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Time series measurements of water transparency, water temperature, and current velocity were made at a station located in 58 m of water in southern Lake Michigan during the summer of 1995. Currents generated by near-inertial internal waves are correlated with variations in the thickness and in the vertical distribution of suspended sediment in the benthicnepheloidlayer. Although a direct
Time series observations of water temperature, water transparency, and current velocity were made at four stations located on the lake slope of southeastern Lake Michigan. The observations show that during stratified conditions the benthicnepheloidlayer is probably not maintained by the local resuspension of bottom sediment. A more likely source is sediment resuspended further inshore and then transported across
Average 14 C ages of dissolved organic carbon (DOC) in the ocean are 3-6,000 years, and are influenced by old DOC from continental margins. However, sources of DOC from terrestrial, autochthonous, and sedimentary organic carbon seem to be too young to be responsible for the old DOC observed in the ocean. Since colloidal organic carbon (COC, i.e., high molecular weight DOC), which is chemically very similar to that of bulk DOC, can be effectively isolated from seawater using cross-flow ultrafiltration, it can hold clues to sources and pathways of DOC turnover in the ocean. Radiocarbon measurements on COC in the water column and benthicnepheloidlayer (BNL) from two continental margin areas (the Middle Atlantic Bight and the Gulf of Mexico) and controlled laboratory experiments were carried out to study sources of old DOC in the ocean margin areas. Vertical distributions of suspended particulate matter (SPM), particulate organic carbon (POC), nitrogen (PON), and DOC in the water column and bottom waters near the sediment-water interface all demonstrate a well developed benthicnepheloidlayer in both ocean margin areas. 14 C values of COC isolated from the BNL (ranging from -362 ± 4 to -456 ± 3 ) were distinctly lower than their counterparts in surface waters (with a range of >0 to -210 ± 5 ). In other words, COC from the BNL was much older than COC from the overlying water column. These results, together with strong concentration gradients of SPM, POC, PON, and DOC, suggest a sedimentary source for organic carbon species and possibly for old COC as well in BNL waters. This is confirmed by the results from controlled laboratory experiments which showed that COC isolated from sediment resuspension had 14 C values between -260 and -352 , which are significantly lower than those of bulk sediment (-87 ± 6 ) or resuspended particles (-138 ± 8 ). The heterogeneity of 14 C signatures in bulk SOC thus points to a preferential release of old organic components from sediment resuspension, which can be the transport mechanism of the old benthic COC observed in ocean margin areas. Old COC from continental margin nepheloidlayers may thus be a potential source of old DOC to the deep ocean.
According to previous studies, the surface circulation of the Gulf of Valencia (GoV) is characterized by a convergence between the southwestward Northern Current carrying old Atlantic Waters (oAW) and the northward intrusions of recent Atlantic Waters (rAW) imported through the Ibiza Channel. This paper focuses on the distribution of the suspended sediment concentration in the GoV obtained from a dense grid of CTD observations in June 1995 during the oceanographic cruise MESO'95 (MESOscale processes). We evaluate the relation between currents, water masses and the nepheloid structure at the time of the survey. Results showed higher suspended sediment concentration (SSC) in the oAW than in the rAW. At the shelf-break depth, an important detachment of particulate matter was observed off Cap La Nao, extending seawards all across the Ibiza Channel. The presence of this intermediate nepheloidlayer detachment indicates a preferential off-shelf sediment export at the southern end of the GoV, where the orientation of the continental margin changes, and oAW and rAW merge. On the continental slope, several nepheloidlayers detachments were observed between 400 and 600 m, where the Levantine Intermediate Water (LIW) interacts with the seafloor, suggesting the possible presence of internal waves causing sediment resuspension and/or maintaining particles in suspension in the mid-slope region. A bottom nepheloidlayer was also observed at deeper locations along the central and southern part of the GoV continental slope, but not at the Ibiza Sill.
Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloidlayer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary. ?? Springer-Verlag 2008.
Poppe, L. J.; McMullen, K. Y.; Williams, S. J.; Crocker, J. M.; Doran, E. F.
Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloidlayer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary.
Poppe, L. J.; McMullen, K. Y.; Williams, S. J.; Crocker, J. M.; Doran, E. F.
Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloidlayer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloidlayer of the basins west of the Mid-Atlantic Ridge, resulting from interaction of abyssal currents with the bottom, range from ??? 2 ?? 106 tons in the equatorial Guyana Basin to ??? 50 ?? 106 tons in the North American Basin. The total resuspended particulate load in the western basins (111 ?? 106 tons) is almost an order of magnitude greater than that in the basins east of the Mid-Atlantic Ridge (13 ?? 106 tons). The net northward flux of resuspended particles carried in the AABW drops from ??? 8 ?? 106 tons/year between the southern and northern ends of the Brazil Basin and remains ??? 1 ?? 106 tons/year across the Guyana Basin. ?? 1977.
Average 14C ages of dissolved organic carbon (DOC) in the ocean are 36,000 years, and are influenced by old DOC from continental margins. However, sources of DOC from terrestrial, autochthonous, and sedimentary organic carbon seem to be too young to be responsible for the old DOC observed in the ocean. Since colloidal organic carbon (COC, i.e., high molecular weight DOC),
HEBBLE's precise aim is to develop and to test explicit predictions about the response of adhesive/cohesive marine sediments to imposed and controlled stresses [Hollister et al., 1980; Kerr, 1980]. Pursuit of this goal has necessitated a co-ordinated, interdisciplinary effort, to date including physical oceanographers, sedimentologists, radiochemists and biochemists, and biological oceanographers.Current produced bed features reflect significant momentum exchange between the fluid boundary layer and the sediment surface. From photographs, and the few current meter records available, it appears that vast areas of the deep sea are presently being modified by energetic flows. The bed forms range in scale from kilometers to millimeters and are found where near bottom currents have been delineated by maxima in near bottom potential temperature. Moreover, on the Scotian Rise for example, many of these bedforms are being produced by present day currents because rapid destruction of the features by benthic organisms is evidenced in stereo-photographs.
Nowell, Arthur R. M.; Hollister, Charles D.; Jumars, Peter A.
This special issue ofGeo-Marine Letters Benthic Boundary Layer Processes in Coastal Environments includes 20 papers devoted to results of recent near-shore experiments supported by the Coastal Benthic Boundary Layer (CBBL) program. Experiments were conducted in gas-rich muddy sediments of Eckernförde Bay of the Baltic Sea and on relict sandy sediments of the West Florida Sand Sheet. In this introductory paper
Interdisciplinary research is certainly one of the current buzzwords that needs to be incorporated in virtually every grant proposal. The idea that integration of different scientific fields is a prerequisite for progress in Earth sciences is now well recognized. The benthic boundary layer (BBL) is one area of research in which physicists, chemists, biologists, geologists, and engineers have worked in close and fruitful cooperation for several decades. The BBL comprises the near-bottom layer of water, the sediment-water interface, and the top layer of sediment that is directly influenced by the overlying water. In 1974, a BBL conference in France resulted in a book titled The Benthic Boundary Layer edited by I.N. McCave. This publication contained contributions from scientists from a wide range of disciplines and gave an overview of the state-of-the-art of BBL research. However, science has moved on in the past 25 years. Significant conceptual and technological progress has been made, and it is definitely time for an update.
Recent geopolitical changes have shifted the emphasis of U.S. naval operations from deep ocean to nearshore coastal regions. In response to this shift, the Office of Naval Research (ONR) established the Coastal Benthic Boundary Layer Special Research Prog...
This paper investigates the dynamics of an internal hydraulic jump in a river plume and associated suspended sediment dispersal. Field investigations were undertaken into the river plume generated by the Herbert River, Australia, following a moderate flood event induced by Cyclone Fritz in 2004. The forced plume experiences an abrupt transition from supercritical to subcritical via an internal hydraulic jump, as defined by a mode-1 internal Froude number computed using the phase speeds from the Taylor-Goldstein equation. The hydraulic theory of a two-layer stratified flow was used to identify the plume shape and the mechanical energy loss within the jump. The hydraulic jump energy loss is primarily transferred to the buoyancy-driven potential energy, uplifting the river plume. Intense stratification decreases the bottom stress, damping the resuspension. Therefore, a separative nepheloid dispersal system occurs at the jump section. Both the upper and lower nepheloid flows are confined to the inner shelf, but have different dispersal behaviors and mechanisms. The upper nepheloid flow, which is primarily controlled by advection and settling, satisfies an exponential decay law of the total suspended sediment concentrations versus the offshore distance. The lower nepheloid flow dominated by deposition is detached seaward near the lift-off point of the river plume. A turbidity front associated with the jump may accumulate a large quantity of suspended sediments, enhancing sediment release from the river plume. These findings will promote in-depth understanding of both the cross-shelf sediment dispersal and muddy deposit on the shelf.
New data from closely spaced hydrocasts, thermograd profiles, vertical nephelometer profiles, and direct bottom current observations within the Vema Channel (near 30°13'S) allow an interpretation of the flow regime and the structure of the benthic boundary layer. A sharp gradient in potential temperature, light scattering, concentration of suspended particulates, and excess radon is present in the transition zone between northward
David A. Johnson; Scott E. McDowell; Lawrence G. Sullivan; Pierre E. Biscaye
The goal of this research is to develop greater understanding of the how the flocculation of fine-grained sediment responds to turbulent stresses and how this packaging of sediment affects optical and acoustical properties in the water column. Objectives ...
E. Boss J. H. Trowbridge P. S. Hill T. G. Milligan
Between 1965 and 1969, fifty-one profiles of light scattering were made in the central Arctic Ocean from Fletcher's Ice Island (T-3). The profiles, taken with an in situ photographic nephelometer extend from just below the surface to the bottom. Two distinctly different types of profiles were observed. At all stations the strongest scattering occurs near the surface, decreasing with depth
With there being few if any well organized field experiments in Lake Erie on benthic boundary layer (BBL) physics to review, this paper summarizes theoretical and experimental observations from the ocean, estuary, and continental shelf research, contrasts the Lake Erie setting wi...
A primary objective of this study was to characterize the corrosive potential of the benthic boundary layer at a site where selected metal alloys were being exposed. Those properties of sea water and sediment likely to affect the corrosion of alloys that ...
The significance of the transport of nutrient-rich hypolimnetic water via the benthic boundary layer (BBL) to the productivity of Mono Lake was studied using a coupled hydrodynamic and ecological model validated against field data. The coupled model enabled us to differentiate between the role of biotic components and hydrodynamic forcing on the internal recycling of nutrients necessary to sustain primary productivity. A 4-year period (19911994) was simulated in which recycled nutrients from zooplankton excretion and bacterially-mediated mineralization exceeded sediment fluxes as the dominant source for primary productivity. Model outputs indicated that BBL transport was responsible for a 53% increase in the flux of hypolimnetic ammonium to the photic zone during stratification with an increase in primary production of 6% and secondary production of 5%. Although the estimated impact of BBL transport on the productivity of Mono Lake was not large, significant nutrient fluxes were simulated during periods when BBL transport was most active.
Bruce, Louise C; Jellison, Robert; Imberger, Jorg; Melack, John M
The significance of the transport of nutrient-rich hypolimnetic water via the benthic boundary layer (BBL) to the productivity of Mono Lake was studied using a coupled hydrodynamic and ecological model validated against field data. The coupled model enabled us to differentiate between the role of biotic components and hydrodynamic forcing on the internal recycling of nutrients necessary to sustain primary productivity. A 4-year period (1991-1994) was simulated in which recycled nutrients from zooplankton excretion and bacterially-mediated mineralization exceeded sediment fluxes as the dominant source for primary productivity. Model outputs indicated that BBL transport was responsible for a 53% increase in the flux of hypolimnetic ammonium to the photic zone during stratification with an increase in primary production of 6% and secondary production of 5%. Although the estimated impact of BBL transport on the productivity of Mono Lake was not large, significant nutrient fluxes were simulated during periods when BBL transport was most active. PMID:18710583
Bruce, Louise C; Jellison, Robert; Imberger, Jörg; Melack, John M
In aquatic benthic environments, hydrodynamic transport of mass and momentum have shaped the evolution of form-function relationships. Animals whose life cycle depends on success in such environments have developed the biological structure and behavioral mechanisms to sustain dynamic stresses and complex chemical signals. It has become increasingly clear that understanding the ecology of these organisms is dependent on examining the complexities of the turbulent environment. In this dissertation, hydrodynamics and the structure of chemical signals within turbulent boundary layer flows are examined in the context of natural and biological systems. Experiments were conducted in the benthic region of a water flume using a combination of point-measurement and full-field imaging techniques. There are three areas of focus within the complete body of work: (1) The accuracy of an acoustic measurement technique commonly used in natural flows was evaluated. Errors in the technique, primarily attributed to a sampling volume that is large relative to the scales of motion in turbulent flows, were found to be larger than and extend farther from the bed than previously reported. (2) A three-dimensional laser-based imaging system was developed for quantifying turbulent scalar structure. The system was employed to study the topology and orientation of structure within a bed-level, passively released scalar plume. (3) Hydrodynamic stresses were measured near marine fouling communities in a study aimed at predicting larval settlement probabilities. Turbulent stresses, and by extension, the suitability of microhabitats, were found to be highly dependent on local topography and outer-scale flow conditions. This body of work advances the field of experimental fluid mechanics by contributing to the development of methods for quantifying turbulent flows, as well as furthering current understanding of the capabilities and limitations associated with new and existing techniques. Statistical analysis and flow visualization were employed to extract trends from the data with the goal of contributing to the science of prediction, specifically to the benefit of benthic ecology. Ecological applications in the aquatic sciences consistently guided the design of experiments and analysis of results, although the methods of assessment (both experimental and numerical) are generally applicable to the study of fluid physics in a broader context.
It is often hypothesized that the locus of a thermal shelf fronts is where the water depth (D) is equal to the thickness of the tidal frictional bottom boundary layer h. To determine the proper scales for tidal benthic boundary layers, we present simple, but rather general arguments which demonstrate that benthic boundary layers (BBL) in neutrally stratified environment must be defined by Ekman scale Le=u*/Ù, where u* is friction velocity, based on the bottom stress ôb=pu2*, p-water density, and Ù-Coriolis parameter. This result differs from those suggested by the numerical simulation of the formation of BBL in initially continuously stratified fluid, subject to a suddenly imposed barotropic pressure gradient as well as by direct observations of the intensity of turbulence close to the sea bottom, which indicated that the thickness of the well-mixed turbulent region close to the bottom of the sea is very often significantly less than Le. Recently, Stigebrandt has argued that it can be explained by introducing the numerical constant ë in the expression h = ë Le (ë [[SYMBOL MISSING
One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic primary production can proceed is poorly quantified. Here, we use a new analysis of satellite (SeaWiFS) data collected between 1998 and 2003 to estimate, for the first time at a nearly global scale, the irradiance reaching the bottom of the coastal ocean. The following cumulative functions provide the percentage of the surface (S) of the coastal zone receiving an irradiance greater than Ez (in mol photons m-2 d-1): SNon-polar = 29.61 - 17.92 log10(Ez) + 0.72 log102(Ez) + 0.90 log103(Ez) SArctic = 15.99 - 13.56 log10(Ez) + 1.49 log102(Ez) + 0.70 log103(Ez) Data on the constraint of light availability on the major benthic primary producers and net community production are reviewed. Some photosynthetic organisms can grow deeper than the nominal bottom limit of the coastal ocean (200 m). The minimum irradiance required varies from 0.4 to 5.1 mol photons m-2 d-1 depending on the group considered. The daily compensation irradiance of benthic communities ranges from 0.24 to 4.4 mol photons m-2 d-1. Data on benthic irradiance and light requirements are combined to estimate the surface area of the coastal ocean where (1) light does not limit the distribution of primary producers and (2) net community production (NCP, the balance between gross primary production and community respiration) is positive. Positive benthic NCP can occur over 33% of the global shelf area. The limitations of this approach, related to the spatial resolution of the satellite data, the parameterization used to convert reflectance data to irradiance, the lack of global information on the benthicnepheloidlayer, and the relatively limited biological information available, are discussed.
Gattuso, J.-P.; Gentili, B.; Duarte, C. M.; Kleypas, J. A.; Middelburg, J. J.; Antoine, D.
The state of the benthic component of the shelf ecosystem is strongly influenced by availability of dissolved oxygen. The chemical structure of the Black Sea waters is largely determined by the location and the strength of the pycnocline. Due to similarity in the mechanisms of vertical exchanges the oxycline and the chemocline occur at the same depth intervals as the halocline and pycnocline (Özsoy and Ünlüata, 1997). As the data for dissolved oxygen on the shelf is relatively sparse we assume that much abundant data on physical parameters (temperature and salinity) can be used as proxy in determining the location of the oxycline and hence the spatial extent of near-bottom waters depleted in oxygen. When the waters of the benthic boundary layers below the pycnocline are locked' i.e. unable to mix vertically with surface then the biological pump and supply of oxygen are suppressed. However, the locked water can, in principle, move horizontally', predominantly along the constant density levels and get ventilated via isopycnal exchanges. The isopycnals in the Black Sea have generally a dome-like structure, so that the isopycnal movements across the shelf break can ventilate bottom shelf waters with water masses from upper parts of the water column in the deep sea. We use the intra- and inter-annual variations in the near-bottom temperature as indicators for variability of physical conditions in the benthic boundary layer on the shelf. The physical reason for this is that interannual variations in the near-bottom temperature are directly related with the volume of cold waters (Ivanov et al., 2000) which are formed on the shelf and then exported into the deep sea, so that variations in temperature may indicate changes in the intensity of horizontal exchanges. In this paper we identified areas on the Black Sea margin where bottom waters can not be mixed vertically (locked' waters) during the winter months and locations to which the locked waters can move horizontally'. The potential energy approach was used to identify the spatial and temporal variability of the areas and volumes occupied by the locked waters. This approach allows to assess a relative strength of the ability of locked waters to mix vertically with oxygen rich surface waters as compared to horizontal' exchanges with the deep sea along isopycnic surfaces. Analysis of interannual variability of temperature showed that the period 1965-1983 was a warm period when the summer' season ( May to November) temperatures of the benthic waters were higher than the average; to the contrary the period 1983-2001 (i.e. up to end of available data sets) was a cold period. Correlations between various time series of hydrographical and meteorological parameters were calculated to establish the relative importance of vertical versus horizontal exchanges in ventilation of the locked water masses. A low correlation (R=0.24) was obtained between the variation of the winter sea surface temperature on the shelf and the summer' temperatures of locked waters. A higher correlation (R=0.56) was found between the summer temperatures of the Cold Intermediate Waters below the seasonal pycnocline in the deep sea (density range sigma-theta= 14.2-14.8) and the summer' temperatures of the locked' waters in the benthic boundary layer on the shelf. Analysis shows that the isopycnic exchanges with the deep sea are more important for ventilation of the benthic boundary layer on the shelf than winter convection on the shelf itself. This work was made possible via support from EU FP6 SESAME and EU FP7 MyOcean projects and NERC PhD studentship. References Özsoy, E. and Ünlüata, Ü., 1997. Oceanography of the Black Sea: a review of some recent results. Earth-Sci. Rev., 42(4): 231-272. Ivanov, L.I., Belokopytov, V.N., Özsoy, E. and Samodurov, A., 2000. Ventilation of the Black Sea pycnocline on seasonal and interannual time scales. Mediterr. Mar. Sci., 1/2: 61-74.
The Benthic Boundary Layer (BBL) assemblages from the Cap-Ferret Canyon (Bay of Biscay) were quantitatively sampled at two sites located within its main channel near mooring deployments (Mooring Sites MS 1: ca. 2400m; MS 2: ca. 3000m) with a suprabenthic sled equipped with four nets fishing at different heights above the bottom. The macrofaunal abundance above the sea-floor was mainly
Near bottom water samples and sediments were taken during five cruises to 6 stations forming a transect across the N.W. European Continental Margin at Goban Spur. Flow velocity spot measurements in the benthic boundary layer (BBL) always increased from the shelf to the upper slope (1470 m) from 5 to 9 cm s?1 in spring\\/summer and from 15 to 37
Changes in land use and intensification of agricultural pressure have greatly accelerated the alteration of the landscape in most developed countries. These changes may greatly disturb the adjacent ecosystems, particularly streams, where the effects of pollution are amplified. In this study, we used the leaf litter breakdown rate to assess the functional integrity of stream ecosystems and river sediments along a gradient of either traditional extensive farming or a gradient of vineyard area. In the benthiclayer, the total litter breakdown process integrates the temporal variability of the anthropogenic disturbances and is strongly influenced by land use changes in the catchment even though a low concentration of toxics was measured during the study period. This study also confirmed the essential role played by amphipods in the litter breakdown process. In contrast, microbial processes may have integrated the variations in available nutrients and dissolved oxygen concentrations, but failed to respond to the disturbances induced by vineyard production (the increase in pesticides and metal concentrations) during the study period. The response of microbes may not be sensitive enough for assessing the global effect of seasonal agricultural practices. Finally, the leaf litter breakdown measured in the hyporheic zone seemed mainly driven by microbial activities and was hence more affected by vertical exchanges with surface water than by land use practices. However, the breakdown rate of leaf litter in the hyporheic zone may constitute a relevant way to evaluate the impact on river functioning of any human activities that induce massive soil erosion and sediment clogging. PMID:21794895
Piscart, Christophe; Navel, Simon; Maazouzi, Chafik; Montuelle, Bernard; Cornut, Julien; Mermillod-Blondin, Florian; des Chatelliers, Michel Creuze; Simon, Laurent; Marmonier, Pierre
The Benthic Boundary Layer (BBL) assemblages from the Cap-Ferret Canyon (Bay of Biscay) were quantitatively sampled at two sites located within its main channel near mooring deployments (Mooring Sites MS 1: ca. 2400 m; MS 2: ca. 3000 m) with a suprabenthic sled equipped with four nets fishing at different heights above the bottom. The macrofaunal abundance above the sea-floor was mainly represented by Isopoda (42.2%), Amphipoda (19.0%), Euphausiacea (17.3%), Cumacea (13.5%), Mysidacea (2.8%) and Tanaidacea (2.6%). At both sampling sites, the highest total densities were generally recorded in the immediate vicinity of the sea floor (10-40 cm water layer), and a drastic decrease occurred higher in the BBL community. The BBL assemblages from the two sampling sites were similar in their faunal composition (major taxa), and their mean density estimates were not statistically different (MS 1 : 525.3 ind. 100 m -2; MS 2 : 283.3 ind. m -2) although the recorded values during each cruise were always lower at the deeper site. The BBL macrofauna abundance showed obvious temporal fluctuations at both sites, probably linked with a seasonal organic input from the euphotic zone (vertical flux) via phytodetritus deposition on the sea bottom.
The wave-induced velocity and pressure fields beneath a large amplitude internal solitary wave of depression propagating over a smooth, flat, horizontal, and rigid boundary in a shallow two-layer fluid are computed numerically. A numerical ocean model is utilised, the set-up of which is designed and tuned to replicate the previously published experimental results of Carr and Davies (Phys Fluids 18(1):016,601-1-016,601-10, 2006). Excellent agreement is found between the two data sets and, in particular, the numerical simulation replicates the finding of a reverse flow along the bed aft of the wave. The numerically computed velocity and pressure gradients confirm that the occurrence of the reverse flow is a consequence of boundary layer separation in the adverse pressure gradient region. In addition, vortices associated with the reverse flow are seen to form near the bed.
Thiem, Øyvind; Carr, Magda; Berntsen, Jarle; Davies, Peter A.
Experiments are described which model some features of anticyclonic eddies in the benthic boundary layer. Eddies were created in a two-layer stratified rotating fluid, by "squashing" a column of water in the centre of a tank on a rotating table. Ekman suction into the bottom boundary layer caused thinning of the lower layer in the core of the eddy. If the eddy was sufficiently strong, a "bare-spot" (i.e. a region over which the lower layer was no longer present) bounded by a front where the interface intersected the lower boundary was formed. These are similar to the "bare-spots" described by LINDEN and VAN HEIJST (1984, Journal of Fluid Mechanics, 143, 69-94). Formation of a bare-spot reduced the time required for the spin-up of the upper layer. When F = V/(g'H 2) 1/2 ? 1 (V = azimuthal velocity, g' = reduced gravity of the interface and H 2 = the initial depth of the lower layer) , upper-layer fluid in the bottom Ekman layer was observed to intrude under the denser lower layer. Instabilities, initially in the form of two-dimensional rolls, soon developed on the intruding layer. This resulted in mixing between the initial upper and lower layers. Baroclinic instabilities of the front were observed and it is shown that Ekman dissipation increases the wavelength of the fastest growing disturbances. The possibility of the formation of fronts in the benthic boundary layer is discussed.
A physical model, supported by field experiments, predicts that body and substratum morphology of benthic organisms can determine the particle composition encountered by the organisms. The model is based on the velocity gradient of boundary-layer flows, its resultant particle distribution, and the flow pattern induced by bluff bodies (benthic organisms and substrata). The various body morphologies of benthic organisms can
As part of an extensive program to monitor the health of reservoirs in the TVA system, dredges were used to sample benthic life at 36 locations on 12 Tennessee Valley Authority reservoirs and the Tennessee River downstream from the lowest reservoir in the system. Up to ten dredge samples were collected from forebay, transition zone, and inflow locations of typical reservoirs. The survey was conducted between mid March and mid April, 1990. Results are described.
HEBBLE's precise aim is to develop and to test explicit predictions about the response of adhesive\\/cohesive marine sediments to imposed and controlled stresses [Hollister et al., 1980; Kerr, 1980]. Pursuit of this goal has necessitated a co-ordinated, interdisciplinary effort, to date including physical oceanographers, sedimentologists, radiochemists and biochemists, and biological oceanographers.Current produced bed features reflect significant momentum exchange between the
Arthur R. M. Nowell; Charles D. Hollister; Peter A. Jumars
Size structure, taxonomic composition and bioturbation potential of benthic metazoan communities were examined at three contrasting sites on the northwest European continental margin as part of a wider study of biogeochemical cycling in the deep-sea benthic boundary layer. Sampling was conducted in the HattonRockall Basin (1100 m depth), on the North Feni Ridge (1920 m) and in the South Rockall
Size structure, taxonomic composition and bioturbation potential of benthic metazoan communities were examined at three contrasting sites on the northwest European continental margin as part of a wider study of biogeochemical cycling in the deep-sea benthic boundary layer. Sampling was conducted in the Hatton Rockall Basin (1100 m depth), on the North Feni Ridge (1920 m) and in the South
This paper analyzes the propagation of a cohesive crack through a reinforcement layer and gives a solution that can be used for any specimen and loading condition. Here it faces the case of a reinforced prismatic beam loaded at three points. Reinforcement is represented by means of a free-slip bar bridging the cracked section, anchored at both sides of the
Boundary layers are important in determining the forces on objects in flowing fluids, mixing characteristics, and other phenomena. For example, benthic boundary layers are frequently active resuspension layers that determine bottom turbidity and transniissivity. Traditionally, bo...
A remote sensing unit has been developed to continuously monitor the benthic environment in selected kelp beds in the Santa Barbara Channel area. To characterize their environment, light distribution, temperature and water motion are monitored. Light distribution is determined by a six channel spectral irradiance photometer. Temperature is sensed using a thermistor in a linearizing constant voltage bridge over a
Recruitment of animals into initially dcfaunated sites containing simulated stalks of a marsh grass was studied on an intertidal sandflat. Laboratory flume experiments were used to predict the effects of these structures on near-bed flow, the sediment size-frequency composi- tion, and the patterns and rates of benthic recruitment. The effects of simulated stalks on both rates of fluid transport near
Potential influences of the whole benthic organisms' activity (i.e., coupled faunal and microbial effects) on (58)Co, (51)Cr and (65)Zn diffusion into surface mangrove sediment layers (0-6 cm depth) were evaluated in 36 h experiments. Benthic activity indices (BAI) were proposed, calculated as the relative percent difference between untreated sediments and formaldehyde-treated sediments data in relation to untreated sediments data. Benthic activity was estimated as responsible for 32%-44% of total inventories within sediments, being the chromate anion spiked the less affected radiotracer, while (65)Zn was the most sensitive. Benthic activity was quantitatively evidenced as a control on trace metal diffusion into the sediments, contributing to determine the sediment role as a metal sink. This influence can also affect metal potential bioavailability, considering that recently diffused metals can be more readily available to biological uptake. PMID:23174087
Suzuki, K N; Machado, E C; Machado, W; Bellido, L F; Bellido, A V B; Lopes, R T
The benthic boundary layer, defined as a thin near-bed region that connects the fluid boundary layer and a thin layer below the sediment, has great importance to the biology, chemistry, geology and physics of the oceans. In this region, the biological and chemical exchange processes are highly coupled with hydrodynamic processes. Understanding the effect of benthic boundary layer on the
A. Goharzadeh; A. Khalili; W. Merzkirch; B. B. Jørgensen
This paper provides an overview of interactions between contaminated sediments and bethic invertebrates in marine and freshwater systems using selected examples from the available literature. Impacts on the benthic community (e.g., acute toxicity, morphological and genetic changes in the Chironomidae and Oligochaeta, and induction of carcinogenesis) and changes in community structure are discussed. Processes by which benthic organisms transfer contaminants
We assessed the influence of benthic communities on sediment properties in large defaunation experiments in replicated 16 m2 plots on a tidal flat in the Westerschelde estuary (SW Netherlands). We compared microphytobenthos and benthic macrofauna recovery and recolonisation between control and defaunated sediments during 8 mo following the defaunation, focussing on how the temporal scale of biological responses interact with
F. Montserrat Trotsenburg; C. Van Colen; S. Degraer; T. Ysebaert; P. M. J. Herman
We examined the impact of a 1:3 year return period flood on benthic and pelagic coupling in the river-dominated sub-tropical Brunswick Estuary. The flood had a significant impact on the study site flushing it with freshwater, reducing the flushing time 0.6 days, increasing nutrient concentrations in the water column and scouring the sediment surface. In the three weeks post-flood the benthic and pelagic systems alternated between being coupled and un-coupled via dissolved, particulate and living material pathways. Immediately post-flood benthic and pelagic coupling via the deposition of phyto-detritus and viable algal cells was reduced due to the scouring of the top sediment layers, and benthic respiration and productivity and NH4+ effluxes all decreased correspondingly. In contrast, benthic and pelagic coupling was enhanced via the uptake and denitrification of NO3- due to elevated NO3- concentrations in the water column. Some of the NO3- consumed by the sediments may have also been converted to DON. Two weeks post-flood benthic and pelagic coupling was significantly enhanced via the deposition of phyto-detritus and viable algal cells associated with a phytoplankton bloom in the water column. This increased supply of phyto-detritus and viable algal cells rapidly increased benthic respiration and productivity and NH4+ efflux. The depletion of water column DIN by the phytoplankton bloom resulted in a de-coupling of the benthic and pelagic systems via the uptake and denitrification of NO3-. However, benthic and pelagic coupling was enhanced via the uptake of NH4+ by benthic microalgae. Three weeks post-flood the phytoplankton bloom had collapsed and the coupling between the benthic and pelagic systems via the deposition of phyto-detritus and living algal cells had diminished. Again benthic and pelagic coupling was enhanced via the uptake and denitrification of NO3- due to elevated NO3- concentrations in the water column associated with the recycling of bloom material. Overall the sediments became less heterotrophic (increasing benthic productivity/respiration ratio) following the flood. Floods can cause rapid and complex changes in the coupling between benthic and pelagic systems in sub-tropical estuaries.
The flux of dissolved reactive phosphate from Potomac riverine and estuarine sediments is controlled by processes occurring at the water-sediment interface and within surficial sediment. In situ benthic fluxes (0.1 to 2.0 mmoles m-2 day-1) are generally five to ten times higher than calculated diffusive fluxes (0.020 to 0.30 mmoles m-2 day-1). The discrepancy between the two flux estimates is greatest in the transition zone (river mile 50 to 70) and is attributd to macrofaunal irrigation. Both in situ and diffusive fluxes of dissolved reactive phosphate from Potomac tidal river sediments are low while those from anoxic lower estuarine sediments are high. The net accumulation rate of phosphorus in benthic sediment exhibits an inverse pattern. Thus a large fraction of phosphorus is retained by Potomac tidal river sediments, which contain a surficial oxidized layer and oligochaete worms tolerant of low oxygen conditions, and a large fraction of phosphorus is released from anoxic lower estuary sediments. Tidal river sediment pore waters are in equilibrium with amorphous Fe (OH)3 while lower estuary pore waters are significantly undersaturated with respect to this phase. Benthic regeneration of dissolved reactive phosphorus is sufficient to supply all the phosphorus requirements for net primary production in the lower tidal river and transition-zone waters of the Potomac River Estuary. Benthic regeneration supplies approximately 25% as much phosphorus as inputs from sewage treatment plants and 10% of all phosphorus inputs to the tidal Potomac River. When all available point source phosphorus data are put into a steady-state conservation of mass model and reasonable coefficients for uptake of dissolved phosphorus, remineralization of particulate phosphorus, and sedimentation of particulate phosphorus are used in the model, a reasonably accurate simulation of dissolved and particulate phosphorus in the water column is obtained for the summer of 1980. ?? 1982 Dr W. Junk Publishers.
Based upon the composition of the dominant species of benthic foraminifers in the bottom sediments sampled at 50 sampling stations in the White Sea, their six assemblages (communities) were defined and mapped. The ranges of these communities depend on the environmental factors determined by the bathymetric, latitudinal, and circum-continental sea zonalities, the sea currents, the bottom upwellings, the continental runoff, the productivity of the waters, and the CaCO3 content in the near-bottom water layers and bottom sediments.
In this study, we used the fact that bacteria are able to cleave a fluorogenic substrate analog (l-leucine-7-amido-4-methylcoumarin) to determine the maximal ectoproteolytic activities (Vm) and affinities (Km) of natural benthic microbial communities by the multiconcentration kinetic method. This investigation was performed during the winter and summer of 1997 with a set of 36 samples of near-bottom water and sediment collected from a coastal area and an offshore area in the western part of the Gulf of Lions. The existence of biphasic microbial ectoproteolysis was statistically confirmed for both the near-bottom water and the sediment, regardless of the spatial and seasonal conditions. Globally, 72.2% of the entire set of bacterial consortia collected at the water-sediment boundary layer showed biphasic microbial kinetics. A specific estimator of the biphasicity indicated that deep benthic bacterial consortia responded better with episodic nutrient supplies than shallower benthic bacterial consortia responded.
The benthic macroinvertebrate fauna of New York Bight generally resemble the fauna common to most of the Middle Atlantic Bight and show considerable spatial and temporal heterogeneity in numbers of individuals, species richness, and diversity. The relativ...
J. B. Pearce D. J. Radosh J. V. Caracciolo F. W. Steimle
Field experiments were conducted testing the effects of synthetic fabric barriers on benthic macroinvertebrates in Eau Galle Reservoir, Wisconsin, Lake Guntersville, Alabama, and ponds at the Lewisville Aquatic Ecosystem Research Facility of the Corps of ...
Scientists at EPA's National Health and Environmental Effects Research Laboratory, Western Ecology Division (WED) have been studying seafloor (benthic) habitats in Yaquina estuary for several years. Those studies were conducted as parts of several research projects, including: e...
Abstract The suitability of total carbonate production,instead of oxygen consumption,as a measure,of benthic respiration has been investigated. In situ fluxes of total carbonate, oxygen, calcium, total alkalinity, nutrients, and sulfide across the sediment-water interface were measured in diver- operated benthic flux chambers. Two chambers,were run in parallel to test the influence of oxygen and pH levels on total carbonate production.
LEIF G. ANDERSON; PER O. J. HALL; ÅKE IVERFELDT; MICHIEL M. RUTGERS VAN DER LOEFF; BJØRN SUNDBY; STIG F. G. WESTERLUND
The discovery that foraminifera are able to use nitrate instead of oxygen as energy source for their metabolism has challenged our understanding of nitrogen cycling in the ocean. It was evident before that only prokaryotes and fungi are able to denitrify. Rate estimates of foraminiferal denitrification were very sparse on a regional scale. Here, we present estimates of benthic foraminiferal denitrification rates from six stations at intermediate water depths in and below the Peruvian oxygen minimum zone (OMZ). Foraminiferal denitrification rates were calculated from abundance and assemblage composition of the total living fauna in both, surface and subsurface sediments, as well as from individual species specific denitrification rates. A comparison with total benthic denitrification rates as inferred by biogeochemical models revealed that benthic foraminifera account for the total denitrification on the shelf between 80 and 250 m water depth. They are still important denitrifiers in the centre of the OMZ around 320 m (29-56% of the benthic denitrification) but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (3-7% of total benthic denitrification). Furthermore, foraminiferal denitrification was compared to the total benthic nitrate loss measured during benthic chamber experiments. Foraminiferal denitrification contributes 1 to 50% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates ranged from 0.01 to 1.3 mmol m-2 d-1. Furthermore we show that the amount of nitrate stored in living benthic foraminifera (3 to 705 µmol L-1) can be higher by three orders of magnitude as compared to the ambient pore waters in near surface sediments sustaining an important nitrate reservoir in Peruvian OMZ sediments. The substantial contribution of foraminiferal nitrate respiration to total benthic nitrate loss at the Peruvian margin, which is one of the main nitrate sink regions in the world oceans, underpins the importance of previously underestimated role of benthic foraminifera in global biochemical cycles.
