the lines and dilution by unpolarized line emission, while the variations in position angle are due to the Doppler-shifted absorptive opacity and/or scattered line photons. As the sense of rotation in the loops is also independent of phase of this alleged Wolf-Rayet + compact binary, the polarized line profiles are the signature of a rotating, expanding wind geometry around a single star.
Sedimentation processes in a coral reef embayment: Hanalei Bay, Kauai
Storlazzi, C.D.; Field, M.E.; Bothner, Michael H.; Presto, M.K.; Draut, A.E.
2009-01-01
Oceanographic measurements and sediment samples were collected during the summer of 2006 as part of a multi-year study of coastal circulation and the fate of terrigenous sediment on coral reefs in Hanalei Bay, Kauai. The goal of this study was to better understand sediment dynamics in a coral reef-lined embayment where winds, ocean surface waves, and river floods are important processes. During a summer period that was marked by two wave events and one river flood, we documented significant differences in sediment trap collection rates and the composition, grain size, and magnitude of sediment transported in the bay. Sediment trap collection rates were well correlated with combined wave-current near-bed shear stresses during the non-flood periods but were not correlated during the flood. The flood's delivery of fine-grained sediment to the bay initially caused high turbidity and sediment collection rates off the river mouth but the plume dispersed relatively quickly. Over the next month, the flood deposit was reworked by mild waves and currents and the fine-grained terrestrial sediment was advected around the bay and collected in sediment traps away from the river mouth, long after the turbid surface plume was gone. The reworked flood deposits, due to their longer duration of influence and proximity to the seabed, appear to pose a greater long-term impact to benthic coral reef communities than the flood plumes themselves. The results presented here display how spatial and temporal differences in hydrodynamic processes, which result from variations in reef morphology and orientation, cause substantial variations in the deposition, residence time, resuspension, and advection of both reef-derived and fluvial sediment over relatively short spatial scales in a coral reef embayment.
Suppression of Heating of Coronal Loops Rooted in Opposite Polarity Sunspot Umbrae
NASA Technical Reports Server (NTRS)
Tiwari, Sanjiv K.; Thalmann, Julia K.; Moore, Ronald L.; Panesar, Navdeep K.; Winebarger, Amy R.
2016-01-01
EUV observations of active region (AR) coronae reveal the presence of loops at different temperatures. To understand the mechanisms that result in hotter or cooler loops, we study a typical bipolar AR, near solar disk center, which has moderate overall magnetic twist and at least one fully developed sunspot of each polarity. From AIA 193 and 94 Å images we identify many clearly discernible coronal loops that connect plage or a sunspot of one polarity to an opposite-polarity plage region. The AIA 94 Å images show dim regions in the umbrae of the spots. To see which coronal loops are rooted in a dim umbral area, we performed a non-linear force-free field (NLFFF) modeling using photospheric vector magnetic field measurements obtained with the Heliosesmic Magnetic Imager (HMI) onboard SDO. The NLFFF model, validated by comparison of calculated model field lines with observed loops in AIA 193 and 94 Å, specifies the photospheric roots of the model field lines. Some model coronal magnetic field lines arch from the dim umbral area of the positive-polarity sunspot to the dim umbral area of a negative-polarity sunspot. Because these coronal loops are not visible in any of the coronal EUV and X-ray images of the AR, we conclude they are the coolest loops in the AR. This result suggests that the loops connecting opposite polarity umbrae are the least heated because the field in umbrae is so strong that the convective braiding of the field is strongly suppressed.
Spectroscopic Study of a Dark Lane and a Cool Loop in a Solar Limb Active Region by Hinode/EIS
NASA Astrophysics Data System (ADS)
Lee, Kyoung-Sun; Imada, S.; Moon, Y.-J.; Lee, Jin-Yi
2014-01-01
We investigated a cool loop and a dark lane over a limb active region on 2007 March 14 using the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in the coronal spectral lines and is rooted on a bright point. We examined their electron densities, Doppler velocities, and nonthermal velocities as a function of distance from the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII, and Fe XIV spectra. We also compared the observed density scale heights with the calculated scale heights from each peak formation temperatures of the spectral lines under the hydrostatic equilibrium. We noted that the observed density scale heights of the cool loop are consistent with the calculated heights, with the exception of one observed cooler temperature; we also found that the observed scale heights of the dark lane are much lower than their calculated scale heights. The nonthermal velocity in the cool loop slightly decreases along the loop, while nonthermal velocity in the dark lane sharply falls off with height. Such a decrease in the nonthermal velocity may be explained by wave damping near the solar surface or by turbulence due to magnetic reconnection near the bright point.
2003-05-02
KENNEDY SPACE CENTER, FLA. - A team aboard the Liberty Star secures lines to underwater research equipment being used on an expedition to characterize the condition of the deep-sea coral reefs and reef fish populations in the Oculina Banks, a marine protected area, 20 miles offshore of the east coast of Florida. The equipment includes an underwater robot, a seafloor sampler, and the Passive Acoustic Monitoring System (PAMS), originally developed by NASA to monitor the impact of rocket launches on wildlife refuge lagoons at KSC. The research is sponsored by NOAA Fisheries. The ship departed from Port Canaveral April 29 and will return May 9.
NASA Astrophysics Data System (ADS)
Lindo-Atichati, D.; Curcic, M.; Paris, C. B.; Buston, P. M.
2016-02-01
Determining the appropriate resolution of circulation models often lacks statistical evaluation. Thus, the gains from implementing high-resolution versus less-costly low-resolution models are not always clear. Here we construct a hierarchy of ocean-atmosphere models operating at multiple-scales within a 1×1° domain of the Belizean Barrier Reef (BBR). We compare the dispersion and velocity of 55 surface drifters released in the field in summer 2013 to the dispersion and velocity of simulated drifters under alternative model configurations. Increasing the resolution of the ocean model (from 1/12° to 1/100°, from 1 day to 1 h), the resolution of the atmosphere model forcing (from 1/2° to 1/100°, from 6 h to 1 h), and incorporating tidal forcing incrementally reduces discrepancy between simulated and observed velocities and dispersion. We also investigate the effect of semi-diurnal tides on the local circulation. The model with highest resolution and with tidal forcing resolves higher number of looping trajectories and sub-mesoscale coherent structures. This may be a key factor in reducing discrepancy between simulated and observed velocities and dispersion. Simulations conducted with the highest resolution ocean-atmosphere model and tidal forcing highlight an intensification of the velocity fields throughout the summer and reveal several processes: mesoscale anticyclonic circulation around Glovers Reef, and recurrent sub-mesoscale cyclonic eddies formed in the vicinity of Columbus Island. This study provides a general framework to estimate the best surface transport prediction from different ocean-atmosphere models using metrics derived from high frequency drifters' data. Also, this study provides an evaluated high-resolution ocean-atmosphere model that resolves tides for the Belizean Barrier Reef.
puffers were edible . Collections were made in April during the reproduction period when toxicity was at a maximum. Hook and line, spear, dynamite, and...flavimarginatus; the sea bass Variola louti; the pomacentrids Abudefduf spp. and lethrinids. Underwater movies were taken for food chain studies. A shipment of reef fishes of Fanning Island was also procured.
33 CFR 110.140 - Buzzards Bay, Nantucket Sound, and adjacent waters, Mass.
Code of Federal Regulations, 2014 CFR
2014-07-01
... Phoenix Point; thence 154° along a line which passes 100 yards east of New Bedford Channel Buoys 8, 6, and... through Bird Island Reef Bell Buoy 13; and south of a line bearing 270° from Wings Neck Light. Each vessel... Island Channel 4 Light; thence 129° to a point bearing 209°, approximately 733 yards, from Wings Neck...
33 CFR 110.140 - Buzzards Bay, Nantucket Sound, and adjacent waters, Mass.
Code of Federal Regulations, 2013 CFR
2013-07-01
... Phoenix Point; thence 154° along a line which passes 100 yards east of New Bedford Channel Buoys 8, 6, and... through Bird Island Reef Bell Buoy 13; and south of a line bearing 270° from Wings Neck Light. Each vessel... Island Channel 4 Light; thence 129° to a point bearing 209°, approximately 733 yards, from Wings Neck...
33 CFR 110.140 - Buzzards Bay, Nantucket Sound, and adjacent waters, Mass.
Code of Federal Regulations, 2012 CFR
2012-07-01
... Phoenix Point; thence 154° along a line which passes 100 yards east of New Bedford Channel Buoys 8, 6, and... through Bird Island Reef Bell Buoy 13; and south of a line bearing 270° from Wings Neck Light. Each vessel... Island Channel 4 Light; thence 129° to a point bearing 209°, approximately 733 yards, from Wings Neck...
Couttolenc, Alan; Espinoza, Cesar; Fernández, José J; Norte, Manuel; Plata, Gabriela B; Padrón, José M; Shnyreva, Alla; Trigos, Ángel
2016-08-01
It is well known that marine fungi are an excellent source of biologically active secondary metabolites, and by 2011, it was reported that over 400 bioactive metabolites were derived from marine fungi. This study establishes the basis for future research on antiproliferative compounds of marine endophytes inhabited in the Veracruz Reef System. Isolation of the 34 fungal strains was carried out by microbiological method from samples of sponges, corals, and other biological material from the Veracruz Reef System. The fungal biomass and broth were separated and extracted with a mixture of solvents MeOH:CHCl3. Characterization and molecular identification of the fungal strains were performed through microbiological methods and the analysis of the ITS-rDNA regions. Antiproliferative activity was tested at a dose of 250 μg/mL on human solid tumor cell lines HBL-100, HeLa, SW1573, T-47D, and WiDr by the SRB assay after 48 h-exposure to the fungal extracts. The extracts from five isolates showed an antiproliferative effect against one or more of the tested cell lines (percentage growth < 50%). The mycelial extract from the isolate LAEE 03 manifested the highest activity against the five cell lines (% PG of 17 HBL-100, 19 HeLa, 23 SW1573, -6 T-47D, and 10 WiDr) and the strain was identified as Curvularia trifolii (Kauffman) Boedijn (Pleosporaceae). The results obtained indicate that the extract from a marine derived C. trifolii has the antiproliferative effect, thus suggesting that this organism is a good candidate for further analysis of its metabolites.
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred
1988-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred (Inventor)
1987-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
The massive soft anomalous dimension matrix at two loops
NASA Astrophysics Data System (ADS)
Mitov, Alexander; Sterman, George; Sung, Ilmo
2009-05-01
We study two-loop anomalous dimension matrices in QCD and related gauge theories for products of Wilson lines coupled at a point. We verify by an analysis in Euclidean space that the contributions to these matrices from diagrams that link three massive Wilson lines do not vanish in general. We show, however, that for two-to-two processes the two-loop anomalous dimension matrix is diagonal in the same color-exchange basis as the one-loop matrix for arbitrary masses at absolute threshold and for scattering at 90 degrees in the center of mass. This result is important for applications of threshold resummation in heavy quark production.
Toward a Quantitative Comparison of Magnetic Field Extrapolations and Observed Coronal Loops
NASA Astrophysics Data System (ADS)
Warren, Harry P.; Crump, Nicholas A.; Ugarte-Urra, Ignacio; Sun, Xudong; Aschwanden, Markus J.; Wiegelmann, Thomas
2018-06-01
It is widely believed that loops observed in the solar atmosphere trace out magnetic field lines. However, the degree to which magnetic field extrapolations yield field lines that actually do follow loops has yet to be studied systematically. In this paper, we apply three different extrapolation techniques—a simple potential model, a nonlinear force-free (NLFF) model based on photospheric vector data, and an NLFF model based on forward fitting magnetic sources with vertical currents—to 15 active regions that span a wide range of magnetic conditions. We use a distance metric to assess how well each of these models is able to match field lines to the 12202 loops traced in coronal images. These distances are typically 1″–2″. We also compute the misalignment angle between each traced loop and the local magnetic field vector, and find values of 5°–12°. We find that the NLFF models generally outperform the potential extrapolation on these metrics, although the differences between the different extrapolations are relatively small. The methodology that we employ for this study suggests a number of ways that both the extrapolations and loop identification can be improved.
Example Level 1 Ada/SQL (Structured Query Language) System Software
1987-09-01
PUTLINE ("EMPNAME JOB SALARY COMMISSION"); loop FETCH ( CURSOR ); INTO ( VEMP NAME , STR LAST ); T LEN INTEGER (STR LAST - V EMP NAME’FIRST + 1); for I in 1...begin PUT_LINE ("EMPNAME JOB SALARY DEPT"); loop FETCH (CURSOR); INTO ( VEMP NAME , STRLAST ); T_LEN := INTEGER (STRLAST - V_EMPNAME’FIRST + 1); for I in...NUMBERS OPEN ( CURSOR ); begin PUT_LINE ("EMP_NAME SALARY JOB"); loop FETCH ( CURSOR ); INTO ( VEMP NAME , STRLAST ); T_LEN := INTEGER (STR_LAST
2018-06-11
Giant, bright coronal loops trace out the magnetic field lines above an active region from June 4-6, 2018. The wavelength of extreme ultraviolet light shown here is emitted by ionized iron travelling along the field lines, super-heated to approximately 1 million degrees K. Coronal loops were not seen in this level of detail until the Solar Dynamics Observatory was launched in 2010 and came online, giving solar scientists new data with which to study the Sun and its processes. https://photojournal.jpl.nasa.gov/catalog/PIA22508
Experimental study of high-performance cooling system pipeline diameter and working fluid amount
NASA Astrophysics Data System (ADS)
Nemec, Patrik; Malcho, Milan; Hrabovsky, Peter; Papučík, Štefan
2016-03-01
This work deals with heat transfer resulting from the operation of power electronic components. Heat is removed from the mounting plate, which is the evaporator of the loop thermosyphon to the condenser and by natural convection is transferred to ambient. This work includes proposal of cooling device - loop thermosyphon, with its construct and follow optimization of cooling effect. Optimization proceeds by selecting the quantity of working fluid and selection of diameters vapour line and liquid line of loop thermosyphon.
NASA Astrophysics Data System (ADS)
Jorry, Stéphan J.; Camoin, Gilbert F.; Jouet, Gwénaël; Roy, Pascal Le; Vella, Claude; Courgeon, Simon; Prat, Sophie; Fontanier, Christophe; Paumard, Victorien; Boulle, Julien; Caline, Bruno; Borgomano, Jean
2016-04-01
Isolated carbonate platforms occur throughout the geologic record, from Archean to present. Although the respective roles of tectonics, sediment supply and sea-level changes in the stratigraphical architecture of these systems are relatively well constrained, the details of the nature and controls on the variability of sedimentological patterns between and within individual geomorphologic units on platforms have been barely investigated. This study aims at describing and comparing geomorphological and sedimentological features of surficial sediments and fossil reefs from three isolated carbonate platforms located in the SW Indian Ocean (Glorieuses, Juan de Nova and Europa). These carbonate platforms are relatively small and lack continuous reef margins, which have developed only on windward sides. Field observations, petrographic characterization and grain-size analyses are used to illustrate the spatial patterns of sediment accumulation on these platforms. The internal parts of both Glorieuses and Juan de Nova platforms are blanketed by sand dunes with medium to coarse sands with numerous reef pinnacles. Skeletal components including coral, green algae, and benthic foraminifera fragments prevail in these sediments. Europa platform exhibits a similar skeletal assemblage dominated by coral fragments, with the absence of wave-driven sedimentary bodies. Fossil reefs from the Last interglacial (125,000 years BP) occur on the three platforms. At Glorieuses, a succession of drowned terraces detected on seismic lines is interpreted as reflecting the last deglacial sea-level rise initiated 20,000 years ago. These findings highlight the high potential of these platforms to study past sea-level changes and the related reef response, which remain poorly documented in the SW Indian Ocean.
Microbial Ecology of Four Coral Atolls in the Northern Line Islands
Smriga, Steven; Edwards, Robert A.; Angly, Florent; Wegley, Linda; Hatay, Mark; Hall, Dana; Brown, Elysa; Haynes, Matthew; Krause, Lutz; Sala, Enric; Sandin, Stuart A.; Thurber, Rebecca Vega; Willis, Bette L.; Azam, Farooq; Knowlton, Nancy; Rohwer, Forest
2008-01-01
Microbes are key players in both healthy and degraded coral reefs. A combination of metagenomics, microscopy, culturing, and water chemistry were used to characterize microbial communities on four coral atolls in the Northern Line Islands, central Pacific. Kingman, a small uninhabited atoll which lies most northerly in the chain, had microbial and water chemistry characteristic of an open ocean ecosystem. On this atoll the microbial community was equally divided between autotrophs (mostly Prochlorococcus spp.) and heterotrophs. In contrast, Kiritimati, a large and populated (∼5500 people) atoll, which is most southerly in the chain, had microbial and water chemistry characteristic of a near-shore environment. On Kiritimati, there were 10 times more microbial cells and virus-like particles in the water column and these microbes were dominated by heterotrophs, including a large percentage of potential pathogens. Culturable Vibrios were common only on Kiritimati. The benthic community on Kiritimati had the highest prevalence of coral disease and lowest coral cover. The middle atolls, Palmyra and Tabuaeran, had intermediate densities of microbes and viruses and higher percentages of autotrophic microbes than either Kingman or Kiritimati. The differences in microbial communities across atolls could reflect variation in 1) oceaonographic and/or hydrographic conditions or 2) human impacts associated with land-use and fishing. The fact that historically Kingman and Kiritimati did not differ strongly in their fish or benthic communities (both had large numbers of sharks and high coral cover) suggest an anthropogenic component in the differences in the microbial communities. Kingman is one of the world's most pristine coral reefs, and this dataset should serve as a baseline for future studies of coral reef microbes. Obtaining the microbial data set, from atolls is particularly important given the association of microbes in the ongoing degradation of coral reef ecosystems worldwide. PMID:18301735
Microbial ecology of four coral atolls in the Northern Line Islands.
Dinsdale, Elizabeth A; Pantos, Olga; Smriga, Steven; Edwards, Robert A; Angly, Florent; Wegley, Linda; Hatay, Mark; Hall, Dana; Brown, Elysa; Haynes, Matthew; Krause, Lutz; Sala, Enric; Sandin, Stuart A; Thurber, Rebecca Vega; Willis, Bette L; Azam, Farooq; Knowlton, Nancy; Rohwer, Forest
2008-02-27
Microbes are key players in both healthy and degraded coral reefs. A combination of metagenomics, microscopy, culturing, and water chemistry were used to characterize microbial communities on four coral atolls in the Northern Line Islands, central Pacific. Kingman, a small uninhabited atoll which lies most northerly in the chain, had microbial and water chemistry characteristic of an open ocean ecosystem. On this atoll the microbial community was equally divided between autotrophs (mostly Prochlorococcus spp.) and heterotrophs. In contrast, Kiritimati, a large and populated ( approximately 5500 people) atoll, which is most southerly in the chain, had microbial and water chemistry characteristic of a near-shore environment. On Kiritimati, there were 10 times more microbial cells and virus-like particles in the water column and these microbes were dominated by heterotrophs, including a large percentage of potential pathogens. Culturable Vibrios were common only on Kiritimati. The benthic community on Kiritimati had the highest prevalence of coral disease and lowest coral cover. The middle atolls, Palmyra and Tabuaeran, had intermediate densities of microbes and viruses and higher percentages of autotrophic microbes than either Kingman or Kiritimati. The differences in microbial communities across atolls could reflect variation in 1) oceaonographic and/or hydrographic conditions or 2) human impacts associated with land-use and fishing. The fact that historically Kingman and Kiritimati did not differ strongly in their fish or benthic communities (both had large numbers of sharks and high coral cover) suggest an anthropogenic component in the differences in the microbial communities. Kingman is one of the world's most pristine coral reefs, and this dataset should serve as a baseline for future studies of coral reef microbes. Obtaining the microbial data set, from atolls is particularly important given the association of microbes in the ongoing degradation of coral reef ecosystems worldwide.
The effect of nonequilibrium ionization on ultraviolet line shifts in the solar transition region
NASA Technical Reports Server (NTRS)
Spadaro, D.; Noci, G.; Zappala, R. A.; Antiochos, S. K.
1990-01-01
The line profiles and wavelength positions of all the important emission lines due to carbon were computed for a variety of steady state siphon flow loop models. For the lines from the lower ionization states (C II-C IV) a preponderance of blueshifts was found, contrary to the observations. The lines from the higher ionization states can show either a net red- or blueshift, depending on the position of the loop on the solar disk. Similar results are expected for oxygen. It is concluded that the observed redshifts cannot be explained by the models proposed here.
Conversion from mutual helicity to self-helicity observed with IRIS
NASA Astrophysics Data System (ADS)
Li, L. P.; Peter, H.; Chen, F.; Zhang, J.
2014-10-01
Context. In the upper atmosphere of the Sun observations show convincing evidence for crossing and twisted structures, which are interpreted as mutual helicity and self-helicity. Aims: We use observations with the new Interface Region Imaging Spectrograph (IRIS) to show the conversion of mutual helicity into self-helicity in coronal structures on the Sun. Methods: Using far UV spectra and slit-jaw images from IRIS and coronal images and magnetograms from SDO, we investigated the evolution of two crossing loops in an active region, in particular, the properties of the Si IV line profile in cool loops. Results: In the early stage two cool loops cross each other and accordingly have mutual helicity. The Doppler shifts in the loops indicate that they wind around each other. As a consequence, near the crossing point of the loops (interchange) reconnection sets in, which heats the plasma. This is consistent with the observed increase of the line width and of the appearance of the loops at higher temperatures. After this interaction, the two new loops run in parallel, and in one of them shows a clear spectral tilt of the Si IV line profile. This is indicative of a helical (twisting) motion, which is the same as to say that the loop has self-helicity. Conclusions: The high spatial and spectral resolution of IRIS allowed us to see the conversion of mutual helicity to self-helicity in the (interchange) reconnection of two loops. This is observational evidence for earlier theoretical speculations. Movie associated with Fig. 1 and Appendix A are available in electronic form at http://www.aanda.org
Automated Coronal Loop Identification using Digital Image Processing Techniques
NASA Astrophysics Data System (ADS)
Lee, J. K.; Gary, G. A.; Newman, T. S.
2003-05-01
The results of a Master's thesis study of computer algorithms for automatic extraction and identification (i.e., collectively, "detection") of optically-thin, 3-dimensional, (solar) coronal-loop center "lines" from extreme ultraviolet and X-ray 2-dimensional images will be presented. The center lines, which can be considered to be splines, are proxies of magnetic field lines. Detecting the loops is challenging because there are no unique shapes, the loop edges are often indistinct, and because photon and detector noise heavily influence the images. Three techniques for detecting the projected magnetic field lines have been considered and will be described in the presentation. The three techniques used are (i) linear feature recognition of local patterns (related to the inertia-tensor concept), (ii) parametric space inferences via the Hough transform, and (iii) topological adaptive contours (snakes) that constrain curvature and continuity. Since coronal loop topology is dominated by the magnetic field structure, a first-order magnetic field approximation using multiple dipoles provides a priori information that has also been incorporated into the detection process. Synthesized images have been generated to benchmark the suitability of the three techniques, and the performance of the three techniques on both synthesized and solar images will be presented and numerically evaluated in the presentation. The process of automatic detection of coronal loops is important in the reconstruction of the coronal magnetic field where the derived magnetic field lines provide a boundary condition for magnetic models ( cf. , Gary (2001, Solar Phys., 203, 71) and Wiegelmann & Neukirch (2002, Solar Phys., 208, 233)). . This work was supported by NASA's Office of Space Science - Solar and Heliospheric Physics Supporting Research and Technology Program.
Quantum mechanics in non-inertial reference frames: Time-dependent rotations and loop prolongations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Klink, W.H., E-mail: william-klink@uiowa.edu; Wickramasekara, S., E-mail: wickrama@grinnell.edu; Department of Physics, Grinnell College, Grinnell, IA 50112
2013-09-15
This is the fourth in a series of papers on developing a formulation of quantum mechanics in non-inertial reference frames. This formulation is grounded in a class of unitary cocycle representations of what we have called the Galilean line group, the generalization of the Galilei group to include transformations amongst non-inertial reference frames. These representations show that in quantum mechanics, just as the case in classical mechanics, the transformations to accelerating reference frames give rise to fictitious forces. In previous work, we have shown that there exist representations of the Galilean line group that uphold the non-relativistic equivalence principle asmore » well as representations that violate the equivalence principle. In these previous studies, the focus was on linear accelerations. In this paper, we undertake an extension of the formulation to include rotational accelerations. We show that the incorporation of rotational accelerations requires a class of loop prolongations of the Galilean line group and their unitary cocycle representations. We recover the centrifugal and Coriolis force effects from these loop representations. Loops are more general than groups in that their multiplication law need not be associative. Hence, our broad theoretical claim is that a Galilean quantum theory that holds in arbitrary non-inertial reference frames requires going beyond groups and group representations, the well-established framework for implementing symmetry transformations in quantum mechanics. -- Highlights: •A formulation of Galilean quantum mechanics in non-inertial reference frames is presented. •The Galilei group is generalized to infinite dimensional Galilean line group. •Loop prolongations of Galilean line group contain central extensions of Galilei group. •Unitary representations of the loops are constructed. •These representations lead to terms in the Hamiltonian corresponding to fictitious forces, including centrifugal and Coriolis forces.« less
Spectroscopic study of a dark lane and a cool loop in a solar limb active region by Hinode/EIS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lee, Kyoung-Sun; Imada, S.; Moon, Y.-J.
2014-01-10
We investigated a cool loop and a dark lane over a limb active region on 2007 March 14 using the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in the coronal spectral lines and is rooted on a bright point. We examined their electron densities, Doppler velocities, and nonthermal velocities as a function of distance from the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII, and Femore » XIV spectra. We also compared the observed density scale heights with the calculated scale heights from each peak formation temperatures of the spectral lines under the hydrostatic equilibrium. We noted that the observed density scale heights of the cool loop are consistent with the calculated heights, with the exception of one observed cooler temperature; we also found that the observed scale heights of the dark lane are much lower than their calculated scale heights. The nonthermal velocity in the cool loop slightly decreases along the loop, while nonthermal velocity in the dark lane sharply falls off with height. Such a decrease in the nonthermal velocity may be explained by wave damping near the solar surface or by turbulence due to magnetic reconnection near the bright point.« less
Full characterization of dislocations in ion-irradiated polycrystalline UO2
NASA Astrophysics Data System (ADS)
Onofri, C.; Legros, M.; Léchelle, J.; Palancher, H.; Baumier, C.; Bachelet, C.; Sabathier, C.
2017-10-01
In order to fully characterize the dislocation loops and lines features (Burgers vectors, habit/slip planes, interstitial or vacancy type) induced by irradiation in UO2, polycrystalline thin foils were irradiated with 4 MeV Au or 390 keV Xe ions at different temperatures (25, 600 and 800 °C) and fluences (0.5 and 1 × 1015 ions/cm2), and further analyzed using TEM. In all the cases, this study, performed on a large number of dislocation loops (diameter ranging from 10 to 80 nm) and for the first time on several dislocation lines, reveals unfaulted prismatic dislocation loops with an interstitial nature and Burgers vectors only along the <110>-type directions. Almost 60% of the studied loops are purely prismatic type and lie on {110} habit planes perpendicular to the Burgers vector directions. The others lie on the {110} or {111} planes, which are neither perpendicular to the Burgers vectors, nor contain them. About 87% of the dislocation lines, formed by loop overlapping as fluence increases, are edge or mixed type in the <100>{100} slip systems, as those induced under mechanical load.
Code of Federal Regulations, 2013 CFR
2013-07-01
... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING 404 PROGRAM DEFINITIONS... mining-related materials;” after the words “utility lines; and artificial reefs. (2) In addition..., overburden from mining or other excavation activities, and materials used to create any structure or...
Code of Federal Regulations, 2014 CFR
2014-07-01
... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING 404 PROGRAM DEFINITIONS... mining-related materials;” after the words “utility lines; and artificial reefs. (2) In addition..., overburden from mining or other excavation activities, and materials used to create any structure or...
Code of Federal Regulations, 2012 CFR
2012-07-01
... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING 404 PROGRAM DEFINITIONS... mining-related materials;” after the words “utility lines; and artificial reefs. (2) In addition..., overburden from mining or other excavation activities, and materials used to create any structure or...
Code of Federal Regulations, 2013 CFR
2013-10-01
... shoreward boundary is the line of mean low water (MLW; 33 CFR 2.20). Within these boundaries, discrete areas... or permitted man-made structures such as aids-to-navigation (ATONs), artificial reefs, boat ramps...
Code of Federal Regulations, 2014 CFR
2014-10-01
... shoreward boundary is the line of mean low water (MLW; 33 CFR 2.20). Within these boundaries, discrete areas... or permitted man-made structures such as aids-to-navigation (ATONs), artificial reefs, boat ramps...
Code of Federal Regulations, 2012 CFR
2012-10-01
... shoreward boundary is the line of mean low water (MLW; 33 CFR 2.20). Within these boundaries, discrete areas... or permitted man-made structures such as aids-to-navigation (ATONs), artificial reefs, boat ramps...
DOE Office of Scientific and Technical Information (OSTI.GOV)
Goreau, T.J.; Hilbertz, W.
Electrolysis of seawater is used to precipitate limestone on top of underwater steel structures to create growing artificial reefs to enhance coral growth, restore coral reef habitat, provide shelter for fish, shellfish, and other marine organisms, generate white sand for beach replenishment, and protect shore lines from wave erosion. Films and slides will be shown of existing structures in Jamaica, Panama, and the Maldives, and projects being developed in these and other locations will be evaluated. The method is unique because it creates the only artificial reef structures that generate the natural limestone substrate from which corals and coral reefsmore » are composed, speeding the settlement and growth of calcareous organisms, and attracting the full range of other reef organisms. The structures are self-repairing and grow stronger with age. Power sources utilized include batteries, battery chargers, photovoltaic panels, and windmills. The cost of seawalls and breakwaters produced by this method is less than one tenth that of conventional technology. Because the technology is readily scaled up to build breakwaters and artificial islands able to keep pace with rising sea level it is capable of playing an important role in protecting low lying coastal areas from the effects of global climate change.« less
NASA Astrophysics Data System (ADS)
Hyart, T.; Ojajärvi, R.; Heikkilä, T. T.
2018-04-01
Three-dimensional topological semimetals can support band crossings along one-dimensional curves in the momentum space (nodal lines or Dirac lines) protected by structural symmetries and topology. We consider rhombohedrally (ABC) stacked honeycomb lattices supporting Dirac lines protected by time-reversal, inversion and spin rotation symmetries. For typical band structure parameters there exists a pair of nodal lines in the momentum space extending through the whole Brillouin zone in the stacking direction. We show that these Dirac lines are topologically distinct from the usual Dirac lines which form closed loops inside the Brillouin zone. In particular, an energy gap can be opened only by first merging the Dirac lines going through the Brillouin zone in a pairwise manner so that they turn into closed loops inside the Brillouin zone, and then by shrinking these loops into points. We show that this kind of topological phase transition can occur in rhombohedrally stacked honeycomb lattices by tuning the ratio of the tunneling amplitudes in the directions perpendicular and parallel to the layers. We also discuss the properties of the surface states in the different phases of the model.
An improved external recycle reactor for determining gas-solid reaction kinetics
NASA Technical Reports Server (NTRS)
Miller, Irvin M.; Hoyt, Ronald F.
1987-01-01
These improvements in the recycle system effectively eliminate initial concentration variation by two modifications: (1) a vacuum line connection to the recycle loop which permits this loop to be evacuated and then filled with the test gas mixture to slightly above atmospheric pressure; and (2) a bypass line across the reactor which permits the reactor to be held under vacuum while the rest of the recycle loop is filled with test gas. A three-step procedure for bringing the feed gas mixture into contact with the catalyst at time zero is described.
NASA Astrophysics Data System (ADS)
Jernsletten, J. A.
2005-11-01
A TEM survey was carried out in Pima County, Arizona, in January 2003. Data was collected using 100 m Tx loops and a ferrite-cored magnetic coil Rx antenna, using a 16 Hz sounding frequency, which is sensitive to slightly salty groundwater. Prominent features in the data are the ~500 m depth of investigation and the ~120 m depth to the water table, confirmed by data from four USGS test wells sur-rounding the field area. Note also the conductive (~20-40 Ωm) clay-rich soil above the water table. During May and June of 2003, a Fast-Turnoff (early time) TEM survey was carried out at the Peña de Hierro field area of the MARTE project, near the town of Nerva, Spain. Data was collected using 20 m and 40 m Tx loop antennae and 10 m loop Rx antennae, with a 32 Hz sounding frequency. Data from Line 4 (of 16) from this survey, collected using 40 m Tx loops, show ~200 m depth of investigation and a conduc-tive high at ~90 m depth below Station 20 (second station of 10 along this line). This is the water table, matching the 431 m MSL elevation of the nearby pit lake. Data from Line 15 and Line 14 of the Rio Tinto survey, collected using 20 m Tx loops, achieve ~50 m depth of investigation and show con-ductive highs at ~15 m depth below Station 50 (Line 15) and Station 30 (Line 14), interpreted as subsurface water flow under mine tailings matching surface flows seen coming out from under the tailings, and shown on maps. Both of the interpretations from Rio Tinto data (Line 4, and Lines 15 & 14) were confirmed by preliminary results from the MARTE ground truth drilling campaign carried out in September and October 2003. Drill Site 1 was moved ~50 m based on recommendations built on data from Line 15 and Line 14 of the Fast-Turnoff TEM survey.
NASA Astrophysics Data System (ADS)
Williams, Ashley J.; Ballagh, Aaron C.; Begg, Gavin A.; Murchie, Cameron D.; Currey, Leanne M.
2008-09-01
The reef line fishery (RLF) in eastern Torres Strait (ETS) is unique in that it has both a commercial indigenous sector and a commercial non-indigenous sector. Recently, concerns have been expressed by all stakeholders about the long-term sustainability of the fishery. These concerns have been exacerbated by the lack of detailed catch and effort information from both sectors, which has precluded any formal assessment of the fishery. In this paper, we characterise the harvest patterns and effort dynamics of the indigenous and non-indigenous commercial sectors of the ETS RLF using a range of data sources including commercial logbooks, community freezer records, voluntary logbooks and observer surveys. We demonstrate that bycatch is a significant component of the catch for both sectors and identify substantial differences in harvest patterns and effort dynamics between the sectors. Differences between sectors were observed in species composition and spatial and temporal patterns in catch, effort and catch per unit effort. These results highlight the inherent variation in catch and effort dynamics between the two commercial sectors of the ETS RLF and provide valuable information for the development of future assessments and appropriate management strategies for the fishery. The more reliable estimates of harvest patterns and effort dynamics for both sectors obtained from observer surveys will also assist in resolving issues relating to allocation of reef fish resources in Torres Strait.
NASA Astrophysics Data System (ADS)
Doschek, G. A.; Warren, H. P.
2013-12-01
The plasma volume above the soft X-ray emitting loop tops is of particular interest for studying the formation of flare loops. We present observations of non-thermal motions (turbulence) determined from spectral line profiles Fe XXIII and Fe XXIV ions. We compare the non-thermal motions at temperatures near 10 MK with the motions along the same lines-of-sight determined from lines of coronal ions such as Fe XII, Fe XIV, and Fe XV formed at 1-2 MK. We discuss the results in terms of predictions of the effects of magnetic reconnection and non-thermal motion results obtained in flares from earlier X-ray Yohkoh observations of line profiles of Fe XXV and Ca XIX. Fe XXV is formed at significantly higher temperatures than any strong flare EUV spectral line observed by EIS or by imaging telescopes such as AIA or TRACE. This work is supported by a NASA Hinode grant.
Protected areas mitigate diseases of reef-building corals by reducing damage from fishing.
Lamb, Joleah B; Williamson, David H; Russ, Garry R; Willis, Bette L
2015-09-01
Parks and protected areas have been instrumental in reducing anthropogenic sources of damage in terrestrial and aquatic environments. Pathogen invasion often succeeds physical wounding and injury, yet links between the reduction of damage and the moderation of disease have not been assessed. Here, we examine the utility of no-take marine reserves as tools for mitigating diseases that affect reef-building corals. We found that sites located within reserves had fourfold reductions in coral disease prevalence compared to non-reserve sites (80466 corals surveyed). Of 31 explanatory variables assessed, coral damage and the abundance of derelict fishing line best explained differences in disease assemblages between reserves and non-reserves. Unexpectedly, we recorded significantly higher levels of disease, coral damage, and derelict fishing line in non-reserves with fishing gear restrictions than in those without gear restrictions. Fishers targeting stocks perceived to be less depleted, coupled with enhanced site access from immediately adjacent boat moorings, may explain these unexpected patterns. Significant correlations between the distance from mooring sites and prevalence values for a ciliate disease known to infest wounded tissue (r = -0.65), coral damage (r = -0.64), and the abundance of derelict fishing line (r = -0.85) corroborate this interpretation. This is the first study to link disease with recreational use intensity in a park, emphasizing the need to evaluate the placement of closures and their direct relationship to ecosystem health. Since corals are modular, ecological processes that govern reproductive and competitive fitness are frequently related to colony surface area therefore, even low levels of cumulative tissue loss from progressing diseases pose significant threats to reef coral persistence. Disease mitigation through reductions in physical injury in areas where human activities are concentrated is another mechanism by which protected areas may improve ecosystem resilience in a changing climate.
Geological and technological assessment of artificial reef sites, Louisiana outer continental shelf
Pope, D.L.; Moslow, T.F.; Wagner, J.B.
1993-01-01
This paper describes the general procedures used to select sites for obsolete oil and gas platforms as artificial reefs on the Louisiana outer continental shelf (OCS). The methods employed incorporate six basic steps designed to resolve multiple-use conflicts that might otherwise arise with daily industry and commercial fishery operations, and to identify and assess both geological and technological constraints that could affect placement of the structures. These steps include: (1) exclusion mapping; (2) establishment of artificial reef planning areas; (3) database compilation; (4) assessment and interpretation of database; (5) mapping of geological and man-made features within each proposed reef site; and (6) site selection. Nautical charts, bathymetric maps, and offshore oil and gas maps were used for exclusion mapping, and to select nine regional planning areas. Pipeline maps were acquired from federal agencies and private industry to determine their general locations within each planning area, and to establish exclusion fairways along each pipeline route. Approximately 1600 line kilometers of high-resolution geophysical data collected by federal agencies and private industry was acquired for the nine planning areas. These data were interpreted to determine the nature and extent of near-surface geologic features that could affect placement of the structures. Seismic reflection patterns were also characterized to evaluate near-bottom sedimentation processes in the vicinity of each reef site. Geotechnical borings were used to determine the lithological and physical properties of the sediment, and for correlation with the geophysical data. Since 1987, five sites containing 10 obsolete production platforms have been selected on the Louisiana OCS using these procedures. Industry participants have realized a total savings of approximately US $1 500 000 in salvaging costs by converting these structures into artificial reefs. ?? 1993.
NASA Astrophysics Data System (ADS)
McCook, L. J.; Almany, G. R.; Berumen, M. L.; Day, J. C.; Green, A. L.; Jones, G. P.; Leis, J. M.; Planes, S.; Russ, G. R.; Sale, P. F.; Thorrold, S. R.
2009-06-01
The global decline in coral reefs demands urgent management strategies to protect resilience. Protecting ecological connectivity, within and among reefs, and between reefs and other ecosystems is critical to resilience. However, connectivity science is not yet able to clearly identify the specific measures for effective protection of connectivity. This article aims to provide a set of principles or practical guidelines that can be applied currently to protect connectivity. These ‘rules of thumb’ are based on current knowledge and expert opinion, and on the philosophy that, given the urgency, it is better to act with incomplete knowledge than to wait for detailed understanding that may come too late. The principles, many of which are not unique to connectivity, include: (1) allow margins of error in extent and nature of protection, as insurance against unforeseen or incompletely understood threats or critical processes; (2) spread risks among areas; (3) aim for networks of protected areas which are: (a) comprehensive and spread—protect all biotypes, habitats and processes, etc., to capture as many possible connections, known and unknown; (b) adequate—maximise extent of protection for each habitat type, and for the entire region; (c) representative—maximise likelihood of protecting the full range of processes and spatial requirements; (d) replicated—multiple examples of biotypes or processes enhances risk spreading; (4) protect entire biological units where possible (e.g. whole reefs), including buffers around core areas. Otherwise, choose bigger rather than smaller areas; (5) provide for connectivity at a wide range of dispersal distances (within and between patches), emphasising distances <20-30 km; and (6) use a portfolio of approaches, including but not limited to MPAs. Three case studies illustrating the application of these principles to coral reef management in the Bohol Sea (Philippines), the Great Barrier Reef (Australia) and Kimbe Bay (Papua New Guinea) are described.
Recovery of coral cover in records spanning 44 yr for reefs in Kāne`ohe Bay, Oa`hu, Hawai`i
NASA Astrophysics Data System (ADS)
Stimson, John
2018-03-01
Published and unpublished long-term studies are assembled to examine trends in coral cover and the dependence of change in coral cover on the initial coral cover in Kāne`ohe Bay over the last 44 yr. Each study showed there had been periods of increase in coral cover in the bay and showed that the rate of change in cover has been inversely dependent on the initial cover at a site. When coral cover is high on upper reef slopes, the fragile structure of reefs in this sheltered bay often collapses, resulting in a decrease in coral cover. The rate of change in coral cover was also inversely dependent on cover in one of the two studies that included analysis of reef-flat corals; the cause of decrease in cover in this habitat is thought to be attributable to particularly low sea levels in Hawai`i in the late 1990s and 2009-2010. The inverse relationship between initial coral cover and change in cover, and the intersections of the regression lines of these variables with the x-axis at intermediate values of coral cover, is indicative of resilience in this ecosystem over the last 44 yr. In the 1970s, the invasive macroscopic green alga Dictyosphaeria cavernosa covered a high percentage of coral habitat and commonly displaced corals from the reef slope and outer reef flats; the change was cited as an example of a phase shift on a reef. This alga has virtually disappeared from the bay, thus increasing the space available to corals; its disappearance is coincident with the increase in coral cover. Other species of macroalgae, including alien species, have not replaced D. cavernosa as major space competitors. The increase in coral cover and virtual disappearance of D. cavernosa constitute an example of a phase-shift reversal.
Maynard, Jeffrey A; Anthony, Kenneth R N; Afatta, Siham; Dahl-Tacconi, Nancy; Hoegh-Guldberg, Ove
2010-10-01
Most of the world's coral reefs line the coasts of developing nations, where impacts from intense and destructive fishing practices form critical conservation issues for managers. Overfishing of herbivorous fishes can cause phase shifts to macroalgal dominance, and fishers' use of rocks as anchors lowers coral cover, giving further competitive advantage to macroalgae. Overfishing and anchoring have been studied extensively, but the role of their interaction in lowering coral reef resilience has not been quantified formally. We analyzed the combined effects of overfishing and rock anchoring on a range of reef habitat types--varying from high coral and low macroalgae cover to low coral and high macroalgae cover--in a marine park in Indonesia. We parameterized a model of coral and algal dynamics with three intensities of anchoring and fishing pressure. Results of the model indicated that damage caused by rock anchoring was equal to or possibly more devastating to coral reefs in the area than the impact of overfishing. This is an important outcome for local managers, who usually have the funds to distribute less-damaging anchors, but normally are unable to patrol regularly and effectively enough to reduce the impact of overfishing. We translated model results into an interactive visual tool that allows managers to explore the benefits of reducing anchoring frequency and fishing pressure. The potential consequences of inaction were made clear: the likelihood that any of the reef habitats will be dominated in the future by macroalgae rather than corals depends on reducing anchoring frequency, fishing pressure, or both. The tool provides a platform for strengthened relationships between managers and conservationists and can facilitate the uptake of recommendations regarding resource allocation and management actions. Conservation efforts for coral reefs in developing nations are likely to benefit from transforming model projections of habitat condition into tools local managers can understand and interact with. © 2010 Society for Conservation Biology.
Temperature Calibration of a Northern Gulf of Mexico Siderastrea siderea Coral
NASA Astrophysics Data System (ADS)
Wagner, A. J.; DeLong, K. L.; Kilbourne, K. H.; Richey, J. N.; Jelinek, K.; Hickerson, E.; Slowey, N. C.
2015-12-01
The Gulf of Mexico (GOM) is sensitive to oceanic and atmospheric variability in both the Atlantic and Pacific Oceans (i.e., Atlantic Multidecadal Oscillation (AMO), El Niño Southern Oscillation (ENSO), Pacific North American Pattern (PNA), and Pacific Decadal Oscillation (PDO)). The major GOM current, the Loop Current, feeds the Gulf Stream as it transports oceanic heat to the northern Atlantic Ocean. The northern GOM is the northernmost summer extent of the western hemisphere warm pool (WHWP) that drives oceanic moisture flux and precipitation into the Americas. Decadally-resolved foraminifera reconstructions from the northern GOM indicates SST was 2 to 4ºC colder on average than today during the Little Ice Age (LIA, ~1850), whereas a subannually-resolved coral reconstruction from the southeastern GOM find 1.5 to 2ºC colder intervals and reduced areal extent of the WHWP on interannual time scales during some intervals of the LIA. However, records capable of resolving annual and subannual SST variability from the northern GOM, necessary for investigating WHWP northern extent, are still lacking. Here we present a new temperature reconstruction for the northern GOM derived from strontium-to-calcium (Sr/Ca) ratios of approximately monthly samples milled from a Siderastrea siderea coral core collected from the Flower Garden Banks National Marine Sanctuary (FGBNMS; 27° 52.5'N, 93° 49'W) growing at a water depth of 20 m. Coral Sr/Ca is calibrated to reef temperature data from FGBNMS Hobotemp data loggers near the reef cap in ~22 m water depth (1986-2004) and to NOAA OISST (1981-2004), which co-varies with the reef temperature (r=0.95, p<0.05, n=146) and consistently captures winter values in reef temperature with slightly warmer summers (0.9ºC on average). The Sr/Ca-SST calibration slope (-0.043, r=-0.89, n=136, p<0.01 for reef temperature; -0.039, r=-0.94, n=275, p<0.01 for OISST) agrees well with published coral Sr/Ca-SST calibrations for S. siderea in the southeastern GOM from shallower water depths.
Thurman, Paul E.; McBride, Richard S.; Sulak, Kenneth J.; Dennis, George D.
2004-01-01
Specimens of the four study species were collected during cruises to outer-continental shelf reefs of the northeastern Gulf of Mexico. Age was estimated for all serranid species using whole otoliths and C. enchrysurus ages were determined from transverse sections of sagittal otoliths. Ring structure observed on otoliths was validated as having an annual periodicity for P. martinicensis using marginal increment analysis. Ring structure on remaining species was assumed to correspond to age (years). Pronotogrammus martinicensis, H. vivanus, S. phoebe, and C. enchrysurus exhibited maximum ages of 9, 8, 5, and 11, respectively. Spatial variations in size-at-age were observed in P. martinicensis populations. Individuals inhabiting reefs in the Madison-Swanson Reserve area on the West Florida Shelf edge exhibited the fastest growth rates, while the slowest growing P. martinicensis were collected from the Alabama Alps Reef, the farthest west study reef. Pronotogrammus martinicensis and H. vivanus are both protogynous hermaphrodites. Evidence of active spawning was observed in the months from February through July for P. martinicensis, and March and May for H. vivanus. Serranus phoebe was observed to be a simultaneous hermaphroditic capable of spawning year-round. Batch fecundity estimates for P. martinicensis ranged from 149-394 oocytes per fish. Size selectivity was evident in our primary sampling method, hook and line using small tandem bait hooks. Smaller size-classes of all species examined were under-represented in our samples, hindering accurate growth modeling. Due to the protogynous nature of P. martinicensis and H. vivanus, hook and line sampling also tended to select for males. Future descriptions of the reproductive biology of both protogynous species would be more complete if less selective sampling methods could be successfully employed. The data presented here contribute to a better assessment of the fish community of the northeastern Gulf of Mexico. Little information on age and reproduction was previously available for the serranid and pomacentrid species investigated in the present study. These species are important links between both planktonic or benthic food resources and economically-valuable groupers, snappers, and amberjacks. If a catastrophic natural or anthropogenic event occurred in these outer continental shelf reef habitats, the resultant loss of these forage species would immediately impact regional fish production via the food chain. This would be particularly true for reef-resident commercial and recreational fish species that depend extensively upon a diet of small forage fish species. Recovery to a stable community, fully repopulated with small forage fish species, would require at least a decade, possibly longer if the habitat had been substantially degraded during the initial disturbance.
Identification and prevalence of coral diseases on three Western Indian Ocean coral reefs.
Séré, Mathieu G; Chabanet, Pascale; Turquet, Jean; Quod, Jean-Pascal; Schleyer, Michael H
2015-06-03
Coral diseases have caused a substantial decline in the biodiversity and abundance of reef-building corals. To date, more than 30 distinct diseases of scleractinian corals have been reported, which cause progressive tissue loss and/or affect coral growth, reproductive capacity, recruitment, species diversity and the abundance of reef-associated organisms. While coral disease research has increased over the last 4 decades, very little is known about coral diseases in the Western Indian Ocean. Surveys conducted at multiple sites in Reunion, South Africa and Mayotte between August 2010 and June 2012 revealed the presence of 6 main coral diseases: black band disease (BBD), white syndrome (WS), pink line syndrome (PLS), growth anomalies (GA), skeleton eroding band (SEB) and Porites white patch syndrome (PWPS). Overall, disease prevalence was higher in Reunion (7.5 ± 2.2%; mean ± SE) compared to South Africa (3.9 ± 0.8%) and Mayotte (2.7 ± 0.3%). Across locations, Acropora and Porites were the genera most susceptible to disease. Spatial variability was detected in both Reunion and South Africa, with BBD and WS more prevalent on shallow than deep reefs. There was also evidence of seasonality in 2 diseases: the prevalence of BBD and WS was higher in summer than winter. This was the first study to investigate the ecology of coral diseases, providing both qualitative and quantitative data, on Western Indian Ocean reefs, and surveys should be expanded to confirm these patterns.
Numerical simulations of loops heated to solar flare temperatures. III - Asymmetrical heating
NASA Technical Reports Server (NTRS)
Cheng, C.-C.; Doschek, G. A.; Karpen, J. T.
1984-01-01
A numerical model is defined for asymmetric full solar flare loop heating and comparisons are made with observational data. The Dynamic Flux Tube Model is used to describe the heating process in terms of one-dimensional, two fluid conservation equations of mass, energy and momentum. An adaptive grid allows for the downward movement of the transition region caused by an advancing conduction front. A loop 20,000 km long is considered, along with a flare heating system and the hydrodynamic evolution of the loop. The model was applied to generating line profiles and spatial X-ray and UV line distributions, which were compared with SMM, P78-1 and Hintori data for Fe, Ca and Mg spectra. Little agreement was obtained, and it is suggested that flares be treated as multi-loop phenomena. Finally, it is concluded that chromospheric evaporation is not an effective mechanism for generating the soft X-ray bursts associated with flares.
NASA Astrophysics Data System (ADS)
Nay, Tiffany J.; Johansen, Jacob L.; Habary, Adam; Steffensen, John F.; Rummer, Jodie L.
2015-12-01
As global temperatures increase, fish populations at low latitudes are thought to be at risk as they are adapted to narrow temperature ranges and live at temperatures close to their thermal tolerance limits. Behavioural movements, based on a preference for a specific temperature ( T pref), may provide a strategy to cope with changing conditions. A temperature-sensitive coral reef cardinalfish ( Cheilodipterus quinquelineatus) was exposed to 28 °C (average at collection site) or 32 °C (predicted end-of-century) for 6 weeks. T pref was determined using a shuttlebox system, which allowed fish to behaviourally manipulate their thermal environment. Regardless of treatment temperature, fish preferred 29.5 ± 0.25 °C, approximating summer average temperatures in the wild. However, 32 °C fish moved more frequently to correct their thermal environment than 28 °C fish, and daytime movements were more frequent than night-time movements. Understanding temperature-mediated movements is imperative for predicting how ocean warming will influence coral reef species and distribution patterns.
2006-07-01
technical approach overview .............................................................................. 4 Figure 2 Magnetic field lines around a loop ...11 Figure 10 HMF (Bx) and loop (Bz) antenna comparison .............................................................. 12...Figure 26 Top view of one proposed receiver loop arrangement. ................................................ 25 Figure 27 Receiver response modeling
2006-07-01
technical approach overview .............................................................................. 4 Figure 2 Magnetic field lines around a loop ...11 Figure 10 HMF (Bx) and loop (Bz) antenna comparison .............................................................. 12 Figure...26 Top view of one proposed receiver loop arrangement. ................................................ 25 Figure 27 Receiver response modeling
FAST TRACK COMMUNICATION: A Temperley-Lieb quantum chain with two- and three-site interactions
NASA Astrophysics Data System (ADS)
Ikhlef, Y.; Jacobsen, J. L.; Saleur, H.
2009-07-01
We study the phase diagram of a quantum chain of spin-1/2 particles whose world lines form a dense loop gas with loop weight n. In addition to the usual two-site interaction corresponding to the XXZ spin chain, we introduce a three-site interaction. The resulting model contains a Majumdar-Ghosh-like gapped phase and a new integrable point, which we solve exactly. We also locate a critical line realizing dilute O(n) criticality, without introducing explicit dilution in the loops. Our results have implications for anisotropic spin chains, as well as anyonic quantum chains.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Xie, Haixia; Li, Bo; Huang, Zhenghua
How the solar corona is heated to high temperatures remains an unsolved mystery in solar physics. In the present study we analyze observations of 50 whole active region loops taken with the Extreme-ultraviolet Imaging Spectrometer on board the Hinode satellite. Eleven loops were classified as cool loops (<1 MK) and 39 as warm loops (1–2 MK). We study their plasma parameters, such as densities, temperatures, filling factors, nonthermal velocities, and Doppler velocities. We combine spectroscopic analysis with linear force-free magnetic field extrapolation to derive the 3D structure and positioning of the loops, their lengths and heights, and the magnetic fieldmore » strength along the loops. We use density-sensitive line pairs from Fe xii, Fe xiii, Si x, and Mg vii ions to obtain electron densities by taking special care of intensity background subtraction. The emission measure loci method is used to obtain the loop temperatures. We find that the loops are nearly isothermal along the line of sight. Their filling factors are between 8% and 89%. We also compare the observed parameters with the theoretical Rosner–Tucker–Vaiana (RTV) scaling law. We find that most of the loops are in an overpressure state relative to the RTV predictions. In a follow-up study, we will report a heating model of a parallel-cascade-based mechanism and will compare the model parameters with the loop plasma and structural parameters derived here.« less
47 CFR 51.319 - Specific unbundling requirements.
Code of Federal Regulations, 2014 CFR
2014-10-01
... copper loop and a second competitive LEC provides digital subscriber line service over the high frequency portion of that same loop. The high frequency portion of the loop consists of the frequency range on the... complete transmission path on the high frequency range between the incumbent LEC's distribution frame (or...
47 CFR 51.319 - Specific unbundling requirements.
Code of Federal Regulations, 2013 CFR
2013-10-01
... copper loop and a second competitive LEC provides digital subscriber line service over the high frequency portion of that same loop. The high frequency portion of the loop consists of the frequency range on the... complete transmission path on the high frequency range between the incumbent LEC's distribution frame (or...
