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1

Antarctic Food Web Game  

NSDL National Science Digital Library

In this interactive game adapted from the Bigelow Laboratory for Ocean Sciences, build a food web that illustrates the flow of energy in an Antarctic ecosystem and the relationships between predators and prey.

Foundation, Wgbh E.

2007-08-09

2

Effects of sea-ice extent and krill or salp dominance on the Antarctic food web  

Microsoft Academic Search

Krill (Euphausia superba) provide a direct link between primary producers and higher trophic levels in the Antarctic marine food web. The pelagic tunicate Salpa thompsoni can also be important during spring and summer through the formation of extensive and dense blooms. Although salps are not a major dietary item for Antarctic vertebrate predators,, their blooms can affect adult krill reproduction

V. Loeb; V. Siegel; O. Holm-Hansen; R. Hewitt; W. Fraser; W. Trivelpiece; S. Trivelpiece

1997-01-01

3

Alteration of the food web along the Antarctic Peninsula in response to a regional warming trend  

E-print Network

Alteration of the food web along the Antarctic Peninsula in response to a regional warming trend M Abstract In the nearshore coastal waters along the Antarctic Peninsula, a recurrent shift in phytoplankton community structure, from diatoms to cryptophytes, has been documen- ted. The shift was observed

Moline, Mark

4

The Antarctic Food Chain  

NSDL National Science Digital Library

This lesson plan introduces students to the animals of Antarctica and to the Antarctic food chain. Students will draw pictures of a variety of animals and attach the pictures to a wall collage. They will then listen to or read statements about the diet of each animal and draw arrows to show which animals eat which other animals. Students will end up with a food web that illustrates the importance of krill to the Antarctic ecosystem.

5

Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf  

NASA Astrophysics Data System (ADS)

The productivity and linkages in the food web of the southern region of the west Antarctic Peninsula continental shelf were investigated using a multi-trophic level mass balance model. Data collected during the Southern Ocean Global Ocean Ecosystem Dynamics field program were combined with data from the literature on the abundance and diet composition of zooplankton, fish, seabirds and marine mammals to calculate energy flows in the food web and to infer the overall food web structure at the annual level. Sensitivity analyses investigated the effects of variability in growth and biomass of Antarctic krill (Euphausia superba) and in the biomass of Antarctic krill predators on the structure and energy fluxes in the food web. Scenario simulations provided insights into the potential responses of the food web to a reduced contribution of large phytoplankton (diatom) production to total primary production, and to reduced consumption of primary production by Antarctic krill and mesozooplankton coincident with increased consumption by microzooplankton and salps. Model-derived estimates of primary production were 187-207 g C m-2 y-1, which are consistent with observed values (47-351 g C m-2 y-1). Simulations showed that Antarctic krill provide the majority of energy needed to sustain seabird and marine mammal production, thereby exerting a bottom-up control on higher trophic level predators. Energy transfer to top predators via mesozooplanton was a less efficient pathway, and salps were a production loss pathway because little of the primary production they consumed was passed to higher trophic levels. Increased predominance of small phytoplankton (nanoflagellates and cryptophytes) reduced the production of Antarctic krill and of its predators, including seabirds and seals.

Ballerini, Tosca; Hofmann, Eileen E.; Ainley, David G.; Daly, Kendra; Marrari, Marina; Ribic, Christine A.; Smith, Walker O.; Steele, John H.

2014-03-01

6

Polar Record. Page 1 of 16. c Cambridge University Press 2013. doi:10.1017/S0032247412000757 1 Fishing down the food web of the Antarctic continental shelf  

E-print Network

Fishing down the food web of the Antarctic continental shelf and slope David G. Ainley H.T. Harvey. The history of biotic exploitation for the continental margin (shelf and slope) of the Antarctic Large Marine an attempt is made to review how the most remote ocean area in the world, the Antarctic continental shelf

Pauly, Daniel

7

Persistent organic pollutants at the base of the Antarctic marine food web.  

PubMed

Various organochlorine pesticides and brominated diphenyl ethers (BDE-47, -99, and -100) were measured in sea ice algae, water column plankton, and juvenile and adult krill collected in the Palmer Long-Term Ecological Research (LTER) region west of the Antarctic Peninsula during late austral winter and midsummer, 2001-2002. BDEs were 100-1000 times higher in ice algae and 2-10 times higher in phytoplankton than the most abundant organochlorine pesticide, hexachlorobenzene (HCB), reflecting the current production and use of BDEs versus organochlorine pesticides. However, concentrations of HCB and BDEs were significantly lower in summer plankton than in ice algae indicating lower atmospheric inputs, removal from the water column, and/or biodilution of persistent organic pollutants at the base of the food web during summer. Concentrations of HCB (juvenile and adult krill) and BDEs (juvenile krill) were not significantly different from their primary food source (ice algae, phytoplankton), and BDEs were significantly lower in adult krill versus phytoplankton, indicating no biomagnification of HCB or BDEs during transfer from plankton to krill. The high concentrations of BDEs and HCB in ice algae and associated juvenile krill illustrate the importance of sea ice as a vector for entry of POPs into the Antarctic marine ecosystem. PMID:15296304

Chiuchiolo, Amy L; Dickhut, Rebecca M; Cochran, Michele A; Ducklow, Hugh W

2004-07-01

8

The Food Web Matching Game  

NSDL National Science Digital Library

In this activity, students construct a food web of Antarctic organisms. Working from a trophic table that provides information about each organisms's role in the food web, they will attempt to place them in their correct positions on a blank food web chart. Links to a glossary are embedded in the text.