??In freshwater ecosystems production of both pelagic and benthic microalgae tends to be limited by phosphorus and light. However, the availability of these resources to pelagic and benthic communities differs due to differences in habitat structure. In a well mixed epilimnion individual phytoplankton cells should receive similar light intensities and nutrient concentrations per unit time. Benthic microalgae colonize substrates forming
Sabine Flöder; Anja Combüchen; Annika Pasternak; Helmut Hillebrand
Natural alkalinity generation by microbial sulphate reduction in acidic lakes is usually inhibited by the low pH and a low\\u000a primary production which results in a lack of suitable organic carbon sources. In some acidic mining lakes mass developments\\u000a of filamentous benthic algae occur. The effects of this periphyton layer on the biogeochemistry of the sedimentwater interface\\u000a were investigated by
Matthias Koschorreck; Andreas Kleeberg; Peter Herzsprung; Katrin Wendt-Potthoff
Elevated levels of nutrients in Florida springs and spring-run streams, principally nitrate, are becoming increasingly linked to the proliferation of benthic algal populations. Changes include increased algal abundance (as biomass, cell density, and/or ch...
Abstract Spatial and temporal distribution of benthic communities around the Strait of Istanbul (Bosphorus) and the effect of lower layer discharge on these communities have been evaluated during studies between February-December 1999. Mytilus galloprovincialis was the dominant species with fasies at the Black Sea station that is not affected by the strait lower layer current system. On the other hand, another Black Sea station, influenced by the strait lower layer currents, has a similar biota to the strait stations. Species richness and diversity is highest in the strait than other areas. The dominant species is Maera grossimana. However, the station located at the Black Sea exit of the strait has a different biota, and various groups/species appeared to be dominant. Melinna palmata is the dominant species at the Sea of Marmara during the study period. Low dissolved oxygen values of lower layer and soft substratum of sediment resulted in wide distribution of Melinna palmata, adapted to these conditions. The closer stations to the strait in the Sea of Marmara have higher diversity as a result of hydrodynamic processes. On the other hand, coastal stations with low currents and inputs have lower index values, showing the negative effect of discharges and pollution. PMID:12420963
We have compared 14 different sediment incubation chambers, most of them were used on bottom landers. Measurements of mixing time, pressure gradients at the bottom and Diffusive Boundary Layer thickness (DBL) were used to describe the hydrodynamic properties of the chambers and sedimentwater solute fluxes of silicate (34 replicates) and oxygen (23 replicates) during three subsequently repeated incubation experiments on
A. Tengberg; P. O. J. Hall; U. Andersson; B. Lindén; O. Styrenius; G. Boland; F. de Bovee; B. Carlsson; S. Ceradini; A. Devol; G. Duineveld; J.-U. Friemann; R. N. Glud; A. Khripounoff; J. Leather; P. Linke; L. Lund-Hansen; G. Rowe; P. Santschi; P. de Wilde; U. Witte
Saturated and olefinic hydrocarbons were determined in additional species of benthic marine algae from the Cape Cod (Massachusetts, USA) area (see: Youngblood et al., 1971). The distribution of homologous and isomeric olefins was studied in plants of different age and in morphologically different parts of the same specimen. With two minor exceptions, only normal alkanes and alkenes are present. The
In stratified coastal marine waters hypoxia is a growing problem affecting bottom-dwelling animals Earlier studies suggest oxygen concentrations of about 2 mlll (Rosenberg 1980) as the lower tolerance limit for many benthic species in coastal areas. We exposed several conspicuous infaunal species on the NE Atlantic continental shelf, contained within their sediment habitat, to gradually reduced oxygen concentrations. Tolerance to
Rutger Rosenberg; Birthe Hellman; Birgitta Johansson
Eighteen types of benthic foraminifer communities inhabiting depths of 0-200 m are described for the Persian Gulf including the analysis of 269 sampling sites. The species area is mostly localized by the geographical position and bathymetrical features, including the water masses advection, the upwelling, the river discharge, and the concentrations of CaCo3 and Corg in the bottom sediments.
Synthesis of published research on the responses of stream benthic macroinvertebrates to fire in western United States indicates a consistent pattern of response that can guide resource management and future research. Direct effects of fire generally are minor or indiscernible. Indirect effects, resulting primarily from increased rates of runoff and channel alteration, have the greatest impacts on macroinvertebrate community metrics
A field-oriented technique for halving benthic invertebrate samples, the sieve sample splitter, was used to expedite a fish food survey of the Suwannee River, Florida. The splitter was most efficient with collections that completely covered the screen and contained high invertebrate densities.
Chemical reactions in marine sediments and the resulting fluxes across the sediment-water interface influence the global carbon cycle and the pH of the sea and affect the abundance of CaCO3 and opal-forming plankton in the ocean. On very long timescales these diagenetic reactions control carbon burial in sedimentary rocks and the oxygen content of the atmosphere. Sedimentary deposits that remain after diagenesis are the geochemical artifacts used for interpreting past changes in ocean circulation, biogeochemical cycles, and climate. This chapter is about the processes of diagenesis and burial of the chemical elements that make up the bulk of the particulate matter that reaches the seafloor (organic matter, CaCO3, SiO2, Fe, Mn, and aluminosilicates).Understanding of sediment diagenesis and benthic fluxes has evolved with advances in both experimental methods and modeling. Measurements of chemical concentrations in sediments, their associated pore waters and fluxes at the sediment-water interface have been used to identify the most important reactions. Because transport in pore waters is usually by molecular diffusion, this medium is conducive to interpretation by models of heterogeneous chemical equilibrium and kinetics. Large chemical changes and manageable transport mechanisms have led to elegant models of sediment diagenesis and great advances in understanding of diagenetic processes.We shall see, though, that the environment does not yield totally to simple models of chemical equilibrium and chemical kinetics, and laboratory determined constants often cannot explain the field observations. For example, organic matter degradation rate constants determined from modeling are so variable that there are essentially no constraints on these values from laboratory experiments. In addition, reaction rates of CaCO3 and opal dissolution determined from modeling pore waters usually cannot be reproduced in laboratory experiments of these reactions. The inability to mechanistically understand reaction kinetics calculated from diagenesis models is an important uncertainty in the field today.Processes believed to be most important in controlling the preservation of organic matter have evolved from a focus on the lability of the substrate to the protective mechanisms of mineral-organic matter interactions. The specific electron acceptor is not particularly important during very early diagenesis, but the importance of oxygen to the degradation of organic matter during later stages of diagenesis has been clarified by the study of diagenesis in turbidites deposited on the ocean floor during glacial periods.Evolution of thinking about the importance of reactions between seawater and detrital clay minerals has come full circle since the mid-1960s. "Reverse weathering" reactions were hypothesized in very early chemical equilibrium (Sillen, 1961) and mass-balance ( Mackenzie and Garrels, 1966) models of the oceans. Subsequent observations that marine clay minerals generally resemble those weathered from adjacent land and the discovery of hydrothermal circulation put these ideas on the back burner. Recent studies of silicate and aluminum diagenesis, however, have rekindled awareness of this process, and it is back in the minds of geochemists as a potentially important process for closing the marine mass balance of some elements.
The discovery that foraminifera are able to use nitrate instead of oxygen as an electron acceptor for respiration has challenged our understanding of nitrogen cycling in the ocean. It was thought before that only prokaryotes and some fungi are able to denitrify. Rate estimates of foraminiferal denitrification have been very sparse and limited to specific regions in the oceans, not comparing stations along a transect of a certain region. Here, we present estimates of benthic foraminiferal denitrification rates from six stations at intermediate water depths in and below the Peruvian oxygen minimum zone (OMZ). Foraminiferal denitrification rates were calculated from abundance and assemblage composition of the total living fauna in both surface and subsurface sediments, as well as from individual species specific denitrification rates. A comparison with total benthic denitrification rates as inferred by biogeochemical models revealed that benthic foraminifera probably account for the total denitrification in shelf sediments between 80 and 250 m water depth. The estimations also imply that foraminifera are still important denitrifiers in the centre of the OMZ around 320 m (29-50% of the benthic denitrification), but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (2-6% of total benthic denitrification). Furthermore, foraminiferal denitrification has been compared to the total benthic nitrate loss measured during benthic chamber experiments. The estimated foraminiferal denitrification rates contribute 2 to 46% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates range from 0.01 to 1.3 mmol m-2 d-1. Furthermore we show that the amount of nitrate stored in living benthic foraminifera (3 to 3955 ?mol L-1) can be higher by three orders of magnitude as compared to the ambient pore waters in near-surface sediments sustaining an important nitrate reservoir in Peruvian OMZ sediments. The substantial contribution of foraminiferal nitrate respiration to total benthic nitrate loss at the Peruvian margin, which is one of the main nitrate sink regions in the world ocean, underpins the importance of the previously underestimated role of benthic foraminifera in global biogeochemical cycles.
As part of the environmental impact assessment studies for polymetallic nodule mining, the effect of simulated "benthic disturbance" caused by a benthic hydraulic disturber was studied in the Central Indian Basin (CIB). We have compared the abundance and distribution of meiofauna, macrofauna, total counts of bacteria (TC) and cultivable bacteria in the sediments, retrieved from depths of 5000-5300 m, using box corer, before and after disturbance. Nine box core samples each in pre- and post-disturbance stages, were analyzed for labile organic matter (LOM constituted by carbohydrates, protein and lipids), total organic carbon (TOC), ATP and sediment enzymes, phosphatase and lipase. Immediately after the benthic disturbance, (within 10 days), we observed a decrease in meiofauna, macrofauna and bacterial numbers, accompanied by a decrease in LOM, ATP and lipase activity, indicating importance of quality food for the deep-sea benthos. On the other hand, there was an increase in TOC, phosphatase activity and cultivable bacteria, suggesting beneficial effect of disturbance. The results show that a benthic disturbance caused by a hydraulic device may have mixed effects, such as bringing up nutrients from the subsurface layers on one hand and blanketing the bottom by the discharged sediment plume resulting in a decrease in the number of benthos on the other hand. The distinct change in nutrient characteristics of the bottom sediments caused by the disturbance which is probably comparable to a magnified bioturbation process, can be used as an indicator of benthic disturbance.
Raghukumar, Chandralata; Bharathi, P. A. Loka; Ansari, Z. A.; Nair, Shanta; Ingole, B.; Sheelu, G.; Mohandass, C.; Nagender Nath, B.; Rodrigues, Nimi
Chemosynthetic benthic communities, which live symbiotically with microbes capable of metabolizing nutrients dissolved in water seeping out of the seafloor, are widespread along the Cascadia subduction zone. These seeps and vents are therefore indicative of one mode of fluid migration out of the subduction zone sediments. The authors have used deep-towed seismic methods, including hydrophones mounted on Alvin, to examine the detailed geologic structure under two of these vent sites. At one of the sites, located on a seaward dipping thrust zone, the benthic communities are associated with a disruption of the subsurface acoustic layering in the thrust zone. It appears that at this site, dewatering is occurring along fractures in the disrupted sediments which connect to permeable layers in the undeformed sediments and not along the main thrust fault. The other site is located near the top of a ridge which has been uplifted by thrusting along a landward dipping thrust. Most of the benthic communities are found to exist at the outcrop of a steeply dipping unconformity between recent slope-basin sediments and the older uplifted sediments, with the unconformity serving as the fluid pathway. Underlying this unconformity at the most active dewatering location is a complexly deformed structure which appears to enhance the flow of fluid to the unconformity. The source of the fluids could be the older uplifted sediments or the recent slope-basin turbidites. In either case the source is shallow, less than about 1 km.
Lewis, B.T.R. (Univ. of Washington, Seattle (United States)); Cochrane, G.C. (Geological Survey, Menlo Park, CA (United States))
Benthic species of algae and cyanobacteria (i.e., those that grow on surfaces), may provide potential advantages over planktonic species for some commercial-scale biotechnological applications. A multitude of different designs of photobioreactor (PBR) are available for growing planktonic species but to date there has been little research on PBR for benthic algae or cyanobacteria. One notable advantage of some benthic cyanobacterial species is that during their growth cycle they become positively buoyant, detach from the growth surface and form floating mats. This 'self-harvesting' capability could be advantageous in commercial PBRs as it would greatly reduce dewatering costs. In this study we compared the growth rates and efficiency of 'self-harvesting' among three species of benthic cyanobacteria; Phormidium autumnale; Phormidium murrayi and Planktothrix sp.. Phormidium autumnale produced the greatest biomass and formed cohesive mats once detached. Using this strain and an optimised MLA media, a variety of geometries of benthic PBRs (bPBRs) were trialed. The geometry and composition of growth surface had a marked effect on cyanobacterial growth. The highest biomass was achieved in a bPBR comprising of a vertical polyethylene bag with loops of silicone tubing to provide additional growth surfaces. The productivity achieved in this bPBR was a similar order of magnitude as planktonic species, with the additional advantage that towards the end of the exponential phase the bulk of the biomass detached forming a dense mat at the surface of the medium. PMID:21906375
Accelerator mass spectrometry offers for the first time the opportumity to date hand-picked planktonic (surface-swelling) and benthic (bottom-dwelling) foraminifera from deep sea cores, making it possible to reconstruct temporal changes in the rate of deep ocean ventilation. There is, however, a serious problem in interpreting such results. Bioturbation of the soil zone in the upper has two subtle influences that lead to biases in the results. One involves changes with time in the abundances of the forams in newly deposited sediment. The other concerns dissolution effects on the forams during their residence within the bioturbated layer. Mixing models are presented in this paper that illustrate the effects of these interactions on the /sup 14/C age difference between benthic and planktonic species. 9 references, 12 figures.
Benthic habitats are the different bottom environments as defined by distinct physical, geochemical, and biological characteristics. Remote sensing is increasingly being used to map and monitor the complex dynamics associated with estuarine and nearshore benthic habitats. Advantages of remote sensing technology include both the qualitative benefits derived from a visual overview, and more importantly, the quantitative abilities for systematic assessment and monitoring. Advancements in instrument capabilities and analysis methods are continuing to expand the accuracy and level of effectiveness of the resulting data products. Hyperspectral sensors in particular are rapidly emerging as a more complete solution, especially for the analysis of subsurface shallow aquatic systems. The spectral detail offered by hyperspectral instruments facilitates significant improvements in the capacity to differentiate and classify benthic habitats. This paper reviews two techniques for mapping shallow coastal ecosystems that both combine the retrieval of water optical properties with a linear unmixing model to obtain classifications of the seafloor. Example output using AVIRIS hyperspectral imagery of Kaneohe Bay, Hawaii is employed to demonstrate the application potential of the two approaches and compare their respective results.
Vélez-Reyes, Miguel; Goodman, James A.; Castrodad-Carrau, Alexey; Jiménez-Rodriguez, Luis O.; Hunt, Shawn D.; Arnstrong, Roy
The general objective of the research associated with the Benthic Primary Production Work Unit of Columbia River Estuary Development Program was to determine mechanisms that control the production dynamics and species composition of benthic plant assemblages in the Columbia River Estuary. In particular, the work was concerned with effects of selected physical variables on structural and functional attributes of micro- and macro- vegetation, and on the productivity and biomass of benthic autotrophs on the tidal flats of the estuary.
We examine three radium isotopes (224Ra, 223Ra and 226Ra) as a sediment-water interface tracer in upper Indian River Lagoon. Benthic fluxes are estimated using lagoon budgets, benthic chambers and pore water profiles. The lagoon budget approach estimates range from ~20 dpm\\/m2-d for 224Ra to ~7 dpm\\/ m2-d for 223Ra to zero for 226Ra. Benthic Chamber flux estimates determined over an
J. M. Smoak; P. W. Swarzenski; J. E. Cable; J. B. Martin
Our overall goal is to understand how photosynthetic and photoprotective pigments in benthic plants (primarily benthic microalgae) affect the optical properties (primarily spectral reflectance and fluorescence) of shallow benthic environments. The informa...
Light and dark benthic dissolved organic carbon (DOC) fluxes and sediment characteristics (total organic carbon (TOC), total nitrogen (TN), TOC isotope ratio (?13C), phospholipid fatty acid (PLFA) concentration, and compound-specific ?13C) were measured seasonally in a range of habitats in three warm-temperate Australian estuaries to determine what factors control benthic DOC fluxes. Benthic DOC fluxes were seasonal with the highest
Light and dark benthic dissolved organic carbon (DOC) fluxes and sediment characteristics (total organic carbon (TOC), total nitrogen (TN), TOC isotope ratio (?13C), phospholipid fatty acid (PLFA) concentration, and compound-specific ?13C) were measured seasonally in a range of habitats in three warm-temperate Australian estuaries to determine what factors control benthic DOC fluxes. Benthic DOC fluxes were seasonal with the highest rates generally observed during summer. Most habitats displayed uptake of DOC during the dark and efflux during the light, and were a net source of DOC to the overlying waters over the diel cycle. Macrophyte habitats (seagrass and macroalgae) had the highest benthic fluxes of DOC (up to 50 mmol C m-2 d-1). Organic matter supply to the sediment was dominated by in situ production, and both quantity and source exerted control over benthic DOC fluxes. DOC flux was tightly coupled to bacteria and algal PLFA concentrations during summer, and algal PLFA concentrations during winter, indicating a strong influence of microbial interactions on benthic DOC flux and a temperature-related decoupling of algae and bacteria under cooler conditions. Estimates of the global estuarine benthic DOC flux indicate that these areas are a significant source of DOC to the ocean (1-41 Tg C yr -1). Inclusion of macrophyte, salt marsh, mangrove, and intertidal benthic DOC flux estimates resulted in a higher global continental margin benthic DOC flux (106-416 Tg C yr -1) than the previous estimate (90 Tg C yr-1).
The long-term goal of this research is to gain an understanding of the nature and significance of fluorescence and reflectance characteristics of benthic marine organisms in general, and coral reef cnidarians in particular. We wish to determine both how b...
Benthic macrofaunal sampling protocols in the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) are to collect 30 to 50 random benthic macrofauna [defined as animals retained on a 0.5 mm (East and Gulf Coasts, USA) or a 1.0 mm mesh siev...
Low dissolved oxygen (hypoxia and\\/or anoxia) has become a major cause of change to the benthic component of ecosystems around the world. We present the response of a benthic community to hypoxia in organically enriched environments in Korean coastal waters. Disturbances due to low dissolved oxygen (DO), and organic enrichment altered community dynamics, result in defaunation during summer hypoxia with
Hyun-Sig Lim; Robert J. Diaz; Jae-Sang Hong; Linda C. Schaffner
In soft sediments, Dreissena spp. create firm substrate in the form of aggregates of living mussels (druses) that roll free on the sediments. Druses provide physical structure which increases habitat heterogeneity, and the mussels increase benthic organic matter through the production of pseudofeces and feces. Descriptive and experimental studies were used to determine: 1) whether the density of benthic invertebrates
The benthic body size miniaturization hypothesis states that deep-sea communities are dominated by organisms of smaller body size, although some ¢eld studies have produced contradictory results. Using appropriate sample sets, this study tests this hypothesis by contrasting the benthic communities of the Fladen Ground (North Sea, 150 m) and the Faroe ^Shetland Channel (1600 m). Samples were collected for large
Using radioactively labeled bacteria and photoautotrophs in undisturbed sediment cores, we show that three cooccurring species of benthic copepods feed on different microbial food sources in their natural environment. Specifically, Thompsonula hyaenae feeds on photoautotrophs, Halicyclops coulli feeds on bacteria, and Zausodes arenicolus feeds on both photoautotrophs and bacteria. Species of benthic copepods feed differently from one another in the
Distributions of benthic populations in the Hadley Harbor area, Massachusetts, form the basis for a model study of benthic ecosystems which can be applied to coastal lagoons in temperate and tropical regions. The Hadley Harbor area covers one-third Km2 an...
Coastal lagoons are highly variable and dynamic systems that have been rarely investigated in terms of benthic microbial loop. We present here the results of a comparative study aimed at investigating factors and benthic processes potentially affecting microbial loop functioning in three lagoon systems (Goro, Lesina and Marsala lagoons). The three lagoons were characterised by different geo-morphological, trophic and ecological
Elena Manini; Carla Fiordelmondo; Cristina Gambi; Antonio Pusceddu; Roberto Danovaro
A benthic index for northern Gulf of Mexico estuaries has been developed and successfully validated by the Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) in the Louisianian Province. The benthic index is a useful indicator of estuarine condition that provi...
Benthic Nutrient Flux in a Small Estuary in Northwestern Florida(USA).Gulf and Caribbean Research 18, 15-25, 2006. Benthic nutrient fluxes of ammonium (NH4+), nitrite/nitrate (NO2-+NO3-), phosphate (PO4-), and dissolved silica (DSi) were measured in Escambia Bay, an estuar...
Triclosan (5-chloro-2-[2,4-dichlorophenoxy]phenol) is a relatively new, commonly used antimicrobial compound found in many personal care products. Triclosan is toxic to marine organisms at the micrograms per liter level, can photodegrade to a dioxin, can accumulate in humans, and has been found to be stable in marine sediments for over 30 years. To determine the effects of triclosan on marine benthic communities, intact sediment cores were brought into the laboratory and held under flowing seawater conditions. A 2-cm layer of triclosan-spiked sediment was applied to the surface, and after a two-week exposure the meio- and macrofaunal communities were assessed for differences in composition relative to nonspiked cores. A high triclosan treatment (180?mg/kg dry wt) affected both the meio- and the macrobenthic communities. There were no discernible differences with a low-triclosan treatment (14?mg/kg dry wt). This exposure method is effective for testing the benthic community response to sediment contaminants, but improvements should be made with regard to the amount and method of applying the overlying sediment to prevent smothering of fragile benthic organisms. PMID:23161706
Ho, Kay T; Chariton, Anthony A; Portis, Lisa M; Proestou, Dina; Cantwell, Mark G; Baguley, Jeffrey G; Burgess, Robert M; Simpson, Stuart; Pelletier, Marguerite C; Perron, Monique M; Gunsch, Claudia K; Bik, Holly M; Katz, David; Kamikawa, Anthony
A generalized analytical model for benthic water flux forced by linear surface gravity waves over a series of layered hydrogeologic units is developed by adapting a previous solution for a hydrogeologic unit with an infinite thickness (Case I) to a unit with a finite thickness (Case II) and to a dual-unit system (Case III). The model compares favorably with laboratory observations. The amplitude of wave-forced benthic water flux is shown to be directly proportional to the amplitude of the wave, the permeability of the hydrogeologic unit, and the wave number and inversely proportional to the kinematic viscosity of water. A dimensionless amplitude parameter is introduced and shown to reach a maximum where the product of water depth and the wave number is 1.2. Submarine groundwater discharge (SGD) is a benthic water discharge flux to a marine water body. The Case I model estimates an 11.5-cm/d SGD forced by a wave with a 1 s period and 5-cm amplitude in water that is 0.5-m deep. As this wave propagates into a region with a 0.3-m-thick hydrogeologic unit, with a no-flow bottom boundary, the Case II model estimates a 9.7-cm/d wave-forced SGD. As this wave propagates into a region with a 0.2-m-thick hydrogeologic unit over an infinitely thick, more permeable unit, the Case III quasi-confined model estimates a 15.7-cm/d wave-forced SGD. The quasi-confined model has benthic constituent flux implications in coral reef, karst, and clastic regions. Waves may undermine tracer and seepage meter estimates of SGD at some locations. Copyright 2009 by the American Geophysical Union.
In situ, paired light and dark benthic flux chamber incubations were used to estimate the exchange of nutrients, oxygen and inorganic carbon across the sediment water interface of the South Atlantic Bight (SAB) continental shelf. The results indicate that physically forced non-diffusive pore water transport and benthic primary production (BPP) by sea floor microalgae exert a major influence on
Richard A. Jahnke; James R. Nelson; Roberta L. Marinelli; James E. Eckman
Field-collected living specimens of the benthic foraminifera Haynesina germanica were maintained in the laboratory and fed a naturally occurring motile benthic diatom assemblage dominated by Pleurosigma angulatum. The extracellular removal of diatom contents was inferred for P. angulatum in controlled experiments. A characteristic pattern of fracturing of the diatom frustule was observed that was directly attributed to foraminiferal feeding\\/sequestration mechanisms.
Heather Anne Austin; William E. N. Austin; David M. Paterson
A microcosm experiment was conducted using a replicated factorial design to determine if a benthic fish modifies the effects of sediment-bound contaminants (diesel fuel and two levels of a Cu, Cr, Pb, Hg and Cd mixture) on saltmarsh benthic primary producers and consumers. The naked goby, Gobiosoma bosc, a burrowing fish that preys on small macrofauna, was added to experimental
J. W. Fleeger; G. Tita; K. R. Carman; R. N. Millward; E. B. Moser; R. J. Portier; R. P. Gambrell
The generally accepted concept that dorsoventral flatness and\\/or small size of benthic stream invertebrates staying on the surface of the bottom substratum allows a current-sheltered life in the boundary layer (Ambühl 1959) is checked by means of the new technique of Laser Doppler Anemometry (LDA). With LDA measurement of flow can be done nearly punctually without any mechanical disturbance. Mapping
Community structure and assembly are determined in part by environmental heterogeneity. While reef-building corals respond negatively to warming (i.e. bleaching events) and ocean acidification (OA), the extent of present-day natural variability in pH on shallow reefs and ecological consequences for benthic assemblages is unknown. We documented high resolution temporal patterns in temperature and pH from three reefs in the central Pacific and examined how these data relate to community development and net accretion rates of early successional benthic organisms. These reefs experienced substantial diel fluctuations in temperature (0.78°C) and pH (>0.2) similar to the magnitude of 'warming' and 'acidification' expected over the next century. Where daily pH within the benthic boundary layer failed to exceed pelagic climatological seasonal lows, net accretion was slower and fleshy, non-calcifying benthic organisms dominated space. Thus, key aspects of coral reef ecosystem structure and function are presently related to natural diurnal variability in pH. PMID:22952785
Price, Nichole N; Martz, Todd R; Brainard, Russell E; Smith, Jennifer E
Community structure and assembly are determined in part by environmental heterogeneity. While reef-building corals respond negatively to warming (i.e. bleaching events) and ocean acidification (OA), the extent of present-day natural variability in pH on shallow reefs and ecological consequences for benthic assemblages is unknown. We documented high resolution temporal patterns in temperature and pH from three reefs in the central Pacific and examined how these data relate to community development and net accretion rates of early successional benthic organisms. These reefs experienced substantial diel fluctuations in temperature (0.78°C) and pH (>0.2) similar to the magnitude of warming and acidification expected over the next century. Where daily pH within the benthic boundary layer failed to exceed pelagic climatological seasonal lows, net accretion was slower and fleshy, non-calcifying benthic organisms dominated space. Thus, key aspects of coral reef ecosystem structure and function are presently related to natural diurnal variability in pH.
Benthic communities provide secondary production for higher trophic levels, and changes in benthic community structure can be a harbinger for associated food web alterations. Benthic communities can be affected by variations in water quality, with low dissolved oxygen reducing benthic abundance and biomass. We quantified the effects of dissolved oxygen and other environmental factors upon changes in density, biomass, and
Rochelle D. Seitz; Daniel M. Dauer; Roberto J. Llansó; W. Christopher Long
The influence of sea squirt aquaculture on benthic-pelagic coupling was evaluated in semi-enclosed Korean coastal waters with an in situ benthic chamber and results show for the first time that suspended sea squirt cultures play an important role in benthic-pelagic coupling in the coastal zone. Measurements of primary production, vertical particulate fluxes, and benthic fluxes were made at two stations, a sea squirt (Halocynthia roretzi) farm (SSF) and an area of organic-matter-enriched sediment in Jinhae Bay. The vertical material fluxes of organic carbon, nitrogen, and biogenic silicate (BSi) were significantly higher at SSF than in Jinhae Bay, indicating massive biodeposits in the surface sediments at SSF. The organic carbon oxidation rates (Cox) were estimated after correction for CaCO3 dissolution. The average Cox at SSF (204 mmol C m-2 d-1) was significantly higher than that in the organic-enriched Jinhae Bay sediment (77 mmol C m-2 d-1). The organic carbon burial fluxes were determined using vertical profiles of organic carbon of up to 30 cm and the sedimentation rate calculated from the excess 210Pb distribution. At both stations, 95% of the settled organic carbon was oxidized and only 5% was buried in the deep sediment layer. The benthic fluxes of dissolved inorganic nitrogen and phosphate at SSF were 2-12 times higher than in Jinhae Bay, corresponding to 85%, and 270%, respectively, of the requirements for primary production.
Lee, Jae Seong; Kim, Sung-Han; Kim, Yong-Tae; Hong, Sok Jin; Han, Jeong Hee; Hyun, Jung-Ho; Shin, Kyung-Hoon
Continental shelves are hotspots for sedimentary denitrification, and the loss of N through denitrification can limit primary production in ecosystems. Spatial and seasonal trends in sedimentary denitrification and benthic nutrient fluxes are poorly characterized in the highly productive Bering Sea shelf ecosystem. Through the Bering Sea Ecosystem Study (BEST) program, we measured benthic fluxes of N2 and dissolved inorganic nitrogen (DIN: NH4++NO2-+NO3-), the extent of coupled sedimentary nitrification/denitrification, and the water column DIN deficit relative to phosphate, as indicated by a modified N* parameter (N**), on the Bering Sea shelf in the spring and summer 2009-2010. We found that sedimentary denitrification is widespread over the shelf, it is fueled mostly through coupled nitrification/denitrification, the net balance of sedimentary DIN flux is near zero over the shelf, and that the water column DIN deficit varies widely according to season and year. In the summer, N** in the surface layer appeared to be strongly affected by non-Redfieldian uptake of inorganic nutrients by phytoplankton in the spring bloom; in the winter, N** was strongly affected by sedimentary denitrification. Our findings indicate that the estimate of total N loss in Bering Sea shelf sediments should be revised upwards by at least 50% to 5.2-6.2 Tg N y-1. In addition, sediments are not a significant source of remineralized N for primary production over the shelf; hence sedimentary denitrification exacerbates N-limitation of the ecosystem.
Horak, Rachel E. A.; Whitney, Heather; Shull, David H.; Mordy, Calvin W.; Devol, Allan H.
In 2005, Hurricane Katrina produced a distinct, acute ecological disturbance of the benthic invertebrate community of Lake\\u000a Pontchartrain, LA, USA. The bivalve Rangia cuneata and other community dominants were lost from 50% (815 km2) of the lake bottom. The storm surge directly killed benthic organisms and produced salinity stratification that caused episodes\\u000a of detrimental low dissolved oxygen concentration at depths >3.7 m.
Michael A. Poirrier; Zoe Rodriguez del Rey; Elizabeth A. Spalding
species, representing 9 major benthic faunal groups encountered at 200 m depth off the Princess Astrid coast (Lat. 69°54'S; Long. 12°49'E) in the Eastern Antarctica, are described here. Estimated benthic biomass was 68 gm -2 . Echinoderms (35%) followed by sponges (22%), molluscs (15%), ascidians (8%), coelenterates (5%), crustaceans (5%), bryozoans (4%) and annelids (3%) were the major faunal taxa.
Sequence of invasion of estuarine benthic organisms into a man-made pond was followed over a 2-year period. Dominant animals\\u000a established early and developed aMya- Macoma- Nereis association similar to that in nearby estuarine waters. Estimated biomass, faunal abundance, and growth measurements indicate\\u000a that the benthic populations were near maximum levels within the first year, and that a stable association continued
Research of complex systems and problems, entities with many dependencies, is often reductionist. The reductionist approach\\u000a splits systems or problems into different components, and then addresses these components one by one. This approach has been\\u000a used in the study of recruitment and population dynamics of marine benthic (bottom-dwelling) species. Another approach examines\\u000a benthic population dynamics by looking at a small
Jesús Pineda; Nathalie B. Reyns; Victoria R. Starczak
A total of 76 taxa of benthic macroinvertebrates as collected from Ham's Lake, Oklahoma, during 1974 and 1975. The composition\\u000a and density of the benthic assemblage was similar to that of other Oklahoma reservoirs. The number of species and density\\u000a of macroinvertebrates decreased from March to the end of July, 1975 Species diversity and biomass did not change significantly\\u000a with
The latest Paleocene benthic foraminiferal extinction event has been studied in two marlstone successions in the Tethys: at Wadi Nukhl (Egypt) and Torangly (Turkmenistan). Both sections yield a sapropelic layer at the level of the extinction event. At Nukhl, this layer underlies a thin calcareous bed that has also been found in other Middle East upper Paleocene sections. With the onset of anoxia at the Tethyan sea floor, the aerobic and oligotrophic Gavelinella beccariiformis deep-sea community collapsed. Eutrophic-to-mesotrophic and low-oxygen conditions, most likely resulting from enhanced organic carbon fluxes to the sea floor, triggered an 100 200 k.y. repopulation sequence, marked by downslope migration of several neritic communities that were dominated by opportunistic and tolerant taxa. The initial ecosystem restoration was completed when an aerobic and oligotrophic Nuttallides truempyi deep-sea community became established. We suggest that this repopulation mode could be typical for the central Tethys.
Speijer, Robert P.; Schmitz, Birger; van der Zwaan, Gijsbert J.
In this work we evaluated the vertical distribution pattern of benthic infauna during the tidal cycle at one of the most important mudflats of the Tagus estuary. Samples were collected hourly during 24 h periods at four complete tidal cycles, using a corer specifically designed for the study purpose that allowed easy and effective separation of 15 different sediment layers. A particular case of general linear models, the hurdle model, was used to analyse data sets. We found that different species have different distribution and abundance according to sediment layers. Results showed that individuals tend to go deeper into sediment with a lower water column height and that these migrations are more visible during spring tides.
Cardoso, Inês; Granadeiro, José Pedro; Cabral, Henrique
The direct effects of a Virginia trout farm on benthic macroinvertebrates were examined using multiple approaches. Static laboratory tests with the amphipod, Hyallela azteca, were conducted with exposures to water taken from a spring and from effluent both above and below a sedimentation basin. Onsite mesocosms were constructed to expose previously colonized artificial substrates to the same treatments as the laboratory tests. Flat-headed mayflies also were collected from a nearby stream and transported to the mesocosms for a 10-d exposure. There was no significant difference between treatments in the laboratory tests after 20 d, but after 28 d the control was significantly lower than the above-sedimentation basin treatment in one test. In the multispecies field tests, a clear decrease in total invertebrate and Ephemeroptera, Plecoptera, and Trichoptera (EPT) abundance was seen in the effluent treatments compared to spring water treatments. There was, however, a slight improvement in survival in treatment below the sedimentation basin. Only total invertebrate abundance after 21 d produced statistically significant differences. A significant difference was detected between the effluent and the spring treatments in the flat-headed mayfly field test. We suggest that in this study, the effluent alone does not explain the lack of taxa richness in the receiving stream. The main cause of mortality from trout effluents appears to be solids accumulating upon the organisms. Well operated and designed sedimentation basins are expected to, in part, reduce any effects on macroinvertebrates. PMID:19323285
18O 16O and 13C 12C ratios of Miocene benthic foraminifera from a number of Atlantic, Pacific and Indian Ocean DSDP sites (71, 77B, 206, 208, 238, 279, 289, 296, 329, 357 and 366A) have been compiled. These provide a rather detailed history of Miocene deep water especially in the Pacific Ocean. Bottom-water temperatures rose during the early Miocene and then declined rapidly during the middle Miocene. This decline was accompanied by an increase in Antarctic glaciation. Late Miocene bottom temperatures and Antarctic ice volumes are inferred to be similar to today's, but exhibited some fluctuation. The early Miocene ocean was less thermally stratified at intermediate and abyssal depths while the late Miocene deep ocean had a thermal structure generally similar to the modern ocean. Foraminiferal carbon isotope ratios at most of the sites varied quasi-sympathetically throughout the Miocene. These variations must reflect comparable variations in the mean 13C 12C of marine HCO3-. However, the causes of such variations are not yet clear. ?? 1981.
Savin, S. M.; Douglas, R. G.; Keller, G.; Killingley, J. S.; Shaughnessy, L.; Sommer, M. A.; Vincent, E.; Woodruff, F.
Recently documented changes to benthic communities in the lower Great Lakes have created concerns about the status of benthic macroinvertebrates in Lake Superior. This lakewide study was conducted to ascertain their status in U.S. nearshore waters of Lake Superior. Benthic macroinvertebrates were collected from 27 sites representing the U.S. nearshore waters (20 to 110 m) of Lake Superior in 1994, 2000, and 2003. No significant differences in total benthic macroinvertebrate abundance, or abundances of oligochaetes, clams or chironomids were detected between years. Abundance of the amphipod Diporeia spp. was lower in 2000 than in 1994 and 2003. The oligochaete trophic index, a measure of relative abundance of species tolerant of varying degrees of organic enrichment, did not differ between years. Diporeia exhibited a bimodal depth distribution, with peaks in abundance at depths of 30 to 40 and 60 to 70 m. Oligochaetes were most abundant at 50 to 60 m depth, clams between 30 and 70 m, and chironomids at less than 30 m, with a secondary peak at 50 to 60 m. The spatial and temporal variability observed in Lake Superior benthic macroinvertebrate communities has implications for sampling design for environmental assessment. This abstract does not necessarily reflect USEPA policy.