50 CFR 665.598 - Management area.
Code of Federal Regulations, 2014 CFR
2014-10-01
... § 665.598 Management area. The PRIA fishery management area is the EEZ seaward of Palmyra Atoll, Kingman Reef, Jarvis Island, Baker Island, Howland Island, Johnston Atoll, and Wake Island, Pacific Remote Island Areas with the inner boundary a line coterminous with the seaward boundaries of the above atolls...
50 CFR 665.598 - Management area.
Code of Federal Regulations, 2012 CFR
2012-10-01
... § 665.598 Management area. The PRIA fishery management area is the EEZ seaward of Palmyra Atoll, Kingman Reef, Jarvis Island, Baker Island, Howland Island, Johnston Atoll, and Wake Island, Pacific Remote Island Areas with the inner boundary a line coterminous with the seaward boundaries of the above atolls...
50 CFR 665.598 - Management area.
Code of Federal Regulations, 2011 CFR
2011-10-01
... § 665.598 Management area. The PRIA fishery management area is the EEZ seaward of Palmyra Atoll, Kingman Reef, Jarvis Island, Baker Island, Howland Island, Johnston Atoll, and Wake Island, Pacific Remote Island Areas with the inner boundary a line coterminous with the seaward boundaries of the above atolls...
50 CFR 665.598 - Management area.
Code of Federal Regulations, 2013 CFR
2013-10-01
... § 665.598 Management area. The PRIA fishery management area is the EEZ seaward of Palmyra Atoll, Kingman Reef, Jarvis Island, Baker Island, Howland Island, Johnston Atoll, and Wake Island, Pacific Remote Island Areas with the inner boundary a line coterminous with the seaward boundaries of the above atolls...
2003-05-02
KENNEDY SPACE CENTER, FLA. - A view from inside the pilot house of the Liberty Star overlooks the stern where a team secures lines to underwater research equipment being used on an expedition to characterize the condition of the deep-sea coral reefs and reef fish populations in the Oculina Banks. The banks are a marine protected area, 20 miles offshore of the east coast of Florida. The equipment includes an underwater robot, a seafloor sampler, and the Passive Acoustic Monitoring System (PAMS), originally developed by NASA to monitor the impact of rocket launches on wildlife refuge lagoons at KSC. The research is sponsored by NOAA Fisheries. The ship departed from Port Canaveral April 29 and will return May 9.
A century of ocean warming on Florida Keys coral reefs: historic in situ observations
Kuffner, Ilsa B.; Lidz, Barbara H.; Hudson, J. Harold; Anderson, Jeffery S.
2015-01-01
There is strong evidence that global climate change over the last several decades has caused shifts in species distributions, species extinctions, and alterations in the functioning of ecosystems. However, because of high variability on short (i.e., diurnal, seasonal, and annual) timescales as well as the recency of a comprehensive instrumental record, it is difficult to detect or provide evidence for long-term, site-specific trends in ocean temperature. Here we analyze five in situ datasets from Florida Keys coral reef habitats, including historic measurements taken by lighthouse keepers, to provide three independent lines of evidence supporting approximately 0.8 °C of warming in sea surface temperature (SST) over the last century. Results indicate that the warming observed in the records between 1878 and 2012 can be fully accounted for by the warming observed in recent decades (from 1975 to 2007), documented using in situ thermographs on a mid-shore patch reef. The magnitude of warming revealed here is similar to that found in other SST datasets from the region and to that observed in global mean surface temperature. The geologic context and significance of recent ocean warming to coral growth and population dynamics are discussed, as is the future prognosis for the Florida reef tract.
Solid oxide fuel cell power plant with an anode recycle loop turbocharger
Saito, Kazuo; Skiba, Tommy; Patel, Kirtikumar H.
2015-07-14
An anode exhaust recycle turbocharger (100) has a turbocharger turbine (102) secured in fluid communication with a compressed oxidant stream within an oxidant inlet line (218) downstream from a compressed oxidant supply (104), and the anode exhaust recycle turbocharger (100) also includes a turbocharger compressor (106) mechanically linked to the turbocharger turbine (102) and secured in fluid communication with a flow of anode exhaust passing through an anode exhaust recycle loop (238) of the solid oxide fuel cell power plant (200). All or a portion of compressed oxidant within an oxidant inlet line (218) drives the turbocharger turbine (102) to thereby compress the anode exhaust stream in the recycle loop (238). A high-temperature, automotive-type turbocharger (100) replaces a recycle loop blower-compressor (52).
Solid oxide fuel cell power plant with an anode recycle loop turbocharger
Saito, Kazuo; Skiba, Tommy; Patel, Kirtikumar H.
2016-09-27
An anode exhaust recycle turbocharger (100) has a turbocharger turbine (102) secured in fluid communication with a compressed oxidant stream within an oxidant inlet line (218) downstream from a compressed oxidant supply (104), and the anode exhaust recycle turbocharger (100) also includes a turbocharger compressor (106) mechanically linked to the turbocharger turbine (102) and secured in fluid communication with a flow of anode exhaust passing through an anode exhaust recycle loop (238) of the solid oxide fuel cell power plant (200). All or a portion of compressed oxidant within an oxidant inlet line (218) drives the turbocharger turbine (102) to thereby compress the anode exhaust stream in the recycle loop (238). A high-temperature, automotive-type turbocharger (100) replaces a recycle loop blower-compressor (52).
Near optimum digital phase locked loops.
NASA Technical Reports Server (NTRS)
Polk, D. R.; Gupta, S. C.
1972-01-01
Near optimum digital phase locked loops are derived utilizing nonlinear estimation theory. Nonlinear approximations are employed to yield realizable loop structures. Baseband equivalent loop gains are derived which under high signal to noise ratio conditions may be calculated off-line. Additional simplifications are made which permit the application of the Kalman filter algorithms to determine the optimum loop filter. Performance is evaluated by a theoretical analysis and by simulation. Theoretical and simulated results are discussed and a comparison to analog results is made.
Interplay between short-range correlated disorder and Coulomb interaction in nodal-line semimetals
NASA Astrophysics Data System (ADS)
Wang, Yuxuan; Nandkishore, Rahul M.
2017-09-01
In nodal-line semimetals, Coulomb interactions and short-range correlated disorder are both marginal perturbations to the clean noninteracting Hamiltonian. We analyze their interplay using a weak-coupling renormalization group approach. In the clean case, the Coulomb interaction has been found to be marginally irrelevant, leading to Fermi liquid behavior. We extend the analysis to incorporate the effects of disorder. The nodal line structure gives rise to kinematical constraints similar to that for a two-dimensional Fermi surface, which plays a crucial role in the one-loop renormalization of the disorder couplings. For a twofold degenerate nodal loop (Weyl loop), we show that disorder flows to strong coupling along a unique fixed trajectory in the space of symmetry inequivalent disorder couplings. Along this fixed trajectory, all symmetry inequivalent disorder strengths become equal. For a fourfold degenerate nodal loop (Dirac loop), disorder also flows to strong coupling, however, the strengths of symmetry inequivalent disorder couplings remain different. We show that feedback from disorder reverses the sign of the beta function for the Coulomb interaction, causing the Coulomb interaction to flow to strong coupling as well. However, the Coulomb interaction flows to strong coupling asymptotically more slowly than disorder. Extrapolating our results to strong coupling, we conjecture that at low energies nodal line semimetals should be described by a noninteracting nonlinear sigma model. We discuss the relation of our results with possible many-body localization at zero temperatures in such materials.
Global Far-ultraviolet Properties of the Cygnus Loop
NASA Astrophysics Data System (ADS)
Kim, Il-Joong; Seon, Kwang-Il; Lim, Yeo-Myeong; Lee, Dae-Hee; Han, Wonyong; Min, Kyoung-Wook; Edelstein, Jerry
2014-03-01
We present the C III λ977, O VI λλ1032, 1038 and N IV] λ1486 emission line maps of the Cygnus Loop, obtained with the newly processed data of the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR; also known as FIMS) mission. In addition, the Si IV+O IV] line complexes around 1400 Å are resolved into two separate emission lines whose intensity demonstrates a relatively high Si IV region that was predicted in the previous study. The morphological similarity between the O VI and X-ray images, as well as a comparison of the O VI intensity with the value expected from the X-ray results, indicates that large portions of the observed O VI emissions could be produced from X-ray emitting gas. Comparisons of the far-ultraviolet (FUV) images with the optical and H I 21 cm images reveal spatial variations of shock-velocity populations and high FUV extinction in the direction of a previously identified H I cloud. By calculating the FUV line ratios for several subregions of the Cygnus Loop, we investigate the spatial variation of the population of radiative shock velocities as well as the effects of resonance scattering, X-ray emitting gas, and nonradiative shocks. The FUV and X-ray luminosity comparisons between the Cygnus Loop and the Vela supernova remnant suggest that the fraction of shocks in the early evolutionary stages is much larger in the Cygnus Loop.
Passive magnetic bearing for a motor-generator
Post, Richard F [Walnut Creek, CA
2006-07-18
Conductive lap windings are interleaved with conventional loops in the stator of a motor-generator. The rotor provides magnetic induction lines that, when rotated, cut across the lap windings and the loops. When the rotor is laterally displaced from its equilibrium axis of rotation, its magnetic lines of induction induce a current in the interleaved lap windings. The induced current interacts with the magnetic lines of induction of the rotor in accordance with Lenz's law to generate a radial force that returns the rotor to its equilibrium axis of rotation.
Generalized EC&LSS computer program configuration control
NASA Technical Reports Server (NTRS)
Blakely, R. L.
1976-01-01
The generalized environmental control and life support system (ECLSS) computer program (G189A) simulation of the shuttle orbiter ECLSS was upgraded. The G189A component model configuration was changed to represent the current PV102 and subsequent vehicle ECLSS configurations as defined by baseline ARS and ATCS schematics. The diagrammatic output schematics of the gas, water, and freon loops were also revised to agree with the new ECLSS configuration. The accuracy of the transient analysis was enhanced by incorporating the thermal mass effects of the equipment, structure, and fluid in the ARS gas and water loops and in the ATCS freon loops. The sources of the data used to upgrade the simulation are: (1) ATCS freon loop line sizes and lengths; (2) ARS water loop line sizes and lengths; (3) ARS water loop and ATCS freon loop component and equipment weights; and (4) ARS cabin and avionics bay thermal capacitance and conductance values. A single G189A combination master program library tape was generated which contains all of the master program library versions which were previously maintained on separate tapes. A new component subroutine, PIPETL, was developed and incorporated into the G189A master program library.
Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lal, Shankar, E-mail: shankar@rrcat.gov.in; Pant, K. K.
2016-08-15
Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday’s law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled withmore » β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.« less
Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient
NASA Astrophysics Data System (ADS)
Lal, Shankar; Pant, K. K.
2016-08-01
Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday's law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.
Field Keys to Common Hawaiian Marine Animals and Plants.
ERIC Educational Resources Information Center
Hawaii State Dept. of Education, Honolulu. Office of Instructional Services.
Presented are keys for identifying common Hawaiian marine algae, beach plants, reef corals, sea urchins, tidepool fishes, and sea cucumbers. Nearly all species considered can be distinguished by characteristics visible to the naked eye. Line drawings illustrate most plants and animals included, and a list of suggested readings follows each…
Code of Federal Regulations, 2013 CFR
2013-10-01
..., Baker, Howland, and Jarvis Islands, Johnston Atoll, Kingman Reef, and Palmyra Atoll, is defined as...″ 0°28′39″ N. (d) Johnston Atoll. The Johnston Atoll unit of the Monument includes the waters and submerged and emergent lands around Johnston Atoll within an area defined by straight lines connecting the...
Code of Federal Regulations, 2014 CFR
2014-10-01
..., Baker, Howland, and Jarvis Islands, Johnston Atoll, Kingman Reef, and Palmyra Atoll, is defined as...″ 0°28′39″ N. (d) Johnston Atoll. The Johnston Atoll unit of the Monument includes the waters and submerged and emergent lands around Johnston Atoll within an area defined by straight lines connecting the...
Dirac Magnon Nodal Loops in Quasi-2D Quantum Magnets.
Owerre, S A
2017-07-31
In this report, we propose a new concept of one-dimensional (1D) closed lines of Dirac magnon nodes in two-dimensional (2D) momentum space of quasi-2D quantum magnetic systems. They are termed "2D Dirac magnon nodal-line loops". We utilize the bilayer honeycomb ferromagnets with intralayer coupling J and interlayer coupling J L , which is realizable in the honeycomb chromium compounds CrX 3 (X ≡ Br, Cl, and I). However, our results can also exist in other layered quasi-2D quantum magnetic systems. Here, we show that the magnon bands of the bilayer honeycomb ferromagnets overlap for J L ≠ 0 and form 1D closed lines of Dirac magnon nodes in 2D momentum space. The 2D Dirac magnon nodal-line loops are topologically protected by inversion and time-reversal symmetry. Furthermore, we show that they are robust against weak Dzyaloshinskii-Moriya interaction Δ DM < J L and possess chiral magnon edge modes.
NASA Astrophysics Data System (ADS)
Wagner, A. J.; DeLong, K. L.; Kilbourne, H.; Slowey, N. C.
2016-12-01
The Gulf of Mexico (GOM) is sensitive to oceanic and atmospheric variability in both the Atlantic and Pacific Oceans (i.e., Atlantic Multidecadal Oscillation (AMO), El Niño Southern Oscillation (ENSO), Pacific North American pattern (PNA), and Pacific Decadal Oscillation (PDO)). The major GOM current, the Loop Current, feeds the Gulf Stream as it transports oceanic heat to the northern Atlantic Ocean. The northern GOM is the northernmost summer extent of the western hemisphere warm pool (WHWP) that drives oceanic moisture flux and precipitation into the Americas. Decadally-resolved foraminifera reconstructions from the northern GOM indicates SST was 2 to 4ºC colder on average than today during the Little Ice Age (LIA, 1850), whereas a subannually-resolved coral reconstruction from the southeastern GOM find 1.5 to 2ºC colder intervals and reduced areal extent of the WHWP on interannual time scales during some intervals of the LIA. However, records capable of resolving annual and subannual SST variability from the northern GOM, necessary for investigating WHWP northern extent, are still lacking. Here we present a new temperature reconstruction for the northern GOM derived from strontium-to-calcium (Sr/Ca) ratios of approximately monthly samples milled from a Siderastrea siderea coral core collected from the Flower Garden Banks National Marine Sanctuary (FGBNMS; 27° 52.5'N, 93° 49'W) growing at a water depth of 20 m. Coral Sr/Ca and δ18O is calibrated to reef temperature data from FGBNMS Hobotemp data loggers near the reef cap in 22 m water depth (1986-2004) and to NOAA OISST (1981-2004). Coral Sr/Ca co-varies with the reef temperature (r=0.95, p<0.05, n=146) and consistently captures winter values in reef temperature with slightly warmer summers (0.9ºC on average). Pseudocoral analysis is used to assess the relationships between SST and SSS in coral δ18O.
Century-long acidification reveals possible consequences of coral reef sediment dissolution
NASA Astrophysics Data System (ADS)
Fink, A.; Hassenrueck, C.; Guilini, K.; Lichtschlag, A.; Borisov, S.; Fabricius, K.; de Beer, D.
2016-02-01
Coarse permeable carbonate sediments play a key role as biocatalytical filters in element cycling on coral reefs, but are subjected to increased dissolution due to ocean acidification (OA). We investigated coral reef sediment properties and remineralization rates along a pH gradient in an area of volcanic CO2 seeping within a fringing coral reef (Papua New Guinea). In coarse carbonate-rich sediments of the reference site (water column pHT = 8.1) in-situ microprofiles showed a buffered porewater pH of 7.7 to 7.9. In contrast, sites with diffuse CO2 seeping (water column pHT 8.0 to 7.7) experienced porewater pH of less than 6 to 7. At the seep sites, the sediments were almost free of carbonates and were dominated by silicates. We found that this resulted in reduced grain sizes leading to decreased permeability and oxygen penetration into the sediment. Areal oxygen consumption and sulfate reduction rates declined at the seep sites. The pattern in oxygen consumption could be explained by oxygen limitation due to lower permeability. However, sulfate reduction was never limited by electron acceptor, indicating that the seep site sediments were limited in electron donors. In line with lower process rates, abundances of microorganisms and meiofauna declined at the seep sites. Our findings suggest that an enhanced dissolution of carbonate sediments due to OA could impact their biocatalytical filtration function. This could slow down the intense element cycling in coral reefs and other coastal carbonate environments, with consequences for ecosystem productivity and functioning.
Drivers of shoreline change in atoll reef islands of the Tuamotu Archipelago, French Polynesia
NASA Astrophysics Data System (ADS)
Duvat, Virginie K. E.; Salvat, Bernard; Salmon, Camille
2017-11-01
This paper increases by around 30% the sample of atoll reef islands studied from a shoreline change perspective, and covers an under-studied geographical area, i.e. the French Tuamotu Archipelago. It brings new irrefutable evidences on the persistence of reef islands over the last decades, as 77% of the 111 study islands exhibited areal stability while 15% and 8% showed expansion and contraction, respectively. This paper also addresses a key research gap by interpreting the major local drivers controlling recent shoreline and island change, i.e. tropical cyclones and seasonal swells, sediment supply by coral reefs and human activities. The 1983 tropical cyclones had contrasting impacts, depending on the shoreline indicator considered. While they generally caused a marked retreat of the stability line, the base of the beach advanced at some locations, as a result of either sediment reworking or fresh sediment inputs. The post-cyclone fair weather period was characterised by reversed trends indicating island morphological readjustment. Cyclonic waves contributed to island upwards growth, which reached up to 1 m in places, through the transfer of sediments up onto the island surface. However, the steep outer slopes of atolls limited sediment transfers to the reef flat and island system. We found that 57% of the study islands are disturbed by human activities, including 'rural' and uninhabited islands. Twenty-six percent of these islands have lost the capacity to respond to ocean-climate related pressures, including the 'capital' islands concentrating atolls' population, infrastructures and economic activities, which is preoccupying under climate change.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dudík, Jaroslav; Mackovjak, Šimon; Dzifčáková, Elena
2015-07-10
We report on the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) and Hinode/EUV Imaging Spectrograph (EIS) observations of a transient coronal loop. The loop brightens up in the same location after the disappearance of an arcade formed during a B8.9-class microflare 3 hr earlier. EIS captures this loop during its brightening phase, as observed in most of the AIA filters. We use the AIA data to study the evolution of the loop, as well as to perform the differential emission measure (DEM) diagnostics as a function of κ. The Fe xi–Fe xiii lines observed by EIS are used to perform themore » diagnostics of electron density and subsequently the diagnostics of κ. Using ratios involving the Fe xi 257.772 Å self-blend, we diagnose κ ≲ 2, i.e., an extremely non-Maxwellian distribution. Using the predicted Fe line intensities derived from the DEMs as a function of κ, we show that, with decreasing κ, all combinations of ratios of line intensities converge to the observed values, confirming the diagnosed κ ≲ 2. These results represent the first positive diagnostics of κ-distributions in the solar corona despite the limitations imposed by calibration uncertainties.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hahn, M.; Savin, D. W.
We have measured the energy and dissipation of Alfvénic waves in the quiet Sun. A magnetic field model was used to infer the location and orientation of the magnetic field lines along which the waves are expected to travel. The waves were measured using spectral lines to infer the wave amplitude. The waves cause a non-thermal broadening of the spectral lines, which can be expressed as a non-thermal velocity v {sub nt}. By combining the spectroscopic measurements with this magnetic field model, we were able to trace the variation of v {sub nt} along the magnetic field. At each footpointmore » of the quiet-Sun loops, we find that waves inject an energy flux in the range of 1.3-5.5 × 10{sup 5} erg cm{sup –2} s{sup –1}. At the minimum of this range, this amounts to more than 80% of the energy needed to heat the quiet Sun. We also find that these waves are dissipated over a region centered on the top of the loops. The position along the loop where the damping begins is strongly correlated with the length of the loop, implying that the damping mechanism depends on the global loop properties rather than on local collisional dissipation.« less
Xia, Ming-Hua; Xie, Shui-Hua; Wu, Jun; Zhang, Wen-Qing; Chen, Wei-Dong; He, Jian-Hua; Ding, Hao; Hu, Qian-Qin; Wang, Xiao-Peng
2016-07-25
To explore the clinical effects of the triple no loop Endobutton plate combined with Orthcord line in treating acromioclavicular dislocation of Tossy type III. Between February 2011 and September 2013, 36 patients with acromioclavicular dislocation of Tossy type III were treated with triple no loop Endobutton plate and Orthcord line. There were 21 males and 15 females, aged from 9 to 48 years old with an average of (26.41±14.05) years. Couse of disease was from 2 to 7 days in the patients. The patients had the clinical manifestations such as shoulder pain, extension limited, acromioclavicular tenderness, positive organ point sign. Clinical effects were assessed by acromioclavicular scoring system. Thirty six patients were followed up from 8 to 15 months with an average of (12.2±4.3) months. All incisions got primary healing. At the final follow up, all shoulder pain vanished, acromioclavicular joints without tenderness, negative organ point sign. No redislocation and steel plate loosening were found. According to the acromioclavicular scoring system, 31 cases obtained excellent results, 5 good. The method of triple no loop Endobutton plate combined with Orthcord line for acromioclavicular dislocation of Tossy type III has advantage of less risk and complication, good functional rehabilitation and is an ideal method.
Christmas Island, Line Island Group, Pacific Ocean
NASA Technical Reports Server (NTRS)
1990-01-01
Christmas Island (2.0N,158.0W), mid central Pacific Ocean, is considered to be the largest atoll in the world, about 25 km in diameter, and is part of the Line Island Group, a northwest-southeast trending chain of volcanic islands on some of the oldest ocean crust in the Pacific. The lagoon is nearly filled with reef growth leaving only a narrow entrance from the sea and large cocoanut groves are found along the fringes of the lagoon.
STEREOSCOPIC OBSERVATION OF SLIPPING RECONNECTION IN A DOUBLE CANDLE-FLAME-SHAPED SOLAR FLARE
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gou, Tingyu; Liu, Rui; Wang, Yuming
2016-04-20
The 2011 January 28 M1.4 flare exhibits two side-by-side candle-flame-shaped flare loop systems underneath a larger cusp-shaped structure during the decay phase, as observed at the northwestern solar limb by the Solar Dynamics Observatory . The northern loop system brightens following the initiation of the flare within the southern loop system, but all three cusp-shaped structures are characterized by ∼10 MK temperatures, hotter than the arch-shaped loops underneath. The “Ahead” satellite of the Solar Terrestrial Relations Observatory provides a top view, in which the post-flare loops brighten sequentially, with one end fixed while the other apparently slipping eastward. By performingmore » stereoscopic reconstruction of the post-flare loops in EUV and mapping out magnetic connectivities, we found that the footpoints of the post-flare loops are slipping along the footprint of a hyperbolic flux tube (HFT) separating the two loop systems and that the reconstructed loops share similarity with the magnetic field lines that are traced starting from the same HFT footprint, where the field lines are relatively flexible. These results argue strongly in favor of slipping magnetic reconnection at the HFT. The slipping reconnection was likely triggered by the flare and manifested as propagative dimmings before the loop slippage is observed. It may contribute to the late-phase peak in Fe xvi 33.5 nm, which is even higher than its main-phase counterpart, and may also play a role in the density and temperature asymmetry observed in the northern loop system through heat conduction.« less
Current systems of coronal loops in 3D MHD simulations
NASA Astrophysics Data System (ADS)
Warnecke, J.; Chen, F.; Bingert, S.; Peter, H.
2017-11-01
Aims: We study the magnetic field and current structure associated with a coronal loop. Through this we investigate to what extent the assumptions of a force-free magnetic field break down and where they might be justified. Methods: We analyze a three-dimensional (3D) magnetohydrodynamic (MHD) model of the solar corona in an emerging active region with the focus on the structure of the forming coronal loops. The lower boundary of this simulation is taken from a model of an emerging active region. As a consequence of the emerging magnetic flux and the horizontal motions at the surface a coronal loop forms self-consistently. We investigate the current density along magnetic field lines inside (and outside) this loop and study the magnetic and plasma properties in and around this loop. The loop is defined as the bundle of field lines that coincides with enhanced emission in extreme UV. Results: We find that the total current along the emerging loop changes its sign from being antiparallel to parallel to the magnetic field. This is caused by the inclination of the loop together with the footpoint motion. Around the loop, the currents form a complex non-force-free helical structure. This is directly related to a bipolar current structure at the loop footpoints at the base of the corona and a local reduction of the background magnetic field (I.e., outside the loop) caused by the plasma flow into and along the loop. Furthermore, the locally reduced magnetic pressure in the loop allows the loop to sustain a higher density, which is crucial for the emission in extreme UV. The action of the flow on the magnetic field hosting the loop turns out to also be responsible for the observed squashing of the loop. Conclusions: The complex magnetic field and current system surrounding it can only be modeled in 3D MHD models where the magnetic field has to balance the plasma pressure. A one-dimensional coronal loop model or a force-free extrapolation cannot capture the current system and the complex interaction of the plasma and the magnetic field in the coronal loop, despite the fact that the loop is under low-β conditions.
Exposure of coastal ecosystems to river plume spreading across a near-equatorial continental shelf
NASA Astrophysics Data System (ADS)
Tarya, A.; Hoitink, A. J. F.; Vegt, M. Van der; van Katwijk, M. M.; Hoeksema, B. W.; Bouma, T. J.; Lamers, L. P. M.; Christianen, M. J. A.
2018-02-01
The Berau Continental Shelf (BCS) in East Kalimantan, Indonesia, harbours various tropical marine ecosystems, including mangroves, seagrass meadows and coral reefs. These ecosystem are located partly within reach of the Berau River plume, which may affect ecosystem health through exposure to land-derived sediments, nutrients and pollutants carried by the plume. This study aims (1) to assess the exposure risk of the BCS coastal ecosystems to river plume water, measured as exposure time to three different salinity levels, (2) to identify the relationships between these salinity levels and the abundance and diversity of coral and seagrass ecosystems, and (3) to determine a suitable indicator for the impacts of salinity on coral reef and seagrass health. We analysed hydrodynamic models, classified salinity levels, and quantified the correlations between the salinity model parameters and ecological metrics for the BCS systems. An Empirical Orthogonal Functions (EOF) analysis revealed three modes of river plume dispersal patterns, which strongly reflect monsoon seasonality. The first mode, explaining 39% of the variability, was associated with the southward movement of the plume due to northerly winds, while the second and third modes (explaining 29% and 26% of the variability, respectively) were associated with the northeastward migration of the plume related to southwesterly and southerly winds. Exposure to low salinity showed higher correlations with biological indicators than mean salinity, indicating that low salinity is a more suitable indicator for coastal ecosystem health. Significant correlations (R2) were found between exposure time to low salinity (days with salinity values below 25 PSU) with coral cover, coral species richness, seagrass cover, the number of seagrass species, seagrass leaf phosphorus, nitrogen, C:N ratio and iron content. By comparing the correlation coefficients and the slopes of the regression lines, our study suggests that coral reefs are more susceptible to low salinity levels exposure than seagrass meadows. Regarding the risk of corals being exposed to low salinity, nearshore and northern barrier reefs were classified as "high risk", the middle barrier reef as "medium to high risk" and southern barrier reefs as "medium risk". Further offshore, the oceanic reefs were classified as "low risk". Regarding the seagrass meadows, the nearshore region was categorized as "high risk", the barrier reef as "medium to low risk" and oceanic reefs as "low risk". This study contributes to assessing the potential impacts of salinity on the BCS ecosystems, and further provides a knowledge base for marine conservation planning.
Hamylton, Sarah
2014-01-01
A geomorphic assessment of reef system calcification is conducted for past (3200 Ka to present), present and future (2010–2100) time periods. Reef platform sediment production is estimated at 569 m3 yr−1 using rate laws that express gross community carbonate production as a function of seawater aragonite saturation, community composition and rugosity and incorporating estimates of carbonate removal from the reef system. Key carbonate producers including hard coral, crustose coralline algae and Halimeda are mapped accurately (mean R2 = 0.81). Community net production estimates correspond closely to independent census-based estimates made in-situ (R2 = 0.86). Reef-scale outputs are compared with historic rates of production generated from (i) radiocarbon evidence of island deposition initiation around 3200 years ago, and (ii) island volume calculated from a high resolution island digital elevation model. Contemporary carbonate production rates appear to be remarkably similar to historical values of 573 m3 yr−1. Anticipated future seawater chemistry parameters associated with an RCP8.5 emissions scenario are employed to model rates of net community calcification for the period 2000–2100 on the basis of an inorganic aragonite precipitation law, under the assumption of constant benthic community character. Simulations indicate that carbonate production will decrease linearly to a level of 118 m3 yr−1 by 2100 and that by 2150 aragonite saturation levels may no longer support the positive budgetary status necessary to sustain island accretion. Novel aspects of this assessment include the development of rate law parameters to realistically represent the variable composition of coral reef benthic carbonate producers, incorporation of three dimensional rugosity of the entire reef platform and the coupling of model outputs with both historical radiocarbon dating evidence and forward hydrochemical projections to conduct an assessment of island evolution through time. By combining several lines of evidence in a deterministic manner, an assessment of changes in carbonate production is carried out that has tangible geomorphic implications for sediment availability and associated island evolution. PMID:24759700
Modeling Hydrodynamics on the Wave Group Scale in Topographically Complex Reef Environments
NASA Astrophysics Data System (ADS)
Reyns, J.; Becker, J. M.; Merrifield, M. A.; Roelvink, J. A.
2016-02-01
The knowledge of the characteristics of waves and the associated wave-driven currents is important for sediment transport and morphodynamics, nutrient dynamics and larval dispersion within coral reef ecosystems. Reef-lined coasts differ from sandy beaches in that they have a steep offshore slope, that the non-sandy bottom topography is very rough, and that the distance between the point of maximum short wave dissipation and the actual coastline is usually large. At this short wave breakpoint, long waves are released, and these infragravity (IG) scale motions account for the bulk of the water level variance on the reef flat, the lagoon and eventually, the sandy beaches fronting the coast through run-up. These IG energy dominated water level motions are reinforced during extreme events such as cyclones or swells through larger incident band wave heights and low frequency wave resonance on the reef. Recently, a number of hydro(-morpho)dynamic models that have the capability to model these IG waves have successfully been applied to morphologically differing reef environments. One of these models is the XBeach model, which is curvilinear in nature. This poses serious problems when trying to model an entire atoll for example, as it is extremely difficult to build curvilinear grids that are optimal for the simulation of hydrodynamic processes, while maintaining the topology in the grid. One solution to remediate this problem of grid connectivity is the use of unstructured grids. We present an implementation of the wave action balance on the wave group scale with feedback to the flow momentum balance, which is the foundation of XBeach, within the framework of the unstructured Delft3D Flexible Mesh model. The model can be run in stationary as well as in instationary mode, and it can be forced by regular waves, time series or wave spectra. We show how the code is capable of modeling the wave generated flow at a number of topographically complex reef sites and for a number of different forcing conditions, by comparison with field data.
Hamylton, Sarah
2014-01-01
A geomorphic assessment of reef system calcification is conducted for past (3200 Ka to present), present and future (2010-2100) time periods. Reef platform sediment production is estimated at 569 m3 yr-1 using rate laws that express gross community carbonate production as a function of seawater aragonite saturation, community composition and rugosity and incorporating estimates of carbonate removal from the reef system. Key carbonate producers including hard coral, crustose coralline algae and Halimeda are mapped accurately (mean R2 = 0.81). Community net production estimates correspond closely to independent census-based estimates made in-situ (R2 = 0.86). Reef-scale outputs are compared with historic rates of production generated from (i) radiocarbon evidence of island deposition initiation around 3200 years ago, and (ii) island volume calculated from a high resolution island digital elevation model. Contemporary carbonate production rates appear to be remarkably similar to historical values of 573 m3 yr-1. Anticipated future seawater chemistry parameters associated with an RCP8.5 emissions scenario are employed to model rates of net community calcification for the period 2000-2100 on the basis of an inorganic aragonite precipitation law, under the assumption of constant benthic community character. Simulations indicate that carbonate production will decrease linearly to a level of 118 m3 yr-1 by 2100 and that by 2150 aragonite saturation levels may no longer support the positive budgetary status necessary to sustain island accretion. Novel aspects of this assessment include the development of rate law parameters to realistically represent the variable composition of coral reef benthic carbonate producers, incorporation of three dimensional rugosity of the entire reef platform and the coupling of model outputs with both historical radiocarbon dating evidence and forward hydrochemical projections to conduct an assessment of island evolution through time. By combining several lines of evidence in a deterministic manner, an assessment of changes in carbonate production is carried out that has tangible geomorphic implications for sediment availability and associated island evolution.
Coral reefs in Saudi Arabia: 3.5 years after the Gulf War oil spill
NASA Astrophysics Data System (ADS)
Vogt, I. P.
1995-11-01
As a consequence of the 1991 Gulf War, 6-8 million barrels of oil were released into the marine environment and a total of 1.12 billion barrels were burned in the Kuwaiti oil fields. In order to detect delayed effects of the Gulf War pollution, six permanent transect lines were placed on Saudi Arabian offshore and inshore reefs. A comparison of three sets of video recordings taken between 1992 and 1994 indicated a significant increase in live coral cover. Therefore, it has been concluded that corals in Saudi Arabia survived the largest oil spill on record remarkably unscathed, with no visible signs of immediate or late effects up to 3.5 years after the Gulf War.
Explaining observed red and blue-shifts using multi-stranded coronal loops
NASA Astrophysics Data System (ADS)
Regnier, S.; Walsh, R. W.; Pearson, J.
2012-03-01
Magnetic plasma loops have been termed the building blocks of the solar atmosphere. However, it must be recognised that if the range of loop structures we can observe do consist of many ''sub-resolution'' elements, then current one-dimensional hydrodynamic models are really only applicable to an individual plasma element or strand. Thus a loop should be viewed is an amalgamation of these strands. They could operate in thermal isolation from one another with a wide range of temperatures occurring across the structural elements. This scenario could occur when the energy release mechanism consists of localised, discrete bursts of energy that are due to small scale reconnection sites within the coronal magnetic field- the nanoflare coronal heating mechanism. These energy bursts occur in a time-dependent manner, distributed along the loop/strand length, giving a heating function that depends on space and time. An important observational discovery with the Hinode/EIS spectrometer is the existence of red and blue-shifts in coronal loops depending on the location of the footpoints (inner or outer parts of the active region), and the temperature of the emission line in which the Doppler shifts are measured. Based on the multi-stranded model developed by Sarkar and Walsh (2008, ApJ, 683, 516), we show that red and blue-shifts exist in different simulated Hinode/EIS passbands: cooler lines (OV-SiVII) being dominated by red-shifts, whilst hotter lines (FeXV-CaXVII) are a combination of both. The distribution of blue-shifts depends on the energy input and not so much on the heating location. Characteristic Doppler shifts generated fit well with observed values. We also simulate the Hinode/EIS rasters to closely compare our simulation with the observations. Even if not statistically significant, loops can have footpoints with opposite Doppler shifts.
A Study of Some Problems in Network Information Theory
ERIC Educational Resources Information Center
Kamath, Sudeep Uday
2013-01-01
Red snapper, "Lutjanus campechanus," were sampled with hook and line at natural (n = 33) and artificial (n = 27) reef sites in the northern Gulf of Mexico from 2009-2011. Stomachs (n = 708) were extracted and their contents preserved for gut content analysis, and muscle tissue samples (n = 200) were dissected and frozen for stable…
Reserves as tools for alleviating impacts of marine disease
Wenger, Amelia S.; Devlin, Michelle J.; Ceccarelli, Daniela M.; Williamson, David H.; Willis, Bette L.
2016-01-01
Marine protected areas can prevent over-exploitation, but their effect on marine diseases is less clear. We examined how marine reserves can reduce diseases affecting reef-building corals following acute and chronic disturbances. One year after a severe tropical cyclone, corals inside reserves had sevenfold lower levels of disease than those in non-reserves. Similarly, disease prevalence was threefold lower on reserve reefs following chronic exposure to terrestrial run-off from a degraded river catchment, when exposure duration was below the long-term site average. Examination of 35 predictor variables indicated that lower levels of derelict fishing line and injured corals inside reserves were correlated with lower levels of coral disease in both case studies, signifying that successful disease mitigation occurs when activities that damage reefs are restricted. Conversely, reserves were ineffective in moderating disease when sites were exposed to higher than average levels of run-off, demonstrating that reductions in water quality undermine resilience afforded by reserve protection. In addition to implementing protected areas, we highlight that disease management efforts should also target improving water quality and limiting anthropogenic activities that cause injury. PMID:26880842
Reserves as tools for alleviating impacts of marine disease.
Lamb, Joleah B; Wenger, Amelia S; Devlin, Michelle J; Ceccarelli, Daniela M; Williamson, David H; Willis, Bette L
2016-03-05
Marine protected areas can prevent over-exploitation, but their effect on marine diseases is less clear. We examined how marine reserves can reduce diseases affecting reef-building corals following acute and chronic disturbances. One year after a severe tropical cyclone, corals inside reserves had sevenfold lower levels of disease than those in non-reserves. Similarly, disease prevalence was threefold lower on reserve reefs following chronic exposure to terrestrial run-off from a degraded river catchment, when exposure duration was below the long-term site average. Examination of 35 predictor variables indicated that lower levels of derelict fishing line and injured corals inside reserves were correlated with lower levels of coral disease in both case studies, signifying that successful disease mitigation occurs when activities that damage reefs are restricted. Conversely, reserves were ineffective in moderating disease when sites were exposed to higher than average levels of run-off, demonstrating that reductions in water quality undermine resilience afforded by reserve protection. In addition to implementing protected areas, we highlight that disease management efforts should also target improving water quality and limiting anthropogenic activities that cause injury. © 2016 The Author(s).
NASA Astrophysics Data System (ADS)
Price, N.; Rohwer, F. L.; Stuart, S. A.; Andersson, A.; Smith, J.
2012-12-01
The metabolic activity of resident organisms can cause spatio-temporal variability in carbonate chemistry within the benthic boundary layer, and thus potentially buffer the global impacts of ocean acidification. But, little is known about the capacity for particular species assemblages to contribute to natural daily variability in carbonate chemistry. We encapsulated replicate areas (~3m2) of reef across six Northern Line Islands in the central Pacific for 24 hrs to quantify feedbacks to carbonate chemistry within the benthic boundary layer from community metabolism. Underneath each 'tent', we quantified relative abundance and biomass of each species of corals and algae. We coupled high temporal resolution time series data on the natural diurnal variability in pH, dissolved oxygen, salinity, and temperature (using autonomous sensors) with resident organisms' net community calcification and productivity rates (using change in total dissolved carbon and total alkalinity over time) to examine feedbacks from reef metabolism to boundary layer carbonate chemistry. These reefs experienced large ranges in pH (> 0.2 amplitude) each day, similar to the magnitude of 'acidification' expected over the next century. Daily benthic pH, pCO2, and aragonite saturation state (Ωaragonite) were contrasted with seasonal threshold values estimated from open ocean climatological data extrapolated at each island to determine relative inter-island feedbacks. Diurnal amplitude in pH, pCO2, and Ωaragonite at each island was dependent upon the resident species assemblage of the benthos and was particularly reliant upon the biomass, productivity, and calcification rate of Halimeda. Net primary productivity of fleshy algae (algal turfs and Lobophora spp.) predominated on degraded, inhabited islands where net community calcification was negligible. In contrast, the chemistry over reefs on 'pristine', uninhabited islands was driven largely by net calcification of calcareous algae and stony corals. Knowledge about species specific physiological rates and relative abundances of key taxa whose metabolism significantly alters carbonate chemistry may give insight to the ability for a reef to buffer against or exacerbate ocean acidification.
NASA Astrophysics Data System (ADS)
Sato, Yui; Bell, Sara C.; Nichols, Cassandra; Fry, Kent; Menéndez, Patricia; Bourne, David G.
2018-06-01
Coral recovery (the restoration of abundance and composition of coral communities) after disturbance is a key process that determines the resilience of reef ecosystems. To understand the mechanisms underlying the recovery process of coral communities, colony abundance and size distribution were followed on reefs around Pelorus Island, located in the inshore central region of the Great Barrier Reef, following a severe tropical cyclone in 2011 that caused dramatic loss of coral communities. Permanent quadrats (600 m2) were monitored biannually between 2012 and 2016, and individual coral colonies were counted, sized and categorized into morphological types. The abundance of coral recruits and coral cover were also examined using permanent quadrats and random line intercept transects, respectively. The number of colonies in the smallest size class (4-10 cm) increased substantially during the study period, driving the recovery of coral populations. The total number of coral colonies 5 yr post-cyclone reached between 73 and 122% of pre-cyclone levels though coral cover remained between 16 and 31% of pre-cyclone levels, due to the dominance of small coral colonies in the recovering communities. Temporal transitions of coral demography (i.e., colony-size distributions) illustrated that the number of recently established coral populations overtook communities of surviving colonies. Coral recruits (< 4 cm in size) also showed increasing patterns in abundance over the study period, underscoring the importance of larval supply in coral recovery. A shift in morphological composition of coral communities was also observed, with the relative abundance of encrusting corals reduced post-cyclone in contrast to their dominance prior to the disturbance. This study identifies the fine-scale processes involved in the initial recovery of coral reefs, providing insights into the dynamics of coral demography that are essential for determining coral reef resilience following major disturbance.
Simulation and Measurement of Medium-Frequency Signals Coupling From a Line to a Loop Antenna
Damiano, Nicholas W.; Li, Jingcheng; Zhou, Chenming; Brocker, Donovan E.; Qin, Yifeng; Werner, Douglas H.; Werner, Pingjuan L.
2016-01-01
The underground-mining environment can affect radio-signal propagation in various ways. Understanding these effects is especially critical in evaluating communications systems used during normal mining operations and during mine emergencies. One of these types of communications systems relies on medium-frequency (MF) radio frequencies. This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating MF coupling between a transmission line (TL) and a loop antenna in an underground coal mine. Two different types of measurements were completed: 1) line-current distribution and 2) line-to-antenna coupling. Measurements were taken underground in an experimental coal mine and on a specially designed surface test area. The results of these tests are characterized by current along a TL and voltage induced in the loop from a line. This paper concludes with a discussion of issues for MF TLs. These include electromagnetic fields at the ends of the TL, connection of the ends of the TL, the effect of other conductors underground, and the proximity of coal or earth. These results could help operators by providing examples of these challenges that may be experienced underground and a method by which to measure voltage induced by a line. PMID:27784954
NASA Technical Reports Server (NTRS)
Gary, G. A.; Moore, R. L.; Porter, J. G.; Falconer, D. A.
1999-01-01
We report further results on the magnetic origins of coronal heating found from registering coronal images with photospheric vector magnetograms. For two complementary active regions, we use computed potential field lines to examine the global non-potentiality of bright extended coronal loops and the three-dimensional structure of the magnetic field at their feet, and assess the role of these magnetic conditions in the strong coronal heating in these loops. The two active regions are complementary, in that one is globally potential and the other is globally nonpotential, while each is predominantly bipolar, and each has an island of included polarity in its trailing polarity domain. We find the following: (1) The brightest main-arch loops of the globally potential active region are brighter than the brightest main- arch loops of the globally strongly nonpotential active region. (2) In each active region, only a few of the mainarch magnetic loops are strongly heated, and these are all rooted near the island. (3) The end of each main-arch bright loop apparently bifurcates above the island, so that it embraces the island and the magnetic null above the island. (4) At any one time, there are other main-arch magnetic loops that embrace the island in the same manner as do the bright loops but that are not selected for strong coronal heating. (5) There is continual microflaring in sheared core fields around the island, but the main-arch bright loops show little response to these microflares. From these observational and modeling results we draw the following conclusions: (1) The heating of the main-arch bright loops arises mainly from conditions at the island end of these loops and not from their global non-potentiality. (2) There is, at most, only a loose coupling between the coronal heating in the bright loops of the main arch and the coronal heating in the sheared core fields at their feet, although in both the heating is driven by conditions/events in and around the island. (3) The main-arch bright loops are likely to be heated via reconnection driven at the magnetic null over the island. The details of how and where (along the null line) the reconnection is driven determine which of the split-end loops are selected for strong heating. (4) The null does not appear to be directly involved in the heating of the sheared core fields or in the heating of an extended loop rooted in the island. Rather, these all appear to be heated by microflares in the sheared core field.
Mass and energy supply of a cool coronal loop near its apex
NASA Astrophysics Data System (ADS)
Yan, Limei; Peter, Hardi; He, Jiansen; Xia, Lidong; Wang, Linghua
2018-03-01
Context. Different models for the heating of solar corona assume or predict different locations of the energy input: concentrated at the footpoints, at the apex, or uniformly distributed. The brightening of a loop could be due to the increase in electron density ne, the temperature T, or a mixture of both. Aim. We investigate possible reasons for the brightening of a cool loop at transition region temperatures through imaging and spectral observation. Methods: We observed a loop with the Interface Region Imaging Spectrograph (IRIS) and used the slit-jaw images together with spectra taken at a fixed slit position to study the evolution of plasma properties in and below the loop. We used spectra of Si IV, which forms at around 80 000 K in equilibrium, to identify plasma motions and derive electron densities from the ratio of inter-combination lines of O IV. Additional observations from the Solar Dynamics Observatory (SDO) were employed to study the response at coronal temperatures (Atmospheric Imaging Assembly, AIA) and to investigate the surface magnetic field below the loop (Helioseismic and Magnetic Imager, HMI). Results: The loop first appears at transition region temperatures and later also at coronal temperatures, indicating a heating of the plasma in the loop. The appearance of hot plasma in the loop coincides with a possible accelerating upflow seen in Si IV, with the Doppler velocity shifting continuously from -70 km s-1 to -265 km s-1. The 3D magnetic field lines extrapolated from the HMI magnetogram indicate possible magnetic reconnection between small-scale magnetic flux tubes below or near the loop apex. At the same time, an additional intensity enhancement near the loop apex is visible in the IRIS slit-jaw images at 1400 Å. These observations suggest that the loop is probably heated by the interaction between the loop and the upflows, which are accelerated by the magnetic reconnection between small-scale magnetic flux tubes at lower altitudes. Before and after the possible heating phase, the intensity changes in the optically thin (Si IV) and optical thick line (C II) are mainly contributed by the density variation without significant heating. Conclusions: We therefore provide evidence for the heating of an envelope loop that is affected by accelerating upflows, which are probably launched by magnetic reconnection between small-scale magnetic flux tubes underneath the envelope loop. This study emphasizes that in the complex upper atmosphere of the Sun, the dynamics of the 3D coupled magnetic field and flow field plays a key role in thermalizing 1D structures such as coronal loops. An animation associated to Fig. 1 is available at http://https://www.aanda.org
NASA Astrophysics Data System (ADS)
Posada-Ramírez, B.; Durán-Sánchez, M.; Álvarez-Tamayo, R. I.; Ibarra-Escamilla, B.; Hernández-Arriaga, M. V.; Sánchez-de-la-Llave, D.; Kuzin, E. A.
2017-08-01
We propose an all-fiber Tm-doped fiber laser with a tunable and narrow laser line generated in a wavelength region of 2 µm. A single laser line with a linewidth below 0.05 nm, tunable in a wavelength range of 44.25 nm, is obtained. The laser linewidth and the discrete wavelength tuning range depend on the characteristics of the two fiber optical loop mirrors with high birefringence in the loop that forms the cavity. Dual-wavelength laser operation is also observed at tuning range limits with a wavelength separation of 47 nm. Alternate wavelength switching is also observed.
How many fish? Comparison of two underwater visual sampling methods for monitoring fish communities
Sini, Maria; Vatikiotis, Konstantinos; Katsoupis, Christos
2018-01-01
Background Underwater visual surveys (UVSs) for monitoring fish communities are preferred over fishing surveys in certain habitats, such as rocky or coral reefs and seagrass beds and are the standard monitoring tool in many cases, especially in protected areas. However, despite their wide application there are potential biases, mainly due to imperfect detectability and the behavioral responses of fish to the observers. Methods The performance of two methods of UVSs were compared to test whether they give similar results in terms of fish population density, occupancy, species richness, and community composition. Distance sampling (line transects) and plot sampling (strip transects) were conducted at 31 rocky reef sites in the Aegean Sea (Greece) using SCUBA diving. Results Line transects generated significantly higher values of occupancy, species richness, and total fish density compared to strip transects. For most species, density estimates differed significantly between the two sampling methods. For secretive species and species avoiding the observers, the line transect method yielded higher estimates, as it accounted for imperfect detectability and utilized a larger survey area compared to the strip transect method. On the other hand, large-scale spatial patterns of species composition were similar for both methods. Discussion Overall, both methods presented a number of advantages and limitations, which should be considered in survey design. Line transects appear to be more suitable for surveying secretive species, while strip transects should be preferred at high fish densities and for species of high mobility. PMID:29942703
NASA Astrophysics Data System (ADS)
Jernsletten, J. A.
2004-05-01
INTRODUCTION: To evaluate the appropriateness of TEM in mapping deep groundwater tables (in Mars analog environmnets), a field study was carried out in the desert ~30 miles SW of Tucson, Arizona. The study was also designed to observe effects of powerline noise on TEM data. The clay-rich soil in the area is quite conductive. The study consisted of 40 in-loop TEM stations, divided into 3 lines, for 4 line-km of data. The survey was carried out by a crew of one person, with square Tx wire loops 100 m on a side, and a ferrite-core magnetic coil Rx antenna in the center of each Tx loop. Maximum useful depth of investigation achieved was ~600 m. TEM DATA: The field area is surrounded by powerlines on all 4 sides: Line 1 has the outside of the first Tx loop under the powerline to the West; Line 2 starts with the powerline to the North passing above just inside its first Tx loop, and ends with the outside of the last station's transmitter loop ~20 m shy of the powerline to the South; finally, Line 3 starts ~50 m East of the powerline to the West, and runs parallel to the powerline to the South along its entire length, at a separation distance of ~70 m. Line 3 was placed largely in an effort to obeserve powerline noise. The decay curve for the first station on Line 1(Line 1/Station 50) is raised above the other curves from Line 1. This is due to the charge (noise) from the adjacent powerline, which is at a distance of ~50 m from the Rx coil. In effect, the transient decay is recorded as being slower than it would be without the presence of the powerline. This also artficially lowers the apparent resistivity, readily observed in Line 1/Station 50 data. These effects are present to a lesser extent (lower magnitude noise) in the data from Line1/Station 150, the second station on Line 1. On the smooth-model inversion cross-section of the data from Line 1, the effects of the powerline noise appears as a pulling up of the low-resistivity water table contact towards the surface under the first two stations. Line 2/Station 50 data shows the same artificially slow decay and lowered apparent resistivity, compare to Line1/Station 50. Lower magnitude noise in Line 2/Station 150 data compares to Line 1 data. On the cross-section the effect is again a pulling up of the low-resistivity water table. The effects of the powerline noise on Line 2/Station 1550 data (last station) is mostly reflected in the fact that this data runs into noise at an earlier decay time than the data from other stations on Line 2. The last two stations do show shallower depths of investigation than the bulk of Line 2. Data from Line 3 uniformly runs into noise at earlier decay times than Line 1 and Line 2 data. Line 3 data achieves shallower depths of investigation than those possible along Line 1 and Line 2, and the water table contact is modeled at an artificially shallower than real depth along Line 3. Both of these effects are observable on the resistivity cross-section of Line 3 data. CONCLUSIONS: Line 1 and Line 2 observations are in good agreement. Effects observed in raw data include artifically slow decay and correspondingly low apparent resisitvities. The powerline noise lowers signal to noise ratios and depths of investigation. An artificial pulling up of the low-resistivity water table towards the surface is observed under affected stations in model cross-sections. There are a few ways in which to deal with this sort of noise in practical terms: remove noisy data at the end of each decay curve; throw out data from affected stations; keep data from affected stations, but be keenly aware of noise source locations and their effects on the data; and if at all possible, record data ~200+ m from any powerline noise source.
Cool transition region loops observed by the Interface Region Imaging Spectrograph
NASA Astrophysics Data System (ADS)
Huang, Z.; Xia, L.; Li, B.; Madjarska, M. S.
2015-12-01
An important class of loops in the solar atmosphere, cool transition region loops, have received little attention mainly due to instrumental limitations. We analyze a cluster of these loops in the on-disk active region NOAA 11934 recorded in a Si IV 1402.8 Å spectral raster and 1400Å slit-jaw (SJ) images taken by the Interface Region Imaging Spectrograph. We divide these loops into three groups and study their dynamics, evolution and interaction.The first group comprises geometrically relatively stable loops, which are finely scaled with 382~626 km cross-sections. Siphon flows in these loops are suggested by the Doppler velocities gradually changing from -10 km/s (blue-shifts) in one end to 20 km/s (red-shifts) in the other. Nonthermal velocities from 15 to 25 km/s were determined. The obtained physical properties suggest that these loops are impulsively heated by magnetic reconnection occurring at the blue-shifted footpoints where magnetic cancellation with a rate of 1015 Mx/s is found. The released magnetic energy is redistributed by the siphon flows. The second group corresponds to two active footpoints rooted in mixed-magnetic-polarity regions. Magnetic reconnection in both footpoints is suggested by explosive-event line profiles with enhanced wings up to 200 km/s and magnetic cancellation with a rate of ~1015 Mx/s. In the third group, an interaction between two cool loop systems is observed. Mixed-magnetic polarities are seen in their conjunction area where explosive-event line profiles and magnetic cancellation with a rate of 3×1015 Mx/s are found. This is a clear indication that magnetic reconnection occurs between these two loop systems. Our observations suggest that the cool transition region loops are heated impulsively most likely by sequences of magnetic reconnection events.
Cool Transition Region Loops Observed by the Interface Region Imaging Spectrograph
NASA Astrophysics Data System (ADS)
Huang, Zhenghua; Xia, Lidong; Li, Bo; Madjarska, Maria S.