9

Food Webs  

NSDL National Science Digital Library

Food web reading. Build a food web and design a creature. Requires downloaded program. Download your assignment Food Web Assignment Sheet. Use the following sites and activities to answer the questions. Do not start the creature creator until Mr. Wood has seen your food web and completed assignment and allowed you to move on. Type your answers on the sheet and edit it to fit one page. When ...

Wood, Mr.

2010-10-06

10

Food Chain & Food Web  

NSDL National Science Digital Library

What are the differences and similarities between food chain and food web? Print (2) Garden Gate Print (1) Venn Diagram Garden Gate Venn Diagram Let's learn about the food chain and food web.Read the notes.Food Chain 4 Also, view more notes on food chain and food web. Go to the 7th title Food Chain which is before the Habitats and food chain title of the webpage.Food Chain Power Point Presentation Record what you learn ...

B, Ms.

2011-10-27

11

Forest Food Web  

NSDL National Science Digital Library

Food webs are an interconnection of producers, consumers, and decomposers. It is important to understand that a change to any level of the food web directly and indirectly affects other organisms within the food web.

Katie Hale (CSUF;Biological Sciences)

2007-07-14

12

Lesson Summary Students participate in a food web "string game"  

E-print Network

knowledge about animals in the Antarctic AAAS Science Benchmarks The Living Environment Interdependence. http://www.terraquest.com/va/science/environments/m.environments.html Excellent Antarctic Food Web the connection between Antarctic animals. Prior Knowledge & Skills -Basic knowledge about the food chain -Basic

Mojzsis, Stephen J.

13

Fun With Food Webs  

NSDL National Science Digital Library

This set of online activities consists of matching games about meadow, arctic and pond food webs. Intended for younger students, each game involves placing images of various plants and animals into their proper places in the food webs.

14

Food Chains and Webs  

NSDL National Science Digital Library

Learn more about food chains, food webs, and how the organisms in them affect each other. In class, you have learned what food webs and food chains are. Today, you will explore how the organisms in these systems interact. Step One: Food Chains What happens when you take something out of a food chain? Go to the Chain Reaction website: Chain Reaction--Food Chains This internet site will help you ...

Thompson, Ms.

2007-02-21

15

Fun With Food Webs  

ERIC Educational Resources Information Center

Explains an upper elementary game of tag that illustrates energy flow in food webs using candy bars as food sources. A follow-up field trip to a river and five language arts projects are also suggested. (CS)

Smith, Karl D.

1977-01-01

16

Food Chains and Webs  

NSDL National Science Digital Library

In this activity, learners investigate feeding relationships. Learners complete a food web and then make a mobile to represent a food chain. Use this activity to talk about predator/prey relationships and ecosystems.

Council, Biotechnology A.

2012-06-26

17

Properties of food webs  

SciTech Connect

On the assumption that systems of interacting species, when perturbed from equilibrium, should return to equilibrium quickly, one can predict four properties of food webs: (1) food chains should be short, (2) species feeding on more than one trophic level (omnivores) should be rare, (3) those species that do feed on more than one trophic level should do so by feeding on species in adjacent trophic levels, and (4) host-parasitoid systems are likely to be exceptions to (1)-(3) when interaction coefficients permit greater trophic complexity. By generating random, model food webs (with many features identical to webs described from a variety of marine, freshwater, and terrestrial systems), it is possible to generate expected values for the number of trophic levels and the degree of omnivory within webs. When compared with these random webs, real world webs are shown to have fewer trophic levels, less omnivory, and very few omnivores feeding on nonadjacent trophic levels. Insect webs are shown to have a greater degree of omnivory than other webs. The confirmation of all these predictions from stability analyses suggests that system stability places necessary, though not sufficient, limitations on the possible shapes of food webs.

Pimm, S.L.

1980-04-01

18

Oceanic Food Web  

NSDL National Science Digital Library

This visualization illustrates the carbon cycle throughout the oceanic zones, beginning at the surface and traveling to the deep. The concept map-like connections encourage students to link the abiotic and biotic interactions within the oceanic food web.

Science, Office O.; Biological and Environmental Research Information System (BERIS)

19

Planktonic microbial assemblages and the potential effects of metazooplankton predation on the food web of lakes from the maritime Antarctica and subAntarctic islands  

Microsoft Academic Search

Antarctica is the continent with the harshest climate on the Earth. Antarctic lakes, however, usually presents liquid water, at least during part of the year or below the ice cover, especially those from the sub-Antarctic islands and the maritime Antarctic region where climatic conditions are less extreme. Planktonic communities in these lakes are mostly dominated by microorganisms, including bacteria and

Antonio Camacho

2006-01-01

20

Forest Food Webs  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on the seasonal changes that affect life in a temperate forest ecosystem and how organisms in a temperate forest are dependent on one another for proper nutrition. Students describe the three major types of organisms that live in an ecosystem, three types of consumers, food webs, and food chains. They then create a food web diagram for display in their classrooms. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

2007-03-12

21

ANSWER: the Antarctic Seismic Web Resource  

Microsoft Academic Search

Research aimed at understanding the tectonic and glacial history, and present-day forces acting on the Antarctic plate involves many different workers from a diverse range of scientific disciplines. There has long been a need for a central source of information on (e.g.) earthquake hypocentres and focal mechanisms which are indicative of the strength and direction of resultant forces in the

A. M. Reading

2003-01-01

22

The Great Lakes Food Web.  