Porewater concentration gradients indicate relatively large benthic fluxes of Pb from sediments in the San Francisco Bay estuary. Gradients in total dissolved (<0.45 [mu]m) Pb concentrations in sediment porewaters, which range from 0.07-19.2 nM, parallel gradients in ammonia and dissolved Fe in sediment cores from the bay. Corresponding Fickian diffusive fluxes range from 2.6 [times] 10[sup [minus]9] moles m[sup [minus]2] d[sup [minus]1] to 3.1 [times] 10[sup [minus]8] moles m[sup [minus]2] d[sup [minus]1] in anoxic surface (<2 cm) sediments along the periphery of the estuary. These indicate the net diffusive benthic flux of Pb from sediments in San Francisco Bay (3-31 moles d[sup [minus]1]) is at least an order of magnitude greater than the fluvial input of dissolved Pb to the estuary (0.2 moles d[sup [minus]1]) during low flow periods. Moreover, estimates of the total benthic Pb flux, which were based on HAMMOND et al. (1985) irrigation benthic flux model, are two- to six-fold greater (6-186 moles d[sup [minus]1]) than the estimates of diffusive fluxes. Therefore, the total benthic flux of Pb from the bay's sediments may be within the order of magnitude of the total anthropogenic flux of Pb to the San Francisco Bay estuary (965-8,410 moles d[sup [minus]1]).
Rivera-Duarte, I.; Flegal, A.R. (Univ. of California, Santa Cruz, CA (United States))
Description: The negative effect of turbidity on the reactive distance of ... and field observations suggest that benthic feeding by salmonids in flowing water affects the ... Two experiments were conducted in a laboratory stream to quantify benthic ...
The spatial patterns of subtidal benthic invertebrates and physical-chemical variables in the nearshore Gulf of Maine (Acadian Biogeographic Province) were studied to provide information needed to calibrate benthic indices of environmental condition, determine physical-chemical f...
Benthic invertebrate indices have commonly been utilized to assess benthic invertebrate communities. These indices have been constructed using different techniques, but have shown different levels of application success. For example, the EMAP Virginian Province Index did not pe...
Coastal estuaries of Oregon, USA, typically support relatively large accumulations of benthic green macroalgae (BGM) during the summer/early fall growing season. This raises questions regarding possible (positive and negative) effects on eelgrass and benthic epifauna and infauna...
To establish and define relationships between benthic storms (periods of intense currents and bottom resuspension) sediment distribution patterns, and the intensity of eddy kinetic energy observed in surface or bottom waters. A correlation between benthic...
Benthic macroinvertebrate assemblages have been used as indicators of ecological condition because their responses integrate localized environmental conditions of the sediments and overlying water. Assemblages of benthic invertebrates in the near coastal region are of particular...
Streams and rivers in the California Central Valley Ecoregion have been substantially modified by human activities. This study examines distributional patterns of benthic diatom assemblages in relation to environmental characteristics in streams and rivers of this region. Benthic...
Benthic macroinvertebrate assemblages are useful indicators of ecological condition for aquatic systems. This study was conducted to characterize benthic communities of three large reservoirs on the Missouri River. The information collected will be useful in development of samp...
Remotely operated vehicles (ROVs) have revolutionized oceanographic research, supplementing traditional technologies of acoustics and trawling as tools which assess animal diversity, distribution and abundance. Video equipment deployed on ROVs enable quantitative video transects (QVTs) to be recorded from ocean habitats, providing high-resolution imagery on the scale of individual organisms and their associated habitat. Currently, the manual method employed by trained scientists analyzing QVTs is labor-intensive and costly, limiting the amount of data analyzed from ROV dives. An automated system for detecting organisms and identifying objects visible in video would address these concerns. Automated event detection (scene segmentation) is a step towards an automated analytical system for QVTs. In the work presented here, video frames are processed with a neuromorphic selective-attention algorithm. The candidate locations identified by the attention selection module are subject to a number of parameters. These parameters, combined with successful tracking over several frames, determine whether detected events are deemed "interesting" or "boring". "Interesting" events are marked in the video frames for subsequent identification and processing. As reported previously for mid-water QVTs, the system agrees with professional annotations 80% of the time. Poor contrast of small translucent animals in conjunction with the presence of debris ("marine snow") complicates automated event detection. While the visual characteristics of the seafloor (benthic) habitat are very different from the mid-water environment, the system yields a 92% correlation of detected animals on the seafloor compared with professional annotations. We present results detailing the comparison between a) automated detection and b) professional detection and classification, and we outline plans for future development of automated analysis.
Edgington, D. R.; Kerkez, I.; Oliver, D.; Kuhnz, L.; Cline, D. E.; Walther, D.; Itti, L.
Three-dimensional structure of the near-bottom density field was observed with a towed yo-yoing profiler and a fixed current\\/temperature measuring array on the Hatteras abyssal plain. A great variety of structures were seen. Immediately above the bottom a well-mixed bottom layer extends vertically 5-60 m, with less than 1 m°C potential temperature change. This mixed layer is often capped by a
In the western basin of Lake Erie, benthic invertebrate abundance and community composition have changed dramatically over the past five decades, as have abundance and growth of yellow perch Perca flavescens. Before 1950, large benthic invertebrates dominated the benthic community of the western basin. Yellow perch readily consumed Hexagenia larvae, caddisfly larvae, amphipods, chironomids, and zooplankton. From 1960 through 1980,
ABSTRACT. Zebra mussel, Dreissena polymorpha (Pallas), proliferation in Saginaw Bay, Lake Huron is associated with increased water clarity and increased light levels on benthic substrata in the littoral zone. We hypothesized that the filtering activities of Dreissena and associated increases in light penetra- tion should affect the structure and function of benthic algae in the bay. Monthly quantitative benthic algal
Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic
Andreas F. Haas; Craig E. Nelson; Linda Wegley Kelly; Craig A. Carlson; Forest Rohwer; James J. Leichter; Alex Wyatt; Jennifer E. Smith
The abundance and productivity of benthic microalgae in coral reef sediments are poorly known compared with other, more conspicuous (e.g. coral zooxanthellae, macroalgae) primary producers of coral reef habitats. A survey of the distribution, biomass, and productivity of benthic microalgae on a platform reef flat and in a cross-shelf transect in the southern Great Barrier Reef indicated that benthic microalgae
C. A. Heil; K. Chaston; A. Jones; P. Bird; B. Longstaff; S. Costanzo; W. C. Dennison
Commercial fishing is one of the most important human impacts on the marine benthic environment. One such impact is through disturbance to benthic habitats as fishing gear (trawls and dredges) are dragged across the seafloor. While the direct effects of such an impact on benthic communities appear obvious, the magnitude of the effects has been very difficult to evaluate. Experimental
S. F. Thrush; J. E. Hewitt; V. J. Cummings; P. K. Dayton; M. Cryer; S. J. Turner; G. A. Funnell; R. G. Budd; C. J. Milburn; M. R. Wilkinson
The Chesapeake Bay Benthic Index of Biotic Integrity (B-161) and the Environmental Monitoring and Assessment Program's Virginian Province Benthic Index (EMAP-VP BI) were applied to 294 sampling events in Chesapeake Bay and the results were compared. These benthic indices are inte...
By applying discriminant analysis to benthic macroinvertebrate data to produce a benthic index, we have developed an indicator of benthic condition for northern Gulf of Mexico estuaries. The data used were collected by the U.S. Environmental Protection Agency's (USEPA) Environmen...
The Chesapeake Benthic Index of Biotic Integrity (B-IBI) and the EMAP-VP Benthic Index were applied to samples from 239 sites in Chesapeake Bay. The B-IBI weights several community measures equally and uses a simple scoring system while the EMAP-VP Benthic Index uses discriminant...
Often when various estuarine benthic indices disagree in their assessments of benthic condition, they are reflecting different aspects of benthic condition. We describe a process to screen indices for associations and, after identifying candidate metrics, evaluate metrics individually against the indices. We utilize radar plots as a multi-metric visualization tool, and conditional probability plots and receiver operating characteristic curves to
Sandra J. Benyi; Jeffrey W. Hollister; John A. Kiddon; Henry A. Walker
This study was conducted to examine how a low-head dam removal (partial removal) could affect benthic macroinvertebrate communities in a stream. Benthic macroinvertebrates and substrates were seasonally sampled before and after dam removal (March 2006April 2007). Benthic macroinvertebrates and substrates were quantitatively sampled from immediately upstream (upper: pool) and downstream (lower: riffle) sites, the location of the dam itself (middle),
This study was conducted to examine how a low-head dam removal (partial removal) could affect benthic macroinvertebrate communities in a stream. Benthic macroinvertebrates and substrates were seasonally sampled before and after dam removal (March 2006April 2007). Benthic macroinvertebrates and substrates were quantitatively sampled from immediately upstream (upper: pool) and downstream (lower: riffle) sites, the location of the dam itself (middle),
The brine discharge from seawater desalination has a strong impact on marine community, especially benthic community near brine outlet. The aim of this study is to examine the effect of brine discharge over soft bottom benthic community and changes of sediment quality by periodic brine exposure and water circulation confinement using small-scale benthic microcosms. Transparent acrylic cylinder (1?m in length
Numerous investigators characterize benthic flux and submarine groundwater discharge (SGD) using a geochemical conceptual model that relies on the estimation of tracer fluxes into and out of a control volume. (Benthic flux is the rate of flow across the bed of any water body, per unit area of bed. Benthic flux is a vector that includes both discharge and recharge components. SGD is a benthic water discharge flux to a marine water body.) For the geochemical approach, benthic discharge flux or SGD is estimated by summing the flux of tracer into or out of the control volume---a water body or portion of a water body---and deducing that tracer deficiency within the control volume must be explained by SGD. Typically, estimated or measured fluxes include advection and mixing in surface-water, diffusion, evasion across the air-water interface, production, and decay. The geochemical model, however, does not account for fluxes that do not transport tracer. For example, investigators found equivalent (<10 dpm per liter) radon activities in both surface water, and in pore fluid within the upper 30 cm of sediment in the Indian River Lagoon, Florida, in June and July 2003. At this location, a surface-gravity wave with a five-centimeter amplitude and one-second period in 0.5 m of water forced a 12-cm-per-day SGD. The radon tracer technique may not characterize SGD forced by the one-second wave due to the time scale of the wave, the absence of a radon activity gradient between bed medium and surface water, and the <30 cm depth to which the wave affects the flow field within the porous medium. A new geophysical conceptual model for benthic flux is proposed. The model parses benthic flux into components driven by individual forcing mechanisms. The model recognizes that benthic flux components may interact in a constructive or destructive manner, such that benthic flux generated by multiple forcing mechanisms at the same location may not be equivalent to the linear sum of benthic flux generated by single forcing mechanisms. Restated: the whole may be different than the sum of the parts. Individual forcing mechanisms that drive benthic flux components include: the terrestrial hydraulic gradient, tide, surface gravity waves, density gradients, chemical gradients, diagenesis, bio-irrigation, sea-level rise, and bedform-current interaction. Other forcing mechanisms surely exist. Although many of these component forcing mechanisms can be characterized, component interactions are not fully understood. Differences exist between the geophysical and geochemical conceptual models. The geochemical model integrates the contribution of forcing mechanisms over both the control volume and duration of study. Because a tracer can not characterize a flux that does not transport the tracer, and because the time-scale or spatial-scale of some SGD forcing mechanisms is not resolved by certain tracers, the geochemical model may not describe all SGD to a water body. Restated: the geochemical model may only describe the component of SGD that transports the tracer. Some components of the geophysical model may be difficult or impossible to measure in natural systems. Interaction between specific components of the geophysical model may be intractable.
Many types of indices have been developed to assess benthic invertebrate community condition, but there have been few studies evaluating the relative performance of different index approaches. Here we calibrate and compare the performance of five indices: the Benthic Response Index (BRI), Benthic Quality Index (BQI), Relative Benthic Index (RBI), River Invertebrate Prediction and Classification System (RIVPACS), and the Index
J. Ananda Ranasinghe; Stephen B. Weisberg; Robert W. Smith; David E. Montagne; Bruce Thompson; James M. Oakden; David D. Huff; Donald B. Cadien; Ronald G. Velarde; Kerry J. Ritter
Experience gained while diving has made it possible to view forests of giant kelp as communities of plants existing in, and adapted to conditions in three water motion regions: the boundary layer and turf region; the surge zone; and the current zone. Duri...
Two closely located islands on the west coast of South Africa support widely different benthic communities. The biota at Malgas Island is dominated by seaweeds and by rock lobsters that consume settling mussels, thereby preventing the establishment of the mussels. They also prey on whelks, although one species, Burnupena papyracea, is protected from predation by a commensal bryozoan that covers
Investigations were completed to quantify the amount of phosphorus (P) available for release from the sediment of Lake Waco, Texas, as part of the Lake Waco Comprehensive Lake Management Study. Sediment oxygen demand and benthic nutrient flux measurements were obtained using an in situ chamber and an in situ nutrient analyzer available from Systea Inc. Sediment samples were also collected
The benthic macroinvertebrates in the Kenya waters of Lake Victoria (ca. 1400 km2) were surveyed during four 10 day sampling periods in February, April, August and November 1984. Fourty three taxonomic groups were recorded. Oligochaetes, molluscs and dipteran larvae were the most abundant and widely distributed groups. The dominant oligochaetes were Branchiura sowerbyii Beddard and the swamp worm Alma emini
A diver-deployed field instrument that records near-bottom temperature, light intensity and horizontal water speed for up to 3 months is described. The mean, standard deviation and extremes of water speed from currents and waves are recorded. Principal applications are in benthic ecology studies and aquaculture site selection.
R. J Miller; J.-G Dessureault; B. D Beanlands; G. J Sharp
We describe a safe and effective apparatus for washing and reducing the volume of benthic samples collected by grab samplers aboard ship. The sample is transferred directly from the dredge to the apparatus and then washed with water pumped through pipes in the apparatus and from onboard hoses. Wastewater and materials smaller than 0.541 mm in diameter are washed overboard.
Phillip N. Pepper; Thomas L. Girard; Martin A. Stapanian
A biostratigraphic survey of 57 Late Ordovician marine shelly invertebrates from the Climacograptus manitoulinensis zone of eastern Canada supports suggestions that throughout the Early Phanerozoic benthic marine speciations occurred preferentially in marginal marine environments. The species subsequently spread onto the craton. There is no obvious positive correlation between the times of first appearance of new associations or novel communities along
Benthic foraminifera from an intertidal mudflat (Bay of Bourgneuf, France) have been exposed to different types of oil-polluted seawater in an experimental laboratory setting. The aim of this experiment was to study the response of foraminiferal faunas from the intertidal zone to oil spills, as observed after the wreckage of the Erika oil tanker in December 1999 on the French
S. R. Ernst; J. Morvan; E. Geslin; A. Le Bihan; F. J. Jorissen
... high secondary production of benthic macroinvertebrates in open-canopy rapids. ... River, North Carolina, to test whether varying amounts of Podostemum influenced ... We estimated that P. ceratophyllum increased surface area by 3 to 4 times ... We recommend that you also print this page and attach it to the printout of ...
A wealth of data are available on the seasonal variation of plankton communities, but few studies take into consideration the circannual cycles of benthic organisms. In fact, the macrobenthos is generally considered as composed by slow-growing organisms showing variations mainly in relation to substrate competition. On the contrary, hydroids are an important group of macrobenthos that, in temperate but also
G. Bavestrello; S. Puce; C. Cerrano; E. Zocchi; N. Boero
Potential nitrification rates (PNR) directly associated with isolated marine macrobenthic invertebrates were measured for a range of benthic epifaunal and infaunal species (bivalves, gastropods, polychaetes and crustaceans) collected from the Sacca di Goro, Po River delta, Italy. In the case of the filter-feeding bivalves, Tapes philippinarum and Mytilus galloprovicialis the PNR associated with the shell surfaces and dissected animal tissues
Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter
Ulrike Braeckman; Pieter Provoost; Tom Moens; Karline Soetaert; Jack J. Middelburg; Magda Vincx; Jan Vanaverbeke; Andrew Wilby
Habitat-based ecological risk assessments rely, in part, on estimates of the ecological value of the habitats at risk. As part of a larger programmatic effort to estimate estuarine habitat values, we determined benthic macrofauna-habitat relationships for 8 intertidal habitats i...
Marine rocky benthic communities present rich contrasts in spatial pattern. Its quantification is a prerequisite for the comparison of spatial pattern across communities, for the evaluation of temporal changes, and for the analysis of the effects of pattern on ecological processes. This study pursues two goals: (1) to evaluate the potential application of landscape pattern indices to the description of
Accurate knowledge of factors affecting the survival of early life stages of marine invertebrates is critically important for understanding their population dynamics and the evolution of their diverse reproductive and life-history characteristics. Chemical defense is an important determinant of survival for adult stages of many sessile benthic invertebrates, yet relatively little consideration has been given to chemical defenses at the
Climate changes can influence the input of meltwater from the polar ice sheets. In Antarctica, signatures of meltwater input during the Holocene may be recorded in the benthic fossils which exist at similar altitudes above sea level in emerged beaches aro...
Solids from marine municipal discharges settle to the sea bottom where they cause major but potentially reversible changes in the biomass and trophic structure of macrobenthic communities. The relationships may be useful in forecasting changes in the size and structure of benthic...
Hippolyte inermis Leach 1814 is a benthic shrimp characterized by a peculiar mechanism of sex reversal influenced by diatom foods. In fact, the appearance of primary females in spring is due to an apoptotic early disruption of the androgenic gland and of the male gonad, triggered by still unknown compounds present in diatoms of the genus Cocconeis. The influence of
Benthic chamber measurements of the reactants and products involved with biogenic matter remineralization (oxygen, ammonium, nitrate, nitrite, phosphate, silicate, TCO2and alkalinity) were used to define solute exchange rates between the sediment and overlying water column of Port Phillip Bay, Australia. Measurements at various sites throughout the bay, conducted during the summers of 1994 and 1995, indicate that the variability in
W. M. Berelson; D. Heggie; A. Longmore; T. Kilgore; G. Nicholson; G. Skyring
Airborne hyperspectral data was collected in April 1999 over 16 square kilometres of coastal waters adjacent to the South Australian Bolivar Wastewater Treatment Plant (near Adelaide). Concurrent in situ measurements of benthic reflectances were collected. A subsequent field-work mission to validate the 1999 image analysis was completed in February 2000. The aim was to map substrate type accurately, differentiating species
J. M. Anstee; A. G. Dekker; V. Brando; N. Pinnel; G. Byrne; P. Daniel; A. Held
The feasibility of permanent benthic quadrats checked by SCUBA divers was tested. Stations were set up on the bottom of six representative aquatic habitats, both marine and inland, including oligotrophic and eutrophic ponds, river, coastal lagoon, estuary, and open marine coast. Data include physical-chemical factors, species composition, number and height of shoots, and general observations. From volume\\/length constants, the standing
The pore-water geochemistry and benthic foraminiferal assemblages of sediments from two slope sites and within the central portion of the Santa Barbara Basin were characterized between February 1988 and July 1989. The highest foraminiferal numerical densities (1197 cm-3 as determined by an ATP assay) occurred at a slope site in June 1988 (550 m) in partially laminated sediments. In continuously
Aim To evaluate the influence of geographical distribution on the extinction risk of benthic marine invertebrates using data from the fossil record, both during times of background extinction and across a mass-extinction episode. Total geographical range is contrasted with proxies of global abundance to assess the relationships between the two essential components of geographical distribution and extinction risk. Location A
Summary Station-holding performance was determined on a smooth substratum and on a grid substratum for three species of benthic fishes differing in body shape, surface texture, density, friction coefficient and behavioural repertoire. The grid was made of wires parallel to the flow, which raised fish into the free stream. Limited observations were also made on the benthopelagic cod. Station-holding perform-
We examine three radium isotopes (224Ra, 223Ra and 226Ra) as a sediment-water interface tracer in upper Indian River Lagoon. Benthic fluxes are estimated using lagoon budgets, benthic chambers and pore water profiles. The lagoon budget approach estimates range from ~20 dpm/m2-d for 224Ra to ~7 dpm/ m2-d for 223Ra to zero for 226Ra. Benthic Chamber flux estimates determined over an 8 hour time period are statistically no different than zero for all three isotopes. Pore water profile flux estimates are low with 0.5 dpm/m2-d for 224Ra to 0.2 dpm/m2-d for 223Ra and zero for 226Ra. Benthic flux estimates correlate with the regeneration rates of the individual isotopes. Radium-224 has the largest flux value and is the isotope with the fastest regeneration rates due to a short half-life. The isotope with the slowest regeneration rate (226Ra) due to a 1600-year half-life, cannot be distinguished from zero in any of the estimates. The short half-life of 224Ra and 223Ra, allow for the examination of exchange processes at the sediment-water interface that cannot be achieved with the long-lived radium isotope (226Ra).
Smoak, J. M.; Swarzenski, P. W.; Cable, J. E.; Martin, J. B.
In the temperate open ocean of the modern northeast Atlantic, the spring bloom of phytoplankton leads to a seasonal pulse of detrital organic material (phytodetritus) to the ocean floor. Opportunistic benthic foraminifera rapidly colonise this food resource, producing large numbers of individuals whose tests are ultimately added to the sediment. One of these taxa, Epistominella exigua, shows periodic peaks in
C. W. Smart; S. C. King; A. J. Gooday; J. W. Murray; E. Thomas
The problem of variability in benthic density estimates from stream sampling was reassessed using data from a number of stream studies, including our own. When data were analyzed assuming a negative binomial distribution and a tolerated precision of 40% of the mean, it was apparent that earlier estimates of hundreds of samples required to estimate density were inaccurate. Based on
Endothall and diquat are herbicides commonly applied in lakes to control troublesome macrophytes. Chemical treatments such as these, however, may perturb an aquatic ecosystem through toxic effects on non-target species. In this study endothall and diquat were tested and compared on a sample of freshwater benthic macroinvertebrates taken from Lake Waban, Wellesley, Massachusetts. Endothall and diquat control all the primary
Ernest H. Williams; Ellen L. Mather; Sandra M. Carter
Efforts that are underway to rehabilitate the Florida Bay ecosystem to a more natural state are best guided by a comprehensive understanding of the natural versus human-induced variability that has existed within the ecosystem. Benthic foraminifera, which are well-known paleoenvironmental indicators, were identified in 203 sediment samples from six sediment cores taken from Florida Bay, and analyzed to understand the
Efforts that are underway to rehabilitate the Florida Bay ecosystem to a more natural state are best guided by a comprehensive understanding of the natural versus human-induced variability that has existed within the ecosystem. Benthic foraminifera, which are well-known paleoenvironmental indicators, were identified in 203 sediment samples from six sediment cores taken from Florida Bay, and analyzed to understand the
The upper Great Lakes contain a diverse array of benthic algal communities. Characteristic communities occupy substrates from the supralittoral to depths in excess of 30 m. Diatoms are the dominant taxonomic group present in terms of numbers, and usually in terms of biomass, exce...
A pronounced deficit of nitrogen (N) in the oxygen minimum zone (OMZ) of the Arabian Sea suggests the occurrence of heavy N-loss that is commonly attributed to pelagic processes. However, the OMZ water is in direct contact with sediments on three sides of the basin. Contribution from benthic N-loss to the total N-loss in the Arabian Sea remains largely unassessed. In October 2007, we sampled the water column and surface sediments along a transect cross-cutting the Arabian Sea OMZ at the Pakistan continental margin, covering a range of station depths from 360 to 1430?m. Benthic denitrification and anammox rates were determined by using (15)N-stable isotope pairing experiments. Intact core incubations showed declining rates of total benthic N-loss with water depth from 0.55 to 0.18?mmol?N?m(-2)?day(-1). While denitrification rates measured in slurry incubations decreased from 2.73 to 1.46?mmol?N?m(-2)?day(-1) with water depth, anammox rates increased from 0.21 to 0.89?mmol?N?m(-2)?day(-1). Hence, the contribution from anammox to total benthic N-loss increased from 7% at 360?m to 40% at 1430?m. This trend is further supported by the quantification of cd(1)-containing nitrite reductase (nirS), the biomarker functional gene encoding for cytochrome cd(1)-Nir of microorganisms involved in both N-loss processes. Anammox-like nirS genes within the sediments increased in proportion to total nirS gene copies with water depth. Moreover, phylogenetic analyses of NirS revealed different communities of both denitrifying and anammox bacteria between shallow and deep stations. Together, rate measurement and nirS analyses showed that anammox, determined for the first time in the Arabian Sea sediments, is an important benthic N-loss process at the continental margin off Pakistan, especially in the sediments at deeper water depths. Extrapolation from the measured benthic N-loss to all shelf sediments within the basin suggests that benthic N-loss may be responsible for about half of the overall N-loss in the Arabian Sea. PMID:23226143
Sokoll, Sarah; Holtappels, Moritz; Lam, Phyllis; Collins, Gavin; Schlüter, Michael; Lavik, Gaute; Kuypers, Marcel M M
During the past 60 years, considerable effort has been expended in studies of the relations of the biotic community and physicochemical characteristics of San Francisco Bay water. In very recent years these studies have emphasized the relations between the 'state of health' of bottom-living invertebrates (the benthos) and the levels of pollutants in the bay. Benthic organisms, generally sessile, are unable to escape deleterious environmental changes, and they reflect these changes in alterations of normal species composition of assemblages and species abundance. Data that expands understanding of these relations in urbanized areas such as San Francisco Bay are critical. Because of the implications of such data in control of water quality, the U.S. Geological Survey undertook a review of the results and major conclusions of San Francisco Bay benthic surveys. The size and species composition of faunal assemblages are largely controlled by the salinity of the water, the texture of the bottom sediments, and locally by wastes discharged into the bay. Efforts to describe the structure and function of benthic communities of the bay and to quantify the effects of waste discharge on them have been hampered by inconsistent and often faulty sampling methodology and species identification. Studies made show a lack of information on the normal life processes of the organisms concerned. The diversity index (a mathematical expression of the number of kinds of organisms present at a location), commonly used to describe the 'health' of the benthic community, has been employed without regard for the need for standardizing methodology and species identifications or for understanding natural biological processes that affect such mathematical indices. There are few reliable quantitative data on the distribution of benthic organisms in San Francisco Bay with which future assessments of the 'health' of the benthic community might be compared. Methods for study of the benthos must be standardized, identifications of species verified by trained taxonomists, and new field and laboratory studies undertaken before we can expect to obtain an accurate description of the benthic fauna and its relations with the environment.
Estuary-wide benthic macrofauna habitat associations in Willapa Bay, Washington, United States, were determined for 4 habitats (eelgrass [Zostera marina], Atlantic cordgrass [Spartina alterniflora], mud shrimp [Upogebia pugettensis], ghost shrimp [Neotrypaea californiensis]) in 1996 and 7 habitats (eelgrass, Atlantic cordgrass, mud shrimp, ghost shrimp, oyster [Crassostrea gigas], bare mud/sand, subtidal) in 1998. Most benthic macrofaunal species inhabited multiple habitats; however, 2 dominants, a fanworm, Manayunkia aestuarina, in Spartina, and a sand dollar, Dendraster excentricus, in subtidal, were rare or absent in all other habitats. Benthic macrofaunal Bray Curtis similarity varied among all habitats except eelgrass and oyster. There were significant differences among habitats within- and between-years on several of the following ecological indicators: mean number of species (S), abundance (A), biomass (B), abundance of deposit (AD), suspension (AS), and facultative (AF) feeders, Swartz's index (SI), Brillouin's index (H), and jackknife estimates of habitat species richness (HSR). In the 4 habitats sampled in both years, A was about 2.5× greater in 1996 (a La Niña year) than 1998 (a strong El Niño year) yet relative values of S, A, B, AD, AS, SI, and H among the habitats were not significantly different, indicating strong benthic macrofauna habitat associations despite considerable climatic and environmental variability. In general, the rank order of habitats on indicators associated with high diversity and productivity (high S, A, B, SI, H, HSR) was eelgrass = oyster ? Atlantic cordgrass ? mud shrimp ? bare mud/sand ? ghost shrimp = subtidal. Vegetation, burrowing shrimp, and oyster density and sediment %silt + clay and %total organic carbon were generally poor, temporally inconsistent predictors of ecological indicator variability within habitats. The benthic macrofauna habitat associations in this study can be used to help identify critical habitats, prioritize habitats for environmental protection, index habitat suitability, assess habitat equivalency, and as habitat value criteria in ecological risk assessments in Willapa Bay.
Mucus films, flocs or foams consisting of fine sand, algae and detritus frequently occur in the surface waters of rocky intertidal reef flats during incoming tide. These masses are referred to as mucus aggregates. We examined the developmental process of mucus aggregates and their abundance, distribution, migration and trophic composition. The trophic composition of mucus aggregates was then compared to those of sediments to evaluate their potential nutritional value for benthic animals. The organic matter content, chlorophyll a concentration, microalgal density and bacteria-derived fatty acid contents of mucus aggregates were higher than those observed in sediment, suggesting that mucus aggregates contain not only high levels of organic matter but also dense concentrations of microalgae and bacteria; therefore, mucus aggregates may serve as a qualitatively more energetic food source for benthic fauna compared to sediments. Benthic diatoms were the most abundant organisms in mucus aggregates. Large numbers of diatoms were trapped in fine mineral particles and mucilage-like strings, suggesting that a portion of the mucus is secreted by these benthic microalgae. Mucus aggregate accounted for only 0.01-3.9% of the daily feeding requirements of the dominant detritivore, Ophiocoma scolopendrina (Echinodermata: Ophiuroidea) over the entire sampling area. In contrast, for the species population on the back reef, where mucus aggregates ultimately accumulate, mucus aggregates provided from 0.4 to 113.3% of food for this species. These results suggest that mucus aggregate availability varies spatiotemporally and that they do not always provide adequate food sources for O. scolopendrina populations.
The influence of marine plants representing different stages of eutrophication on carbon decomposition and production, benthic nutrient fluxes and denitrification was examined in 4 shallow warm-temperate Australian lagoons. Differences in carbon production and decomposition across the lagoons were the main regulators of the quantity and quality of benthic nutrient fluxes and the relative proportion of nitrogen lost through denitrification. For
For sessile organisms, dispersal and recruitment are typically spatially stochastic, but there is little understanding of how this variability scales up to influence processes such as competitive coexistence. Here we argue that coexistence of benthic marine animals is enhanced by stochastic differences between species in the spatial distribution of larval settlement. Differentiation of settlement distributions among competitors results in intraspecifically aggregated settlement, which can reduce overall interspecific competition and increase overall intraspecific competition. We test for the components of this mechanism using a pair of subtidal invertebrates, and we find that the mean interspecific effect of the dominant competitor is substantially reduced by natural settlement variability. Using a simulation parameterized with experimental data, we find that variable settlement could play an important role in long-term coexistence between these species. This mechanism may apply broadly to benthic marine communities, which can be highly diverse and typically exhibit large settlement fluctuation over a range of scales. PMID:21661570
To understand substrate preferences of benthic foraminifera, I have conducted in situ recoIonization experiments at a permanent deep-sea station, OBB No. 2 (1445 m depth) in Sagami Bay, central Japan since 1991. Substrates, prepared in culture bottles, include defaunated natural sediment, defaunated sediment enriched with dried Chlorella, defaunated sediment covered with plankton netting, and artificial substrate made of silt-size glass
We have studied the metazoan parasite fauna of 52 species of deep-living benthic fishes from depths of 53 to 5000m off the New York Bight (3949°N; 7072°W). 17144 parasites were recovered from 1712 fishes. The infestation rate was 80%, with an average of 12.5 worms per host. Percentage occurrence by group among all fishes was Monogenea 12.9%, Digenea 48%, Cestoda
Teleost fishes capture prey using ram, suction, and biting behaviors. The relative use of these behaviors in feeding on midwater\\u000a prey is well studied, but few attempts have been made to determine how benthic prey are captured. This issue was addressed\\u000a in the wrasses (Labridae), a trophically diverse lineage of marine reef fishes that feed extensively on prey that take
L. A. Ferry-Graham; P. C. Wainwright; M. W. Westneat; D. R. Bellwood
In glacial lakes on an alpine pasture in Switzerland, benthic cyanobacteria produced microcystin, a cyclic hepatotoxic heptapeptide.\\u000a The cyanobacteria formed dense mats on sediments and submerged stones. The mats consisted mainly of Oscillatoria limosa, Phormidium\\u000a konstantinosum (= Oscillatoria tenuis) and Tychonema granulatum (= Oscillatoria granulata). In order to characterize the ecological\\u000a conditions of these cyanobacteria, nutrient concentrations were determined, and
Konstanze Mez; Kurt Hanselmann; Hans Rudolf Preisig
Two novel cyclic lipopeptides, anabaenolysin A and anabaenolysin B, were isolated from two benthic cyanobacterial strains of the genus Anabaena. This novel class of cyanobacterial lipopeptides has a general structure of a small peptide ring consisting of four amino acids from which two are proteinogenic and two unusual; glycine1, glycine2, 2-(3-amino-5-oxytetrahydrofuran-2-yl)-2-hydroxyacetic acid3 and a long unsaturated C18 ?-amino acid4 with
Jouni Jokela; Linn Oftedal; Lars Herfindal; Perttu Permi; Matti Wahlsten; Stein Ove Døskeland; Kaarina Sivonen
Estuarine waters are known to enhance productivity in coastal environments, but little is known about the impact that nutrient-rich waters can have on benthic microbial processes. After intensive surface sediment sampling in a wide coastal area impacted by river plume waters, we performed on-site microcosm experiments in which we added estuarine waters, rich in both organic and inorganic N and P, to pristine offshore sediments. This experimental approach has been conducted in different coastal areas for two consecutive years, in which the river-plume waters differed in both inorganic and organic N and P content. Benthic bacterial response (total bacterial abundance and biomass, aminopeptidase, beta-d-glucosidase and bacterial C production) was investigated in treated and non-treated sediments. All structural and functional microbial variables increased significantly after plume-water supply (within 12-24 h bacterial abundance in the sediment doubled and enzymatic activities increased up to >50%). Results indicate that inorganic N supply from plume waters was sufficient to induce a significant response in benthic bacterial abundance, independently from the presence of high and/or variable N:P ratios. However, bacterial carbon production and exo-enzymatic activities increased significantly when the supply of organic P from plume waters was associated with a decrease of organic N:P ratios. We conclude that plume waters have important effects on benthic bacterial dynamics, but the extent of their biogeochemical implications is largely dependent upon their organic P availability and on stoichiometric ratios of organic nutrients supplied by plume waters. PMID:19712359
Manini, Elena; Luna, Gian Marco; Danovaro, Roberto
The effects of various environmental factors on Znâ¶âµ uptake and ; loss were investigated in benthic algae. Increasing the pH promoted Znâ¶âµ ; uptake and retarded Znâ¶âµ loss in Ulva lactuca, Porphyra umbilicalis, and ; Laminaria agardi. A similar pH dependency was displayed by killed algae of the ; same species which in all cases absorbed more Znâ¶âµ than the
Downloadable electronic version of a section of a book of the same title; a naturalist's approach to understanding the environment of that region. A searchable summary includes brief introduction, list of headings, keyword list, and cross-references to other sections. Benthic habitats are composed of a variety of sediment types and are exposed to a wide range of water conditions, leading to the development of diverse plant and animal communities.
The flux of dissolved reactive phosphate from Potomac riverine and estuarine sediments is controlled by processes occurring\\u000a at the water-sediment interface and within surficial sediment.In situ benthic fluxes (0.1 to 2.0 mmoles m?2 day?1) are generally five to ten times higher than calculated diffusive fluxes (0.020 to 0.30 mmoles m?2 day?1). The discrepancy between the two flux estimates is greatest
An expansive area of bottom-water hypoxia occurs annually during the summer on the Louisiana continental shelf (LCS). The formation of these hypoxic waters has been linked to spring Mississippi River nutrient loading. Inferred in this linkage is the remineralization of nutrients, in both the sediments and water-column, to support primary production (PP) across the LCS. Benthic-pelagic interactions also mediate bottom-water
J. Lehrter; R. Devereux; D. Beddick; D. Yates; M. Murrell; J. Hagy; J. Kurtz
As part of an extensive Reservoir Monitoring program to examine the ecological health of reservoirs in the TVA system, benthic communities were sampled and evaluated at 41 locations on 14 TVA reservoirs. Up to ten dredge samples were collected at locations from the forebay, inflow and transition zones. Surveys were conducted between mid-March and mid-April, 1991. The results of these surveys are presented and discussed in this report.
Abstract: Densities of the major benthic macroinvertebrate groups declined dramatically at sites shallower than 50 m in southern Lake Michigan between 1980 and 1993. Declines in Diporeia, Oligochaeta, and Sphaeriidae ranged from 40 to 75% at these depths. Total densities declined from 16 800·m, in 1980?1987. We hypothesize that the filtering activities of large populations of Dreissena polymorpha,in nearshore waters
Thomas F. Nalepa; David J. Hartson; David L. Fanslow; Gregory A. Lang; J. Lozano
As part of an extensive program to monitor the health of reservoirs in the TVA system, dredges were used to sample benthic life at 36 locations on 12 Tennessee Valley Authority reservoirs and the Tennessee River downstream from the lowest reservoir in the system. Up to ten dredge samples were collected from forebay, transition zone, and inflow locations of typical reservoirs. The survey was conducted between mid March and mid April, 1990. Results are described.