2015-09-01
We report on the first Interface Region Imaging Spectrograph (IRIS) study of cool transition region loops, a class of loops that has received little attention in the literature. A cluster of such loops was observed on the solar disk in active region NOAA11934, in the Si iv 1402.8 Å spectral raster and 1400 Å slit-jaw images. We divide the loops into three groups and study their dynamics. The first group comprises relatively stable loops, with 382-626 km cross-sections. Observed Doppler velocities are suggestive of siphon flows, gradually changing from -10 km s-1 at one end to 20 km s-1 at the other end of the loops. Nonthermal velocities of 15 ˜ 25 km s-1 were determined. Magnetic cancellation with a rate of 1015 Mx s-1 is found at the blueshifted footpoints. These physical properties suggest that these loops are impulsively heated by magnetic reconnection, and the siphon flows play an important role in the energy redistribution. The second group corresponds to two footpoints rooted in mixed-magnetic-polarity regions, where magnetic cancellation with a rate of 1015 Mx s-1 and explosive-event line profiles with enhanced wings of up to 200 km s-1 were observed. In the third group, interaction between two cool loop systems is observed. Evidence for magnetic reconnection between the two loop systems is reflected in the explosive-event line profiles and magnetic cancellation with a rate of 3× {10}15 Mx s-1 observed in the corresponding area. The IRIS has provided opportunity for in-depth investigations of cool transition region loops. Further numerical experiments are crucial for understanding their physics and their roles in the coronal heating processes.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Antolin, P.; Moortel, I. De; Doorsselaere, T. Van
Magnetohydrodynamic (MHD) waves permeate the solar atmosphere and constitute potential coronal heating agents. Yet, the waves detected so far may be but a small subset of the true existing wave power. Detection is limited by instrumental constraints but also by wave processes that localize the wave power in undetectable spatial scales. In this study, we conduct 3D MHD simulations and forward modeling of standing transverse MHD waves in coronal loops with uniform and non-uniform temperature variation in the perpendicular cross-section. The observed signatures are largely dominated by the combination of the Kelvin–Helmholtz instability (KHI), resonant absorption, and phase mixing. Inmore » the presence of a cross-loop temperature gradient, we find that emission lines sensitive to the loop core catch different signatures compared to those that are more sensitive to the loop boundary and the surrounding corona, leading to an out-of-phase intensity and Doppler velocity modulation produced by KHI mixing. In all of the considered models, common signatures include an intensity and loop width modulation at half the kink period, a fine strand-like structure, a characteristic arrow-shaped structure in the Doppler maps, and overall line broadening in time but particularly at the loop edges. For our model, most of these features can be captured with a spatial resolution of 0.″33 and a spectral resolution of 25 km s{sup −1}, although we do obtain severe over-estimation of the line width. Resonant absorption leads to a significant decrease of the observed kinetic energy from Doppler motions over time, which is not recovered by a corresponding increase in the line width from phase mixing and KHI motions. We estimate this hidden wave energy to be a factor of 5–10 of the observed value.« less
2016-09-15
A series of active regions stretched along the right side of the sun exhibited a wide variety of loops cascading above them (Sept. 12-14, 2016). The active region near the center has tightly coiled loops, while the region rotating over the right edge has some elongated and some very stretched loops above it. The loops are actually charged particles spiraling along magnetic field lines, observed here in a wavelength of extreme ultraviolet light. Near the middle of the video the Earth quickly passes in front of a portion of the sun as viewed by SDO. http://photojournal.jpl.nasa.gov/catalog/PIA16997
FORWARD MODELING OF STANDING KINK MODES IN CORONAL LOOPS. I. SYNTHETIC VIEWS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yuan, Ding; Doorsselaere, Tom Van, E-mail: DYuan2@uclan.ac.uk
2016-04-15
Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this study, we synthesize the Fe ix λ171.073 Å emission of a coronal loop supporting a standing kink MHD mode. The kink MHD wave solution of a plasma cylinder is mapped into a semi-torus structure to simulate a curved coronal loop. We decompose the solution into a quasi-rigid kink motion and a quadrupole term, which dominate the plasma inside and outside of the flux tube, respectively.more » At the loop edges, the line of sight integrates relatively more ambient plasma, and the background emission becomes significant. The plasma motion associated with the quadrupole term causes spectral line broadening and emission suppression. The periodic intensity suppression will modulate the integrated intensity and the effective loop width, which both exhibit oscillatory variations at half of the kink period. The quadrupole term can be directly observed as a pendular motion at the front view.« less
Evidence for siphon flows with shocks in solar magnetic flux tubes
NASA Technical Reports Server (NTRS)
Degenhardt, D.; Solanki, S. K.; Montesinos, B.; Thomas, J. H.
1993-01-01
We synthesize profiles of the infrared line Fe I 15648.5 A (g = 3) for a recently developed theoretical model of siphon flows along photospheric magnetic loops. The synthesized line profiles are compared with the observations from which Rueedi et al. (1992) deduced the presence of such flows across the neutral line of an active region plage. This comparison supports the interpretation of Rueedi et al. (1992). It also suggests that the average footpoint separation of the observed loops carrying the siphon flow is 8-15 sec and that the siphon flow experiences a standing tube shock in the downstream leg near the top of the arch.
Environmental Assessment - Demolish 934 of Grand Forks Air Force Base
2006-03-01
r- line ’at th,-- above. described locnticn, it i .s hereby u :jderst,omdA that , stk-LdeterMination shall cc :>>titutu an P,- ., AAwiment1i reef ...office of the Clerk of District Court of Cass County, at Fargo, North Dakota, and to serve a golden corral All Management Positions • Voted #1 Sales in
33 CFR 110.190 - Tortugas Harbor, in vicinity of Garden Key, Dry Tortugas, Fla.
Code of Federal Regulations, 2013 CFR
2013-07-01
... Garden Key, Dry Tortugas, Fla. 110.190 Section 110.190 Navigation and Navigable Waters COAST GUARD..., in vicinity of Garden Key, Dry Tortugas, Fla. (a) The anchorage grounds. All of Bird Key Harbor, southwest of Garden Key, bounded by the surrounding reefs and shoals and, on the northeast, by a line...
33 CFR 110.190 - Tortugas Harbor, in vicinity of Garden Key, Dry Tortugas, Fla.
Code of Federal Regulations, 2012 CFR
2012-07-01
... Garden Key, Dry Tortugas, Fla. 110.190 Section 110.190 Navigation and Navigable Waters COAST GUARD..., in vicinity of Garden Key, Dry Tortugas, Fla. (a) The anchorage grounds. All of Bird Key Harbor, southwest of Garden Key, bounded by the surrounding reefs and shoals and, on the northeast, by a line...
33 CFR 110.190 - Tortugas Harbor, in vicinity of Garden Key, Dry Tortugas, Fla.
Code of Federal Regulations, 2011 CFR
2011-07-01
... Garden Key, Dry Tortugas, Fla. 110.190 Section 110.190 Navigation and Navigable Waters COAST GUARD..., in vicinity of Garden Key, Dry Tortugas, Fla. (a) The anchorage grounds. All of Bird Key Harbor, southwest of Garden Key, bounded by the surrounding reefs and shoals and, on the northeast, by a line...
33 CFR 110.190 - Tortugas Harbor, in vicinity of Garden Key, Dry Tortugas, Fla.
Code of Federal Regulations, 2010 CFR
2010-07-01
... Garden Key, Dry Tortugas, Fla. 110.190 Section 110.190 Navigation and Navigable Waters COAST GUARD..., in vicinity of Garden Key, Dry Tortugas, Fla. (a) The anchorage grounds. All of Bird Key Harbor, southwest of Garden Key, bounded by the surrounding reefs and shoals and, on the northeast, by a line...
33 CFR 110.190 - Tortugas Harbor, in vicinity of Garden Key, Dry Tortugas, Fla.
Code of Federal Regulations, 2014 CFR
2014-07-01
... Garden Key, Dry Tortugas, Fla. 110.190 Section 110.190 Navigation and Navigable Waters COAST GUARD..., in vicinity of Garden Key, Dry Tortugas, Fla. (a) The anchorage grounds. All of Bird Key Harbor, southwest of Garden Key, bounded by the surrounding reefs and shoals and, on the northeast, by a line...
System having unmodulated flux locked loop for measuring magnetic fields
Ganther, Jr., Kenneth R.; Snapp, Lowell D [Blue Springs, MO
2006-08-15
A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.
Proposed test protocol for video imaging detection at intersection stop lines.
DOT National Transportation Integrated Search
2010-08-01
Test protocols for non-loop detectors have often required comparing the performance : attributes of these detectors with those of loops or other point detectors, or to manual counts. : However, that comparison is not always appropriate for a variety ...
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gosain, S., E-mail: sgosain@nso.edu; Udaipur Solar Observatory, P.O. Box 198, Dewali, Udaipur, Rajasthan 313001
2012-04-10
We use high-resolution Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly observations to study the evolution of the coronal loops in a flaring solar active region, NOAA 11158. We identify three distinct phases of the coronal loop dynamics during this event: (1) slow-rise phase: slow rising motion of the loop-tops prior to the flare in response to the slow rise of the underlying flux rope; (2) collapse phase: sudden contraction of the loop-tops, with the lower loops collapsing earlier than the higher loops; and (3) oscillation phase: the loops exhibit global kink oscillations after the collapse phase at different periods, with themore » period decreasing with the decreasing height of the loops. The period of these loop oscillations is used to estimate the field strength in the coronal loops. Furthermore, we also use SDO/Helioseismic and Magnetic Imager (HMI) observations to study the photospheric changes close to the polarity inversion line (PIL). The longitudinal magnetograms show a stepwise permanent decrease in the magnetic flux after the flare over a coherent patch along the PIL. Furthermore, we examine the HMI Stokes I, Q, U, V profiles over this patch and find that the Stokes-V signal systematically decreases while the Stokes-Q and U signals increase after the flare. These observations suggest that close to the PIL the field configuration became more horizontal after the flare. We also use HMI vector magnetic field observations to quantify the changes in the field inclination angle and find an inward collapse of the field lines toward the PIL by {approx}10 Degree-Sign . These observations are consistent with the 'coronal implosion' scenario and its predictions about flare-related photospheric field changes.« less
Huang, Yongmei; Deng, Chao; Ren, Wei; Wu, Qiongyan
2017-01-01
In the CCD-based fine tracking optical system (FTOS), the whole disturbance suppression ability (DSA) is the product of the inner loop and outer position loop. Traditionally, high sampling fiber-optic gyroscopes (FOGs) are added to the platform to stabilize the line-of-sight (LOS). However, because of the FOGs’ high cost and relatively big volume relative to the back narrow space of small rotating mirrors, we attempt in this work to utilize a cheaper and smaller micro-electro-mechanical system (MEMS) accelerometer to build the inner loop, replacing the FOG. Unfortunately, since accelerometers are susceptible to the low-frequency noise, according to the classical way of using accelerometers, the crucial low-frequency DSA of the system is insufficient. To solve this problem, in this paper, we propose an approach based on MEMS accelerometers combining disturbance observer (DOB) with triple-loop control (TLC) in which the composite velocity loop is built by acceleration integration and corrected by CCD. The DOB is firstly used to reform the platform, greatly improving the medium-frequency DSA. Then the composite velocity loop exchanges a part of medium-frequency performance for the low-frequency DSA. A detailed analysis and experiments verify the proposed method has a better DSA than the traditional way and could totally substitute FOG in the LOS stabilization. PMID:29149050
NASA Astrophysics Data System (ADS)
Polte, Patrick; Kotterba, Paul; Moll, Dorothee; von Nordheim, Lena
2017-02-01
General concepts of larval fish ecology in temperate oceans predominantly associate dispersal and survival to exogenous mechanisms such as passive drift along ocean currents. However, for tropical reef fish larvae and species in inland freshwater systems behavioural aspects of habitat selection are evidently important components of dispersal. This study is focused on larval Atlantic herring (Clupea harengus) distribution in a Baltic Sea retention area, free of lunar tides and directed current regimes, considered as a natural mesocosm. A Lorenz curve originally applied in socio-economics to describe demographic income distribution was adapted to a 20 year time-series of weekly larval herring distribution, revealing size-dependent spatial homogeneity. Additional quantitative sampling of distinct larval development stages across pelagic and littoral areas uncovered a loop in habitat use during larval ontogeny, revealing a key role of shallow littoral waters. With increasing rates of coastal change, our findings emphasize the importance of the littoral zone when considering reproduction of pelagic, ocean-going fish species; highlighting a need for more sensitive management of regional coastal zones.
Polte, Patrick; Kotterba, Paul; Moll, Dorothee; von Nordheim, Lena
2017-01-01
General concepts of larval fish ecology in temperate oceans predominantly associate dispersal and survival to exogenous mechanisms such as passive drift along ocean currents. However, for tropical reef fish larvae and species in inland freshwater systems behavioural aspects of habitat selection are evidently important components of dispersal. This study is focused on larval Atlantic herring (Clupea harengus) distribution in a Baltic Sea retention area, free of lunar tides and directed current regimes, considered as a natural mesocosm. A Lorenz curve originally applied in socio-economics to describe demographic income distribution was adapted to a 20 year time-series of weekly larval herring distribution, revealing size-dependent spatial homogeneity. Additional quantitative sampling of distinct larval development stages across pelagic and littoral areas uncovered a loop in habitat use during larval ontogeny, revealing a key role of shallow littoral waters. With increasing rates of coastal change, our findings emphasize the importance of the littoral zone when considering reproduction of pelagic, ocean-going fish species; highlighting a need for more sensitive management of regional coastal zones. PMID:28205543
Suppression of heating of coronal loops rooted in opposite polarity sunspot umbrae
NASA Astrophysics Data System (ADS)
Tiwari, Sanjiv K.; Thalmann, Julia K.; Moore, Ronald L.; Panesar, Navdeep; Winebarger, Amy R.
2016-05-01
EUV observations of active region (AR) coronae reveal the presence of loops at different temperatures. To understand the mechanisms that result in hotter or cooler loops, we study a typical bipolar AR, near solar disk center, which has moderate overall magnetic twist and at least one fully developed sunspot of each polarity. From AIA 193 and 94 A images we identify many clearly discernible coronal loops that connect plage or a sunspot of one polarity to an opposite-polarity plage region. The AIA 94 A images show dim regions in the umbrae of the spots. To see which coronal loops are rooted in a dim umbral area, we performed a non-linear force-free field (NLFFF) modeling using photospheric vector magnetic field measurements obtained with the HMI onboard SDO. After validation of the NLFFF model by comparison of calculated model field lines and observed loops in AIA 193 and 94, we specify the photospheric roots of the model field lines. The model field then shows the coronal magnetic loops that arch from the dim umbral areas of the opposite polarity sunspots. Because these coronal loops are not visible in any of the coronal EUV and X-ray images of the AR, we conclude they are the coolest loops in the AR. This result suggests that the loops connecting opposite polarity umbrae are the least heated because the field in umbrae is so strong that the convective braiding of the field is strongly suppressed.We hypothesize that the convective freedom at the feet of a coronal loop, together with the strength of the field in the body of the loop, determines the strength of the heating. In particular, we expect the hottest coronal loops to have one foot in an umbra and the other foot in opposite-polarity penumbra or plage (coronal moss), the areas of strong field in which convection is not as strongly suppressed as in umbra. Many transient, outstandingly bright, loops in the AIA 94 movie of the AR do have this expected rooting pattern. We will also present another example of AR in which we find a similar rooting pattern of coronal loops.
Detection of Heating Processes in Coronal Loops by Soft X-ray Spectroscopy
NASA Astrophysics Data System (ADS)
Kawate, Tomoko; Narukage, Noriyuki; Ishikawa, Shin-nosuke; Imada, Shinsuke
2017-08-01
Imaging and Spectroscopic observations in the soft X-ray band will open a new window of the heating/acceleration/transport processes in the solar corona. The soft X-ray spectrum between 0.5 and 10 keV consists of the electron thermal free-free continuum and hot coronal lines such as O VIII, Fe XVII, Mg XI, Si XVII. Intensity of free-free continuum emission is not affected by the population of ions, whereas line intensities especially from highly ionized species have a sensitivity of the timescale of ionization/recombination processes. Thus, spectroscopic observations of both continuum and line intensities have a capability of diagnostics of heating/cooling timescales. We perform a 1D hydrodynamic simulation coupled with the time-dependent ionization, and calculate continuum and line intensities under different heat input conditions in a coronal loop. We also examine the differential emission measure of the coronal loop from the time-integrated soft x-ray spectra. As a result, line intensity shows a departure from the ionization equilibrium and shows different responses depending on the frequency of the heat input. Solar soft X-ray spectroscopic imager will be mounted in the sounding rocket experiment of the Focusing Optics X-ray Solar Imager (FOXSI). This observation will deepen our understanding of heating processes to solve the “coronal heating problem”.
The NST observation of a small loop eruption in He I D3 line on 2016 May 30
NASA Astrophysics Data System (ADS)
Kim, Yeon-Han; Xu, Yan; Bong, Su-Chan; Lim, Eunkyung; Yang, Heesu; Park, Young-Deuk; Yurchyshyn, Vasyl B.; Ahn, Kwangsu; Goode, Philip R.
2017-08-01
Since the He I D3 line has a unique response to a flare impact on the low solar atmosphere, it can be a powerful diagnostic tool for energy transport processes. In order to obtain comprehensive data sets for studying solar flare activities in D3 spectral line, we performed observations for several days using the 1.6m New Solar Telescope of Big Bear Solar Observatory (BBSO) in 2015 and 2016, equipped with the He I D3 filter, the photospheric broadband filter, and Near IR imaging spectrograph (NIRIS). On 2016 May 30, we observed a small loop eruption in He I D3 images associated with a B class brightening, which is occurred around 17:10 UT in a small active region, and dynamic variations of photospheric features in G-band images. Accordingly, the cause of the loop eruption can be magnetic reconnection driven by photospheric plasma motions. In this presentation, we will give the observation results and the interpretation.
Video on phone lines: technology and applications
NASA Astrophysics Data System (ADS)
Hsing, T. Russell
1996-03-01
Recent advances in communications signal processing and VLSI technology are fostering tremendous interest in transmitting high-speed digital data over ordinary telephone lines at bit rates substantially above the ISDN Basic Access rate (144 Kbit/s). Two new technologies, high-bit-rate digital subscriber lines and asymmetric digital subscriber lines promise transmission over most of the embedded loop plant at 1.544 Mbit/s and beyond. Stimulated by these research promises and rapid advances on video coding techniques and the standards activity, information networks around the globe are now exploring possible business opportunities of offering quality video services (such as distant learning, telemedicine, and telecommuting etc.) through this high-speed digital transport capability in the copper loop plant. Visual communications for residential customers have become more feasible than ever both technically and economically.
Damage structures in fission-neutron irradiated Ni-based alloys at high temperatures
NASA Astrophysics Data System (ADS)
Yamakawa, K.; Shimomura, Y.
1999-01-01
The defects formed in Ni based (Ni-Si, Ni-Cu and Ni-Fe) alloys which were irradiated with fission-neutrons were examined by electron microscopy. Irradiations were carried out at 473 K and 573 K. In the 473 K irradiated specimens, a high density of large interstitial loops and small vacancy clusters with stacking fault tetrahedra (SFT) were observed. The number densities of these two types of defects did not strongly depend on the amount of solute atoms in each alloy. The density of the loops in Ni-Si alloys was much higher than those in Ni-Cu and Ni-Fe alloys, while the density of SFT only slightly depended on the kind of solute. Also, the size of the loops depended on the kinds and amounts of solute. In 573 K irradiated Ni-Cu specimens, a high density of dislocation lines developed during the growth of interstitial loops. In Ni-Si alloys, the number density and size of the interstitial loops changed as a function of the amount of solute. Voids were formed in Ni-Cu alloys but scarcely formed in Ni-Si alloys. The number density of voids was one hundredth of that of SFT observed in 473 K irradiated Ni-Cu alloys. Possible formation processes of interstitial loops, SFT dislocation lines and voids are discussed.
NASA Astrophysics Data System (ADS)
Tebbett, Sterling B.; Goatley, Christopher H. R.; Bellwood, David R.
2017-09-01
The lined bristletooth, Ctenochaetus striatus, and the brown surgeonfish, Acanthurus nigrofuscus, are among the most abundant surgeonfishes on Indo-Pacific coral reefs. Yet, the functional role of these species has been the focus of an ongoing debate lasting at least six decades. Specifically, to what extent are C. striatus herbivorous like the visually similar A. nigrofuscus? To address this question, we used natural feeding surfaces, covered with late successional stage reef-grown algal turfs, to examine turf algal removal by the two species. Surfaces exposed to C. striatus in laboratory experiments exhibited no significant reductions in turf length or area covered by turfing algae. In marked contrast, A. nigrofuscus reduced turf length by 51% and area covered by turfing algae by 15% in 1 h. The gut contents of specimens from the reef revealed that A. nigrofuscus predominantly ingests algae (the dominant item in 79.6-94.7% of gut content quadrats), while C. striatus ingests detritus and sediments (dominant in 99.6-100% of quadrats). Therefore, C. striatus ingests detritus and sediment, leaving mature algal turfs relatively intact, while A. nigrofuscus directly removes and ingests turf algae. The function of C. striatus differs from cropping herbivorous surgeonfishes such as A. nigrofuscus. On coral reefs, C. striatus brush detrital aggregates from algal turfs, removing microorganisms, organic detritus and inorganic sediment. Confusion over the functional role of C. striatus may stem from an inability to fit it into a single functional category.
NASA Astrophysics Data System (ADS)
Gupta, G. R.; Sarkar, Aveek; Tripathi, Durgesh
2018-04-01
Using the observations recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Interface Region Imaging Spectrograph (IRIS) and the Extreme-ultraviolet Imaging Spectrometer and X-Ray Telescope both on board Hinode, we present evidence of chromospheric evaporation in a coronal loop after the occurrence of two active region transient brightenings (ARTBs) at the two footpoints. The chromospheric evaporation started nearly simultaneously in all of the three hot channels of AIA 131, 94, and 335 Å and was observed to be temperature dependent, being fastest in the highest temperature channel. The whole loop became fully brightened following the ARTBs after ≈25 s in 131 Å, ≈40 s in 94 Å, and ≈6.5 minutes in 335 Å. The differential emission measurements at the two footpoints (i.e., of two ARTBs) and at the loop top suggest that the plasma attained a maximum temperature of ∼10 MK at all these locations. The spectroscopic observations from IRIS revealed the presence of redshifted emission of ∼20 km s‑1 in cooler lines like C II and Si IV during the ARTBs that was cotemporal with the evaporation flow at the footpoint of the loop. During the ARTBs, the line width of C II and Si IV increased nearly by a factor of two during the peak emission. Moreover, enhancement in the line width preceded that in the Doppler shift, which again preceded enhancement in the intensity. The observed results were qualitatively reproduced by 1D hydrodynamic simulations, where energy was deposited at both of the footpoints of a monolithic coronal loop that mimicked the ARTBs identified in the observations.
NASA Astrophysics Data System (ADS)
Shi, Zongyang; Liu, Lihua; Xiao, Pan; Geng, Zhi; Liu, Fubo; Fang, Guangyou
2018-02-01
An ungrounded loop in the shallow subsurface transient electromagnetic surveys has been studied as the transmission line model for early turn-off stage, which can accurately explicate the early turn-off current waveform inconsistency along the loop. In this paper, the Gauss-Legendre numerical integration method is proposed for the first time to simulate and analyze the transient electromagnetic (TEM) response considering the different early turn-off current waveforms along the loop. During the simulation, these integral node positions along the loop are firstly determined by solving these zero points of Legendre polynomial, then the turn-off current of each node position is simulated by using the transfer function of the transmission line. Finally, the total TEM response is calculated by using the Gauss-Legendre integral formula. In addition, the comparison and analysis between the results affected by the distributed parameters and that generated by lumped parameters are presented. It is found that the TEM responses agree well with each other after current is thoroughly switched off, while the transient responses in turn-off stage are completely different. It means that the position dependence of the early turn-off current should be introduced into the forward model during the early response data interpretation of the shallow TEM detection of the ungrounded loop. Furthermore, the TEM response simulations at four geometric symmetry points are made. It shows that early responses of different geometric symmetry points are also inconsistent. The research on the influence of turn-off current position dependence on the early response of geometric symmetry point is of great significance to guide the layout of the survey lines and the transmitter location.
Heating and cooling system for an on-board gas adsorbent storage vessel
Tamburello, David A.; Anton, Donald L.; Hardy, Bruce J.; Corgnale, Claudio
2017-06-20
In one aspect, a system for controlling the temperature within a gas adsorbent storage vessel of a vehicle may include an air conditioning system forming a continuous flow loop of heat exchange fluid that is cycled between a heated flow and a cooled flow. The system may also include at least one fluid by-pass line extending at least partially within the gas adsorbent storage vessel. The fluid by-pass line(s) may be configured to receive a by-pass flow including at least a portion of the heated flow or the cooled flow of the heat exchange fluid at one or more input locations and expel the by-pass flow back into the continuous flow loop at one or more output locations, wherein the by-pass flow is directed through the gas adsorbent storage vessel via the by-pass line(s) so as to adjust an internal temperature within the gas adsorbent storage vessel.
Marsden, J. Ellen; Binder, Thomas R.; Johnson, James; He, Ji; Dingledine, Natalie; Adams, Janice; Johnson, Nicholas S.; Buchinger, Tyler J.; Krueger, Charles C.
2016-01-01
Degradation of aquatic habitats has motivated construction and research on the use of artificial reefs to enhance production of fish populations. However, reefs are often poorly planned, reef design characteristics are not evaluated, and reef assessments are short-term. We constructed 29 reefs in Thunder Bay, Lake Huron, in 2010 and 2011 to mitigate for degradation of a putative lake trout spawning reef. Reefs were designed to evaluate lake trout preferences for height, orientation, and size, and were compared with two degraded natural reefs and a high-quality natural reef (East Reef). Eggs and fry were sampled on each reef for five years post-construction, and movements of 40 tagged lake trout were tracked during three spawning seasons using acoustic telemetry. Numbers of adults and spawning on the constructed reefs were initially low, but increased significantly over the five years, while remaining consistent on East Reef. Adult density, egg deposition, and fry catch were not related to reef height or orientation of the constructed reefs, but were related to reef size and adjacency to East Reef. Adult lake trout visited and spawned on all except the smallest constructed reefs. Of the metrics used to evaluate the reefs, acoustic telemetry produced the most valuable and consistent data, including fine-scale examination of lake trout movements relative to individual reefs. Telemetry data, supplemented with diver observations, identified several previously unknown natural spawning sites, including the high-use portions of East Reef. Reef construction has increased the capacity for fry production in Thunder Bay without apparently decreasing the use of the natural reef. Results of this project emphasize the importance of multi-year reef assessment, use of multiple assessment methods, and comparison of reef characteristics when developing artificial reef projects. Specific guidelines for construction of reefs focused on enhancing lake trout spawning are suggested.
New BCJ representations for one-loop amplitudes in gauge theories and gravity
NASA Astrophysics Data System (ADS)
He, Song; Schlotterer, Oliver; Zhang, Yong
2018-05-01
We explain a procedure to manifest the Bern-Carrasco-Johansson duality between color and kinematics in n-point one-loop amplitudes of a variety of supersymmetric gauge theories. Explicit amplitude representations are constructed through a systematic reorganization of the integrands in the Cachazo-He-Yuan formalism. Our construction holds for any nonzero number of supersymmetries and does not depend on the number of spacetime dimensions. The cancellations from supersymmetry multiplets in the loop as well as the resulting power counting of loop momenta is manifested along the lines of the corresponding superstring computations. The setup is used to derive the one-loop version of the Kawai-Lewellen-Tye formula for the loop integrands of gravitational amplitudes.
Evidence of suppressed heating of coronal loops rooted in opposite polarity sunspot umbrae
NASA Astrophysics Data System (ADS)
Tiwari, Sanjiv K.; Thalmann, Julia K.; Winebarger, Amy R.; Panesar, Navdeep K.; Moore, Ronald
2015-04-01
Observations of active region (AR) coronae in different EUV wavelengths reveal the presence of various loops at different temperatures. To understand the mechanisms that result in hotter or cooler loops, we study a typical bipolar AR, near solar disk center, which has moderate overall magnetic twist and at least one fully developed sunspot of each polarity. From AIA 193 and 94 A images we identify many clearly discernible coronal loops that connect opposite-polarity plage or a sunspot to a opposite-polarity plage region. The AIA 94 A images show dim regions in the umbrae of the spots. To see which coronal loops are rooted in a dim umbral area, we performed a non-linear force-free field (NLFFF) modeling using photospheric vector magnetic field measurements obtained with the Heliosesmic Magnetic Imager (HMI) onboard SDO. After validation of the NLFFF model by comparison of calculated model field lines and observed loops in AIA 193 and 94 A, we specify the photospheric roots of the model field lines. The model field then shows the coronal magnetic loops that arch from the dim umbral area of the positive-polarity sunspot to the dim umbral area of a negative-polarity sunspot. Because these coronal loops are not visible in any of the coronal EUV and X-ray images of the AR, we conclude they are the coolest loops in the AR. This result suggests that the loops connecting opposite polarity umbrae are the least heated because the field in umbrae is so strong that the convective braiding of the field is strongly suppressed.From this result, we further hypothesize that the convective freedom at the feet of a coronal loop, together with the strength of the field in the body of the loop, determines the strength of the heating. In particular, we expect the hottest coronal loops to have one foot in an umbra and the other foot in opposite-polarity penumbra or plage (coronal moss), the areas of strong field in which convection is not as strongly suppressed as in umbrae. Many transient, outstandingly bright, loops in the AIA 94 A movie of the AR do have this expected rooting pattern.
The rate of predation by fishes on hatchlings of the green turtle ( Chelonia mydas)
NASA Astrophysics Data System (ADS)
Gyuris, E.
1994-07-01
This study addresses the need for empirical data on the survival of sea turtle hatchlings after entry into the sea by (1) developing a method for measuring marine predation; (2) estimating predation rates while crossing the reef; and (3) investigating the effect of environmental variables on predation rates. Predation rates were quantified by following individual hatchlings, tethered by a 10m monofilament nylon line, as they swam from the water's edge towards the reef crest. Predation rates under particular combinations of environmental variables (tide, time of day, and moon phase) were measured in separate trials. Predation rates varied among trials from 0 to 85% with a mean of 31% (SE=2.5%). The simplest logistic regression model that explained variation in predation contained tide and moon phase as predictor variables. The results suggest that noctural emergence from the nest is a behavioral adaptation to minimize exposure to the heat of the day rather than a predator-escape mechanism. For the green turtle populations breeding in eastern Australia, most first year mortality is caused by predation while crossing the reef within the first hour of entering the sea.
Coronal Heating and the Magnetic Field in Solar Active Regions
NASA Astrophysics Data System (ADS)
Falconer, D. A.; Tiwari, S. K.; Winebarger, A. R.; Moore, R. L.
2017-12-01
A strong dependence of active-region (AR) coronal heating on the magnetic field is demonstrated by the strong correlation of AR X-ray luminosity with AR total magnetic flux (Fisher et al 1998 ApJ). AR X-ray luminosity is also correlated with AR length of strong-shear neutral line in the photospheric magnetic field (Falconer 1997). These two whole-AR magnetic parameters are also correlated with each other. From 150 ARs observed within 30 heliocentric degrees from disk center by AIA and HMI on SDO, using AR luminosity measured from the hot component of the AIA 94 Å band (Warren et al 2012, ApJ) near the time of each of 3600 measured HMI vector magnetograms of these ARs and a wide selection of whole-AR magnetic parameters from each vector magnetogram after it was deprojected to disk center, we find: (1) The single magnetic parameter having the strongest correlation with AR 94-hot luminosity is the length of strong-field neutral line. (2) The two-parameter combination having the strongest still-stronger correlation with AR 94-hot luminosity is a combination of AR total magnetic flux and AR neutral-line length weighted by the vertical-field gradient across the neutral line. We interpret these results to be consistent with the results of both Fisher et al (1998) and Falconer (1997), and with the correlation of AR coronal loop heating with loop field strength recently found by Tiwari et al (2017, ApJ Letters). Our interpretation is that, in addition to depending strongly on coronal loop field strength, AR coronal heating has a strong secondary positive dependence on the rate of flux cancelation at neutral lines at coronal loop feet. This work was funded by the Living With a Star Science and Heliophysics Guest Investigators programs of NASA's Heliophysics Division.
Tang, Tao; Tian, Jing; Zhong, Daijun; Fu, Chengyu
2016-06-25
A rate feed forward control-based sensor fusion is proposed to improve the closed-loop performance for a charge couple device (CCD) tracking loop. The target trajectory is recovered by combining line of sight (LOS) errors from the CCD and the angular rate from a fiber-optic gyroscope (FOG). A Kalman filter based on the Singer acceleration model utilizes the reconstructive target trajectory to estimate the target velocity. Different from classical feed forward control, additive feedback loops are inevitably added to the original control loops due to the fact some closed-loop information is used. The transfer function of the Kalman filter in the frequency domain is built for analyzing the closed loop stability. The bandwidth of the Kalman filter is the major factor affecting the control stability and close-loop performance. Both simulations and experiments are provided to demonstrate the benefits of the proposed algorithm.
B1 field-insensitive transformers for RF-safe transmission lines.
Krafft, Axel; Müller, Sven; Umathum, Reiner; Semmler, Wolfhard; Bock, Michael
2006-11-01
Integration of transformers into transmission lines suppresses radiofrequency (RF)-induced heating. New figure-of-eight-shaped transformer coils are compared to conventional loop transformer coils to assess their signal transmission properties and safety profile. The transmission properties of figure-of-eight-shaped transformers were measured and compared to transformers with loop coils. Experiments to quantify the effect of decoupling from the B1 field of the MR system were conducted. Temperature measurements were performed to demonstrate the effective reduction of RF-induced heating. The transformers were investigated during active tracking experiments. Coupling to the B1 field was reduced by 18 dB over conventional loop-shaped transformer coils. MR images showed a significantly reduced artifact for the figure-of-eight- shaped coils generated by local flip-angle amplification. Comparable transmission properties were seen for both transformer types. Temperature measurements showed a maximal temperature increase of 30 K/3.5 K for an unsegmented/segmented cable. With a segmented transmission line a robotic assistance system could be successfully localized using active tracking. The figure-of-eight-shaped transformer design reduces both RF field coupling with the MR system and artifact sizes. Anatomical structure close to the figure-of-eight-shaped transformer may be less obscured as with loop-shaped transformers if these transformers are integrated into e.g. intravascular catheters.
Magnetic activity in the Galactic Centre region - fast downflows along rising magnetic loops
NASA Astrophysics Data System (ADS)
Kakiuchi, Kensuke; Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Enokiya, Rei; Machida, Mami; Matsumoto, Ryoji
2018-06-01
We studied roles of the magnetic field on the gas dynamics in the Galactic bulge by a three-dimensional global magnetohydrodynamical simulation data, particularly focusing on vertical flows that are ubiquitously excited by magnetic activity. In local regions where the magnetic field is stronger, it is frequently seen that fast downflows slide along inclined magnetic field lines that are associated with buoyantly rising magnetic loops. The vertical velocity of these downflows reaches ˜100 km s-1 near the footpoint of the loops by the gravitational acceleration towards the Galactic plane. The two footpoints of rising magnetic loops are generally located at different radial locations and the field lines are deformed by the differential rotation. The angular momentum is transported along the field lines, and the radial force balance breaks down. As a result, a fast downflow is often observed only at the one footpoint located at the inner radial position. The fast downflow compresses the gas to form a dense region near the footpoint, which will be important in star formation afterwards. Furthermore, the horizontal components of the velocity are also fast near the footpoint because the downflow is accelerated along the magnetic sliding slope. As a result, the high-velocity flow creates various characteristic features in a simulated position-velocity diagram, depending on the viewing angle.
Work, Thierry M.; Aeby, Greta S.; Neal, Benjamin P.; Price, Nichole N.; Conklin, Eric; Pollock, Amanda
2018-01-01
In 2007, a phase shift from corals to corallimorpharians (CM) centered around a shipwreck was documented at Palmyra Atoll, Line Islands. Subsequent surveys revealed CM to be overgrowing the reef benthos, including corals and coralline algae, potentially placing coral ecosystems in the atoll at risk. This prompted the U.S. Fish and Wildlife Service, the lead management agency of the atoll, to remove the shipwreck. Subsequent surveys showed reductions in CM around the ship impact site. We explain patterns of spread of the CM in terms of both life history and local currents and show with a pilot study that pulverized bleach may be an effective tool to eradicate CM on a local scale. If applied strategically, particularly in heavily infested (> 66% cover) areas, active intervention such as this could be an effective management tool to reduce CM impact on localized areas and decrease colonization rate of remaining reefs. This is the first documentation of the response of an invasive cnidarian to shipwreck removal. While this was a singular event in Palmyra, the spatial and temporal patterns of this invasion and the eradications lessons described herein, are useful for anticipating and controlling similar situations elsewhere.
NASA Astrophysics Data System (ADS)
Maran, S. P.; Robinson, R. D.; Shore, S. N.; Brosius, J. W.; Carpenter, K. G.; Woodgate, B. E.; Linsky, J. L.; Brown, A.; Byrne, P. B.; Kundu, M. R.; White, S.; Brandt, J. C.; Shine, R. A.; Walter, F. M.
1994-02-01
We report on an observation of AU Mic taken with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The data consist of a rapid sequence of spectra covering the wavelength range 1345-1375 A with a spectral resolution of 10,000. The observations were originally intended to search for spectral variations during flares. No flares were detected during the 3.5 hr of monitoring. A method of reducing the noise while combining the individual spectra in the time series is described which resulted in the elimination of half of the noise while rejecting only a small fraction of the stellar signal. The resultant spectrum was of sufficient quality to allow the detection of emission lines with an integrated flux of 10-15 ergs/sq cm(sec) or greater. Lines of C I, O I, O V, Cl I, and Fe XXI were detected. This is the first indisputable detection of the 1354 A Fe XXI line, formed at T approximately = 107 K, on a star other than the Sun. The line was well resolved and displayed no significant bulk motions or profile asymmetry. From the upper limit on the observed line width, we derive an upper limit of 38 km/s for the turbulent velocity in the 107 K plasma. An upper limit is derived for the flux of the 1349 A Fe XII line, formed at T approximately = 1.3 x 106 K. These data are combined with contemporaneous GHRS and International Ultraviolet Explorer (IUE) data to derive the volume emission measure distribution of AU Mic over the temperature range 104-107 K. Models of coronal loops in hydrostatic equilibrium are consistent with the observed volume emission measures of the coronal lines. The fraction of the stellar surface covered by the footprints of the loops depends upon the loop length and is less than 14% for lengths smaller than the stellar radius. From the upper limit to the estimated width of the Fe XXI line profile we find that the we cannot rule out Alfven wave dissipation as a possible contributor to the required quiescent loop heating rate.
NASA Astrophysics Data System (ADS)
Tang, Tao; Cai, Huaxiang; Huang, Yongmei; Ren, Ge
2015-10-01
A feedforward control based on data fusion is proposed to enhance closed-loop performance. The target trajectory as the observed value of a Kalman filter is recovered by synthesizing line-of-sight error and angular position from the encoder. A Kalman filter based on a Singer acceleration model is employed to estimate the target velocity. In this control scheme, the control stability is influenced by the bandwidth of the Kalman filter and time misalignment. The transfer function of the Kalman filter in the frequency domain is built for analyzing the closed loop stability, which shows that the Kalman filter is the major factor that affects the control stability. The feedforward control proposed here is verified through simulations and experiments.
NASA Astrophysics Data System (ADS)
Duan, Aiying; Jiang, Chaowei; Hu, Qiang; Zhang, Huai; Gary, G. Allen; Wu, S. T.; Cao, Jinbin
2017-06-01
Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE-MHD-NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO/AIA. It is found that the CESE-MHD-NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ˜10°. This suggests that the CESE-MHD-NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (˜30°). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Duan, Aiying; Zhang, Huai; Jiang, Chaowei
Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE–MHD–NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from themore » region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO /AIA. It is found that the CESE–MHD–NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ∼10°. This suggests that the CESE–MHD–NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (∼30°). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.« less
Bathymetric distribution of foraminifera in Jamaican reef environments
DOE Office of Scientific and Technical Information (OSTI.GOV)
Martin, R.E.; Liddell, W.D.
1985-02-01
Recent foraminifera inhabiting Jamaican north-coast fringing reefs display variations in distributional patterns that are related to bathymetry and reef morphology. Sediment samples containing foraminifera were collected along a profile that traversed the back reef (depth 1-2 m), fore-reef terrace (3-15 m), fore-reef escarpment (15-27 m), fore-reef slope (30-55 m), and upper deep fore reef (70 m). Approximately 150 species distributed among 80 genera were identified from the samples. Preliminary analyses indicate that diversity values (S, H') are lowest on the fore-reef terrace (79, 3.0, respectively), increase similarly in back-reef and fore-reef escarpment and slope settings (93, 3.4), and are highestmore » on the deep fore reef (109, 3.7). Larger groupings (suborders) exhibit distinct bathymetric trends with miliolids occurring more commonly in back-reef (comprising 51% of the fauna) than in fore-reef (28%) zones, whereas agglutinated and planktonic species occur more commonly in deeper reef (> 15 m, 9% and 4%, respectively) than in shallower reef zones (< 15 m, 3%, and 0.5%, respectively). Among the more common species Amphistegina gibbosa (Rotolina) is much more abundant in fore-reef (3%) environments, and Sorites marginalis (Miliolina) occurs almost exclusively in the back reef, where it comprises 5.5% of the fauna. Q-mode cluster analysis, involving all species collected, enabled the delineation of back-reef, shallow fore-reef, and deeper fore-reef biofacies, also indicating the potential utility of foraminiferal distributions in detailed paleoenvironment interpretations of ancient reef settings.« less
The Duration of Energy Deposition on Unresolved Flaring Loops in the Solar Corona
NASA Astrophysics Data System (ADS)
Reep, Jeffrey W.; Polito, Vanessa; Warren, Harry P.; Crump, Nicholas A.
2018-04-01
Solar flares form and release energy across a large number of magnetic loops. The global parameters of flares, such as the total energy released, duration, physical size, etc., are routinely measured, and the hydrodynamics of a coronal loop subjected to intense heating have been extensively studied. It is not clear, however, how many loops comprise a flare, nor how the total energy is partitioned between them. In this work, we employ a hydrodynamic model to better understand the energy partition by synthesizing Si IV and Fe XXI line emission and comparing to observations of these lines with the Interface Region Imaging Spectrograph (IRIS). We find that the observed temporal evolution of the Doppler shifts holds important information on the heating duration. To demonstrate this, we first examine a single loop model, and find that the properties of chromospheric evaporation seen in Fe XXI can be reproduced by loops heated for long durations, while persistent redshifts seen in Si IV cannot be reproduced by any single loop model. We then examine a multithreaded model, assuming both a fixed heating duration on all loops and a distribution of heating durations. For a fixed heating duration, we find that durations of 100–200 s do a fair job of reproducing both the red- and blueshifts, while a distribution of durations, with a median of about 50–100 s, does a better job. Finally, we compare our simulations directly to observations of an M-class flare seen by IRIS, and find good agreement between the modeled and observed values given these constraints.
Role of Integrin-Beta 1 in Polycystic Kidney Disease
2011-04-01
characterized a novel cell line from human loop of Henle epithelium that can serve as a unique model to study medullary cystic kidney disease-2 (MCKD2) and...Therefore, we further characterized the TIRE131 clone to confirm their loop of Henle origin. Similarly to the loop of Henle epithelium , the...TIRE131 cells: 1) possessed a significant resistance to hyperosmotic growth conditions; 2) formed a functional epithelium with tight junction and
2010-02-16
field. Techniques utilizing this design use an open- loop control and no flow monitoring sensors are required. Conversely, reactive (or closed - loop ...and closed (dashed line) configuration. 38 closed configuration described above, the ambiguity in the critical limits of the transition...flow; a new vortex is then shed from the cavity leading edge, closing the feedback loop .[31] Open cavities with an L/D approximately greater than
Polar phase of superfluid 3He: Dirac lines in the parameter and momentum spaces
NASA Astrophysics Data System (ADS)
Volovik, G. E.
2018-03-01
The time reversal symmetric polar phase of the spin-triplet superfluid 3He has two types of Dirac nodal lines. In addition to the Dirac loop in the spectrum of the fermionic Bogoliubov quasiparticles in the momentum space (p x , p y , p z ), the spectrum of bosons (magnons) has Dirac loop in the 3D space of parameters-the components of magnetic field (H x , H y , H z ). The bosonic Dirac system lives on the border between the type-I and type-II.
Sweeping Arches and Loops [video
2014-07-10
Two active regions with their intense magnetic fields produced towering arches and spiraling coils of solar loops above them (June 29 - July 1, 2014) as they rotated into view. When viewed in extreme ultraviolet light, magnetic field lines are revealed by charged particles that travel along them. These active regions appear as dark sunspots when viewed in filtered light. Note the small blast in the upper of the two major active regions, followed by more coils of loops as the region reorganizes itself. The still was taken on June 30 at 10:33 UT. Credit: NASA/Solar Dynamics Observatory Two active regions with their intense magnetic fields produced towering arches and spiraling coils of solar loops above them (June 29 - July 1, 2014) as they rotated into view. When viewed in extreme ultraviolet light, magnetic field lines are revealed by charged particles that travel along them. These active regions appear as dark sunspots when viewed in filtered light. Note the small blast in the upper of the two major active regions, followed by more coils of loops as the region reorganizes itself. The still was taken on June 30 at 10:33 UT. Credit: Solar Dynamics Observatory/NASA.
Force-Free Magnetic Fields Calculated from Automated Tracing of Coronal Loops with AIA/SDO
NASA Astrophysics Data System (ADS)
Aschwanden, M. J.
2013-12-01
One of the most realistic magnetic field models of the solar corona is a nonlinear force-free field (NLFFF) solution. There exist about a dozen numeric codes that compute NLFFF solutions based on extrapolations of photospheric vector magnetograph data. However, since the photosphere and lower chromosphere is not force-free, a suitable correction has to be applied to the lower boundary condition. Despite of such "pre-processing" corrections, the resulting theoretical magnetic field lines deviate substantially from observed coronal loop geometries. - Here we developed an alternative method that fits an analytical NLFFF approximation to the observed geometry of coronal loops. The 2D coordinates of the geometry of coronal loop structures observed with AIA/SDO are traced with the "Oriented Coronal CUrved Loop Tracing" (OCCULT-2) code, an automated pattern recognition algorithm that has demonstrated the fidelity in loop tracing matching visual perception. A potential magnetic field solution is then derived from a line-of-sight magnetogram observed with HMI/SDO, and an analytical NLFFF approximation is then forward-fitted to the twisted geometry of coronal loops. We demonstrate the performance of this magnetic field modeling method for a number of solar active regions, before and after major flares observed with SDO. The difference of the NLFFF and the potential field energies allows us then to compute the free magnetic energy, which is an upper limit of the energy that is released during a solar flare.
Fine flow structures in the transition region small-scale loops
NASA Astrophysics Data System (ADS)
Yan, L.; Peter, H.; He, J.; Wei, Y.
2016-12-01
The observation and model have suggested that the transition region EUV emission from the quiet sun region is contributed by very small scale loops which have not been resolved. Recently, the observation from IRIS has revealed that this kind of small scale loops. Based on the high resolution spectral and imaging observation from IRIS, much more detail work needs to be done to reveal the fine flow features in this kind of loop to help us understand the loop heating. Here, we present a detail statistical study of the spatial and temporal evolution of Si IV line profiles of small scale loops and report the spectral features: there is a transition from blue (red) wing enhancement dominant to red (blue) wing enhancement dominant along the cross-section of the loop, which is independent of time. This feature appears as the loop appear and disappear as the loop un-visible. This is probably the signature of helical flow along the loop. The result suggests that the brightening of this kind of loop is probably due to the current dissipation heating in the twisted magnetic field flux tube.
How to share underground reservoirs
NASA Astrophysics Data System (ADS)
Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.
2012-10-01
Many resources, such as oil, gas, or water, are extracted from porous soils and their exploration is often shared among different companies or nations. We show that the effective shares can be obtained by invading the porous medium simultaneously with various fluids. Partitioning a volume in two parts requires one division surface while the simultaneous boundary between three parts consists of lines. We identify and characterize these lines, showing that they form a fractal set consisting of a single thread spanning the medium and a surrounding cloud of loops. While the spanning thread has fractal dimension 1.55 +/- 0.03, the set of all lines has dimension 1.69 +/- 0.02. The size distribution of the loops follows a power law and the evolution of the set of lines exhibits a tricritical point described by a crossover with a negative dimension at criticality.
Postglacial Fringing-Reef to Barrier-Reef conversion on Tahiti links Darwin's reef types
NASA Astrophysics Data System (ADS)
Blanchon, Paul; Granados-Corea, Marian; Abbey, Elizabeth; Braga, Juan C.; Braithwaite, Colin; Kennedy, David M.; Spencer, Tom; Webster, Jody M.; Woodroffe, Colin D.
2014-05-01
In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs then atolls. Yet historically no transition between reef types has been discovered and they are widely considered to develop independently from antecedent foundations during glacio-eustatic sea-level rise. Here we reconstruct reef development from cores recovered by IODP Expedition 310 to Tahiti, and show that a fringing reef retreated upslope during postglacial sea-level rise and transformed into a barrier reef when it encountered a Pleistocene reef-flat platform. The reef became stranded on the platform edge, creating a lagoon that isolated it from coastal sediment and facilitated a switch to a faster-growing coral assemblage dominated by acroporids. The switch increased the reef's accretion rate, allowing it to keep pace with rising sea level, and transform into a barrier reef. This retreat mechanism not only links Darwin's reef types, but explains the re-occupation of reefs during Pleistocene glacio-eustacy.
2003-01-01
These banana-shaped loops are part of a computer-generated snapshot of our sun's magnetic field. The solar magnetic-field lines loop through the sun's corona, break through the sun's surface, and cornect regions of magnetic activity, such as sunspots. This image --part of a magnetic-field study of the sun by NASA's Allen Gary -- shows the outer portion (skins) of interconnecting systems of hot (2 million degrees Kelvin) coronal loops within and between two active magnetic regions on opposite sides of the sun's equator. The diameter of these coronal loops at their foot points is approximately the same size as the Earth's radius (about 6,000 kilometers).
Self-generated morphology in lagoon reefs
Hamblin, Michael G.
2015-01-01
The three-dimensional form of a coral reef develops through interactions and feedbacks between its constituent organisms and their environment. Reef morphology therefore contains a potential wealth of ecological information, accessible if the relationships between morphology and ecology can be decoded. Traditionally, reef morphology has been attributed to external controls such as substrate topography or hydrodynamic influences. Little is known about inherent reef morphology in the absence of external control. Here we use reef growth simulations, based on observations in the cellular reefs of Western Australia’s Houtman Abrolhos Islands, to show that reef morphology is fundamentally determined by the mechanical behaviour of the reef-building organisms themselves—specifically their tendency to either remain in place or to collapse. Reef-building organisms that tend to remain in place, such as massive and encrusting corals or coralline algae, produce nodular reefs, whereas those that tend to collapse, such as branching Acropora, produce cellular reefs. The purest reef growth forms arise in sheltered lagoons dominated by a single type of reef builder, as in the branching Acropora-dominated lagoons of the Abrolhos. In these situations reef morphology can be considered a phenotype of the predominant reef building organism. The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images. More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef. PMID:26175962
Manikandan, B; Ravindran, J; Shrinivaasu, S; Marimuthu, N; Paramasivam, K
2014-10-01
Coral reef fishes are exploited without the knowledge of their sustainability and their possible effect in altering the community structure of a coral reef ecosystem. Alteration of the community structure could cause a decline in the health of coral reefs and its services. We documented the coral community structure, status of live corals and reef fish assemblages in Palk Bay at the reef fishing hotspots and its nearby reef area with minimum fishing pressure and compared it with a control reef area where reef fishing was banned for more than two decades. The comparison was based on the percent cover of different forms of live corals, their diversity and the density and diversity of reef fishes. The reef fish stock in the reef fishing hotspots and its neighbouring reef was lower by 61 and 38%, respectively compared to the control reef. The herbivore fish Scarus ghobban and Siganus javus were exploited at a rate of 250 and 105 kg month(-1) fishermen(-1), respectively, relatively high comparing the small reef area. Live and dead corals colonized by turf algae were predominant in both the reef fishing hotspots and its nearby coral ecosystems. The percent cover of healthy live corals and live corals colonized by turf algae was <10 and >80%, respectively, in the intensively fished coral ecosystems. The corals were less diverse and the massive Porites and Favia colonies were abundant in the intensive reef fishing sites. Results of this study suggest that the impact of reef fish exploitation was not solely restricted to the intensively fished reefs, but also to the nearby reefs which play a critical role in the resilience of degraded reef ecosystems.
Pakleza, Christophe; Cognet, Jean A. H.
2003-01-01
A new molecular modelling methodology is presented and shown to apply to all published solution structures of DNA hairpins with TTT in the loop. It is based on the theory of elasticity of thin rods and on the assumption that single-stranded B-DNA behaves as a continuous, unshearable, unstretchable and flexible thin rod. It requires four construction steps: (i) computation of the tri-dimensional trajectory of the elastic line, (ii) global deformation of single-stranded helical DNA onto the elastic line, (iii) optimisation of the nucleoside rotations about the elastic line, (iv) energy minimisation to restore backbone bond lengths and bond angles. This theoretical approach called ‘Biopolymer Chain Elasticity’ (BCE) is capable of reproducing the tri-dimensional course of the sugar–phosphate chain and, using NMR-derived distances, of reproducing models close to published solution structures. This is shown by computing three different types of distance criteria. The natural description provided by the elastic line and by the new parameter, Ω, which corresponds to the rotation angles of nucleosides about the elastic line, offers a considerable simplification of molecular modelling of hairpin loops. They can be varied independently from each other, since the global shape of the hairpin loop is preserved in all cases. PMID:12560506
Hot spine loops and the nature of a late-phase solar flare
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sun, Xudong; Todd Hoeksema, J.; Liu, Yang
2013-12-01
The fan-spine magnetic topology is believed to be responsible for many curious features in solar explosive events. A spine field line links distinct flux domains, but direct observation of such a feature has been rare. Here we report a unique event observed by the Solar Dynamic Observatory where a set of hot coronal loops (over 10 MK) connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggests that these loops are partly tracers of the evolving spine field line. Continuous slipping- and null-point-type reconnections were likely at work, energizing themore » loop plasma and transferring magnetic flux within and across the fan quasi-separatrix layer. We argue that the initial reconnection is of the 'breakout' type, which then transitioned to a more violent flare reconnection with an eruption from the fan dome. Significant magnetic field changes are expected and indeed ensued. This event also features an extreme-ultraviolet (EUV) late phase, i.e., a delayed secondary emission peak in warm EUV lines (about 2-7 MK). We show that this peak comes from the cooling of large post-reconnection loops beside and above the compact fan, a direct product of eruption in such topological settings. The long cooling time of the large arcades contributes to the long delay; additional heating may also be required. Our result demonstrates the critical nature of cross-scale magnetic coupling—topological change in a sub-system may lead to explosions on a much larger scale.« less
Great Barrier Reef, Queensland, Australia
NASA Technical Reports Server (NTRS)
1990-01-01
This detailed view of the Great Barrier Reef, Queensland, Australia (19.5S, 149.5E) shows several small patch reefs within the overall reef system. The Great Barrier Reef, largest in the world, comprises thousands of individual reefs of great variety and are closely monitored by marine ecologists. These reefs are about 6000 years old and sit on top of much older reefs. The most rapid coral growth occurs on the landward side of the reefs.
An approach toward the numerical evaluation of multi-loop Feynman diagrams
NASA Astrophysics Data System (ADS)
Passarino, Giampiero
2001-12-01
A scheme for systematically achieving accurate numerical evaluation of multi-loop Feynman diagrams is developed. This shows the feasibility of a project aimed to produce a complete calculation for two-loop predictions in the Standard Model. As a first step an algorithm, proposed by F.V. Tkachov and based on the so-called generalized Bernstein functional relation, is applied to one-loop multi-leg diagrams with particular emphasis to the presence of infrared singularities, to the problem of tensorial reduction and to the classification of all singularities of a given diagram. Successively, the extension of the algorithm to two-loop diagrams is examined. The proposed solution consists in applying the functional relation to the one-loop sub-diagram which has the largest number of internal lines. In this way the integrand can be made smooth, a part from a factor which is a polynomial in xS, the vector of Feynman parameters needed for the complementary sub-diagram with the smallest number of internal lines. Since the procedure does not introduce new singularities one can distort the xS-integration hyper-contour into the complex hyper-plane, thus achieving numerical stability. The algorithm is then modified to deal with numerical evaluation around normal thresholds. Concise and practical formulas are assembled and presented, numerical results and comparisons with the available literature are shown and discussed for the so-called sunset topology.
NASA Astrophysics Data System (ADS)
Ryan, E. J.; Smithers, S. G.; Lewis, S. E.; Clark, T. R.; Zhao, J. X.