ERIC Educational Resources Information Center

Presents a play for students in grades four to nine that incorporates the scientific names, physical characteristics, feeding habits, interactions, and interdependence of the plants and animals that make up the Great Lakes food web to facilitate the learning of this complex system. Includes a Great Lakes food web chart. (AIM)

Baker, Marjane L.

1997-01-01

23

Metal dynamics in an Antarctic food chain.  

PubMed

The concentrations of copper, zinc, cadmium, selenium and mercury were determined in eggs, muscle, liver, kidney and stomach content of nestilings and adults of the Antarctic petrel, Thalassoica antarctica, and its predator, the south polar skua, Chataracta maccormicki, from Svarthamaren, Dronning Maud Land, Antarctica. The dominant food of the petrels is krill, Euphausia superba. The results show relatively high levels of cadmium in krill, which is assumed to be the main reason for the high levels of cadmium in petrels and skuas. Cadmium is almost absent in eggs, but accumulates very rapidly with age in nestlings. The copper concentrations in livers of nestling petrels reach very high levels during growth. This may be seen in connection with physiological development processes. Mercury seems to be accumulated with age and between trophic levels. Among the nestlings, the mercury levels decrease with increasing age, which may be accomplished by the excretion of mercury through the growth of feathers and as a dilution effect during growth. Selenium and mercury are inversely correlated in nestlings. The levels of zinc were similar for different nestling stages and between nestlings and adults in skuas and petrels. PMID:11488240

Nygård, T; Lie, E; Røv, N; Steinnes, E

2001-07-01

24

Food Web and Energy Flow  

NSDL National Science Digital Library

This chapter discusses the concept of a food web and energy flow. Its activities will assist students in defining and constructing an energy pyramid. These activities can be incorporated into lessons which teach students how to create a food web and and identify the interdependencies within that habitat. Students will learn how to identify and illustrate parts of the water cycle, the carbon-oxygen cycle, and the nitrogen cycle. This section also offers students the tools to demonstrate active knowledge of conservation measures.

Galle, Janet R.; Warren, Patricia A.

2005-01-01

25

KELP FOREST FOOD WEBS IN GWAII HAANAS  

E-print Network

Grazing Rates on Kelp Assimilation of Kelp-derived Organic Carbon in Kelp Forest Food Webs | 33 IntertidalKELP FOREST FOOD WEBS IN GWAII HAANAS: Ecosystem-Level Effects of Predator Depletion and Recovery

26

Food Chains and Food Webs - Balance within Natural Systems  

NSDL National Science Digital Library

With a continued focus on the Sonoran Desert, students are introduced to the concepts of food chains and food webs through a PowerPoint® presentation. They learn the difference between producers and consumers and study how these organisms function within their communities as participants in various food chains. They further understand ecosystem differences by learning how multiple food chains link together to form intricate and balanced food webs. At lesson end, students construct food webs using endemic desert species.

Vu Bioengineering Ret Program

27

Simple Rules Yield Complex Food Webs  

Microsoft Academic Search

Several of the most ambitious theories in ecology describe food webs that document the structure of strong and weak trophic links among diverse assemblages of species. Early mechanism-based theory asserted that food webs have little omnivory and several properties that are independent of species richness. This theory was overturned by empirical studies that found food webs to be much more

Neo Martinez

2003-01-01

28

INTRODUCTION Aquatic food-webs' ecology  

E-print Network

INTRODUCTION Aquatic food-webs' ecology: old and new challenges Andrea Belgrano Looking up ``aquatic food web'' on Google provides a dizzying array of eclectic sites and information (and disinformation!) to choose from. However, even within this morass it is clear that aquatic food-web research has

29

Persistence of complex food webs in metacommunities  

E-print Network

Persistence of complex food webs in metacommunities Gesa A. B¨ohme 1 and Thilo Gross 2 1 Max of Engineering Mathematics, Bristol, UK Keywords: metacommunities, food webs, predator-prey interactions, geo diversity and food web complexity. Recently Pillai et al. proposed a simple modeling framework

30

Fitting Algae Into the Food Web  

NSDL National Science Digital Library

This activity will help students understand food chains and food webs in the ocean. After studying the materials provided, students will play a food web game, in which they are given a blank food web and the names of the organisms. Students place the organisms in their correct places on the food web so that the arrows indicate the direction of energy flow. As a follow-up, students decide what would happen if they removed one of the organisms from the food web, consider the role of decomposers, and deal with geographic variation. Students should also be able to understand the importance of and need for primary producers, the interdependence of organisms, the role of bacteria in the food web, and geographic variation in food webs.

31

The soil food web: structure and perspectives  

Microsoft Academic Search

This review outlines directions for future research in soil food web ecology. Two lines of research are considered to be most important: the adoption of new methodologies to investigate food relationships and the strengthening of experimentation to investigate the interaction strength between food web components. For a better understanding of food relationships molecular methods, particularly fluorescence in situ hybridization, and

Stefan Scheu

2002-01-01

32

Got Energy? Spinning a Food Web  

NSDL National Science Digital Library

Students learn about energy flow in food webs, including the roles of the sun, producers, consumers and decomposers in the energy cycle. They model a food web and create diagrams of food webs using their own drawings and/or images from nature or wildlife magazines. Students investigate the links between the sun, plants and animals, building their understanding of the web of nutrient dependency and energy transfer.