Matched chemical and ecological monitoring data were used to assess the effects of iron on benthic macroinvertebrate communities.\\u000a Three measures of iron exposure: dissolved, total, and particulate iron were assessed. Ecological responses were normalised\\u000a to an unimpacted reference condition to make site-specific predictions of the reference condition. Ecological data were expressed\\u000a as an Ecological Quality Index (EQI), indicating quality relative
The flux of dissolved reactive phosphate from Potomac riverine and estuarine sediments is controlled by processes occurring at the water-sediment interface and within surficial sediment.In situ benthic fluxes (0.1 to 2.0 mmoles m-2 day-1) are generally five to ten times higher than calculated diffusive fluxes (0.020 to 0.30 mmoles m-2 day-1). The discrepancy between the two flux estimates is greatest
Benthic invertebrate populations at the Surry power plant on James River, Virginia and the C. P. Crane power plant on Saltpeter\\u000a Creek, Maryland exhibited large spatial and temporal variations. At C. P. Crane, where the cooling water is pumped between\\u000a two tidal creeks, populations in the receiving creek exhibited five response patterns: 1) mitigation of a winter dieoff (Rangia cuneata,
. Seven marine benthic crustaceans were exposed in 4 d water-only toxicity tests to five concentrations of fluoranthene. After\\u000a exposures, mortality (LC50) and the ability to bury in clean sediment (EC50) were determined. Survivors were then exposed to UV radiation for 1 h. The differences between LC50s and EC50s before and after UV exposure were used to assess photoinduced toxicity.
B. L. Boese; J. O. Lamberson; R. C. Swartz; R. J. Ozretich
Coral reef ecosystems, the most varied on earth, continually face destruction from anthropogenic and natural threats. The U.S. Coral Reef Task Force seeks to characterize and map priority coral reef ecosystems in the U.S.\\/Trust Territories by 2009. Building upon NOAA Biogeography shallow-water classifications based on Ikonos imagery, presented here are new methods, based on acoustic data, for classifying benthic terrain
Emily R. Lundblad; Dawn J. Wright; Joyce Miller; Emily M. Larkin; Ronald Rinehart; David F. Naar; Brian T. Donahue; S. Miles Anderson; Tim Battista
A total of 69 samples of benthic animals was taken in the lower 20 km of the Raritan River estuary from 1957 to 1960. During 1957, under heavily polluted conditions, no frcsh- water spccics wcrc discovered. Of the I7 marinc species found, the barnacle BaEanus im- prouisus extended 8.5 km above the river mouth; the remaining species were confined to
In ecological studies involving the analysis of ?2.4 million living (stained) individual tests, to date ?2140 species of benthic foraminifera have been recorded. Of these 602 species are agglutinated, 341 porcelaneous and 1197 hyaline. The numbers of species in the major environments are: marginal marine 701 (in ?1.5 million individuals), shelf 989 (in ?0.6 million individuals) and deep sea 831 (in ?0.3 million individuals).
Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments\\u000a of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel\\u000a and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of\\u000a foraminiferal tests revealed three assemblages that
A. Z. Al-Zamel; M. A. Al-Sarawi; S. R. Khader; I. A. Al-Rifaiy
Lagoons are ecotones between freshwater, marine and terrestrial biotopes, characterized by internal ecosystem heterogeneity, due to patchy spatial and temporal distribution of biotic and abiotic components, and inter-ecosystem heterogeneity, due to the various terrestrial-freshwater and freshwater -marine interfaces. 2 - Here, we carried out an analysis of environmental heterogeneity and benthic macro-invertebrate guilds in a sample of 26 Italian lagoons
It is unknown whether carbonaceous geosorbents, such as black carbon (BC) affect bioturbation by benthic invertebrates, thereby possibly affecting sediment-water exchange of sediment-bound contaminants. Here, we assess the effects of oil soot on polychlorinated biphenyl (PCB) mass transfer from sediment to overlying water, for sediments with and without tubificid oligochaeta as bioturbators. PCB levels were so low that toxicity to the oligochaeta played no role, whereas soot levels and binding affinity of PCBs to soot were so low that pore water PCB concentrations were not significantly affected by binding of PCBs to soot. This setup left direct effects of BC on bioturbation activity as the only explanation for any observed effects on mass transfer. Mass transfer coefficients (KL) for benthic boundary layer transport were measured by a novel flux method using Empore disks as a sink for PCBs in the overlying water. For the PCBs studied (logKow 5.2-8.2), KL values ranged from 0.2 to 2 cm×d(-1) in systems without tubificids. Systems with tubificids showed KL values that were a factor of 10-25 higher. However, in the presence of oil soot, tubificids did not cause an increase in mass transfer coefficients. This suggests that at BC levels as encountered under field conditions, the mechanism for reduction of sediment-water transfer of contaminants may be twofold: (a) reduced mass transfer due to strong binding of the contaminants to BC, and (b) reduced mass transfer of contaminants due to a decrease in bioturbation activity. PMID:21543104
Sediment physicochemical characteristics, benthic community structure, and toxicity were measured at reference and contaminated intertidal mudflats around the North Island of New Zealand. Chronic whole-sediment toxicity tests were conducted with the estuarine amphipod, Chaetocorophium lucasi and the marine bivalve, Macomona lilana, and pore-water toxicity tests were conducted with embryos of the echinoid, Fellaster zelandiae. Although concentrations of organic chemicals and heavy metals were up to several orders of magnitude higher at the sites considered to be contaminated, levels of contamination were relatively low compared to internationally based sediment quality guidelines. Although no pronounced difference was found in benthic community structure between reference and contaminated sites, multivariate analysis indicated that natural sediment characteristics and factors related to contamination may have been affecting community structure. Although benthic effects caused by present levels of contamination are not yet dramatic, subtle changes in community structure related to pollution may be occurring. The two whole-sediment and the pore-water toxicity tests presented different response patterns. Growth of C. lucasi and M. liliana was a less sensitive endpoint than survival. None of the three toxicity tests responded more strongly to the contaminated than to the reference sites, that is, neither natural-sediment and pore-water characteristics nor unmeasured contaminants affected the test organisms. It is possible that sediment collection and handling may have induced chemical changes, confounding interpretation of toxicity tests.
Nipper, M.G.; Roper, D.S.; Williams, E.K.; Martin, M.L.; Van Dam, L.F.; Mills, G.N. [National Inst. of Water and Atmospheric Research Ltd., Hamilton (New Zealand)
Mass occurrence of benthic cyanobacterial mats in a sequence of Late Devonian black shales and bituminous limestones of the Holy Cross Mts. (central Poland), enclosing the famous Kellwasser and Hangenberg extinction horizons, is reported. The microbiota forming the mats is compared with some modern benthic chroococcalean cyanobacteria. Similarly to their extant counterparts, the Devonian cyanobacteria must had been phototrophic and oxygenic aerobes which could, however, tolerate slightly sulfidic conditions characterizing the near-bottom waters of the Late Devonian epicontinental sea. The cyanobacterial mats successfully colonized the oxygen-deficient and H(2)S-enriched seabed otherwise unfavorable for most other benthic biota. The redox state of this sluggish Late Devonian sea, ascribed previously mostly to anoxic or euxinic conditions, is reassessed as probably pulsating between anoxic, dysoxic, and weakly oxic conditions. The redox state was dependent on the rate of oxygen production by the cyanobacterial mats, the intensity of H(2)S emissions from the decaying mat biomass, and the rate of planktonic production. PMID:22882315
In soft sediments, Dreissena spp. create firm substrate in the form of aggregates of living mussels (druses) that roll free on the sediments. Druses provide physical structure which increases habitat heterogeneity, and the mussels increase benthic organic matter through the production of pseudofeces and feces. Descriptive and experimental studies were used to determine: 1) whether the density of benthic invertebrates in soft sediments increased in the presence of druses, and 2) whether the invertebrate assemblage responded to the physical structure provided by a druse or to some biotic effect associated with the presence of living mussels. In core samples collected biweekly during summer in Presque Isle Bay, Erie, Pennsylvania, amphipods, chironomids, oligochaetes, turbellarians, and hydrozoans were significantly more abundant in sand with druses than in bare sand. When mesh bags containing either a living druse, non-living druse, or no druse were incubated in the bay for 33 d, we found that chironomids were significantly more abundant in treatments with living druses than with non-living druses, and in treatments with non-living druses than with no druse; turbellarians, amphipods, and hydrozoans were significantly more abundant in treatments with living or non-living druses than with no druse; oligochaetes showed no significant differences among treatments. This study demonstrates that most taxa of benthic invertebrates in soft substrate respond specifically to the physical structure associated with aggregates of mussel shells, but further study is needed to examine chironomid responses to some biotic effect dependent on the presence of living mussels.
Botts, P. Silver; Patterson, Benjamin A.; Schloesser, Don W.
Traditional Ecological Knowledge (TEK) is the empirically accumulated knowledge of local communities whose livelihoods depend directly on natural resources. TEK has a considerable potential as a reliable, rapid and low cost information source. However, its use for decision making in environmental management is frequently challenged due to the lack of scientific validation and the multiple and poorly understood biases deriving from measurement and analytical errors, as well as from political, cultural and religious sources. During the planning stage of a Marine Protected Area (MPA) in Southeastern Brazil we assessed fisherfolk TEK regarding seabed features, comparing it with results from a conventional oceanographic assessment. TEK was acquired and synthesized during a survey involving 19 fishing villages and a consensus analysis that minimized variation among individual fisherfolks and communities. The oceanographic survey included high resolution benthic habitat mapping tools such as sidescan sonar and ground-truthing with SCUBA near the interfaces of benthic features identified by fisherfolk. Nearly 3000 km(2) of seafloor were mapped by local fisherfolk as "gravel", "sand", "mud" and "reef structures", while side-scan sonar surveys covered approximately 360 km with an average 400 m swath. Analyses of overlap and proximity showed that TEK is relatively cost-effective and accurate for large-scale benthic surveys, especially as a starting point for planning oceanographic surveys. Moreover, including TEK in the planning stage of MPAs may increase communities' participation and understanding of the costs and benefits of the new access and fishing effort regulations. PMID:23262411
Teixeira, João Batista; Martins, Agnaldo Silva; Pinheiro, Hudson Tercio; Secchin, Nelio Augusto; Leão de Moura, Rodrigo; Bastos, Alex Cardoso
This report presents a summary of data collected and an updated progress report for a long-term benthic study conducted to measure the long-term effects of power plant operations on benthic populations and to identify long-term trends and annual cycles in these populations. Benthic organisms and the physical\\/chemical characteristics of sediments and water were sampled between July 1981 and May 1982
Recruitment is an important process in regulating many marine benthic communities and many studies have examined factors controlling the dispersal and distribution of larval immigrants. However, benthic species also have early post-settlement life-stages that are dramatically different from adult and larval stages. Predation on these stages potentially impacts measured recruitment and the benthic populations and communities that ultimately develop.We examined
Data on the composition of benthic foraminiferal faunas at Deep Sea Drilling Project Site 575 in the eastern equatorial Pacific Ocean were combined with benthic and planktonic carbon- and oxygen-isotope records and CaCO3 data. Changes in the composition of the benthic foraminiferal faunas at Site 575 predated the middle Miocene period of growth of the Antarctic ice cap and cooling
Dissolved organic carbon (DOC) flux dynamics were examined in the context of other biogeochemical cycles in intertidal sediments\\u000a inhabited by benthic microalgae. In August 2003, gross oxygenic photosynthetic (GOP) rates, oxygen penetration depths, and\\u000a benthic flux rates were quantified at seven sites along the Duplin River, GA, USA. Sediments contained abundant benthic microalgal\\u000a (BMA) biomass with a maximum chlorophyll a
William P. Porubsky; Liliana E. Velasquez; Samantha B. Joye
Algal biomass, C:N:P (carbon:nitrogen:phosphorus) ratios and APA (biomass specific alkaline phosphatase activity) were measured in benthic algal communities on living substrates (mussels and macrophytes) and on rocks and stones (epilithon) in three lakes of different trophy. Benthic algal communities on living substrates had lower C:N:P ratios than epilithon, whereas algal biomass was highest on rocks and stones. Benthic algal biomass
Eleven sites were located on Mediterranean continental shelves to explore the link between the physical characteristics and epibenthic fauna from soft-sediment habitats. These sites, at 32-82 m in depth, were associated with fishing grounds and the trawling intensity was estimated at the site scale to assess the effects of trawling on benthic communities. Each site was surveyed with Multi-Beam (bathymetry and backscatter), side-scan sonar, benthic grabs and a surface dredge. The sites were clustered in three habitat types. Habitat 1, with moderate trawling disturbance, was characterised by homogeneous mud and associated epifauna that was also highly homogeneous across sites. Habitat 2, with sandy mud and scattered gravel and rocks, had a high abundance of sessile suspension feeders that probably attach to the coarser substratum and benefit from the low fishing disturbance in these sites. Habitat 3 included sites with heterogeneous sediments with maërl as the prevailing biocenosis and having the highest species richness, despite being subjected to variable trawling intensity. Statistical models were used to relate environmental parameters and the species abundance. More than 3 physical variables were necessary to explain the epifaunal patterns across sites, including the percentage of mud, sediment heterogeneity and fishing effort. These analyses are an essential step for extrapolating information from benthic samples to the larger scale of habitats, mapped through acoustic surveys. Despite this, a good integration is required between the mapping of physical habitat distribution and the ecological knowledge of communities.
Paleoceanographic conditions in the Japan Sea changed drastically during the late Quaternary in association with orbital and suborbital cycles and glacio-eustatic sea level changes. However, few studies had been examined long-term sediment records older than last intergracial period because of the lack of long cores which contains continuous paleoclimatic records and difficulties reconstructing high-resolution age models. Especially disappearance of benthic foraminifers by euxinic bottom water conditions during glacial maxima makes it difficult to understand specific bottom water environments. In this study, we reconstructed benthic foraminiferal stable isotopic stratigraphy of the Japan Sea core with the resolution in 2 kyr. and compared the global stack of benthic foraminfieral ?18O curve (LR04, Lisiecki & Raymo, 2005). The investigated core MD01-2408, was recovered from 806 m water depth, off Akita Prefecture during IMAGES VII cruise. It had recorded continuous paleoenvironmental histories during the last 230 kyr through the core. This core was mainly consisted of alternating layers of homogeneous light colored silty clay and laminated or bioturbated dark colored silty clay, occasionally intercalating volcanic ash layers. The most abundant benthic foraminiferal species are Uvigerina akitaensis, Angulogerina kokozuraensis and Islandiella norcrossi. Abundance of these species fluctuated drastically through the core. No benthic foraminifera is found in two dark layer intervals 4 ~ 5 mbsf and 25 ~ 25.5 mbsf, corresponding 15 ~ 25 kyr and 149 ~ 152 kyr, respectively, probably representing super anoxic bottom water conditions(Oba et al 1984 1991;Tada et al., 1999). ?18O of U. akitaensis and A. kokozuraensis showed a similar values with a precision of ± 0.27 and it was inferred that both species had similar habitat. ?18O of both species in core MD01-2408 fluctuated with the range of 2 over 230 kyr. Although benthic ?18O stack of LR04 reached to 5 during the glacial maxima, ?18O of core MD01-2408 were 2.6 and 2.7 during MIS 2a and MIS 6, respectively. Differences of bottom water ?18O between global average and the Japan Sea were 2.3 ~ 2.4 . This reason of negative excursions was considered as downward diffusion of low saline surface water to the bottom (Oba et al 1984 1991). However, the interglacial stages during MIS3 to 5, benthic foraminiferal ?18O was rather heavier (4.0 ~ 4.5) than MIS2 and 6. Furthermore, benthic ?18O values had became ligher from MIS5a to 2 gradually. These ?18O shift should be attributed to bottom water salinity change rather than temperature. It is considered that the thickness of less saline surface water had increased and strongly affected to the bottom water properties in the glacial maximum stages through the last 230 kyr.
Benthic invertebrate indices have commonly been utilized to assess benthic invertebrate communities. These indices have been constructed using different techniques, but have shown different levels of application success. For example, the EMAP Virginian Province Index did not pe...
The fossil record provides understanding of possible linkages between long-term environmental changes and evolution of assemblages and morphological species of deep-sea benthic foraminifera, of which the phylogeny is still little known. Deep-sea benthic foraminifera have long morphological species lives and do not commonly suffer massive extinctions: they live in the largest habitat on earth, species have large geographic ranges or are cosmopolitan, and they use motile propagules to rapidly re-populate regions where populations have been destroyed. Extinction occurs only when rapid and severe environmental change affects such a large part of the deep ocean that no refugia exist, even for common species. Deep-sea benthic foraminifera reacted to global cooling (in the earliest Oligocene, middle Miocene and middle Pleistocene) not by extinction, but by a gradual turnover of species. The most extensive turnover occurred in the late Eocene through earliest Oligocene, when some presently important ecological niches were first filled. In contrast, deep-sea benthic foraminifera suffered severe extinction (30-50% of species, including common, cosmopolitan, long-lived species) during the rapid global warming of the Paleocene-Eocene Thermal Maximum (PETM), a time of high CO2 levels and potential ocean acidification. The extinction was followed by slow recovery of faunas, but diversity never returned to pre-extinction levels. The PETM and later, less severe short-term periods of global warming (hyperthermals ETM1 and ETM2) were characterized by low diversity faunas dominated by small, thin-walled individuals. No significant net extinction occurred during the later hyperthermals. Such faunas might reflect dissolution, low oxygen conditions, or blooming of opportunistic species after environmental disturbance. Most commonly cited causes of the PETM extinction are: 1. low oxygen concentrations, 2. acidification of the oceans, 3. increase or decrease in oceanic productivity and/or transfer of food to the sea floor, and 4. increasing temperatures. All 4 factors may have contributed to the extinction, but the first three factors varied regionally and by depth, whereas only the temperature increase affected the deep-sea environment globally. High temperatures not only increase overall metabolic rates, but also affect which species of prokaryotes are most active and which labile compounds they generate, thus the compounds and the amount of labile organic matter available for foraminiferal feeding. At sites along a depth transect at Walvis Ridge (SE Atlantic) species that earlier had been abundant in neritic waters ( Tappanina selmensis) increased strongly in abundance. Some surviving deep-sea species underwent diversification and morphological evolution; during and just after the PETM and two other hyperthermal events the deep-sea genus Abyssamina became more abundant (most pronounced at the deeper sites), while evolving into several morphological species. During the warmer intervals its aperture became more irregular in shape, with an extremely asymmetrical shape at the deepest site during ETM1. The aperture in benthic foraminifera directs the streaming of pseudopods, thus the way of food intake, suggesting that the nature of benthic feeding changed during the warm periods. During the early Eocene (a period characterized by hyperthermals), faunas maintained larger differences in assemblage composition between ocean basins than before the extinction. It remains a question whether this faunal heterogeneity reflects the mode of deep-ocean circulation/ventilation during the warmest period of the Cenozoic.
The density and spatial distribution of benthic viruses and prokaryotes in relation to biotic and abiotic factors were investigated in sediment cores collected in Hornsund, a permanently cold fjord on the West coast of Svalbard, Norway. The cores were obtained from the mouth of the fjord to the central basin, along a longitudinal transect. The results of our analyses showed lower densities of viruses (0.2 x 10(8) to 5.4 x 10(8) virus-like particles/g) and lower virus-to-prokaryote ratios (0.2-0.6, with the exception of the uppermost layer in the central basin, where the ratio was about 1.2) at the study site than generally found in the temperate areas, despite the relatively high organic matter content in subpolar sediments. Variations in benthic viral and prokaryote abundances along gradients of particle sedimentation rates, phytopigment concentrations, and macrobenthic species composition together suggested the influence of particle sedimentation and macrobenthic bioturbation on the abundance and spatial distribution ofprokaryotes and viruses in cold habitats. PMID:24151781
Worldwide, many marine coastal habitats are facing rapid deterioration due in part to human-driven changes in habitat characteristics, including changes in flow patterns, a factor known to greatly affect primary production in corals, algae, and seagrasses. The effect of flow traditionally is attributed to enhanced influx of nutrients and dissolved inorganic carbon (DIC) across the benthic boundary layer from the water to the organism however, here we report that the organisms photosynthetic response to changes in the flow is nearly instantaneous, and that neither nutrients nor DIC limits this rapid response. Using microelectrodes, dual-pulse amplitude-modulated fluorometry, particle image velocimetry, and real time mass-spectrometry with the common scleractinian coral Favia veroni, the alga Gracilaria cornea, and the seagrass Halophila stipulacea, we show that this augmented photosynthesis is due to flow-driven enhancement of oxygen efflux from the organism to the water, which increases the affinity of the RuBisCO to CO2. No augmentation of photosynthesis was found in the absence of flow or when flow occurred, but the ambient concentration of oxygen was artificially elevated. We suggest that water motion should be considered a fundamental factor, equivalent to light and nutrients, in determining photosynthesis rates in marine benthic autotrophs.
Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan
A decade has yielded much progress in understanding polar disturbance and community recoverymainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scalesice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago.
Carbon and nitrogen contents (total organic carbon and total nitrogen), chlorophyll-a concentrations in surface sediments and benthic sediment water fluxes of oxygen and carbon dioxide were investigated at five stations in Lake Illawarra (Australia) to compare the sources/quality of sedimentary organic matter and the characteristics of diagenesis and benthic biogeochemical processes for different primary producers (e.g., seagrass, microphytobenthos and macroalgae) and/or sediment types (sand or mud). The unvegetated sediments showed lower C/N ratios (with the lowest value occurring in the deep organic-rich muddy site) than the seagrass (Ruppia or Zostera) beds, which may be due to the contribution of microalgae (mainly diatoms) to the sedimentary organic matter pool. This was also supported by the detection of microalgal pigments in the bare sediments. On an annual basis, seagrass beds exhibited the highest gross primary productivity (O2 or TCO2 fluxes), while the lowest rates occurred in the deep central basin of the Lake. Seasonally, there was a general trend of highest production in spring or summer, and lowest production in winter or autumn. Organic carbon oxidation scenarios, evaluated by either calcium carbonate dissolution or sulfate reduction models, indicated that both models can explain organic matter mineralization. Trophic status was evaluated using different indices including benthic trophic state index, net O2 fluxes and P/R ratios for Lake Illawarra, which led to similar trophic classifications in general, and also the same trends in spatial and seasonal variations. Overall, these data indicated that the Lake was heterotrophic on an annual basis, as the total community carbon respiration exceeded production, and this supported an earlier LOICZ mass balance/stoichiometric modelling conclusion.
Qu, Wenchuan; Morrison, R. J.; West, R. J.; Su, Chenwei
To investigate potential high organisational level impacts of persistent organic pollution in the wetlands in the Sydney Olympic Park (SOP) remediated site, the benthic macroinvertebrate assemblages of seven wetlands within SOP and two off-site reference wetlands were examined. Sediment cores were collected, stained and preserved from each study site and the macroinvertebrates identified to the appropriate taxonomic level (Class, Order, Family, Subfamily). Data were analysed for taxon richness and macroinvertebrate abundance and multivariate techniques were used to identify chemical/physical characteristics of the sediment, which were important influences on the differences in the assemblage between study sites. Macroinvertebrate abundance was highly variable between study sites and taxon richness was low across all sites. Oligochaetes, nematodes, ostracods and chironomids were the most common taxa found and were the most important in influencing differences between the macroinvertebrate assemblages among the study sites. Sediment grain size and chemical characteristics of the sediments (?PAH, ?PCB, TCDDeq and heavy metal concentrations) were important in separating the study sites based on taxon richness and abundance. Canonical correspondence analysis separated the macroinvertebrate assemblages at newly two created wetlands from those at other study sites including the urban reference sites. Increased sediment POP contamination (particularly as measured TCDDeq and ?DDT concentrations) is a likely contributor in excluding pollution sensitive taxa and, therefore, alterations to benthic macroinvertebrate assemblages. Further, the influence of TOC suggests the significance of catchment inputs in contributing to changes in macroinvertebrate assemblage. The SOP remediation led to the establishment of wetlands with benthic communities representative of those expected in urban wetlands. PMID:20857194
Rawson, Christopher A; Lim, Richard P; Tremblay, Louis A; Warne, Michael St J; Ying, Guang-Guo; Laginestra, Edwina; Chapman, John C
The combined analysis of neodymium (Nd) isotopes and radiocarbon (14C) in sedimentary benthic foraminifera has the potential to remedy a major issue involved in the interpretation of 14C data. The problem is that changes in deep-water sourcing, deep-water source signature and deep-water renewal rates may all affect 14C concentration, complicating the interpretation of deep-water 14C reconstructions. To overcome this, the application of a circulation tracer is required. Traditional proxies such as ?13C, Cd/Ca, and deep-water temperature either do not behave as conservative tracers or only indirectly represent water mass mixing, and so are of limited use1. The application of a more recently developed proxy for water mass sourcing, circulation and mixing, Nd isotopes, might offer a solution to this problem. A recent pioneering study2 has demonstrated that sedimentary benthic foraminifera might be a suitable archive of past deep-water Nd isotope composition at high resolution, potentially more robust than acidic-reductive sediment leach data. This study seeks to utilise this promising new tracer by applying it to an investigation of deglacial ventilation changes in the North Atlantic. Initial data presented here for core-top benthic foraminifera from the Labrador Sea, Iberian Margin and Pacific illustrate nearly the complete dynamic range of Nd isotope compositions present in the modern ocean, in general agreement with existing seawater Nd isotope data. Preliminary down-core Nd isotope data from the Iberian Margin place initial constraints on the contribution of deep-water sourcing to observed changes in deep-water 14C ventilation across the last deglaciation. 1 - E. Boyle, Ann. Rev. Earth Planet. Sci. 20, 245-287 (1992) 2 - V. Klevenz et al., Earth Planet. Sci. Lett. 265, 571-587 (2008)
Ocean acidification is a threat to marine ecosystems globally. In shallow-water systems, however, ocean acidification can be masked by benthic carbon fluxes, depending on community composition, seawater residence time, and the magnitude and balance of net community production (pn) and calcification (gn). Here, we examine how six benthic groups from a coral reef environment on Heron Reef (Great Barrier Reef, Australia) contribute to changes in seawater aragonite saturation state (?a). Results of flume studies showed a hierarchy of responses across groups, depending on CO2 level, time of day and water flow. At low CO2 (350-450 ?atm), macroalgae (Chnoospora implexa), turfs and sand elevated ?a of the flume water by around 0.10 to 1.20 h-1 - normalised to contributions from 1 m2 of benthos to a 1 m deep water column. The rate of ?a increase in these groups was doubled under acidification (560-700 ?atm) and high flow (35 compared to 8 cm s-1). In contrast, branching corals (Acropora aspera) increased ?a by 0.25 h-1 at ambient CO2 (350-450 ?atm) during the day, but reduced ?a under acidification and high flow. Nighttime changes in ?a by corals were highly negative (0.6-0.8 h-1) and exacerbated by acidification. Calcifying macroalgae (Halimeda spp.) raised ?a by day (by around 0.13 h-1), but lowered ?a by a similar or higher amount at night. Analyses of carbon flux contributions from four different benthic compositions to the reef water carbon chemistry across Heron Reef flat and lagoon indicated that the net lowering of ?a by coral-dominated areas can to some extent be countered by long water residence times in neighbouring areas dominated by turfs, macroalgae and potentially sand.
Anthony, K. R. N.; Diaz-Pulido, G.; Verlinden, N.; Tilbrook, B.; Andersson, A. J.
Holistic rates of excess organic carbon production (E) and calcification for a 0.5 km2 segment of the backreef platform of the northern Florida reef tract (NFRT) were estimated by combining biotope mapping using remote sensing with community metabolic rates determined with a benthic incubation system. The use of ASTER multispectral satellite imaging for the spatial scaling of benthic metabolic processes resulted in errors in E and net calcification (G) of 48 and 431% respectively, relative to estimates obtained using AISA hyperspectral airborne scanning. At 19 and 125%, the E and G errors relative to the AISA-based estimates were less pronounced for an analysis that used IKONOS multispectral satellite imagery to spatially extrapolate the chamber process measurements. Our scaling analysis indicates that the holistic calcification rate of the backreef platform of the northern Florida reef tract is negligible at 0.07 g CaCO3 m-2 d-1. All of the mapped biotopes in this reef zone are net heterotrophic, resulting in an estimated holistic excess production rate of -0.56 g C m-2 d -1, and an overall gross primary production to respiration ratio of 0.85. Based on our finding of ubiquitous heterotrophy, we infer that the backreef platform of the NFRT is a sink for external inputs of suspended particulate organic matter. Further, our results suggest that the inward advection of inorganic nutrients is not a dominant forcing mechanism for benthic biogeochemical function in the NFRT. We suggest that the degradation of the northern Florida reef tract may parallel the community phase shifts documented within other reef systems polluted by organic detritus. ?? Inter-Research 2006.
Brock, J. C.; Yates, K. K.; Halley, R. B.; Kuffner, I. B.; Wright, C. W.; Hatcher, B. G.
This article presents an in situ treatment method for retardation of phosphate release from freshwater benthic sediments. The method is based on the addition of ocher pellets into benthic sediments. The pellets consist of ocher and calcium nitrate (OCN pellet). The OCN pellet slowly releases calcium and nitrate, together with ocher, into the sedimentwater interface, where all three components play
Five lotic systems of Serra do Cipó, south-east Brazil, were investigated in order to assess the existing diversity of benthic macroinvertebrates, habitats-microhabitats, and the available trophic resources. For each river it was analysed the communities of benthic macroinvertebrates and the com- position of some taxonomic groups (Plecoptera, Ephemeroptera, Trichoptera and Diptera Chirono- midae): the community with Bivalvia Sphaeriidae, Oligochaeta and
The National Coastal Assessment has sampled benthic assemblages each summer since 2000 in coastal areas of the U.S. Acadian Biogeographic Province (tip of Cape Cod to Canadian border). We are developing a multimetric index to be used as an indicator of benthic condition. During...
The National Coastal Assessment has sampled benthic assemblages each summer since 2000 in coastal areas of the U.S. Gulf of Maine. We are developing a multimetric index to be used as an indicator of benthic condition for both spatial comparisons of condition along the coast and f...
The objective of this study was to evaluate the effect of agricultural pollution on periphyton in streams and rivers of southern Québec. We sampled benthic algae incubated from mid-July to mid-August on artificial substrates at 29 sites and analysed the variations in community structure and total community biomass. Diatom community structure as well as total benthic algae community were analysed.
Isabelle Lavoie; Warwick F. Vincent; Reinhard Pienitz; Jean Painchaud
The standard EPA West Coast Environmental Monitoring and Assessment Program (EMAP-W) benthic macrofaunal sampling protocol is to collect 30-50 random benthic samples per reporting unit (e.g., estuary, region) using a 0.1 m2 grab and to sort out macrofauna using a 1.0 mm mesh scre...
Utilization of Computer-aided-Tomography (CT) technology is a powerful tool to investigate benthic communities in aquatic systems. In this presentation, we will attempt to summarize our 15 years of experience in developing specific CT methods and applications to marine benthic co...
The standard benthic macrofaunal sampling protocol in the U.S. Environmental Protection Agency's Pacific Coast Environmental Monitoring and Assessment Program (EMAP) is to collect a minimum of 30 random benthic samples per reporting unit (e.g., estuary) using a 0.1 m2 grab and to...
Microcystis is a microcystin-producing cyanobacterium known to proliferate in the water column of freshwater ecosystems, and to overwinter in the sediment. In this study, we demonstrate that microcystins can remain present in benthic cells buried in the sediment for long periods, and suggest that Microcystis is able to produce microcystins throughout its benthic survival. We investigated the viability and ability
Benjamin Misson; Marion Sabart; Christian Amblard; Delphine Latour
Sampling small benthic and lithophilic fish species in large rivers and lakes presents challenges not adequately addressed by conventional survey methods such as boat electrofishing and gill netting. The development of the Missouri trawl has helped to address these issues; however, our observations by scuba diving when using the Missouri trawl have revealed avoidance of the trawl by benthic fishes,
Jonathan A. Freedman; Timothy D. Stecko; Benjamin D. Lorson; Jay R. Stauffer Jr
SUMMARY 1. Anthropogenic activities have increased reactive nitrogen availability, and now many streams carry large nitrate loads to coastal ecosystems. Denitrification is potentially an important nitrogen sink, but few studies have investigated the influence of benthic organic carbon on denitrification in nitrate-rich streams. 2. Using the acetylene-block assay, we measured denitrification rates associated with benthic substrata having different proportions of
CLAY P. A RANGO; L. T ANK; J AMIE L. S CHALLER; TODD V. R OYER
Omnivory is omnipresent in natural communities. However, most theoretical models predict that omnivory should be rare, especially at high basal productivity. To address this incongruity, we consider as an example benthic food webs with omnivory. We present a mathematical analysis of simple benthic food webs in which a number of mechanisms promote persistence of omnivory. As a model system, we
Reinier HilleRisLambers; Johan van de Koppel; Peter M. J. Herman
The seabed community provides a sensitive litmus for environmental change. North Sea analysis of benthic populations provides an effective means for monitoring impacts from man's interventions, such as offshore oil exploitation and fishing, against baseline knowledge of the environment. Comparable knowledge of the benthic biology in the deep waters of the Atlantic Frontier beyond the N.E. Atlantic shelf edge is
Los Angeles-Long Beach Harbors were a grossly polluted body of water at the time of initiation of benthic invertebrate studies in 1951. Waste discharges included industrial, domestic and storm waters which received little or no treatment. The inner harbor water mass contained little or no dissolved oxygen, but the outer harbor was well oxygenated. Benthic conditions were characterized by four
In October 1987, there was extensive mortality of benthic organisms in relatively shallow water areas of the inner part of the Gullmarsfjord on the Swedish west coast, probably caused by low oxygen levels. Benthic disturbance caused by a continuation of hypoxia was also seen in J...
ABSTRACT We sampled benthic macroinvertebrates above and below a point source effluent in La Tordera stream (NE, Spain) over 2001?2002 to assess the effects of nutrient enrichment on the structure, and taxonomic composition of the benthic macroinvertebrate community. Below the point source, discharge, specific conductance and nutrient concentrations were higher than at the upstream reach, while dissolved oxygen (DO) decreased.
The assumption that water pollution causes a depression in the diversity of benthic macroinvertebrates as measured by the Shannon index and similar diversity indices is questioned. An interpretation of the community response of benthic macroinvertebrates to pollution in the Millers River, Massachusetts is developed from species presence-absence and abundance data in conjunction with published information on the species' environmental tolerances
Although the study of lakes has traditionally focused on pelagic production pathways, recent stable isotope and diet evidence indicates that benthic algal production is an important contributor to fish production. This has led to the suggestion that energy may be more efficiently passed along benthic food chains relative to their pelagic counter- parts. To test this idea, we combined stable
M. Jake Vander Zanden; Sudeep Chandra; Sang-Kyu Park; Yvonne Vadeboncoeur; Charles R. Goldman
Variations in oceanic primary productivity, flux of organic carbon to the sediments, and dissolved-oxygen levels in the water column are thought to be important in the control of benthic foraminiferal test size, wall thickness, morphology, and species composition of assemblages by many foraminiferal paleontologists. Aspects of these processes should be reflected by the benthic foraminiferal oxygen index (BFOI) based on
This study presents: (1) basic data on the benthic fauna and surface sediments of the nearshore zone of Panama City Beach, Fla., before restoration of the beach, and (2) the results of a study on the effect of Hurricane Eloise on the benthic fauna in the ...
Human exploitation of intertidal marine invertebrates is known to alter benthic community structure. This study describes the impact that harvesting by women and children has on the intertidal community structure of the mudflats of the Saco on Inhaca Island, Mozambique, by comparing the benthic communities of exploited and unexploited areas. Sampling was done using two different methods: a standard core
Five laboratory studies of benthic macroinvertebrate recolonization were conducted for 6-wk periods to evaluate the effects of physical factors (i.e., microcosm size, seawater flow rates and sediment depth) on benthic community structure. esign variables included4 open-faced acry...
By applying discriminant analysis to benthic macroinvertebrate data, we have developed an indicator of benthic condition for northern Gulf of Mexico estuaries. The data used were collected by the United States Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) in the Louisianian Province from 1991 to 1994. This benthic index represents a linear combination of the following weighted parameters: the proportion of expected species diversity, the mean abundance of tubificid oligochaetes, the percent of total abundance represented by capitellid polychaetes, the percent of total abundance represented by bivalve mollusks, and the percent of total abundance represented by amphipods. We successfully validated and retrospectively applied the benthic index to all of the benthic data collected by EMAP in the Louisianian Province. This benthic index was also calculated for independent data collected from Pensacola Bay, Florida, in order to demonstrate its flexibility and applicability to different estuarine systems within the same biogeographic region. The benthic index is a useful and valid indicator of estuarine condition that is intended to provide environmental managers with a simple tool for assessing the health of benthic macroinvertebrate communities.