2016-09-01
The geomorphology and chronostratigraphy of the reef flat (including microatoll ages and elevations) were investigated to better understand the long-term development of the reef at Middle Island, inshore central Great Barrier Reef. Eleven cores across the fringing reef captured reef initiation, framework accretion and matrix sediments, allowing a comprehensive appreciation of reef development. Precise uranium-thorium ages obtained from coral skeletons revealed that the reef initiated ~7873 ± 17 years before present (yBP), and most of the reef was emplaced in the following 1000 yr. Average rates of vertical reef accretion ranged between 3.5 and 7.6 mm yr-1. Reef framework was dominated by branching corals ( Acropora and Montipora). An age hiatus of ~5000 yr between 6439 ± 19 and 1617 ± 10 yBP was observed in the core data and attributed to stripping of the reef structure by intense cyclones during the mid- to late-Holocene. Large shingle ridges deposited onshore and basset edges preserved on the reef flat document the influence of cyclones at Middle Island and represent potential sinks for much of the stripped material. Stripping of the upper reef structure around the outer margin of the reef flat by cyclones created accommodation space for a thin (<1.2 m) veneer of reef growth after 1617 ± 10 yBP that grew over the eroded mid-Holocene reef structure. Although limited fetch and open-water exposure might suggest the reef flat at Middle Island is quite protected, our results show that high-energy waves presumably generated by cyclones have significantly influenced both Holocene reef growth and contemporary reef flat geomorphology.
Monitoring transients in low inductance circuits
Guilford, Richard P.; Rosborough, John R.
1987-01-01
A pair of flat cable transmission lines are monitored for transient current spikes by using a probe connected to a current transformer by a pickup loop and monitoring the output of the current transformer. The approach utilizes a U-shaped pickup probe wherein the pair of flat cable transmission lines are received between the legs of the U-shaped probe. The U-shaped probe is preferably formed of a flat coil conductor adhered to one side of a flexible substrate. On the other side of the flexible substrate there is a copper foil shield. The copper foil shield is connected to one end of the flat conductor coil and connected to one leg of the pickup loop which passes through the current transformer. The other end of the flat conductor coil is connected to the other leg of the pickup loop.
A Global Estimate of the Number of Coral Reef Fishers.
Teh, Louise S L; Teh, Lydia C L; Sumaila, U Rashid
2013-01-01
Overfishing threatens coral reefs worldwide, yet there is no reliable estimate on the number of reef fishers globally. We address this data gap by quantifying the number of reef fishers on a global scale, using two approaches - the first estimates reef fishers as a proportion of the total number of marine fishers in a country, based on the ratio of reef-related to total marine fish landed values. The second estimates reef fishers as a function of coral reef area, rural coastal population, and fishing pressure. In total, we find that there are 6 million reef fishers in 99 reef countries and territories worldwide, of which at least 25% are reef gleaners. Our estimates are an improvement over most existing fisher population statistics, which tend to omit accounting for gleaners and reef fishers. Our results suggest that slightly over a quarter of the world's small-scale fishers fish on coral reefs, and half of all coral reef fishers are in Southeast Asia. Coral reefs evidently support the socio-economic well-being of numerous coastal communities. By quantifying the number of people who are employed as reef fishers, we provide decision-makers with an important input into planning for sustainable coral reef fisheries at the appropriate scale.
A Global Estimate of the Number of Coral Reef Fishers
Teh, Louise S. L.; Teh, Lydia C. L.; Sumaila, U. Rashid
2013-01-01
Overfishing threatens coral reefs worldwide, yet there is no reliable estimate on the number of reef fishers globally. We address this data gap by quantifying the number of reef fishers on a global scale, using two approaches - the first estimates reef fishers as a proportion of the total number of marine fishers in a country, based on the ratio of reef-related to total marine fish landed values. The second estimates reef fishers as a function of coral reef area, rural coastal population, and fishing pressure. In total, we find that there are 6 million reef fishers in 99 reef countries and territories worldwide, of which at least 25% are reef gleaners. Our estimates are an improvement over most existing fisher population statistics, which tend to omit accounting for gleaners and reef fishers. Our results suggest that slightly over a quarter of the world’s small-scale fishers fish on coral reefs, and half of all coral reef fishers are in Southeast Asia. Coral reefs evidently support the socio-economic well-being of numerous coastal communities. By quantifying the number of people who are employed as reef fishers, we provide decision-makers with an important input into planning for sustainable coral reef fisheries at the appropriate scale. PMID:23840327
Crustose coralline algae increased framework and diversity on ancient coral reefs.
Weiss, Anna; Martindale, Rowan C
2017-01-01
Crustose coralline algae (CCA) are key producers of carbonate sediment on reefs today. Despite their importance in modern reef ecosystems, the long-term relationship of CCA with reef development has not been quantitatively assessed in the fossil record. This study includes data from 128 Cenozoic coral reefs collected from the Paleobiology Database, the Paleoreefs Database, as well as the original literature and assesses the correlation of CCA abundance with taxonomic diversity (both corals and reef dwellers) and framework of fossil coral reefs. Chi-squared tests show reef type is significantly correlated with CCA abundance and post-hoc tests indicate higher involvement of CCA is associated with stronger reef structure. Additionally, general linear models show coral reefs with higher amounts of CCA had a higher diversity of reef-dwelling organisms. These data have important implications for paleoecology as they demonstrate that CCA increased building capacity, structural integrity, and diversity of ancient coral reefs. The analyses presented here demonstrate that the function of CCA on modern coral reefs is similar to their function on Cenozoic reefs; thus, studies of ancient coral reef collapse are even more meaningful as modern analogues.
Dinitroanilines Bind α-Tubulin to Disrupt Microtubules
Morrissette, Naomi S.; Mitra, Arpita; Sept, David; Sibley, L. David
2004-01-01
Protozoan parasites are remarkably sensitive to dinitroanilines such as oryzalin, which disrupt plant but not animal microtubules. To explore the basis of dinitroaniline action, we isolated 49 independent resistant Toxoplasma gondii lines after chemical mutagenesis. All 23 of the lines that we examined harbored single point mutations in α-tubulin. These point mutations were sufficient to confer resistance when transfected into wild-type parasites. Several mutations were in the M or N loops, which coordinate protofilament interactions in the microtubule, but most of the mutations were in the core of α-tubulin. Docking studies predict that oryzalin binds with an average affinity of 23 nM to a site located beneath the N loop of Toxoplasma α-tubulin. This binding site included residues that were mutated in several resistant lines. Moreover, parallel analysis of Bos taurus α-tubulin indicated that oryzalin did not interact with this site and had a significantly decreased, nonspecific affinity for vertebrate α-tubulin. We propose that the dinitroanilines act through a novel mechanism, by disrupting M-N loop contacts. These compounds also represent the first class of drugs that act on α-tubulin function. PMID:14742718
Wörheide, Gert; Hooper, John N A; Degnan, Bernard M
2002-09-01
Leucetta 'chagosensis' is a widespread calcareous sponge, occurring in shaded habitats of Indo-Pacific coral reefs. In this study we explore relationships among 19 ribosomal DNA sequence types (the ITS1-5.8S-ITS2 region plus flanking gene sequences) found among 54 individuals from 28 locations throughout the western Pacific, with focus on the Great Barrier Reef (GBR). Maximum parsimony analysis revealed phylogeographical structuring into four major clades (although not highly supported by bootstrap analysis) corresponding to the northern/central GBR with Guam and Taiwan, the southern GBR and subtropical regions south to Brisbane, Vanuatu and Indonesia. Subsequent nested clade analysis (NCA) confirmed this structure with a probability of > 95%. After NCA of geographical distances, a pattern of range expansion from the internal Indonesian clade was inferred at the total cladogram level, as the Indonesian clade was found to be the internal and therefore oldest clade. Two distinct clades were found on the GBR, which narrowly overlap geographically in a line approximately from the Whitsunday Islands to the northern Swain Reefs. At various clade levels, NCA inferred that the northern GBR clade was influenced by past fragmentation and contiguous range expansion events, presumably during/after sea level low stands in the Pleistocene, after which the northern GBR might have been recolonized from the Queensland Plateau in the Coral Sea. The southern GBR clade is most closely related to subtropical L. 'chagosensis', and we infer that the southern GBR probably was recolonized from there after sea level low stands, based on our NCA results and supported by oceanographic data. Our results have important implications for conservation and management of the GBR, as they highlight the importance of marginal transition zones in the generation and maintenance of species rich zones, such as the Great Barrier Reef World Heritage Area.
Andréfouët, S; Wantiez, L
2010-01-01
Since 1972, the UNESCO "World Heritage Convention" offers an international canvas for conservation and management that targets areas of high cultural and environmental significance. To support the designation of areas within the 36.000 km(2) of New Caledonia coral reefs and lagoons as a World Heritage Site, the natural value and diversity of the proposed zones needed to be demonstrated. To exhaustively identify each configuration of shallow habitats, high resolution remote sensing images were used to select the sampling sites. This optimal scheme resulted in the selection of nearly 1300 sampling sites, and was then simplified to render its application realistic. In the final sampling plan, only the most common or the most remarkable coral zones were selected. Following this selection, in situ habitat and fish surveys were conducted in 2006-2008 in five large areas spanning a 600 km-long latitudinal gradient. Habitats were described using line-intercept transects in parallel with underwater visual census of indicator and commercial coral reef fish species. We report here on the results achieved in terms of: (i) the actual diversity of coral habitats captured by the remote sensing based sampling strategy, (ii) the different reef fish communities captured from the different sites, and (iii) how well they represent New Caledonia diversity. We discuss the possible generalization of this scheme to other sites, in the context of World Heritage Site selection and for other large-scale conservation planning activities. Copyright (c) 2010 Elsevier Ltd. All rights reserved.
Hoeke, R.; Storlazzi, C.; Ridd, P.
2011-01-01
This paper examines the relationship between offshore wave climate and nearshore waves and currents at Hanalei Bay, Hawaii, an exposed bay fringed with coral reefs. Analysis of both offshore in situ data and numerical hindcasts identify the predominance of two wave conditions: a mode associated with local trade winds and an episodic pattern associated with distant source long-period swells. Analysis of 10 months of in situ data within the bay show that current velocities are up to an order of magnitude greater during long-period swell episodes than during trade wind conditions; overall circulation patterns are also fundamentally different. The current velocities are highly correlated with incident wave heights during the swell episodes, while they are not during the modal trade wind conditions. A phase-averaged wave model was implemented with the dual purpose of evaluating application to bathymetrically complex fringing reefs and to examine the propagation of waves into the nearshore in an effort to better explain the large difference in observed circulation during the two offshore wave conditions. The prediction quality of this model was poorer for the episodic condition than for the lower-energy mode, however, it illustrated how longer-period swells are preferentially refracted into the bay and make available far more nearshore wave energy to drive currents compared to waves during modal conditions. The highly episodic circulation, the nature of which is dependent on complex refraction patterns of episodic, long-period swell has implications for flushing and sediment dynamics for incised fringing reef-lined bays that characterize many high islands at low latitudes around the world.
LINE-OF-SIGHT SHELL STRUCTURE OF THE CYGNUS LOOP
DOE Office of Scientific and Technical Information (OSTI.GOV)
Uchida, Hiroyuki; Tsunemi, Hiroshi; Katsuda, Satoru
We conducted a comprehensive study on the shell structure of the Cygnus Loop using 41 observation data obtained by the Suzaku and the XMM-Newton satellites. To investigate the detailed plasma structure of the Cygnus Loop, we divided our fields of view into 1042 box regions. From the spectral analysis, the spectra obtained from the limb of the Loop are well fitted by the single-component non-equilibrium ionization plasma model. On the other hand, the spectra obtained from the inner regions are well fitted by the two-component model. As a result, we confirmed that the low-temperature and high-temperature components originated from themore » surrounding interstellar matter (ISM) and the ejecta of the Loop, respectively. From the best-fit results, we showed a flux distribution of the ISM component. The distribution clearly shows the limb-brightening structure, and we found out some low-flux regions. Among them, the south blowout region has the lowest flux. We also found other large low-flux regions at slightly west and northeast from the center. We estimated the former thin shell region to be approx1.{sup 0}3 in diameter and concluded that there exists a blowout along the line of sight in addition to the south blowout. We also calculated the emission measure distribution of the ISM component and showed that the Cygnus Loop is far from the result obtained by a simple Sedov evolution model. From the results, we support that the Cygnus Loop originated from a cavity explosion. The emission measure distribution also suggests that the cavity-wall density is higher in the northeast than that in the southwest. These results suggest that the thickness of the cavity wall surrounding the Cygnus Loop is not uniform.« less
High-altitude closed magnetic loops at Mars observed by MAVEN
NASA Astrophysics Data System (ADS)
Xu, Shaosui; Mitchell, David; Luhmann, Janet; Ma, Yingjuan; Fang, Xiaohua; Harada, Yuki; Hara, Takuya; Brain, David; Webber, Tristan; Mazelle, Christian; DiBraccio, Gina A.
2017-10-01
With electron and magnetic field data obtained by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we have identified closed magnetic field lines, with both footpoints embedded in the dayside ionosphere, extending up to 6200 km altitude (2.8 $R_m$) into the Martian tail. This topology is deduced from photoelectrons produced in the dayside ionosphere being observed in both parallel and anti-parallel directions along the magnetic field line. At perpendicular pitch angles, cases with either solar wind electrons or photoelectrons have been found, indicative of different formation mechanisms of these closed loops. These large closed loops are predicted by MHD simulations. The case with field-aligned photoelectrons mixed with perpendicular solar wind electrons is likely to be associated with reconnection, while the case with photoelectrons in all directions are probably due to closed field lines being pulled back down tail. We have developed an automated algorithm for distinguishing photoelectrons from solar wind electrons in pitch angle resolved energy spectra. This allows us to systematically analyze the MAVEN database and map the spatial distribution and occurrence rate of these closed magnetic loops, ranging from a few percent to a few tens percent outside of the optical shadow and less than one percent within the wake. These observations can be used to investigate the general magnetic topology in the tail, which is relevant to ion escape, reconnection, and flux ropes.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Brannon, Sean R.
Despite significant advances in instrumentation, there remain no studies that analyze observations of on-disk flare loop plasma flows covering the entire evolution from chromospheric evaporation, through plasma cooling, to draining downflows. We present results from an imaging and spectroscopic observation from the Interface Region Imaging Spectrograph ( IRIS ) of the SOL2015–03–12T11:50:00 M-class flare, at high spatial resolution and time cadence. Our analysis of this event reveals initial plasma evaporation at flare temperatures indicated by 100–200 km s{sup −1} blueshifts in the Fe xxi line. We subsequently observe plasma cooling into chromospheric lines (Si iv and O iv) with ∼11more » minute delay, followed by loop draining at ∼40 km s{sup −1} as indicated by a “C”-shaped redshift structure and significant (∼60 km s{sup −1}) non-thermal broadening. We use density-sensitive lines to calculate a plasma density for the flare loops, and estimate a theoretical cooling time approximately equal to the observed delay. Finally, we use a simple elliptical free-fall draining model to construct synthetic spectra, and perform what we believe to be the first direct comparison of such synthetic spectra to observations of draining downflows in flare loops.« less
Diagrammatic exponentiation for products of Wilson lines
NASA Astrophysics Data System (ADS)
Mitov, Alexander; Sterman, George; Sung, Ilmo
2010-11-01
We provide a recursive diagrammatic prescription for the exponentiation of gauge theory amplitudes involving products of Wilson lines and loops. This construction generalizes the concept of webs, originally developed for eikonal form factors and cross sections with two eikonal lines, to general soft functions in QCD and related gauge theories. Our coordinate space arguments apply to arbitrary paths for the lines.
NLO evolution of 3-quark Wilson loop operator
Balitsky, I.; Grabovsky, A. V.
2015-01-07
It is well known that high-energy scattering of a meson from some hadronic target can be described by the interaction of that target with a color dipole formed by two Wilson lines corresponding to fast quark-antiquark pair. Moreover, the energy dependence of the scattering amplitude is governed by the evolution equation of this color dipole with respect to rapidity. Similarly, the energy dependence of scattering of a baryon can be described in terms of evolution of a three-Wilson-lines operator with respect to the rapidity of the Wilson lines. We calculate the evolution of the 3-quark Wilson loop operator in themore » next-to-leading order (NLO) and present a quasi-conformal evolution equation for a composite 3-Wilson-lines operator. Thus we also obtain the linearized version of that evolution equation describing the amplitude of the odderon exchange at high energies.« less
Multiturn split-conductor transmission-line resonator
NASA Astrophysics Data System (ADS)
Haziza, Nathalie; Bittoun, Jacques; Kan, Siew
1997-05-01
A split-conductor parallel-plate transmission line resonator is a simple structure made from bending a strip of double-face copper-clad printed-circuit board into a loop with alternate electrical discontinuities (gaps) on opposite sides. Its natural resonant frequency (Fn) is determined by the transmission line characteristic impedance, the loop diameter or strip length, and the number (Ng) of gaps. It is easy to design high frequency resonators simply by increasing Ng. We propose here a single-gap multiturn resonator for low frequency operation as well as a simplified expression for the determination of Fn. A design procedure of this type of resonator is outlined and illustrative examples with parallel-plate as well as ordinary 50 Ω coaxial transmission lines are given. Also, for a given cable length, numerical calculation shows that the minimum resonator frequency can be attained with a form factor of the order of 2.
Small-Boat Noise Impacts Natural Settlement Behavior of Coral Reef Fish Larvae.
Simpson, Stephen D; Radford, Andrew N; Holles, Sophie; Ferarri, Maud C O; Chivers, Douglas P; McCormick, Mark I; Meekan, Mark G
2016-01-01
After a pelagic larval phase, settlement-stage coral reef fish must locate a suitable reef habitat for juvenile life. Reef noise, produced by resident fish and invertebrates, provides an important cue for orientation and habitat selection during this process, which must often occur in environments impacted by anthropogenic noise. We adapted an established field-based protocol to test whether recorded boat noise influenced the settlement behavior of reef fish. Fewer fish settled to patch reefs broadcasting boat + reef noise compared with reef noise alone. This study suggests that boat noise, now a common feature of many reefs, can compromise critical settlement behavior of reef fishes.
DC servomechanism parameter identification: a Closed Loop Input Error approach.
Garrido, Ruben; Miranda, Roger
2012-01-01
This paper presents a Closed Loop Input Error (CLIE) approach for on-line parametric estimation of a continuous-time model of a DC servomechanism functioning in closed loop. A standard Proportional Derivative (PD) position controller stabilizes the loop without requiring knowledge on the servomechanism parameters. The analysis of the identification algorithm takes into account the control law employed for closing the loop. The model contains four parameters that depend on the servo inertia, viscous, and Coulomb friction as well as on a constant disturbance. Lyapunov stability theory permits assessing boundedness of the signals associated to the identification algorithm. Experiments on a laboratory prototype allows evaluating the performance of the approach. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.
Thermal Analysis of Post-eruption Loops from 80,000 to 1.6 million K
NASA Technical Reports Server (NTRS)
Kucera, T.; Landi, E.
2006-01-01
We analyze the thermal properties of a set of post eruptive loops which appeared after a prominence eruption on April 30, 2004. The event was observed by TRACE and SOHO/SUMER. The SUMER data was taken from a single slit location with a 90 second cadence and included a number of lines spanning the temperature range 80,000 to 1.6 million K. We perform a differential emission measure analysis of the loops in order to study their thermal evolution.
Development of a Microprocessor-Based Asynchronous Data Communications Line Tester.
1981-12-01
either RS232 or 20 mA current loop 13. Current loop optically isolated 14. Current loop selectable for either active or pasive mode 15. Address...Executin Invoking the execution of the software is therefore a matter of power-up and reset. The software will wait for a response from the console (any key...SIO has two channels as previously mentioned. Addressing the SIO then is a matter of addressing these two channels. The port addrecses are user defined
NASA Technical Reports Server (NTRS)
Zirin, H.; Tanaka, K.
1972-01-01
Analysis is made of observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra. In each flare the observations fit a model of particle acceleration in the chromosphere with emission produced by impart and by heating by the energetic electrons and protons. The region showed twisted flux and high gradients from birth, and flares appear due to strong magnetic shears and gradients across the neutral line produced by sunspot motions. Post flare loops show a strong change from sheared, force-free fields parallel to potential-field-like loops, perpendicular to the neutral line above the surface.
Generation and dynamics of optical beams with polarization singularities.
Cardano, Filippo; Karimi, Ebrahim; Marrucci, Lorenzo; de Lisio, Corrado; Santamato, Enrico
2013-04-08
We present a convenient method to generate vector beams of light having polarization singularities on their axis, via partial spin-to-orbital angular momentum conversion in a suitably patterned liquid crystal cell. The resulting polarization patterns exhibit a C-point on the beam axis and an L-line loop around it, and may have different geometrical structures such as "lemon", "star", and "spiral". Our generation method allows us to control the radius of L-line loop around the central C-point. Moreover, we investigate the free-air propagation of these fields across a Rayleigh range.
Huang, Chiung-Yao; Su, Jui-Hsin; Liaw, Chih-Chuang; Sung, Ping-Jyun; Chiang, Pei-Lun; Hwang, Tsong-Long; Dai, Chang-Feng; Sheu, Jyh-Horng
2017-09-01
A c ontinuing chemical investigation of the ethyl acetate (EtOAc) extract of a reef soft coral Sinularia brassica , which was cultured in a tank, afforded four new steroids with methyl ester groups, sinubrasones A-D (1-4) for the first time. In particular, 1 possesses a β-D-xylopyranose. The structures of the new compounds were elucidated on the basis of spectroscopic analyses. The cytotoxicities of compounds 1-4 against the proliferation of a limited panel of cancer cell lines were assayed. The anti-inflammatory activities of these new compounds 1-4 were also evaluated by measuring their ability to suppress superoxide anion generation and elastase release in N -formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-induced human neutrophils. Compounds 2 and 3 were shown to exhibit significant cytotoxicity, and compounds 3 and 4 were also found to display attracting anti-inflammatory activities.
Conservation status and spatial patterns of AGRRA vitality indices in Southwestern Atlantic reefs.
Kikuchi, Ruy K P; Leão, Zelinda M A N; Oliveira, Marília D M
2010-05-01
Coral reefs along the Eastern Brazilian coast extend for a distance of 800 km from 12 degrees to 18 degrees S. They are the largest and the richest reefs of Brazil coasts, and represent the Southernmost coral reefs of the Southwestern Atlantic Ocean. Few reef surveys were performed in the 90's in reef areas of Bahia State, particularly in the Abrolhos reef complex, in the Southernmost side of the state. A monitoring program applying the Atlantic and Gulf Rapid Reef Assessment (AGRRA) protocol was initiated in 2000, in the Abrolhos National Marine Park, after the creation of the South Tropical America (STA) Regional Node of the Global Coral Reef Monitoring Network (GCRMN) by the end of 1999. From that time up to 2005, nine reef surveys were conducted along the coast of the State of Bahia, including 26 reefs, with 95 benthic sites, 280 benthic transects, 2025 quadrats and 3537 stony corals. Eighteen of the 26 investigated reefs were assessed once and eight reefs of Abrolhos were surveyed twice to four times. The MDS ordination, analysis of similarity (ANOSIM, one way and two-way nested layouts) and similarity percentages (SIMPER) tests were applied to investigate the spatial and temporal patterns of reef vitality. Four indicators of the coral vitality: live coral cover, the density of the larger corals (colonics > 20cm per reef site) and of the coral recruits (colonies < 2cm per square meter), and the percentage of macroalgae indicate that the nearshore reefs, which are located less than 5 km from the coast, are in poorer condition than the reefs located more than 5 km off the coast. A higher density of coral colonies, lower macroalgal index, higher relative percent of turf algae and higher density of coral recruits in offshore reefs compared to the nearshore reefs are the conditions that contribute more than 80% to the dissimilarity between them. The offshore reefs are in better vital condition than the nearshore reefs and have a set of vitality indices more closely related to the Northwestern Atlantic reefs than the nearshore reef. These have been most severely impacted by the effects of direct human activities such as cuthrophic waters associated with sewage pollution, higher sedimentation rates and water turbidity, inadequate use of the reefs and over exploitation of their resources. The implementation of a more effective coral reef monitoring program in Bahia is mandatory, in order to improve the strategies for protection and management efforts of the reefs.
Computer Generated Snapshot of Our Sun's Magnetic Field
NASA Technical Reports Server (NTRS)
2003-01-01
These banana-shaped loops are part of a computer-generated snapshot of our sun's magnetic field. The solar magnetic-field lines loop through the sun's corona, break through the sun's surface, and cornect regions of magnetic activity, such as sunspots. This image --part of a magnetic-field study of the sun by NASA's Allen Gary -- shows the outer portion (skins) of interconnecting systems of hot (2 million degrees Kelvin) coronal loops within and between two active magnetic regions on opposite sides of the sun's equator. The diameter of these coronal loops at their foot points is approximately the same size as the Earth's radius (about 6,000 kilometers).
An interacting loop model of solar flare bursts
NASA Technical Reports Server (NTRS)
Emslie, A. G.
1981-01-01
As a result of the strong heating produced at chromospheric levels during a solar flare burst, the local gas pressure can transiently attain very large values in certain regions. The effectiveness of the surrounding magnetic field at confining this high pressure plasma is therefore reduced and the flaring loop becomes free to expand laterally. In so doing it may drive magnetic field lines into neighboring, nonflaring, loops in the same active region, causing magnetic reconnection to take place and triggering another flare burst. The features of this interacting loop model are found to be in good agreement with the energetics and time structure of flare associated solar hard X-ray bursts.
Development of Murray Loop Bridge for High Induced Voltage
NASA Astrophysics Data System (ADS)
Isono, Shigeki; Kawasaki, Katsutoshi; Kobayashi, Shin-Ichi; Ishihara, Hayato; Chiyajo, Kiyonobu
In the case of the cable fault that ground fault resistance is less than 10MΩ, Murray Loop Bridge is excellent as a fault locator in location accuracy and the convenience. But, when the induction of several hundred V is taken from the single core cable which adjoins it, a fault location with the high voltage Murray Loop Bridge becomes difficult. Therefore, we developed Murray Loop Bridge, which could be applied even when the induced voltage of several hundred V occurs in the measurement cable. The evaluation of the fault location accuracy was done with the developed prototype by the actual line and the training equipment.
Artificial reefs and reef restoration in the Laurentian Great Lakes
McLean, Matthew W.; Roseman, Edward; Pritt, Jeremy J.; Kennedy, Gregory W.; Manny, Bruce A.
2015-01-01
We reviewed the published literature to provide an inventory of Laurentian Great Lakes artificial reef projects and their purposes. We also sought to characterize physical and biological monitoring for artificial reef projects in the Great Lakes and determine the success of artificial reefs in meeting project objectives. We found records of 6 artificial reefs in Lake Erie, 8 in Lake Michigan, 3 in Lakes Huron and Ontario, and 2 in Lake Superior. We found 9 reefs in Great Lakes connecting channels and 6 reefs in Great Lakes tributaries. Objectives of artificial reef creation have included reducing impacts of currents and waves, providing safe harbors, improving sport-fishing opportunities, and enhancing/restoring fish spawning habitats. Most reefs in the lakes themselves were incidental (not created purposely for fish habitat) or built to improve local sport fishing, whereas reefs in tributaries and connecting channels were more frequently built to benefit fish spawning. Levels of assessment of reef performance varied; but long-term monitoring was uncommon as was assessment of physical attributes. Artificial reefs were often successful at attracting recreational species and spawning fish; however, population-level benefits of artificial reefs are unclear. Stressors such as sedimentation and bio-fouling can limit the effectiveness of artificial reefs as spawning enhancement tools. Our investigation underscores the need to develop standard protocols for monitoring the biological and physical attributes of artificial structures. Further, long-term monitoring is needed to assess the benefits of artificial reefs to fish populations and inform future artificial reef projects.
NASA Astrophysics Data System (ADS)
Polito, V.; Testa, P.; De Pontieu, B.; Allred, J. C.
2017-12-01
The observation of the high temperature (above 10 MK) Fe XXI 1354.1 A line with the Interface Region Imaging Spectrograph (IRIS) has provided significant insights into the chromospheric evaporation process in flares. In particular, the line is often observed to be completely blueshifted, in contrast to previous observations at lower spatial and spectral resolution, and in agreement with predictions from theoretical models. Interestingly, the line is also observed to be mostly symmetric and with a large excess above the thermal width. One popular interpretation for the excess broadening is given by assuming a superposition of flows from different loop strands. In this work, we perform a statistical analysis of Fe XXI line profiles observed by IRIS during the impulsive phase of flares and compare our results with hydrodynamic simulations of multi-thread flare loops performed with the 1D RADYN code. Our results indicate that the multi-thread models cannot easily reproduce the symmetry of the line and that some other physical process might need to be invoked in order to explain the observed profiles.
Many atolls may be uninhabitable within decades due to climate change
Storlazzi, Curt; Elias, Edwin P.L.; Berkowitz, Paul
2015-01-01
Observations show global sea level is rising due to climate change, with the highest rates in the tropical Pacific Ocean where many of the world’s low-lying atolls are located. Sea-level rise is particularly critical for low-lying carbonate reef-lined atoll islands; these islands have limited land and water available for human habitation, water and food sources, and ecosystems that are vulnerable to inundation from sea-level rise. Here we demonstrate that sea-level rise will result in larger waves and higher wave-driven water levels along atoll islands’ shorelines than at present. Numerical model results reveal waves will synergistically interact with sea-level rise, causing twice as much land forecast to be flooded for a given value of sea-level rise than currently predicted by current models that do not take wave-driven water levels into account. Atolls with islands close to the shallow reef crest are more likely to be subjected to greater wave-induced run-up and flooding due to sea-level rise than those with deeper reef crests farther from the islands’ shorelines. It appears that many atoll islands will be flooded annually, salinizing the limited freshwater resources and thus likely forcing inhabitants to abandon their islands in decades, not centuries, as previously thought.
Storlazzi, Curt D.; Presto, M. Katherine; Logan, Joshua B.; Field, Michael E.
2008-01-01
High-resolution measurements of waves, currents, water levels, temperature, salinity and turbidity were made in Hanalei Bay, northern Kaua'i, Hawai'i, during the summer of 2006 to better understand coastal circulation, sediment dynamics, and the potential impact of a river flood in a coral reef-lined embayment during quiescent summer conditions. A series of bottommounted instrument packages were deployed in water depths of 10 m or less to collect long-term, high-resolution measurements of waves, currents, water levels, temperature, salinity, and turbidity. These data were supplemented with a series of profiles through the water column to characterize the vertical and spatial variability in water column properties within the bay. These measurements support the ongoing process studies being conducted as part of the U.S. Geological Survey (USGS) Coastal and Marine Geology Program's Pacific Coral Reef Project; the ultimate goal is to better understand the transport mechanisms of sediment, larvae, pollutants, and other particles in coral reef settings. Information regarding the USGS study conducted in Hanalei Bay during the 2005 summer is available in Storlazzi and others (2006), Draut and others (2006) and Carr and others (2006). This report, the last part in a series, describes data acquisition, processing, and analysis for the 2006 summer data set.
Ecological carrying capacity assessment of diving site: A case study of Mabul Island, Malaysia.
Zhang, Li-Ye; Chung, Shan-Shan; Qiu, Jian-Wen
2016-12-01
Despite considered a non-consumptive use of the marine environment, diving-related activities can cause damages to coral reefs. It is imminent to assess the maximum numbers of divers that can be accommodated by a diving site before it is subject to irreversible deterioration. This study aimed to assess the ecological carrying capacity of a diving site in Mabul Island, Malaysia. Photo-quadrat line transect method was used in the benthic survey. The ecological carrying capacity was assessed based on the relationship between the number of divers and the proportion of diver damaged hard corals in Mabul Island. The results indicated that the proportion of diver damaged hard corals occurred exponentially with increasing use. The ecological carrying capacity of Mabul Island is 15,600-16,800 divers per diving site per year at current levels of diver education and training with a quarterly threshold of 3900-4200 per site. Our calculation shows that management intervention (e.g. limiting diving) is justified at 8-14% of hard coral damage. In addition, the use of coral reef dominated diving sites should be managed according to their sensitivity to diver damage and the depth of the reefs. Copyright © 2016 Elsevier Ltd. All rights reserved.
Geoscience Laser Altimeter System (GLAS) Final Test Report of DM LHP TV Testing
NASA Technical Reports Server (NTRS)
Baker, Charles
2000-01-01
Two loop heat pipes (LHPs) are to be used for thermal control of the Geoscience Laser Altimeter System (GLAS), planned for flight in 2001. One LHP will be used to transport 100 W from a laser to the radiator, the other will transport 210 W from electronic boxes to the radiator. In order to verify the LHP design for the GLAS application, an LHP Development Model has been fabricated, and ambient and thermal vacuum tested. Two aluminum blocks of 15 kg and 30 kg, respectively, were attached to the LHP to simulate the thermal masses connected to the heat sources. A 20 W starter heater was installed on the evaporator to aid the loop startup. A new concept to thermally couple the vapor and liquid line was also incorporated in the LHP design. Such a thermal coupling would reduce the power requirement on the compensation chamber in order to maintain the loop set point temperature. To avoid freezing of the liquid in the condenser during cold cases, propylene was selected as the working fluid. The LHP was tested under reflux mode and with adverse elevation. Tests conducted included start-up, power cycle, steady state and transient operation during hot and cold cases, and heater power requirements for the set point temperature control of the LHP. Test results showed very successful operation of the LHP under all conditions. The 20 W starter heater proved necessary in order to start the loop when a large thermal mass was attached to the evaporator. The thermal coupling between the liquid line and the vapor line significantly reduced the heater power required for loop temperature control, which was less than 5 watts in all cases, including a cold radiator. The test also demonstrated successful operation with a propylene working fluid, with successful startups with condenser temperatures as low as 100 C. Furthermore, the test demonstrated accurate control of the loop operating temperature within +/- 0.2 C, and a successful shutdown of the loop during the survival mode of operation.
NASA Technical Reports Server (NTRS)
Chen, George T.
1987-01-01
An automatic control scheme for spacecraft proximity operations is presented. The controller is capable of holding the vehicle at a prescribed location relative to a target, or maneuvering it to a different relative position using straight line-of-sight translations. The autopilot uses a feedforward loop to initiate and terminate maneuvers, and for operations at nonequilibrium set-points. A multivariate feedback loop facilitates precise position and velocity control in the presence of sensor noise. The feedback loop is formulated using the Linear Quadratic Gaussian (LQG) with Loop Transfer Recovery (LTR) design procedure. Linear models of spacecraft dynamics, adapted from Clohessey-Wiltshire Equations, are augmented and loop shaping techniques are applied to design a target feedback loop. The loop transfer recovery procedure is used to recover the frequency domain properties of the target feedback loop. The resulting compensator is integrated into an autopilot which is tested in a high fidelity Space Shuttle Simulator. The autopilot performance is evaluated for a variety of proximity operations tasks envisioned for future Shuttle flights.
NASA Astrophysics Data System (ADS)
Brosius, J. W.
2012-12-01
We observed a C1 flare in rapid cadence stare mode simultaneously with Hinode's EIS (11.2 s) and SOHO's CDS (10 s) on 2012 March 7. The pointings of the two slits were offset about 25 arcsec, so that EIS observed the leg and CDS the apex of the flaring loop. EIS observed the Fe XXIII line at 263.8 A, formed at temperatures around 14 MK, to emerge abruptly above the background noise at 18:49:36 UT. The line's intensity peaked at 18:53:09 UT. After its emergence the Fe XXIII line's entire profile became increasingly blueshifted over the next 3 exposures, reached a maximum upward velocity of -208 km/s, and then became decreasingly blueshifted toward zero velocity while the line's intensity continued to increase over the next 12 exposures. The bulk of the Fe XXIII emission remained stationary after that. A secondary blueshifted component of the Fe XXIII line profile appeared at 18:52:24 UT, endured for 5 exposures, and reached a maximum upward velocity of -206 km/s. We interpret this sudden, brief re-appearance of rapid upward velocity in Fe XXIII emission as evidence for ongoing reconnection following the flare's initial, impulsive phase. The structure of the loop and its strand footpoints seen in the AIA 131 and 94 A images reveal changes possibly due to the cutting and rearrangement of individual strands during reconnection. Emission lines of Fe XVII, formed at temperatures around 4 MK, and Fe XVI, formed around 2.7 MK, brightened significantly starting about 3.3 and 7.1 minutes after the first appearance of Fe XXIII emission, likely due to cooling of plasma previously heated to temperatures appropriate for Fe XXIII emission. Neither Fe XVII nor Fe XVI showed significant relative Doppler velocities. None of the transition region lines observed by EIS participated in the event. CDS spectra were contaminated by a particle storm at SOHO during the flare, but we were able to salvage roughly 1/3 of the exposures by visually inspecting individual line profiles and discarding those that appeared affected. The intensity of the Fe XIX line at 592.2 A, formed at 8 MK, reached its maximum value at the location of the CDS slit near the flare loop apex about 4.6 minutes after the Fe XXIII line reached its peak intensity. This work was supported by NASA grant NNX10AC08G.
Linking Wave Forcing to Coral Cover and Structural Complexity Across Coral Reef Flats
NASA Astrophysics Data System (ADS)
Harris, D. L.; Rovere, A.; Parravicini, V.; Casella, E.
2015-12-01
The hydrodynamic regime is a significant component in the geomorphic and ecological development of coral reefs. The energy gradients and flow conditions generated by the breaking and transformation of waves across coral reef crests and flats drive changes in geomorphic structure, and coral growth form and distribution. One of the key aspects in regulating the wave energy propagating across reef flats is the rugosity or roughness of the benthic substrate. Rugosity and structural complexity of coral reefs is also a key indicator of species diversity, ecological functioning, and reef health. However, the links between reef rugosity, coral species distribution and abundance, and hydrodynamic forcing are poorly understood. In this study we examine this relationship by using high resolution measurement of waves in the surf zone and coral reef benthic structure.Pressure transducers (logging at 4 Hz) were deployed in cross reef transects at two sites (Tiahura and Ha'apiti reef systems) in Moorea, French Polynesia with wave characteristics determined on a wave by wave basis. A one dimensional hydrodynamic model (XBeach) was calibrated from this data to determine wave processes on the reef flats under average conditions. Transects of the reef benthic structure were conducted using photographic analysis and the three dimensional reef surface was constructed using structure from motion procedures. From this analysis reef rugosity, changes in coral genus and growth form, and across reef shifts in benthic community were determined. The results show clear changes in benthic assemblages along wave energy gradients with some indication of threshold values of wave induced bed shear stress above which live coral cover was reduced. Reef rugosity was shown to be significantly along the cross-reef transect which has important implications for accurate assessment of wave dissipation across coral reef flats. Links between reef rugosity and coral genus were also observed and may indicate that some coral species are crucial in maintaining the structural diversity of coral reefs.
Dynamic interactions between the promoter and terminator regions of the mammalian BRCA1 gene.
Tan-Wong, Sue Mei; French, Juliet D; Proudfoot, Nicholas J; Brown, Melissa A
2008-04-01
The 85-kb breast cancer-associated gene BRCA1 is an established tumor suppressor gene, but its regulation is poorly understood. We demonstrate by gene conformation analysis in both human cell lines and mouse mammary tissue that gene loops are imposed on BRCA1 between the promoter, introns, and terminator region. Significantly, association between the BRCA1 promoter and terminator regions change upon estrogen stimulation and during lactational development. Loop formation is transcription-dependent, suggesting that transcriptional elongation plays an active role in BRCA1 loop formation. We show that the BRCA1 terminator region can suppress estrogen-induced transcription and so may regulate BRCA1 expression. Significantly, BRCA1 promoter and terminator interactions vary in different breast cancer cell lines, indicating that defects in BRCA1 chromatin structure may contribute to dysregulated expression of BRCA1 seen in breast tumors.
Unbundling in Current Broadband and Next-Generation Ultra-Broadband Access Networks
NASA Astrophysics Data System (ADS)
Gaudino, Roberto; Giuliano, Romeo; Mazzenga, Franco; Valcarenghi, Luca; Vatalaro, Francesco
2014-05-01
This article overviews the methods that are currently under investigation for implementing multi-operator open-access/shared-access techniques in next-generation access ultra-broadband architectures, starting from the traditional "unbundling-of-the-local-loop" techniques implemented in legacy twisted-pair digital subscriber line access networks. A straightforward replication of these copper-based unbundling-of-the-local-loop techniques is usually not feasible on next-generation access networks, including fiber-to-the-home point-to-multipoint passive optical networks. To investigate this issue, the article first gives a concise description of traditional copper-based unbundling-of-the-local-loop solutions, then focalizes on both next-generation access hybrid fiber-copper digital subscriber line fiber-to-the-cabinet scenarios and on fiber to the home by accounting for the mix of regulatory and technological reasons driving the next-generation access migration path, focusing mostly on the European situation.
Efficient laser noise reduction method via actively stabilized optical delay line.
Li, Dawei; Qian, Cheng; Li, Ye; Zhao, Jianye
2017-04-17
We report a fiber laser noise reduction method by locking it to an actively stabilized optical delay line, specifically a fiber-based Mach-Zehnder interferometer with a 10 km optical fiber spool. The fiber spool is used to achieve large arm imbalance. The heterodyne signal of the two arms converts the laser noise from the optical domain to several megahertz, and it is used in laser noise reduction by a phase-locked loop. An additional phase-locked loop is induced in the system to compensate the phase noise due to environmentally induced length fluctuations of the optical fiber spool. A major advantage of this structure is the efficient reduction of out-of-loop frequency noise, particularly at low Fourier frequency. The frequency noise reaches -30 dBc/Hz at 1 Hz, which is reduced by more than 90 dB compared with that of the laser in its free-running state.
Wise, Marcus B.; Thompson, Cyril V.
1998-01-01
An in-line gas monitor capable of accurate gas composition analysis in a continuous real time manner even under strong applied vacuum conditions operates by mixing an air sample with helium forming a sample gas in two complementary sample loops embedded in a manifold which includes two pairs of 3-way solenoid valves. The sample gas is then analyzed in an ion trap mass spectrometer on a continuous basis. Two valve drivers actuate the two pairs of 3-way valves in a reciprocating fashion, so that there is always flow through the in-line gas monitor via one or the other of the sample loops. The duty cycle for the two pairs of 3-way valves is varied by tuning the two valve drivers to a duty cycle typically between 0.2 to 0.7 seconds.
Rogers, Caroline S.; Miller, Jeff; Hubbard, Dennis K.; Rogers, Caroline S.; Lipps, Jere H.; Stanley, George D.
2016-01-01
What, exactly, is a coral reef? And how have the world’s reefs changed in the last several decades? What are the stressors undermining reef structure and function? Given the predicted effects of climate change, do reefs have a future? Is it possible to “manage” coral reefs for resilience? What can coral reef scientists contribute to improve protection and management of coral reefs? What insights can biologists and geologists provide regarding the persistence of coral reefs on a human timescale? What is reef change to a biologist… to a geologist?Clearly, there are many challenging questions. In this chapter, we present some of our thoughts on monitoring and management of coral reefs in US national parks in the Caribbean and western Atlantic based on our experience as members of monitoring teams. We reflect on the need to characterize and evaluate reefs, on how to conduct high-quality monitoring programs, and on what we can learn from biological and geological experiments and investigations. We explore the possibility that specific steps can be taken to “manage” coral reefs for greater resilience.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mazzullo, S.J.; Anderson-Underwood, K.E.; Burke, C.D.
Coral patch reefs are major components of Holocene platform carbonate facies systems in tropical and subtropical areas. The biotic composition, growth and relationship to sea level history, and diagenetic attributes of a representative Holocene patch reef ([open quotes]Elmer Reef[close quotes]) in the Mexico Rocks complex in northern Belize are described and compared to those of Holocene patch reefs in southern Belize. Elmer Reef has accumulated in shallow (2.5 m) water over the last 420 yr, under static sea level conditions. Rate of vertical construction is 0.3-0.5 m/100 yr, comparable to that of patch reefs in southern Belize. A pronounced coralmore » zonation exists across Elmer Reef, with Monastrea annularis dominating on its crest and Acropora cervicornis occurring on its windward and leeward flanks. The dominance of Montastrea on Elmer Reef is unlike that of patch reefs in southern Belize, in which this coral assumes only a subordinate role in reef growth relative to that of Acropora palmata. Elmer Reef locally is extensively biodegraded and marine, fibrous aragonite and some bladed high-magnesium calcite cements occur throughout the reef section, partially occluding corallites and interparticle pores in associated sands. Patch reefs in southern Belize have developed as catch-up and keep-up reefs in a transgressive setting. In contrast, the dominant mode of growth of Elmer Reef, and perhaps other patch reefs in Mexico Rocks, appears to be one of lateral rather than vertical accretion. This style of growth occurs in a static sea level setting where there is only limited accommodation space because of the shallowness of the water, and such reefs are referred to as [open quotes]expansion reefs[close quotes]. 39 refs., 8 figs., 2 tabs.« less
Storlazzi, C.D.; Ogston, A.S.; Bothner, Michael H.; Field, M.E.; Presto, M.K.
2004-01-01
The fringing coral reef off the south coast of Molokai, Hawaii is currently being studied as part of a US Geological Survey (USGS) multi-disciplinary project that focuses on geologic and oceanographic processes that affect coral reef systems. For this investigation, four instrument packages were deployed across the fringing coral reef during the summer of 2001 to understand the processes governing fine-grained terrestrial sediment suspension on the shallow reef flat (h=1m) and its advection across the reef crest and onto the deeper fore reef. The time-series measurements suggest the following conceptual model of water and fine-grained sediment transport across the reef: Relatively cool, clear water flows up onto the reef flat during flooding tides. At high tide, more deep-water wave energy is able to propagate onto the reef flat and larger Trade wind-driven waves can develop on the reef flat, thereby increasing sediment suspension. Trade wind-driven surface currents and wave breaking at the reef crest cause setup of water on the reef flat, further increasing the water depth and enhancing the development of depth-limited waves and sediment suspension. As the tide ebbs, the water and associated suspended sediment on the reef flat drains off the reef flat and is advected offshore and to the west by Trade wind- and tidally- driven currents. Observations on the fore reef show relatively high turbidity throughout the water column during the ebb tide. It therefore appears that high suspended sediment concentrations on the deeper fore reef, where active coral growth is at a maximum, are dynamically linked to processes on the muddy, shallow reef flat.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jordan, C.F. Jr.; Colgan, M.W.; Frost, S.H.
1990-05-01
Miocene reefs lived approximately within the latitudes of 27{degree}S to 48{degree}N compared with 25{degree}S and 32{degree}N for Holocene reefs. This expansion of reef-growing environments was the result of warm Miocene climates, aided by a eustatic sea level rise and tectonic styles that provided numerous foundations for reef development. The majority of Miocene reefs are found in three main areas: (1) Southeast Asia and the western Pacific, (2) the Mediterranean-Middle East, and (3) Middle America and the Caribbean. These regions, with their distinctive suites of coral and foramineral species, formed three biological provinces; respectively, they are the Indo-Pacific, Tethyan, and Westernmore » Atlantic provinces. Miocene reefs in Southeast Asia occur in several foreland basins as patch reef complexes on paleohighs and as barrier reefs in back-arc basins. Those reefs in the Mediterranean occur as fringing reefs, middle-shelf patch reefs, or as barrier reefs on the edges of tectonic blocks associated with Alpine thrust belts. Most reefs in the Caribbean grew on isolated open-ocean highs of volcanic origin. Miocene reefs display a diversity of framework types: (1) coral-encrusting, red algal boundstones with diverse coral faunas, (2) branching coral-encrusting, red algal boundstones with a limited Poritid fauna, (3) encrusting red algal boundstones. Barrier reef systems are especially rich in encrusting red algae and robust corals; grainstones are common as interbedded sediment. Patch reef complexes, however, display muddy carbonate textures, may have less diverse coral faunas, and commonly have larger foraminifera. The global distribution of Miocene reefs is important because (1) it provides insight into a paleoclimatic view of the earth during a major greenhouse stage and (2) Miocene buildups, such as the Arun (EUR of 14 tcf) and Bima fields (EUR of about 100 MMBO), are exploration targets.« less
NASA Astrophysics Data System (ADS)
Zhang, B.; Hou, Y. J.; Zhang, J.
2018-03-01
Aims: We aim to ascertain the physical parameters of a propagating wave over the solar disk detected by the Interface Region Imaging Spectrograph (IRIS). Methods: Using imaging data from the IRIS and the Solar Dynamic Observatory (SDO), we tracked bright spots to determine the parameters of a propagating transverse wave in active region (AR) loops triggered by activation of a filament. Deriving the Doppler velocity of Si IV line from spectral observations of IRIS, we have determined the rotating directions of active region loops which are relevant to the wave. Results: On 2015 December 19, a filament was located on the polarity inversion line of the NOAA AR 12470. The filament was activated and then caused a C1.1 two-ribbon flare. Between the flare ribbons, two rotation motions of a set of bright loops were observed to appear in turn with opposite directions. Following the end of the second rotation, a propagating wave and an associated transverse oscillation were detected in these bright loops. In 1400 Å channel, there was bright material flowing along the loops in a wave-like manner, with a period of 128 s and a mean amplitude of 880 km. For the transverse oscillation, we tracked a given loop and determine the transverse positions of the tracking loop in a limited longitudinal range. In both of 1400 Å and 171 Å channels, approximately four periods are distinguished during the transverse oscillation. The mean period of the oscillation is estimated as 143 s and the displacement amplitude as between 1370 km and 690 km. We interpret these oscillations as a propagating kink wave and obtain its speed of 1400 km s-1. Conclusions: Our observations reveal that a flare associated with filament activation could trigger a kink propagating wave in active region loops over the solar disk. Movies associated to Figs. 1-4 are available at http://https://www.aanda.org
Feasibility Investigation of a Two-Stage, Platform-Mounted Airdrop System
1975-07-01
apart. 2. The ends of the reefing lines were fab - ricated so that a 1-inch connector link (I’/N 101735) could be used to connect the ends of each...Configuration II on Tests No. 11 through IS. 20 i^^^P^ff^P^ BPP ^^^^IÜI ÜIJIÜ1.LLJJ1IIÜIIIU i * m- mm^mfmnrnKmrnrnm^ mw L-® G-ll Clevis. FSN 1670-090
Development and Testing of a Drogue Parachute System for X-37 ALTV/B-52H Separation
NASA Technical Reports Server (NTRS)
Whitmore, Stephen A.; Cobleigh, Brent R.; Jacobson, Steven R.; Jensen, Steven C.; Hennings, Elsa J.
2004-01-01
Multiple scenarios were identified in which the X-37 approach and landing test vehicle (ALTV) catastrophically recontacts the B-52H carrier aircraft after separation. The most cost-effective recontact risk mitigation is the prelaunch deployment of a drogue parachute that is released after the X-37 ALTV has safely cleared the B-52H. After release, a fully-inflated drogue parachute takes 30 min to reach ground and results in a large footprint that excessively restricts the days available for flight. To reduce the footprint, a passive collapse mechanism consisting of an elastic reefing line attached to the parachute skirt was developed. At flight loads the elastic is stretched, allowing full parachute inflation. After release, drag loads drop dramatically and the elastic line contracts, reducing the frontal drag area. A 50-percent drag reduction results in an approximately 75-percent ground footprint reduction. Eleven individual parachute designs were evaluated at flight load dynamic pressures in the High Velocity Airflow System (HIVAS) at the Naval Air Warfare Center (NAWC), China Lake, California. Various options for the elastic reefing system were also evaluated at HIVAS. Two best parachute designs were selected from HIVAS to be carried forward to flight test. Detailed HIVAS test results are presented in this report.
Development and Testing of a Drogue Parachute System for X-37 ALTV/B-52H Separation
NASA Technical Reports Server (NTRS)
Whitmore, Stephen A.; Cobleigh, Brent R.; Jacobson, Steven R.; Jensen, Steven C.; Hennings, Elsa J.
2004-01-01
Multiple scenarios were identified in which the X-37 approach and landing test vehicle (ALTV) catastrophically recontacts the B-52H carrier aircraft after separation. The most cost-effective recontact risk mitigation is the prelaunch deployment of a drogue parachute that is released after the X-37 ALTV has safely cleared the B-52H. After release, a fully-inflated drogue parachute takes 30 min to reach ground and results in a large footprint that excessively restricts the days available for flight. To reduce the footprint, a passive collapse mechanism consisting of an elastic reefing line attached to the parachute skirt was developed. At flight loads the elastic is stretched, allowing full parachute inflation. After release, drag loads drop dramatically and the elastic line contracts, reducing the frontal drag area. A 50 percent drag reduction results in an approximately 75 percent ground footprint reduction. Eleven individual parachute designs were evaluated at flight load dynamic pressures in the High Velocity Airflow System (HIVAS) at the Naval Air Warfare Center (NAWC), China Lake, California. Various options for the elastic reefing system were also evaluated at HIVAS. Two best parachute designs were selected from HIVAS to be carried forward to flight test. Detailed HIVAS test results are presented in this report.
Oyster reef restoration in the northern Gulf of Mexico: extent, methods and outcomes
LaPeyre, Megan K.; Furlong, Jessica N.; Brown, Laura A.; Piazza, Bryan P.; Brown, Ken
2014-01-01
Shellfish reef restoration to support ecological services has become more common in recent decades, driven by increasing awareness of the functional decline of shellfish systems. Maximizing restoration benefits and increasing efficiency of shellfish restoration activities would greatly benefit from understanding and measurement of system responses to management activities. This project (1) compiles a database of northern Gulf of Mexico inshore artificial oyster reefs created for restoration purposes, and (2) quantitatively assesses a subset of reefs to determine project outcomes. We documented 259 artificial inshore reefs created for ecological restoration. Information on reef material, reef design and monitoring was located for 94, 43 and 20% of the reefs identified. To quantify restoration success, we used diver surveys to quantitatively sample oyster density and substrate volume of 11 created reefs across the coast (7 with rock; 4 with shell), paired with 7 historic reefs. Reefs were defined as fully successful if there were live oysters, and partially successful if there was hard substrate. Of these created reefs, 73% were fully successful, while 82% were partially successful. These data highlight that critical information related to reef design, cost, and success remain difficult to find and are generally inaccessible or lost, ultimately hindering efforts to maximize restoration success rates. Maintenance of reef creation information data, development of standard reef performance measures, and inclusion of material and reef design testing within reef creation projects would be highly beneficial in implementing adaptive management. Adaptive management protocols seek specifically to maximize short and long-term restoration success, but are critically dependent on tracking and measuring system responses to management activities.
NASA Astrophysics Data System (ADS)
Woodroffe, Colin D.; Brooke, Brendan P.; Linklater, Michelle; Kennedy, David M.; Jones, Brian G.; Buchanan, Cameron; Mleczko, Richard; Hua, Quan; Zhao, Jian-xin
2010-08-01
Coral reefs track sea level and are particularly sensitive to changes in climate. Reefs are threatened by global warming, with many experiencing increased coral bleaching. Warmer sea surface temperatures might enable reef expansion into mid latitudes. Here we report multibeam sonar and coring that reveal an extensive relict coral reef around Lord Howe Island, which is fringed by the southernmost reef in the Pacific Ocean. The relict reef, in water depths of 25-50 m, flourished in early Holocene and covered an area more than 20 times larger than the modern reef. Radiocarbon and uranium-series dating indicates that corals grew between 9000 and 7000 years ago. The reef was subsequently drowned, and backstepped to its modern limited extent. This relict reef, with localised re-establishment of corals in the past three millennia, could become a substrate for reef expansion in response to warmer temperatures, anticipated later this century and beyond, if corals are able to recolonise its surface.