Integrated Teaching And Learning Program

33

Live from Antarctica 2: The Food Web Game  

NSDL National Science Digital Library

This activity will help students understand that increases in the ozone hole will result in damaging ultraviolet-B (UV-B) rays penetrating deep into the ocean, and harming young marine life, such as floating fish eggs, fish larvae, juvenile fish, and shrimp larvae, and affecting phytoplankton movement. Students will discover how others in the Antarctic food web will be affected if phytoplankton are harmed by depletion of the ozone layer. They will also find out what will survive UV-B radiation in Antarctica.

34

Persistence of complex food webs in metacommunities  

E-print Network

Metacommunity theory is considered a promising approach for explaining species diversity and food web complexity. Recently Pillai et al. proposed a simple modeling framework for the dynamics of food webs at the metacommunity level. Here, we employ this framework to compute general conditions for the persistence of complex food webs in metacommunities. The persistence conditions found depend on the connectivity of the resource patches and the structure of the assembled food web, thus linking the underlying spatial patch-network and the species interaction network. We find that the persistence of omnivores is more likely when it is feeding on (a) prey on low trophic levels, and (b) prey on similar trophic levels.

Böhme, Gesa A

2012-01-01

35

Phytoplankton food quality control of planktonic food web processes  

Microsoft Academic Search

We developed a mechanistic model of nutrient, phytoplankton, zooplankton and fish interactions to test the effects of phytoplankton\\u000a food quality for herbivorous zooplankton on planktonic food web processes. When phytoplankton food quality is high strong\\u000a trophic cascades suppress phytoplankton biomass, the zooplankton can withstand intense zooplanktivory, and energy is efficiently\\u000a transferred through the food web sustaining higher trophic level production.

Marta G. Danielsdottir; Michael T. Brett; George B. Arhonditsis

2007-01-01

36

Simple rules yield complex food webs  

Microsoft Academic Search

Several of the most ambitious theories in ecology describe food webs that document the structure of strong and weak trophic links that is responsible for ecological dynamics among diverse assemblages of species. Early mechanism-based theory asserted that food webs have little omnivory and several properties that are independent of species richness. This theory was overturned by empirical studies that found

Richard J. Williams; Neo D. Martinez

2000-01-01

37

A Stochastic Theory of Community Food Webs IV: Theory of Food Chain Lengths in Large Webs  

Microsoft Academic Search

This paper develops a theory of the length of food chains in community food webs. The theory derives from a mathematical model of webs called the cascade model. Our analysis concerns the behaviour of chain lengths for webs in which the number, S, of species is large. From an exact formula for the expected number of chains of each length,

C. M. Newman; J. E. Cohen

1986-01-01

38

Historical Food Web Structure and Restoration of Native Aquatic  

E-print Network

the contemporary food web of nearby Cascade Lake, which is free from most exotic spe- cies and contains a speciesHistorical Food Web Structure and Restoration of Native Aquatic Communities in the Lake Tahoe as embedded within a broader food web context. In this study, we quantify food web changes in Lake Tahoe

Vander Zanden, Jake

39

NOAA Education Resources: Aquatic Food Webs  

NSDL National Science Digital Library

This nice site from NOAA starts with a bold statement: "Big fish eat little fish; that's how the food cycle works." It's a fitting introduction to this exploration of aquatic food webs. Offered as part of NOAA's main Education Resources site, this site offers a dozen well-produced videos, lesson plans, and data sets divided into areas that include Background Information and Multimedia. These items include "Tagging of Pacific Pelagics," "Census of Marine Life Biodiversity," and "Components of a Food Web." Visitors can also look over the Features area near the bottom of the site, whose offerings range from a profile of the Stellwagen Bank National Marine Sanctuary to a longitudinal study of sea trout in the food web. Finally, visitors can use the social media tabs to share resources from the site with colleagues and others.

2011-06-15

40

Parasites in the Wadden Sea food web  

NASA Astrophysics Data System (ADS)

While the free-living fauna of the Wadden Sea has received much interest, little is known on the distribution and effects of parasites in the Wadden Sea food web. However, recent studies on this special type of trophic interaction indicate a high diversity of parasites in the Wadden Sea and suggest a multitude of effects on the hosts. This also includes effects on specific predator-prey relationships and the general structure of the food web. Focussing on molluscs, a major group in the Wadden Sea in terms of biomass and abundance and an important link between primary producers and predators, we review existing studies and exemplify the ecological role of parasites in the Wadden Sea food web. First, we give a brief inventory of parasites occurring in the Wadden Sea, ranging from microparasites (e.g. protozoa, bacteria) to macroparasites (e.g. helminths, parasitic copepods) and discuss the effects of spatial scale on heterogeneities in infection levels. We then demonstrate how parasites can affect host population dynamics by acting as a strong mortality factor, causing mollusc mass mortalities. In addition, we will exemplify how parasites can mediate the interaction strength of predator-prey relationships and affect the topological structure of the Wadden Sea food web as a whole. Finally, we highlight some ongoing changes regarding parasitism in the Wadden Sea in the course of global change (e.g. species introduction, climate change) and identify important future research questions to entangle the role of parasites in the Wadden Sea food web.