The authors performed chemical analyses of heavy metals in water and periphyton, toxicity tests with Daphnia magna and an indigenous mayfly (Deleatidium sp.), and field surveys of benthic macroinvertebrates to estimate the degree of metal pollution in three catchments in the Coromandel Peninsula of New Zealand. Good agreement was found between toxicity tests and measures of benthic community structure, particularly
Sixty streams in northern Sweden were sampled for benthic macroinvertebrates in spring and autumn of 2000 as part of the European Union project AQEM (the Development and Testing of an Integrated Assessment System for the Ecological Quality of Streams and Rivers throughout Europe using Benthic Macroinvertebrates). Samples were taken using a harmonised multi-habitat sampling procedure and a large number of
It is well established that benthic invertebrate community structure and function shift in a predictable fashion along longitudinal stream gradients as a result of variation in environmental conditions. The authors research is concerned with experimentally testing whether this shift in community structure influences the response of benthic macroinvertebrates to heavy metals. Using artificial streams, they compared effects of Zn on
Changes of the benthic Microcystis community during the time of reinvasion and its influence on the planktonic inoculum were investigated in a laboratory experiment and in a shallow lake (Quitzdorf Reservoir, Germany). Reinvasion was quantified by the diminution of benthic Microcystis abundance, and moreover, by the increase of Microcystis in the water column. Laboratory investigations revealed that the migration of
Katja Schöne; Sabine Jähnichen; Tilo Ihle; Frank Ludwig; Jürgen Benndorf
Several organic contaminants in sewage effluent have been shown to elicit an estrogenic response in juvenile fish. Comparatively little emphasis has been placed on assessing these effects in marine invertebrates, particularly benthic organisms inhabiting sediment where lipophilic contaminants tend to persist. The present study examined reproductive effects in the benthic crustacean Leptocheirus plumulosus exposed to sewage-impacted sediment from Jamaica Bay,
The role of benthic micro-algae, primary producers on the intertidal areas of the Oosterschelde, has been studied during 1985 to 1986. To quantify benthic primary production microscale measurements of oxygen production and pH were performed in situ. Five ...
S. A. De Jong P. A. G. Hofman A. J. J. Sandee E. J. Wagenvoort
The diagnostic capability of changes in the benthic macroinvertebrate community composition to determine the cause in contaminated sediments were addressed using box core mesocosms subjected to cadmium, atrazine and nutrient enrichment. Intact cores of lake sediment were collected from Lake Erie at four occasions during 1996 and were returned to laboratory where they were maintained and manipulated. The benthic community
Bottom trawling causes widespread disturbance of sediments in shelf seas and can have a negative impact on benthic fauna. We conducted a large-scale assessment of bottom trawl fishing of benthic fauna in different habitats, using a theoretical, size-based model that included habitat features. Species richness was estimated based on a generalized body mass versus species richness relationship. The model was
J. G. Hiddink; S. Jennings; M. J. Kaiser; A. M. Queiros; D. E. Duplisea; G. J. Piet
A study of the response of benthic communities exposed to pentachlorophenol (PCP) was conducted to obtain additional information on the effects of this widely used chemical on the estuarine environment and to compare its effect on estuarine benthic communities developed in the fi...
SUMMARY 1. Fish can play an important role in coupling benthic and pelagic habitats by consuming benthic prey and providing essential nutrients to algae in dissolved form. However, little is known about the factors affecting the magnitude of this nutrient subsidy. 2. Using laboratory and mesocosm experiments we evaluated how varying ingestion rates of bluegill sunfish (Lepomis macrochirus) affects fish
Six species of benthic diatoms and a natural benthic diatom community were cultured in flasks on a variety of sediments. Diatom species which secreted large quantities of mucilage were effective sediment stabilizers. These mucilage-secreting species significantly reduced resuspension and retarded laminar flow of the sediments when the culture flasks were agitated. Diatom species which secreted little or no mucilage were
We show that robust regressions can be established between relative sea-level (RSL) data and benthic foraminifera oxygen isotopic ratios from the North Atlantic and Equatorial Pacific Ocean over the last climatic cycle. We then apply these regressions to long benthic isotopic records retrieved at one North Atlantic and one Equatorial Pacific site to build a composite RSL curve, as well
C. Waelbroeck; L. Labeyrie; E. Michel; J. C. Duplessy; J. F. McManus; K. Lambeck; E. Balbon; M. Labracherie
Cold-water coral ecosystems dominated by the species Lophelia pertusa and Madrepora oculata, as well as cold-water coral carbonate mounds (fossils and/or active) occur worldwide and are especially developed along the European margin, from northern Norway to the Gulf of Cadiz and into the Alboran Sea. Their discovery is a major achievement of the last few decades and their widespread occurrence presents a challenge to understand their development, preservation and possible importance in the geologic record. On the Norwegian shelf active/living reefs are developed on elevated hard substrata. Along the Irish margin L. pertusa builds large fossil and/or active carbonate mounds. In the Gulf of Cadiz and in the Alboran Sea buried reefs and patch reefs are generally found in association with mud volcanoes. In modern oceans, they provide important ecological niches for the marine benthic fauna in the deep-sea. In comparison to the macrofauna the microfauna, particularly the foraminifera associated to these systems, are poorly known. We present here a detailed study based on quantitative analyses of benthic and planktonic foraminifera together with the statistical treatment of assemblage data collected along the Norwegian margin, in the Porcupine-Rockall region and in the Alboran Sea. The three regions were and/or are site of cold-water coral ecosystems settlements. Our study reveals that in the Porcupine/Rockall region benthic foraminiferal assemblages are strictly related to the distribution of facies. On the Norwegian margin, benthic foraminiferal habitats are weakly defined and grade one into the other preventing the sharp facies separation observed along the Irish margin (Margreth et al., 2009). In the Alboran Sea cold-water coral ecosystems and cold-water carbonate mounds are presently buried and corals are generally fragmented. However, benthic assemblages from coral-rich layers in the Alboran Sea and those from Porcupine/Rockall and Norway show remarkable similarities. In particular, epifaunal-attached species such as Discanomalina coronata, Cibicides refulgens, and Lobatula lobatula dominate the assemblages with D. coronata restricted to living cold-water coral reefs facies only and/or in co-occurrence with coral fragments. In conclusion, our data suggest that although cold-water coral ecosystems occur at different latitudes, the associated foraminiferal assemblages are consistent from Norway to the Western Mediterranean. Thus they can be used to identify these ecosystems even in the geologic record, when the corals are often strongly dissolved like in the Alboran Sea. References: Margreth, S., Rüggeberg, A. and Spezzaferri, S., 2009. Benthic foraminifera as bioindicator for cold-water coral reef ecosystems along the Irish margin. Deep Sea Res. Part I, 56: 2216-2234. This study is funded by the Swiss National Foundation Projects 200020-117928 and 200021-111694.
The University of Connecticut has a tremendous collection of algae from the Long Island Sound, and back in 2001 they went ahead and photographed the original herbarium sheets featuring the preserved algae specimens. The archive is quite comprehensive, as it features all of the benthic marine macroalgal species in the Long Island Sound. All told, there are over 299 images here, and visitors are encouraged to peruse the collection by phylum, family, or name. The site also contains a list of definitions, a regional map, and information about the team that worked to make this collection a possibility.
Surveys of marine benthic macro-algae were made at two study areas receiving thermal effluents from power plants. A third, at an area where a natural thermal gradient exists, was investigated for comparison. Ordination analysis of the algal communities indicated changes in species composition of about 10% for each degree of temperature change up to 3/sup 0/C. Temperatures 7/sup 0/C above ambient altered the algal community by eliminating the large phaeophytes. Temperatures 10/sup 0/C above ambient left only a species-poor community of ephemeral populations.
The influence of benthic prey availability on growth of black crappies Pomoxis nigromaculatus is poorly understood due to scant research on the relationships between benthic prey abundance and composition and black crappie diet. However, benthic taxa play an important role as prey items of black crappies during intermediate ontogenetic diet phases. We evaluated diet, growth, and abundance of black crappies
This study was designed to assess trends in physical habitat and benthic communities (macroinvertebrates) annually in two agricultural streams (Del Puerto Creek and Salt Slough) in California's San Joaquin Valley from 2001 to 2005, determine the relationship between benthic communities and both water quality and physical habitat from both streams over the 5-year period, and compare benthic communities and physical
One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic
J.-P. Gattuso; B. Gentili; C. M. Duarte; J. A. Kleypas; J. J. Middelburg; D. Antoine
One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic
J.-P. Gattuso; B. Gentili; C. M. Duarte; J. A. Kleypas; J. J. Middelburg; D. Antoine
Temporal changes of biomass and dominant species in benthic algal communities were investigated in a littoral sand-beach zone in the north basin of Lake Biwa from December 1999 to September 2000. Chlorophyll- a amounts of benthic algal communities per unit area of the sandy sediments rapidly increased from late April to June. Increases in biomass of the benthic algal communities
The role of benthic sandy ecosystems in mitigating NO3? loads carried by Submarine Groundwater Discharge (SGD) to coastal marine ecosystems is uncertain. Benthic biogeochemical mediation of NO3?-rich submarine groundwater discharge was studied at the seepage face of a barrier island site in the Ria Formosa coastal lagoon (Southern Portugal). Preliminary analysis of NO3? porewater distributions at the seepage face during discharge indicated that benthic biogeochemical processes could significantly affect the fluxes of groundwater-borne NO3? into the lagoon. In order to discriminate between the relative contribution of transport and reaction processes to shape and concentration range evidenced by in-situ porewater NO3? gradients, an advection-dispersion-reaction (ADR) model of NO3? diagenesis was applied to describe NO3? porewater profiles obtained in March, June, September and December 2006. Good agreement between modeled and measured profiles was obtained. Model-derived apparent benthic nitrification and NO3? reduction rates ranged from 0.01 to 5.2 mmol m?2 h?1, sufficient to explain gross observed changes in NO3? fluxes arriving at the seepage face (up to 70% within the surficial 20 cm depth layer). Results of the analysis indicated that the upper limit of the seepage face promoted mitigation of NO3? fluxes to the lagoon throughout the year. In contrast, the lower limit of the seepage area promoted net amplification of the NO3? fluxes into the lagoon in June and September. These results will help constrain further work aiming to clarify the role of permeable sediments in mitigating nitrogen loading of coastal ecosystems.
Ibánhez, J. Severino P.; Leote, Catarina; Rocha, Carlos
The effects of climate change on Arctic marine ecosystems and their biogeochemical cycles are difficult to predict given the complex physical, biological and chemical interactions among the ecosystem components. We studied benthic biogeochemical fluxes in the Arctic and the influence of short-term (seasonal to annual), long-term (annual to decadal) and other environmental variability on their spatial distribution to provide a baseline for estimates of the impact of future changes. In summer 2009, we measured fluxes of dissolved oxygen, nitrate, nitrite, ammonia, soluble reactive phosphate and silicic acid at the sediment-water interface at eight sites in the southeastern Beaufort Sea at water depths from 45 to 580 m. The spatial pattern of the measured benthic boundary fluxes was heterogeneous. Multivariate analysis of flux data showed that no single or reduced combination of fluxes could explain the majority of spatial variation, indicating that oxygen flux is not representative of other nutrient sink-source dynamics. We tested the influence of eight environmental parameters on single benthic fluxes. Short-term environmental parameters (sinking flux of particulate organic carbon above the bottom, sediment surface Chl a) were most important for explaining oxygen, ammonium and nitrate fluxes. Long-term parameters (porosity, surface manganese and iron concentration, bottom water oxygen concentrations) together with ?13Corg signature explained most of the spatial variation in phosphate, nitrate and nitrite fluxes. Variation in pigments at the sediment surface was most important to explain variation in fluxes of silicic acid. In a model including all fluxes synchronously, the overall spatial distribution could be best explained (57%) by the combination of sediment Chl a, phaeopigments, ?13Corg, surficial manganese and bottom water oxygen concentration. We conclude that it is necessary to consider long-term environmental variability along with rapidly ongoing environmental changes to predict the flux of oxygen and nutrients across Arctic sediments even at short timescales. Our results contribute to improve ecological models predicting the impact of climate change on the functioning of marine ecosystems.
Link, H.; Chaillou, G.; Forest, A.; Piepenburg, D.; Archambault, P.
We describe a safe and effective apparatus for washing and reducing the volume of benthic samples collected by grab samplers aboard ship. The sample is transferred directly from the dredge to the apparatus and then washed with water pumped through pipes in the apparatus and from onboard hoses. Wastewater and materials smaller than 0.541 mm in diameter are washed overboard. Larger materials, including benthic organisms, collect on an upper 0.64-cm screen and on a lower 30-mm-mesh stainless steel bolt cloth. A collection jar is screwed into the bottom of the apparatus. Therefore, transfer of sample material from the apparatus to the jar is quick and easy. This apparatus has several advantages for use aboard ship over others described in the literature, especially in rough seas, in cold weather, and at night. The apparatus provides a safe and convenient platform for washing and reducing samples, and samples can be prepared while the vessel is traveling at full speed.
Pepper, Phillip N.; Girard, Thomas L.; Stapanian, Martin A.
Low dissolved oxygen (hypoxia and/or anoxia) has become a major cause of change to the benthic component of ecosystems around the world. We present the response of a benthic community to hypoxia in organically enriched environments in Korean coastal waters. Disturbances due to low dissolved oxygen (DO), and organic enrichment altered community dynamics, result in defaunation during summer hypoxia with delayed recolonization occurring in winter. As DO decreased, the number of taxa, their abundance and biomass of macrofauna dropped significantly at inner bay stations in Chinhae Bay and Youngsan River estuarine bay affected by hypoxia. With the return of normoxic conditions in Chinhae Bay, recolonization was initiated by opportunistic species, with a 1-4months lag. The polychaetes, Sigambra tentaculata, Mesochaetopterus sp., and Lumbrineris longifolia, were most persistent under hypoxia. The first recolonizers were the polychaetes Paraprionospio pinnata, S. tantaculata, Glycinde gurjanovae and Nectoneanthes multignatha and the bivalve Theora fragilis. The second group of colonizers included the polychaetes Capitella capitata, Mesochaetopterus sp. and L. longifolia, and the bivalve Raetellops pulchella. Hypoxic and near anoxic conditions resulted in mass mortality in Chinhae Bay and Youngsan River estuarine bay, but communities did partially recover after return to normoxic conditions despite delayed recolonization. PMID:16860829
Lim, Hyun-Sig; Diaz, Robert J; Hong, Jae-Sang; Schaffner, Linda C
The community structure of sedentary organisms is largely controlled by the outcome of direct competition for space. Understanding factors defining competitive outcomes among neighbors is thus critical for predicting large-scale changes, such as transitions to alternate states within coral reefs. Using a spatially explicit model, we explored the importance of variation in two spatial properties in benthic dynamics on coral reefs: (1) patterns of herbivory are spatially distinct between fishes and sea urchins and (2) there is wide variation in the areal extent into which different coral species can expand. We reveal that the size-specific, competitive asymmetry of corals versus fleshy algae highlights the significance of spatial patterning of herbivory and of coral growth. Spatial dynamics that alter the demographic importance of coral recruitment and maturation have profound effects on the emergent structure of the reef benthic community. Spatially constrained herbivory (as by sea urchins) is more effective than spatially unconstrained herbivory (as by many fish) at opening space for the time needed for corals to settle and to recruit to the adult population. Further, spatially unconstrained coral growth (as by many branching coral species) reduces the number of recruitment events needed to fill a habitat with coral relative to more spatially constrained growth (as by many massive species). Our model predicts that widespread mortality of branching corals (e.g., Acropora spp) and herbivorous sea urchins (particularly Diadema antillarum) in the Caribbean has greatly reduced the potential for restoration across the region. PMID:22009340
Habitat heterogeneity is considered an important mechanism influencing diversity patterns in spatially structured habitats. However, spatial heterogeneity is not static and it can change along temporal scales. These changes, whether gradual or rapid, have the potential of forcing species extinctions or facilitating the introduction of nonnative species. Here, we present modeling results that show how changes in spatial heterogeneity over several generations can produce strong changes in benthic species composition residing in eastern Long Island Sound, USA. For many benthic species, hard substrate is a limiting resource which can vary in availability among different coastal areas. We modeled gradual changes from a heterogeneous landscape (mimicking patches of natural hard and soft substrate) to a homogenous one (analogous to a fully developed coast with hard, manmade substrate) and followed the abundance and distribution patterns of species possessing four different life histories. We also modeled changes from homogeneous to heterogeneous landscapes. We found that as regions become more homogeneous, species extinctions become more frequent and poor dispersers dominate locally. In contrast, as habitats become more heterogeneous, species distributing across localities leads to regional species coexistence and fewer extinctions. These results suggest that focusing on changing habitat heterogeneity can be a useful management strategy to prevent poor dispersing species, such as invasive ascidians, from driving communities to monocultures. PMID:21639055
Munguia, Pablo; Osman, Richard W; Hamilton, John; Whitlatch, Robert; Zajac, Roman
Despite its often featureless appearance, the deep-ocean floor includes some of the most diverse habitats on Earth. However, the accurate assessment of global deep-sea diversity is impeded by a paucity of data on the geographical ranges of bottom-dwelling species, particularly at the genetic level. Here, we present molecular evidence for exceptionally wide distribution of benthic foraminifera, which constitute the major part of deep-sea meiofauna. Our analyses of nuclear ribosomal RNA genes revealed high genetic similarity between Arctic and Antarctic populations of three common deep-sea foraminiferal species (Epistominella exigua, Cibicides wuellerstorfi and Oridorsalis umbonatus), separated by distances of up to 17, 000 km. Our results contrast with the substantial level of cryptic diversity usually revealed by molecular studies, of shallow-water benthic and planktonic marine organisms. The very broad ranges of the deep-sea foraminifera that we examined support the hypothesis of global distribution of small eukaryotes and suggest that deep-sea biodiversity may be more modest at global scales than present estimates suggest. PMID:17725572
Accurate measurement of coral reef community metabolism is a necessity for process monitoring and in situ experimentation on coral reef health. Traditional methodologies used for these measurements are effective but limited by location and scale constraints. We present field trial results for a new benthic chamber system called the Submersible Habitat for Analyzing Reef Quality (SHARQ). This large, portable incubation system enables in situ measurement and experimentation on community- scale metabolism. Rates of photosynthesis, respiration, and calcification were measured using the SHARQ for a variety of coral reef substrate types on the reef flat of South Molokai, Hawaii, and in Biscayne National Park, Florida. Values for daily gross production, 24-h respiration, and net calcification ranged from 0.26 to 6.45 g O2 m-2 day-1, 1.96 to 8.10 g O2 m-2 24 h-1, and 0.02 to 2.0 g CaCO3 m -2 day-1, respectively, for all substrate types. Field trials indicate that the SHARQ incubation chamber is an effective tool for in situ isolation of a water mass over a variety of benthic substrate types for process monitoring, experimentation, and other applications.
Foraminiferal species exhibit a wide range of morphological characteristics, some of which are a reflection of the environment of their habitat. These ecophenotypic responses may provide a powerful clue to determining past depositional environments. In most morphologic studies of benthic foraminifera, relationships have been shown between test size and water depth and between surface sculpture and water depth. The authors applied an automated imaging system to examine the morphology of three species of Bolivina from the northwestern Gulf of Mexico. Two of the three species analyzed displayed clear relationships with test shape and water depth. Overall test shape appeared to be the most important discriminator of depth, but changes in the periphery (i.e., spinosity) of the foraminifera were also noted in one species. All of these results clearly indicate that the test shape of benthic foraminifera hold the possibility of providing facies information to paleontologists. Importantly, these results indicate that imaging techniques are capable of distinguishing changes in shape with depth. The quantification of these changes offers the possibility of precise and rapid depth determinations with an accuracy and resolution not possible with many other techniques.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
Measurements have been made over a period of seven months of currents and mixing near the seabed. The location of the study was in the N. Atlantic approximately midway between the islands of the Azores and Madeira. Currents were measured near the seabed in a water depth exceeding 5000m with moored internally-recording instruments. Maps of near bottom flow have been constructed and the dispersion of particles of water and therefore mixing of a tracer, such as radionuclide has been inferred. The research described in this report is concerned with a small part of the scientific assessment of the feasibility of the disposal of heat generating radioactive waste (HGW) into the deep sea environment.
This study shows that spatially and temporally recurring benthic macrofauna-habitat patterns validate the ecological relevance of habitat types to benthic macrofauna and suggest they can serve as elements in ecological periodic tables of benthic macrofaunal usage. We discovered patterns across nine habitat types (intertidal eelgrass [Zostera marina], dwarf eelgrass [Zostera japonica], oyster [Crassostrea gigas] ground culture, burrowing mud shrimp [Upogebia pugettensis], burrowing ghost shrimp [Neotrypaea californiensis], shell, sand, mud, and subtidal) on a variety of benthic macrofaunal community state variables in Grays Harbor, Washington, USA and compared them to those in Willapa Bay, Washington, USA. There were nominal differences in benthic macrofaunal Bray-Curtis similarity between all the habitats investigated except eelgrass and oyster in both estuaries. Across-habitat patterns on mean benthic macrofaunal species richness, abundance, biomass, abundance of deposit, suspension and facultative feeders, a dominance and a diversity index for the five habitats common to both studies were the same on a rank measurement scale: eelgrass ? oyster > mud shrimp > ghost shrimp ? subtidal. The patterns for most of the habitats and benthic macrofaunal measures were the same on a ratio measurement scale.
Allochthonous input provides important food and spatial resources for estuarine benthic fauna. While it is known that autochthonous materials are important for fauna occupying small marshes, here, we present the significance of allochthonous materials for benthic fauna inhabiting a large salt marsh. To assess the effects of allochthonous input on benthic macrofaunal communities in estuarine salt marshes, we determined the source of substrate sediments and food resource utilisation patterns of benthic invertebrates in 2 temperate estuaries (the Tama River and the Obitsu River estuarine outlets into Tokyo Bay) by using stable carbon and nitrogen isotope analyses. In the Tama River estuary, which has small patches of marsh vegetation upstream of the river mouth, there was an input of sedimentary organic matter from autochthonous sources (i.e. common reed and microphytobenthos). In the Obitsu River estuary salt marsh, which is situated immediately upstream of the river mouth and is well connected to the sea, sediment consists of allochthonous sources (i.e. imported phytoplankton), along with microphytobenthos. Isotope analysis indicated that most benthic invertebrates in the Tama River estuary depend on benthic microalgae (autochthonous) as a food resource, whereas the macrofauna in the Obitsu River estuary are supported by drift macroalgae (allochthonous), in addition to microphytobenthos or phytoplankton. Our results indicated that allochthonous material provides a food resource and potential habitat for benthic macrofauna in extensive salt marshes that have a strong connection to the sea but is not substantial in smaller marshes with limited connectivity to coastal water.
Toxicity-based sediment quality guidelines (SQGs) are often used to assess the potential of sediment contamination to adversely affect benthic macrofauna, yet the correspondence of these guidelines to benthic community condition is poorly documented. This study compares the performance of 5 toxicity-based SQG approaches to a new benthos-based SQG approach relative to changes in benthic community condition. Four of the toxicity-based SQG approaches--effects range median, logistic regression modeling (LRM), sediment quality guideline quotient 1 (SQGQ1), and consensus--were derived in previous national studies in the United States, and one was developed as a regional variation of LRM calibrated to California data. The new benthos-based SQG approach, chemical score index, was derived from Southern California benthic community data. The chemical-specific guidelines for each approach were applied to matched chemical concentration, amphipod mortality, and benthic macrofauna abundance data for Southern California. Respective results for each SQG approach were then combined into a summary metric describing the overall contamination magnitude (e.g., mean quotient) and assessed in accordance with a set of thresholds in order to classify stations into 4 categories of expected biological effect. Results for each SQG approach were significantly correlated with changes in sediment toxicity and benthic community condition. Cumulative frequency plots and effect category thresholds for toxicity and benthic community condition were similar, indicating that both types of effect measures had similar sensitivity and specificity of response to contamination level. In terms of discriminating among multiple levels of benthic community condition, the toxicity-based SQG indices illustrated moderate capabilities, similar to those for multiple levels of toxicity. The National LRM, California LRM, and the chemical score index had the highest overall agreement with benthic categories. However, only the benthos-based chemical score index was consistently among the highest performing SQG indices for all measures of association (correlation, percent agreement, and weighted kappa) for both toxicity and benthos. PMID:22275113
Ritter, Kerry J; Bay, Steven M; Smith, Robert W; Vidal-Dorsch, Doris E; Field, L Jay
Benthic nitrogen (N) cycling was investigated at six stations along a transect traversing the Peruvian oxygen minimum zone (OMZ) at 11°S. An extensive dataset including porewater concentration profiles and in situ benthic fluxes of nitrate (NO3-), nitrite (NO2-) and ammonium (NH4+) was used to constrain a 1-D reaction-transport model designed to simulate and interpret the measured data at each station. Simulated rates of nitrification, denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) by filamentous large sulfur bacteria (e.g. Beggiatoa and Thioploca) were highly variable throughout the OMZ yet clear trends were discernible. On the shelf and upper slope (80-260 m water depth) where extensive areas of bacterial mats were present, DNRA dominated total N turnover (?2.9 mmol N m-2 d-1) and accounted for ?65% of NO3- + NO2- uptake by the sediments from the bottom water. Nonetheless, these sediments did not represent a major sink for dissolved inorganic nitrogen (DIN = NO3- + NO2- + NH4+) since DNRA reduces NO3- and, potentially NO2-, to NH4+. Consequently, the shelf and upper slope sediments were recycling sites for DIN due to relatively low rates of denitrification and high rates of ammonium release from DNRA and ammonification of organic matter. This finding contrasts with the current opinion that sediments underlying OMZs are a strong sink for DIN. Only at greater water depths (300-1000 m) did the sediments become a net sink for DIN. Here, denitrification was the major process (?2 mmol N m-2 d-1) and removed 55-73% of NO3- and NO2- taken up by the sediments, with DNRA and anammox accounting for the remaining fraction. Anammox was of minor importance on the shelf and upper slope yet contributed up to 62% to total N2 production at the 1000 m station. The results indicate that the partitioning of oxidized N (NO3-, NO2-) into DNRA or denitrification is a key factor determining the role of marine sediments as DIN sinks or recycling sites. Consequently, high measured benthic uptake rates of oxidized N within OMZs do not necessarily indicate a loss of fixed N from the marine environment.
Bohlen, L.; Dale, A. W.; Sommer, S.; Mosch, T.; Hensen, C.; Noffke, A.; Scholz, F.; Wallmann, K.
When benthic shells occur in sufficiently large numbers, they can dominate acoustic backscattering by the seafloor, especially at angles of incidence away from normal. In order to use sound as a tool to remotely detect and quantify the shells, the scattering properties of the shells need to be understood, both in free-space as well as when placed on the seafloor. Through laboratory experimentation, it has been determined that the edges of certain types of shells (such as bivalves and sand dollars) can dominate the scattering over an important range of grazing angles. The surfaces of these shells and others dominate under other conditions. The dominant scattering effects are discussed in the context of interpreting acoustic backscatter data in terms of meaningful parameters such as numerical density of the shells.
Zooplankton show a unique pattern of evolution with successive waves of invasion into the water column from the benthos. We have found that 18 of 21 planktonic groups whose ancestry can be traced originated in the benthos. New recruits have survived and radiated if preadapted to remain in the plankton, but no major clades have evolved there (with the possible exception of some protists). The innovative steps into the planktic realm do not coincide with major global events such as mass extinctions. Recruitment into the plankton can occur either at the larval stage or in adulthood. No groups have returned to a benthic mode of life from a planktic one, except possibly some of the cnidarians. This unusual pattern of evolution, a one-way track into a particular environment, demonstrates the profound effect of the ecosystem on large-scale patterns and processes of evolution.
In April 2004, more than 40 hours of georeferenced submarine digital video was collected in water depths of 15-370 m in Glacier Bay to (1) ground-truth existing geophysical data (bathymetry and acoustic reflectance), (2) examine and record geologic characteristics of the sea floor, and (3) investigate the relation between substrate types and benthic communities, and (4) construct predictive maps of seafloor geomorphology and habitat distribution. Common substrates observed include rock, boulders, cobbles, rippled sand, bioturbated mud, and extensive beds of living horse mussels and scallops. Four principal sea-floor geomorphic types are distinguished by using video observations. Their distribution in lower and central Glacier Bay is predicted using a supervised, hierarchical decision-tree statistical classification of geophysical data.
Harney, Jodi N.; Cochrane, Guy R.; Etherington, Lisa L.; Dartnell, Pete; Golden, Nadine E.; Chezar, Hank
Two hundred twenty-nine species of benthic foraminifera have been identified from 96 stations representing 33 localities on the eastern Pacific inner continental shelf, ranging from southern Peru to northern Baja California. Their distributions mark nearshore provincial boundaries that are nearly identical with those previously documented from the distribution of ostracodes and molluscs. Thirteen species are characteristic of the Panamanian Province, one is characteristic of the Chilean-Peruvian Province, and one is characteristic of the newly proposed Sonoran Subprovince. Seventeen species (7%) appear to be endemic to the eastern Pacific. Fifty-eight (25%) of the species recognized are disjunct from population centers in the western Pacific, 134 species (59%) are disjunct from modern assemblages of the Atlanto-Carribean region, and 40 species (17%) are disjunct from both the western Pacific and the Atlanto-Caribbean. The distribution of the remaining 57 species (25%) is poorly documented; we classify them as of unknown origin. -Authors
The ocean floor is one of the main accumulation sites of marine debris. The study of this kind of debris still lags behind that of shorelines. It is necessary to identify the methods used to evaluate this debris and how the results are presented and interpreted. From the available literature on benthic marine debris (26 studies), six sampling methods were registered: bottom trawl net, sonar, submersible, snorkeling, scuba diving and manta tow. The most frequent method used was bottom trawl net, followed by the three methods of diving. The majority of the debris was classified according to their former use and the results usually expressed as items per unity of area. To facilitate comparisons of the contamination levels among sites and regions some standardization requirements are suggested. PMID:18082846
Matched chemical and ecological monitoring data were used to assess the effects of iron on benthic macroinvertebrate communities. Three measures of iron exposure: dissolved, total, and particulate iron were assessed. Ecological responses were normalised to an unimpacted reference condition to make site-specific predictions of the reference condition. Ecological data were expressed as an Ecological Quality Index (EQI), indicating quality relative to the reference condition. Quantile regression analysis was used to derive thresholds as an EQI value equivalent to the cut-off between good and moderate ecological status for water quality classification. Thresholds for Good Ecological Status ranged from 1.25 to 2.46 mg L?¹ depending on the measure of exposure and ecological response. PMID:21516455
Seven marine benthic crustaceans were exposed in 4 d water-only toxicity tests to five concentrations of fluoranthene. After exposures, mortality (LC50) and the ability to bury in clean sediment (EC50) were determined. Survivors were then exposed to UV radiation for 1 h. The differences between LC50s and EC50s before and after UV exposure were used to assess photoinduced toxicity. UV exposure enhanced fluoranthene toxicity by as much as tenfold in five of the seven species tested (Rhepoxynius abronius, Eohaustorius estuarius, Leptocheirus plumulosus, Grandidierella japonica, and Corophium insidiosum). Species having the greatest potential for natural exposure to sunlight (Excirolana vancouverensis and Emerita analoga) were the least sensitive to photoinduced fluoranthene toxicity. Although photoinduced toxicity needs to be considered in environmental risk assessments, testing should be done, using ecologically relevant species and exposures. PMID:9175504
Boese, B L; Lamberson, J O; Swartz, R C; Ozretich, R J
The turbulence associated with the vigorous bottom currents of the western North Atlantic maintains a nepheloidlayer with an average thickness of one kilometer. The layer covers the continental rise, abyssal plains and Bermuda Rise. On the average, a ten...
One predicted effect of global climate change, specifically global warming, is the increase in the temperatures and stratification of shallow coastal and estuarine systems. This, coupled with ongoing anthropogenic eutrophication, will exacerbate hypoxia and benthic mortalities, significantly damaging these critical marine ecosystems. These phenomena are particularly severe on sublitoral soft-bottoms such as the poorly sorted silty sands at the study site in the northern Adriatic Sea. We deployed a specially developed underwater chamber to artificially induce anoxia in situ. Our Experimental Anoxia Generating Unit (EAGU) is a large plexiglass chamber that combines a digital camera with oxygen/hydrogen sulphide/pH sensors along with flashes and battery packs. The unit can be deployed for up to five days to autonomously generate oxygen crises and quantify both physico-chemical parameters and benthic responses. The system is initially positioned in an "open" configuration (open-sided aluminium frame) over the benthic fauna ("control" experiment). After 24 h the EAGU is switched to its "closed" configuration (plexiglass enclosure) and repositioned over the same assemblage. In this contribution, we focus on the natural oxygen content, temperature and pH of bottom waters during summer, the course of oxygen decrease during our experiments and the onset of H2S development. Oxygen content of the bottom water, a few centimetres above the sediment-water interface, ranges from ~3.5-8 but is mostly between 4-6 ml l-1 during July to September of the study periods (2005 and 2006) and decreases to zero within ~1-3 days after initiation of our experiments. In parallel, H2S starts to develop at the onset of anoxia. Water temperatures at the bottom were stable during experiments and ranged from 18.5°C to 21.4°C, but pH decreased from 8.3 to 8.1 at the beginning to 7.9 to 7.7 at the end of the experiments. Sediment profiling indicates that the diffusive benthic boundary layer is approximately 2.5 mm thick and that oxygen values decrease from ~2 ml l-1 3.5 mm above the sediment water interface to virtually zero at the interface. PH-values in 2 mm depth decrease from 8.15 to 7.6 within the first 10 h of the experiment. This indicates that the most reactive organic matter is decomposing in the uppermost few mm of the sediment. These data can be related to behavioural responses and mortality sequences of benthic faunas, including echinoids, crustaceans, molluscs and anemones. Beginning hypoxia (?2.0 ml l-1 DO) elicited escape patterns such as increased horizontal and vertical locomotion of animals. Moderate hypoxia (?1.0 ml l-1 DO) triggered species-specific sublethal effects such as arm-tipping in ophiuroids or extension from the sediment in sea anemones. At severe hypoxia (?0.5 ml l-1 DO) infaunal organisms began to emerge and first mortalities occurred. Some crustaceans and echinoderms are among the first to die, but sea anemones and large gastropods can even survive the onset of hydrogen sulfide.
Zuschin, Martin; Riedel, Bettina; Stachowitsch, Michael; Cermelj, Branko
An expansive area of bottom-water hypoxia occurs annually during the summer on the Louisiana continental shelf (LCS). The formation of these hypoxic waters has been linked to spring Mississippi River nutrient loading. Inferred in this linkage is the remineralization of nutrients, in both the sediments and water-column, to support primary production (PP) across the LCS. Benthic-pelagic interactions also mediate bottom-water O2 concentrations and provide a nitrogen sink through production of N2. To investigate the role of benthic- pelagic coupling processes we measured water-column PP, sediment-water interface fluxes of nutrients, N2, O2, and DIC, and concentrations of biogeochemically active substrates in sediments across the LCS during 5 cruises spanning 2006 and 2007. Measurements of PP indicated that a substantial fraction of PP (25-50%) occurred below the pycnocline. Thus, N and P remineralized from the sediments were directly available to primary producers, even when the water-column was strongly stratified. Sediment N2 fluxes (range = 0.0-1.2 mmoles N2 m-2 d-1) indicated a large potential sink for Mississippi River N loads. Sediment oxygen consumption (SOC) rates (range = 0-24 mmoles O2 m-2 d-1) were dependent on bottom-water O2 concentrations (range = 13-135 mmoles O2 m-3). Total sediment metabolism rates, approximated from sediment DIC fluxes (range = 8-21 mmoles C m-2 d- 1), did not vary significantly across the LCS and were insensitive to changes in bottom-water O2 concentrations. The accumulation of reduced anaerobic end-products under conditions of low bottom-water O2 concentrations may be important in maintaining hypoxia through summer.
Lehrter, J.; Devereux, R.; Beddick, D.; Yates, D.; Murrell, M.; Hagy, J.; Kurtz, J.