NASA Astrophysics Data System (ADS)
Bufarale, Giada; Collins, Lindsay B.; O'Leary, Michael J.; Stevens, Alexandra; Kordi, Moataz; Solihuddin, Tubagus
2016-07-01
The inner shelf Kimberley Bioregion of Northwest Australia is characterised by a macrotidal setting where prolific coral reefs growth as developed around a complex drowned landscape and is considered a biodiversity "hotspot". High-resolution shallow seismic studies were conducted across various reef settings in the Kimberley (Buccaneer Archipelago, north of Dampier Peninsula, latitude: between 16°40‧S and 16°00‧S) to evaluate stratigraphic evolution, interaction with different substrates, morphological patterns and distribution. Reef sites were chosen to assess most of the reef types present, particularly high intertidal planar reefs and fringing reefs. Reef internal acoustic reflectors were identified according to their shape, stratigraphic position and characteristics. Two main seismic horizons were identified marking the boundaries between Holocene reef (Marine Isotope Stage 1, MIS 1, last 12 ky), commonly 10-20 m thick, and MIS 5 (Last Interglacial, LIG, ~120 ky, up to 12 m thick) and Proterozoic rock foundation over which Quaternary reef growth occurred. Within the Holocene Reef unit, at least three minor internal reflectors, generally discontinuous, subparallel to the reef flat were recognised and interpreted as either growth hiatuses or a change of the coral framework or sediment matrix. The LIG reefs represent a new northernmost occurrence along the Western Australian coast. The research presented here achieved the first regional geophysical study of the Kimberley reefs. Subbottom profiles demonstrated that the surveyed reefs are characterised by a multi-stage reef buildup, indicating that coral growth occurred in the Kimberley during previous sea level highstands. The data show also that antecedent substrate and regional subsidence have contributed, too, in determining the amount of accommodation available for reef growth and controlling the morphology of the successive reef building stages. Moreover, the study showed that in spite of macrotidal conditions, high-turbidity and frequent high-energy cyclonic events, corals have exhibited prolific reef growth during the Holocene developing significant reef accretionary structures. As a result coral reefs have generating habitat complexity and species diversity in what is a biodiversity hotspot.
Stratigraphy and evolution of emerged Pleistocene reefs at the Red Sea coast of Sudan
NASA Astrophysics Data System (ADS)
Hamed, Basher; Bussert, Robert; Dominik, Wilhelm
2016-02-01
Emerged Pleistocene coral reefs constitute a prominent landform along the Red Sea coast of Sudan. They are well exposed with a thickness of up to 12 m and extend over a width of about 3 km parallel to the coastline. Four major reef units that represent different reef zones are distinguished. Unit 1 is located directly at the coastline and is assigned to the rock-reef rim, while unit 2 represents the reef-front zone. Unit 3 is attributed to the reef-flat zone and unit 4 to the back-reef zone. The stratigraphic position and age of the four units respectively the facies zones are based on field relationships and δ18O analysis. Results of δ18O analysis of coral, gastropod and bivalve samples were correlated to previous age dating of correlative reefs in Sudan and other parts of the Red Sea region. Estimation of reef ages was mainly based on δ18O values of the reef-front zone (unit 2) and the observed sedimentary succession of the reefs. δ18O values of two Porites coral samples from the reef-front zone strongly suggest equivalent ages of 120 and 122 ka that correspond to marine isotope stage MIS 5.5. Based on δ18O values and the field relationship to the reef-front zone, ages of reef-flat zone (unit 3) and back-reef zone (unit 4) could be assigned to MIS 9 and MIS 7 respectively. MIS 5.1 is suggested for the reef-rock rim (unit 1). The relationship of the reef zones to individual MIS might be explained by the predominance of a specific zone during a certain stage, while other facies were less well developed and/or later eroded by wave action. The reef unit most distal from the recent coastline formed during interglacial stage MIS 7, while former studies assign this unit to interglacial stage MIS 9. Unique flourishing, high diversity and excellent preservation of corals in the back-reef unit of MIS 7 reflect growth in troughs landward of the oldest reef-flat formed during previous interglacial stage MIS 9.
Mesopredator trophodynamics on thermally stressed coral reefs
NASA Astrophysics Data System (ADS)
Hempson, Tessa N.; Graham, Nicholas A. J.; MacNeil, M. Aaron; Hoey, Andrew S.; Almany, Glenn R.
2018-03-01
Ecosystems are becoming vastly modified through disturbance. In coral reef ecosystems, the differential susceptibility of coral taxa to climate-driven bleaching is predicted to shift coral assemblages towards reefs with an increased relative abundance of taxa with high thermal tolerance. Many thermally tolerant coral species are characterised by low structural complexity, with reduced habitat niche space for the small-bodied coral reef fishes on which piscivorous mesopredators feed. This study used a patch reef array to investigate the potential impacts of climate-driven shifts in coral assemblages on the trophodynamics of reef mesopredators and their prey communities. The `tolerant' reef treatment consisted only of coral taxa of low susceptibility to bleaching, while `vulnerable' reefs included species of moderate to high thermal vulnerability. `Vulnerable' reefs had higher structural complexity, and the fish assemblages that established on these reefs over 18 months had higher species diversity, abundance and biomass than those on `tolerant' reefs. Fish assemblages on `tolerant' reefs were also more strongly influenced by the introduction of a mesopredator ( Cephalopholis boenak). Mesopredators on `tolerant' reefs had lower lipid content in their muscle tissue by the end of the 6-week experiment. Such sublethal energetic costs can compromise growth, fecundity, and survivorship, resulting in unexpected population declines in long-lived mesopredators. This study provides valuable insight into the altered trophodynamics of future coral reef ecosystems, highlighting the potentially increased vulnerability of reef fish assemblages to predation as reef structure declines, and the cost of changing prey availability on mesopredator condition.
Brown, Laura A.; Furlong, Jessica N.; Brown, Kenneth M.; LaPeyre, Megan K.
2013-01-01
In the northern Gulf of Mexico (GOM), reefs built by eastern oysters, Crassostrea virginica, provide critical habitat within shallow estuaries, and recent efforts have focused on restoring reefs to benefit nekton and benthic macroinvertebrates. We compared nekton and benthic macroinvertebrate assemblages at historic, newly created (<5years) and old (>6years) shell and rock substrate reefs. Using crab traps, gill-nets, otter trawls, cast nets, and benthic macroinvertebrate collectors, 20 shallow reefs (<5m) in the northern GOM were sampled throughout the summer of 2011. We compared nekton and benthic assemblage abundance, diversity and composition across reef types. Except for benthic macroinvertebrate abundance, which was significantly higher on old rock reefs as compared to historic reefs, all reefs were similar to historic reefs, suggesting created reefs provide similar support of nekton and benthic assemblages as historic reefs. To determine refuge value of oyster structure for benthic macroinvertebrates compared to bare bottom, we tested preferences of juvenile crabs across depth and refuge complexity in the presence and absence of adult blue crabs (Callinectes sapidus). Juveniles were more likely to use deep water with predators present only when provided oyster structure. Provision of structural material to support and sustain development of benthic and mobile reef communities may be the most important factor in determining reef value to these assemblages, with biophysical characteristics related to reef location influencing assemblage patterns in areas with structure; if so, appropriately locating created reefs is critical.
Reef Education Evaluation: Environmental Knowledge and Reef Experience
ERIC Educational Resources Information Center
Stepath, Carl M.
2005-01-01
Background: The Reef education evaluation: environmental knowledge and reef experience report concerns PhD research about marine education, and the investigation of learning with high school students and the effect of coral reef monitoring marine experiential education interventions. The effectiveness of classroom learning and reef trips were…
Transequatorial loops interconnecting McMath regions 12472 and 12474
NASA Technical Reports Server (NTRS)
Svestka, Z.; Krieger, A. S.; Chase, R. C.; Howard, R.
1977-01-01
The paper reviews the life history of one transequatorial loop in a system observed in soft X-rays for at least 1.5 days and which interconnected a newly born active region with an old region. The birth of the selected loop is discussed along with properties of the interconnected active regions, sharpening and brightening of the loop, decay of the loop system, and physical relations between the interconnected regions. It is concluded that: (1) the loop was most probably born via reconnection of magnetic-field lines extending from the two active regions toward the equator, which occurred later than 33 hr after the younger region was born; (2) the fully developed interconnection was composed of several loops, all of which appeared to be rooted in a spotless magnetic hill of preceding northern polarity but were spread over two separate spotty regions of southern polarity in the magnetically complex new region; (3) the loop electron temperature increased from 2.1 million to 3.1 million K in one to three hours when the loop system brightened; and (4) the loops became twisted during the brightening, possibly due to their rise in the corona while remaining rooted in moving magnetic features in the younger region.
Coordinated gripping of substrate by subunits of a AAA+ proteolytic machine
Iosefson, Ohad; Nager, Andrew R.; Baker, Tania A.; Sauer, Robert T.
2014-01-01
Hexameric AAA+ unfoldases of ATP-dependent proteases and protein-remodeling machines use conserved loops that line the axial pore to apply force to substrates during the mechanical processes of protein unfolding and translocation. Whether loops from multiple subunits act independently or coordinately in these processes is a critical aspect of mechanism but is currently unknown for any AAA+ machine. By studying covalently linked hexamers of the E. coli ClpX unfoldase bearing different numbers and configurations of wild-type and mutant pore loops, we show that loops function synergistically, with the number of wild-type loops required for efficient degradation depending upon the stability of the protein substrate. Our results support a mechanism in which a power stroke initiated in one subunit of the ClpX hexamer results in the concurrent movement of all six pore loops, which coordinately grip and apply force to the substrate. PMID:25599533
Encouraging Proximal Relations: Queensland High School Students Go to the Reef
ERIC Educational Resources Information Center
Stepath, Carl; Whitehouse, Hilary
2006-01-01
Background: This article concerns learning with high school students and the effect of snorkeling and coral reef monitoring at the Great Barrier Reef, Australia. The effectiveness of classroom learning, student-reef relationships and reef trips were investigated. Purpose: This paper presents selected student accounts of reef educational…
Simple way to calculate a UV-finite one-loop quantum energy in the Randall-Sundrum model
NASA Astrophysics Data System (ADS)
Altshuler, Boris L.
2017-04-01
The surprising simplicity of Barvinsky-Nesterov or equivalently Gelfand-Yaglom methods of calculation of quantum determinants permits us to obtain compact expressions for a UV-finite difference of one-loop quantum energies for two arbitrary values of the parameter of the double-trace asymptotic boundary conditions. This result generalizes the Gubser and Mitra calculation for the particular case of difference of "regular" and "irregular" one-loop energies in the one-brane Randall-Sundrum model. The approach developed in the paper also allows us to get "in one line" the one-loop quantum energies in the two-brane Randall-Sundrum model. The relationship between "one-loop" expressions corresponding to the mixed Robin and to double-trace asymptotic boundary conditions is traced.
The Evolution of Transition Region Loops Using IRIS and AIA
NASA Technical Reports Server (NTRS)
Winebarger, Amy R.; DePontieu, Bart
2014-01-01
Over the past 50 years, the model for the structure of the solar transition region has evolved from a simple transition layer between the cooler chromosphere to the hotter corona to a complex and diverse region that is dominated by complete loops that never reach coronal temperatures. The IRIS slitjaw images show many complete transition region loops. Several of the "coronal" channels in the SDO AIA instrument include contributions from weak transition region lines. In this work, we combine slitjaw images from IRIS with these channels to determine the evolution of the loops. We develop a simple model for the temperature and density evolution of the loops that can explain the simultaneous observations. Finally, we estimate the percentage of AIA emission that originates in the transition region.
Effect of Phase Shift from Corals to Zoantharia on Reef Fish Assemblages
Cruz, Igor C. S.; Loiola, Miguel; Albuquerque, Tiago; Reis, Rodrigo; de Anchieta C. C. Nunes, José; Reimer, James D.; Mizuyama, Masaru; Kikuchi, Ruy K. P.; Creed, Joel C.
2015-01-01
Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated. PMID:25629532
The structure and composition of Holocene coral reefs in the Middle Florida Keys
Toth, Lauren T.; Stathakopoulos, Anastasios; Kuffner, Ilsa B.
2016-07-21
The Florida Keys reef tract (FKRT) is the largest coral-reef ecosystem in the continental United States. The modern FKRT extends for 362 kilometers along the coast of South Florida from Dry Tortugas National Park in the southwest, through the Florida Keys National Marine Sanctuary (FKNMS), to Fowey Rocks reef in Biscayne National Park in the northeast. Most reefs along the FKRT are sheltered by the exposed islands of the Florida Keys; however, large channels are located between the islands of the Middle Keys. These openings allow for tidal transport of water from Florida Bay onto reefs in the area. The characteristics of the water masses coming from Florida Bay, which can experience broad swings in temperature, salinity, nutrients, and turbidity over short periods of time, are generally unfavorable or “inimical” to coral growth and reef development.Although reef habitats are ubiquitous throughout most of the Upper and Lower Keys, relatively few modern reefs exist in the Middle Keys most likely because of the impacts of inimical waters from Florida Bay. The reefs that are present in the Middle Keys generally are poorly developed compared with reefs elsewhere in the region. For example, Acropora palmata has been the dominant coral on shallow-water reefs in the Caribbean over the last 1.5 million years until populations of the coral declined throughout the region in recent decades. Although A. palmata was historically abundant in the Florida Keys, it was conspicuously absent from reefs in the Middle Keys. Instead, contemporary reefs in the Middle Keys have been dominated by occasional massive (that is, boulder or head) corals and, more often, small, non-reef-building corals.Holocene reef cores have been collected from many locations along the FKRT; however, despite the potential importance of the history of reefs in the Middle Florida Keys to our understanding of the environmental controls on reef development throughout the FKRT, there are currently no published records of the Holocene history of reefs in the region. The objectives of the present study were to (1) provide general descriptions of unpublished core records from Alligator Reef and (2) collect and describe new Holocene reef cores from two additional locations in the Middle Keys: Sombrero and Tennessee Reefs.
Seismic and Biological Sources of Ambient Ocean Sound
NASA Astrophysics Data System (ADS)
Freeman, Simon Eric
Sound is the most efficient radiation in the ocean. Sounds of seismic and biological origin contain information regarding the underlying processes that created them. A single hydrophone records summary time-frequency information from the volume within acoustic range. Beamforming using a hydrophone array additionally produces azimuthal estimates of sound sources. A two-dimensional array and acoustic focusing produce an unambiguous two-dimensional `image' of sources. This dissertation describes the application of these techniques in three cases. The first utilizes hydrophone arrays to investigate T-phases (water-borne seismic waves) in the Philippine Sea. Ninety T-phases were recorded over a 12-day period, implying a greater number of seismic events occur than are detected by terrestrial seismic monitoring in the region. Observation of an azimuthally migrating T-phase suggests that reverberation of such sounds from bathymetric features can occur over megameter scales. In the second case, single hydrophone recordings from coral reefs in the Line Islands archipelago reveal that local ambient reef sound is spectrally similar to sounds produced by small, hard-shelled benthic invertebrates in captivity. Time-lapse photography of the reef reveals an increase in benthic invertebrate activity at sundown, consistent with an increase in sound level. The dominant acoustic phenomenon on these reefs may thus originate from the interaction between a large number of small invertebrates and the substrate. Such sounds could be used to take census of hard-shelled benthic invertebrates that are otherwise extremely difficult to survey. A two-dimensional `map' of sound production over a coral reef in the Hawaiian Islands was obtained using two-dimensional hydrophone array in the third case. Heterogeneously distributed bio-acoustic sources were generally co-located with rocky reef areas. Acoustically dominant snapping shrimp were largely restricted to one location within the area surveyed. This distribution of sources could reveal small-scale spatial ecological limitations, such as the availability of food and shelter. While array-based passive acoustic sensing is well established in seismoacoustics, the technique is little utilized in the study of ambient biological sound. With the continuance of Moore's law and advances in battery and memory technology, inferring biological processes from ambient sound may become a more accessible tool in underwater ecological evaluation and monitoring.
Habitat, Fauna, and Conservation of Florida's Deep-Water Coral Reefs
NASA Astrophysics Data System (ADS)
Reed, J. K.; Pomponi, S. A.; Messing, C. G.; Brooke, S.
2008-05-01
Various types of deep-water coral habitats are common off the southeastern United States from the Blake Plateau through the Straits of Florida to the eastern Gulf of Mexico. Expeditions in the past decade with the Johnson-Sea- Link manned submersibles, ROVs, and AUVs have discovered, mapped and compiled data on the status, distribution, habitat, and biodiversity for many of these relatively unknown deep-sea coral ecosystems. We have discovered over three hundred, high relief (15-152-m tall) coral mounds (depth 700-800 m) along the length of eastern Florida (700 km). The north Florida sites are rocky lithoherms, whereas the southern sites are primarily classic coral bioherms, capped with dense 1-2 m tall thickets of Lophelia pertusa and Enallopsammia profunda. Off southeastern Florida, the Miami Terrace escarpment (depth 300-600 m) extends nearly 150 km as a steep, rocky slope of Miocene-age phosphoritic limestone, which provides habitat for a rich biodiversity of fish and benthic invertebrates. Off the Florida Keys, the Pourtalès Terrace (depth 200- 460 m) has extensive high-relief bioherms and numerous deep-water sinkholes to depths of 250-610 m and diameters up to 800 m. The dominant, deep-water, colonial scleractinian corals in this region include Oculina varicosa, L. pertusa, E. profunda, Madrepora oculata, and Solenosmilia variabilis. Other coral species include hydrozoans (Stylasteridae), bamboo octocorals (Isididae), numerous other gorgonians, and black corals (Antipatharia). These structure-forming taxa provide habitat and living space for a relatively unknown but biologically rich and diverse community of crustaceans, mollusks, echinoderms, polychaete and sipunculan worms, and associated fishes. We have identified 142 taxa of benthic macro-invertebrates, including 66 Porifera and 57 Cnidaria. Nearly 100 species of fish have been identified to date in association with these deep-water coral habitats. Paull et al. (2000) estimated that over 40,000 individual deep-water lithoherms may occur on the Blake Plateau and Straits of Florida, perhaps exceeding the areal extent of all the shallow-water reefs of the southeastern U.S. Our research program has provided data on the status of knowledge concerning these deep-reef habitats to the South Atlantic Fishery Management Council (SAFMC). Currently pending is a proposal by the SAFMC for a deep- water coral Habitat Area of Particular Concern (HAPC) that would extend from North Carolina to south Florida (78,888 km2) to protect these diverse and irreplaceable resources from destructive fishing activities such as bottom trawling. Deep-water reefs worldwide have been severely impacted by bottom trawling, including the deep-water Oculina coral reefs off central eastern Florida, which are structurally similar to the Lophelia reefs. Over a 30-year period, up to 99% of unprotected portions of the Oculina reefs were destroyed by rock shrimp trawling, whereas reefs designated as the Oculina HAPC in 1984 were protected from trawling and long-lines and are still relatively healthy. Numerous fisheries may target the deep-water Lophelia reef habitat including royal red shrimp, golden crab, and various fin fish.
NASA Astrophysics Data System (ADS)
Shoham, Erez; Benayahu, Yehuda
2017-03-01
Mesophotic coral-reef ecosystems (MCEs), which comprise the light-dependent communities of corals and other organisms found at depths between 30 and 150 m, have received very little study to date. However, current technological advances, such as remotely operated vehicles and closed-circuit rebreather diving, now enable their thorough investigation. Following the reef-building stony corals, octocorals are the second most common benthic component on many shallow reefs and a major component on deep reefs, the Red Sea included. This study is the first to examine octocoral community features on upper MCEs based on species-level identification and to compare them with the shallower reef zones. The study was carried out at Eilat (Gulf of Aqaba, northern Red Sea), comparing octocoral communities at two mesophotic reefs (30-45 m) and two shallow reef zones (reef flat and upper fore-reef) by belt transects. A total of 30 octocoral species were identified, with higher species richness on the upper MCEs compared to the shallower reefs. Although the MCEs were found to host a higher number of species than the shallower reefs, both featured a similar diversity. Each reef zone revealed a unique octocoral species composition and distinct community structure, with only 16% of the species shared by both the MCEs and the shallower reefs. This study has revealed an almost exclusive dominance of zooxanthellate species at the studied upper MCE reefs, thus indicating an adequate light regime for photosynthesis there. The findings should encourage similar studies on other reefs, aimed at understanding the spatiotemporal features and ecological role of octocorals in reef ecosystems down to the deepest limit of the MCEs.
Wave Dissipation on Low- to Super-Energy Coral Reefs
NASA Astrophysics Data System (ADS)
Harris, D. L.
2016-02-01
Coral reefs are valuable, complex and bio-diverse ecosystems and are also known to be one of the most effective barriers to swell events in coastal environments. Previous research has found coral reefs to be remarkably efficient in removing most of the wave energy during the initial breaking and transformation on the reef flats. The rate of dissipation is so rapid that coral reefs have been referred to as rougher than any known coastal barrier. The dissipation of wave energy across reef flats is crucial in maintaining the relatively low-energy conditions in the back reef and lagoonal environments providing vital protection to adjacent beach or coastal regions from cyclone and storm events. A shift in the regulation of wave energy by reef flats could have catastrophic consequences ecologically, socially, and economically. This study examined the dissipation of wave energy during two swell events in Tahiti and Moorea, French Polyesia. Field sites were chosen in varying degrees of exposure and geomorphology from low-energy protected sites (Tiahura, Moorea) to super-energy sites (Teahupo'o, Tahiti). Waves were measured during two moderate to large swell events in cross reef transects using short-term high-resolution pressure transducers. Wave conditions were found to be similar in all back reef locations despite the very different wave exposure at each reef site. However, wave conditions on the reef flats were different and mirrored the variation in wave exposure with depth over the reef flat the primary regulator of reef flat wave height. These results indicate that coral reef flats evolve morphodynamically with the wave climate, which creates coral reef geomorphologies capable of dissipating wave energy that results in similar back reef wave conditions regardless of the offshore wave climate.
NASA Astrophysics Data System (ADS)
Black, Kerry P.
1993-03-01
Reef-scale, eddy-resolving numerical models are applied to discriminate between local trapping of neutrally buoyant passive material coming from a natal reef versus trapping of this material on reefs downstream. A hydrodynamic model is coupled with a Lagrangian (nongridded) dispersal simulation to map the movement of material such as passive larvae within and between natural reefs. To simplify the interpretation, a number of schematic reef shapes, sizes and spacings were devised to represent the most common cases typifying Australia's Great Barrier Reef. Prior investigations have shown that coral reefs on the Great Barrier Reef may retain material for times equivalent to the pelagic dispersal period of many species. This paper explores whether larvae are more likely to settle on the natal reef, settle downstream or fail to settle at all. The modelling neglects active larval behaviour and treats the vertically well-mixed case of notionally weightless particles only. The crown-of-thorns starfish larvae with a pelagic dispersal period of at least 10 days are one example of this case. Larvae are most likely to be found near the natal reef rather than its downstream neighbour, mostly because the currents take the vertically well-mixed material around, rather than onto, the downstream reef. Of all the simulations, the highest numbers were found on natal reefs (e.g. 8% after 10 days) while downstream numbers mostly varied between 0 and 1% after 10 days. Particle numbers equalised only when spacing between the two reefs was less than the reef length (6 km), or when the downstream reef was in the direct path of the larval stream.
Coral identity underpins architectural complexity on Caribbean reefs.
Alvarez-Filip, Lorenzo; Dulvy, Nicholas K; Côte, Isabelle M; Watkinson, Andrew R; Gill, Jennifer A
2011-09-01
The architectural complexity of ecosystems can greatly influence their capacity to support biodiversity and deliver ecosystem services. Understanding the components underlying this complexity can aid the development of effective strategies for ecosystem conservation. Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic change is shifting communities toward reefs dominated by stress-resistant coral species, which are often less architecturally complex. With the regionwide decline in reef fish abundance, it is becoming increasingly important to understand changes in coral reef community structure and function. We quantify the influence of coral composition, diversity, and morpho-functional traits on the architectural complexity of reefs across 91 sites at Cozumel, Mexico. Although reef architectural complexity increases with coral cover and species richness, it is highest on sites that are low in taxonomic evenness and dominated by morpho-functionally important, reef-building coral genera, particularly Montastraea. Sites with similar coral community composition also tend to occur on reefs with very similar architectural complexity, suggesting that reef structure tends to be determined by the same key species across sites. Our findings provide support for prioritizing and protecting particular reef types, especially those dominated by key reef-building corals, in order to enhance reef complexity.
NASA Astrophysics Data System (ADS)
Levy, J.; Franklin, E. C.; Hunter, C. L.
2016-12-01
Coral reefs are biodiversity hotspots that are vital to the function of global economic and biological processes. Coral bleaching is a significant contributor to the global decline of reefs and can impact an expansive reef area over short timescales. In order to understand the dynamics of coral bleaching and how these stress events impact reef ecosystems, it is important to conduct rapid bleaching surveys at functionally important spatial scales. Due to the inherent heterogeneity, size, and in some cases, remoteness of coral reefs, it is difficult to routinely monitor coral bleaching dynamics before, during, and after bleaching. Additionally, current in situ survey methods only collect snippets of discrete reef data over small reef areas, which are unable to accurately represent the reef as a whole. We present a new technique using small unmanned aerial systems (sUAS) as cost effective, efficient monitoring tools that target small to intermediate-scale reef dynamics to understand the spatial distribution of bleached coral colonies during the 2015 bleaching event on patch reefs in Kaneohe Bay, Oahu. Overlapping low altitude aerial images were collected at four reefs during the bleaching period and processed using Structure-from-Motion techniques to produce georeferenced and spatially accurate orthomosaics of complete reef areas. Mosaics were analyzed using manual and heuristic neural network classification schemes to identify comprehensive populations of bleached and live coral on each patch reef. We found that bleached colonies had random and clumped distributions on patch reefs in Kaneohe Bay depending on local environmental conditions. Our work demonstrates that sUAS provide a low cost, efficient platform that can rapidly and repeatedly collect high-resolution imagery (1 cm/pixel) and map large areas of shallow reef ecosystems (5 hectares). This study proves the feasibility of utilizing sUAS as a tool to collect spatially rich reef data that will provide reef scientists a new perspective on meso-scale coral reef dynamics. We envision that similar low altitude aerial surveys will be incorporated as a standard component of shallow-water reef studies, especially on reefs too dangerous or remote for in situ surveys.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cross, S.L.; Lighty, R.G.
Coral-rudist reefs of the Lower Cretaceous Mural limestone, southeastern Arizona, show a pronounced relationship between specific reef facies, primary porosity, and early submarine diagenesis. These large open-shelf reefs differ from the well-studied low-relief rudist buildups, and provide an alternate analog for many Cretaceous reef reservoirs. Arizona buildups have diverse corals, high depositional relief, and a well-developed facies zonation from fore reef to back reef: skeletal grainstone talus, muddy fore reef with branching and lamellar corals, massive reef crest with abundant lamellar corals and sandy matrix, protected thickets of delicate branching corals and large rudist mounds, and a wide sediment apronmore » of well-washed coral, rudist, and benthic foraminiferal sands. These well-exposed outcrops permit a detailed facies comparison of primary interparticle porosity. Porosity as high as 40% in grainstones was occluded by later subsurface cements. Reef-framework interparticle porosity was negligible because fore-reef coral and back-reef rudist facies were infilled by muds, and high-energy reef-crest frameworks were filled by peloidal submarine cement crusts and muddy skeletal sands. These thick crusts coated lamellar corals in cryptic and open reef-crest areas, and are laminated with ripple and draped bed forms that suggest current influence. Similar peloidal crusts and laminated textures are common magnesium-calcite submarine cement features in modern reefs. By documenting specific facies control on early cementation and textural variability, patterns of late-stage subsurface diagenesis and secondary porosity may be more easily explained for Cretaceous reef reservoirs. Significant primary porosity might be retained between sands in back-reef facies and within coral skeletons.« less
NASA Astrophysics Data System (ADS)
Mukharror, Darmawan Ahmad; Tiara Baiti, Isnaini; Ichsan, Muhammad; Pridina, Niomi; Triutami, Sanny
2017-10-01
Despite increasing academic research citation on biology, abundance, and the behavior of the blacktip reef sharks, the influence of reef fish population on the density of reef sharks: Carcharhinus melanopterus and Triaenodon obesus population in its habitat were largely unassessed. This present study examined the correlation between abundance of reef fishes family/species with the population of reef sharks in Southern Waters of Morotai Island. The existence of reef sharks was measured with the Audible Stationary Count (ASC) methods and the abundance of reef fishes was surveyed using Underwater Visual Census (UVC) combined with Diver Operated Video (DOV) census. The coefficient of Determination (R2) was used to investigate the degree of relationships between sharks and the specific reef fishes species. The research from 8th April to 4th June 2015 showed the strong positive correlations between the existence of reef sharks with abundance of reef fishes. The correlation values between Carcharhinus melanopterus/Triaenodon obesus with Chaetodon auriga was 0.9405, blacktip/whitetip reef sharks versus Ctenochaetus striatus was 0.9146, and Carcharhinus melanopterus/Triaenodon obesus to Chaetodon kleinii was 0.8440. As the shark can be worth more alive for shark diving tourism than dead in a fish market, the abundance of these reef fishes was important as an early indication parameter of shark existence in South Water of Morotai Island. In the long term, this highlights the importance of reef fishes abundance management in Morotai Island’s Waters to enable the establishment of appropriate and effective reef sharks conservation.
Manzello, Derek P; Kleypas, Joan A; Budd, David A; Eakin, C Mark; Glynn, Peter W; Langdon, Chris
2008-07-29
Ocean acidification describes the progressive, global reduction in seawater pH that is currently underway because of the accelerating oceanic uptake of atmospheric CO(2). Acidification is expected to reduce coral reef calcification and increase reef dissolution. Inorganic cementation in reefs describes the precipitation of CaCO(3) that acts to bind framework components and occlude porosity. Little is known about the effects of ocean acidification on reef cementation and whether changes in cementation rates will affect reef resistance to erosion. Coral reefs of the eastern tropical Pacific (ETP) are poorly developed and subject to rapid bioerosion. Upwelling processes mix cool, subthermocline waters with elevated pCO(2) (the partial pressure of CO(2)) and nutrients into the surface layers throughout the ETP. Concerns about ocean acidification have led to the suggestion that this region of naturally low pH waters may serve as a model of coral reef development in a high-CO(2) world. We analyzed seawater chemistry and reef framework samples from multiple reef sites in the ETP and found that a low carbonate saturation state (Omega) and trace abundances of cement are characteristic of these reefs. These low cement abundances may be a factor in the high bioerosion rates previously reported for ETP reefs, although elevated nutrients in upwelled waters may also be limiting cementation and/or stimulating bioerosion. ETP reefs represent a real-world example of coral reef growth in low-Omega waters that provide insights into how the biological-geological interface of coral reef ecosystems will change in a high-CO(2) world.
NASA Astrophysics Data System (ADS)
Adrim, Mohammad; Hutomo, Malikusworo
Observations on chaetodontid fishes were made by applying a visual census technique at 13 coral reef locations in the Flores Sea region in October and November 1984. These observations were made along 50 m transect lines, parallel to the shore or the reef edge at depths between 3 to 12 m. Twenty-three species of Chaetodontidae were observed, representing three genera: Chaetodon (20 species), Heniochus (2 species) and Forcipiger (1 species). Chaetodon kleini, C. trifasciatus, C. melannotus and C. baronessa proved to be the most abundant species, and among them C. kleini and C. trifasciatus were the most widely distributed ones. Chaetodon semeion and C. mertensi were the rarest species. The greatest number of individuals (77) was counted at station 4.268 near Tanjung Burung, Sumbawa, while the greatest number of species (14) was observed at station 4.257, north of Komodo. The lowest number of individuals (17) was counted at station 4.175 near P. Bahuluang, Salayer, while station 4.251 near Teluk Slawi, Komodo, was inhabited by the smallest numbver of species (2). Numerical classification by using the Bray Curtis dissimilarity index resulted in three groups of entities. The first group was characterized by predomination of C. kleini and the second by predomination of C. melannotus. The third one was a loose group not characterized by any predominant species. The analyses indicated that the similarities of the chaetodontid communities between locations are not related to the distance between them, but rather to habitat conditions. For example predomination of C. melannotus is strongly related to the predomination of soft coral. Compared to other areas of Indonesia, e.g. Bali, Seribu Islands, Batam, Sunda Strait, and Ambon Bay, the Flores Sea reefs have a more abundant and more diverse chaetodontid fauna.
Linear quadratic regulators with eigenvalue placement in a specified region
NASA Technical Reports Server (NTRS)
Shieh, Leang S.; Dib, Hani M.; Ganesan, Sekar
1988-01-01
A linear optimal quadratic regulator is developed for optimally placing the closed-loop poles of multivariable continuous-time systems within the common region of an open sector, bounded by lines inclined at + or - pi/2k (k = 2 or 3) from the negative real axis with a sector angle of pi/2 or less, and the left-hand side of a line parallel to the imaginary axis in the complex s-plane. The design method is mainly based on the solution of a linear matrix Liapunov equation, and the resultant closed-loop system with its eigenvalues in the desired region is optimal with respect to a quadratic performance index.
Vortex reconnection rate, and loop birth rate, for a random wavefield
NASA Astrophysics Data System (ADS)
Hannay, J. H.
2017-04-01
A time dependent, complex scalar wavefield in three dimensions contains curved zero lines, wave ‘vortices’, that move around. From time to time pairs of these lines contact each other and ‘reconnect’ in a well studied manner, and at other times tiny loops of new line appear from nowhere (births) and grow, or the reverse, existing loops shrink and disappear (deaths). These three types are known to be the only generic events. Here the average rate of their occurrences per unit volume is calculated exactly for a Gaussian random wavefield that has isotropic, stationary statistics, arising from a superposition of an infinity of plane waves in different directions. A simplifying ‘axis fixing’ technique is introduced to achieve this. The resulting formulas are proportional to the standard deviation of angular frequencies, and depend in a simple way on the second and fourth moments of the power spectrum of the plane waves. Reconnections turn out to be more common than births and deaths combined. As an expository preliminary, the case of two dimensions, where the vortices are points, is studied and the average rate of pair creation (and likewise destruction) per unit area is calculated.
NASA Astrophysics Data System (ADS)
Jernsletten, J. A.
2005-05-01
Introduction: The purpose of this study is to evaluate the use of (diffusive) Time Domain Electromagnetics (TEM) for sounding of subsurface water in conductive Mars analog environments. To provide a baseline for such studies, I show data from two field studies: 1) Diffusive sounding data (TEM) from Pima County, Arizona; and 2) Shallower sounding data using the Fast-Turnoff TEM method from Peña de Hierro in the Rio Tinto region of Spain. The latter is data from work conducted under the auspices of the Mars Analog Research and Technology Experiment (MARTE). Pima County TEM Survey: A TEM survey was carried out in Pima County, Arizona, in January 2003. Data was collected using 100 m Tx loops and a ferrite-cored magnetic coil Rx antenna, and processed using commercial software. The survey used a 16 Hz sounding frequency, which is sensitive to slightly salty groundwater. Prominent features in the data from Arizona are the ~500 m depth of investigation and the ~120 m depth to the water table, confirmed by data from four USGS test wells surrounding the field area. Note also the conductive (~20-40 ω m) clay-rich soil above the water table. Rio Tinto Fast-Turnoff TEM Survey: During May and June of 2003, a Fast-Turnoff (early time) TEM survey was carried out at the Peña de Hierro field area of the MARTE project, near the town of Nerva, Spain. Data was collected using 20 m and 40 m Tx loop antennae and 10 m loop Rx antennae, with a 32 Hz sounding frequency. Data from Line 4 (of 16) from this survey, collected using 40 m Tx loops, show ~200 m depth of investigation and a conductive high at ~90 m depth below Station 20 (second station of 10 along this line). This is the water table, matching the 431 m MSL elevation of the nearby pit lake. The center of the "pileup" below Station 60 is spatially coincident with the vertical fault plane located here. Data from Line 15 and Line 14 of the Rio Tinto survey, collected using 20 m Tx loops, achieve ~50 m depth of investigation and show conductive highs at ~15 m depth below Station 50 (Line 15) and Station 30 (Line 14), interpreted as subsurface water flow under mine tailings matching surface flows seen coming out from under the tailings, and shown on maps. Conclusions: Results from the Pima County TEM survey were in good agreement with control data from the four USGS test wells located around the field area. This survey also achieved very acceptable 500+ m depths of investigation. Both of the interpretations from Rio Tinto data (Line 4, and Lines 15 & 14) were confirmed by preliminary results from the MARTE ground truth drilling campaign carried out in September and October 2003. Drill Site 1 was moved ~50 m based on recommendations built on data from Line 15 and Line 14 of the Fast-Turnoff TEM survey.
A dynamic flare with anomalously dense flare loops
NASA Technical Reports Server (NTRS)
Svestka, Z.; Fontenla, J. M.; Machado, M. E.; Martin, S. F.; Neidig, D. F.
1986-01-01
The dynamic flare of November 6, 1980 developed a rich system of growing loops which could be followed in H-alpha for 1.5 hours. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of b-values for a hydrogen atom reveal that this requires electron densities in the loops to be close to 10 to the 12th per cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th per cu cm if no nonthermal motions were present. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density a loop would cool through radiation from 10 to the 7th K to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, the density must have been significantly smaller when the loops were formed and the flare loops were apparently both shrinking and becoming denser while cooling.
2017-03-16
When an active region rotated over to the edge of the sun, it presented us with a nice profile view of its elongated loops stretching and swaying above it (Mar. 8-9, 2017). These loops are actually charged particles (made visible in extreme ultraviolet light) swirling along the magnetic field lines of the active region. The video covers about 30 hours of activity. Also of note is a darker twisting mass of plasma to the left of the active region being pulled and spun about by magnetic forces. Video is available at http://photojournal.jpl.nasa.gov/catalog/PIA21562
Project O.R.B (Operation Reef Ball): Creating Artificial Reefs, Educating the Community
NASA Astrophysics Data System (ADS)
Phipps, A.
2012-04-01
The Project O.R.B. (Operation Reef Ball) team at South Plantation High School's Everglades Restoration & Environmental Science Magnet Program is trying to help our ailing south Florida coral reefs by constructing, deploying, and monitoring designed artificial reefs. Students partnered with the Reef Ball Foundation, local concrete companies, state parks, Girl Scouts, Sea Scouts, local universities and environmental agencies to construct concrete reef balls, each weighing approximately 500 lbs (227 kg). Students then deployed two artificial reefs consisting of over 30 concrete reef balls in two sites previously permitted for artificial reef deployment. One artificial reef was placed approximately 1.5 miles (2.4 km) offshore of Golden Beach in Miami-Dade County with the assistance of Florida Atlantic University and their research vessel. A twin reef was deployed at the mouth of the river in Oleta River State Park in Miami. Monitoring and maintenance of the sites is ongoing with semi-annual reports due to the Reef Ball Foundation and DERM (Department of Environmental Resource Management) of Miami-Dade County. A second goal of Project O.R.B. is aligned with the Florida Local Action Strategy, the Southeast Florida Coral Reef Initiative, and the U.S. Coral Reef Task Force, all of which point out the importance of awareness and education as key components to the health of our coral reefs. Project O.R.B. team members developed and published an activity book targeting elementary school students. Outreach events incorporate cascade learning where high school students teach elementary and middle school students about various aspects of coral reefs through interactive "edu-tainment" modules. Attendees learn about water sampling, salinity, beach erosion, surface runoff, water cycle, ocean zones, anatomy of coral, human impact on corals, and characteristics of a well-designed artificial reef. Middle school students snorkel on the artificial reef to witness first-hand the success of this artificial reef. Over 3,000 students have been reached through the educational outreach endeavors of Project O.R.B. This successful STEM project models the benefits of partnerships with universities, local K-12 public schools and community conservation organizations and provides students with authentic learning experiences. Students are able to have a positive impact on their local coral reef environment, their peers and their community through this comprehensive service-learning project.
Reef Development on Artificial Patch Reefs in Shallow Water of Panjang Island, Central Java
NASA Astrophysics Data System (ADS)
Munasik; Sugiyanto; Sugianto, Denny N.; Sabdono, Agus
2018-02-01
Reef restoration methods are generally developed by propagation of coral fragments, coral recruits and provide substrate for coral attachment using artificial reefs (ARs). ARs have been widely applied as a tool for reef restoration in degraded natural reefs. Successful of coral restoration is determined by reef development such as increasing coral biomass, natural of coral recruits and fauna associated. Artificial Patch Reefs (APRs) is designed by combined of artificial reefs and coral transplantation and constructed by modular circular structures in shape, were deployed from small boats by scuba divers, and are suitable near natural reefs for shallow water with low visibility of Panjang Island, Central Java. Branching corals of Acropora aspera, Montipora digitata and Porites cylindrica fragments were transplanted on to each module of two units of artificial patch reefs in different periods. Coral fragments of Acropora evolved high survival and high growth, Porites fragments have moderate survival and low growth, while fragment of Montipora show in low survival and moderate growth. Within 19 to 22 months of APRs deployment, scleractinian corals were recruited on the surface of artificial patch reef substrates. The most recruits abundant was Montastrea, followed by Poritids, Pocilloporids, and Acroporids. We conclude that artificial patch reefs with developed by coral fragments and natural coral recruitment is one of an alternative rehabilitation method in shallow reef with low visibility.
2001-04-11
The Great Barrier Reef extends for 2,000 kilometers along the northeastern coast of Australia. It is not a single reef, but a vast maze of reefs, passages, and coral cays islands that are part of the reef.
Characterization of Inductive loop coupling in a Cyclotron Dee Structure
NASA Astrophysics Data System (ADS)
Carroll, Lewis
Many of today's low to medium-energy cyclotrons apply RF power to the resonator structure (the dees) by inductive loop coupling through a feed-line driven by an RF transmitter employing a triode or tetrode power tube. The transmitter's output network transforms the tube's optimum load line (typically a few thousand ohms) down to Z0, typically 50 ohms. But the load-line is not a physical resistance, so one would not expect to see 50 ohms when looking back toward the transmitter. Moreover, if both the resonator's input and the transmitter's output are matched to Z0, then the coupled or working Q of the resonator is reduced to half that of the uncoupled Q, implying that half the power is being dissipated in the transmitter's output resistance- an inefficient and expensive solution for a high power RF application. More power is available if the transmitter's reverse-impedance is not matched to Z0, but this may result in misalignment between the frequency for correct forward match at the loop, versus the frequency for maximum power in the resonator. The misalignment can be eliminated, and the working Q maximized, by choosing the appropriate length of feed-line between the non-matched transmitter output and the matched resonator's input. In addition, the transmitter's output impedance may be complex, comprising resistance plus reactance, requiring a further process and means of measuring the output impedance so that an additional compensating length of feed-line can be incorporated. But a wrong choice of overall feed-line length- even though correctly load-matched at the resonator's operating frequency- can result in a curious degenerate condition, where the resonator's working Q appears to collapse, and the potential for transmitter overload increases substantially: a condition to be avoided!
NASA Astrophysics Data System (ADS)
Buhl-Mortensen, L.; Serigstad, B.; Buhl-Mortensen, P.; Olsen, M. N.; Ostrowski, M.; Błażewicz-Paszkowycz, M.; Appoh, E.
2017-03-01
The distribution of cold-water coral reefs is relatively well known in the North-east Atlantic as compared to the Central-east Atlantic, where only a few documentations exist from low latitudes. In 2012 an initial survey was conducted on a reef situated at 400 m depth on the continental shelf off Ghana. The reef corals and fauna were visually documented using a Video Assisted Multi Sampler (VAMS) coupled with an ROV. Here we present the results from three dives on the 1400 m long and 70 m high reef with an ambient temperatures between 9 and 10 °C. The banana shaped reef was oriented perpendicular to the main current, the convex side facing the current and there was no sign of human impact. The great height of the reef is probably a result of undisturbed growth for more than 20,000 years. On the Norwegian continental shelf the largest reefs are around 30 m high and have been aged to 9000 years. The reef morphology resembles that of Northeast Atlantic Lophelia reefs. The main reef building coral was Lophelia pertusa with contribution from Madrepora oculata, Solenosmilia variabilis, and occasional occurrences of Dendrophyllia cf. alternata. The skeleton of Aphrocallistes beatrix (Hexactinellidae) contributed to the reef framework and the reef consisted of 46% coral blocks 22% sediment, 13% coral rubble, 11% sponge skeleton and 8% live corals. A rich megafauna of 31 taxa was recorded and most frequent was Acesta excavate (bivalve), Aphrocallistes beatrix (with an associated Zooanthida on 39% of the colonies), squat lobsters, hydroids and bryozoans. Six fish species were recorded of which the Sebastidae Helicolenus dactylopterus and Nettastoma melanurum were found amongst coral blocks. The reef community showed several similarities with the northern reefs with sponges, Sebastes spp., squat lobsters, and Acesta excavata being common megafauna associates. In contrast the gorgonian corals that are characteristic of the northern reefs seemed to be lacking and Hexactinellidae rather than Demospongia were common on the reef and contributed to the reef framework. Crabs that are uncommon on northern reefs were frequently encountered.
Say what? Coral reef sounds as indicators of community assemblages and reef conditions
NASA Astrophysics Data System (ADS)
Mooney, T. A.; Kaplan, M. B.
2016-02-01
Coral reefs host some of the highest diversity of life on the planet. Unfortunately, reef health and biodiversity is declining or is threatened as a result of climate change and human influences. Tracking these changes is necessary for effective resource management, yet estimating marine biodiversity and tracking trends in ecosystem health is a challenging and expensive task, especially in many pristine reefs which are remote and difficult to access. Many fishes, mammals and invertebrates make sound. These sounds are reflective of a number of vital biological processes and are a cue for settling reef larvae. Biological sounds may be a means to quantify ecosystem health and biodiversity, however the relationship between coral reef soundscapes and the actual taxa present remains largely unknown. This study presents a comparative evaluation of the soundscape of multiple reefs, naturally differing in benthic cover and fish diversity, in the U.S. Virgin Islands National Park. Using multiple recorders per reef we characterized spacio-temporal variation in biological sound production within and among reefs. Analyses of sounds recorded over 4 summer months indicated diel trends in both fish and snapping shrimp acoustic frequency bands with crepuscular peaks at all reefs. There were small but statistically significant acoustic differences among sites on a given reef raising the possibility of potentially localized acoustic habitats. The strength of diel trends in lower, fish-frequency bands were correlated with coral cover and fish density, yet no such relationship was found with shrimp sounds suggesting that fish sounds may be of higher relevance to tracking certain coral reef conditions. These findings indicate that, in spite of considerable variability within reef soundscapes, diel trends in low-frequency sound production reflect reef community assemblages. Further, monitoring soundscapes may be an efficient means of establishing and monitoring reef conditions.
2004-09-20
ISS009-E-23808 (20 September 2004) --- A fringing coral reef in the Red Sea is featured in this image photographed by an Expedition 9 crewmember on the International Space Station (ISS). The Sudanese coast of the Red Sea is a well known destination for divers due to clear water and abundance of coral reefs (or shiaab in Arabic). According to NASA scientists studying the ISS imagery, reefs are formed primarily from precipitation of calcium carbonate by corals; massive reef structures are built over thousands of years of succeeding generations of coral. In the Red Sea, fringing reefs form on shallow shelves of less than 50 meters depth along the coastline. This photograph illustrates the intricate morphology of the reef system located along the coast between Port Sudan to the northwest and the Tokar River delta to the southeast. Close to shore, fringing reefs border the coastline. Farther offshore grows a larger, more complicated barrier reef structure. Different parts of the reef structure show up as variable shades of light blue. Deeper water channels (darker blue) define the boundaries for individual reefs within the greater barrier reef system. Such a complex pattern of reefs may translate into greater ecosystem diversity through a wide variety of local reef environments.
Climate-driven coral reorganisation influences aggressive behaviour in juvenile coral-reef fishes
NASA Astrophysics Data System (ADS)
Kok, Judith E.; Graham, Nicholas A. J.; Hoogenboom, Mia O.
2016-06-01
Globally, habitat degradation is altering the abundance and diversity of species in a variety of ecosystems. This study aimed to determine how habitat degradation, in terms of changing coral composition under climate change, affected abundance, species richness and aggressive behaviour of juveniles of three damselfishes ( Pomacentrus moluccensis, P. amboinensis and Dischistodus perspicillatus, in order of decreasing reliance on coral). Patch reefs were constructed to simulate two types of reefs: present-day reefs that are vulnerable to climate-induced coral bleaching, and reefs with more bleaching-robust coral taxa, thereby simulating the likely future of coral reefs under a warming climate. Fish communities were allowed to establish naturally on the reefs during the summer recruitment period. Climate-robust reefs had lower total species richness of coral-reef fishes than climate-vulnerable reefs, but total fish abundance was not significantly different between reef types (pooled across all species and life-history stages). The nature of aggressive interactions, measured as the number of aggressive chases, varied according to coral composition; on climate-robust reefs, juveniles used the substratum less often to avoid aggression from competitors, and interspecific aggression became relatively more frequent than intraspecific aggression for juveniles of the coral-obligate P. moluccensis. This study highlights the importance of coral composition as a determinant of behaviour and diversity of coral-reef fishes.
Wise, M.B.; Thompson, C.V.
1998-07-14
An in-line gas monitor capable of accurate gas composition analysis in a continuous real time manner even under strong applied vacuum conditions operates by mixing an air sample with helium forming a sample gas in two complementary sample loops embedded in a manifold which includes two pairs of 3-way solenoid valves. The sample gas is then analyzed in an ion trap mass spectrometer on a continuous basis. Two valve drivers actuate the two pairs of 3-way valves in a reciprocating fashion, so that there is always flow through the in-line gas monitor via one or the other of the sample loops. The duty cycle for the two pairs of 3-way valves is varied by tuning the two valve drivers to a duty cycle typically between 0.2 to 0.7 seconds. 3 figs.
Gao, X; Xie, J K; Wan, Y X; Ushigusa, K; Wan, B N; Zhang, S Y; Li, J; Kuang, G L
2002-01-01
Stationary multifaceted asymmetric radiation from the edge (MARFE) is studied by gas-puffing feedback control according to an empirical MARFE critical density ( approximately 1.8 x 10(13) cm(-3)) in the HT-7 Ohmic discharges (where the plasma current I(p) is about 170 kA, loop voltage V(loop)=2-3 V, toroidal field B(T)=1.9 T, and Z(eff)=3-4). It is observed that an improved confinement mode characterized by D(alpha) line emissions drops and the line-averaged density increase is triggered in the stationary MARFE discharges. The mode is not a symmetric "detachment" state, because the quasi-steady-state poloidally asymmetric radiation (e.g., C III line emissions) still exists. This phenomenon has not been predicted by the current MARFE theory.
Nucleation of stable superconductivity in YBCO-films
NASA Astrophysics Data System (ADS)
Kötzler, J.
By means of the linear dynamic conductivity, inductively measured on epitaxial films between 30mHz and 30 MHz, the transition line T g (B) to generic superconductivity is studied in fields between B=0 and 19T. It follows closely the melting line T m (B) described recently in terms of a blowout of thermal vortex loops in clean materials. The critical exponents of the correlation length and time near T g (B), however, enem to be dominated by some intrinsic disorder. Columnar defects produced by heavy-ion irradiation up to field-equivalent-doses of B ϕ =10T lead to adisappointing reduction of T g (B→0) while for B>B ϕ the generic line of the pristine film is recovered. These novel results are also discussed in terms of a loop-driven destruction of generic superconductivity.
Using vessels as artificial reefs is an option for disposal. Artificial reefs serve to benefit the environment. Vessel-to-reef projects can follow the best management practices guidance. Guidance are provided for how to clean up vessels for use as reefs.
Searching for Spectroscopic Signs of Termination Shocks in Solar Flares
NASA Astrophysics Data System (ADS)
Galan, G.; Polito, V.; Reeves, K.
2017-12-01
The standard flare model predicts the presence of a termination shock located above the flare loop tops, however terminations shocks have not yet been well observed. We analyze flare observations by the Interface Region Imaging Spectrograph (IRIS), which provides cotemporal UV imaging and spectral data. Specifically, we study plasma emissions in the Fe XXI line, formed at the very hot plasma temperatures in flares (> 10 MK). Imaging observations that point to shocks include fast hot reconnection downflows above the loop tops and localized dense, bright plasma at the loop tops; spectral signatures that suggest shocks in the locality of the loop tops include redshifts and nonthermal broadening of the Fe XXI line. We identify possibly significant redshifts in some on-disk flare events observed by IRIS. Redshifts are observed in the vicinity of the bright loop top source that is thought to coincide with the site of the shock. In these events, the Fe XXI emissions at the time of the redshifted structures are dominated by at the at-rest components. The much more less intense redshifted components are broader, with velocities of 200 km/s. The spatial location of these shifts might indicate plasma motions and speeds indicative of termination shocks. This work is supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313, and by NASA Grant NNX15AJ93G. Keywords: Solar flares, Solar magnetic reconnection, Termination shocks
NASA Astrophysics Data System (ADS)
Lindo-Atichati, D.; Curcic, M.; Paris, C. B.; Buston, P. M.
2016-10-01
The gains from implementing high-resolution versus less costly low-resolution models to describe coastal circulation are not always clear, often lacking statistical evaluation. Here we construct a hierarchy of ocean-atmosphere models operating at multiple scales within a 1 × 1° domain of the Belizean Barrier Reef (BBR). The various components of the atmosphere-ocean models are evaluated with in situ observations of surface drifters, wind and sea surface temperature. First, we compare the dispersion and velocity of 55 surface drifters released in the field in summer 2013 to the dispersion and velocity of simulated drifters under alternative model configurations. Increasing the resolution of the ocean model (from 1/12° to 1/100°, from 1 day to 1 h) and atmosphere model forcing (from 1/2° to 1/100°, from 6 h to 1 h), and incorporating tidal forcing incrementally reduces discrepancy between simulated and observed velocities and dispersion. Next, in trying to understand why the high-resolution models improve prediction, we find that resolving both the diurnal sea-breeze and semi-diurnal tides is key to improving the Lagrangian statistics and transport predictions along the BBR. Notably, the model with the highest ocean-atmosphere resolution and with tidal forcing generates a higher number of looping trajectories and sub-mesoscale coherent structures that are otherwise unresolved. Finally, simulations conducted with this model from June to August of 2013 show an intensification of the velocity fields throughout the summer and reveal a mesoscale anticyclonic circulation around Glovers Reef, and sub-mesoscale cyclonic eddies formed in the vicinity of Columbus Island. This study provides a general framework to assess the best surface transport prediction from alternative ocean-atmosphere models using metrics derived from high frequency drifters' data and meteorological stations.
Reef sharks: recent advances in ecological understanding to inform conservation.