Thieltges, David W.; Engelsma, Marc Y.; Wendling, Carolin C.; Wegner, K. Mathias

2013-09-01

41

MOLECULAR CONTROL POINTS IN RHIZOSPHERE FOOD WEBS  

Microsoft Academic Search

Plant roots play diverse roles in the rhizosphere. They function as organs responsible for structural support, for acquisition of mineral and water resources, and for fostering of symbiotic bacteria and fungi. They also sustain a complex food web of pro- karyotes and eukaryotes in, on, and near the root. In addition to these well-known functions, roots have a recently discovered

Donald A. Phillips; Howard Ferris; Douglas R. Cook; Donald R. Strong

2003-01-01

42

PRIMARY RESEARCH PAPER Phytoplankton food quality control of planktonic food web  

E-print Network

variety of approaches devoted to studying this topic, the nature of food web Handling editor: D. HamiltonPRIMARY RESEARCH PAPER Phytoplankton food quality control of planktonic food web processes Marta G to test the effects of phytoplankton food quality for herbivorous zooplankton on planktonic food web

Arhonditsis, George B.

43

Estimating Relative Energy Fluxes Using the Food Web, Species  

E-print Network

Estimating Relative Energy Fluxes Using the Food Web, Species Abundance, and Body Size DANIEL C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 VII. Application: Trophic Level and Tropic Height . . . . . . . . . . . . . . . . . . 163 VIII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 I. SUMMARY Given the food web, mean body sizes, and numerical abundances of species

Cohen, Joel E.

44

DEEPWATER AND NEARSHORE FOOD WEB CHARACTERIZATIONS IN LAKE SUPERIOR  

EPA Science Inventory

Due to the difficulty associated with sampling deep aquatic systems, food web relationships among deepwater fauna are often poorly known. We are characterizing nearshore versus offshore habitats in the Great Lakes and investigating food web linkages among profundal, pelagic, and ...

45

Quantifying Food Web Flows Using Linear Inverse Models  

Microsoft Academic Search

The quantitative mapping of food web flows based on empirical data is a crucial yet difficult task in ecology. The difficulty\\u000a arises from the under-sampling of food webs, because most data sets are incomplete and uncertain. In this article, we review\\u000a methods to quantify food web flows based on empirical data using linear inverse models (LIM). The food web in

Dick van Oevelen; Karel Van den Meersche; Filip J. R. Meysman; Karline Soetaert; Jack J. Middelburg; Alain F. Vézina

2010-01-01

46

Benthos as the basis for arctic lake food webs  

Microsoft Academic Search

Plankton have traditionally been viewed as the basis for limnetic food webs, with zooplankton acting as a gateway for energy passing between phytoplanktonic primary producers and fish. Often, benthic production has been considered to be important primarily in shallow systems or as a subsidy to planktonic food web pathways. Stable isotope food web analyses of two arctic lakes (NE14 and

Michael E. Sierszen; Michael E. McDonald; Douglas A. Jensen

2003-01-01

47

Models of food web evolution Alan J. McKane  

E-print Network

. If there are similarities between food webs in such diverse communities (for instance, marine, desert or lake communitiesModels of food web evolution Alan J. McKane Barbara Drossel While it is often possible to model of possible networks. Here we argue, in the context of food webs, that it is necessary to go beyond simply

McKane, Alan

48

Does cadmium pollution change trophic interactions in rockpool food webs?  

Microsoft Academic Search

The authors studied the regulation of phytoplankton and zooplankton biomass in rockpool food webs under chronic cadmium pollution. Experimental food webs with two and three trophic levels were composed of phytoplankton, small-bodied zooplankton (Chydorus sphaericus, Cyclops sp., and rotifers), Daphnia magna, and Notonecta sp., a zooplanktivorous predator. Every food web received a control and cadmium treatment allowing a separate study

Sanna Koivisto; M. Arner; Nils Kautsky

1997-01-01

49

9 Food Web Structure and the Evolution of Complex Networks  

E-print Network

and the same prey is merged in one trophic species (this is referred to as the aggregation of a food web9 Food Web Structure and the Evolution of Complex Networks Guido Caldarelli1 , Diego Garlaschelli1 propose two other useful quantities that can help in characterizing the topology of food webs

Caldarelli, Guido

50

Food web complexity and higher-level ecosystem services  

E-print Network

. Ecology Letters (2003) 6: 587­593 IN T ROD U CTI ON The looming global biodiversity crisis has spawnedLETTER Food web complexity and higher-level ecosystem services Jose´ M. Montoya1,2 *, Miguel A in natural food webs. Here we present evidence that differences in food web structure and the richness

Rodríguez, Miguel Ángel

51

Staff summary of Issues & Recommendations Predation and Food Webs  

E-print Network

1 Staff summary of Issues & Recommendations Predation and Food Webs *Preliminary draft, please and Food Webs Specific Language Changes NOAA Fisheries recommends the following new language in the Habitat of non-native predators including abundance, diel and temporal distributions, and food web interactions

52

DISTRIBUTION OF PHTHALATE MONOESTERS IN AN AQUATIC FOOD WEB  

E-print Network

DISTRIBUTION OF PHTHALATE MONOESTERS IN AN AQUATIC FOOD WEB by Maggie L. McConnell B: Distribution of Phthalate Monoesters in an Aquatic Food Web Report No.: 426 Examining Committee in organisms of an aquatic food web were investigated. A field study was conducted in False Creek, Vancouver