Triclosan is an antimicrobial compound that has been widely used in consumer products such as toothpaste, deodorant, and shampoo. Because of its widespread use, triclosan has been detected in various environmental media, including wastewater, sewage sludge, surface waters, and sediments. Triclosan is acutely toxic to numerous aquatic organisms, but very few studies have been performed on estuarine and marine benthic organisms. For whole sediment toxicity tests, the sediment-dwelling estuarine amphipod, Ampelisca abdita, and the epibenthic mysid shrimp, Americamysis bahia, are commonly used organisms. In the present study, median lethal concentration values (LC50) were obtained for both of these organisms using water-only and whole sediment exposures. Acute 96-h water-only toxicity tests resulted in LC50 values of 73.4 and 74.3 µg/L for the amphipod and mysid, respectively. For the 7-d whole sediment toxicity test, LC50 values were 303 and 257 mg/kg (dry wt) for the amphipod and mysid, respectively. Using equilibrium partitioning theory, these whole sediment values are equivalent to interstitial water LC50 values of 230 and 190 µg/L for the amphipod and mysid, respectively, which are within a threefold difference of the observed 96-h LC50 water-only values. Triclosan was found to accumulate in polychaete tissue in a 28-d bioaccumulation study with a biota-sediment accumulation factor of 0.23 kg organic carbon/kg lipid. These data provide some of the first toxicity data for triclosan with marine benthic and epibenthic species while also indicating a need to better understand the effects of other forms of sediment carbon, triclosan ionization, and organism metabolism of triclosan on the chemical's behavior and toxicity in the aquatic environment. PMID:22605471
Perron, Monique M; Ho, Kay T; Cantwell, Mark G; Burgess, Robert M; Pelletier, Marguerite C
Three collecting trips were coordinated in April, May, and August 2006 to sample the water column and benthos of hypereutrophic Upper Klamath Lake (OR, USA) through the annual cyanophyte bloom of Aphanizomenon flos-aquae. A pore-water profiler was designed and fabricated to obtain the first high-resolution (centimeter-scale) estimates of the vertical concentration gradients of macro- and micronutrients for diffusive-flux determinations. A consistently positive benthic flux for soluble reactive phosphorus (SRP) was observed with solute release from the sediment, ranging between 0.4 and 6.1 mg/m(2)/d. The mass flux over an approximate 200-km(2) lake area was comparable in magnitude to riverine inputs. An additional concern related to fish toxicity was identified when dissolved ammonium also displayed consistently positive benthic fluxes of 4 to 134 mg/m(2)/d, again comparable to riverine inputs. Although phosphorus was a logical initial choice by water quality managers for the limiting nutrient when nitrogen-fixing cyanophytes dominate, initial trace-element results from the lake and major inflowing tributaries suggested that the role of iron limitation on primary productivity should be investigated. Dissolved iron became depleted in the lake water column during the course of the algal bloom, while dissolved ammonium and SRP increased. Elevated macroinvertebrate densities, at least of the order of 10(4) individuals/m(2), suggested that the diffusive-flux estimates may be significantly enhanced by bioturbation. In addition, heat-flux modeling indicated that groundwater advection of nutrients could also significantly contribute to internal nutrient loading. Accurate environmental assessments of lentic systems and reasonable expectations for point-source management require quantitative consideration of internal solute sources. PMID:18980391
Kuwabara, James S; Topping, Brent R; Lynch, Dennis D; Carter, James L; Essaid, Hedeff I
In contrast to clastic depositional environments, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 sediment samples (piston core top and grab) collected along two transverses approximately 25 km apart across the northern (windward) margin of Little Bahama Bank at depths of 275 to 1135 m. Most species exhibit great variation in abundance with depth. However, Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators (Spearman's r > 0.91; p < 0.005), being most abundant at depths > 1000 m, and correspond to lower slope (> 900 m) periplatform aprons. Individual foraminiferal suborders (Miliolina, Rotaliina, Textulariina) show no consistent depth-related trends. However, certain operational taxonomic groups, such as reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are significant more abundant at depths < 300 m (95% C.I.: 2.6 +/- 2.2% and 6.9 +/- 2.7%, respectively) than at greater depths (95% C.I.: 0.3 +/- 0.2% and 2.0 +/- 0.8%; Mann-Whitney U, p < 0.01), reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines (i.e., suborder Miliolina minus peneroplids and soritids) and rosalinids and discorbids (suborder Rotaliina) are also more abundant at depths < 300 m (95% C.I.: 27.5 +/- 7.4% and 32.6 +/- 8.5%, respectively) than at greater depths (95% C.I.: 10.0 +/- 3.9% and 1.5 +/- 1.6%; Mann-Whitney U, p < 0.01) and are winnowed from the carbonate platform. Assemblages exhibit greatest variation in diversity (species number, s; Shannon-Weaver, H'; evenness, J') at depths > 900 m; indices for shallower assemblages tend to be grouped more tightly at relatively high values.
This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of PAH mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for t...
This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of the insecticide endrin in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accoun...
This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of the insecticide dieldrin in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it acco...
An Intensified Environmental Monitoring and Assessment Program (EMAP) sampling grid in the St. Louis River estuary of western Lake Superior was used toassess the relationship between surficial sediment characteristics and benthic community structure. Ninety sites within two habit...
The community composition of benthic macroinvertebrates from 870 estuarine sites was examined to determine boundaries of biogeographical provinces along the Gulf of Mexico and western Atlantic coasts of the United States. Our objective was to confirm or challenge established boun...
The paper describes a qualitative and quantitative census of the inshore benthic fauna off southwest Long Island over the period February 1966 through January 1967, prior to construction of an ocean sewer outfall in the general vicinity. Preliminary analy...
Agricultural drainage ditches have large differences in hydroperiod and provide additional water residence time to mitigate farm runoff before it reaches receiving water bodies. These ditch wetland habitats harbor a characteristic benthic macroinvertebrate fauna reflective of the assimilative capac...
A survey of benthic habitats throughout Tampa Bay was conducted by the Tampa Bay National Estuary Program (TBNEP), the Environmental Protection Commission of Hillsborough County (EPCHC), and the Manatee County Environmental Action Commission (MCEAC) in Se...
Our study had two objectives. First, in order to quantify the potential underestimation of community respiration caused by the exclusion of anaerobic processes, we compared benthic microbial respiration measured as 02 consumption with estimated based on DHA. Second, our previous ...
Eutrophication-induced changes to benthic structure and function are problems of enormous ecological and economic significance. Understanding the relationships between nutrient enrichment and effects, modifying factors such as localized transport time, and symptoms of eutrophica...
One of the most significant problems produced by bottom deposits is the gradual depletion in water storage capacity. A portion of bottom sediments, termed benthic deposits, with specific gravity only slightly greater than water will eventually settle down...
The potential influence of polycyclic aromatic hydrocarbon (PAH) metabolism on bioaccumulation is well accepted, but rarely has been examined in many species of benthic invertebrates that commonly are found in contaminated sediments, or used in bioaccumulation or toxicity tests. ...
The article reports the results of an investigation to identify and map the major benthic communities in Puget Sound, to determine the distributional relationships among communities and environmental parameters, and to determine the ecologically significa...
The results of the research effort culminated in the development of a research method for assessing the chronic toxicity of contaminated marine and estuarine sediments using the benthic amphipod, Leptocheirus plumulosus. The first chapter describes the ef...
J. E. Sewall M. S. Redmond R. C. Swartz T. H. DeWitt
Estuarine benthic macroalgae are excellent producers of new carbonaceous material through their high rates of photosynthesis. Under some circumstances, this organic carbon is liberated into the aquatic environment in dissolved form while the plant is acti...
This study was designed to develop a system for using benthic macroinvertebrates as water quality indicators in a large deep river. The objectives were: (1) to develop reliable sampling techniques; (2) to determine whether pollution-stressed communities w...
A computer file of all published distributional data (presence or absence) on the recent, living and dead benthic foraminifera off the North American Pacific Coast (California and Baja California) was constructed from 89 papers published since 1896. Manip...
Although temporary rivers are widespread freshwater systems, they have been poorly studied by ecologists and are largely ignored in water management plans, practices and policies. If the effects of dry events on benthic invertebrates have been reported individually from different...
For more than two decades it has been recognized that benthic suspension feeders, by filtering particles out of the water,\\u000a may have a major impact on the overlying water column. Benthic suspension feeders comprise a large group of both passive and\\u000a active filter feeders, but only the impact of actively pumping macro-zoobenthic organisms will be dealt with. Of these are
Changes in the benthic infaunal community structure at a location in south-west Ireland subject to dredging impacts were studied. Dredging of a muddy-maerl matrix takes place with a seasonally varying frequency of 25 times per month. The benthic infauna at a currently dredged site was compared to a fallowed portion of the area, at which extraction ceased 6 months prior
Benthicpelagic coupling and the role of bottom-up versus top-down processes are recognized as having a major impact on the community structure of intertidal and shallow subtidal marine communities. Bottom-up processes, however, are still viewed as principally affecting the outcome of top-down processes. Sponges on coral reefs are important members of the benthic community and provide a crucial coupling between water-column
Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota) effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface) by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days) in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential), gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH(4)(+) and dissolved Si. Although effluxes of PO(4)(3-) were not altered significantly, changes were observed in sediment PO(4)(3-) sorption capability. The duration of hypoxia (i.e. number of days of stress) explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the benthic habitat matters, and that the link between biodiversity and ecosystem function is likely to be affected by a range of factors in complex, natural environments. PMID:23091592
In this work a non-parametric multivariate analysis was used to assess the impact of metals and organic compounds in the macro\\u000a infaunal component of the mollusks benthic community using surface sediment data from several monitoring programs collected\\u000a over 20 years in Salina Cruz Bay, Mexico. The data for benthic mollusks community characteristics (richness, abundance and\\u000a diversity) were linked to multivariate environmental
C. González-Macías; I. Schifter; D. B. Lluch-Cota; L. Méndez-Rodríguez; S. Hernández-Vázquez
Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota) effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface) by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days) in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential), gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH4+ and dissolved Si. Although effluxes of PO43? were not altered significantly, changes were observed in sediment PO43? sorption capability. The duration of hypoxia (i.e. number of days of stress) explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the benthic habitat matters, and that the link between biodiversity and ecosystem function is likely to be affected by a range of factors in complex, natural environments.
Different land uses affect the characteristics of a hydrographic basin, reflected in the river water quality, and consequently\\u000a affecting the aquatic biota. The benthic community closely reflects the alterations caused by different human activities.\\u000a In this study, the effects of different land uses were evaluated by analysis of the benthic community structure in streams\\u000a with urban, agricultural and pasturage influences,
Data on benthic macroinvertebrates of the northern Caspian Sea in 19801991 were collected by the Caspian Fishery Research\\u000a Institute. During the initial period of the water-level rise, the main trends in benthic macroinvertebrates were increases\\u000a in the biomass of the main groups and decreases in the relative abundance of species of Mediterranean origin. There was no\\u000a significant alteration in species
L. V. Malinovskaja; A. A. Filippov; V. F. Osadchikh; N. V. Aladin
Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal-microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal-microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments often is enhanced even more than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies revealed that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification-denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of nitrogen.
The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule). PMID:22952910
Ubertini, Martin; Lefebvre, Sébastien; Gangnery, Aline; Grangeré, Karine; Le Gendre, Romain; Orvain, Francis
The relative contribution of sediment food (e.g. organic matter, carbohydrates, proteins, C, N, polyunsaturated fatty acids) and environmental variables (e.g. oxygen, pH, depth, sediment grain size, conductivity) in explaining the observed variation in benthic macroinvertebrates is investigated. Soft bottom sediments, water and benthic macroinvertebrates were sampled in several water systems across The Netherlands. The variance partitioning method is used to
Edwin T. H. M. Peeters; Ronald Gylstra; Jose H. Vos
Sampling benthic macroinvertebrates in large rivers has several limitations, arising not only from the selectivity of traditional\\u000a sampling gears but also from difficulty in capturing organisms that inhabit the deeper zones and high current velocities.\\u000a Considering the importance of benthic macroinvertebrates as a food resource for fishes, the sampling restrictions in sediment\\u000a collection done by dredges, and the importance of
Daniel M. MaronezeTaynan; Taynan H. Tupinambás; Carlos B. M. AlvesFabio; Fábio Vieira; Paulo S. Pompeu; Marcos Callisto
Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata--Ochrophyta; Amansia rhodantha--Rhodophyta; Halimeda opuntia--Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h?¹ dm?²), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h?¹) and concomitant oxygen drawdown (0.16±0.05 µmol L?¹ h?¹ dm?²). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef microbial dynamics and biogeochemical parameters (i.e., DOC and oxygen availability, bacterial abundance and metabolism) in coral reef communities. PMID:22125645
Haas, Andreas F; Nelson, Craig E; Wegley Kelly, Linda; Carlson, Craig A; Rohwer, Forest; Leichter, James J; Wyatt, Alex; Smith, Jennifer E
We compared benthic invertebrate assemblages among headwater streams in several forest types in Japan. Forests were divided\\u000a into three clusters based on vegetation composition: old-growth broad-leaved forest, planted coniferous forest, and mixed\\u000a forest. The numbers of individuals and families and the diversity (Shannon-Wiener) of benthic invertebrate assemblages did\\u000a not differ significantly among the three forest clusters. However, principal components analysis
This is a review on benthic algae from streams situated above the tree line in the Alps. It integrates published and unpublished\\u000a data from alpine streams in Austria and in the Trento Province (Northern Italy). The main focus is on the structural and taxonomic\\u000a composition of benthic algae including macro- and micro-algae and their contribution to the epilithic biofilm and
Estimation of abundance or biomass of benthic invertebrates requires considerable effort to process samples. Consequently,\\u000a it has been suggested to process only organisms retained by a relatively coarse meshed sieve and apply size-specific correction\\u000a factors based on the probability that a sieve retains individual organisms. Benthic samples were collected from 10 sites in\\u000a 2 regions and processed to validate an
Oxygen and total dissolved inorganic carbon (DIC) fluxes at the watersediment interface were measured using benthic chambers to assess the short-term variations of community respiration (CR) in the back reef sediments of Reunion Island (Indian Ocean). Benthic CR had a daily cycle of minimal (6:00 AM) and maximal values (6:00 PM), showing increases of oxygen and DIC fluxes of 2.8-
Jacques Clavier; Laurent Chauvaud; Pascale Cuet; Clémentine Esbelin; Patrick Frouin; Dorothée Taddei; Gérard Thouzeau
Many coral reef ecosystems experience shifts in benthic community composition from scleractinian corals to algae. However,\\u000a consequences of such phase shifts on O2 availability, important for many reef organisms, are unresolved. This study therefore comparatively investigated potential\\u000a in situ effects of different benthic cover by reef macroalgae and scleractinian corals on water column O2 concentrations in a Northern Red Sea
Wolfgang NigglAndreas; Andreas F. Haas; Christian Wild
Benthic foraminiferal Mg/Ca paleothermometry is based on an empirical relationship between the Mg/Ca of benthic foraminifera recovered from core tops and in situ bottom water temperatures (Rosenthal, 1997; Martin et al, in press; Lear et al, in review). While there is a tight correlation between shell Mg/Ca and temperature over a broad range of temperatures (-1 to 20 degrees C), Mg/Ca variation over the small range of deep water temperatures reveals departures from the calibration curve at low temperatures. Lower Mg/Ca values are generally associated with the deepest sites from the Atlantic and Pacific, contributing to an apparently steeper Mg/Ca-T response for abyssal benthics. The steeper response of abyssal benthics may reflect an influence of decreasing carbonate saturation with depth. Saturation related effects have already been documented for Mg in planktonic foraminifera and for other metals (Cd, Ba, and Zn) in benthic foraminifera shells (see Marchitto and ref. therein). Although it is difficult to definitively separate the effects of various environmental parameters (including temperature, depth, and relative saturation states), which often change in unison, we can use the core top Mg/Ca data to estimate the potential influence of saturation state. An alternative calibration of the benthic Mg/Ca - T relationship can be derived from core top benthic foraminifera based only on sites bathed in waters above carbonate saturation that yields a slightly smaller change in Mg/Ca per degree C (~9.5% vs. 11%) but better explains benthic Mg/Ca from the coldest sites (-1degrees C). Using this alternative Mg/Ca -T relation and a subset of data from the Ceara Rise and Ontong Java Plateau, we can estimate a maximum Mg/Ca offset attributable to saturation state. By comparing core top and downcore data, we can also address possible differences in the primary Mg-T response and carbonate saturation related effects between different genera (Cibicidoides and Uvigerina).
At regional scales, the distribution of species and the structure of assemblages vary with latitude within many marine and terrestrial systems. The oligotrophic coastal waters of Western Australia (WA) support highly speciose and endemic assemblages, yet spatial patterns in benthic structure are currently poorly known. We examined benthic assemblage composition along a latitudinal gradient of 28.533.5°S and a depth gradient
D. A. Smale; G. A. Kendrick; K. I. Waddington; K. P. Van Niel; J. J. Meeuwig; E. S. Harvey
This study consisted of sampling benthic algae at 32 sites in the Gangqu River, an important upstream tributary of the Yangtze\\u000a River. Our aims were to characterize the benthic algae communities and relationships with environmental variables. Among the\\u000a 162 taxa observed, Achnanthes linearis and Achnanthes lanceolata var. elliptica were the dominant species (17.10% and 14.30% of the total relative abundance,
This study assessed benthic macroinvertebrates and periphyton and its responses to managed river-flows, in riffles downstream\\u000a of three dams on the Cotter River, Australian Capital Territory. Benthic macroinvertebrates and periphyton were also assessed\\u000a in adjacent tributaries of the river, as well as in a nearby unregulated river and its tributaries. Food sources of four macroinvertebrate\\u000a taxa (Leptophlebiidae, Elmidae, Glossosomatidae and
We studied the distribution and seasonal abundance of benthic macroinvertebrates from July 1975 through September 1976 in\\u000a a hypereutrophic lake in subtropical Florida. The benthic community was comprised principally of oligochaetes (56.1%), chironomids\\u000a (37.1%), and chaoborids (5.7%). Numbers of taxa and mean densities correlated negatively with depth and positively with mean\\u000a grain size of the substratum and dissolved oxygen concentration
The effects of offshore placer gold mining on benthic invertebrates were assessed on sand and cobble substrates in Norton Sound, northeastern Bering Sea. Mining with a bucket-line dredge occurred nearshore in 920 m during June to November 198690. Sampling nearly a year subsequent to mining demonstrated minor alteration of substrate granulometry with no clear trends. However, benthic macrofaunal community parameters
The effects of Hurricane Katrina on benthic fauna and habitat quality in coastal waters of Louisiana, Mississippi, and Alabama,\\u000a USA, were assessed in October, 2005, 2 months after the hurricane made landfall between New Orleans, LA and Biloxi, MS. Benthic\\u000a macrofaunal samples, sediment chemical concentrations, and water quality measurements from 60 sites in Lake Pontchartrain\\u000a and Mississippi Sound were compared with
Virginia D. Engle; Jeffrey L. Hyland; Cynthia Cooksey
Estuarine benthic organisms are frequently subjected to disturbance events caused by hydrodynamic processes that disrupt and\\u000a move the sediment in which the animals reside, however the mechanisms by which physical disturbance processes affect infaunal\\u000a and epifaunal populations and communities remain poorly resolved. The responses of three infaunal and two epifaunal estuarine\\u000a benthic species to sediment disturbance (burial) were compared in
Elizabeth K. Hinchey; Linda C. Schaffner; Cara C. Hoar; Bruce W. Vogt; Lauren P. Batte
Changes to benthic infauna caused by exploratory gas drilling operations in the Minerva field were examined experimentally using a BACI (before, after, control, impact) design. Analysis of 72×0.1 m2 SmithMcIntyre grab samples obtained from one pre-drilling and three post-drilling periods yielded a diverse fauna consisting of 196 invertebrate species and 5035 individuals. Changes to benthic community structure were assessed using
Benthic cyanobacteria are found globally in plethora of environments. Although they have received less attention than their planktonic freshwater counterparts, it is now well established that they produce toxins and reports of their involvement in animal poisonings have increased markedly during the last decade. Most of the known cyanotoxins have been identified from benthic cyanobacteria including: the hepatotoxic microcystins, nodularins and cylindrospermopsins, the neurotoxic saxitoxins, anatoxin-a and homoanatoxin-a and dermatotoxins, such as lyngbyatoxin. In most countries, observations of toxic benthic cyanobacteria are fragmented, descriptive and in response to animal toxicosis events. Only a limited number of long-term studies have aimed to understand why benthic proliferations occur, and/or how toxin production is regulated. These studies have shown that benthic cyanobacterial blooms are commonly a mixture of toxic and non-toxic genotypes and that toxin concentrations can be highly variable spatially and temporally. Physiochemical parameters responsible for benthic proliferation vary among habitat type with physical disturbance (e.g., flow regimes, wave action) and nutrients commonly identified as important. As climatic conditions change and anthropogenic pressures on waterways increase, it seems likely that the prevalence of blooms of benthic cyanobacteria will increase. In this article we review current knowledge on benthic cyanobacteria: ecology, toxin-producing species, variables that regulate toxin production and bloom formation, their impact on aquatic and terrestrial organisms and current monitoring and management strategies. We suggest research needs that will assist in filling knowledge gaps and ultimately allow more robust monitoring and management protocols to be developed. PMID:23891539
The biogeography of marine benthic macroinvertebrates of US Atlantic estuaries and inshore coastal areas from Delaware Bay\\u000a north to Passamaquoddy Bay was studied to compare recent data with historical biogeographic studies, define physicalchemical\\u000a factors affecting species distributions, and provide information for calibrating benthic indices of environmental condition.\\u000a Five years (20002004) of data from 614 non-polluted, soft-bottom stations from the National
Estuarine benthic macroalgae are excellent producers of new carbonaceous material through their high rates of photosynthesis. Under some circumstances, this organic carbon is liberated into the aquatic environment in dissolved form while the plant is actively photosynthesizing. This project established a protocol for examining the effects of different combinations of salinity, temperature, and emergence/submergence regimes, determined the effects of antibiotics on the photosynthetic rate, and the extent to which these factors effect liberation of organics by selected estuarine benthic macroalgae.
Laboratory experiments were performed to study the growth rate and phosphorus (P) and nitrogen (N) uptakes of eight benthic\\u000a microalgae species isolated from different sources of pig manure. Cells immobilized in calcium alginate beads were cultured\\u000a with three replicates for each species. P removal rates obtained for the unicellular self-aggregating benthic species (Palmellopsis gelatinosa, Chlorosarcinopsis sp., and Macrochloris sp.) were
Carmen Pérez-Martínez; Pedro Sánchez-Castillo; Maria Valle Jiménez-Pérez
Benthic macroinvertebrates have many useful properties that make possible the use of these organisms as sentinel in biomonitoring programmes in freshwater. Combined with the characteristics of the water and sediment, benthic macroinvertebrates are potential indicators of environmental quality. Thus, the spatial occurrence of potentially toxic metals (Al, Zn, Cr, Co, Cu, Fe, Mn and Ni) in the water, sediment and benthic macroinvertebrates samples were investigated in a sub-basin in the southeast of Brazil in the city of São Carlos, São Paulo state, with the aim of verifying the metals and environment interaction with benthic communities regarding bioaccumulation. Hypothetically, there can be contamination by metals in the aquatic environment in the city due to lack of industrial effluent treatment. All samples were analysed by the USEPA adapted method and processed in an atomic absorption spectrophotometer. The sub-basin studied is contaminated by toxic metals in superficial water, sediment and benthic macroinvertebrates. The Bioaccumulation Factor showed a tendency for metal bioaccumulation by the benthic organisms for almost all the metal species. The results show a potential human and ecosystem health risk, contributing to metal contamination studies in aquatic environments in urban areas. PMID:21755156
The authors examined food web magnification factors of total mercury (THg) and methylmercury (MeHg) for the benthic organisms in Masan Bay, a semiclosed, temperate estuary located on the southeastern coast of Korea. For benthic invertebrates, concentrations of THg and MeHg (%MeHg) ranged from 9.57 to 195 and 2.56 to 111 ng/g dry weight (12.2-85.6%), respectively. Benthic fish THg and MeHg (%MeHg) concentrations ranged widely from 10.8 to 618 and 2.90 to 529 ng/g dry weight (22.9-93.9%), respectively. The linear regression slopes of log [Hg] relative to ?(15)N (i.e., food web magnification factors) found for the Masan Bay benthic organisms were 0.119 for THg and 0.168 for MeHg. These values are similar to the food web magnification factors of benthic organisms and lower than those of pelagic organisms of various coastal marine environments. It suggests that pelagic organisms might be at greater risk of THg and MeHg accumulation than benthic biota. PMID:22447737
Kim, Eunhee; Kim, Hyunji; Shin, Kyung-hoon; Kim, Min-seob; Kundu, Sampa Rani; Lee, Byeong-gweon; Han, Seunghee
Live benthic foraminifera in the superficial sediments from the muddy central axis of the Ría de Vigo were examined under two contrasting hydrographic conditions: downwelling and upwelling. During downwelling conditions the abundance of benthic foraminifera does not show large differences between sites with different organic carbon contents. The arrival of labile organic carbon to the seafloor delivered during upwelling events causes an increase in the abundance of the most significant species and the appearance of new species in the life assemblage. This suggests that benthic foraminiferal faunas strongly depend on high quality organic carbon supply and the sedimentary organic carbon is not a good indicator of food availability to benthic foraminifera. The response of benthic foraminifera to phytoplankton blooms differs between outer and inner sites. In outer and middle areas benthic foraminiferal assemblages show quick population growth in reaction to phytoplankton blooms (r-strategists), whereas in inner sites the most abundant species displays both growth and reproduction (k-strategists). It is suggested that r-strategy results of adaptation to perturbations on short time-scales (downwelling/upwelling cycles) under favourable microenvironmental conditions, while the k-strategy represents the adaptation to long term perturbations, such as relatively low oxygen concentrations and/or reducing microenvironmental conditions in the sediment.
This report presents porewater and selected water column data collected from Coeur d'Alene Lake in September of 1992. Despite probable oxidation of the porewater samples during collection and handling, these data are used to calculate molecular diffusive fluxes of dissolved metals (that is, Zn, Pb, Cu, and Mn) across the sediment-water interface. While these data and calculations provide preliminary information on benthic metal fluxes in Coeur d'Alene Lake, further work is needed to verify their direction and magnitude. The benthic flux calculations indicate that the sediment is generally a source of dissolved Zn, Cu, Mn, and, possibly, Pb to the overlying water column. These benthic fluxes are compared with two other major sources of metals to Coeur d'Alene Lake-the Coeur d'Alene and St. Joe Rivers. Comparisons indicate that benthic fluxes of Zn, Pb, and Cu are generally less than half of the fluxes of these metals into the lake from the Coeur d'Alene River. However, in a few cases, the calculated benthic metal fluxes exceed the Coeur d'Alene River fluxes. Benthic fluxes of Zn and, possibly, Pb may be greater than the corresponding metal fluxes from the St. Joe River. These results have implications for changes in the relative importance of metal sources to the lake as remediation activities in the Coeur d'Alene River basin proceed.
In recent years considerable data have been compiled on heavy metal levels in biota in marine and estuarine environments. With respect to the fauna, much information is available on accumulation and effects of heavy metals in birds, fish and benthic macrofauna. Accumulation of heavy metals in aquatic flora has been studied mostly in benthic macroalgae, in particular in relation to the use as a biological monitor. The response of planktonic algal species to heavy metals has been studied extensively in cultured populations. Also. heavy metal concentrations in natural plankton have been studied. As far as we know, very few data are available on the concentrations of heavy metals in the lowest benthic trophic level, the benthic microflora. It is a major food supply for numerous intertidal species, so it is obvious that microflora might play an important role in the accumulation of contaminants through coastal food chains. The aim of this research was to adjust a recently developed collection technique for benthic diatoms so that it is suitable for large-scale field studies. The method was then used to assess the concentration of the heavy metals Cd, Cu, Pb and Zn in benthic diatoms and sediments along an estuarine gradient. 18 refs., 2 figs., 1 tab.
Absil, M.C.P.; Scheppingen, Y. van [Netherlands Inst. of Ecology, Vierstraat (Netherlands)
Strong benthicpelagic coupling is an important characteristic of shallow coastal marine ecosystems. Building upon a rich\\u000a history of benthic metabolism data, we measured oxygen uptake and nutrient fluxes across the sedimentwater interface along\\u000a a gradient of water column primary production in Narragansett Bay, RI (USA). Despite the strong gradients seen in water column\\u000a production, sediment oxygen demand (SOD) and benthic
Robinson W. Fulweiler; Scott W. Nixon; Betty A. Buckley
Detailed analyses of the benthic foraminiferal assemblages extracted with the cold acetolyse method together with high resolution geochemical and mineralogical investigations across the Paleocene\\/Eocene (P\\/E) boundary of the classical succession at Contessa Road (western Tethys), allowed to recognize and document the PaleoceneEocene Thermal Maximum (PETM) interval, the position of the Benthic Extinction Event (BEE) and the early recovery of benthic
Luca Giusberti; Rodolfo Coccioni; Mario Sprovieri; Fabio Tateo
Yellow Sea tidal flats are internationally recognised for their contribution to biological diversity and yet are under enormous\\u000a pressure from reclamation, pollution and overexploitation. The benthic macroinfauna community is the dominant community on\\u000a these tidal flats and a reliable indicator of benthic environmental changes. We surveyed the current benthic macroinfauna\\u000a community of the Ganghwa Southern Tidal Flat, the largest remaining
Keun-Hyung Choi; Sung-Mi Lee; Sang-Min Lim; Mark Walton; Gyung-Soo Park
This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared benthic macrofaunal Bray-Curtis similarity and the means of eight benthic macrofaunal community measures across seven habitat types in Tillamook Bay, Oregon, USA: intertidal eelgrass (Zostera marina), dwarf eelgrass (Zostera japonica), oyster (Crassostrea gigas) ground culture, burrowing mud shrimp (Upogebia pugettensis), burrowing ghost shrimp (Neotrypaea californiensis), sand and subtidal. Benthic macrofaunal Bray-Curtis similarity differed among all the habitats except ghost shrimp and sand. The habitat rank order on mean benthic macrofaunal species richness, abundance and biomass was dwarf eelgrass ? oyster ? mud shrimp ? eelgrass > sand ? ghost shrimp ? subtidal. The benthic macrofaunal habitat usage pattern in Tillamook Bay was, with a few exceptions, similar to that in two other US Pacific Northwest estuaries. The exceptions indicate variants of eelgrass and ghost shrimp habitat that differ in benthic macrofaunal usage perhaps due to differences in the coarseness of the sand fraction of the sediments in which they live. The similarities indicate periodic benthic macrofaunal usage patterns across the other habitat types extend over a wider geographic scale and range of environmental conditions than previously known.
Benthic diatoms evolved in a biofilm structure, at the interface between water and substrata. Biofilms can adsorb toxicants, such as herbicides, but little is known about the exposure of biofilm organisms, such as benthic diatoms, to these adsorbed herbicides. We assessed the sensitivity of 11 benthic diatoms species to 6 herbicides under both planktonic and benthic conditions using single-species bioassays. The concentration that reduced the growth rate of the population by 10% (EC10) and 50% (EC50), respectively, varied depending on the species, the herbicides, and the growth forms involved. As a general trend, the more hydrophobic the herbicide, the more species were found to be sensitive under benthic growth conditions. Statistical differences (alpha<5%) were observed between the sensitivities under planktonic and benthic growth conditions for many hydrophobic herbicides. A protective effect of the biofilm against herbicides was observed, and this tended to decrease (at both the EC10 and EC50 levels) with increasing hydrophobicity. The biofilm matrix appeared to control exposure to herbicides, and consequently their toxicity towards benthic diatoms. For metolachlor, terbutryn and irgarol, benthic thresholds derived from species sensitivity distributions were more protective than planktonic thresholds. For hydrophobic herbicides, deriving sensitivity thresholds from data obtained under benthic growth seems to offer a promising alternative. PMID:23831793
The mechanism of diatom locomotion has been widely researched but still remains a hypothesis. There are several questionable points on the prevailing model proposed by Edgar, and some of the observed phenomena cannot be completely explained by this model. In this paper, we undertook detailed investigations of cell structures, locomotion, secreted mucilage, and bending deformation for a benthic pennate diatom Navicula species. According to these broad evidences, an updated locomotion model is proposed. For Navicula sp., locomotion is realized via two or more pseudopods or stalks protruded out of the frustules. The adhesion can be produced due to the pull-off of one pseudopod or stalk from the substratum through extracellular polymeric substances. And the positive pressure is generated to balance the adhesion because of the push-down of another pseudopod or stalk onto the substratum. Because of the positive pressure, friction is generated, acting as a driving force of locomotion, and the other pseudopod or stalk can detach from the substratum, resulting in the locomotion. Furthermore, this model is validated by the force evaluation and can better explain observed phenomena. This updated model would provide a novel aspect on underwater locomotion strategy, hence can be useful in terms of artificial underwater locomotion devices. PMID:23645345
We describe a new chamber-based benthic microbial fuel cell (BMFC) that incorporates a suspended, high surface area and semi-enclosed anode to improve performance. In Yaquina Bay, OR, two chambered BMFC prototypes generated current continuously for over 200 days. One BMFC was pumped intermittently, which produced power densities more than an order of magnitude greater than those achieved by previous BMFCs with single buried graphite-plate anodes. On average, the continuous power densities with pumping were 233 mW/m2 (2.3 W/m3); peak values were 380 mW/m2 (3.8 W/m3), and performance improved over the time of the deployments. Without pumping, high power densities could similarly be achieved after either BMFC was allowed to rest at open circuit. A third chambered BMFC with a 0.4 m2 footprint was deployed at a cold seep in Monterey Canyon, CA to test the new design in an environment with natural advection. The power density increased 5-fold (140 mW/m2 vs 28 mW/m2) when low-pressure check valves allowed unidirectional flow through the chamber. PMID:18075105
Nielsen, Mark E; Reimers, Clare E; Stecher, Hilmar A
Deep-sea sediments harbour a vast biosphere. Archaea-one of the three domains of life-are prevalent in marine environments, and comprise a significant fraction of the biomass in marine sediments. Archaeal membranes are well characterized, and are comprised of a glycerol backbone and a nonpolar isoprenoid chain. However, the ecology of sedimentary archaea remains elusive, because it is difficult to grow them in the laboratory. Here, we trace the fate of 13C-labelled glucose added to marine sediments in Sagami Bay, Japan, to determine the in situ mechanisms of membrane synthesis. Following the addition of labelled glucose to sediment samples collected in the region, we placed the cores on the sea floor and sampled them after 9 and 405days. We found that the 13C was incorporated into the glycerol backbone of archaeal membranes; 13C was apparent after 9 days of incubation, but most pronounced after 405 days. However, the isoprenoid chain of the membranes remained unlabelled. On the basis of the differential uptake of 13C, we suggest that the glycerol unit is synthesized de novo, whereas the isoprenoid unit is synthesized from relic archaeal membranes and detritus, because of the prevalence of these compounds in marine sediments. We therefore suggest that some benthic archaea build their membranes by recycling sedimentary organic compounds.
Traction transport of pebbles and cobbles occurs subtidally at current velocities below 0.5 m s- 1 when seaweed attached to clasts provides additional lift and drag to the clast. In the Juan de Fuca Strait, British Columbia, Canada, the seaweed Cymanthere triplicata commonly attaches to pebbles and provides sufficient additional surface area for tidal currents to drag the clast along the seafloor. Using in situ measurements of current velocities at 13 m water depth, the threshold for initiation of motion of a 30 mm pebble with attached seaweed is 0.3 m s- 1. This is approximately one order of magnitude less than the activation velocity for a 30 mm pebble without attached seaweed.In addition to kelp-rafted (floated) gravel, seaweed-assisted, benthic gravel transport is possible in marine settings where unidirectional currents (e.g., tidal currents, storm-induced bottom currents) are sufficient to transport pebbles alongshore, and into and across the offshore (below fairweather wave base). If preserved in the rock record, deposits of algal-enhanced gravel deposited via unidirectional, subtidal currents will likely appear as isolated gravel clasts encased in sandstone, reflecting the similar current velocities required to transport these two clast groups.
There are several benthic macroinvertebrate sampling techniques currently being used by the Montana Department of Environmental Quality (DEQ) that evaluate instream water resource quality. A traveling kick or a jab with a D-frame net collects most samples. DEQ monitors a smaller proportion of sites using Hess Samplers. Also used in the state are the sampling methods of the U.S. EPA Environmental Monitoring and Assessment Program (EMAP) and Regional Environmental Monitoring and Assessment Program (REMAP). Both EMAP and REMAP use a D-frame net, distributing sampling effort throughout the target reach along a series of transects. The purpose of this study is to evaluate the effects of these four different sampling techniques on the samples gathered, in particular, on taxonomic diversity and metric values. This evaluation will help DEQ accomplish its ultimate goal: to implement consistent statewide sampling protocols. We developed a suite of both quantitative and qualitative performance characteristics (precision, accuracy, bias) for each of the methods, and directly compared them among the protocols. The level of comparability among methods was characterized and the acceptability of each method for use by Montana DEQ was determined.
Feldman, D. L.; Laidlaw, T.; Jessup, B.; Stribling, J.; Stagliano, D.; Bollman, W.
The implementation of legislations is generating a fruitful debate amongst marine scientists about how to define efficient and reliable bio-assessment tools to monitor the ecological quality status (EcoQS) of marine waters. According to those legislations, EcoQS assessment needs a "reference condition" with which to compare the present-day condition at a site. The fossil record has a potential to reconstruct PaleoEcoQS and thereby establish in situ reference conditions from pre-impact times. Unlike most macrofaunal groups which are the most commonly used biological quality indicator in these environments, benthic foraminifera leave a fossil record and therefore allow the reconstruction of human-induced environmental disturbance over decades to centuries. Foraminifera have the potential to serve as ecosystem characterization tools in modern and past marine environments. We compared the response of benthic foraminifera, macrofauna and selected environmental parameters from the same sites in areas with relatively stable salinity and temperature conditions but otherwise contrasting environmental properties (e.g., varying degree of anthropogenic impact). In August 2008, replicate samples for living (stained) benthic foraminifera and macrofauna from 27 stations in 11 silled fjords along the Norwegian Skagerrak coast were examined. Environmental data (bottom-water dissolved-oxygen, TOC, TN and pigments) were analysed for each station. The same kind of data were analysed from 2 recolonisation sites in the inner Oslofjord. In addition, the PaleoEcoQS during the past century was reconstructed using benthic foraminifera and selected environmental parameters from 11 stations in the inner Oslofjord. Results show that living benthic foraminifera are at least as reliable to define present-day EcoQS as conventional methods. Fossil benthic foraminifera can also define ecological status of reference conditions from pre-impacted times. This is not possible using conventional methods. Consequently, benthic foraminifera are excellent bioindicators of human-induced environmental impacts over time.