Osgood, G J; Baum, J K
2015-12-01
Sharks are increasingly being recognized as important members of coral-reef communities, but their overall conservation status remains uncertain. Nine of the 29 reef-shark species are designated as data deficient in the IUCN Red List, and three-fourths of reef sharks had unknown population trends at the time of their assessment. Fortunately, reef-shark research is on the rise. This new body of research demonstrates reef sharks' high site restriction, fidelity and residency on coral reefs, their broad trophic roles connecting reef communities and their high population genetic structure, all information that should be useful for their management and conservation. Importantly, recent studies on the abundance and population trends of the three classic carcharhinid reef sharks (grey reef shark Carcharhinus amblyrhynchos, blacktip reef shark Carcharhinus melanopterus and whitetip reef shark Triaenodon obesus) may contribute to reassessments identifying them as more vulnerable than currently realized. Because over half of the research effort has focused on only these three reef sharks and the nurse shark Ginglymostoma cirratum in only a few locales, there remain large taxonomic and geographic gaps in reef-shark knowledge. As such, a large portion of reef-shark biodiversity remains uncharacterized despite needs for targeted research identified in their red list assessments. A research agenda for the future should integrate abundance, life history, trophic ecology, genetics, habitat use and movement studies, and expand the breadth of such research to understudied species and localities, in order to better understand the conservation requirements of these species and to motivate effective conservation solutions. © 2015 The Fisheries Society of the British Isles.
New evidence for the barrier reef model, Permian Capitan Reef complex, New Mexico
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kirkland, B.L.; Moore, C.H. Jr.
1990-05-01
Recent paleontologic and petrologic observations suggest that the Capitan Formation was deposited as an organic or ecologic reef that acted as an emergent barrier to incoming wave energy. In outcrops in the Guadalupe Mountains and within Carlsbad Caverns, massive reef boundstone contains a highly diverse assemblage of frame-building and binding organisms. In modern reefs, diversity among frame builders decreases dramatically with depth. Marine cement is abundant in reef boundstone, but limited in back-reef grainstone and packstone. This cementation pattern is similar to that observed in modern emergent barrier reef systems. Based on comparison with modern analogs, these dasycladrominated back-reef sedimentsmore » and their associated biota are indicative of shallow, hypersaline conditions. Few of these dasyclads exhibit broken or abraded segments and some thallus sections are still articulated suggesting that low-energy, hypersaline conditions occurred immediately shelfward of the reef. In addition, large-scale topographic features, such as possible spur and groove structures between Walnut Canyon and Rattlesnake Canyon, and facies geometries, such as the reef to shelf transition, resemble those found in modern shallow-water reefs. The organisms that formed the Capitan Reef appear to have lived in, and responded to, physical and chemical conditions similar to those that control the geometry of modern shallow-water reefs. Like their modern counterparts, they seem to have strongly influenced adjacent environments. In light of this evidence, consideration should be given to either modifying or abandoning the marginal mound model in favor of the originally proposed barrier reef model.« less
Suitable Environmental Ranges for Potential Coral Reef Habitats in the Tropical Ocean
Guan, Yi; Hohn, Sönke; Merico, Agostino
2015-01-01
Coral reefs are found within a limited range of environmental conditions or tolerance limits. Estimating these limits is a critical prerequisite for understanding the impacts of climate change on the biogeography of coral reefs. Here we used the diagnostic model ReefHab to determine the current environmental tolerance limits for coral reefs and the global distribution of potential coral reef habitats as a function of six factors: temperature, salinity, nitrate, phosphate, aragonite saturation state, and light. To determine these tolerance limits, we extracted maximum and minimum values of all environmental variables in corresponding locations where coral reefs are present. We found that the global, annually averaged tolerance limits for coral reefs are 21.7—29.6 °C for temperature, 28.7—40.4 psu for salinity, 4.51 μmol L-1 for nitrate, 0.63 μmol L-1 for phosphate, and 2.82 for aragonite saturation state. The averaged minimum light intensity in coral reefs is 450 μmol photons m-2 s-1. The global area of potential reef habitats calculated by the model is 330.5 × 103 km2. Compared with previous studies, the tolerance limits for temperature, salinity, and nutrients have not changed much, whereas the minimum value of aragonite saturation in coral reef waters has decreased from 3.28 to 2.82. The potential reef habitat area calculated with ReefHab is about 121×103 km2 larger than the area estimated from the charted reefs, suggesting that the growth potential of coral reefs is higher than currently observed. PMID:26030287
Suitable environmental ranges for potential coral reef habitats in the tropical ocean.
Guan, Yi; Hohn, Sönke; Merico, Agostino
2015-01-01
Coral reefs are found within a limited range of environmental conditions or tolerance limits. Estimating these limits is a critical prerequisite for understanding the impacts of climate change on the biogeography of coral reefs. Here we used the diagnostic model ReefHab to determine the current environmental tolerance limits for coral reefs and the global distribution of potential coral reef habitats as a function of six factors: temperature, salinity, nitrate, phosphate, aragonite saturation state, and light. To determine these tolerance limits, we extracted maximum and minimum values of all environmental variables in corresponding locations where coral reefs are present. We found that the global, annually averaged tolerance limits for coral reefs are 21.7-29.6 °C for temperature, 28.7-40.4 psu for salinity, 4.51 μmol L-1 for nitrate, 0.63 μmol L-1 for phosphate, and 2.82 for aragonite saturation state. The averaged minimum light intensity in coral reefs is 450 μmol photons m-2 s-1. The global area of potential reef habitats calculated by the model is 330.5 × 103 km2. Compared with previous studies, the tolerance limits for temperature, salinity, and nutrients have not changed much, whereas the minimum value of aragonite saturation in coral reef waters has decreased from 3.28 to 2.82. The potential reef habitat area calculated with ReefHab is about 121×103 km2 larger than the area estimated from the charted reefs, suggesting that the growth potential of coral reefs is higher than currently observed.
NASA Technical Reports Server (NTRS)
Emslie, A. G.; Li, Peng; Mariska, John T.
1992-01-01
A series of hydrodynamic numerical simulations of nonthermal electron-heated solar flare atmospheres and their corresponding soft X-ray Ca XIX emission-line profiles, under the conditions of tapered flare loop geometry and/or a preheated atmosphere, is presented. The degree of tapering is parameterized by the magnetic mirror ratio, while the preheated atmosphere is parameterized by the initial upper chromospheric pressure. In a tapered flare loop, it is found that the upward motion of evaporated material is faster compared with the case where the flare loop is uniform. This is due to the diverging nozzle seen by the upflowing material. In the case where the flare atmosphere is preheated and the flare geometry is uniform, the response of the atmosphere to the electron collisional heating is slow. The upward velocity of the hydrodynamic gas is reduced due not only to the large coronal column depth, but also to the increased inertia of the overlying material. It is concluded that the only possible electron-heated scenario in which the predicted Ca XIX line profiles agree with the BCS observations is when the impulsive flare starts in a preheated dense corona.
Shamah, S M; Stiles, C D; Guha, A
1993-01-01
Malignant astrocytoma is the most common primary human brain tumor. Most astrocytomas express a combination of platelet-derived growth factor (PDGF) and PDGF receptor which could close an autocrine loop. It is not known whether these autocrine loops contribute to the transformed phenotype of astrocytoma cells or are incidental to that phenotype. Here we show that dominant-negative mutants of the PDGF ligand break the autocrine loop and revert the phenotype of BALB/c 3T3 cells transformed by the PDGF-A or PDGF-B (c-sis) gene. Then, we show that these mutants are selective in that they do not alter the phenotype of 3T3 cells transformed by an activated Ha-ras or v-src gene or by simian virus 40. Finally, we show that these mutants revert the transformed phenotype of two independent human astrocytoma cell lines. They have no effect on the growth of human medulloblastoma, bladder carcinoma, or colon carcinoma cell lines. These observations are consistent with the view that PDGF autocrine loops contribute to the transformed phenotype of at least some human astrocytomas. Images PMID:8246942
Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-18
... Drum, Reef Fish, Shrimp, and Coral and Coral Reefs Fishery Management Plans (Generic ACL Amendment) for... the Caribbean, Gulf of Mexico, and South Atlantic; Gulf of Mexico Reef Fish Fishery; South Atlantic... management unit in the Fishery Management Plan for Reef Fish Resources of the Gulf of Mexico (Reef Fish FMP...
Coral Reefs: An English Compilation of Activities for Middle School Students.
ERIC Educational Resources Information Center
Walker, Sharon H.; Newton, R. Amanda; Ortiz, Alida
This activity book on coral reefs for middle school students is divided into 10 sections. Section 1 contains the introduction. Section 2 describes what coral reefs are while section 3 describes how coral reefs reproduce and grow. Section 4 discusses where coral reefs are found and section 5 describes life on a coral reef. Section 6 discusses the…
Coral reef resilience through biodiversity
Rogers, Caroline S.
2013-01-01
Irrefutable evidence of coral reef degradation worldwide and increasing pressure from rising seawater temperatures and ocean acidification associated with climate change have led to a focus on reef resilience and a call to “manage” coral reefs for resilience. Ideally, global action to reduce emission of carbon dioxide and other greenhouse gases will be accompanied by local action. Effective management requires reduction of local stressors, identification of the characteristics of resilient reefs, and design of marine protected area networks that include potentially resilient reefs. Future research is needed on how stressors interact, on how climate change will affect corals, fish, and other reef organisms as well as overall biodiversity, and on basic ecological processes such as connectivity. Not all reef species and reefs will respond similarly to local and global stressors. Because reef-building corals and other organisms have some potential to adapt to environmental changes, coral reefs will likely persist in spite of the unprecedented combination of stressors currently affecting them. The biodiversity of coral reefs is the basis for their remarkable beauty and for the benefits they provide to society. The extraordinary complexity of these ecosystems makes it both more difficult to predict their future and more likely they will have a future.
NASA Astrophysics Data System (ADS)
Carter, Alex B.; Davies, Campbell R.; Mapstone, Bruce D.; Russ, Garry R.; Tobin, Andrew J.; Williams, Ashley J.
2014-09-01
Batch fecundity of female Plectropomus leopardus, a coral reef fish targeted by commercial and recreational fishing, was compared between reefs open to fishing and reefs within no-take marine reserves within three regions of the Great Barrier Reef (GBR), Australia. Length, weight, and age had positive effects on batch fecundity of spawners from northern and central reefs but negligible effects on spawners from southern reefs. Females were least fecund for a given length, weight, and age in the southern GBR. Batch fecundity of a 500-mm fork length female was 430 % greater on central reefs and 207 % greater on northern reefs than on southern reefs. The effects of length and age on batch fecundity did not differ significantly between reserve and fished reefs in any region, but weight-specific fecundity was 100 % greater for large 2.0 kg females on reserve reefs compared with fished reefs in the central GBR. We hypothesize that regional variation in batch fecundity is likely driven by water temperature and prey availability. Significant regional variation in batch fecundity highlights the need for understanding spatial variation in reproductive output where single conservation or fishery management strategies cover large, potentially diverse, spatial scales.
NASA Astrophysics Data System (ADS)
Kitsikoudis, V.; Kibler, K. M.; Spiering, D. W.
2017-12-01
This study analyzes flow patterns and sediment distributions around three oyster reefs in a bar-built estuarine lagoon. We studied a degraded reef, a recently restored reef, and a reference condition reef with a healthy live oyster community. The restored reef had been regraded and restored with oyster shell mats to aid in recruitment of oyster spat, with the goal of reestablishing a healthy oyster community. Despite the fact that flow-biota-sediment interaction constitutes a blossoming research field, actual field data are sparse and current knowledge emanates from flume studies and numerical modeling. Moreover, the hydraulic effect of restored oyster reefs has not been thoroughly investigated and it is not clear if the flow field and sediment erosion/deposition are similar or diverge from natural reefs. Instantaneous three-dimensional flow velocities were collected on reefs using a Nortek Vectrino Profiler and an acoustic Doppler current profiler (Nortek Aquadopp). The former measured a 2 - 3 cm velocity profile above the oyster bed, while the latter quantified incoming velocities across the flow profile approximately 10 m from the edge of the reef. Flow measurements were conducted during rising tides and are coupled with simultaneous wind speed and direction data. In addition, 20 cm deep sediment cores were retrieved on and off the investigated reefs. Sediment grain size distributions were determined after individual cores were processed for loss on ignition. Incoming flow velocities were as high as 10 cm/s, relatively higher than those recorded close to reefs. Mean and turbulent flow velocities close to the reefs, varied among the investigated sites, despite the similar wind flow conditions offshore. For instance, the measurements at the degraded reef showed decreased wave attenuation and augmented flow velocities compared to the other sites. Boat wakes exhibited a very distinct signal in the flow velocity time-series and significantly increased the approaching flow velocity at the reefs. The oyster roughness height at the restored reef (68 mm) was higher than the roughness at the reference reef (45 mm); however, the variance was higher at the latter. Sediments from degraded reef and the recently restored reef were coarser and contained less organic matter compared to the reference condition reef.
Simulating reef response to sea-level rise at Lizard Island: A geospatial approach
NASA Astrophysics Data System (ADS)
Hamylton, S. M.; Leon, J. X.; Saunders, M. I.; Woodroffe, C. D.
2014-10-01
Sea-level rise will result in changes in water depth over coral reefs, which will influence reef platform growth as a result of carbonate production and accretion. This study simulates the pattern of reef response on the reefs around Lizard Island in the northern Great Barrier Reef. Two sea-level rise scenarios are considered to capture the range of likely projections: 0.5 m and 1.2 m above 1990 levels by 2100. Reef topography has been established through extensive bathymetric profiling, together with available data, including LiDAR, single beam bathymetry, multibeam swath bathymetry, LADS and digitised chart data. The reef benthic cover around Lizard Island has been classified using a high resolution WorldView-2 satellite image, which is calibrated and validated against a ground referencing dataset of 364 underwater video records of the reef benthic character. Accretion rates are parameterised using published hydrochemical measurements taken in-situ and rules are applied using Boolean logic to incorporate geomorphological transitions associated with different depth ranges, such as recolonisation of the reef flat when it becomes inundated as sea level rises. Simulations indicate a variable platform response to the different sea-level rise scenarios. For the 0.5 m rise, the shallower reef flats are gradually colonised by corals, enabling this active geomorphological zone to keep up with the lower rate of rise while the other sand dominated areas get progressively deeper. In the 1.2 m scenario, a similar pattern is evident for the first 30 years of rise, beyond which the whole reef platform begins to slowly drown. To provide insight on reef response to sea-level rise in other areas, simulation results of four different reef settings are discussed and compared at the southeast reef flat (barrier reef), Coconut Beach (fringing reef), Watson's Bay (leeward bay with coral patches) and Mangrove Beach (sheltered lagoonal embayment). The reef sites appear to accrete upwards at a rate commensurate with the rate of rise, thereby maintaining their original profile and position relative to the sea surface and the leeward and lagoonal sites with a low accretion rate maintain a similar profile but slowly gain depth relative to sea-level. The result of this variable response is that elevated features of the reef platform, such as reef patches and crests tend to become more pronounced.
Bridge, Tom; Beaman, Robin; Done, Terry; Webster, Jody
2012-01-01
Aim Coral reef communities occurring in deeper waters have received little research effort compared to their shallow-water counterparts, and even such basic information as their location and extent are currently unknown throughout most of the world. Using the Great Barrier Reef as a case study, habitat suitability modelling is used to predict the distribution of deep-water coral reef communities on the Great Barrier Reef, Australia. We test the effectiveness of a range of geophysical and environmental variables for predicting the location of deep-water coral reef communities on the Great Barrier Reef. Location Great Barrier Reef, Australia. Methods Maximum entropy modelling is used to identify the spatial extent of two broad communities of habitat-forming megabenthos phototrophs and heterotrophs. Models were generated using combinations of geophysical substrate properties derived from multibeam bathymetry and environmental data derived from Bio-ORACLE, combined with georeferenced occurrence records of mesophotic coral communities from autonomous underwater vehicle, remotely operated vehicle and SCUBA surveys. Model results are used to estimate the total amount of mesophotic coral reef habitat on the GBR. Results Our models predict extensive but previously undocumented coral communities occurring both along the continental shelf-edge of the Great Barrier Reef and also on submerged reefs inside the lagoon. Habitat suitability for phototrophs is highest on submerged reefs along the outer-shelf and the deeper flanks of emergent reefs inside the GBR lagoon, while suitability for heterotrophs is highest in the deep waters along the shelf-edge. Models using only geophysical variables consistently outperformed models incorporating environmental data for both phototrophs and heterotrophs. Main Conclusion Extensive submerged coral reef communities that are currently undocumented are likely to occur throughout the Great Barrier Reef. High-quality bathymetry data can be used to identify these reefs, which may play an important role in resilience of the GBR ecosystem to climate change. PMID:23118952
Impacts and recovery from severe tropical cyclone Yasi on the Great Barrier Reef.
Beeden, Roger; Maynard, Jeffrey; Puotinen, Marjetta; Marshall, Paul; Dryden, Jen; Goldberg, Jeremy; Williams, Gareth
2015-01-01
Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1-Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km2) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km2) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance.
NASA Astrophysics Data System (ADS)
Zuo, Xiuling; Su, Fenzhen; Zhao, Huanting; Zhang, Junjue; Wang, Qi; Wu, Di
2017-05-01
Coral reefs in the Xisha Islands (also known as the Paracel Islands in English), South China Sea, have experienced dramatic declines in coral cover. However, the current regional scale hard coral distribution of geomorphic and ecological zones, essential for reefs management in the context of global warming and ocean acidification, is not well documented. We analyzed data from field surveys, Landsat-8 and GF-1 images to map the distribution of hard coral within geomorphic zones and reef flat ecological zones. In situ surveys conducted in June 2014 on nine reefs provided a complete picture of reef status with regard to live coral diversity, evenness of coral cover and reef health (live versus dead cover) for the Xisha Islands. Mean coral cover was 12.5% in 2014 and damaged reefs seemed to show signs of recovery. Coral cover in sheltered habitats such as lagoon patch reefs and biotic dense zones of reef flats was higher, but there were large regional differences and low diversity. In contrast, the more exposed reef slopes had high coral diversity, along with high and more equal distributions of coral cover. Mean hard coral cover of other zones was <10%. The total Xisha reef system was estimated to cover 1 060 km2, and the emergent reefs covered 787 m2. Hard corals of emergent reefs were considered to cover 97 km2. The biotic dense zone of the reef flat was a very common zone on all simple atolls, especially the broader northern reef flats. The total cover of live and dead coral can reach above 70% in this zone, showing an equilibrium between live and dead coral as opposed to coral and algae. This information regarding the spatial distribution of hard coral can support and inform the management of Xisha reef ecosystems.
Impacts and Recovery from Severe Tropical Cyclone Yasi on the Great Barrier Reef
Beeden, Roger; Maynard, Jeffrey; Puotinen, Marjetta; Marshall, Paul; Dryden, Jen; Goldberg, Jeremy; Williams, Gareth
2015-01-01
Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1—Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km2) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km2) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance. PMID:25874718
A geological perspective on the degradation and conservation of western Atlantic coral reefs.
Kuffner, Ilsa B; Toth, Lauren T
2016-08-01
Continuing coral-reef degradation in the western Atlantic is resulting in loss of ecological and geologic functions of reefs. With the goal of assisting resource managers and stewards of reefs in setting and measuring progress toward realistic goals for coral-reef conservation and restoration, we examined reef degradation in this region from a geological perspective. The importance of ecosystem services provided by coral reefs-as breakwaters that dissipate wave energy and protect shorelines and as providers of habitat for innumerable species-cannot be overstated. However, the few coral species responsible for reef building in the western Atlantic during the last approximately 1.5 million years are not thriving in the 21st century. These species are highly sensitive to abrupt temperature extremes, prone to disease infection, and have low sexual reproductive potential. Their vulnerability and the low functional redundancy of branching corals have led to the low resilience of western Atlantic reef ecosystems. The decrease in live coral cover over the last 50 years highlights the need for study of relict (senescent) reefs, which, from the perspective of coastline protection and habitat structure, may be just as important to conserve as the living coral veneer. Research is needed to characterize the geological processes of bioerosion, reef cementation, and sediment transport as they relate to modern-day changes in reef elevation. For example, although parrotfish remove nuisance macroalgae, possibly promoting coral recruitment, they will not save Atlantic reefs from geological degradation. In fact, these fish are quickly nibbling away significant quantities of Holocene reef framework. The question of how different biota covering dead reefs affect framework resistance to biological and physical erosion needs to be addressed. Monitoring and managing reefs with respect to physical resilience, in addition to ecological resilience, could optimize the expenditure of resources in conserving Atlantic reefs and the services they provide. © 2016 The Authors. Conservation Biology published by Wiley Periodicals, Inc., on behalf of Society for Conservation Biology.
Bottlenecks to coral recovery in the Seychelles
NASA Astrophysics Data System (ADS)
Chong-Seng, K. M.; Graham, N. A. J.; Pratchett, M. S.
2014-06-01
Processes that affect recovery of coral assemblages require investigation because coral reefs are experiencing a diverse array of more frequent disturbances. Potential bottlenecks to coral recovery include limited larval supply, low rates of settlement, and high mortality of new recruits or juvenile corals. We investigated spatial variation in local abundance of scleractinian corals in the Seychelles at three distinct life history stages (recruits, juveniles, and adults) on reefs with differing benthic conditions. Following widespread coral loss due to the 1998 bleaching event, some reefs are recovering (i.e., relatively high scleractinian coral cover: `coral-dominated'), some reefs have low cover of living macrobenthos and unconsolidated rubble substrates (`rubble-dominated'), and some reefs have high cover of macroalgae (`macroalgal-dominated'). Rates of coral recruitment to artificial settlement tiles were similar across all reef conditions, suggesting that larval supply does not explain differential coral recovery across the three reef types. However, acroporid recruits were absent on macroalgal-dominated reefs (0.0 ± 0.0 recruits tile-1) in comparison to coral-dominated reefs (5.2 ± 1.6 recruits tile-1). Juvenile coral colony density was significantly lower on macroalgal-dominated reefs (2.4 ± 1.1 colonies m-2), compared to coral-dominated reefs (16.8 ± 2.4 m-2) and rubble-dominated reefs (33.1 ± 7.3 m-2), suggesting that macroalgal-dominated reefs have either a bottleneck to successful settlement on the natural substrates or a high post-settlement mortality bottleneck. Rubble-dominated reefs had very low cover of adult corals (10.0 ± 1.7 %) compared to coral-dominated reefs (33.4 ± 3.6 %) despite no statistical difference in their juvenile coral densities. A bottleneck caused by low juvenile colony survivorship on unconsolidated rubble-dominated reefs is possible, or alternatively, recruitment to rubble-dominated reefs has only recently begun. This study identified bottlenecks to recovery of coral assemblages that varied depending on post-disturbance habitat condition.
Wu, Yun; Wang, Lin -Lin; Mun, Eundeok; ...
2016-04-04
In topological quantum materials 1,2,3 the conduction and valence bands are connected at points or along lines in the momentum space. A number of studies have demonstrated that several materials are indeed Dirac/Weyl semimetals 4,5,6,7,8. However, there is still no experimental confirmation of materials with line nodes, in which the Dirac nodes form closed loops in the momentum space 2,3. Here we report the discovery of a novel topological structure—Dirac node arcs—in the ultrahigh magnetoresistive material PtSn 4 using laser-based angle-resolved photoemission spectroscopy data and density functional theory calculations. Unlike the closed loops of line nodes, the Dirac node arcmore » structure arises owing to the surface states and resembles the Dirac dispersion in graphene that is extended along a short line in the momentum space. Here, we propose that this reported Dirac node arc structure is a novel topological state that provides an exciting platform for studying the exotic properties of Dirac fermions.« less
On the decentralized control of large-scale systems. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
Chong, C.
1973-01-01
The decentralized control of stochastic large scale systems was considered. Particular emphasis was given to control strategies which utilize decentralized information and can be computed in a decentralized manner. The deterministic constrained optimization problem is generalized to the stochastic case when each decision variable depends on different information and the constraint is only required to be satisfied on the average. For problems with a particular structure, a hierarchical decomposition is obtained. For the stochastic control of dynamic systems with different information sets, a new kind of optimality is proposed which exploits the coupled nature of the dynamic system. The subsystems are assumed to be uncoupled and then certain constraints are required to be satisfied, either in a off-line or on-line fashion. For off-line coordination, a hierarchical approach of solving the problem is obtained. The lower level problems are all uncoupled. For on-line coordination, distinction is made between open loop feedback optimal coordination and closed loop optimal coordination.
Coupling the Gaussian Free Fields with Free and with Zero Boundary Conditions via Common Level Lines
NASA Astrophysics Data System (ADS)
Qian, Wei; Werner, Wendelin
2018-06-01
We point out a new simple way to couple the Gaussian Free Field (GFF) with free boundary conditions in a two-dimensional domain with the GFF with zero boundary conditions in the same domain: Starting from the latter, one just has to sample at random all the signs of the height gaps on its boundary-touching zero-level lines (these signs are alternating for the zero-boundary GFF) in order to obtain a free boundary GFF. Constructions and couplings of the free boundary GFF and its level lines via soups of reflected Brownian loops and their clusters are also discussed. Such considerations show for instance that in a domain with an axis of symmetry, if one looks at the overlay of a single usual Conformal Loop Ensemble CLE3 with its own symmetric image, one obtains the CLE4-type collection of level lines of a GFF with mixed zero/free boundary conditions in the half-domain.
Determining the solar-flare photospheric scale height from SMM gamma-ray measurements
NASA Technical Reports Server (NTRS)
Lingenfelter, Richard E.
1991-01-01
A connected series of Monte Carlo programs was developed to make systematic calculations of the energy, temporal and angular dependences of the gamma-ray line and neutron emission resulting from such accelerated ion interactions. Comparing the results of these calculations with the Solar Maximum Mission/Gamma Ray Spectrometer (SMM/GRS) measurements of gamma-ray line and neutron fluxes, the total number and energy spectrum of the flare-accelerated ions trapped on magnetic loops at the Sun were determined and the angular distribution, pitch angle scattering, and mirroring of the ions on loop fields were constrained. Comparing the calculations with measurements of the time dependence of the neutron capture line emission, a determination of the He-3/H ratio in the photosphere was also made. The diagnostic capabilities of the SMM/GRS measurements were extended by developing a new technique to directly determine the effective photospheric scale height in solar flares from the neutron capture gamma-ray line measurements, and critically test current atmospheric models in the flare region.
Healthy coral reefs may assure coastal protection in face of climate change related sea level rise
NASA Astrophysics Data System (ADS)
Harris, D. L.; Rovere, A.; Parravicini, V.; Casella, E.; Canavesio, R.; Collin, A.
2016-12-01
Coral reefs are diverse ecosystems that support millions of people worldwide providing crucial services, of which, coastal protection is one of the most relevant. The efficiency of coral reefs in protecting coastlines and dissipating waves is directly linked to the cover of living corals and three dimensional reef structural complexity. Climate change and human impacts are leading to severe global reductions in live coral cover, posing serious concerns regarding the capacity of degraded reef systems in protecting tropical coastal regions. Although it is known that the loss of structurally complex reefs may lead to greater erosion of coastlines, this process has rarely been quantified and it is still unknown whether the maintenance of healthy reefs through conservation will be enough to guarantee coastal protection during rising sea levels. We show that a significant loss of wave dissipation and a subsequent increase in back-reef wave height (up to 5 times present wave height) could occur even at present sea level if living corals are lost and reef structural complexity is reduced. Yet we also show that healthy reefs, measured by structural complexity and efficiency of vertical reef accretion, may maintain their present capacity of wave dissipation even under rising sea levels. Our results indicate that the health of coral reefs and not sea level rise will be the major determinant of the coastal protection services provided by coral reefs and calls for investments into coral reef conservation to ensure the future protection of tropical coastal communities.
The characteristics and dynamics of wave-driven flow across a platform coral reef in the Red Sea
NASA Astrophysics Data System (ADS)
Lentz, S. J.; Churchill, J. H.; Davis, K. A.; Farrar, J. T.; Pineda, J.; Starczak, V.
2016-02-01
Current dynamics across a platform reef in the Red Sea near Jeddah, Saudi Arabia, are examined using 18 months of current profile, pressure, surface wave, and wind observations. The platform reef is 700 m long, 200 m across with spatial and temporal variations in water depth over the reef ranging from 0.6 to 1.6 m. Surface waves breaking at the seaward edge of the reef cause a 2-10 cm setup of sea level that drives cross-reef currents of 5-20 cm s-1. Bottom stress is a significant component of the wave setup balance in the surf zone. Over the reef flat, where waves are not breaking, the cross-reef pressure gradient associated with wave setup is balanced by bottom stress. The quadratic drag coefficient for the depth-average flow decreases with increasing water depth from Cda = 0.17 in 0.4 m of water to Cda = 0.03 in 1.2 m of water. The observed dependence of the drag coefficient on water depth is consistent with open-channel flow theory and a hydrodynamic roughness of zo = 0.06 m. A simple one-dimensional model driven by incident surface waves and wind stress accurately reproduces the observed depth-averaged cross-reef currents and a portion of the weaker along-reef currents over the focus reef and two other Red Sea platform reefs. The model indicates the cross-reef current is wave forced and the along-reef current is partially wind forced.
A magnetohydrodynamic theory of coronal loop transients
NASA Technical Reports Server (NTRS)
Yeh, T.
1982-01-01
The physical and geometrical characteristics of solar coronal loop transients are described in an MHD model based on Archimedes' MHD buoyancy force. The theory was developed from interpretation of coronagraphic data, particularly from Skylab. The brightness of a loop is taken to indicate the electron density, and successive pictures reveal the electron enhancement in different columns. The forces which lift the loop off the sun surface are analyzed as an MHD buoyancy force affecting every mass element by imparting an inertial force necessary for heliocentrifugal motion. Thermal forces are responsible for transferring the ambient stress to the interior of the loop to begin the process. The kinematic and hydrostatic buoyancy overcome the gravitational force, and a flux rope can then curve upward, spiralling like a corkscrew with varying cross section around the unwinding solar magnetic field lines.
NASA Astrophysics Data System (ADS)
Ciaravella, A.; Raymond, J. C.; Kahler, S. W.
2006-11-01
We present UV spectral information for 22 halo or partial halo CMEs observed by UVCS. The CME fronts show broad line profiles, while the line intensities are comparable to the background corona. The Doppler shifts of the front material are generally small, showing that the motion of gas in the fronts is mostly transverse to the line of sight. This indicates that, at least in halo CMEs, the fronts generally correspond to coronal plasma swept up by a shock or compression wave, rather than plasma carried outward by magnetic loops. This favors an ice cream cone (or a spherical shell) model, as opposed to an expanding arcade of loops. We use the line widths to discriminate between shock heating and bulk expansion. Of 14 cases where we detected the CME front, the line broadening in 7 cases can be attributed to shock heating, while in 3 cases it is the line-of-sight component of the CME expansion. For the CME cores we determine the angles between the motion and the plane of the sky, along with the actual heliocentric distances, in order to provide quantitative estimates of projection effects.
Study of Two Successive Three-ribbon Solar Flares on 2012 July 6
NASA Astrophysics Data System (ADS)
Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda
2014-01-01
This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.''1 resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Hα images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Hα apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.
Study of Two Successive Three-ribbon Solar Flares Using BBSO/NST Observations
NASA Astrophysics Data System (ADS)
Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda
2014-06-01
We studied two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.1 arcsec resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Halpha images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Halpha apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.
NASA Astrophysics Data System (ADS)
Conway, Kim W.; Barrie, J. Vaughn; Krautter, Manfred
2005-09-01
Multibeam imagery of siliceous sponge reefs (Hexactinellida, Hexactinosida) reveals the setting, form, and organization of five reef complexes on the western Canadian continental shelf. The reefs are built by framework skeleton sponges which trap clay-rich sediments resulting in a distinctive pattern of low intensity backscatter from the reefs that colonize more reflective glacial sediments of higher backscatter intensity. Bathymetry and backscatter maps show the distribution and form of reefs in two large complexes in the Queen Charlotte Basin (QCB) covering hundreds of km2, and three smaller reef complexes in the Georgia Basin (GB). Ridges up to 7 km long and 21 m in height, together with diversely shaped, coalescing bioherms and biostromes form the principal reef shape in the QCB whereas chains of wave-form, streamlined mounds up to 14 m in height have developed in the GB. Reef initiation is dependent on the distribution of high backscatter-intensity relict glacial surfaces, and the variation in reef complex morphology is probably the result of tidally driven, near seabed currents.
Evidence from aerial photography of structural loss of coral reefs at Barbados, West Indies
NASA Astrophysics Data System (ADS)
Lewis, J.
2002-04-01
In response to concerns about widespread degradation of coral reefs at Barbados, West Indies, over the past two decades, maps and planimetric areas of 20 fringing coral reefs were estimated from enlargements of aerial photographs of the island, using geographic information system analysis. There were statistically significant reductions in reef areas over a 40-year period from 1950 to 1991. Areal losses exceeding measurement and boundary interpretation errors of 10% were detected on eight of the 20 reefs. Ground validation carried out by divers on six of the reefs confirmed physical losses of reef structures and accumulation of rubble and sand substrata at sites where substantial planimetric area loss was detected on aerial photographs. Structural losses occurred along the "spur and groove" system of the reef-seaward edge, within deep channels or breaches in the reef front, and along the flanks or ends of reefs. The location and nature of the observed losses suggest that storm damage and seasonal alterations in beach morphology are the two most important factors contributing to geomorphological structural loss of the reefs.
Initial colonization, erosion and accretion of coral substrate
NASA Astrophysics Data System (ADS)
Davies, Peter J.; Hutchings, Patricia A.
1983-08-01
Blocks cut from Porites lutea were laid on the fore reef slope, reef flat and a lagoonal patch reef at Lizard Island, in the Northern Great Barrier Reef, and replicates removed from each environment at intervals of three months over a period of one and a half years. Variations in bioeroders and bioaccretors were noted. Microfaunas are far more numerous than macrofaunas as block colonizers; the principal borers are polychaete worms, whereas encrusters are molluscs, bryozoans, serpulids and solitary corals. The reef slope is more readily colonised by microfauna pioneer communities than are the other areas. All the environments exhibit a change from cirratulids to either sabellids or spionids (polydorids) over the length of the experiment. Accretion occurred on all blocks during the experiment, with significant differences detectable between environments; both reef slope and reef flat blocks showed weight increases of 9 10% whereas blocks from the patch reef showed increases of 15%. Annual erosion rates produced by polychaete worms are 0.694 kg m-2 year-1 (reef front), 0.843 kg m-2 year-1 (reef flat) and 1.788 kg m-2 year-1 (patch reef).
43 CFR Appendix II to Part 11 - Format for Data Inputs and Modifications to the NRDAM/CME
Code of Federal Regulations, 2012 CFR
2012-10-01
... not contain vegetation (e.g., wetland, seagrass, or kelp) or invertebrate reef (e.g., coral reef) and... invertebrate reef (e.g., coral reef) and is classified as “seaward” in Table 6.2, Volume I of the NRDAM/CME... invertebrate reef (e.g., coral reef). Tidal current—currents caused by alternating rise and fall of the sea...
NASA Astrophysics Data System (ADS)
Salas-Saavedra, Marcos; Dechnik, Belinda; Webb, Gregory E.; Webster, Jody M.; Zhao, Jian-xin; Nothdurft, Luke D.; Clark, Tara R.; Graham, Trevor; Duce, Stephanie
2018-01-01
Many factors govern reef growth through time, but their relative contributions are commonly poorly known. A prime example is the degree to which modern reef morphology is controlled by contemporary hydrodynamic settings or antecedent topography. Fortunately, reefs record essential information for interpreting palaeoclimate and palaeoenvironment within their structure as they accrete in response to environmental change. Five new cores recovered from the margin of Heron Reef, southern Great Barrier Reef (GBR), provide new insights into Holocene reef development and relationships between Holocene reefs and Pleistocene antecedent topography, suggesting much more irregular underlying topography than expected based on the configuration of the overlying modern reef margin. Cores were recovered to depths of 30 m and 94 new 230Th ages document growth between 8408 ± 24 and 2222 ± 16 yrs. BP. One core penetrated Pleistocene basement at ∼15.3 m with Holocene reef growth initiated by ∼8.4 ka BP. However, 1.83 km west along the same smooth margin, four cores failed to penetrate Pleistocene basement at depths between 20 and 30 m, suggesting that the margin at this location overlies a karst valley, or alternatively, the antecedent platform does not extend there. A 48 m-long margin-perpendicular transect of three cores documents the filling of this topographic low, at least 30 m beneath the current reef top, with seaward lateral accretion at a rate of 34.3 m/ka. Cores indicate steady vertical and lateral accretion between 3.2 and 1.8 ka BP with no evidence of the hiatus in reef flat progradation seen in most other offshore reefs of the GBR at that time. These cores suggest that the relative protection afforded by the valley allowed for unconsolidated sediment to accumulate, enabling continuous progradation even when other areas of the reef flat appear to have 'turned off'. Additionally, the cores suggest that although reefs in the southern GBR clearly owe their location to Pleistocene antecedent topography, modern reef morphology at sea level primarily reflects the interaction of Holocene reef communities with contemporary hydrodynamics.
NASA Astrophysics Data System (ADS)
Perry, C. T.; Morgan, K. M.
2017-01-01
Sea-surface temperature (SST) warming events, which are projected to increase in frequency and intensity with climate change, represent major threats to coral reefs. How these events impact reef carbonate budgets, and thus the capacity of reefs to sustain vertical growth under rising sea levels, remains poorly quantified. Here we quantify the magnitude of changes that followed the ENSO-induced SST warming that affected the Indian Ocean region in mid-2016. Resultant coral bleaching caused an average 75% reduction in coral cover (present mean 6.2%). Most critically we report major declines in shallow fore-reef carbonate budgets, these shifting from strongly net positive (mean 5.92 G, where G = kg CaCO3 m-2 yr-1) to strongly net negative (mean -2.96 G). These changes have driven major reductions in reef growth potential, which have declined from an average 4.2 to -0.4 mm yr-1. Thus these shallow fore-reef habitats are now in a phase of net erosion. Based on past bleaching recovery trajectories, and predicted increases in bleaching frequency, we predict a prolonged period of suppressed budget and reef growth states. This will limit reef capacity to track IPCC projections of sea-level rise, thus limiting the natural breakwater capacity of these reefs and threatening reef island stability.
Perry, C T; Morgan, K M
2017-01-13
Sea-surface temperature (SST) warming events, which are projected to increase in frequency and intensity with climate change, represent major threats to coral reefs. How these events impact reef carbonate budgets, and thus the capacity of reefs to sustain vertical growth under rising sea levels, remains poorly quantified. Here we quantify the magnitude of changes that followed the ENSO-induced SST warming that affected the Indian Ocean region in mid-2016. Resultant coral bleaching caused an average 75% reduction in coral cover (present mean 6.2%). Most critically we report major declines in shallow fore-reef carbonate budgets, these shifting from strongly net positive (mean 5.92 G, where G = kg CaCO 3 m -2 yr -1 ) to strongly net negative (mean -2.96 G). These changes have driven major reductions in reef growth potential, which have declined from an average 4.2 to -0.4 mm yr -1 . Thus these shallow fore-reef habitats are now in a phase of net erosion. Based on past bleaching recovery trajectories, and predicted increases in bleaching frequency, we predict a prolonged period of suppressed budget and reef growth states. This will limit reef capacity to track IPCC projections of sea-level rise, thus limiting the natural breakwater capacity of these reefs and threatening reef island stability.
Perry, C. T.; Morgan, K. M.
2017-01-01
Sea-surface temperature (SST) warming events, which are projected to increase in frequency and intensity with climate change, represent major threats to coral reefs. How these events impact reef carbonate budgets, and thus the capacity of reefs to sustain vertical growth under rising sea levels, remains poorly quantified. Here we quantify the magnitude of changes that followed the ENSO-induced SST warming that affected the Indian Ocean region in mid-2016. Resultant coral bleaching caused an average 75% reduction in coral cover (present mean 6.2%). Most critically we report major declines in shallow fore-reef carbonate budgets, these shifting from strongly net positive (mean 5.92 G, where G = kg CaCO3 m−2 yr−1) to strongly net negative (mean −2.96 G). These changes have driven major reductions in reef growth potential, which have declined from an average 4.2 to −0.4 mm yr−1. Thus these shallow fore-reef habitats are now in a phase of net erosion. Based on past bleaching recovery trajectories, and predicted increases in bleaching frequency, we predict a prolonged period of suppressed budget and reef growth states. This will limit reef capacity to track IPCC projections of sea-level rise, thus limiting the natural breakwater capacity of these reefs and threatening reef island stability. PMID:28084450
NASA Astrophysics Data System (ADS)
González Manrique, S. J.; Bello González, N.; Denker, C.
2017-04-01
Context. Emerging flux regions mark the first stage in the accumulation of magnetic flux eventually leading to pores, sunspots, and (complex) active regions. These flux regions are highly dynamic, show a variety of fine structure, and in many cases live only for a short time (less than a day) before dissolving quickly into the ubiquitous quiet-Sun magnetic field. Aims: The purpose of this investigation is to characterize the temporal evolution of a minute emerging flux region, the associated photospheric and chromospheric flow fields, and the properties of the accompanying arch filament system. We aim to explore flux emergence and decay processes and investigate if they scale with structure size and magnetic flux contents. Methods: This study is based on imaging spectroscopy with the Göttingen Fabry-Pérot Interferometer at the Vacuum Tower Telescope, Observatorio del Teide, Tenerife, Spain on 2008 August 7. Photospheric horizontal proper motions were measured with Local correlation tracking using broadband images restored with multi-object multi-frame blind deconvolution. Cloud model (CM) inversions of line scans in the strong chromospheric absorption Hαλ656.28 nm line yielded CM parameters (Doppler velocity, Doppler width, optical thickness, and source function), which describe the cool plasma contained in the arch filament system. Results: The high-resolution observations cover the decay and convergence of two micro-pores with diameters of less than one arcsecond and provide decay rates for intensity and area. The photospheric horizontal flow speed is suppressed near the two micro-pores indicating that the magnetic field is already sufficiently strong to affect the convective energy transport. The micro-pores are accompanied by a small arch filament system as seen in Hα, where small-scale loops connect two regions with Hα line-core brightenings containing an emerging flux region with opposite polarities. The Doppler width, optical thickness, and source function reach the largest values near the Hα line-core brightenings. The chromospheric velocity of the cloud material is predominantly directed downwards near the footpoints of the loops with velocities of up to 12 km s-1, whereas loop tops show upward motions of about 3 km s-1. Some of the loops exhibit signs of twisting motions along the loop axis. Conclusions: Micro-pores are the smallest magnetic field concentrations leaving a photometric signature in the photosphere. In the observed case, they are accompanied by a miniature arch filament system indicative of newly emerging flux in the form of Ω-loops. Flux emergence and decay take place on a time-scale of about two days, whereas the photometric decay of the micro-pores is much more rapid (a few hours), which is consistent with the incipient submergence of Ω-loops. Considering lifetime and evolution timescales, impact on the surrounding photospheric proper motions, and flow speed of the chromospheric plasma at the loop tops and footpoints, the results are representative for the smallest emerging flux regions still recognizable as such.
Wheeler, Philip M.; Johnson, Magnus L.
2016-01-01
Artificial reefs in marine protected areas provide additional habitat for biodiversity viewing, and therefore may offer an innovative management solution for managing for coral reef recovery and resilience. Marine park user fees can generate revenue to help manage and maintain natural and artificial reefs. Using a stated preference survey, this study investigates the present consumer surplus associated with visitor use of a marine protected area in Barbados. Two hypothetical markets were presented to differentiate between respondents use values of either: (a) natural reefs within the marine reserve or (b) artificial reef habitat for recreational enhancement. Information was also collected on visitors’ perceptions of artificial reefs, reef material preferences and reef conservation awareness. From a sample of 250 visitors on snorkel trips, we estimate a mean willingness to pay of US$18.33 (median—US$15) for natural reef use and a mean value of US$17.58 (median—US$12.50) for artificial reef use. The number of marine species viewed, age of respondent, familiarity with the Folkestone Marine Reserve and level of environmental concern were statistically significant in influencing willingness to pay. Regression analyses indicate visitors are willing to pay a significant amount to view marine life, especially turtles. Our results suggest that user fees could provide a considerable source of income to aid reef conservation in Barbados. In addition, the substantial use value reported for artificial reefs indicates a reef substitution policy may be supported by visitors to the Folkestone Marine Reserve. We discuss our findings and highlight directions for future research that include the need to collect data to establish visitors’ non-use values to fund reef management. PMID:27547521
Lamb, Joleah B; Willis, Bette L
2011-10-01
Concentrating tourism activities can be an effective way to closely manage high-use parks and minimize the extent of the effects of visitors on plants and animals, although considerable investment in permanent tourism facilities may be required. On coral reefs, a variety of human-related disturbances have been associated with elevated levels of coral disease, but the effects of reef-based tourist facilities (e.g., permanent offshore visitor platforms) on coral health have not been assessed. In partnership with reef managers and the tourism industry, we tested the effectiveness of concentrating tourism activities as a strategy for managing tourism on coral reefs. We compared prevalence of brown band disease, white syndromes, black band disease, skeletal eroding band, and growth anomalies among reefs with and without permanent tourism platforms within the Great Barrier Reef Marine Park. Coral diseases were 15 times more prevalent at reefs with offshore tourism platforms than at nearby reefs without platforms. The maximum prevalence and maximum number of cases of each disease type were recorded at reefs with permanently moored tourism platforms. Diseases affected 10 coral genera from 7 families at reefs with platforms and 4 coral genera from 3 families at reefs without platforms. The greatest number of disease cases occurred within the spatially dominant acroporid corals, which exhibited 18-fold greater disease prevalence at reefs with platforms than at reefs without platforms. Neither the percent cover of acroporids nor overall coral cover differed significantly between reefs with and without platforms, which suggests that neither factor was responsible for the elevated levels of disease. Identifying how tourism activities and platforms facilitate coral disease in marine parks will help ensure ongoing conservation of coral assemblages and tourism. ©2011 Society for Conservation Biology.
NASA Astrophysics Data System (ADS)
Huntington, B. E.; Lirman, D.
2012-12-01
Landscape-scale attributes of patch size, spatial isolation, and topographic complexity are known to influence diversity and abundance in terrestrial and marine systems, but remain collectively untested for reef-building corals. To investigate the relationship between the coral assemblage and seascape variation in reef habitats, we took advantage of the distinct boundaries, spatial configurations, and topographic complexities among artificial reef patches to overcome the difficulties of manipulating natural reefs. Reef size (m2) was found to be the foremost predictor of coral richness in accordance with species-area relationship predictions. Larger reefs were also found to support significantly higher colony densities, enabling us to reject the null hypothesis of random placement (a sampling artifact) in favor of target area predictions that suggest greater rates of immigration on larger reefs. Unlike the pattern previously documented for reef fishes, topographic complexity was not a significant predictor of any coral assemblage response variable, despite the range of complexity values sampled. Lastly, coral colony density was best explained by both increasing reef size and decreasing reef spatial isolation, a pattern found exclusively among brooding species with shorter larval dispersal distances. We conclude that seascape attributes of reef size and spatial configuration within the seascape can influence the species richness and abundance of the coral community at relatively small spatial scales (<1 km). Specifically, we demonstrate how patterns in the coral communities that have naturally established on these manipulated reefs agree with the target area and island biogeography mechanisms to drive species-area relationships in reef-building corals. Based on the patterns documented in artificial reefs, habitat degradation that results in smaller, more isolated natural reefs may compromise coral diversity.
Rinkevich, Baruch
2015-10-01
Nearly all coral reefs bordering nations have experienced net losses in reef biodiversity, goods and services, even without considering the ever-developing global change impacts. In response, this overview wishes to reveal through prospects of active reef-restoration, the currently non-marketed or poorly marketed reef services, focusing on a single coral species (Stylophora pistillata). It is implied that the integration of equity capitals and other commodification with reef-restoration practices will improve total reef services. Two tiers of market-related activities are defined, the traditional first-tier instruments (valuating costs/gains for extracting tradable goods and services) and novel second-tier instruments (new/expanded monetary tools developed as by-products of reef restoration measures). The emerging new suite of economic mechanisms based on restoration methodologies could be served as an incentive for ecosystem conservation, enhancing the sum values of all services generated by coral reefs, where the same stocks of farmed/transplanted coral colonies will be used as market instruments. I found that active restoration measures disclose 12 classes of second-tier goods and services, which may partly/wholly finance restoration acts, bringing to light reef capitalizations that allow the expansion of markets with products that have not been considered before. The degree to which the second tier of market-related services could buffer coral-reef degradation is still unclear and would vary with different reef types and in various reef restoration scenarios; however, reducing the uncertainty associated with restoration. It is expected that the expansion of markets with the new products and the enhancement of those already existing will be materialized even if reef ecosystems will recover into different statuses. Copyright © 2015 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Johnson, Jamie; Perry, Chris; Smithers, Scott; Morgan, Kyle
2016-04-01
Declining water quality due to river catchment modification since European settlement (c. 1850 A.D.) represents a major threat to the health of coral reefs on Australia's Great Barrier Reef (GBR), particularly for those located in the coastal waters of the GBR's inner-shelf. These nearshore reefs are widely perceived to be most susceptible to declining water quality owing to their close proximity to river point sources. Despite this, nearshore reefs have been relatively poorly studied with the impacts and magnitudes of environmental degradation still remaining unclear. This is largely due to ongoing debates concerning the significance of increased sediment yields against naturally high background sedimentary regimes. Benthic foraminifera are increasingly used as tools for monitoring environmental and ecological change on coral reefs. On the GBR, the majority of studies have focussed on the spatial distributions of contemporary benthic foraminiferal assemblages. While baseline assemblages from other environments (e.g. inshore reefs and mangroves) have been described, very few records exist for nearshore reefs. Here, we present preliminary results from the first palaeoecological study of foraminiferal assemblages of nearshore reefs on the central GBR. Cores were recovered from the nearshore reef complex at Paluma Shoals using percussion techniques. Recovery was 100%, capturing the entire Holocene reef sequence of the selected reef structures. Radiocarbon dating and subsequent age-depth modelling techniques were used to identify reef sequences pre-dating European settlement. Benthic foraminifera assemblages were reconstructed from the identified sequences to establish pre-European ecological baselines with the aim of providing a record of foraminiferal distribution during vertical reef accretion and against which contemporary ecological change may be assessed.
Andradi-Brown, Dominic A; Head, Catherine E I; Exton, Dan A; Hunt, Christina L; Hendrix, Alicia; Gress, Erika; Rogers, Alex D
2017-01-01
Mesophotic coral ecosystems (MCEs, reefs 30-150 m) are understudied, yet the limited research conducted has been biased towards large sessile taxa, such as scleractinian corals and sponges, or mobile taxa such as fishes. Here we investigate zooplankton communities on shallow reefs and MCEs around Utila on the southern Mesoamerican Barrier Reef using planktonic light traps. Zooplankton samples were sorted into broad taxonomic groups. Our results indicate similar taxonomic zooplankton richness and overall biomass between shallow reefs and MCEs. However, the abundance of larger bodied (>2 mm) zooplanktonic groups, including decapod crab zoea, mysid shrimps and peracarid crustaceans, was higher on MCEs than shallow reefs. Our findings highlight the importance of considering zooplankton when identifying broader reef community shifts across the shallow reef to MCE depth gradient.
NASA Astrophysics Data System (ADS)
Djuricic, Ana; Puttonen, Eetu; Harzhauser, Mathias; Dorninger, Peter; Székely, Balázs; Mandic, Oleg; Nothegger, Clemens; Molnár, Gábor; Pfeifer, Norbert
2016-04-01
The world's largest fossilized oyster reef is located in Stetten, Lower Austria excavated during field campaigns of the Natural History Museum Vienna between 2005 and 2008. It is studied in paleontology to learn about change in climate from past events. In order to support this study, a laser scanning and photogrammetric campaign was organized in 2014 for 3D documentation of the large and complex site. The 3D point clouds and high resolution images from this field campaign are visualized by photogrammetric methods in form of digital surface models (DSM, 1 mm resolution) and orthophoto (0.5 mm resolution) to help paleontological interpretation of data. Due to size of the reef, automated analysis techniques are needed to interpret all digital data obtained from the field. One of the key components in successful automation is detection of oyster shell edges. We have tested Reflectance Transformation Imaging (RTI) to visualize the reef data sets for end-users through a cultural heritage viewing interface (RTIViewer). The implementation includes a Lambert shading method to visualize DSMs derived from terrestrial laser scanning using scientific software OPALS. In contrast to shaded RTI no devices consisting of a hardware system with LED lights, or a body to rotate the light source around the object are needed. The gray value for a given shaded pixel is related to the angle between light source and the normal at that position. Brighter values correspond to the slope surfaces facing the light source. Increasing of zenith angle results in internal shading all over the reef surface. In total, oyster reef surface contains 81 DSMs with 3 m x 2 m each. Their surface was illuminated by moving the virtual sun every 30 degrees (12 azimuth angles from 20-350) and every 20 degrees (4 zenith angles from 20-80). This technique provides paleontologists an interactive approach to virtually inspect the oyster reef, and to interpret the shell surface by changing the light source direction. One source of light for shading does show all morphologic features needed for description. Additionally, more details such as fault lines, overlaps and characteristic edges of complex shell structures are clearly detected by simply changing the illumination on the shaded digital surface model. In a further study, the potential of edge detection of the individual shells will be analyzed based on statistical analysis by keeping track of the local accumulative shading gradient. The results are compared to manually identified edges. In a following study phase, the detected edges will be improved by graph cut segmentation. We assume that this technique can lead to automatically extracted teaching set for object segmentation on a complex environment. The project is supported by the Austrian Science Fund (FWF P 25883-N29).
75 FR 48934 - Coral Reef Conservation Program Implementation Guidelines
Federal Register 2010, 2011, 2012, 2013, 2014
2010-08-12
...-01] RIN 0648-ZC19 Coral Reef Conservation Program Implementation Guidelines AGENCY: National Oceanic... Guidelines (Guidelines) for the Coral Reef Conservation Program (CRCP or Program) under the Coral Reef... assistance for coral reef conservation projects under the Act. NOAA revised the Implementation Guidelines for...
Shinn, E.A.; Hudson, J.H.; Halley, R.B.; Lidz, B.H.; Taylor, D.L.
1977-01-01
Core drilling and examination of underwater excavation on 6 reef sites in south Florida and Dry Tortugas revealed that underlying topography is the major factor controlling reef morphology. Carbon-14 dating on coral recovered from cores enables calculation of accumulation rates. Accumulation rates were found to range from 0.38 m/1000 years in thin Holocene reefs to as much as 4.85 m/1000 years in thicker buildups. Cementation and alteration of corals were found to be more pronounced in areas of low buildup rates than in areas of rapid accumulation rates. Acropora palmata, generally considered the major reef builder in Florida, was found to be absent in most reefs drilled. At Dry Tortugas, the more than 13-meter thick Holocene reef did not contain A. palmata. The principal reef builders in this outer reef are the same as those which built the Pleistocene Key Largo formation, long considered to be fossilized patch reef complex.
Impact of sea-level rise and coral mortality on the wave dynamics and wave forces on barrier reefs.
Baldock, T E; Golshani, A; Callaghan, D P; Saunders, M I; Mumby, P J
2014-06-15
A one-dimensional wave model was used to investigate the reef top wave dynamics across a large suite of idealized reef-lagoon profiles, representing barrier coral reef systems under different sea-level rise (SLR) scenarios. The modeling shows that the impacts of SLR vary spatially and are strongly influenced by the bathymetry of the reef and coral type. A complex response occurs for the wave orbital velocity and forces on corals, such that the changes in the wave dynamics vary reef by reef. Different wave loading regimes on massive and branching corals also leads to contrasting impacts from SLR. For many reef bathymetries, wave orbital velocities increase with SLR and cyclonic wave forces are reduced for certain coral species. These changes may be beneficial to coral health and colony resilience and imply that predicting SLR impacts on coral reefs requires careful consideration of the reef bathymetry and the mix of coral species. Copyright © 2014 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Bridge, T.; Scott, A.; Steinberg, D.