53

Mycoloop: chytrids in aquatic food webs  

PubMed Central

Parasites are ecologically significant in various ecosystems through their role in shaping food web structure, facilitating energy transfer, and controlling disease. Here in this review, we mainly focus on parasitic chytrids, the dominant parasites in aquatic ecosystems, and explain their roles in aquatic food webs, particularly as prey for zooplankton. Chytrids have a free-living zoosporic stage, during which they actively search for new hosts. Zoospores are excellent food for zooplankton in terms of size, shape, and nutritional quality. In the field, densities of chytrids can be high, ranging from 101 to 109 spores L?1. When large inedible phytoplankton species are infected by chytrids, nutrients within host cells are transferred to zooplankton via the zoospores of parasitic chytrids. This new pathway, the “mycoloop,” may play an important role in shaping aquatic ecosystems, by altering sinking fluxes or determining system stability. The grazing of zoospores by zooplankton may also suppress outbreaks of parasitic chytrids. A food web model demonstrated that the contribution of the mycoloop to zooplankton production increased with nutrient availability and was also dependent on the stability of the system. Further studies with advanced molecular tools are likely to discover greater chytrid diversity and evidence of additional mycoloops in lakes and oceans. PMID:24795703

Kagami, Maiko; Miki, Takeshi; Takimoto, Gaku

2014-01-01

54

Parasites in food webs: the ultimate missing links.  

PubMed

Parasitism is the most common consumer strategy among organisms, yet only recently has there been a call for the inclusion of infectious disease agents in food webs. The value of this effort hinges on whether parasites affect food-web properties. Increasing evidence suggests that parasites have the potential to uniquely alter food-web topology in terms of chain length, connectance and robustness. In addition, parasites might affect food-web stability, interaction strength and energy flow. Food-web structure also affects infectious disease dynamics because parasites depend on the ecological networks in which they live. Empirically, incorporating parasites into food webs is straightforward. We may start with existing food webs and add parasites as nodes, or we may try to build food webs around systems for which we already have a good understanding of infectious processes. In the future, perhaps researchers will add parasites while they construct food webs. Less clear is how food-web theory can accommodate parasites. This is a deep and central problem in theoretical biology and applied mathematics. For instance, is representing parasites with complex life cycles as a single node equivalent to representing other species with ontogenetic niche shifts as a single node? Can parasitism fit into fundamental frameworks such as the niche model? Can we integrate infectious disease models into the emerging field of dynamic food-web modelling? Future progress will benefit from interdisciplinary collaborations between ecologists and infectious disease biologists. PMID:18462196

Lafferty, Kevin D; Allesina, Stefano; Arim, Matias; Briggs, Cherie J; De Leo, Giulio; Dobson, Andrew P; Dunne, Jennifer A; Johnson, Pieter T J; Kuris, Armand M; Marcogliese, David J; Martinez, Neo D; Memmott, Jane; Marquet, Pablo A; McLaughlin, John P; Mordecai, Erin A; Pascual, Mercedes; Poulin, Robert; Thieltges, David W

2008-06-01

55

Understanding food-web persistence from local to global scales  

Microsoft Academic Search

Understanding food-web persistence is an important long-term objective of ecology because of its relevance in maintaining biodiversity. To date, many dynamic studies of food-web behaviour—both empirical and theoretical—have focused on smaller sub- webs, called trophic modules, because these modules are more tractable experimentally and analytically than whole food webs. The question remains to what degree studies of trophic modules are

Daniel B. Stouffer; Jordi Bascompte

2010-01-01

56

Food web model with detritus path  

NASA Astrophysics Data System (ADS)

We present and study a lattice (Monte Carlo) model of a food web consisting of three levels. Agents on the lowest level produce food from dead agents (detritus) of the upper levels and are themselves eaten by the first level species, which in turn are prey for the top level species. Agents which do not find food in a given time, die with a given probability, while eating enables them to produce offspring in their neighborhood. This rule applies to species on all levels, including the lowest one. The dynamics is therefore nutrient limited. We are considering two pathways - grazers and detritus (using dead organic matter). We show that the emerging dynamics is more complex than the ordinary predator-prey systems in which bottom species are indestructible. We investigate the viability of our model and we construct appropriate (extinct-alive) phase diagrams. We demonstrate how the temporal fluctuations in the densities of the three populations are correlated. We show also that the density of the middle level agents plays the key role in the viability of the investigated food web.

Szwabi?ski, Janusz; P?kalski, Andrzej; Bena, Ioana; Droz, Michel

2010-07-01

57

The Antarctic Ecosystem: Where Would It Be Without Krill?  

NSDL National Science Digital Library

This lesson plan asks students to investigate the importance of krill to the Antarctic ecosystem by researching the animals that depend on it. Students will read and answer questions about krill; research Antarctic animals and take note of the place of each animal in the food chain; and draw an Antarctic food web, using the animals they have researched. They will conclude by writing paragraphs explaining the potential consequences of a decline in krill populations.

58

Plankton, antarctic food chain base, respond to increased ultraviolet radiation  

SciTech Connect

With the growth of the austral spring ozone hole phytoplankton in antarctic waters beneath the depleted ozone layer are now being exposed to twice the amount of ultraviolet radiation as organisms outside the hole. This briefly describes the results of a major study examining this issue. A significant observation was a decrease in phytoplankton production by a minimum of 6-12 percent. Implications for other life forms are discussed briefly along with the effects of increased UV light on the whole ecosystem.

Dybas, C.