Bouchet, V. M. P.; Hess, S.; Dolven, J. K.; Alve, E.
Benthic invertebrate and water quality data collected during previous U.S. Geological Survey studies to provide background hydrologic information on streams draining Tennessee coal reserves, were evaluated to identify possible relations between stream biota and water quality. Linear regressions produced low correlation coefficients relating the number of taxa/sample, total number of organisms/sample, sample diversity, and percentage composition of selected orders of invertebrates, with average water quality parameter values available at sampling stations (r is < 0.62 at p=0.05). Analyses of these data by linear regressions explained little of the variability in benthic invertebrate samples primarily because the distributions of benthic organisms along environmental gradients are nonlinear. Variability in substrate characteristics in the study area and seasonal insect emergence patterns also complicated interpretation of these data. However, analysis of variance tests did indicate significant trends towards reduced number of taxa, number of organisms, and sample diversity at stations with relatively poor water quality conditions. Decreasing percentage composition of Ephemeroptera was generally accompanied by an increase in percent Diptera at stations with higher water quality constituent concentrations and acidic pH ( > than 0.6 units). These trends indicate significant differences in benthic communities at sites with evidence of more severe land use impacts. Additional data on benthic invertebrates, water quality , and physical habitat conditions, along with analyses of data using multivariate statistical methods are needed to define ecological relations between specific groups of invertebrates and environmental conditions. (Author 's abstract)
I simultaneously tested three alternative hypotheses (the trophic cascade, nutrient enhancement via terrestrial nutrient translocation, and nutrient enhancement via bioturbation) for consumer regulation of primary productivity (PPR) by three widely distributed stream fish species (Orangethroat Darter, Western Mosquitofish, and Bullhead Minnow). I used stream mesocosms fitted with fish and terrestrial input barriers to address relative importance of localized fish predation versus access to terrestrial inputs for fish consumer effects. Orangethroat Darter, a benthic invertivore, increased PPR through an apparent trophic cascade, by localized reduction of benthic grazing invertebrate densities. Western mosquitofish, a surface feeding insectivore, increased PPR by enhancing nutrients through terrestrial nutrient translocation, and had no effect on benthic grazer invertebrate density. Bullhead Minnow, a benthic omnivore that disturbed sediments during foraging, increased PPR through nutrient enhancement via bioturbation, but within specific stream mesocosm areas two which the fish was restricted it also reduced benthic grazing invertebrates. Thus, suggesting this species may have affected PPR through a combination bioturbation and trophic cascade mechanisms. These mechanistic pathways are likely common processes by which fish affect food web structure and ecosystem function in many stream ecosystems.
In lotic ecosystems, the most common disturbance events occur at the extremes of the hydrological continuum, i.e. spates and streambed drying. During spates, high flow velocities can mobilise sediments and displace invertebrates, and during streambed drying, loss of free water can cause mass mortality of many aquatic taxa. In both cases, invertebrates inhabiting the surface sediments are subject to a greater frequency and magnitude of disturbance than those in the hyporheic zone, and this habitat may therefore act as a refugium. Between extreme events, stable hydrological conditions allow competitive species to thrive, which can cause biotic interactions to increase. We compared the effects of flow extremes and hydrological stability on benthic and hyporheic invertebrate communities. Hydrological conditions included spates, flow recession, and localised streambed drying. During flow recession, competitive benthic taxa, particularly Gammarus pulex (Amphipoda) increased in abundance in surface sediments, causing community diversity to decline. A concurrent increase in the hyporheic abundance of G. pulex indicated that the hyporheic zone may act as a refugium from increasing biotic pressures in the benthic sediments. In contrast, spate events caused severe reductions in both benthic and hyporheic invertebrate abundance, and declines in G. pulex abundance were particularly pronounced; spate events were therefore important in increasing both benthic and hyporheic community diversity.
Different land uses affect the characteristics of a hydrographic basin, reflected in the river water quality, and consequently affecting the aquatic biota. The benthic community closely reflects the alterations caused by different human activities. In this study, the effects of different land uses were evaluated by analysis of the benthic community structure in streams with urban, agricultural and pasturage influences, as well as areas in better-conserved regions. The abiotic parameters showed distinct seasonal variability, which did not occur with the benthic organisms. A degradation gradient was observed among the study sites, in the headwaters-agriculture-pasture-urban direction. By the CCA its possible to observe that the density of organisms tended to increase along this gradient, whereas richness, diversity, evenness, and EPT families decreased. The most intense effects of land use on the benthic community composition, richness, and diversity were observed in urban areas (F (1,4) = 16.0, p = 0.01; F (1,4) = 8.97, p = 0.04; respectively). In conclusion a trend in the benthic community is observed in to predict alterations caused for the different land uses, mainly, when the source point pollution, as the case of urban area. PMID:18843547
The Chesapeake Bay benthic index of biotic integrity (B-IBI) was developed to assess benthic community health and environmental quality in Chesapeake Bay. The B-IBI provides Chesapeake Bay monitoring programs with a uniform tool with which to characterize bay-wide benthic community condition and assess the health of the Bay. A probability-based design permits unbiased annual estimates of areal degradation within the Chesapeake Bay and its tributaries with quantifiable precision. However, of greatest interest to managers is the identification of problem areas most in need of restoration. Here we apply the B-IBI to benthic data collected in the Bay since 1994 to assess benthic community degradation by Chesapeake Bay Program segment and water depth. We used a new B-IBI classification system that improves the reliability of the estimates of degradation. Estimates were produced for 67 Chesapeake Bay Program segments. Greatest degradation was found in areas that are known to experience hypoxia or show toxic contamination, such as the mesohaline portion of the Potomac River, the Patapsco River, and the Maryland mainstem. Logistic regression models revealed increased probability of degraded benthos with depth for the lower Potomac River, Patapsco River. Nanticoke River, lower York River, and the Maryland mainstem. Our assessment of degradation by segment and water depth provided greater resolution of relative condition than previously available, and helped define the extent of degradation in Chesapeake Bay. PMID:12620013
Llansó, Roberto J; Dauer, Daniel M; Vølstad, Jon H; Scott, Lisa C
Heterotrophic bacteria and fungi are widely recognized as crucial mediators of carbon, nutrient, and energy flow in ecosystems, yet information on their total annual production in benthic habitats is lacking. To assess the significance of annual microbial production in a structurally complex system, we measured production rates of bacteria and fungi over an annual cycle in four aerobic habitats of a littoral freshwater marsh. Production rates of fungi in plant litter were substantial (0.2 to 2.4 mg C g?1 C) but were clearly outweighed by those of bacteria (2.6 to 18.8 mg C g?1 C) throughout the year. This indicates that bacteria represent the most actively growing microorganisms on marsh plant litter in submerged conditions, a finding that contrasts strikingly with results from both standing dead shoots of marsh plants and submerged plant litter decaying in streams. Concomitant measurements of microbial respiration (1.5 to 15.3 mg C-CO2 g?1 of plant litter C day?1) point to high microbial growth efficiencies on the plant litter, averaging 45.5%. The submerged plant litter layer together with the thin aerobic sediment layer underneath (average depth of 5 mm) contributed the bulk of microbial production per square meter of marsh surface (99%), whereas bacterial production in the marsh water column and epiphytic biofilms was negligible. The magnitude of the combined production in these compartments (?1,490 g C m?2 year?1) highlights the importance of carbon flows through microbial biomass, to the extent that even massive primary productivity of the marsh plants (603 g C m?2 year?1) and subsidiary carbon sources (?330 g C m?2 year?1) were insufficient to meet the microbial carbon demand. These findings suggest that littoral freshwater marshes are genuine hot spots of aerobic microbial carbon transformations, which may act as net organic carbon importers from adjacent systems and, in turn, emit large amounts of CO2 (here, ?870 g C m?2 year?1) into the atmosphere.
Benthic macroinvertebrate communities have been sampled at 27 of Maryland's CORE monitoring stations since 1976. On average, the benthic samples have been collected annually during the spring to summer months using either a Surber sampler or Fullner modif...
This activity involves an exploration of density. Why does oil float on water? How does drain cleaner sink down into the clogged pipe right through standing water? These questions will be answered as students make a layered "parfait" of colored liquids ba
Figure from the Nature Geoscience article, Geodynamics: Layer cake or plum pudding? by Paul Tackley (Nature Geoscience 1, 157 - 158 (2008)). The figure shows the current understanding of the interaction between the 660 km discontinuity, the core-mantle boundary, downgoing slabs, upwelling plumes.
Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering) or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator) and Abra alba (bioturbator) compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The 13C labelled diatom Skeletonema costatum was added to 4 treatments: (1) microcosms containing the bioturbator, (2) microcosms containing the bio-irrigator, (3) control microcosms and (4) microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (??13C) of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom 13C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m?2), which included TO13C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food source for nematodes, the macrobenthic effect was more pronounced in niche establishment than the negative structuring effects such as competition.
Braeckman, Ulrike; Provoost, Pieter; Moens, Tom; Soetaert, Karline; Middelburg, Jack J.; Vincx, Magda; Vanaverbeke, Jan
The Reference Condition Approach (RCA) is now widely adopted as a basis for the evaluation of the ecological quality of water bodies. In accordance with the RCA, the integrity of communities found in a given location should be analyzed according to their deviation from the communities that would be expected in the absence of anthropogenic disturbances. The RCA was used here with the aim of defining the Maximum Ecological Potential (MEP) of tropical reservoirs located in the hydrographical basin of the Paraopeba River in the state of Minas Gerais, Brazil. Among the reservoirs, Serra Azul is used as a water supply and is located in a core area of environmental protection where tourism is not allowed and the native vegetation is conserved. The benthic macroinvertebrate communities at 90 sites located in three reservoirs were analyzed and sampled every 3 months over 2 years. The temporal patterns of the communities in the three reservoirs were analyzed (2nd-STAGE MDS and ANOSIM) and were not significantly related to seasonal fluctuations in temperature and precipitation. Twenty-eight sites belonging to the Serra Azul reservoir were selected to define the MEP of these reservoirs because these sites had the lowest human disturbance levels. The macroinvertebrate taxa present in the selected MEP sites are similar to those of natural lakes and different from the communities of disturbed sites. The biological classification of these sites revealed two groups with distinct macroinvertebrate communities. This distinction was related to climatic variables, bottom substrate type, the presence of gravel/boulders, coarse sand, silt, clay or muck, depth, and the shoreline substrate zone. These two subsets of biological communities and respective environmental conditions can serve as a basis for the future implementation of ecological quality monitoring programs for tropical reservoirs in the study area. This approach can also, however, be implemented in other geographic areas with artificial or heavily modified water bodies. PMID:23288597
Molozzi, Joseline; Feio, Maria João; Salas, Fuensanta; Marques, João Carlos; Callisto, Marcos
The relative sensitivities of bioassays to determine the toxicity of sediments were investigated and three methods of making the sample dilutions required to generate dose-response relationships were compared. The assays studied were: (a) Microtox(R), a 15-min assay of Photobacterium phosphoreum bioluminescence inhibition by pore water; (b) 48-h Daphnia magna lethality test in pore water; (c) 10-d subchronic assay of lethality to and reduction of weight gain by Chironomus tentans performed in either whole sediment or pore water; (d) 168-h acute lethality assay of Hexagenia limbata in either whole sediment or pore water. The three methods of diluting sediments were: (a) extracting pore water from the toxic location and dilution with pore water from the control station; (b) diluting whole sediment from the toxic location with control whole sediment from a reference location, then extracting pore water; and (c) diluting toxic, whole sediment with whole sediment from a reference location, then using the whole sediment in bioassays. Based on lethality, H. limbata was the most sensitive organism to the toxicity of Detroit River sediment. Lethality of D. magna was similar to that of H. limbata in whole sediment and can be used to predict effects of whole sediment toxicity to H. limbata. The concentration required to cause a 50% reduction in C. tentans growth (10-d EC50) was approximately that which caused 50% lethality of D. magna (48-h LC50) and was similar to the toxicity that restricts benthic invertebrate colonization of contaminated sediments. While the three dilution techniques gave similar results with some assays, they gave very different results in other assays. The dose-response relationships determined by the three dilution techniques would be expected to vary with sediment, toxicant and bioassay type, and the dose-response relationship derived from each technique needs to be interpreted accordingly.
Giesy, John P.; Rosiu, Cornell J.; Graney, Robert L.; Henry, Mary G.
Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of foraminiferal tests revealed three assemblages that depend mainly on the intensity of pollution; (1) a highly polluted tidal flat assemblage, (2) normal (or less polluted) mud flat assemblage and, (3) tidal channel and subtidal assemblage. The highly polluted assemblage characterized by a drop in species densities (< 100 tests/20 cm(3) sediment) but with high average diversity (5.8 Yule-Simpson Index). The microfauna of the less polluted flat displays relatively lower diversity (4.6) but high density of tests (47.2% of the total picked tests). The most abundant species of this assemblage is Ammonia tepida, displays its maximum density in this assemblage. Ammonia tepida drops in density from 17.12% to 3.07% in the polluted assemblage. Tidal channel foraminiferal assemblages should normally display lower diversities than those of tidal flats, because tidal current in the channels tend to wash away most nutrient materials. However, this is not the case of the present study area which could be due to environmental setting of the Sulaibikhat Bay in which tidal currents bring in exceptionally high amounts of nutrients from Shatt Al-Arab Estuary and in which the tidal flats are strongly and adversely polluted. PMID:18389379
Al-Zamel, A Z; Al-Sarawi, M A; Khader, S R; Al-Rifaiy, I A
Downward fluxes of nucleic acids adsorbed onto settling particles play a key role in the supply of organic phosphorus and genetic material to the ocean interior. However, information on pelagic-benthic coupling, diagenesis, and processes controlling nucleic acid preservation in deep-sea sediments is practically nonexistent. In this study, we compared nucleic acid fluxes, sedimentary DNA and RNA concentrations, and the enzymatically hydrolyzable fraction of DNA in a bathyal continental margin (North Aegean Sea) and an open-sea system (South Aegean Sea) of the Eastern Mediterranean. The two systems displayed contrasting patterns of nucleic acid fluxes, which increased significantly with depth in the North Aegean Sea and decreased with depth in the South Aegean Sea. These results suggest that in continental margin and open-ocean systems different processes control the nucleic acid supply to the sea floor. Differences in nucleic acid fluxes were reflected by nucleic acid concentrations in the sediments, which reached extremely high values in the North Aegean Sea. In this system, a large fraction of DNA may be buried, as suggested by the large fraction of DNA resistant to nuclease degradation and by estimates of burial efficiency (ca. eight times higher in the North than in the South Aegean Sea). Overall, the results reported here suggest that the preservation of DNA in deeper sediment layers may be favored in benthic systems characterized by high sedimentation rates.
A complete succession of lower bathyalupper abyssal sediments was deposited across the PaleoceneEocene Thermal Maximum (PETM) at Alamedilla (Betic Cordillera, Southern Spain), where the benthic foraminiferal turnover and extinction event associated with the negative carbon isotope excursion (CIE) across the PETM have been investigated. Detailed quantitative analyses of benthic foraminifera allowed us to distinguish assemblages with paleoecological and paleoenvironmental significance:
Seasonal dynamics of contents of essential polyunsaturated fatty acids (PUFA) in dominant groups of benthic invertebrates: gammarids (Gammaridae, Amphipoda), oligochaetes (Oligochaeta), chironomid larvae (Chironomidae, Diptera) and caddisfly larvae (Trichoptera), and dominant benthivorous fish, Siberian grayling Thymallus arcticus, have been studied in ecosystem of the large Siberian river. During the year of the study most benthic invertebrate taxa showed significant variations
N. N. Sushchik; M. I. Gladyshev; G. S. Kalachova; O. N. Makhutova; A. V. Ageev
Remotely operated vehicle (ROV) video observations were used to document benthic fauna at a hydrocarbon drilling location, at 2 720 m depth, in the poorly studied deep water off northern Egypt. The decapod Chaceon mediterraneus was the most common organism at the site and the only benthic megafaunal invertebrate observed. Three species of fish, Coryphaenoides mediterraneus, Cataetyx laticeps and Bathypterois
We investigate the applicability of modern benthic foraminiferal based paleoproductivity proxies to fossil assemblages in the South China Sea. This western Pacific marginal basin has a 30 Myr continuous pelagic sediment record and minimal carbonate dissolution, and thus provides ideal boundary conditions for such a test. We relate the composition of modern and Pleistocene to Oligocene benthic foraminiferal assemblages to
Detailed benthic foraminiferal analyses performed on the Holocene subsurface deposits of modern Po Delta evidenced a complex palaeogeographic evolution. Hierarchical R- and Q-mode cluster analyses allowed to distinguish four assemblages indicative of different marine environments and sub-environments. Temporal and spatial distribution patterns of benthic foraminifers reflect changes in Po River discharge during delta evolution. The capability of foraminiferal assemblages to
Organic carbon oxidation rates in San Clemente Basin were determined by benthic chamber experiments using the Bottom Lander, along with studies of pore water chemistry. Non-steady-state diagenetic models are developed for interpreting concentration-time data from the benthic chamber experiments. O 2 , NO 3 - , and SO 4 2- are all important oxidants for organic carbon at our study
Michael Bender; Richard Jahnke; Ray Weiss; William Martin; David T. Heggie; Joseph Orchardo; Todd Sowers
The distribution and correlation of benthic bio-community, water and sediment pollutants were evaluated with multivariate analysis from data collected over six samplings at 12 sites in the Ell-Ren river system, Taiwan. A total of 41 benthic algae species, 8 aquatic insect species and 2 annelid species were collected. On the basis of both principal component and correlation matrix analyses, we
Kuang-Chung Yu; Shien-Tsong Ho; Jiunn-Kae Chang; Sheue-Duanlai Lai
The nuisance diatom Didymosphenia geminata (didymo) presents an ecological paradox. How can this benthic algae produce such large amounts of biomass in cold, fast flowing, low nutrient streams? The aim of this paper is to present a conceptual model for the growth, persistence, and blooming behavior of this benthic mat-forming diatom that may help to explain this paradox. The conceptual
J. D. Cullis; C. Gillis; M. Bothwell; C. Kilroy; A. I. Packman; M. A. Hassan
Population changes of three major benthic taxa are discussed in relation to Dreissena spp. Lake Ontario was sampled pre-invasion (1972) and post-invasion (1994, 1997) for abundance of benthic organisms. In offshore sediments of Lake Ontario, neither species composition nor abunda...
This article focuses on the ecological role of benthic macrofauna on nutrient dynamics and benthic-pelagic coupling in the Baltic Sea with relation to eutrophication. Generally, benthic macrofaunal activities have large effects on sediment biogeochemistry and often with stimulatory effects on processes that counteract eutrophication, i.e., denitrification and increased phosphorus retention of the sediment. The degree of faunal impact on such processes varies depending on faunal density and functional group composition. The effect of macrofaunal activities on sediment nutrient dynamics can also result in a higher nitrogen: phosporus ratio of the sediments efflux compared with sediments without macrofauna. Increased internal nutrient loading during eutrophication-induced anoxia is suggested to be caused both by altered sediment biogeochemical processes and through reduced or lost bioturbating macrofauna and thereby a reduced stimulatory effect from their activities on natural purification processes of the Baltic Sea ecosystem. PMID:17520929
This report presents a summary of data collected and an updated progress report for a long-term benthic study conducted to measure the long-term effects of power plant operations on benthic populations and to identify long-term trends and annual cycles in these populations. Benthic organisms and the physical/chemical characteristics of sediments and water were sampled between July 1981 and May 1982 in the mesohaline portion of the Chesapeake Bay and the Potomac estuary. The surveys were concentrated near the Morgantown and Calvert Cliffs, Maryland power plant. Salinities during 1981-1982 were high relative to long-term salinity records with the deviation from average salinities being larger in the Potomac than the mainstem of the Bay.
Bottom hypoxia (dissolved oxygen concentration ?2 ml l(-1)) from anthropogenic eutrophication is a growing global concern. Here, we summarized characteristics of hypoxia and its effects on benthic organisms in Tokyo Bay. Despite recent decreases in nutrient inputs, hypoxia has been increasing in duration and spatial extent, suggesting that the substantial loss of tidal flats from reclamation is contributing to a decrease in the ability of Tokyo Bay to recycle nutrients. Hypoxia develops in the central to northern part of the bay and persists from spring to autumn, causing defaunation of benthic organisms. After the abatement of hypoxia in autumn, the defaunated area is recolonized, either through migration or larval settlement. Some megabenthic species with a spawning peak in spring and summer experience failure of larval settlement, which is probably due to hypoxia. The adverse effects of hypoxia are an impediment to recovery of benthic organisms in Tokyo Bay. PMID:21561630
Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.
This study tested the hypothesis that, during recent years, the benthic macroinvertebrate fauna of the large basin of the Swan-Canning Estuary has changed in ways consistent with deteriorating environmental conditions in that estuary. Between 1986/7 and 2003/4, the compositions of that fauna altered markedly at the species and even family levels. Thus, the densities and number of species of molluscs, and especially of crustaceans, which are particularly susceptible to environmental stress, declined, while those of the more tolerant polychaetes increased. However, taxonomic distinctness declined consistently only at one of the four widely-spaced sampling sites and the dispersion of samples did not differ markedly between periods, indicating that the benthic fauna has not undergone such extreme changes as in the nearby Peel-Harvey Estuary. It is thus proposed that benthic macroinvertebrates can act as important indicators of the severity of environmental degradation in microtidal estuaries in regions where such perturbations are increasing. PMID:21195437
Wildsmith, M D; Rose, T H; Potter, I C; Warwick, R M; Clarke, K R
We document invertebrate benthic and drift dynamics in a regulated river in central Spain at two temporal scales: seasonal (for both benthos and drift) and daily (for drift). The benthic abundance of individuals and taxon richness generally increased in the summer. Drift abundance showed no seasonal or daily variation, but taxon richness of drifting individuals was higher in the spring. Both ben-thos and drift showed clear seasonal changes in taxonomic composition. Interestingly, some benthic taxa showed their highest abundances in the spring, while others were more abundant in the summer. In contrast, most drifting taxa were more abundant in the spring. Different functional feeding groups showed different patterns of variation throughout the year, both in the benthos and the drift. Daily variations in drift were present in very few taxa and functional feeding groups, and only in some seasons.
Benthic invertebrate communities are evaluated as part of the ecological survey component of the U.S. Geological Survey's National Water-Quality Assessment Program. These biological data are collected along with physical and chemical data to assess water-quality conditions and to develop an understanding of the factors that affect water-quality conditions locally, regionally, and nationally. The objectives of benthic invertebrate community characterizations are to (1) develop for each site a list of tax a within the associated stream reach and (2) determine the structure of benthic invertebrate communities within selected habitats of that reach. A nationally consistent approach is used to achieve these objectives. This approach provides guidance on site, reach, and habitat selection and methods and equipment for qualitative multihabitat sampling and semi-quantitative single habitat sampling. Appropriate quality-assurance and quality-control guidelines are used to maximize the ability to analyze data within and among study units.
Cuffney, Thomas F.; Gurtz, Martin E.; Meador, Michael R.
A study of chemical and sedimentological parameters integrated with benthic foraminifera investigation was conducted along the northern coast of Gabes Gulf. Thirty-two samples were studied and a total of 68 benthic foraminiferal species were identified. Heavy metals enrichment factors and total hydrocarbon concentrations showed both metal and petrogenic pollution related mainly to phosphogypsum, sewage, and fishing activities. Statistical analysis (bivariate correlation and hierarchical cluster analysis) show a possible control of these pollutants on density, diversity, as well as the taxonomic composition of the benthic foraminiferal assemblages. The extent to which the population was found less dense and less diversified corresponded to the degree to which the sediment was contaminated. In these contaminated sites, an increase in relative abundance of opportunistic species such Ammonia tepida and Haynesina germanica was found. Far from pollution, foraminiferal assemblages are dominated by species characteristic of Mediterranean shallow water (Ammonia beccarii, Ammonia parkinsoniana, Elphidium crispum, Elphidium williamsoni, Elphidium advenum, Peneroplis planatus, Peneroplis pertesus). PMID:21476104
Biomonitoring of estuarine pollution is the subject of active research, and benthic foraminifera are an attractive group to use for these purposes due to their ubiquitous presence in saline water and wide diversity. Here, we describe a case study of biomonitoring using benthic foraminifera in the French Mediterranean lagoon, Bages-Sigean lagoon. In this case, the major pollutants of interest are heavy metals in the sediment, particularly contaminated by Cu and Cd derived from industrial and agricultural sources. The foraminiferal assemblages of the Bages-Sigean lagoon are typical of normal paralic environments, but unusually almost completely lack agglutinated forms. The density of benthic foraminifera was shown to be more influenced by the sediment characteristics rather than heavy metal pollution. However, the relative abundance of Quinqueloculina bicostata was shown to increase in the most polluted areas and we propose that this taxon may be used as an indicator of heavy metal pollution. PMID:22321172
Foster, William J; Armynot du Châtelet, Eric; Rogerson, Mike
In July 1980, a study was initiated to estimate the effects of the H. A. Wagner Steam Electric Station (SES) on the benthic and finfish assemblages of Baltimore's Outer Harbor and the Patapsco River. This benthic study, conducted from July 1980 to early June 1981, was designed to determine whether shifts in benthic species composition and abundance, out-of-phase reproductive activity,
Zebra mussel, Dreissena polymorpha (Pallas), proliferation in Saginaw Bay, Lake Huron is associated with increased water clarity and increased light levels on benthic substrata in the littoral zone. We hypothesized that the filtering activities of Dreissena and associated increases in light penetration should affect the structure and function of benthic algae in the bay. Monthly quantitative benthic algal samples were
Oxygen respiration rates of benthic foraminifera are not well documented because of the difficulties to measure them. However, the determination of the respiration rates of benthic foraminifera is important in order: 1) to compare the metabolic rates of different species, of various size, and with different microhabitats in the sediment; 2) to estimate the contribution of benthic foraminifera in the aerobic mineralization of organic matter. Benthic foraminifera from 4 different natural environments were used: three species from the intertidal rocky shore of Yeu island, two species from the muddy Bay of Aiguillon, two species from the Bay of Biscay and eleven species from the Rhône prodelta (France). Living foraminifera were placed in a small tube, in which oxygen gradients were determined using oxygen microelectrodes. Respiration rates were calculated on the basis of the oxygen fluxes measured in the vivinity of the foraminiferal specimens. Foraminiferal biovolumes were estimated on the basis of the overall shape of the various species (for example, Ammonia is assimilated to a half sphere) and the width of the shell walls. The results show a wide range of respiration rates according to the species (around 90 to 5300 pmol. cell-1.day-1) and a clear correlation with the biovolume of the foraminifera. No clear relationship between respiration rates and microhabitat is observed. A comparison with previously published data shows that our estimations are generally lower for the small size species. For example, the respiration rate estimations published recently by Nomaki et al. (Journal of Foraminiferal Research, 37, 281-286, 2007) show a range of 900 to 10 000 pmol. cell-1.day-1. The total contribution of benthic foraminifera in the aerobic mineralization of organic matter is estimated for the studied areas. The first results suggest a minor role of benthic foraminifera in this process, which strongly contrasts with their strong contribution to anaerobic mineralisation of organic matter in the same areas (Pina-Ochoa et al., PNAS, 2009).
Geslin, Emmanuelle; Risgaard-Petersen, N.; Langlet, D.; Metzger, E.; Jorissen, F.
Omnivory has an important role in the movement of energy, nutrients, and contaminants between benthic and pelagic food webs. While top-predator fish are known to supplement a mostly piscivorous diet with benthic organisms, a more obscure benthic-pelagic coupling occurs when benthic invertebrates forage on fish carcasses, referred to as necrophagy. The combination of these two benthic-pelagic links, top-predator fish feeding on benthic organisms that have fed on dead fish, can generate a trophic feedback cycle that conserves energy and nutrients and may have implications for biomagnification of methylmercury (MeHg) in fish. We investigated the role of necrophagy by crayfish (Procambarus clarkii), via a trophic feedback cycle, on the biomagnification of MeHg in largemouth bass (Micropterus salmoides), a cosmopolitan top predator fish known to feed on crayfish. Controlled laboratory tests quantified the uptake of MeHg by both organisms from artificial and natural food (whole crayfish or bass tissue). Assimilation efficiency (AE) of MeHg was greater for bass fed crayfish (79±0.5%) than those fed artificial food (60±3%). Furthermore, AE of MeHg was greatest for largemouth bass fed crayfish that fed on MeHg-dosed dead fish (i.e., trophic feedback cycle; 94±17%). A model, parameterized with results of the laboratory experiments, was used to make steady-state projections of MeHg biomagnification factors. Model projections also indicate that MeHg biomagnification would be greatest for largemouth bass from a trophic feedback cycle. These results suggest that food web ecology has an important role in determining MeHg levels in predatory fish and underscore the need for further investigation into the magnitude that necrophagy may affect MeHg biomagnification in aquatic systems. PMID:21356175
Bowling, Anna M; Hammerschmidt, Chad R; Oris, James T
In this activity (on pages 11-12 of PDF) learners create models of lava layers that have formed on the moon. The model is created by mixing a series of different colored vinegar with baking soda, then using colored play dough to cover wet areas where each color of "lava" erupted. Clear straws are pushed into the thickest part of the finished layers to get a "core sample." Groups can present their findings and a list of questions is provided to guide students to a deeper understanding. The activity is part of a larger curriculum based on a video on DVD, which you can request for free by emailing email@example.com.
The Planetary Geology Group at Arizona State University developed this online activity to teach elementary and middle school students "the stratigraphy (layers) of lava flows produced by multiple eruptions" on the moon. The first part of the website provides teachers with background information about the layers of basaltic lava flows that cover about sixteen percent of the Moon as well as how to prepare for the activity and what to expect. Visitors can use the second part of the website as an instruction sheet for the students. The website describes how users can examine the patterns of lava flows on the moon with the help of four simple ingredients: baking soda, vinegar, food coloring, and paper cups. The questions provided at the end will help students understand the process that is taking place in their experiments.
In this study we quantified invertebrate drift and related it to the structure of the benthic community, over a 68 month\\u000a period, in a 4th-order tropical stream in Costa Rica. Relative to reports from similar-sized temperate and tropical streams,\\u000a drift densities were high (2-fold greater: mean 11.2 m?3; range 2.525 m?3), and benthic insect densities were relatively low (>3-fold lower:
General comparisons were made between benthic organism samples collected in 1960-61 and 1972-73 from five sites in the Sacramento River between Red Bluff and Knights Landing, Calif. The composition of benthic organisms from both collection periods was similar. The 1972-73 data showed variable patterns in monthly changes at each site and downstream changes each month with number of organisms per square meter, number of taxa per square meter, and diversity index. Generally, the mean number of taxa per square meter and diversity index for all sampling periods were higher in the upper reach than the lower reach of the Sacramento River. (Woodard-USGS)
Benthic invertebrates from 44 reference streams throughout the state of Missouri were examined for their concordance with established regionalization systems, both aquatic and terrestrial. Invertebrate assemblages coincided nicely with Pflieger's established aquatic faunal regions system, expanding its generality to more than fish assemblages. Our benthic invertebrate and Pflieger's fish assemblages coincided well with both Bailey's ecological sections and Omernik's ecoregions. Subregionalization using Pflieger's subregions and Bailey's subsections further reduced unexplained variation and is recommended for use wherever possible. The concordance of the aquatic fauna and terrestrial features implies the possibility of coordinated regional management among different natural resource disciplines.
Benthic macrofauna and ancillary data were collected during 1987 as part of the U.S. Geological Survey Regional Effects Monitoring Program in San Francisco Bay, California. Data were collected during five cruises at 2-month intervals from March through November. Benthic macrofauna for identification of species and sediment for size analysis were sampled at eight stations. Ancillary data, which consisted of salinity, temperature, dissolved-oxygen concentrations, and suspended sediment, were collected at 12 stations. Salinity and temperature were measured at three stations that coincided with continuous water quality monitors. Abundances and geographical distributions of a newly introduced species of clam were measured. (USGS)
Schemel, Laurence E.; Ota, A. Y.; Harmon, J. G.; Shay, J. M.; Adorado,R. N.
Benthic foraminiferal Mg/Ca paleothermometry is based on an empirical relationship between the Mg/Ca of benthic foraminifera recovered from core tops and in situ bottom water temperatures (Rosenthal, 1997; Martin et al, in press; Lear et al, in review). While there is a tight correlation between shell Mg/Ca and temperature over a broad range of temperatures (-1 to 20 degrees C), Mg/Ca variation over the small range of deep water temperatures reveals departures from the calibration curve at low temperatures. Lower Mg/Ca values are generally associated with the deepest sites from the Atlantic and Pacific, contributing to an apparently steeper Mg/Ca-T response for abyssal benthics. The steeper response of abyssal benthics may reflect an influence of decreasing carbonate saturation with depth. Dissolution or other saturation related effects have already been documented for Mg in planktonic foraminifera and for other metals (Cd, Ba, and Zn) in benthic foraminifera shells (see Marchitto and ref. therein). Although it is difficult to definitively separate the effects of various environmental parameters (including temperature, depth, and relative saturation states), which often change in unison, we can use to the core top Mg/Ca data to estimate the potential influence of saturation state. An alternative calibration of the benthic Mg/Ca - T relationship can be derived based on core top benthic foraminifera only from sites bathed in waters above carbonate saturation, which yields a slightly smaller change in Mg/Ca per degree C (~9.5% vs. 11%) but better explains benthic Mg/Ca from the coldest sites (-1oC). Using this alternative Mg/Ca -T relation and a subset of the data from the Ceara Rise and Ontong Java Plateau, we can estimate a maximum Mg/Ca offset attributable to saturation state. The uncertainty this implies for downcore reconstructions varies widely (exceeding 1.5oC), depending on the hydrographic setting and which proxy is used to estimate saturation state.
Structural and functional parameters of planktonic and benthic communities in the White Sea were studied both at the sites of industrial mussel cultivation farms (MF) and in aquaculture free areas. Redistribution of organic matter in pelagic and bottom systems close to MF was shown to result in changes of the structure of the surrounding biocoenoses. The consumption of proteins by mussels led to a drastic decrease in the relative abundance of planktonic bacteria, while the composition and abundance of the zooplanktonic community were not affected by MF. A significantly uneven distribution was found in the bottom habitats, which results in organic contamination and, in some cases, in degradation of benthic communities.
Primakov, I. M.; Ivanov, M. V.; Lezin, P. A.; Kulakowski, E. E.; Sukhotin, A. A.