2012-12-01
Anemonefishes and their host sea anemones are iconic inhabitants of coral reef ecosystems. While studies have documented their abundance in shallow-water reef habitats in parts of the Indo-Pacific, none have examined these species on mesophotic reefs. In this study, we used autonomous underwater vehicle imagery to examine the abundance and diversity of anemones and anemonefishes at Viper Reef and Hydrographers Passage in the central Great Barrier Reef at depths between 50 and 65 m. A total of 37 host sea anemones (31 Entacmaea quadricolor and 6 Heteractis crispa) and 24 anemonefishes (23 Amphiprion akindynos and 1 A. perideraion) were observed. Densities were highest at Viper Reef, with 8.48 E. quadricolor and A. akindynos per 100 m2 of reef substratum. These results support the hypothesis that mesophotic reefs have many species common to shallow-water coral reefs and that many taxa may occur at depths greater than currently recognised.
Marcos, Ma Shiela Angeli; David, Laura; Peñaflor, Eileen; Ticzon, Victor; Soriano, Maricor
2008-10-01
We introduce an automated benthic counting system in application for rapid reef assessment that utilizes computer vision on subsurface underwater reef video. Video acquisition was executed by lowering a submersible bullet-type camera from a motor boat while moving across the reef area. A GPS and echo sounder were linked to the video recorder to record bathymetry and location points. Analysis of living and non-living components was implemented through image color and texture feature extraction from the reef video frames and classification via Linear Discriminant Analysis. Compared to common rapid reef assessment protocols, our system can perform fine scale data acquisition and processing in one day. Reef video was acquired in Ngedarrak Reef, Koror, Republic of Palau. Overall success performance ranges from 60% to 77% for depths of 1 to 3 m. The development of an automated rapid reef classification system is most promising for reef studies that need fast and frequent data acquisition of percent cover of living and nonliving components.
Humphries, Austin T.; LaPeyre, Megan K.; Kimball, Matthew E.; Rozas, Lawrence P.
2011-01-01
Structurally complex habitats are often associated with more diverse and abundant species assemblages in both aquatic and terrestrial ecosystems. Biogenic reefs formed by the eastern oyster (Crassostrea virginica) are complex in nature and are recognized for their potential habitat value in estuarine systems along the US Atlantic and Gulf of Mexico coasts. Few studies, however, have examined the response of nekton to structural complexity within oyster reefs. We used a quantitative sampling technique to examine how the presence and complexity of experimental oyster reefs influence the abundance, biomass, and distribution of nekton by sampling reefs 4 months and 16 months post-construction. Experimental oyster reefs were colonized immediately by resident fishes and decapod crustaceans, and reefs supported a distinct nekton assemblage compared to mud-bottom habitat. Neither increased reef complexity, nor age of the experimental reef resulted in further changes in nekton assemblages or increases in nekton abundance or diversity. The presence of oyster reefs per se was the most important factor determining nekton usage.
Variability in daily pH scales with coral reef accretion and community structure
NASA Astrophysics Data System (ADS)
Price, N.; Martz, T.; Brainard, R. E.; Smith, J.
2011-12-01
Little is known about natural variability in pH in coastal waters and how resident organisms respond to current nearshore seawater conditions. We used autonomous sensors (SeaFETs) to record temperature and, for the first time, pH with high temporal (hourly observations; 7 months of sampling) resolution on the reef benthos (5-10m depth) at several islands (Kingman, Palmyra and Jarvis) within the newly designated Pacific Remote Island Areas Marine National Monument (PRIMNM) in the northern Line Islands; these islands are uninhabited and lack potentially confounding local impacts (e.g. pollution and overfishing). Recorded benthic pH values were compared with regional means and minimum thresholds based on seasonal amplitude estimated from surrounding open-ocean climatological data, which represent seawater chemistry values in the absence of feedback from the reef. Each SeaFET sensor was co-located with replicate Calcification/Acidification Units (CAUs) designed to quantify species abundances and net community calcification rates so we could determine which, if any, metrics of natural variability in benthic pH and temperature were related to community development and reef accretion rates. The observed range in daily pH encompassed maximums reported from the last century (8.104 in the early evening) to minimums approaching projected levels within the next 100 yrs (7.824 at dawn) for pelagic waters. Net reef calcification rates, measured as calcium carbonate accretion on CAUs, varied within and among islands and were comparable with rates measured from the Pacific and Caribbean using chemistry-based approaches. Benthic species assemblages on the CAUs were differentiated by the presence of calcifying and fleshy taxa (CAP analysis, mean allocation success 80%, δ2 = 0.886, P = <0.001). In general, accretion rates were higher at sites that had a greater number of hours at high pH values each day. Where daily pH failed to exceed climatological seasonal minimum thresholds, net accretion was slower and fleshy, non-calcifying benthic organisms dominated. Natural variation in benthic pH offers a unique opportunity to study ecological consequences of likely future ocean chemistry.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Saller, A.H.; Schlanger, S.O.
Two wells drilled along the margin of Enewetak Atoll penetrated approximately 1,000 m of upper eocene, Oligocene, and lower Miocene carbonates. STrontium isotope stratigraphy indicates relatively continuous deposition of carbonate from 40 Ma to 20 Ma. Depositional environments show a gradual basinward progradation of facies with slope carbonates passing upward into fore-reef, reef, back-reef, and lagoonal carbonates. Slope strata contain wackestones and packstones with submarine-cemented lithoclasts, coral, coralline algae fragments, benthic rotaline forams, planktonic forams, and echinoderm fragments. Fore-reef strata are dominantly packstones and boundstones containing large pieces of coral, abundant benthic forams, coralline algae fragments, stromatoporoids(.), and minor planktonicmore » forams. Reef and near-reef sediments include coralgal boundstones and grainstones with abundant benthic forams. Halimeda and miliolid forams are common in lagoonward parts of the back reef. Sponge borings, geopetal structures, and fractures are common in reef and fore-reef strata. Lagoonal strata are wackestones and packstones with common mollusks, coral, coralline algae, and benthic forams (rotaline and miliolid). Diagenesis has extensively altered strata near the atoll margin. Aragonite dissolution and calcite cements (radiaxial and cloudy prismatic are abundant in fore-reef, reef, and some back-reef strata). Petrographic and geochemical data indicate arogonite dissolution and calcite cementation in seawater at burial depths of 100 to 300 m. Dolomite occurs in slope and deeply buried reefal carbonates.« less
Belhassen, Yaniv; Rousseau, Meghan; Tynyakov, Jenny; Shashar, Nadav
2017-12-01
Artificial reefs are increasingly being used around the globe to attract recreational divers, for both environmental and commercial reasons. This paper examines artificial coral reefs as recreational ecosystem services (RES) by evaluating their attractiveness and effectiveness and by examining divers' attitudes toward them. An online survey targeted at divers in Israel (n = 263) indicated that 35% of the dives in Eilat (a resort city on the shore of the Red Sea) take place at artificial reefs. A second study monitored divers' behavior around the Tamar artificial reef, one of the most popular submerged artificial reefs in Eilat, and juxtaposed it with divers' activities around two adjacent natural reefs. Findings show that the average diver density at the artificial reef was higher than at the two nearby natural knolls and that the artificial reef effectively diverts divers from natural knolls. A third study that examined the attitudes towards natural vs. artificial reefs found that the artificial reefs are considered more appropriate for training, but that divers feel less relaxed around them. By utilizing the RES approach as a framework, the study offers a comprehensive methodology that brings together the aesthetic, behavioral, and attitudinal aspects in terms of which artificial reefs can be evaluated. Copyright © 2017 Elsevier Ltd. All rights reserved.
Workshop on Biological Integrity of Coral Reefs August 21-22 ...
This report summarizes an EPA-sponsored workshop on coral reef biological integrity held at the Caribbean Coral Reef Institute in La Parguera, Puerto Rico on August 21-22, 2012. The goals of this workshop were to:• Identify key qualitative and quantitative ecological characteristics (reef attributes) that determine the condition of linear coral reefs inhabiting shallow waters (<12 m) in southwestern Puerto Rico.• Use those reef attributes to recommend categorical condition rankings for establishing a biological condition gradient.• Ascertain through expert consensus those reef attributes that characterize biological integrity (a natural, fully-functioning system of organisms and communities) for coral reefs. • Develop a conceptual, narrative model that describes how biological attributes of coral reefs change along a gradient of increasing anthropogenic stress.The workshop brought together scientists with expertise in coral reef taxonomic groups (e.g., stony corals, fishes, sponges, gorgonians, algae, seagrasses and macroinvertebrates), as well as community structure, organism condition, ecosystem function and ecosystem connectivity. The experts evaluated photos and videos from 12 stations collected during EPA Coral Reef surveys (2010 & 2011) from Puerto Rico on coral reefs exhibiting a wide range of conditions. The experts individually rated each station as to observed condition (“good”, “fair” or “poor”) and documented their rationale for
Pennsylvanian stratigraphic reefs in Kansas, some modern comparisons and implications
Heckel, P.H.
1972-01-01
Broad platformlike buildups in the Stanton Limestone in southeastern Kansas are composed primarily of lime mud and phylloid algae and are rimmed with skeletal calcarenite composed largely of echinoderm and algal debris. Bordering the buildups are large (1??30 km) channels, lined or filled with similar calcarenite, and a broader basin containing shaly skeletal calcilutite. Grain abrasion and spar cement in the rimming calcarenites indicate water agitation and suggest wave resistance of the buildups during growth. Wave resistance may have been provided by 1) stalked echinoderms, which are resilient when alive and bind sediment with their roots, and also by 2) early drusy cementation of loose sediment to a coherent mass. Comparison to modern channel-separated buildups in the Persian Gulf and the Great Barrier Reef complex brings out the relative significance of organic frameworks in these different geologic settings. Recognized organic frameworks range from absent or insignificant in the Pennsylvanian examples through locally present but insignificant in the Persian Gulf, to apparently important in maintaining the buildups in the Great Barrier Reef. All three examples, however, exhibit patterns of original hydrodynamic control over initiation and gross form of the buildups. Determining significance of organic frameworks to overall buildup growth involves examining both their positions relative to evidence of wave action and the nature of binding in contemporaneous talus produced by wave action on the buildup. ?? 1972 Ferdinand Enke Verlag Stuttgart.
NASA Astrophysics Data System (ADS)
Piñeros, Victor Julio; Gutiérrez-Rodríguez, Carla
2017-09-01
We assessed geographic patterns of genetic variation and connectivity in the widely distributed coral-reef fish Abudefduf saxatilis at different temporal scales. We sequenced two mitochondrial regions (cytochrome b and control region) and genotyped 12 microsatellite loci in a total of 296 individuals collected from 14 reefs in two biogeographic provinces in the tropical western Atlantic Ocean and from three provinces within the Caribbean Sea. We used phylogeography, population genetics and coalescent methods to assess the potential effects of climatic oscillations in the Pleistocene and contemporary oceanographic barriers on the population genetic structure and connectivity of the species. Sequence analyses indicated high genetic diversity and a lack of genetic differentiation throughout the Caribbean and between the two biogeographic provinces. Different lines of evidence depicted demographic expansions of A. saxatilis populations dated to the Pleistocene. The microsatellites exhibited high genetic diversity, and no genetic differentiation was detected within the Caribbean; however, these markers identified a genetic discontinuity between the two western Atlantic biogeographic provinces. Migration estimates revealed gene flow across the Amazon-Orinoco Plume, suggesting that genetic divergence may be promoted by differential environmental conditions on either side of the barrier. The climatic oscillations of the Pleistocene, together with oceanographic barriers and the dispersal potential of the species, constitute important factors determining the geographic patterns of genetic variation in A. saxatilis.
Catastrophic impact of typhoon waves on coral communities in the Ryukyu Islands under global warming
NASA Astrophysics Data System (ADS)
Hongo, Chuki; Kawamata, Hideki; Goto, Kazuhisa
2012-06-01
Typhoon-generated storm waves generally cause mechanical damage to coral communities on present-day reefs, and the magnitude and extent of damage is predicted to increase in the near future as a result of global warming. Therefore, a comprehensive understanding of potential future scenarios of reef ecosystems is of prime interest. This study assesses the current status of coral communities on Ibaruma reef, Ryukyu Islands, on the basis of field observations, engineering and fluid dynamic models, and calculations of wave motion, and predicts the potential effects of a super-extreme typhoon (incident wave height,H = 20 m; wave period, T = 20 s) on the reef. On the present-day reef, massive corals occur in shallow lagoons and tabular corals occur from the reef crest to the reef slope. The observed distribution of corals, which is frequently attacked by moderate (H = 10 m, T = 10 s) and extreme (H = 10 m, T = 15 s) typhoons, is consistent with the predictions of engineering models. Moreover, this study indicates that if a super-extreme typhoon attacks the reef in the near future, massive corals will survive in the shallow lagoons but tabular corals on the reef crest and reef slope will be severely impacted. The findings imply that super-extreme typhoons will cause a loss of species diversity, as the tabular corals are important reef builders and are critical to the maintenance of reef ecosystems. Consequently, reef restoration is a key approach to maintaining reef ecosystems in the wake of super-extreme typhoons.
NASA Astrophysics Data System (ADS)
Wilkinson, Clive R.; Evans, Elizabeth
1989-06-01
Sponge populations were surveyed at different depths in three zones of Davies Reef, a large platform reef of the central Great Barrier Reef. Depth is the major discriminatory factor as few sponges are found within the first 10 m depth and maximal populations occur between 15 m and 30 m on fore-reef, lagoon and back-reef slopes. Reef location is another major factor, with the lagoon containing a significantly different sponge population to either the fore-reef or the back-reef slopes. Physical factors are considered to be the major influences behind these patterns. Physical turbulence is strongest within the first 10 m and apparently limits sponge growth within these shallow zones. Insufficient photosynthetic radiation limits the growth of the sponge population below 30 m depth as many of the species are phototrophic with a dependence on cyanobacterial symbionts for nutrition. Sponge populations on the outer (fore- and back-) reef slopes are comparable with each other but different from those on lagoon slopes where currents are reduced and fine sediment loads are higher. The largest populations occur on the back-reef slope where currents are stronger and there are possibly higher concentrations of organic nutrients originating from the more productive shallow parts of the reef. While there are correlations between sponge populations and environmental parameters, data are insufficient to enable more definitive conclusions to be drawn. Most sponge species are distributed widely over the reef, however, some are restricted to a few habitats and, hence, may be used to characterize those habitats.
Barnett, Adam; Abrantes, Kátya G.; Seymour, Jamie; Fitzpatrick, Richard
2012-01-01
Although marine protected areas (MPAs) are a common conservation strategy, these areas are often designed with little prior knowledge of the spatial behaviour of the species they are designed to protect. Currently, the Coral Sea area and its seamounts (north-east Australia) are under review to determine if MPAs are warranted. The protection of sharks at these seamounts should be an integral component of conservation plans. Therefore, knowledge on the spatial ecology of sharks at the Coral Sea seamounts is essential for the appropriate implementation of management and conservation plans. Acoustic telemetry was used to determine residency, site fidelity and spatial use of three shark species at Osprey Reef: whitetip reef sharks Triaenodon obesus, grey reef sharks Carcharhinus amblyrhynchos and silvertip sharks Carcharhinus albimarginatus. Most individuals showed year round residency at Osprey Reef, although five of the 49 individuals tagged moved to the neighbouring Shark Reef (∼14 km away) and one grey reef shark completed a round trip of ∼250 km to the Great Barrier Reef. Additionally, individuals of white tip and grey reef sharks showed strong site fidelity to the areas they were tagged, and there was low spatial overlap between groups of sharks tagged at different locations. Spatial use at Osprey Reef by adult sharks is generally restricted to the north-west corner. The high residency and limited spatial use of Osprey Reef suggests that reef sharks would be highly vulnerable to targeted fishing pressure and that MPAs incorporating no-take of sharks would be effective in protecting reef shark populations at Osprey and Shark Reef. PMID:22615782
Barnett, Adam; Abrantes, Kátya G; Seymour, Jamie; Fitzpatrick, Richard
2012-01-01
Although marine protected areas (MPAs) are a common conservation strategy, these areas are often designed with little prior knowledge of the spatial behaviour of the species they are designed to protect. Currently, the Coral Sea area and its seamounts (north-east Australia) are under review to determine if MPAs are warranted. The protection of sharks at these seamounts should be an integral component of conservation plans. Therefore, knowledge on the spatial ecology of sharks at the Coral Sea seamounts is essential for the appropriate implementation of management and conservation plans. Acoustic telemetry was used to determine residency, site fidelity and spatial use of three shark species at Osprey Reef: whitetip reef sharks Triaenodon obesus, grey reef sharks Carcharhinus amblyrhynchos and silvertip sharks Carcharhinus albimarginatus. Most individuals showed year round residency at Osprey Reef, although five of the 49 individuals tagged moved to the neighbouring Shark Reef (~14 km away) and one grey reef shark completed a round trip of ~250 km to the Great Barrier Reef. Additionally, individuals of white tip and grey reef sharks showed strong site fidelity to the areas they were tagged, and there was low spatial overlap between groups of sharks tagged at different locations. Spatial use at Osprey Reef by adult sharks is generally restricted to the north-west corner. The high residency and limited spatial use of Osprey Reef suggests that reef sharks would be highly vulnerable to targeted fishing pressure and that MPAs incorporating no-take of sharks would be effective in protecting reef shark populations at Osprey and Shark Reef.
Two waves of colonization straddling the K-Pg boundary formed the modern reef fish fauna.
Price, S A; Schmitz, L; Oufiero, C E; Eytan, R I; Dornburg, A; Smith, W L; Friedman, M; Near, T J; Wainwright, P C
2014-05-22
Living reef fishes are one of the most diverse vertebrate assemblages on Earth. Despite its prominence and ecological importance, the origins and assembly of the reef fish fauna is poorly described. A patchy fossil record suggests that the major colonization of reef habitats must have occurred in the Late Cretaceous and early Palaeogene, with the earliest known modern fossil coral reef fish assemblage dated to 50 Ma. Using a phylogenetic approach, we analysed the early evolutionary dynamics of modern reef fishes. We find that reef lineages successively colonized reef habitats throughout the Late Cretaceous and early Palaeogene. Two waves of invasion were accompanied by increasing morphological convergence: one in the Late Cretaceous from 90 to 72 Ma and the other immediately following the end-Cretaceous mass extinction. The surge in reef invasions after the Cretaceous-Palaeogene boundary continued for 10 Myr, after which the pace of transitions to reef habitats slowed. Combined, these patterns match a classic niche-filling scenario: early transitions to reefs were made rapidly by morphologically distinct lineages and were followed by a decrease in the rate of invasions and eventual saturation of morphospace. Major alterations in reef composition, distribution and abundance, along with shifts in climate and oceanic currents, occurred during the Late Cretaceous and early Palaeogene interval. A causal mechanism between these changes and concurrent episodes of reef invasion remains obscure, but what is clear is that the broad framework of the modern reef fish fauna was in place within 10 Myr of the end-Cretaceous extinction.
Two waves of colonization straddling the K–Pg boundary formed the modern reef fish fauna
Price, S. A.; Schmitz, L.; Oufiero, C. E.; Eytan, R. I.; Dornburg, A.; Smith, W. L.; Friedman, M.; Near, T. J.; Wainwright, P. C.
2014-01-01
Living reef fishes are one of the most diverse vertebrate assemblages on Earth. Despite its prominence and ecological importance, the origins and assembly of the reef fish fauna is poorly described. A patchy fossil record suggests that the major colonization of reef habitats must have occurred in the Late Cretaceous and early Palaeogene, with the earliest known modern fossil coral reef fish assemblage dated to 50 Ma. Using a phylogenetic approach, we analysed the early evolutionary dynamics of modern reef fishes. We find that reef lineages successively colonized reef habitats throughout the Late Cretaceous and early Palaeogene. Two waves of invasion were accompanied by increasing morphological convergence: one in the Late Cretaceous from 90 to 72 Ma and the other immediately following the end-Cretaceous mass extinction. The surge in reef invasions after the Cretaceous–Palaeogene boundary continued for 10 Myr, after which the pace of transitions to reef habitats slowed. Combined, these patterns match a classic niche-filling scenario: early transitions to reefs were made rapidly by morphologically distinct lineages and were followed by a decrease in the rate of invasions and eventual saturation of morphospace. Major alterations in reef composition, distribution and abundance, along with shifts in climate and oceanic currents, occurred during the Late Cretaceous and early Palaeogene interval. A causal mechanism between these changes and concurrent episodes of reef invasion remains obscure, but what is clear is that the broad framework of the modern reef fish fauna was in place within 10 Myr of the end-Cretaceous extinction. PMID:24695431
A geological perspective on the degradation and conservation of western Atlantic coral reefs
Kuffner, Ilsa B.; Toth, Lauren T.
2016-01-01
Continuing coral-reef degradation in the western Atlantic is resulting in loss of ecological and geologic functions of reefs. With the goal of assisting resource managers and stewards of reefs in setting and measuring progress toward realistic goals for coral-reef conservation and restoration, we examined reef degradation in this region from a geological perspective. The importance of ecosystem services provided by coral reefs—as breakwaters that dissipate wave energy and protect shorelines and as providers of habitat for innumerable species—cannot be overstated. However, the few coral species responsible for reef building in the western Atlantic during the last approximately 1.5 million years are not thriving in the 21st century. These species are highly sensitive to abrupt temperature extremes, prone to disease infection, and have low sexual reproductive potential. Their vulnerability and the low functional redundancy of branching corals have led to the low resilience of western Atlantic reef ecosystems. The decrease in live coral cover over the last 50 years highlights the need for study of relict (senescent) reefs, which, from the perspective of coastline protection and habitat structure, may be just as important to conserve as the living coral veneer. Research is needed to characterize the geological processes of bioerosion, reef cementation, and sediment transport as they relate to modern-day changes in reef elevation. For example, although parrotfish remove nuisance macroalgae, possibly promoting coral recruitment, they will not save Atlantic reefs from geological degradation. In fact, these fish are quickly nibbling away significant quantities of Holocene reef framework. The question of how different biota covering dead reefs affect framework resistance to biological and physical erosion needs to be addressed. Monitoring and managing reefs with respect to physical resilience, in addition to ecological resilience, could optimize the expenditure of resources in conserving Atlantic reefs and the services they provide.
Graham, Nicholas A. J.; Chong-Seng, Karen M.; Huchery, Cindy; Januchowski-Hartley, Fraser A.; Nash, Kirsty L.
2014-01-01
Much research on coral reefs has documented differential declines in coral and associated organisms. In order to contextualise this general degradation, research on community composition is necessary in the context of varied disturbance histories and the biological processes and physical features thought to retard or promote recovery. We conducted a spatial assessment of coral reef communities across five reefs of the central Great Barrier Reef, Australia, with known disturbance histories, and assessed patterns of coral cover and community composition related to a range of other variables thought to be important for reef dynamics. Two of the reefs had not been extensively disturbed for at least 15 years prior to the surveys. Three of the reefs had been severely impacted by crown-of-thorns starfish outbreaks and coral bleaching approximately a decade before the surveys, from which only one of them was showing signs of recovery based on independent surveys. We incorporated wave exposure (sheltered and exposed) and reef zone (slope, crest and flat) into our design, providing a comprehensive assessment of the spatial patterns in community composition on these reefs. Categorising corals into life history groupings, we document major coral community differences in the unrecovered reefs, compared to the composition and covers found on the undisturbed reefs. The recovered reef, despite having similar coral cover, had a different community composition from the undisturbed reefs, which may indicate slow successional processes, or a different natural community dominance pattern due to hydrology and other oceanographic factors. The variables that best correlated with patterns in the coral community among sites included the density of juvenile corals, herbivore fish biomass, fish species richness and the cover of macroalgae. Given increasing impacts to the Great Barrier Reef, efforts to mitigate local stressors will be imperative to encouraging coral communities to persist into the future. PMID:24983747
Re-creating missing population baselines for Pacific reef sharks.
Nadon, Marc O; Baum, Julia K; Williams, Ivor D; McPherson, Jana M; Zgliczynski, Brian J; Richards, Benjamin L; Schroeder, Robert E; Brainard, Russell E
2012-06-01
Sharks and other large predators are scarce on most coral reefs, but studies of their historical ecology provide qualitative evidence that predators were once numerous in these ecosystems. Quantifying density of sharks in the absence of humans (baseline) is, however, hindered by a paucity of pertinent time-series data. Recently researchers have used underwater visual surveys, primarily of limited spatial extent or nonstandard design, to infer negative associations between reef shark abundance and human populations. We analyzed data from 1607 towed-diver surveys (>1 ha transects surveyed by observers towed behind a boat) conducted at 46 reefs in the central-western Pacific Ocean, reefs that included some of the world's most pristine coral reefs. Estimates of shark density from towed-diver surveys were substantially lower (<10%) than published estimates from surveys along small transects (<0.02 ha), which is not consistent with inverted biomass pyramids (predator biomass greater than prey biomass) reported by other researchers for pristine reefs. We examined the relation between the density of reef sharks observed in towed-diver surveys and human population in models that accounted for the influence of oceanic primary productivity, sea surface temperature, reef area, and reef physical complexity. We used these models to estimate the density of sharks in the absence of humans. Densities of gray reef sharks (Carcharhinus amblyrhynchos), whitetip reef sharks (Triaenodon obesus), and the group "all reef sharks" increased substantially as human population decreased and as primary productivity and minimum sea surface temperature (or reef area, which was highly correlated with temperature) increased. Simulated baseline densities of reef sharks under the absence of humans were 1.1-2.4/ha for the main Hawaiian Islands, 1.2-2.4/ha for inhabited islands of American Samoa, and 0.9-2.1/ha for inhabited islands in the Mariana Archipelago, which suggests that density of reef sharks has declined to 3-10% of baseline levels in these areas. ©2012 Society for Conservation Biology No claim to original US government works.
Gurney, Georgina G.; Melbourne-Thomas, Jessica; Geronimo, Rollan C.; Aliño, Perry M.; Johnson, Craig R.
2013-01-01
Climate change has emerged as a principal threat to coral reefs, and is expected to exacerbate coral reef degradation caused by more localised stressors. Management of local stressors is widely advocated to bolster coral reef resilience, but the extent to which management of local stressors might affect future trajectories of reef state remains unclear. This is in part because of limited understanding of the cumulative impact of multiple stressors. Models are ideal tools to aid understanding of future reef state under alternative management and climatic scenarios, but to date few have been sufficiently developed to be useful as decision support tools for local management of coral reefs subject to multiple stressors. We used a simulation model of coral reefs to investigate the extent to which the management of local stressors (namely poor water quality and fishing) might influence future reef state under varying climatic scenarios relating to coral bleaching. We parameterised the model for Bolinao, the Philippines, and explored how simulation modelling can be used to provide decision support for local management. We found that management of water quality, and to a lesser extent fishing, can have a significant impact on future reef state, including coral recovery following bleaching-induced mortality. The stressors we examined interacted antagonistically to affect reef state, highlighting the importance of considering the combined impact of multiple stressors rather than considering them individually. Further, by providing explicit guidance for management of Bolinao's reef system, such as which course of management action will most likely to be effective over what time scales and at which sites, we demonstrated the utility of simulation models for supporting management. Aside from providing explicit guidance for management of Bolinao's reef system, our study offers insights which could inform reef management more broadly, as well as general understanding of reef systems. PMID:24260347
Gurney, Georgina G; Melbourne-Thomas, Jessica; Geronimo, Rollan C; Aliño, Perry M; Johnson, Craig R
2013-01-01
Climate change has emerged as a principal threat to coral reefs, and is expected to exacerbate coral reef degradation caused by more localised stressors. Management of local stressors is widely advocated to bolster coral reef resilience, but the extent to which management of local stressors might affect future trajectories of reef state remains unclear. This is in part because of limited understanding of the cumulative impact of multiple stressors. Models are ideal tools to aid understanding of future reef state under alternative management and climatic scenarios, but to date few have been sufficiently developed to be useful as decision support tools for local management of coral reefs subject to multiple stressors. We used a simulation model of coral reefs to investigate the extent to which the management of local stressors (namely poor water quality and fishing) might influence future reef state under varying climatic scenarios relating to coral bleaching. We parameterised the model for Bolinao, the Philippines, and explored how simulation modelling can be used to provide decision support for local management. We found that management of water quality, and to a lesser extent fishing, can have a significant impact on future reef state, including coral recovery following bleaching-induced mortality. The stressors we examined interacted antagonistically to affect reef state, highlighting the importance of considering the combined impact of multiple stressors rather than considering them individually. Further, by providing explicit guidance for management of Bolinao's reef system, such as which course of management action will most likely to be effective over what time scales and at which sites, we demonstrated the utility of simulation models for supporting management. Aside from providing explicit guidance for management of Bolinao's reef system, our study offers insights which could inform reef management more broadly, as well as general understanding of reef systems.
Coral reefs provide the ecological foundation for productive and diverse fish and invertebrate communities that support multibillion dollar reef fishing and tourism industries. Yet reefs are threatened by growing coastal development, climate change, and over-exploitation. A key i...
The role of coral reef rugosity in dissipating wave energy and coastal protection
NASA Astrophysics Data System (ADS)
Harris, Daniel; Rovere, Alessio; Parravicini, Valeriano; Casella, Elisa
2016-04-01
Coral reefs are the most effective natural barrier in dissipating wave energy through breaking and bed friction. The attenuation of wave energy by coral reef flats is essential in the protection and stability of coral reef aligned coasts and reef islands. However, the effectiveness of wave energy dissipation by coral reefs may be diminished under future climate change scenarios with a potential reduction of coral reef rugosity due to increased stress environmental stress on corals. The physical roughness or rugosity of coral reefs is directly related to ecological diversity, reef health, and hydrodynamic roughness. However, the relationship between physical roughness and hydrodynamic roughness is not well understood despite the crucial role of bed friction in dissipating wave energy in coral reef aligned coasts. We examine the relationship between wave energy dissipation across a fringing reef in relation to the cross-reef ecological zonation and the benthic hydrodynamic roughness. Waves were measured by pressure transducers in a cross-reef transect on the reefs flats and post processed on a wave by wave basis to determine wave statistics such as significant wave height and wave period. Results from direct wave measurement were then used to calibrate a 1D wave dissipation model that incorporates dissipation functions due to bed friction and wave breaking. This model was used to assess the bed roughness required to produce the observed wave height dissipation during propagation from deep water and across the coral reef flats. Changes in wave dissipation was also examined under future scenarios of sea level rise and reduced bed roughness. Three dimensional models of the benthic reef structure were produced through structure-from-motion photogrammetry surveys. Reef rugosity was then determined from these surveys and related to the roughness results from the calibrated model. The results indicate that applying varying roughness coefficients as the benthic ecological assemblage changes produces the most accurate assessment of wave energy dissipation across the reef flat. However, the modelled results of bed roughness (e.g. 0.01 for the fore-reef slope) were different to the directly measured rugosity values (0.05 for the fore-reef slope) from three dimension structure-from-motion surveys. In spite of this, the modelled and directly measured values of roughness are similar considering the difficulties outlined in previous research when relating the coral reef structural complexity to a single value of hydrodynamic roughness. Bed roughness was shown to be a secondary factor behind wave breaking in dissipating wave energy. However, without bed friction waves could be an order of magnitude higher in the back-reef environment. Bed friction is also increasingly important in wave dissipation at higher sea levels as wave energy dissipation due to wave breaking is reduced at greater depths. This shows that maintaining a structurally diverse and healthy reef is crucial under future sea level rise scenarios in order to maintain the protection of coastal environments. These results also indicate that significant geomorphic change in coastal environments will occur due to reduced wave dissipation at higher sea levels unless reefs are capable of keeping up with forecasted sea level rise.
Resonant electrodynamic heating of stellar coronal loops: An LRC circuit analogue
NASA Technical Reports Server (NTRS)
Ionson, J. A.
1980-01-01
The electrodynamic coupling of stellar coronal loops to underlying beta velocity fields. A rigorous analysis revealed that the physics can be represented by a simple yet equivalent LRC circuit analogue. This analogue points to the existence of global structure oscillations which resonantly excite internal field line oscillations at a spatial resonance within the coronal loop. Although the width of this spatial resonance, as well as the induced currents and coronal velocity field, explicitly depend upon viscosity and resistivity, the resonant form of the generalized electrodynamic heating function is virtually independent of irreversibilities. This is a classic feature of high quality resonators that are externally driven by a broad band source of spectral power. Applications to solar coronal loops result in remarkable agreement with observations.
Analysis of ultraviolet and X-ray observations of three homologous solar flares from SMM
NASA Technical Reports Server (NTRS)
Cheng, Chung-Chieh; Pallavicini, Roberto
1987-01-01
Three homologous flares observed in the UV lines of Fe XXI and O V and in X-rays from the SMM were studied. It was found that: (1) the homology of the flares was most noticeable in Fe XXI and soft X-ray emissions; (2) the three flares shared many of the same loop footprints which were located in O V bright kernals associated with hard X-ray bursts; and (3) in spite of the strong spatial homology, the temporal evolution in UV and X-ray emissions varied from flare to flare. A comparison between the UV observations and photospheric magnetograms revealed that the basic flare configuration was a complex loop system consisting of many loops or bundles of loops.
NASA Astrophysics Data System (ADS)
Cheng, X. Y.; Wang, H. B.; Jia, Y. L.; Dong, YH
2018-05-01
In this paper, an open-closed-loop iterative learning control (ILC) algorithm is constructed for a class of nonlinear systems subjecting to random data dropouts. The ILC algorithm is implemented by a networked control system (NCS), where only the off-line data is transmitted by network while the real-time data is delivered in the point-to-point way. Thus, there are two controllers rather than one in the control system, which makes better use of the saved and current information and thereby improves the performance achieved by open-loop control alone. During the transfer of off-line data between the nonlinear plant and the remote controller data dropout occurs randomly and the data dropout rate is modeled as a binary Bernoulli random variable. Both measurement and control data dropouts are taken into consideration simultaneously. The convergence criterion is derived based on rigorous analysis. Finally, the simulation results verify the effectiveness of the proposed method.
Modal analysis of dislocation vibration and reaction attempt frequency
Sobie, Cameron; Capolungo, Laurent; McDowell, David L.; ...
2017-02-04
Transition state theory is a fundamental approach for temporal coarse-graining. It estimates the reaction rate for a transition processes by quantifying the activation free energy and attempt frequency for the unit process. To calculate the transition rate of a gliding dislocation, the attempt frequency is often obtained from line tension estimates of dislocation vibrations, a highly simplified model of dislocation behavior. This work revisits the calculation of attempt frequency for a dislocation bypassing an obstacle, in this case a self-interstitial atom (SIA) loop. First, a direct calculation of the vibrational characteristics of a finite pinned dislocation segment is compared tomore » line tension estimates before moving to the more complex case of dislocation-obstacle bypass. The entropic factor associated with the attempt frequency is calculated for a finite dislocation segment and for an infinite glide dislocation interacting with an SIA loop. Lastly, it is found to be dislocation length independent for three cases of dislocation-self interstitial atom (SIA) loop interactions.« less
THE EFFECTS OF LINE-OF-SIGHT INTEGRATION ON MULTISTRAND CORONAL LOOP OSCILLATIONS
DOE Office of Scientific and Technical Information (OSTI.GOV)
De Moortel, I.; Pascoe, D. J., E-mail: ineke@mcs.st-and.ac.uk
2012-02-10
Observations have shown that transverse oscillations are present in a multitude of coronal structures. It is generally assumed that these oscillations are driven by (sub)surface footpoint motions. Using fully three-dimensional MHD simulations, we show that these footpoint perturbations generate propagating kink (Alfvenic) modes which couple very efficiently into (azimuthal) Alfven waves. Using an ensemble of randomly distributed loops, driven by footpoint motions with random periods and directions, we compare the absolute energy in the numerical domain with the energy that is 'visible' when integrating along the line of sight (LOS). We show that the kinetic energy derived from the LOSmore » Doppler velocities is only a small fraction of the actual energy provided by the footpoint motions. Additionally, the superposition of loop structures along the LOS makes it nearly impossible to identify which structure the observed oscillations are actually associated with and could impact the identification of the mode of oscillation.« less
78 FR 66683 - Fisheries in the Western Pacific; Special Coral Reef Ecosystem Fishing Permit
Federal Register 2010, 2011, 2012, 2013, 2014
2013-11-06
... the Western Pacific; Special Coral Reef Ecosystem Fishing Permit AGENCY: National Marine Fisheries... special coral reef ecosystem fishing permit. SUMMARY: NMFS issued a Special Coral Reef Ecosystem Fishing Permit that authorizes Kampachi Farms, LLC, to culture and harvest a coral reef ecosystem management unit...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-14
... Collection; Comment Request; Coral Reef Conservation Program Administration AGENCY: National Oceanic and... The Coral Reef Conservation Act of 2000 (Act) was enacted to provide a framework for conserving coral reefs. The Coral Reef Conservation Grant Program, under the Act, provides funds to broad- based...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-07-01
..., NOAA is seeking information on the knowledge, attitudes and reef use patterns, as well as information on knowledge and attitudes related to specific reef protection activities. In addition, this survey... the efforts to protect reefs rely on education and changing attitudes toward reef protection, the...
ERIC Educational Resources Information Center
Walker, Sharon H.; Newton, R. Amanda; Ortiz, Alida
This activity book for middle school students on coral reefs is divided into 10 sections. Section 1 is the introduction. Section 2 describes what coral reefs are while section 3 describes how coral reefs reproduce and grow. Section 4 describes where coral reefs are found, and section 5 describes life on a coral reef. Section 6 describes the…
Great Barrier Reef, Queensland, Australia
NASA Technical Reports Server (NTRS)
1991-01-01
The Great Barrier Reef of Queensland, Australia extends for roughly 2,000 km along the northeast coast of Australia and is made up of thousands of individual reefs which define the edge of the Continental shelf. Swan Reef, the southern part of the reef system, is seen in this view. Water depths around the reefs are quite shallow (less than 1 to 36 meters) but only a few kilometers offshore, water depths can reach 1,000 meters.
Coral reefs in the Anthropocene.
Hughes, Terry P; Barnes, Michele L; Bellwood, David R; Cinner, Joshua E; Cumming, Graeme S; Jackson, Jeremy B C; Kleypas, Joanie; van de Leemput, Ingrid A; Lough, Janice M; Morrison, Tiffany H; Palumbi, Stephen R; van Nes, Egbert H; Scheffer, Marten
2017-05-31
Coral reefs support immense biodiversity and provide important ecosystem services to many millions of people. Yet reefs are degrading rapidly in response to numerous anthropogenic drivers. In the coming centuries, reefs will run the gauntlet of climate change, and rising temperatures will transform them into new configurations, unlike anything observed previously by humans. Returning reefs to past configurations is no longer an option. Instead, the global challenge is to steer reefs through the Anthropocene era in a way that maintains their biological functions. Successful navigation of this transition will require radical changes in the science, management and governance of coral reefs.
Menza, Charles; Kendall, M.; Rogers, C.; Miller, J.
2007-01-01
The well-documented degradation of shallower reefs which are often closer to land and more vulnerable to pollution, sewage and other human-related stressors has led to the suggestion that deeper, more remote offshore reefs could possibly serve as sources of coral and fish larvae to replenish the shallower reefs. Yet, the distribution, status, and ecological roles of deep (>30 m) Caribbean reefs are not well known. In this report, an observation of a deep reef which has undergone a recent extensive loss of coral cover is presented. In stark contrast to the typical pattern of coral loss in shallow reefs, the deeper corals were most affected. This report is the first description of such a pattern of coral loss on a deep reef.
The Ecological Role of Sharks on Coral Reefs.
Roff, George; Doropoulos, Christopher; Rogers, Alice; Bozec, Yves-Marie; Krueck, Nils C; Aurellado, Eleanor; Priest, Mark; Birrell, Chico; Mumby, Peter J
2016-05-01
Sharks are considered the apex predator of coral reefs, but the consequences of their global depletion are uncertain. Here we explore the ecological roles of sharks on coral reefs and, conversely, the importance of reefs for sharks. We find that most reef-associated shark species do not act as apex predators but instead function as mesopredators along with a diverse group of reef fish. While sharks perform important direct and indirect ecological roles, the evidence to support hypothesised shark-driven trophic cascades that benefit corals is weak and equivocal. Coral reefs provide some functional benefits to sharks, but sharks do not appear to favour healthier reef environments. Restoring populations of sharks is important and can yet deliver ecological surprise. Copyright © 2016 Elsevier Ltd. All rights reserved.
Checklist of fishes from madagascar reef, campeche bank, méxico.
Zarco Perello, Salvador; Moreno Mendoza, Rigoberto; Simões, Nuno
2014-01-01
This study presents the first list of fish species from Madagascar Reef, Campeche Bank, Gulf of México. Field surveys and literature review identified 54 species belonging to 8 orders, 30 families and 43 genera, comprising both conspicuous and cryptic fishes. Species richness was lower at this reef site compared to reefs in the Mexican Caribbean, Veracruz or Tuxpan, but was similar to other reefs in the same region. Species composition was a mixture of species present in all the reef systems of the Mexican Atlantic. Hypoplectrusecosur was recorded here for the first time in the Gulf of Mexico, Mycteropercamicrolepis, Equetuslanceolatus and Chaetodipterusfaber were new records for the reefs of the Campeche Bank, Elacatinusxanthiprora was recorded for the second time in Mexico and expanded its known distribution westwards from Alacranes Reef and Sanopusreticulatus, endemic of the Yucatan state, was recorded here for the first time on a reef.
Recent and relict topography of Boo Bee patch reef, Belize
Halley, R.B.; Shinn, E.A.; Hudson, J.H.; Lidz, B.; Taylor, D.L.
1977-01-01
Five core borings were taken on and around Boo Bee Patch Reef to better understand the origin of such shelf lagoon reefs. The cores reveal 4 stages of development: (1) subaerial exposure of a Pleistocene "high" having about 8 meters of relief, possibly a Pleistocene patch reef; (2) deposition of peat and impermeable terrigenous clay 3 meters thick around the high; (3) initiation of carbonate sediment production by corals and algae on the remaining 5 meters of hard Pleistocene topography and carbonate mud on the surrounding terrigenous clay; and (4) accelerated organic accumulation on the patch reef. Estimates of patch reef sedimentation rates (1.6 m/1000 years) are 3 to 4 times greater than off-reef sedimentation rates (0.4-0.5 m/1000 years). During periods of Pleistocene sedimentation on the Belize shelf, lagoon patch reefs may have grown above one another, stacking up to form reef accumulation of considerable thickness.
Tight coupling between coral reef morphology and mapped resilience in the Red Sea.
Rowlands, Gwilym; Purkis, Sam; Bruckner, Andrew
2016-04-30
Lack of knowledge on the conservation value of different reef types can stymie decision making, and result in less optimal management solutions. Addressing the information gap of coral reef resilience, we produce a map-based Remote Sensed Resilience Index (RSRI) from data describing the spatial distribution of stressors, and properties of reef habitats on the Farasan Banks, Saudi Arabia. We contrast the distribution of this index among fourteen reef types, categorized on a scale of maturity that includes juvenile (poorly aggraded), mature (partially aggraded), and senile (fully aggraded) reefs. Sites with high reef resilience can be found in most detached reef types; however they are most common in mature reefs. We aim to stimulate debate on the coupling that exists between geomorphology and conservation biology, and consider how such information can be used to inform management decisions. Copyright © 2015 Elsevier Ltd. All rights reserved.
The growth of coral reef science in the Gulf: a historical perspective.
Burt, John A
2013-07-30
Coral reef science has grown exponentially in recent decades in the Gulf. Analysis of literature from 1950 to 2012 identified 270 publications on coral reefs in the Gulf, half of which were published in just the past decade. This paper summarizes the growth and evolution of coral reef science in the Gulf by examining when, where and how research has been conducted on Gulf reefs, who conducted that research, and what themes and taxa have dominated scientific interest. The results demonstrate that there has been significant growth in our understanding of the valuable coral reefs of the Gulf, but also highlight the fact that we are documenting an increasingly degraded ecosystem. Reef scientists must make a concerted effort to improve dialogue with regional reef management and decision-makers if we are to stem the tide of decline in coral reefs in the Gulf. Copyright © 2013 Elsevier Ltd. All rights reserved.
Checklist of Fishes from Madagascar Reef, Campeche Bank, México
2014-01-01
Abstract This study presents the first list of fish species from Madagascar Reef, Campeche Bank, Gulf of México. Field surveys and literature review identified 54 species belonging to 8 orders, 30 families and 43 genera, comprising both conspicuous and cryptic fishes. Species richness was lower at this reef site compared to reefs in the Mexican Caribbean, Veracruz or Tuxpan, but was similar to other reefs in the same region. Species composition was a mixture of species present in all the reef systems of the Mexican Atlantic. Hypoplectrus ecosur was recorded here for the first time in the Gulf of Mexico, Mycteroperca microlepis, Equetus lanceolatus and Chaetodipterus faber were new records for the reefs of the Campeche Bank, Elacatinus xanthiprora was recorded for the second time in Mexico and expanded its known distribution westwards from Alacranes Reef and Sanopus reticulatus, endemic of the Yucatan state, was recorded here for the first time on a reef. PMID:24891834
Extinction rate, historical population structure and ecological role of the Caribbean monk seal.
McClenachan, Loren; Cooper, Andrew B
2008-06-22
The productivity and biomass of pristine coral reef ecosystems is poorly understood, particularly in the Caribbean where communities have been impacted by overfishing and multiple other stressors over centuries. Using historical data on the spatial distribution and abundance of the extinct Caribbean monk seal (Monachus tropicalis), this study reconstructs the population size, structure and ecological role of this once common predator within coral reef communities, and provides evidence that historical reefs supported biomasses of fishes and invertebrates up to six times greater than those found on typical modern Caribbean reefs. An estimated 233,000-338,000 monk seals were distributed among 13 colonies across the Caribbean. The biomass of reef fishes and invertebrates required to support historical seal populations was 732-1018 gm(-2) of reefs, which exceeds that found on any Caribbean reef today and is comparable with those measured in remote Pacific reefs. Quantitative estimates of historically dense monk seal colonies and their consumption rates on pristine reefs provide concrete data on the magnitude of decline in animal biomass on Caribbean coral reefs. Realistic reconstruction of these past ecosystems is critical to understanding the profound and long-lasting effect of human hunting on the functioning of coral reef ecosystems.
NASA Astrophysics Data System (ADS)
Noernberg, Mauricio Almeida; Fournier, Jérôme; Dubois, Stanislas; Populus, Jacques
2010-12-01
This study has exploited aerial photographs and LiDAR digital elevation model to quantify intertidal complex landforms volume. A first volume estimation of the main sabellariid polychaete reef complex of the Bay of Mont-Saint-Michel - France is presented. The Sabellaria alveolata is an engineering species that heavily modifies its environment. This gregarious tube-building annelid forms dense and solid reefs of bioclastic coarse sand which can reach several km 2. Since 1970 a very strong decline of reefs has been observed. The authorities have curbed fishing activities without any noticeable changes in reef health status. The S. alveolata reef volume is estimated to be 132 048 m 3 (96 301 m 3 for Sainte-Anne reef and 35 747 m 3 for Champeaux reef). Further LiDAR data surveys will be needed to be able to understand and quantify the accretion/erosion processes in play in the reef dynamic. Because of the internal variability of topographic complexity of the reef, characterized by crevices, cracks, and holes rather than whole blocks, further studies are needed to calculate more accurately the volume of the reef.
The Coral Reef pH-stat: An Important Defense Against Ocean Acidification? (Invited)
NASA Astrophysics Data System (ADS)
Andersson, A. J.; Yeakel, K.; Bates, N.; de Putron, S.; Collins, A.
2013-12-01
Concerns have been raised on how coral reefs will be affected by ocean acidification (OA), but there are currently no direct predictions on how seawater CO2 chemistry and pH within coral reefs might change in response to OA. Projections of future changes in seawater pH and aragonite saturation state have only been applied to open ocean conditions surrounding coral reef environments rather than the reef systems themselves. The seawater CO2 chemistry within heterogenous coral reef systems can be significantly different from that of the open ocean depending on the residence time, community composition and the major biogeochemical processes occurring on the reef, i.e., net ecosystem organic carbon production and calcification, which combined act to modify the seawater chemistry. We argue that these processes and coral reefs in general could as a pH-stat, partly regulating seawater pH on the reef and offsetting changes in seawater chemistry imposed by ocean acidification. Based on observations from the Bermuda coral reef, we show that a range of anticipated biogeochemical responses of coral reef communities to OA by the end of this century could partially offset changes in seawater pH by an average of 12% to 24%.
Linking social and ecological systems to sustain coral reef fisheries.
Cinner, Joshua E; McClanahan, Timothy R; Daw, Tim M; Graham, Nicholas A J; Maina, Joseph; Wilson, Shaun K; Hughes, Terence P
2009-02-10
The ecosystem goods and services provided by coral reefs are critical to the social and economic welfare of hundreds of millions of people, overwhelmingly in developing countries [1]. Widespread reef degradation is severely eroding these goods and services, but the socioeconomic factors shaping the ways that societies use coral reefs are poorly understood [2]. We examine relationships between human population density, a multidimensional index of socioeconomic development, reef complexity, and the condition of coral reef fish populations in five countries across the Indian Ocean. In fished sites, fish biomass was negatively related to human population density, but it was best explained by reef complexity and a U-shaped relationship with socioeconomic development. The biomass of reef fishes was four times lower at locations with intermediate levels of economic development than at locations with both low and high development. In contrast, average biomass inside fishery closures was three times higher than in fished sites and was not associated with socioeconomic development. Sustaining coral reef fisheries requires an integrated approach that uses tools such as protected areas to quickly build reef resources while also building capacities and capital in societies over longer time frames to address the complex underlying causes of reef degradation.
2016-01-01
Reef restoration activities have proliferated in response to the need to mitigate coral declines and recover lost reef structure, function, and ecosystem services. Here, we describe the recent shift from costly and complex engineering solutions to recover degraded reef structure to more economical and efficient ecological approaches that focus on recovering the living components of reef communities. We review the adoption and expansion of the coral gardening framework in the Caribbean and Western Atlantic where practitioners now grow and outplant 10,000’s of corals onto degraded reefs each year. We detail the steps for establishing a gardening program as well as long-term goals and direct and indirect benefits of this approach in our region. With a strong scientific basis, coral gardening activities now contribute significantly to reef and species recovery, provide important scientific, education, and outreach opportunities, and offer alternate livelihoods to local stakeholders. While challenges still remain, the transition from engineering to ecological solutions for reef degradation has opened the field of coral reef restoration to a wider audience poised to contribute to reef conservation and recovery in regions where coral losses and recruitment bottlenecks hinder natural recovery. PMID:27781176
Lirman, Diego; Schopmeyer, Stephanie
2016-01-01
Reef restoration activities have proliferated in response to the need to mitigate coral declines and recover lost reef structure, function, and ecosystem services. Here, we describe the recent shift from costly and complex engineering solutions to recover degraded reef structure to more economical and efficient ecological approaches that focus on recovering the living components of reef communities. We review the adoption and expansion of the coral gardening framework in the Caribbean and Western Atlantic where practitioners now grow and outplant 10,000's of corals onto degraded reefs each year. We detail the steps for establishing a gardening program as well as long-term goals and direct and indirect benefits of this approach in our region. With a strong scientific basis, coral gardening activities now contribute significantly to reef and species recovery, provide important scientific, education, and outreach opportunities, and offer alternate livelihoods to local stakeholders. While challenges still remain, the transition from engineering to ecological solutions for reef degradation has opened the field of coral reef restoration to a wider audience poised to contribute to reef conservation and recovery in regions where coral losses and recruitment bottlenecks hinder natural recovery.
The Role of Turtles as Coral Reef Macroherbivores
Goatley, Christopher H. R.; Hoey, Andrew S.; Bellwood, David R.
2012-01-01
Herbivory is widely accepted as a vital function on coral reefs. To date, the majority of studies examining herbivory in coral reef environments have focused on the roles of fishes and/or urchins, with relatively few studies considering the potential role of macroherbivores in reef processes. Here, we introduce evidence that highlights the potential role of marine turtles as herbivores on coral reefs. While conducting experimental habitat manipulations to assess the roles of herbivorous reef fishes we observed green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) showing responses that were remarkably similar to those of herbivorous fishes. Reducing the sediment load of the epilithic algal matrix on a coral reef resulted in a forty-fold increase in grazing by green turtles. Hawksbill turtles were also observed to browse transplanted thalli of the macroalga Sargassum swartzii in a coral reef environment. These responses not only show strong parallels to herbivorous reef fishes, but also highlight that marine turtles actively, and intentionally, remove algae from coral reefs. When considering the size and potential historical abundance of marine turtles we suggest that these potentially valuable herbivores may have been lost from many coral reefs before their true importance was understood. PMID:22768189
The role of turtles as coral reef macroherbivores.
Goatley, Christopher H R; Hoey, Andrew S; Bellwood, David R
2012-01-01
Herbivory is widely accepted as a vital function on coral reefs. To date, the majority of studies examining herbivory in coral reef environments have focused on the roles of fishes and/or urchins, with relatively few studies considering the potential role of macroherbivores in reef processes. Here, we introduce evidence that highlights the potential role of marine turtles as herbivores on coral reefs. While conducting experimental habitat manipulations to assess the roles of herbivorous reef fishes we observed green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) showing responses that were remarkably similar to those of herbivorous fishes. Reducing the sediment load of the epilithic algal matrix on a coral reef resulted in a forty-fold increase in grazing by green turtles. Hawksbill turtles were also observed to browse transplanted thalli of the macroalga Sargassum swartzii in a coral reef environment. These responses not only show strong parallels to herbivorous reef fishes, but also highlight that marine turtles actively, and intentionally, remove algae from coral reefs. When considering the size and potential historical abundance of marine turtles we suggest that these potentially valuable herbivores may have been lost from many coral reefs before their true importance was understood.
Lidz, Barbara H.; Hine, A.C.; Shinn, Eugene A.; Kindinger, Jack G.
1991-01-01
High-resolution seismic-reflection profiles off the lower Florida Keys reveal a multiple outlier-reef tract system ~0.5 to 1.5 km sea-ward of the bank margin. The system is characterized by a massive, outer main reef tract of high (28 m) unburied relief that parallels the margin and at least two narrower, discontinuous reef tracts of lower relief between the main tract and the shallow bank-margin reefs. The outer tract is ~0.5 to 1 km wide and extends a distance of ~57 km. A single pass divides the outer tract into two main reefs. The outlier reefs developed on antecedent, low-gradient to horizontal offbank surfaces, interpreted to be Pleistocene beaches that formed terracelike features. Radiocarbon dates of a coral core from the outer tract confirm a pre-Holocene age. These multiple outlier reefs represent a new windward-margin model that presents a significant, unique mechanism for progradation of carbonate platforms during periods of sea-level fluctuation. Infilling of the back-reef terrace basins would create new terraced promontories and would extend or "step" the platform seaward for hundreds of metres. Subsequent outlier-reef development would produce laterally accumulating sequences.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lighty, R.G.; Russell, K.L.