1992-12-01

59

36 Changes in Phytoplankton Assemblages Along the Antarctic Peninsula and Potential Implications  

E-print Network

263 36 Changes in Phytoplankton Assemblages Along the Antarctic Peninsula and Potential Implications for the Antarctic Food Web MARKA. MOLINEl, HERVE CLAUSTR£2,THOMAS K. FRAZER], JOE GRZYMSK14,OSCAR in the dominant phytoplankton taxa during the austral summerin a coastalregion alongtheAntarctic Peninsula

Moline, Mark

60

An Antarctic starfish (Odontaster validus) climbs over an Antarctic scallop (Adamisium colbecki).  

NSDL National Science Digital Library

An Antarctic starfish (Odontaster validus) climbs over an Antarctic scallop (Adamisium colbecki) in the coastal Ross Sea. Antarctic starfish are omnivores with a wide range of potential prey and an ability to filter feed. Marine food webs often have a high degree of omnivory, with animals tending to feed broadly across available food types, both up and down the food chain. As a result, species such as starfish do not appear to be restricted to fixed trophic positions in marine food webs. In marine ecosystems in Antarctica, sea ice conditions influence food web dynamics by affecting the primary food sources that are available. This photograph originally appeared on the cover of Ecology (88:11) in November of 2007.

Budd, Rod

2010-02-12

61

The Disruption of Coastal Food Webs  

NSDL National Science Digital Library

This week's In The News addresses recent findings (published in the October 16, 1998 issue of Science) that killer whale predation on sea otters in the North Pacific has "created an ecological chain reaction in nearshore ecosystems." Such ecological chain reactions refer to the disruption of the complex balance between predator and prey species. Killer whales, which traditionally fed on the (now scarce) Steller sea lions and harbor seals, have recently shifted their diet to sea otters. The resulting decline in sea otters has, in turn, led to an increase in sea urchins (sea otter prey), which in turn have deforested many kelp (seaweed) beds in the nearshore marine community. Although killer whales are playing a critical role in the current disruption, this chain of interactions "was probably initiated by anthropogenic changes in the offshore oceanic ecosystem" -- namely, the region's burgeoning fisheries, higher ocean temperatures, and the depletion of baleen whales. Similar "trophic cascades" have been well documented for lakes and in other systems (e.g. Snow Geese in the Arctic), but this research provides a new example of a disrupted food web that may reach a wider audience -- as it involves several highly charismatic vertebrates. The nine resources discussed describe the recent scientific findings, provide background information on food webs, and offer several resources for understanding ecological (trophic) chain reactions.

Payne, Laura X.

1998-01-01

62

Geo-Spatial Browse and Distribution of NSF-OPP's Antarctic Ice and Climate Data via the Web: Antarctic Cryosphere Access Portal (A-CAP)  

NASA Astrophysics Data System (ADS)

A prototype of the Antarctic Cryosphere Access Portal (A-CAP) has been released for public use. Developed at the National Snow and Ice Data Center (NSIDC) Antarctic Glaciological Data Center (AGDC), A-CAP aims to be a geo-visualization and data download tool for AGDC data and other Antarctic-wide parameters, including glaciology, ice core data, snow accumulation, satellite imagery, digital elevation models (DEMs), sea ice concentration, and many other cryosphere-related scientific measurements. The user can zoom in to a specific region as well as overlay coastlines, placenames, latitude/longitude, and other geographic information. In addition to providing an interactive Web interface, customizable A-CAP map images and source data are also accessible via specific Uniform Resource Locator strings (URLs) to a standard suite of Open Geospatial Consortium (OGC) services: Web Map Service (WMS), Web Feature Service (WFS), and Web Coverage Service (WCS). The international specifications of these services provide an interoperable framework for sharing maps and geospatial data over the Internet, allowing A-CAP products to be easily exchanged with other data centers worldwide and enabling remote access for users through OGC-compliant software applications such as ArcGIS, Google Earth, ENVI, and many others. A-CAP is built on MapServer, an Open Source development environment for building spatially-enabled Internet applications. MapServer uses data sets that have been formatted as GeoTIFF or Shapefile to allow rapid sub-setting and over-the-Web presentation of large geospatial data files, and has no requirement for a user-installed client software package (besides a Web browser).

Bauer, R.; Scambos, T.; Haran, T.; Maurer, J.; Bohlander, J.

2008-12-01

63

Consequences of symbiosis for food web dynamics.  