Predators capture prey in complex and variable environments. In the ocean, bottom-dwelling (benthic) organisms are subjected to water currents, waves, and turbulent eddies. For benthic predators that feed on small animals carried in the water (zooplankton), flow not only delivers prey, but can also shape predator-prey interactions. Benthic passive suspension feeders collect prey delivered by movement of ambient water onto capture-surfaces, whereas motile benthic predators, such as burrow-dwelling fish, dart out to catch passing zooplankton. How does the flow of ambient water affect these contrasting modes of predation by benthic zooplanktivores? We studied the effects of turbulent, wavy flow on the encounter, capture, and retention of motile zooplanktonic prey (copepods, Acartia spp.) by passive benthic suspension feeders (sea anemones, Anthopleura elegantissima). Predator-prey interactions were video-recorded in a wave-generating flume under two regimes of oscillating flow with different peak wave velocities and levels of turbulent kinetic energy ("weak" and "strong" waves). Rates of encounter (number of prey passing through a sea anemone's capture zone per time), capture (prey contacting and sticking to tentacles per time), and retention (prey retained on tentacles, without struggling free or washing off, per time) were measured at both strengths of waves. Strong waves enhanced encounter rates both for dead copepods and for actively swimming copepods, but there was so much variability in the behavior of the live prey that the effect of wave strength on encounter rates was not significant. Trapping efficiency (number of prey retained per number encountered) was the same in both flow regimes because, although fewer prey executed maneuvers to escape capture in strong waves, more of the captured prey was washed off the predators' tentacles. Although peak water velocities and turbulence of waves did not affect feeding rates of passive suspension-feeding sea anemones, increases in these aspects of flow have been shown to enhance feeding rates and efficiency of motile benthic fish that lunge out of their burrows to catch zooplankton. Faster, more turbulent flow interferes with the ability of prey to detect predators and execute escape maneuvers, and thus enhances capture rates both for passive suspension-feeding predators and for actively swimming predators. However, prey captured in the mouths of fish are not washed away by ambient flow, whereas prey captured on the tentacles of suspension feeders can be swept off before they are ingested. Therefore, the effects of flowing water on predation on zooplankton by benthic animals depend on the feeding mode of the predator. PMID:23942646
Despite some promising work demonstrating that the geochemistry of large benthic foraminifera (LBF) faithfully records their environment [e.g. 1], the full potential of these organisms for palaeoclimate reconstruction has not been realised. Planktic foraminifera are routinely used to assess the temperature and pH (amongst other parameters) of the past oceans but are short lived and currently offer only limited information regarding seasonal change. In contrast, LBF may live for several years, particularly the large and widespread Paleogene genera such as Nummulites . These foraminifera therefore offer the potential for quantitative reconstruction of seasonal changes of ambient seawater temperature and chemistry. In order to investigate the use of LBF for seasonal palaeoclimate and palaeoceanographic reconstruction we analysed both recent and Eocene Operculina ammonoides (from five different reefs in SE Asia and the Great Barrier Reef) as well as Eocene Nummulites djokdjokartae and N. laevigatus (from Java and England respectively). Our results are obtained using the LA-ICPMS system at RHUL featuring a two-volume LA cell characterised by uniform signal response and rapid washout , enabling intratest compositional variability to be assessed on a ?m scale. Our results show that recent O. ammonoides modifies its calcite test chemistry according to its environment. Moreover, our data demonstrate that, as in planktic foraminifera, a systematic relationship exists between Mg/Ca and temperature thus enabling the use of LBF for palaeotemperature reconstructions. Because the Nummulitids have a similar peak abundance range to planktic species usually considered to be surface dwelling (20-40 m), results derived from LBF can be considered to be representative of sea surface temperatures. Because the relationship between seawater Mg/Ca and test Mg/Ca has also been calibrated for a Nummulitid (Heterostegina depressa) , our data can also be used to better constrain the Mg/Ca ratio of Eocene seawater. Knowledge of this variable is vital for accurate palaeoclimate reconstruction using the Mg/Ca temperature proxy. In addition to Mg/Ca, we have also investigated the use of these organisms as recorders of other important palaeoenvironmental and ocean-chemistry archives. Preliminary data appear to suggest that the use of B/Ca as a pH proxy appears to be viable in the Nummulitids. Furthermore, it appears that inter-ocean differences in chemistry can be evaluated. Finally, the variability of certain trace element systems in LBF calcite can be related to salinity, potentially offering a new and quantitative palaeosalinity proxy.  Wefer & Berger, 1980, Science, 209:803.  Purton & Brasier, 1999, Geology, 27(8): 711.  Müller et al., 2009, JAAS, 24: 209.  Segev & Erez, 2006, Geochem. Geophys. Geosyst., 7(2).
Marine bacteria, actinomycetes and fungal strains were isolated from continental slope sediment of the Bay of Bengal and studied\\u000a for fatty acid profile to investigate their involvement in the benthic food-web. Fifteen different saturated and unsaturated\\u000a fatty acids from bacterial isolates, 14 from actinomycetes and fungal isolates were detected. The total unsaturated fatty\\u000a acids in bacterial isolates ranged from 11.85
The long-term benthic disturbance experiment (BENDEX) was started on the eastern Weddell Sea shelf off Austasen (Antarctica)\\u000a during Polarstern cruise ANT XXI\\/2 in December 2003 to simulate the impact of grounding icebergs on the seabed and follow\\u000a the steps and timescales of recovery of disturbed benthos and demersal fish communities. Here, we report the basic approach\\u000a and first results for
D. Gerdes; E. Isla; R. Knust; K. Mintenbeck; S. Rossi
The River Wupper, a tributary of the River Rhine, is at several locations influenced by anthropogenous nitrogen input, hydraulic structures, and influents from other tributaries. These influences have an impact both on the water quality and on the hydrodynamic conditions. The model approaches used for this article are based on work of Rauch et al. and the River Water Quality Model No. 1; they allow the simulation of the nitrogen conversion in the River Wupper. They are compatible with the activated sludge models and can thus be used also for integrated approaches. The calibration and validation of the model was realized using actual data of the River Wupper over a length of 60 km with one dam, 10 weirs, three wastewater treatment plants and 11 tributaries. The model considers the nitrogen conversion and COD removal and has a strong focus on biofilm processes in the benthic zone. Additional information is given about the sedimentation processes, the physical oxygen input processes, biofilm detachment processes, molecular diffusion, the influence of the laminar border layer and the changing of COD fractions and biofilm densities. PMID:16838700
Wichern, M; Kehl, O; Erbe, V; Luebken, M; Wilderer, P A
Reliable estimates of bottom-water oxygen contents are crucial to understand the formation of past oxygen-depleted environments. Here, we investigate the relationship between pore density in calcareous benthic foraminiferal (BF) tests and measured oxygen concentrations of the surrounding bottom-waters (BW-O2) in living (Rose Bengal stained) specimens of the shallow-infaunal species Bolivina pacifica, and the three deep-infaunal species Fursenkoina mexicana, Globobulimina turgida, and Chilostomella oolina. Used samples span a wide oxygen-gradient across oxygen minimum zones (OMZ) off Namibia and Pakistan. Bolivina pacifica, F. mexicana and G. turgida display a significant negative exponential correlation between the pore density and BW-O2, indicating a morphological response of the foraminifers to decreasing oxygenation. Supporting previous results, we suggest that an increasing number of pores improves the ability of oxygen uptake in low-oxygen environments. This morphological response can be used to establish an independent proxy for BW-O2. The inter-specific comparison of the dependency of pore density and BW-O2 reveals a steeper gradient for B. pacifica than for F. mexicana, and G. turgida. We hypothesize that the inter-specific pore density-BW-O2-relationship may reflect their species-specific microhabitat preferences. The shallow-infaunal species B. pacifica is probably stronger affected by oxygen depletions than the two deep-infaunal species F. mexicana, and G. turgida. Our results for the deep-infaunal species C. oolina show no significant relationship between pore density and BW-O2. This suggests that C. oolina has another life-strategy to survive sustained low-oxic conditions than increasing its pore density. Overall, we propose that the pore density of individual BF species provides a valuable independent proxy to reconstruct ancient bottom-water oxygenation. To test the application of this proxy in fossil assemblages, we used the organic-carbon rich sapropel layer S1 in two cores from the North Agean Sea to illustrate the decrease in BW-O2 before and during the sapropel formation as well as the BW-O2 increase afterwards.
The ecotoxicological effects of oil spill from the grounded vessel MV River Princess on the intertidal benthic organisms of SinquerimCandolim beach at Goa were investigated. An intertidal expanse of 1 km on either side of the grounded vessel was selected to evaluate the concentration of total petroleum hydrocarbon (TPH) in the sediment and its effects on the composition, abundance and
B. Ingole; S. Sivadas; R. Goltekar; S. Clemente; M. Nanajkar; R. Sawant; C. D'Silva; A. Sarkar; Z. Ansari
The colonization characteristics of benthic microalgae communities on artificial substrata were analyzed in four shallow lakes of different trophic status. Colonizations in lower nutrient lakes with macrophytes (Niuchao Lake and Langzi Lake) had longer lag phases, lower peak biomasses, and had longer times to community maturity than the higher nutrient lakes without macrophytes (Nanhu Lake and Donghu Lake). Hypereutrophic Nanhu
SUMMARY 1. We conducted survey and transplant studies to determine whether colonization and residency on soft sediments by introduced, fouling mussels (Dreissena polymorpha and D. bugensis) were affected by physical disturbance, and whether Dreissena presence in turn influenced the diversity and population densities of other benthic invertebrates. Surveys revealed that colony density was typically higher at moderate depths than at
Chemosynthetic benthic communities, which live symbiotically with microbes capable of metabolizing nutrients dissolved in water seeping out of the seafloor, are widespread along the Cascadia subduction zone. These seeps and vents are therefore indicative of one mode of fluid migration out of the subduction zone sediments. We have used deep-towed seismic methods, including hydrophones mounted on Alvin, to examine the
Chemosynthetic benthic communities, which live symbiotically with microbes capable of metabolizing nutrients dissolved in water seeping out of the seafloor, are widespread along the Cascadia subduction zone. These seeps and vents are therefore indicative of one mode of fluid migration out of the subduction zone sediments. The authors have used deep-towed seismic methods, including hydrophones mounted on Alvin, to examine
Muskegon Lake was designated an Area of Concern because of severe environmental impairments from direct discharge of industrial and municipal wastes. Since diversion of all municipal and industrial wastewater in 1973, few studies have assessed ecological changes associated with improved water quality. We examined distributions and long-term changes in the benthic macroinvertebrate community at 27 sites. Distributions were evaluated relative
Glenn S. Carter; Thomas F. Nalepa; Richard R. Rediske
The influence of the River Danube as a major source of nutrients and suspended solids to the continental shelf of the Black Sea has been analyzed. In the framework of the EC project EROS-2000, sediment cores from 33 stations on the northwestern continental shelf were sampled in August 1995. Spatial patterns in structural sediment characteristics, macrobenthos composition and benthic mineralization
The sediments of Poplar Creek and the Clinch River are contaminated with a wide variety of chemicals, including heavy metals, polycyclic aromatic hydrocarbons, and PCBs. Sources include the US Department of Energy`s Oak Ridge Reservation as well as both known and unidentified upstream activities. The authors investigated the risks to benthic invertebrates posed by chemicals in these sediments as part
Daniel S. Jones; Lawrence W. Barnthouse; Glenn W. Suter II; Rebecca A. Efroymson; Jennifer M. Field; John J. Beauchamp
The serial discontinuity concept (SDC; Ward and Stanford, in Ecology of River Systems, 1983) predicts that recovery of large regulated rivers over distance downstream from a dam is limited by relative tributary size; however, channel geomorphology may also influence the recovery process. We examined the spatial variation in water quality, benthic composition and ash-free dry standing biomass (AFDM) among the
Lawrence E. Stevens; Joseph P. Shannon; Dean W. Blinn
This paper summarizes results from the first science deployment of the Autonomous Benthic Explorer (ABE), conducted on the Juan de Fuca Ridge (46°N, 129°W) at depths between 2200 and 2400 m. Using long baseline acoustic transponders, the ABE descended with precision to a preassigned starting point, then executed dead-reckoned tracklines. It followed the bottom at distances between 7 and 20
Dana R. Yoerger; Albert M. Bradley; Barrie B. Walden; Hanumant Singh; Ralf Bachmayer
The Self-Organizing Map (SOM) was used for revealing the ecological states of streams in recovery through patterning of benthic macroinvertebrate communities. SOM was capable of showing different clusters of the sample sites in a small scale according to changes in environmental variables such as water velocity, depth, substrate roughness and the amount of silt. Community abundance correspondingly varied in different
High altitude creates unique challenging conditions to biota that limit the diversity of benthic communities. Because environmental pollution may add further stress to life at high altitude, the present study explored the effect of metal pollution on the macroinvertebrate community composition in Andean streams between 3,500 to 4,500 meters above sea level (masl) during wet and dry seasons. At polluted
Raúl A. Loayza-Muro; Rafaela Elías-Letts; Jenny K. Marticorena-Ruíz; Edwin J. Palomino; Joost F. Duivenvoorden; Michiel H. S. Kraak; Wim Admiraal
Sediment and water can potentially be altered, chemically, physically and biologically as they are sampled at the seafloor, brought to the surface, processed and analysed. As a result, in situ observations of relatively undisturbed systems have become the goal of a growing body of scientists. Our understanding of sediment biogeochemistry and exchange fluxes was revolutionized by the introduction of benthic
E. Viollier; C. Rabouillesupbsu; S. e. Apitz; E. Breuer; G. Chaillou; K. Dedieu; Y. Furukawa; C. Grenz; P Hall; F Janssen; J. L Morford; J.-C Poggiale; S Roberts; T Shimmield; M Taillefert; A Tengberg; F Wenzhöfer; U Witte
A microcosm experiment was used to compare the influence of diesel contamination on two benthic salt-marsh communities, one chronically exposed to petroleum hydrocarbons for decades (Louisiana [LA]) and the other relatively uncontaminated (Mississippi [MS]). Initial meiofaunal community composition of the two sites was similar. Higher organic content of MS sediments should have reduced bioavailability, and thus the toxicity of hydrocarbons
Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites
A recent major discovery has been the rapid sedimentation of phytodetritus to the deep-sea floor1-3 Although benthic mega-faunal invertebrates appear to seek out this relatively fresh food source1,4, and its seasonal arrival on the sea floor may synchronize reproduction in some echinoderms5, a convincing response by ben-thic organisms to phytodetritus has not been demonstrated3. Here I present evidence that certain small benthic Foraminifera (within the meiofaunal size-range) react dramatically to the presence of phytodetritus. Fresh aggregates of this material harbour abundant, low-diversity populations of these protists. The three commonest species are usually poorly represented in the more diverse assemblages inhabiting the underlying sediment. These findings suggest that some deep-sea benthic Foraminifera, like their shallow-water relatives6-8, are specialist feeders that bloom opportunistically when the appropriate food (phytodetritus and associated micro-organisms) becomes available, while others remain unaffected by the organic influx.
The Western Trough of the Lough Hyne Marine Reserve in southern Ireland features annual episodes of profound hypoxia beneath an oxy-thermocline that develops each summer. Previous work had indicated that the hypoxia caused mass mortality of the sessile benthic fauna, but information about the winter fauna, or about mobile species was lacking. Here we report on a combined remote-operated vehicle,
Rob McAllen; John Davenport; Karl Bredendieck; Declan Dunne
Four species of estuarine benthic diatoms: Amphiprora c. f. paludosa W. Smith, Nitzschia c. f. dissipata (Kützing) Grunow, Navicula arenaria Donkin, and Nitzschia sigma (Kützing) W. Smith were grown in unialgal cultures. The growth rates of the diatoms were determined as the rate of increase of the chlorophyll a content of the cultures. The diatoms were cultured at different combinations
During the past few years Archaea have been recognized as a widespread and significant component of marine picoplankton assemblages and, more recently, the presence of novel archaeal phylogenetic lineages has been reported in coastal marine benthic environments. We investigated the relative abundance, vertical distribution, phylogenetic composition, and spatial variability of Archaea in deep-sea sediments collected from several stations in the
COSTANTINO VETRIANI; HOLGER W. JANNASCH; BARBARA J. MACGREGOR; DAVID A. STAHL; ANNA-LOUISE REYSENBACH
Sedimentary bacteria have generally been recognized as an essential food for protists and invertebrates, forming the base of benthic food webs. This trophic role has been well documented, but bacteria play an equally important role as mineralizers of organic detritus and recyclers of essential nutrients. Recent evidence suggests that this latter role is more important than their trophic function in
The impact of Dreissena (Dreissena polymorpha and D. bugensis) on the benthic bacterial community in lakes is largely unknown. Therefore, we quantified differences in the structure and\\u000a activity of bacterial communities living in sediments (1) associated with Dreissena clusters, and (2) unassociated with established clusters (lake bottom sediments). Dreissena clusters and sediments were collected from locations in Lake Erie, Lake
Rachel N. Lohner; Von Sigler; Christine M. Mayer; Csilla Balogh
Linear regressions produced low correlation coefficients relating the number of taxa/sample, total number of organisms/sample, sample diversity, and percentage composition of selected orders of invertebrates, with average water quality parameter values available at sampling stations. Analyses of these data by linear regressions explained little of the variability in benthic invertebrate samples primarily because the distributions of benthic organisms along environmental gradients are nonlinear. Variability in substrate characteristics in the study area and seasonal insect emergence patterns also complicated interpretation of these data. However, analysis of variance tests did indicate significant trends towards reduced number of taxa, number of organisms, and sample diversity at stations with relatively poor water quality conditions. Decreasing percentage composition of Ephemeroptera was generally accompanied by an increase in percent Diptera at stations with higher water quality constituent concentrations and acidic pH. These trends indicate significant differences in benthic communities at sites with evidence of more severe land use impacts. Additional data on benthic invertebrates, water quality, and physical habitat conditions, along with analyses of data using multivariate statistical methods are needed to define ecological relations between specific groups of invertebrates and environmental conditions. 44 refs., 1 fig., 8 tabs.
The source of the background hydrocarbons in benthic sediments of Prince William Sound (PWS), AK, where the 1989 Exxon Valdez oil spill (EVOS) occurred, has been ascribed to oil seeps in coastal areas of the Gulf of Alaska (GOA). The authors present evidence that coal is a more plausible source, including (i) high concentrations of total PAH (TPAH), between 1,670
Jeffrey W. Short; B. A. Wright; K. A. Kvenvolden; P. R. Carlson; F. D. Hostettler; R. J. Rosenbauer
Summary 1 . Interference between species from different functional groups may influence ecosys- tem functioning and biological diversity. This study tested whether interactions between predacious cutthroat trout and an omnivorous signal crayfish modified the crayfish's trophic and engineering effects within a detrital-based, stream benthic community. 2. We show in a trough experiment that omnivorous crayfish through their trophic and engineering
Yixin Zhang; John S. Richardson; Junjiro N. Negishi
Murrell, M.C., J.D. Hagy, J.G. Campbell and J.M. Caffrey. In press. Benthic and Water Column Processes in a Subtropical Estuary: Effects of Light on Oxygen Fluxes (Abstract). To be presented at the ASLO 2004 Summer Meeting: The Changing Landscapes of Oceans and Freshwater, 13-18 ...
SUMMARY 1. In eutrophic lakes, large amounts of the cyanobacterium Microcystis may overwinter in the sediment and re-inoculate the water column in spring. 2. We monitored changes in pelagic and benthic populations of Microcystis in Lake Volkerak, The Netherlands. In addition, sedimentation rates and the rate of recruitment from the sediment were measured using traps. These data were used to
JOLANDA M. H. V ERSPAGEN; KLAUS D. J OHNK; W. I BELINGS; LUUC R. M UR; J EF H UISMAN
Anthropogenic acidification has deleterious effects on both structure and functioning of surface water ecosystems. This study examined how it may affect the leaf decomposition rate and the community structure and activity of decomposers in both benthic and hyporheic zones of five headwater streams along an acidification gradient from highly acidic (pH 4.6) to circumneutral (pH 7.4). Overall, responses to acidification in hyporheic zones were less pronounced, but followed the same pattern as in their benthic counterparts. Leaf decomposition was much faster in the circumneutral stream, both in the hyporheic and benthic zones (k = 0.0068 and 0.0534 d(-1), respectively), than in the most acidic one (k = 0.0016 and 0.0055 d(-1), respectively), and correlated well with the acidic gradient in both compartments. Interestingly, leaf litter decomposition was less affected by acidification in hyporheic compared to benthic compartments, likely due to the relatively low sensitivity of fungi, which were the main decomposers of buried coarse particulate organic matter. These results argue in favour of conserving hyporheic habitats in acidified streams as they can maintain matter and species fluxes that are essential to the ecosystem. PMID:23069077
Traditional classifications of developmental patterns of marine benthic invertebrates are based on combinations of embryological (direct or indirect development) and ecological (such as nutritional source or habitat) characteristics. Different schemes have been proposed for different reasons, relating to ecology, evolution and\\/or development. However, these classifications contain interconnected characters that do not efficiently discriminate between developmental patterns and, thus, do not
Élie Poulin; Sigurd v. Boletzky; Jean-Pierre Féral
At each of 60 sites, we collected benthic macroinvertebrates using six different protocols (including the EMAP methods for non-wadeable rivers) and physical habitat data using the USEPA-EMAP-SW protocols for non-wadeable rivers. We used PCA with physical habitat data and DCA wit...
An integration of sediment physical, chemical, biological, and toxicity data is necessary for a meaningful interpretation of the complex sediment conditions in the marine environment. Assessment of benthic community is a vital component for that interpretation, yet their evaluation is complex and requires a large expenditure of time and funds. Thus, there is a need for new tools that are
The study of the opossum shrimp (Mysis relicta) at Twin Lakes, Colo., is part of an investigation into the potential impacts of pumped-storage power generation on the two lakes. Since 1974, large and small benthic sled-type trawls have been used monthly t...
The community composition of benthic macroinvertebrates from 870 estuarine sites was examimed in order to either confirm or challenge established boundaries of biogeographical provinces along the Gulf of Mexico and western Atlantic coasts of the United States. The objective was t...
Previous work had indicated that the Virginian Province Index did not perform well in a smaller estuarine complex. While it was hoped that the existing Chesapeake Bay Benthic Index of Biotic Integrity, with its greater number of metrics and habitat separation would be more adapt...
Physical and chemical conditions of sediments and benthic community composition were evaluated under syn- thetic fabric barriers, used to control aquatic macrophytes in confined areas. Macroinvertebrate density declined by 69% within 4 weeks at Eau Galle Reservoir, WI. Within a few weeks of placement at ponds near Dallas, TX, invertebrate densities declined by more than 90%. At Eau Galle Reservoir,
THOMAS A. USSERY; H. L. EAKIN; B. S. PAYNE; A. C. MILLER; J. W. BARKO
Temporal changes in coarse (> 1 mm), fine ( 250 µm), and woody benthic organic matter (BOM), and densities of detritivores in pools and riffles were monitored at three sites on two intermittent streams (Werribee and Lerderderg Rivers) in Victoria, Australia during a drought year followed by a wetter year. Standing stocks of BOM peaked in both habitats during summer
We examined the benthic fishes and artisanal fishery in the intertidal flats of Inhaca Island, Mozambique. Results of a questionnaire indicated that catches had decreased, and that piscivorous fish have disappeared. Results of a catch sampling study indicated that current catch rates are low, -1 fishing trip-1. Use of fishing gear was significantly related to season, diel and lunar tidal
Willem F. de Boer; Annemieke M. P. van Schie; Domingos F. Jocene; Alzira B. P. Mabote; Almeida Guissamulo
Seafloor geology and potential benthic habitats were mapped in West Arm, Glacier Bay National Park and Preserve, Alaska, using multibeam sonar, groundtruthed observations, and geological interpretations. The West Arm of Glacier Bay is a recently deglaciated fjord system under the influence of glacial and paraglacial marine processes. High glacially derived sediment and meltwater fluxes, slope instabilities, and variable bathymetry result in a highly dynamic estuarine environment and benthic ecosystem. We characterize the fjord seafloor and potential benthic habitats using the recently developed Coastal and Marine Ecological Classification Standard (CMECS) by the National Oceanic and Atmospheric Administration (NOAA) and NatureServe. Due to the high flux of glacially sourced fines, mud is the dominant substrate within the West Arm. Water-column characteristics are addressed using a combination of CTD and circulation model results. We also present sediment accumulation data derived from differential bathymetry. These data show the West Arm is divided into two contrasting environments: a dynamic upper fjord and a relatively static lower fjord. The results of these analyses serve as a test of the CMECS classification scheme and as a baseline for ongoing and future mapping efforts and correlations between seafloor substrate, benthic habitats, and glacimarine processes.
Hodson, Timothy O., Cochrane, Guy R.; Powell, Ross D.
Benthic macroinvertebrates play a key role when water quality assessments are made. Benthic macroinvertebrates are difficult to identify and their identification need special expertise. Furthermore, manual identification is slow and expensive process. This paper concerns benthic macroinverte-brate classification when Half-Against-Half (HAH) structure was applied to Support Vector Machine (SVM), Linear Discriminant Analysis (LDA), Quadratic Discriminant Analysis (QDA) and Minimum Mahalanobis Distance Classifier (MMDC) classifiers. Especially, LDA, QDA and MMDC classifiers were for first time applied with HAH structure to benthic macroinvertebrate classification. We performed thorough experiments altogether with ten methods. In the case of HAH-SVM we managed to improve classification results from the earlier research by using a different approach to class division problem. We obtained 96.1% classification accuracy with Radial Basis Function (RBF) kernel. Moreover, new variants of LDA, QDA and MMDC classification methods achieved 89.5% and 91.6% classification accuracies which can be considered as a good result in such a difficult classification task. PMID:24110520
The introduction of zebra mussels ( Dreissena spp.) to North America has resulted in dramatic changes to the complexity of benthic habitats. Changes in habitat complexity may have profound effects on predator-prey interactions in aquatic communities. Increased habitat complexity may affect prey and predator dynamics by reducing encounter rates and foraging success. Zebra mussels form thick contiguous colonies on both
We are developing the Large River Bioassessment Protocol (LRBP) for assessment of benthic macroinvertebrate assemblages. This multi-habitat method is currently being used in support of a REMAP project for probabilistic assessment of large rivers in USEPA Region 5. Six rivers, r...
A field study was designed to concurrently evaluate differences in colonization by benthic macroinvertebrates on a range of artificial substratum types (single particles of natural rock or clay brick and baskets of natural substratum) after three colonization periods (1, 8 and 29 days). Fauna on the artificial substrata were compared to natural substratum and the effect of natural epilithic cover
Summary 1. The impacts of trawls and dredges on marine benthic habitats and communities have been studied extensively, but mostly at small scales and over short time periods. To investigate the large-scale chronic impacts of towed fishing gears, zoned commercial fishery management systems allow comparison of habitats and communities between areas of seabed subjected to varying levels of towed-gear use.
ROBERT E. BLYTH; MICHEL J. KAISER; GARETH EDWARDS-JONES; PAUL J. B. HART
Subtidal areas of the Kermadec Islands have not previously been described; samples from a bay at Raoul Island are discussed here. Abundances and percentage cover of benthic organisms were assessed from the high intertidal to 20 m depth using quadrat sampling. Fish abundances were assessed subtidally by random transects in shallow (36 m deep) and deep (1420 m) areas of
In this study we compared macrobenthic communities collected from the Saginaw River (Michigan), Buffalo River (New York), Indiana Harbor (Indiana), Little Scioto River (Ohio), and Mill-town Reservoir (Montana) at the same locations using artificial substrates and grab samplers. Oligochaete worms (Limnodrilus hoffmeisteri) were the predominant benthic organisms in sediment samples collected with grab samplers. Artificial substrates also collected nothing but
Sediments in many Great Lakes harbors and tributary rivers are contaminated. As part of the USEPA's Assessment and Remediation of Contaminated Sediment (ARCS) program, a number of studies were conducted to determine the nature and extent of sediment contamination in Great Lakes Areas of Concern (AOC). This paper describes the composition of benthic invertebrate communities in contaminated sediments and is
Timothy J. Canfield; F. James Dwyer; James F. Fairchild; Pamela S. Haverland; Christopher G. Ingersoll; Nile E. Kemble; David R. Mount; G. Allen Burton; M. C. Swift
This study characterizes the composition and spatial distribution patterns of the benthic macrofauna in the intertidal mudflats of the Tagus estuary, western Portugal. A total of 68 species, more than 226,000 specimens with a total wet weight biomass of approximately 1170 g were identified in 380 sites. The species Streblospio shrubsolii, Cyathura carinata, Tharyx sp., Hydrobia ulvae and Tubificids were the
Ana Maria Rodrigues; Sónia Meireles; Teresa Pereira; Alice Gama; Victor Quintino
Hydrolytic enzyme activity, surfactancy, and dissolved organic matter in the digestive lumens of 19 benthic echinoderm and polychaete species were examined, using consistent and quantifiable methods. Enzyme activities were compared with those of extracellular enzymes from ambient sediments. Enzyme activities ranged over five orders of magnitude, with averages decreasing in the order polychaetes > echinoderms > sediment. Highest activities in
Lawrence M. Mayer; Linda L. Schick; Robert F. L. Selfz; Peter A. Jumars; Robert H. Findlay; Zhen Chen; Stephen Sampson
SUMMARY 1. Few studies have evaluated the effectiveness of riparian buffers in the tropics, despite their potential to reduce the impacts of deforestation on stream communities. We examined macroinvertebrate assemblages and stream habitat characteristics in small lowland streams in southeastern Costa Rica to assess the impacts of deforestation on benthic communities and the influence of riparian forest buffers on these
The role of green sea urchin Strongylocentrotus droebachiensis as a source of fecal particulate organic matter (POM) for the benthic nearshore ecosystems has been studied over a 3.5-month period. Three macroalgae were tested as food sources: Alaria esculenta, Laminaria longicruris and Ulvaria obscura. Urchins were fed ad libitum with either a single alga species or a mixture of all three
The present study represents the first quantitative investigation of deep-sea benthic infauna in Antarctica. Box cores and multicores were used to collect sediment from 12 stations across the slope and abyssal basin of the Weddell Sea and the slope off the South Sandwich Islands, including sites in the South Sandwich Trench (6300m). The multicore was a more efficient sampler than
The present study represents the first quantitative investigation of deep-sea benthic infauna in Antarctica. Box cores and multicores were used to collect sediment from 12 stations across the slope and abyssal basin of the Weddell Sea and the slope off the South Sandwich Islands, including sites in the South Sandwich Trench (6300 m). The multicore was a more efficient sampler
To assess the effects of timber harvesting on headwater streams in upland forests, benthic community structure was contrasted among four dominant forest management types (old growth, red alder-dominated young growth, conifer-dominated young growth, clearcut) and instream habitats (woody debris, cobble, gravel) in southeastern Alaska. Benthos in streams of previously harvested areas resulted in increased richness, densities and biomass relative to
The Salton Sea, California's largest inland water body, is an athalassic saline lake with an invertebrate fauna dominated by marine species. The distribution and seasonal dynamics of the benthic macroinvertebrate populations of the Salton Sea were investigated during 1999 in the first survey of the benthos since 1956. Invertebrates were sampled from sediments at depths of 212 m, shallow water
A total of 694 streams were sampled for benthic macroinvertebrates in the autumn of 1995 as part of the Swedish national stream survey. After removal of sites considered as impacted, data from 428 streams as well as a large number of environmental variables were used to determine the relative importance of local, landscape, and large scale factors in explaining the
The present study describes for the first time the species composition and toxicity of benthic cyanobacteria forming mats on the Nile River and irrigation canal sediments in Egypt. A total of 19 species of cyanobacteria were isolated from these mats during this study. The toxicity of the extracts of these species was investigated using Artemia salina assay, mouse bioassay and
Zakaria A. Mohamed; Hassan M. El-Sharouny; Wafaa S. M. Ali
The goal of this research was to distinguish meadows of native eelgrass (Zostera marina L.) from adjacent beds of benthic green macroalgae in the exposed intertidal zone of Pacific Northwest estuaries, using false-color near-infrared aerial photography. Aerial photographs of Yaq...
The benthic macroinvertebrate riffle-pool communities of two east Texas streams were sampled monthly for a period of one year. In contrast to previous studies in primarily upland areas, pools in Alazan Creek and Bernaldo Bayou contained significantly higher densities and biomass, as well as a significantly higher diversity and number of taxa. The majority of taxa collected could be characterized
The report describes results of studies conducted to obtain data to assess the effects of waste disposal on the marine environment of the New York Bight. It reports investigations of the benthic meio-fauna and macrofauna distribution in the New York Bight...
Changes in oxygen concentrations at the sediment-water interface play a major role in controlling benthic foraminiferal assemblages and morphologic characteristics; such changes are reflected in size, wall thickness, porosity, and also taxa (genera and species) of foraminifera present. These morphologic and taxonomic differences have been quantified as a dissolved-oxygen index. This paper demonstrates that the foraminiferal oxygen index derived from
Accumulative disturbances can erode a coral reefs resilience, often leading to replacement of scleractinian corals by macroalgae or other non-coral organisms. These degraded reef systems have been mostly described based on changes in the composition of the reef benthos, and there is little understanding of how such changes are influenced by, and in turn influence, other components of the reef ecosystem. This study investigated the spatial variation in benthic communities on fringing reefs around the inner Seychelles islands. Specifically, relationships between benthic composition and the underlying substrata, as well as the associated fish assemblages were assessed. High variability in benthic composition was found among reefs, with a gradient from high coral cover (up to 58%) and high structural complexity to high macroalgae cover (up to 95%) and low structural complexity at the extremes. This gradient was associated with declining species richness of fishes, reduced diversity of fish functional groups, and lower abundance of corallivorous fishes. There were no reciprocal increases in herbivorous fish abundances, and relationships with other fish functional groups and total fish abundance were weak. Reefs grouping at the extremes of complex coral habitats or low-complexity macroalgal habitats displayed markedly different fish communities, with only two species of benthic invertebrate feeding fishes in greater abundance in the macroalgal habitat. These results have negative implications for the continuation of many coral reef ecosystem processes and services if more reefs shift to extreme degraded conditions dominated by macroalgae.
Chong-Seng, Karen M.; Mannering, Thomas D.; Pratchett, Morgan S.; Bellwood, David R.; Graham, Nicholas A. J.
The Greybull River Impact Zone (GRIZ) project seeks to understand human impacts, prehistoric, historic, and present within the Greybull River drainage system, Northwest Wyoming. Stream ecology is valuable for an integrated understanding of human ecology in the region. By incorporating a nested sampling design specifically for benthic macro-invertebrate recovery which is also utilized by plant ecologists, terrestrial entomologists, and recently,
Benjamin J. Schoville; Alisa Hjermstad; Todd Wellnitz; Lawrence C. Todd
Association analysis of data on benthic macroinvertebrates in 257 samples from Georgian Bay, followed by discriminant analysis of water and sediment characteristics, facilitated a quantitative description of trophic variability within a relatively unpolluted system. Discriminating variables were bottom water temperature, water pH and Ca, sediment organic matter, sand, silt, clay, total P, Zn, Pb, and Hg. Four discriminating functions, accounting
The assumption that fossils are homogeneously distributed, at least on a small scale is common to many paleoecological studies. However, the fauna of most modern benthic marine communities from intertidal to abyssal depths is patchily distributed. Inherently heterogeneous substrates, such as rocky substrates, have patchy communities because of the diversity of microenvironments, but faunal patchiness in homogeneous environments, such as
The benthic (zoobenthos and microphytobenthos) and physical characteristics of intertidal sediments were studied in April and September 1997 on 10 locations, differing in elevation and exposure to tidal currents, situated on three mudflats in the mesohaline part of the Schelde estuary. Sediment characteristics were spatially and temporally relatively homogeneous among the sampling locations, all characterized by a high proportion of
Backscatter information from multibeam echosounders (MBES) have been shown to contain useful information for the characterisation of benthic habitats. Compared to backscatter imagery, angular response of backscatter has shown advantages for feature discrimination. However its low spatial resolution inhibits the generation of fine scale habitat maps. In this study, angular backscatter response was combined with image segmentation of backscatter imagery
Rozaimi Che Hasan; Daniel Ierodiaconou; Laurie Laurenson
A benthic index of estuarine condition was constructed for the Virginian Biogeographic Province (from Cape Cod, Massachusetts, to the mouth of Chesapeake Bay, Virginia) with data collected during summers of 1990 through 1993 by the US EPA's Environmental Monitoring and Assessment...
Benthic meiofauna were studied at 24 stations, distributed in three profiles in coral reefs named Juan Garcia, Cantiles and Diego Perez in SW of Cuba in February and July 1987. Meiofauna densities in Summer were higher than in Winter (520-4191 ind\\/10 cm 2 and 110- 2379 ind\\/10 cm 2 ). In coral reef Juan Garcia in winter prevail Nematode and
A research on the benthic fauna of Puglie's littoral in the South Adriatic Sea, the first in this area, has been initiated and is carried out through diving and dredging. Various stations and different biotopes have been investigated along about 400 km of...
We attempted to identify spatial patterns and determinants for benthic algal assemblages in Mid-Atlantic streams. Periphyton, water chemistry, stream physical habitat, riparian conditions, and land cover/use in watersheds were characterized at 89 randomly selected stream sites i...
Ecotoxicological tests with benthic organisms are recommended to assess the toxicity of hydrophobic organic contaminants like polycyclic aromatic hydrocarbons that strongly adsorb on sediments. Many routes of exposure including ingestion from sediments are taken into account with bioassays. However, organic matter of the sediments can modify chemical partitioning and toxicity of these non-polar organic contaminants. The purpose of this study
Water chemistry and benthic invertebrate communities were investigated at 37 sites on acid streams originating on the Stockton-Denniston Plateau, North Westland, New Zealand. The region is characterised by high rainfall and runoff, highly acidic soils and the presence of extensive coal measures that have been mined for over 120 years. Four groups of streams were identified: naturally acid plateau streams
We review and evaluate the design and operation of twenty-seven known autonomous benthic chamber and profiling lander instruments. We have made a detailed comparison of the different existing lander designs and discuss the relative strengths and weaknesses of each. Every aspect of a lander deployment, from preparation and launch to recovery and sample treatment is presented and compared. It is
A. Tengberg; F. De Bovee; P. Hall; W. Berelson; D. Chadwick; G. Ciceri; P. Crassous; A. Devol; S. Emerson; J. Gage; R. Glud; F. Graziottini; J. Gundersen; D. Hammond; W. Helder; K. Hinga; O. Holby; R. Jahnke; A. Khripounoff; S. Lieberman; V. Nuppenau; O. Pfannkuche; C. Reimers; G. Rowe; A. Sahami; F. Sayles; M. Schurter; D. Smallman; B. Wehrli; P. De Wilde
To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions.
Antonio Caruso; Claudia Cosentino; Luigi Tranchina; Maria Brai
Benthic macroinvertebrate populations were studied from May, 1970 to June, 1975 in the vicinity of the Monroe power plant on western Lake Erie. Samples were collected with a Ponar dredge and subsequently washed free of sediments in a 0.5 mm diameter wire ...
We evaluated the response of benthic macroinvertebrates in a Michigan trout stream to flow reduction by diverting water from a 602-m reach of Hunt Creek from June through August of 1994, 1997, and 1998. We also assessed the utility of the Physical Habitat...