Transect mapping and petrologic studies reveal a new depositional model and limited diagenesis of a well-exposed Pleistocene reef outcrop at Ambergris Cay, northern Belize. This emergent shelf-edge reef forms a rocky wave-washed headland at the northern terminus of the present-day 250 km long flourishing Belize Barrier Reef. Previously, the Belize reef outcrop was thought to extend southward in the subsurface beneath the modern barrier reef as a Pleistocene equivalent. The authors study indicate that this outcrop is a large, coral patch reef and not part of a barrier reef trend. Sixteen transects 12.5 m apart described in continuous cm incrementsmore » from fore reef to back reef identified: extensive deposits of broken Acropora cervicornis; small thickets of A. palmata with small, oriented branches; and muddy skeletal sediments with few corals or reef rubble. Thin section and SEM studies show three phases of early submarine cementation: syntaxial and rosette aragonite; Mg-calcite rim cement and peloids; and colloidal Mg-calcite geopetal fill. Subaerial exposure in semi-arid northern Belize caused only minor skeletal dissolution, some precipitation of vadose whisker calcite, and no meteoric phreatic diagenesis. Facies geometry, coral assemblages, lack of rubble deposits, coralline algal encrustations and Millepora framework, and recognition of common but discrete submarine cements, all indicate that this Pleistocene reef was an isolated, coral-fringed sediment buildup similar to may large patch reefs existing today in moderate-energy shelf environments behind the modern barrier reef in central and southern Belize.« less
Framework of barrier reefs threatened by ocean acidification.
Comeau, Steeve; Lantz, Coulson A; Edmunds, Peter J; Carpenter, Robert C
2016-03-01
To date, studies of ocean acidification (OA) on coral reefs have focused on organisms rather than communities, and the few community effects that have been addressed have focused on shallow back reef habitats. The effects of OA on outer barrier reefs, which are the most striking of coral reef habitats and are functionally and physically different from back reefs, are unknown. Using 5-m long outdoor flumes to create treatment conditions, we constructed coral reef communities comprised of calcified algae, corals, and reef pavement that were assembled to match the community structure at 17 m depth on the outer barrier reef of Moorea, French Polynesia. Communities were maintained under ambient and 1200 μatm pCO2 for 7 weeks, and net calcification rates were measured at different flow speeds. Community net calcification was significantly affected by OA, especially at night when net calcification was depressed ~78% compared to ambient pCO2 . Flow speed (2-14 cm s(-1) ) enhanced net calcification only at night under elevated pCO2 . Reef pavement also was affected by OA, with dissolution ~86% higher under elevated pCO2 compared to ambient pCO2 . These results suggest that net accretion of outer barrier reef communities will decline under OA conditions predicted within the next 100 years, largely because of increased dissolution of reef pavement. Such extensive dissolution poses a threat to the carbonate foundation of barrier reef communities. © 2015 John Wiley & Sons Ltd.
Predicting climate-driven regime shifts versus rebound potential in coral reefs.
Graham, Nicholas A J; Jennings, Simon; MacNeil, M Aaron; Mouillot, David; Wilson, Shaun K
2015-02-05
Climate-induced coral bleaching is among the greatest current threats to coral reefs, causing widespread loss of live coral cover. Conditions under which reefs bounce back from bleaching events or shift from coral to algal dominance are unknown, making it difficult to predict and plan for differing reef responses under climate change. Here we document and predict long-term reef responses to a major climate-induced coral bleaching event that caused unprecedented region-wide mortality of Indo-Pacific corals. Following loss of >90% live coral cover, 12 of 21 reefs recovered towards pre-disturbance live coral states, while nine reefs underwent regime shifts to fleshy macroalgae. Functional diversity of associated reef fish communities shifted substantially following bleaching, returning towards pre-disturbance structure on recovering reefs, while becoming progressively altered on regime shifting reefs. We identified threshold values for a range of factors that accurately predicted ecosystem response to the bleaching event. Recovery was favoured when reefs were structurally complex and in deeper water, when density of juvenile corals and herbivorous fishes was relatively high and when nutrient loads were low. Whether reefs were inside no-take marine reserves had no bearing on ecosystem trajectory. Although conditions governing regime shift or recovery dynamics were diverse, pre-disturbance quantification of simple factors such as structural complexity and water depth accurately predicted ecosystem trajectories. These findings foreshadow the likely divergent but predictable outcomes for reef ecosystems in response to climate change, thus guiding improved management and adaptation.
Porosity evolution of upper Miocene reefs, Almeria Province, southern Spain
Armstrong, A.K.; Snavely, P.D.; Addicott, W.O.
1980-01-01
Sea cliffs 40 km east of Almeria, southeastern Spain, expose upper Miocene reefs and patch reefs of the Plomo formation. These reefs are formed of scleractinian corals, calcareous algae, and mollusks. The reef cores are as much as 65 m thick and several hundred meters wide. Fore-reef talus beds extend 1,300 m across and are 40 m thick. The reefs and reef breccias are composed of calcific dolomite. They lie on volcanic rocks that have a K-Ar date of 11.5 m.y. and in turn are overlain by the upper Miocene Vicar Formation. In the reef cores and fore-reef breccia beds, porosity is both primary and postdepositional. Primary porosity is of three types: (a) boring clam holes in the scleractinian coral heads, cemented reef rocks, and breccias; (b) intraparticle porosity within the corals, Halimeda plates, and vermetid worm tubes; and (c) interparticle porosity between bioclastic fragments and in the reef breccia. Postdepositional moldic porosity was formed by the solution of aragonitic material such as molluscan and coral fragments. The Plomo reef carbonate rocks have high porosity and permeability, and retain a great amount of depositional porosity. Pores range in size from a few micrometers to 30 cm. The extensive intercrystalline porosity and high permeability resulted from dolomitization of micritic matrix. Dolomite rhombs are between 10 and 30 μ across. More moldic porosity was formed by the dissolution of the calclte bioclasts. Some porosity reduction has occurred by incomplete and partial sparry calcite infilling of interparticular, moldic, and intercrystalline voids. The high porosity and permeability of these reefs make them important targets for petroleum exploration in the western Mediterranean off southern Spain. In these offshore areas in the subsurface the volcanic ridge and the Plomo reef complex are locally onlapped or overlapped by 350 m or more of Miocene(?) and Pliocene fine-grained sedimentary rocks. The possibility exists that the buried Plomo reef deposits may form traps for oil and gas in the offshore areas southwest of the type locality. Stratigraphic traps also may occur where the Neogene sequence above the Plomo reef complex onlaps the volcanic ridge.
Mead, Emma J; Masterton, Rosalyn J; Feary, Marc; Obrezanova, Olga; Zhang, Lin; Young, Robert; Smales, C Mark
2015-12-15
Translation initiation is on the critical pathway for the production of monoclonal antibodies (mAbs) by mammalian cells. Formation of a closed loop structure comprised of mRNA, a number of eukaryotic initiation factors (eIFs) and ribosomal proteins has been proposed to aid re-initiation of translation and therefore increase global translational efficiency. We have determined mRNA and protein levels of the key components of the closed loop, eIFs (eIF3a, eIF3b, eIF3c, eIF3h, eIF3i and eIF4G1), poly(A)-binding protein (PABP) 1 and PABP-interacting protein 1 (PAIP1), across a panel of 30 recombinant mAb-producing GS-CHOK1SV cell lines with a broad range of growth characteristics and production levels of a model recombinant mAb. We have used a multi-level statistical approach to investigate the relationship between key performance indicators (cell growth and recombinant antibody productivity) and the intracellular amounts of target translation initiation factor proteins and the mRNAs encoding them. We show that high-producing cell lines maintain amounts of the translation initiation factors involved in the formation of the closed loop mRNA, maintaining these proteins at appropriate levels to deliver enhanced recombinant protein production. We then utilize knowledge of the amounts of these factors to build predictive models for and use cluster analysis to identify, high-producing cell lines. The present study therefore defines the translation initiation factor amounts that are associated with highly productive recombinant GS-CHOK1SV cell lines that may be targets for screening highly productive cell lines or to engineer new host cell lines with the potential for enhanced recombinant antibody productivity. © 2015 Authors; published by Portland Press Limited.
Duodenal Loop Obstruction as an Unusual Cause of Acute Pancreatitis: A Case Series.
Lee, Hyeonmin; Choi, Yonghyeok; Jeong, Hyewon; Lim, Jae Kyu; Jung, Taeyoung; Han, Joung Ho; Park, Seon Mee
2016-12-25
Duodenal loop obstruction is an unusual cause of acute pancreatitis. Increased intraluminal pressure hinders pancreatic flow, causing dilatation of the pancreatic duct and inducing acute pancreatitis. We experienced three cases of acute pancreatitis that resulted from duodenal loop obstruction after (1) an esophagectomy with gastric pull-up procedure for esophageal cancer, (2) a gastrectomy with Billroth I reconstruction for gastric cancer, and (3) a gastrojejunostomy for abdominal trauma. An abdominal CT scan revealed a distended duodenal loop, dilated pancreatic duct, and inflamed pancreas with fluid collection. Acute pancreatitis with duodenal loop obstruction was diagnosed by abdominal pain, elevated serum amylase/lipase, and abdominal CT findings. Immediate decompression with a nasogastric tube was performed, and all patients showed improvement within one week after admission. Each patient was followed up for more than two years without recurrence. Our findings suggest the usefulness of nasogastric tube decompression as the first line of treatment for acute pancreatitis related to duodenal loop obstruction.
Barrier tunneling of the loop-nodal semimetal in the hyperhoneycomb lattice
NASA Astrophysics Data System (ADS)
Guan, Ji-Huan; Zhang, Yan-Yang; Lu, Wei-Er; Xia, Yang; Li, Shu-Shen
2018-05-01
We theoretically investigate the barrier tunneling in the 3D model of the hyperhoneycomb lattice, which is a nodal-line semimetal with a Dirac loop at zero energy. In the presence of a rectangular potential, the scattering amplitudes for different injecting states around the nodal loop are calculated, by using analytical treatments of the effective model, as well as numerical simulations of the tight binding model. In the low energy regime, states with remarkable transmissions are only concentrated in a small range around the loop plane. When the momentum of the injecting electron is coplanar with the nodal loop, nearly perfect transmissions can occur for a large range of injecting azimuthal angles if the potential is not high. For higher potential energies, the transmission shows a resonant oscillation with the potential, but still with peaks being perfect transmissions that do not decay with the potential width. These strikingly robust transports of the loop-nodal semimetal can be approximately explained by a momentum dependent Dirac Hamiltonian.
Effect of Loop Geometry on TEM Response Over Layered Earth
NASA Astrophysics Data System (ADS)
Qi, Youzheng; Huang, Ling; Wu, Xin; Fang, Guangyou; Yu, Gang
2014-09-01
A large horizontal loop located on the ground or carried by an aircraft are the most common sources of the transient electromagnetic method. Although topographical factors or airplane outlines make the loop of arbitrary shape, magnetic sources are generally represented as a magnetic dipole or a circular loop, which may bring about significant errors in the calculated response. In this paper, we present a method for calculating the response of a loop of arbitrary shape (for which the description can be obtained by different methods, including GPS localization) in air or on the surface of a stratified earth. The principle of reciprocity is firstly used to exchange the functions of the transmitting loop and the dipole receiver, then the response of a vertical or a horizontal magnetic dipole is calculated beforehand, and finally the line integral of the second kind is employed to get the transient response. Analytical analysis and comparisons depict that our work got very good results in many situations. Synthetic and field examples are given in the end to show the effect of loop geometry and how our method improves the precision of the EM response.
Phase-locked-loop-based delay-line-free picosecond electro-optic sampling system
NASA Astrophysics Data System (ADS)
Lin, Gong-Ru; Chang, Yung-Cheng
2003-04-01
A delay-line-free, high-speed electro-optic sampling (EOS) system is proposed by employing a delay-time-controlled ultrafast laser diode as the optical probe. Versatile optoelectronic delay-time controllers (ODTCs) based on modified voltage-controlled phase-locked-loop phase-shifting technologies are designed for the laser. The integration of the ODTC circuit and the pulsed laser diode has replaced the traditional optomechanical delay-line module used in the conventional EOS system. This design essentially prevents sampling distortion from misalignment of the probe beam, and overcomes the difficulty in sampling free-running high-speed transients. The maximum tuning range, error, scanning speed, tuning responsivity, and resolution of the ODTC are 3.9π (700°), <5% deviation, 25-2405 ns/s, 0.557 ps/mV, and ˜1 ps, respectively. Free-running wave forms from the analog, digital, and pulsed microwave signals are sampled and compared with those measured by the commercial apparatus.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kramer, Sharon H.; Hamilton, Christine D.; Spencer, Gregory C.
Wave energy converters (WECs) and tidal energy converters (TECs) are only beginning to be deployed along the U.S. West Coast and in Hawai‘i, and a better understanding of their ecological effects on fish, particularly on special-status fish (e.g., threatened and endangered) is needed to facilitate project design and environmental permitting. The structures of WECs and TECs placed on to the seabed, such as anchors and foundations, may function as artificial reefs that attract reef-associated fishes, while the midwater and surface structures, such as mooring lines, buoys, and wave or tidal power devices, may function as fish aggregating devices (FADs), formingmore » the nuclei for groups of fishes. Little is known about the potential for WECs and TECs to function as artificial reefs and FADs in coastal waters of the U.S. West Coast and Hawai‘i. We evaluated these potential ecological interactions by reviewing relevant information about fish associations with surrogate structures, such as artificial reefs, natural reefs, kelps, floating debris, oil and gas platforms, marine debris, anchored FADs deployed to enhance fishing opportunities, net-cages used for mariculture, and piers and docks. Based on our review, we postulate that the structures of WECs and TECs placed on or near the seabed in coastal waters of the U.S. West Coast and Hawai‘i likely will function as small-scale artificial reefs and attract potentially high densities of reef-associated fishes (including special-status rockfish species [Sebastes spp.] along the mainland), and that the midwater and surface structures of WECs placed in the tropical waters of Hawai‘i likely will function as de facto FADs with species assemblages varying by distance from shore and deployment depth. Along the U.S. West Coast, frequent associations with midwater and surface structures may be less likely: juvenile, semipelagic, kelp-associated rockfishes may occur at midwater and surface structures of WECs in coastal waters of southern California to Washington, and occasional, seasonal, or transitory associations of coastal pelagic fishes such as jack mackerel (Trachurus symmetricus) may also occur at WECs in these waters. Importantly, our review indicated that negative effects of WEC structures on special-status fish species, such as increased predation of juvenile salmonids or rockfishes, are not likely. In addition, WECs installed in coastal California, especially in southern California waters, have the potential to attract high densities of reef-associated fishes and may even contribute to rockfish productivity, if fish respond to the WECs similarly to oil and gas platforms, which have some of the highest secondary production per unit area of seafloor of any marine habitat studied globally (Claisse et al. 2014). We encountered some information gaps, owing to the paucity or lack, in key locations, of comparable surrogate structures in which fish assemblages and ecological interactions were studied. TECs are most likely to be used in the Puget Sound area, but suitable surrogates are lacking there. However, in similarly cold-temperate waters of Europe and Maine, benthopelagic fish occurred around tidal turbines during lower tidal velocities, and this type of interaction may be expected by similar species at TECs in Puget Sound. To address information gaps in the near term, such as whether WECs would function as FADs in temperate waters, studies of navigation buoys using hydroacoustics are recommended.« less
Opto-electronic oscillator: moving toward solutions based on polymer materials
NASA Astrophysics Data System (ADS)
Nguyên, Lâm Duy; Journet, Bernard; Zyss, Joseph
2008-02-01
Optoelectronic oscillators have been studied since many years now, their high spectral purity being one of their most interesting quality for photonics signal processing, communication or radio over fiber systems. One part of the structure is a long fiber optic feedback loop acting as a delay line. Different techniques have been introduced such as multiple loops in order to get very narrow spectral lines and large mode spacing. One of the problems due to long fiber loops is the size and the requirement of temperature control. In order to go toward integrated solutions it is also possible to introduce optical resonators instead of a delay line structure (as for classical electronic oscillators). But such resonators should present very high quality factor. In this paper we demonstrate solutions using resonators based on polymer materials such as PMMA-DCM. Structures such as micro-rings, micro-disks or stadium-shaped resonator have been realized at the laboratory. Quality factor of 6000 have already been achieved leading to an equivalent fiber loop of 19 m for an oscillator at 10 GHz. But it has been already theoretically proved that quality factor greater than one thousand hundred could be obtained. These resonators can be directly implemented with Mach-Zehnder optical modulators based on electro-optic polymer such as PMMA-DR1 leading to integrated solutions. And in the future it should be also possible to add a laser made with polymer material, with a structure as stadium-shape polymer micro-laser. The fully integrated photonic chip is not so far. The last important function to be implemented is the tuning of the oscillation frequency.
Ros, Albert F H; Vullioud, Philippe; Bshary, Redouan
2012-01-01
Cooperation often involves a conflict of interest. This is particularly true in situations where one individual seeks out a service but cannot properly control the quality of the service given by the partner who would gain from defecting. An example is cleaning mutualism involving the bluestreak cleaner wrasse (Labroides dimidiatus) and its reef-fish 'clients'. These cleaners may reduce the stress experienced by their clients by removing parasites; however they occasionally cheat clients (i.e. defect) by eating mucus and other living tissues. Here we present experimental support for the hypothesis that stress responses increase the motivation for clients to seek out such risky asymmetric interactions. We manipulated the stress response by blocking glucocorticoid receptors with the antagonist RU486 in a species that is a regular visitor of cleaner fish, the lined bristletooth (Ctenochaetus striatus). Field observations 1 week after treatment with RU486 showed that antagonist treatment led to a reduction in cleaning duration compared to control treatment. This was not explained by a general effect on client behavior as intraspecific social behavior appeared unaffected. We propose that antagonist treatment reduced stress responses to the presence of ectoparasites, which in turn reduced the client's perception of benefits from seeking out cleaning interactions. The results demonstrate a hitherto overlooked variable role of stress and stress responses on cooperative behavior. Copyright © 2011 Elsevier Inc. All rights reserved.
NASA Astrophysics Data System (ADS)
Hongo, Chuki
2012-03-01
The geological record of key coral species that contribute to reef formation and maintenance of reef ecosystems is important for understanding the ecosystem response to global-scale climate change and anthropogenic stresses in the near future. Future responses can be predicted from accumulated data on Holocene reef species identified in drillcore and from data on raised reef terraces. The present study analyzes a dataset based on 27 drillcores, raised reef terraces, and 134 radiocarbon and U-Th ages from reefs of the Northwest Pacific, with the aim of examining the role of key coral species in reef growth and maintenance for reef ecosystem during Holocene sea-level change. The results indicate a latitudinal change in key coral species: arborescent Acropora (Acropora intermedia and Acropora muricata) was the dominant reef builder at reef crests in the tropics, whereas Porites (Porites australiensis, Porites lutea, and Porites lobata) was the dominant contributor to reef growth in the subtropics between 10,000 and 7000 cal. years BP (when the rate of sea-level rise was 10 m/ka). Acropora digitifera, Acropora hyacinthus, Acropora robusta/A. abrotanoides, Isopora palifera, Favia stelligera, and Goniastrea retiformis from the corymbose and tabular Acropora facies were the main key coral species at reef crests between 7000 and 5000 cal. years BP (when the rate of sea-level rise was 5 m/ka) and during the following period of stable sea-level. Massive Porites (P. australiensis, P. lutea, and P. lobata) contributed to reef growth in shallow lagoons during the period of stable sea level. Key coral species from the corymbose and tabular Acropora facies have the potential to build reefs and maintain ecosystems in the near future under a global sea-level rise of 2-6 m/ka, as do key coral species from the arborescent Acropora facies and massive Porites facies, which show vigorous growth and are tolerant to relatively deep-water, low-energy environments. However, these species are likely to experience severe mortality in upcoming decades due to natural and anthropogenic stresses. Consequently, this damage will lead to a collapse in reef formation and the maintenance of reef ecosystems in the near future. This study emphasizes the need for research into the conservation of key coral species.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Miyazaki, Tadakuni; Harashima, Akira; Nakatani, Yukihiro
Coral reefs are the major sites for photo-synthesis and calcification in the present ocean. Estimating the production rate of calcification by the coral reefs or investigating the sink/source mechanism of CO{sub 2} by the coral reefs in the ocean, the distribution of the coral reefs in the world wide must be identified. Measuring the spectral signatures of underwater coral reefs and mapping of coral reefs by satellite remote sensing are described. The spectral signatures of different species of the coral reefs were measured using a spectroradiometer at off Kuroshima Island, Okinawa, Japan and investigated spectral difference between different species ofmore » the coral reefs. As well as the field experiments, laboratory experiments for measuring the spectral signatures of 9 different species of coral reefs were carried out with the same spectroradiometer. The spectral reflectance of each coral reef showed a significant result that a narrow absorption band exists in the spectral region between 660 and 680 nm, and very strong spectral reflectance from about 700 nm towards the longer wavelength range. On the other hand, absorption and the high reflectance region were not observed from the bottom sands or bare rocks underwater. These experiments suggested that there is a significant spectral difference between coral reefs and bottom sands or bare rocks and so the best spectral range for separating the coral reefs from other underwater objects in the ocean would be between 700 and 800 nm. As well as the basic spectral measurement either in the field or at the laboratory, SPOT satellite imageries were used to classify the underwater coral reefs. Classification methods used here were the principal component analysis, and the maximum likelihood. Finally, the evaluation of classification method for extracting the coral reefs was introduced.« less
Bond, Mark E.; Babcock, Elizabeth A.; Pikitch, Ellen K.; Abercrombie, Debra L.; Lamb, Norlan F.; Chapman, Demian D.
2012-01-01
Carcharhinid sharks can make up a large fraction of the top predators inhabiting tropical marine ecosystems and have declined in many regions due to intense fishing pressure. There is some support for the hypothesis that carcharhinid species that complete their life-cycle within coral reef ecosystems, hereafter referred to as “reef sharks”, are more abundant inside no-take marine reserves due to a reduction in fishing pressure (i.e., they benefit from marine reserves). Key predictions of this hypothesis are that (a) individual reef sharks exhibit high site-fidelity to these protected areas and (b) their relative abundance will generally be higher in these areas compared to fished reefs. To test this hypothesis for the first time in Caribbean coral reef ecosystems we combined acoustic monitoring and baited remote underwater video (BRUV) surveys to measure reef shark site-fidelity and relative abundance, respectively. We focused on the Caribbean reef shark (Carcharhinus perezi), the most common reef shark in the Western Atlantic, at Glover's Reef Marine Reserve (GRMR), Belize. Acoustically tagged sharks (N = 34) were detected throughout the year at this location and exhibited strong site-fidelity. Shark presence or absence on 200 BRUVs deployed at GRMR and three other sites (another reserve site and two fished reefs) showed that the factor “marine reserve” had a significant positive effect on reef shark presence. We rejected environmental factors or site-environment interactions as predominant drivers of this pattern. These results are consistent with the hypothesis that marine reserves can benefit reef shark populations and we suggest new hypotheses to determine the underlying mechanism(s) involved: reduced fishing mortality or enhanced prey availability. PMID:22412965
Coral Reef Color: Remote and In-Situ Imaging Spectroscopy of Reef Structure and Function
NASA Astrophysics Data System (ADS)
Hochberg, E. J.
2016-02-01
Coral reefs are threatened at local to global scales by a litany of anthropogenic impacts, including overfishing, coastal development, marine and watershed pollution, rising ocean temperatures, and ocean acidification. However, available data for the primary indicator of coral reef condition — proportional cover of living coral — are surprisingly sparse and show patterns that contradict the prevailing understanding of how environment impacts reef condition. Remote sensing is the only available tool for acquiring synoptic, uniform data on reef condition at regional to global scales. Discrimination between coral and other reef benthos relies on narrow wavebands afforded by imaging spectroscopy. The same spectral information allows non-invasive quantification of photosynthetic pigment composition, which shows unexpected phenological trends. There is also potential to link biodiversity with optical diversity, though there has been no effort in that direction. Imaging spectroscopy underlies the light-use efficiency model for reef primary production by quantifying light capture, which in turn indicates biochemical capacity for CO2 assimilation. Reef calcification is strongly correlated with primary production, suggesting the possibility for an optics-based model of that aspect of reef function, as well. By scaling these spectral models for use with remote sensing, we can vastly improve our understanding of reef structure, function, and overall condition across regional to global scales. By analyzing those remote sensing products against ancillary environmental data, we can construct secondary models to predict reef futures in the era of global change. This final point is the objective of CORAL (COral Reef Airborne Laboratory), a three-year project funded under NASA's Earth Venture Suborbital-2 program to investigate the relationship between coral reef condition at the ecosystem scale and various nominal biogeophysical forcing parameters.
Battelle developing reefs to ease habitat losses
DOE Office of Scientific and Technical Information (OSTI.GOV)
Not Available
1993-04-01
Artificial reefs may be the answer to solving a worldwide problem of declining fish habitats, or they may only be good for creating fishing spots. Researchers at Battelle's Ocean Sciences Laboratory in Duxbury, Massachusetts, are studying artificial reefs in the Delaware River to determine if they are a solution to habitat losses in estuaries and coastal regions. [open quotes]Right now, we don't know if the fish are using the reefs simply as a grazing land, and then moving on, or if they're using the areas to colonize,[close quotes] said researcher Karen Foster. [open quotes]Ultimately, we hope to find they aremore » colonizing.[close quotes] In 1989, Battelle researchers placed 16 prefabricated concrete reefs 45 feet deep in Delaware Bay. The reefs were placed in clusters of four, and monitoring began the following year. The federal government ordered the reefs placed in the bay as a mitigation technique for fish habitat that was lost when the river was dredged for navigational purposes. Researchers examined the reefs twice last summer. It will take five years, Foster said, before researchers can determine if the reefs are increasing the fish population. Early tests show, however, the populations of mussels, sponges, corals, and anemones increased by up to 150 percent over an area of bay bottom where the reefs were placed. Divers take crustacean samples from the reefs, and fish are caught near the reefs for examination. Researchers dissect the fish stomachs and analyze the contents to determine if they have been feeding at the reefs. [open quotes]If we find blue mussels in the stomach of the fish, that's great because we know that blue mussels are growing on the reef,[close quotes] Foster said.« less
Coral Reef Color: Remote and In-Situ Imaging Spectroscopy of Reef Structure and Function
NASA Astrophysics Data System (ADS)
Hochberg, E. J.
2015-12-01
Coral reefs are threatened at local to global scales by a litany of anthropogenic impacts, including overfishing, coastal development, marine and watershed pollution, rising ocean temperatures, and ocean acidification. However, available data for the primary indicator of coral reef condition — proportional cover of living coral — are surprisingly sparse and show patterns that contradict the prevailing understanding of how environment impacts reef condition. Remote sensing is the only available tool for acquiring synoptic, uniform data on reef condition at regional to global scales. Discrimination between coral and other reef benthos relies on narrow wavebands afforded by imaging spectroscopy. The same spectral information allows non-invasive quantification of photosynthetic pigment composition, which shows unexpected phenological trends. There is also potential to link biodiversity with optical diversity, though there has been no effort in that direction. Imaging spectroscopy underlies the light-use efficiency model for reef primary production by quantifying light capture, which in turn indicates biochemical capacity for CO2 assimilation. Reef calcification is strongly correlated with primary production, suggesting the possibility for an optics-based model of that aspect of reef function, as well. By scaling these spectral models for use with remote sensing, we can vastly improve our understanding of reef structure, function, and overall condition across regional to global scales. By analyzing those remote sensing products against ancillary environmental data, we can construct secondary models to predict reef futures in the era of global change. This final point is the objective of CORAL (COral Reef Airborne Laboratory), a three-year project funded under NASA's Earth Venture Suborbital-2 program to investigate the relationship between coral reef condition at the ecosystem scale and various nominal biogeophysical forcing parameters.
The wicked problem of China's disappearing coral reefs.
Hughes, Terry P; Huang, Hui; Young, Matthew A L
2013-04-01
We examined the development of coral reef science and the policies, institutions, and governance frameworks for management of coral reefs in China in order to highlight the wicked problem of preserving reefs while simultaneously promoting human development and nation building. China and other sovereign states in the region are experiencing unprecedented economic expansion, rapid population growth, mass migration, widespread coastal development, and loss of habitat. We analyzed a large, fragmented literature on the condition of coral reefs in China and the disputed territories of the South China Sea. We found that coral abundance has declined by at least 80% over the past 30 years on coastal fringing reefs along the Chinese mainland and adjoining Hainan Island. On offshore atolls and archipelagos claimed by 6 countries in the South China Sea, coral cover has declined from an average of >60% to around 20% within the past 10-15 years. Climate change has affected these reefs far less than coastal development, pollution, overfishing, and destructive fishing practices. Ironically, these widespread declines in the condition of reefs are unfolding as China's research and reef-management capacity are rapidly expanding. Before the loss of corals becomes irreversible, governance of China's coastal reefs could be improved by increasing public awareness of declining ecosystem services, by providing financial support for training of reef scientists and managers, by improving monitoring of coral reef dynamics and condition to better inform policy development, and by enforcing existing regulations that could protect coral reefs. In the South China Sea, changes in policy and legal frameworks, refinement of governance structures, and cooperation among neighboring countries are urgently needed to develop cooperative management of contested offshore reefs. © 2012 Society for Conservation Biology.
Kuffner, Ilsa B.; Brock, John C.; Grober-Dunsmore, Rikki; Bonito, Victor E.; Hickey, T. Donald; Wright, C. Wayne
2007-01-01
The realization that coral reef ecosystem management must occur across multiple spatial scales and habitat types has led scientists and resource managers to seek variables that are easily measured over large areas and correlate well with reef resources. Here we investigate the utility of new technology in airborne laser surveying (NASA Experimental Advanced Airborne Research Lidar (EAARL)) in assessing topographical complexity (rugosity) to predict reef fish community structure on shallow (n = 10–13 per reef). Rugosity at each station was assessed in situ by divers using the traditional chain-transect method (10-m scale), and remotely using the EAARL submarine topography data at multiple spatial scales (2, 5, and 10 m). The rugosity and biological datasets were analyzed together to elucidate the predictive power of EAARL rugosity in describing the variance in reef fish community variables and to assess the correlation between chain-transect and EAARL rugosity. EAARL rugosity was not well correlated with chain-transect rugosity, or with species richness of fishes (although statistically significant, the amount of variance explained by the model was very low). Variance in reef fish community attributes was better explained in reef-by-reef variability than by physical variables. However, once the reef-by-reef variability was taken into account in a two-way analysis of variance, the importance of rugosity could be seen on individual reefs. Fish species richness and abundance were statistically higher at high rugosity stations compared to medium and low rugosity stations, as predicted by prior ecological research. The EAARL shows promise as an important mapping tool for reef resource managers as they strive to inventory and protect coral reef resources.
Budget of coral-derived organic carbon in a fringing coral reef of the Gulf of Aqaba, Red Sea
NASA Astrophysics Data System (ADS)
Naumann, Malik S.; Richter, Claudio; Mott, Claudius; el-Zibdah, Mohammad; Manasrah, Riyad; Wild, Christian
2012-12-01
The continuous release of organic C-rich material by reef-building corals can contribute substantially to biogeochemical processes and concomitant rapid nutrient recycling in coral reef ecosystems. However, our current understanding of these processes is limited to platform reefs exhibiting a high degree of ecosystem closure compared to the globally most common fringing reef type. This study carried out in the northern Gulf of Aqaba (Red Sea) presents the first quantitative budget for coral-derived organic carbon (COC) in a fringing reef and highlights the importance of local hydrodynamics. Diel reef-wide COC release amounted to 1.1 ± 0.2 kmol total organic carbon (TOC) representing 1-3% of gross benthic primary production. Most COC (73%) was released as particulate organic C (POC), the bulk of which (34-63%) rapidly settled as mucus string aggregates accounting for approximately 28% of total POC sedimentation. Sedimentation of mucus strings, but also dilution of suspended and dissolved COC in reef waters retained 82% of diel COC release in the fringing reef, providing a potentially important organic source for a COC-based food web. Pelagic COC degradation represented 0.1-1.6% of pelagic microbial respiration recycling 32% of diel retained COC. Benthic COC degradation contributed substantially (29-47%) to reef-wide microbial respiration in reef sands, including 20-38% by mucus string POC, and consumed approximately 52% of all retained COC. These findings point out the importance of COC as a C carrier for different reef types. COC may further represent a source of organic carbon for faunal communities colonising reef framework cavities complementing the efficient retention and recycling of COC within fringing reef environments.
NASA Astrophysics Data System (ADS)
Vega-Zepeda, A.; Hernández-Arana, H.; Carricart-Ganivet, J. P.
2007-09-01
The Mexican Government decreed Chinchorro Bank reef as a Biosphere Reserve in 1996. The aim of this study was to evaluate the spatial and size-frequency distribution of Acropora spp. in order to provide further knowledge and tools to enhance management. A field survey was conducted, within six regions, to locate and measure Acropora patches in the reef lagoon. Density, colony size and living tissue cover of Acropora colonies were evaluated using the line-intercept transect technique, combining direct observations and video transects. The results showed that Acropora spp. was preferentially distributed in the southern regions; where cover and density were high. Based on these results and considering that Acropora spp. produces landscape heterogeneity, which in turn generates shelter for other species, including some of considerable economic importance, then at least the South East region should be considered as a key area for Acropora species conservation, and should be included in the Chinchorro Bank management plan.
Remote coral reefs can sustain high growth potential and may match future sea-level trends
Perry, Chris T.; Murphy, Gary N.; Graham, Nicholas A. J.; Wilson, Shaun K.; Januchowski-Hartley, Fraser A.; East, Holly K.
2015-01-01
Climate-induced disturbances are contributing to rapid, global-scale changes in coral reef ecology. As a consequence, reef carbonate budgets are declining, threatening reef growth potential and thus capacity to track rising sea-levels. Whether disturbed reefs can recover their growth potential and how rapidly, are thus critical research questions. Here we address these questions by measuring the carbonate budgets of 28 reefs across the Chagos Archipelago (Indian Ocean) which, while geographically remote and largely isolated from compounding human impacts, experienced severe (>90%) coral mortality during the 1998 warming event. Coral communities on most reefs recovered rapidly and we show that carbonate budgets in 2015 average +3.7 G (G = kg CaCO3 m−2 yr−1). Most significantly the production rates on Acropora-dominated reefs, the corals most severely impacted in 1998, averaged +8.4 G by 2015, comparable with estimates under pre-human (Holocene) disturbance conditions. These positive budgets are reflected in high reef growth rates (4.2 mm yr−1) on Acropora-dominated reefs, demonstrating that carbonate budgets on these remote reefs have recovered rapidly from major climate-driven disturbances. Critically, these reefs retain the capacity to grow at rates exceeding measured regional mid-late Holocene and 20th century sea-level rise, and close to IPCC sea-level rise projections through to 2100. PMID:26669758
Remote coral reefs can sustain high growth potential and may match future sea-level trends.
Perry, Chris T; Murphy, Gary N; Graham, Nicholas A J; Wilson, Shaun K; Januchowski-Hartley, Fraser A; East, Holly K
2015-12-16
Climate-induced disturbances are contributing to rapid, global-scale changes in coral reef ecology. As a consequence, reef carbonate budgets are declining, threatening reef growth potential and thus capacity to track rising sea-levels. Whether disturbed reefs can recover their growth potential and how rapidly, are thus critical research questions. Here we address these questions by measuring the carbonate budgets of 28 reefs across the Chagos Archipelago (Indian Ocean) which, while geographically remote and largely isolated from compounding human impacts, experienced severe (>90%) coral mortality during the 1998 warming event. Coral communities on most reefs recovered rapidly and we show that carbonate budgets in 2015 average +3.7 G (G = kg CaCO3 m(-2) yr(-1)). Most significantly the production rates on Acropora-dominated reefs, the corals most severely impacted in 1998, averaged +8.4 G by 2015, comparable with estimates under pre-human (Holocene) disturbance conditions. These positive budgets are reflected in high reef growth rates (4.2 mm yr(-1)) on Acropora-dominated reefs, demonstrating that carbonate budgets on these remote reefs have recovered rapidly from major climate-driven disturbances. Critically, these reefs retain the capacity to grow at rates exceeding measured regional mid-late Holocene and 20th century sea-level rise, and close to IPCC sea-level rise projections through to 2100.
Solar burst precursors and energy build-up at microwave wavelengths
NASA Technical Reports Server (NTRS)
Lang, Kenneth R.; Wilson, Robert F.
1986-01-01
We summarize high-resolution microwave observations (VLA) of heating and magnetic triggering in coronal loops. Magnetic changes that precede solar eruptions on time scales of tens of minutes involve primarily emerging coronal loops and the interaction of two or more loops. Thermal cyclotron lines have been detected in coronal loops, suggesting the presence of hot current sheets that enhance emission from relatively thin layers of enhanced temperature and constant magnetic field. These current sheets may play a role in the excitation of solar bursts. A filament-associated source with a high brightness temperature and steep radiation spectrum occurs above a region of apparently weak photospheric field. This source might be attributed to currents that enhance coronal magnetic fields. Compact (phi=5 sec) transient sources with lifetimes of 30 to 60 minutes have also been detected in regions of apparently weak photospheric field. We conclude by comparing VLA observations of coronal loops with simultaneous SMM-XRP observations.
Solar burst precursors and energy build-up at microwave wavelengths
NASA Astrophysics Data System (ADS)
Lang, Kenneth R.; Wilson, Robert F.
We summarize high-resolution microwave observations (VLA) of heating and magnetic triggering in coronal loops. Magnetic changes that precede solar eruptions on time scales of tens of minutes involve primarily emerging coronal loops and the interaction of two or more loops. Thermal cyclotron lines have been detected in coronal loops, suggesting the presence of hot current sheets that enhance emission from relatively thin layers of enhanced temperature and constant magnetic field. These current sheets may play a role in the excitation of solar bursts. A filament-associated source with a high brightness temperature and steep radiation spectrum occurs above a region of apparently weak photospheric field. This source might be attributed to currents that enhance coronal magnetic fields. Compact (phi=5 sec) transient sources with lifetimes of 30 to 60 minutes have also been detected in regions of apparently weak photospheric field. We conclude by comparing VLA observations of coronal loops with simultaneous SMM-XRP observations.
Magnetic loops, downflows, and convection in the solar corona
NASA Technical Reports Server (NTRS)
Foukal, P.
1978-01-01
Optical and extreme-ultraviolet observations of solar loop structures show that flows of cool plasma from condensations near the loop apex are a common property of loops associated with radiations whose maximum temperature is greater than approximately 7000 K and less than approximately 3,000,000 K. It is suggested that the mass balance of these structures indicates reconnection by means of plasma motion across field lines under rather general circumstances (not only after flares). It is shown that the cool material has lower gas pressure than the surrounding coronal medium. The density structure of the bright extreme ultraviolet loops suggests that downflows of cool gas result from isobaric condensation of plasma that is either out of thermal equilibrium with the local energy deposition rate into the corona, or is thermally unstable. The evidence is thought to indicate that magnetic fields act to induce a pattern of forced convection.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Coral reefs. 230.44 Section 230.44... Aquatic Sites § 230.44 Coral reefs. (a) Coral reefs consist of the skeletal deposit, usually of calcareous... organisms present in growing portions of the reef. (b) Possible loss of values: The discharge of dredged or...
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Coral reefs. 230.44 Section 230.44... Aquatic Sites § 230.44 Coral reefs. (a) Coral reefs consist of the skeletal deposit, usually of calcareous... organisms present in growing portions of the reef. (b) Possible loss of values: The discharge of dredged or...
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Coral reefs. 230.44 Section 230.44... Aquatic Sites § 230.44 Coral reefs. (a) Coral reefs consist of the skeletal deposit, usually of calcareous... organisms present in growing portions of the reef. (b) Possible loss of values: The discharge of dredged or...
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Coral reefs. 230.44 Section 230.44... Aquatic Sites § 230.44 Coral reefs. (a) Coral reefs consist of the skeletal deposit, usually of calcareous... organisms present in growing portions of the reef. (b) Possible loss of values: The discharge of dredged or...
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Coral reefs. 230.44 Section 230.44... Aquatic Sites § 230.44 Coral reefs. (a) Coral reefs consist of the skeletal deposit, usually of calcareous... organisms present in growing portions of the reef. (b) Possible loss of values: The discharge of dredged or...
The U.S. Environmental Protection Agency (EPA) and Caribbean Coral Reef Institute (CCRI) hosted a Coral Reef and Coastal Ecosystems Decision Support Workshop on April 27-28, 2010 at the Caribbean Coral Reef Institute in La Parguera, Puerto Rico. Forty-three participants, includin...
Cinner, Joshua E; Graham, Nicholas A J; Huchery, Cindy; Macneil, M Aaron
2013-06-01
Coral reef fisheries support the livelihoods of millions of people but have been severely and negatively affected by anthropogenic activities. We conducted a systematic review of published data on the biomass of coral reef fishes to explore how the condition of reef fisheries is related to the density of local human populations, proximity of the reef to markets, and key environmental variables (including broad geomorphologic reef type, reef area, and net productivity). When only population density and environmental covariates were considered, high variability in fisheries conditions at low human population densities resulted in relatively weak explanatory models. The presence or absence of human settlements, habitat type, and distance to fish markets provided a much stronger explanatory model for the condition of reef fisheries. Fish biomass remained relatively low within 14 km of markets, then biomass increased exponentially as distance from reefs to markets increased. Our results suggest the need for an increased science and policy focus on markets as both a key driver of the condition of reef fisheries and a potential source of solutions. © 2012 Society for Conservation Biology.
Localizing softness and stress along loops in 3D topological metamaterials
NASA Astrophysics Data System (ADS)
Baardink, Guido; Souslov, Anton; Paulose, Jayson; Vitelli, Vincenzo
2018-01-01
Topological states can be used to control the mechanical properties of a material along an edge or around a localized defect. The rigidity of elastic networks is characterized by a topological invariant called the polarization; materials with a well-defined uniform polarization display a dramatic range of edge softness depending on the orientation of the polarization relative to the terminating surface. However, in all 3D mechanical metamaterials proposed to date, the topological modes are mixed with bulk soft modes, which organize themselves in Weyl loops. Here, we report the design of a 3D topological metamaterial without Weyl lines and with a uniform polarization that leads to an asymmetry between the number of soft modes on opposing surfaces. We then use this construction to localize topological soft modes in interior regions of the material by including defect lines—dislocation loops—that are unique to three dimensions. We derive a general formula that relates the difference in the number of soft modes and states of self-stress localized along the dislocation loop to the handedness of the vector triad formed by the lattice polarization, Burgers vector, and dislocation-line direction. Our findings suggest a strategy for preprogramming failure and softness localized along lines in 3D, while avoiding extended soft Weyl modes.
NASA Technical Reports Server (NTRS)
Tian, Hui; McIntosh, Scott W.; Wang, Tongjiang; Offman, Leon; De Pontieu, Bart; Innes, Davina E.; Peter, Hardi
2012-01-01
Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfv´en waves rather than flows. In a few cases, there seems to be a p/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfv´enic oscillations. In this scenario, the intensity oscillations associated with Alfv´enic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.
NASA Astrophysics Data System (ADS)
Grady, A. E.; Jenkins, C. J.; Moore, L. J.; Potts, D. C.; Burgess, P. M.; Storlazzi, C. D.; Elias, E.; Reidenbach, M. A.
2013-12-01
The incident wave energy dissipated by the structural complexity and bottom roughness of coral reef ecosystems, and the carbonate sediment produced by framework-building corals, provide natural shoreline protection and nourishment, respectively. Globally, coral reef ecosystems are in decline as a result of ocean warming and acidification, which is exacerbated by chronic regional stressors such as pollution and disease. As a consequence of declining reef health, many reef ecosystems are experiencing reduced coral cover and shifts to dominance by macroalgae, resulting in a loss of rugosity and thus hydrodynamic roughness. As coral reef architecture is compromised and carbonate skeletons are eroded, wave energy dissipation and sediment transport patterns--along with the carbonate sediment budget of the coastal environment--may be altered. Using a Delft3D numerical model of the south-central Molokai, Hawaii, fringing reef, we simulate the effects of changing reef states on wave energy and sediment transport. To determine the temporally-varying effects of biotic and abiotic stressors such as storms and bleaching on the reef structure and carbonate production, we couple Delft3D with CarboLOT, a model that simulates growth and competition of carbonate-producing organisms. CarboLOT is driven by the Lotka-Volterra population ecology equations and niche suitability principles, and accesses the CarboKB database for region-specific, carbonate-producing species information on growth rates, reproduction patterns, habitat suitability, as well as organism geometries. Simulations assess how changing reef states--which alter carbonate sediment production and reef morphology and thus hydrodynamic roughness--impact wave attenuation and sediment transport gradients along reef-fronted beaches. Initial results suggest that along fringing reefs having characteristics similar to the Molokai fringing reef, projected sea level rise will likely outpace coral reef accretion, and the increased residual wave energy transported to the coast may result in the alteration of alongshore sediment transport gradients and substantial changes to coastal morphology.
Coral Reefs on the Edge? Carbon Chemistry on Inshore Reefs of the Great Barrier Reef
Uthicke, Sven; Furnas, Miles; Lønborg, Christian
2014-01-01
While increasing atmospheric carbon dioxide (CO2) concentration alters global water chemistry (Ocean Acidification; OA), the degree of changes vary on local and regional spatial scales. Inshore fringing coral reefs of the Great Barrier Reef (GBR) are subjected to a variety of local pressures, and some sites may already be marginal habitats for corals. The spatial and temporal variation in directly measured parameters: Total Alkalinity (TA) and dissolved inorganic carbon (DIC) concentration, and derived parameters: partial pressure of CO2 (pCO2); pH and aragonite saturation state (Ωar) were measured at 14 inshore reefs over a two year period in the GBR region. Total Alkalinity varied between 2069 and 2364 µmol kg−1 and DIC concentrations ranged from 1846 to 2099 µmol kg−1. This resulted in pCO2 concentrations from 340 to 554 µatm, with higher values during the wet seasons and pCO2 on inshore reefs distinctly above atmospheric values. However, due to temperature effects, Ωar was not further reduced in the wet season. Aragonite saturation on inshore reefs was consistently lower and pCO2 higher than on GBR reefs further offshore. Thermodynamic effects contribute to this, and anthropogenic runoff may also contribute by altering productivity (P), respiration (R) and P/R ratios. Compared to surveys 18 and 30 years ago, pCO2 on GBR mid- and outer-shelf reefs has risen at the same rate as atmospheric values (∼1.7 µatm yr−1) over 30 years. By contrast, values on inshore reefs have increased at 2.5 to 3 times higher rates. Thus, pCO2 levels on inshore reefs have disproportionately increased compared to atmospheric levels. Our study suggests that inshore GBR reefs are more vulnerable to OA and have less buffering capacity compared to offshore reefs. This may be caused by anthropogenically induced trophic changes in the water column and benthos of inshore reefs subjected to land runoff. PMID:25295864
Doropoulos, Christopher; Ward, Selina; Roff, George; González-Rivero, Manuel; Mumby, Peter J.
2015-01-01
Tropical reefs are dynamic ecosystems that host diverse coral assemblages with different life-history strategies. Here, we quantified how juvenile (<50 mm) coral demographics influenced benthic coral structure in reef flat and reef slope habitats on the southern Great Barrier Reef, Australia. Permanent plots and settlement tiles were monitored every six months for three years in each habitat. These environments exhibited profound differences: the reef slope was characterised by 95% less macroalgal cover, and twice the amount of available settlement substrata and rates of coral settlement than the reef flat. Consequently, post-settlement coral survival in the reef slope was substantially higher than that of the reef flat, and resulted in a rapid increase in coral cover from 7 to 31% in 2.5 years. In contrast, coral cover on the reef flat remained low (~10%), whereas macroalgal cover increased from 23 to 45%. A positive stock-recruitment relationship was found in brooding corals in both habitats; however, brooding corals were not directly responsible for the observed changes in coral cover. Rather, the rapid increase on the reef slope resulted from high abundances of broadcast spawning Acropora recruits. Incorporating our results into transition matrix models demonstrated that most corals escape mortality once they exceed 50 mm, but for smaller corals mortality in brooders was double those of spawners (i.e. acroporids and massive corals). For corals on the reef flat, sensitivity analysis demonstrated that growth and mortality of larger juveniles (21–50 mm) highly influenced population dynamics; whereas the recruitment, growth and mortality of smaller corals (<20 mm) had the highest influence on reef slope population dynamics. Our results provide insight into the population dynamics and recovery trajectories in disparate reef habitats, and highlight the importance of acroporid recruitment in driving rapid increases in coral cover following large-scale perturbation in reef slope environments. PMID:26009892
Doropoulos, Christopher; Ward, Selina; Roff, George; González-Rivero, Manuel; Mumby, Peter J
2015-01-01
Tropical reefs are dynamic ecosystems that host diverse coral assemblages with different life-history strategies. Here, we quantified how juvenile (<50 mm) coral demographics influenced benthic coral structure in reef flat and reef slope habitats on the southern Great Barrier Reef, Australia. Permanent plots and settlement tiles were monitored every six months for three years in each habitat. These environments exhibited profound differences: the reef slope was characterised by 95% less macroalgal cover, and twice the amount of available settlement substrata and rates of coral settlement than the reef flat. Consequently, post-settlement coral survival in the reef slope was substantially higher than that of the reef flat, and resulted in a rapid increase in coral cover from 7 to 31% in 2.5 years. In contrast, coral cover on the reef flat remained low (~10%), whereas macroalgal cover increased from 23 to 45%. A positive stock-recruitment relationship was found in brooding corals in both habitats; however, brooding corals were not directly responsible for the observed changes in coral cover. Rather, the rapid increase on the reef slope resulted from high abundances of broadcast spawning Acropora recruits. Incorporating our results into transition matrix models demonstrated that most corals escape mortality once they exceed 50 mm, but for smaller corals mortality in brooders was double those of spawners (i.e. acroporids and massive corals). For corals on the reef flat, sensitivity analysis demonstrated that growth and mortality of larger juveniles (21-50 mm) highly influenced population dynamics; whereas the recruitment, growth and mortality of smaller corals (<20 mm) had the highest influence on reef slope population dynamics. Our results provide insight into the population dynamics and recovery trajectories in disparate reef habitats, and highlight the importance of acroporid recruitment in driving rapid increases in coral cover following large-scale perturbation in reef slope environments.
Particulate organic matter fluxes and hydrodynamics at the Tisler cold-water coral reef
NASA Astrophysics Data System (ADS)
Wagner, Hannes; Purser, Autun; Thomsen, Laurenz; Jesus, Carlos César; Lundälv, Tomas
2011-03-01
Cold-water coral reefs occur in many regions of the world's oceans. Fundamental questions regarding their functioning remain unanswered. These include the biogeochemical influence of reefs on their environment ("reef effects") and the influence of hydrodynamic processes on reef nutrition. In a succession of field campaigns in 2007 and 2008, these questions were addressed at the Tisler cold-water coral reef, which is centered on a sill peak in the Norwegian Skagerrak. A variety of methodological approaches were used. These consisted of the collection of CTD and chlorophyll profiles, current measurements, sampling of particulate organic matter (POM) in the benthic boundary layer (BBL) across the reef with subsequent chemical analyses, and the chemical analysis of freshly released Lophelia pertusa mucus. CTD and chlorophyll profiles indicated that downstream of the sill crest, downwelling delivered warmer, fresher and chlorophyll richer water masses down to the BBL. Both sides of the reef received downwelling nutrition delivery, as flow direction over the reef reversed periodically. Several chemical composition indicators revealed that suspended POM was significantly fresher on the downstream side of the reef than on the upstream side. L. pertusa mucus from the Tisler Reef was labile in composition, as indicated by a low C/N ratio and a high amino acid degradation index (DI) value. Particulate organic carbon (POC) content in the BBL was significantly depleted across the reef. Lateral depositional fluxes were calculated to be 18-1485 mg POC m -2 d -1, with a mean of 459 mg POC m -2 d -1. We propose that the combination of fresh, downwelling POM with mucus released from the reef was the cause of the greater lability of the downstream POM. Our data on POC depletion across the reef suggest that cold-water coral reefs could play an important role in carbon cycling along continental margins.
Near-reef elemental signals in the otoliths of settling Pomacentrus amboinensis (Pomacentridae)
NASA Astrophysics Data System (ADS)
Sih, Tiffany L.; Kingsford, Michael J.
2016-03-01
Settlement is a key life history transition for coral reef fishes, and how long a fish spends close to a reef prior to settlement is poorly understood. We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and otolith microstructure analysis (daily increments and settlement marks) to determine the length of time larval fish spend near a reef prior to settlement. The otoliths of Pomacentrus amboinensis collected from four neighbouring reefs in the southern Great Barrier Reef showed clear and consistent differences in their elemental signatures prior to and following settlement. Elevated Ba:Ca near settlement and post-settlement was found in fish from all four reefs. However, there was individual variation in elemental profiles, with an increased otolith Ba-to-Ca ratio (near-reef signature) at settlement in 33 % of fish, and up to 8 d prior to settlement in others. Increment widths, often used as a proxy for growth, decreased approaching the settlement mark for all fish, providing further evidence for a "search phase" in larvae. We demonstrated experimentally that otoliths of fish kept in reefal or inter-reefal waters had different elemental chemistry. There were differences in the elemental composition of water samples within the study area, but no consistent trends with distance from reefs. There was poor discrimination of multi-element signatures among fish from different reefs during their pre-settlement phases. However, discrimination improved in the settlement and post-settlement phases of otoliths, indicating that reef waters and perhaps stage of ontogeny affected otolith chemistry. This study demonstrated clear near-reef elemental signatures in fish around settlement. We suggest these differences are due to a combination of water chemistry and physiological influences (e.g., growth). Combining LA-ICP-MS with otolith microstructure analysis can provide high-resolution information on the early life history of reef fishes. Further, a near-reef "search phase" prior to settlement may be common in reef fishes.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kauffman, E.G.
Throughout the Mesozoic, shallow-water carbonate ramps and platforms of the circumequatorial Tethyan Ocean were characterized by extensive development of reef ecosystems, especially during times of eustatic highstand, expansion of the Tropics, and warm equable global climates. The greatest reef development was north of the paleoequator in the Caribbean and Indo-Mediterranean provinces. These reefs and associated debris facies comprise major petroleum reservoirs, in some cases with remarkable porosity and permeability normally attributed to a combination of sedimentologic, tectonic, and diagenetic factors. The biological evolution of Mesozoic reefs also has had an important, and in some cases dominant, role in determining reservoirmore » quality. Three major biological factors are critical to mesozoic reef-associated reservoir development: (1) the replacement/competitive displacement of coral-algal dominated, highly integrated reef ecosystems by loosely packed rudistid bivalve-dominated reef ecosystems in the Barremian-Albian; (2) the evolution of dominantly aragonitic, highly porous shells among framework-building rudistids in the middle and Late Cretaceous; and (3) competitive strategies among rudistids that effectively prevented widespread biological binding of Cretaceous reefs, leading to the production of large marginal fans that comprise major carbonate reservoirs. Detailed studies of these evolutionary trends in reef/framework development and of the distribution of different groups of bioconstructors on reefs lead to predictive modeling for primary and secondary porosity development in mesozoic carbonate reservoirs. The competitive displacement of coral-algal communities by rudistids on Cretaceous reefs was so effective that, even after Maastrichtian mass extinction of rudistids and other important groups comprising Mesozoic reef/carbonate platform ecosystems, coral-algal reef-building communities did not evolve again until the late Eocene.« less