PubMed

Basic Lotka-Volterra type models in which mutualism (a type of symbiosis where the two populations benefit both) is taken into account, may give unbounded solutions. We exclude such behaviour using explicit mass balances and study the consequences of symbiosis for the long-term dynamic behaviour of a three species system, two prey and one predator species in the chemostat. We compose a theoretical food web where a predator feeds on two prey species that have a symbiotic relationships. In addition to a species-specific resource, the two prey populations consume the products of the partner population as well. In turn, a common predator forages on these prey populations. The temporal change in the biomass and the nutrient densities in the reactor is described by ordinary differential equations (ODE). Since products are recycled, the dynamics of these abiotic materials must be taken into account as well, and they are described by odes in a similar way as the abiotic nutrients. We use numerical bifurcation analysis to assess the long-term dynamic behaviour for varying degrees of symbiosis. Attractors can be equilibria, limit cycles and chaotic attractors depending on the control parameters of the chemostat reactor. These control parameters that can be experimentally manipulated are the nutrient density of the inflow medium and the dilution rate. Bifurcation diagrams for the three species web with a facultative symbiotic association between the two prey populations, are similar to that of a bi-trophic food chain; nutrient enrichment leads to oscillatory behaviour. Predation combined with obligatory symbiotic prey-interactions has a stabilizing effect, that is, there is stable coexistence in a larger part of the parameter space than for a bi-trophic food chain. However, combined with a large growth rate of the predator, the food web can persist only in a relatively small region of the parameter space. Then, two zero-pair bifurcation points are the organizing centers. In each of these points, in addition to a tangent, transcritical and Hopf bifurcation a global heteroclinic bifurcation is emanating. This heteroclinic cycle connects two saddle equilibria where the predator is absent. Under parameter variation the period of the stable limit cycle goes to infinity and the cycle tends to the heteroclinic cycle. At this global bifurcation point this cycle breaks and the boundary of the basin of attraction disappears abruptly because the separatrix disappears together with the cycle. As a result, it becomes possible that a stable two-nutrient-two-prey population system becomes unstable by invasion of a predator and eventually the predator goes extinct together with the two prey populations, that is, the complete food web is destroyed. This is a form of over-exploitation by the predator population of the two symbiotic prey populations. When obligatory symbiotic prey-interactions are modelled with Liebig's minimum law, where growth is limited by the most limiting resource, more complicated types of bifurcations are found. This results from the fact that the Jacobian matrix changes discontinuously with respect to a varying parameter when another resource becomes most limiting. PMID:15293013

Kooi, B W; Kuijper, L D J; Kooijman, S A L M

2004-09-01

64

Mercury bioaccumulation in estuarine food webs.  

PubMed

We tested for unintended mercury contamination problems associated with estuarine floodplain restoration projects of the Louisiana coastal zone, USA. Barataria Bay and Breton Sound are two neighboring deltaic estuaries that were isolated by levees from the Mississippi River about 100 years ago. These estuaries recently have been reconnected to the nutrient-rich Mississippi River, starting major river diversion (input) flows in 1991 for Breton Sound and in 2004 for Barataria Bay. We collected > 2100 fish over five years from 20 stations in these estuaries to test two hypotheses about Hg bioaccumulation: (H1) Background Hg bioaccumulation in fish would be highest in low-salinity upper reaches of estuaries, and (H2) recent river inputs to these upper estuarine areas would increase Hg bioaccumulation in fish food webs. For H1, we surveyed fish Hg concentrations at several stations along a salinity gradient in Barataria Bay in 2003-2004, a time when this estuary lacked strong river inputs. Results showed that average Hg concentrations in fish communities were lowest (150 ng/g dry mass) in higher salinity areas and -2.4x higher (350 ng/g) in low-salinity oligohaline and freshwater upper reaches of the estuary. For H2, we tested for enhanced Hg bioaccumulation following diversion onset in both estuaries. Fish communities from Breton Sound that had long-term (> 10 years) diversion inputs had -1.7x higher average Hg contents of 610 ng/g Hg vs. 350 ng/g background values. Shorter-term diversion inputs over 2-3 years in upper Barataria Bay did not result in strong Hg enrichments or stable C isotope increases seen in Breton Sound, even though N and S stable-isotope values indicated strong river inputs in both estuaries. It may be that epiphyte communities on abundant submerged aquatic vegetation (SAV) are important hotspots for Hg cycling in these estuaries, and observed lesser development of these epiphyte communities in upper Barataria Bay during the first years of diversion inputs may account for the lessened Hg bioaccumulation in fish. A management consideration from this study is that river restoration projects may unintentionally fertilize SAV and epiphyte-based food webs, leading to higher Hg bioaccumulation in river-impacted floodplains and their food webs. PMID:22611858

Fry, Brian; Chumchal, Matthew M

2012-03-01

65

Dynamics of the Lake Michigan food web, 1970?2000  

Microsoft Academic Search

Herein, we document changes in the Lake Michigan food web between 1970 and 2000 and identify the fac- tors responsible for these changes. Control of sea lamprey (Petromyzon marinus) and alewife (Alosa pseudoharengus) populations in Lake Michigan, beginning in the 1950s and 1960s, had profound effects on the food web. Recoveries of lake whitefish (Coregonus clupeaformis) and burbot (Lota lota)

Charles P. Madenjian; Gary L. Fahnenstiel; Thomas H. Johengen; Thomas F. Nalepa; Henry A. Vanderploeg; Guy W. Fleischer; Philip J. Schneeberger; Darren M. Benjamin; Emily B. Smith; James R. Bence; Edward S. Rutherford; Dennis S. Lavis; Dale M. Robertson; David J. Jude; Mark P. Ebener

2002-01-01

66

Two Degrees of Separation in Complex Food Webs  

Microsoft Academic Search

Feeding relationships can cause invasions, extirpations, and population fluctuations of a species to dramatically affect other species within a variety of natural habitats. Such strong effects rarely propagate through food webs more than three links away from the initial perturbation. However, in large food webs the number of species within these spheres of potential influence are generally unknown. Here we

Richard J. Williams; Neo D. Martinez; Eric L. Berlow; Jennifer A. Dunne; Albert-Laszlo Barabasi

2001-01-01

67

Dietary switching of collembola in grassland soil food webs  

Microsoft Academic Search

Soil food webs are characterised by complex direct and indirect effects among the organisms. Consumption of microorganisms by soil animals is considered as an important factor that contributes to the stability of communities, though cascading effects within the food web can be difficult to detect. In a greenhouse experiment, an addition of a high number the fungal feeding collembola Folsomia

Natalia Ladygina; Tancredi Caruso; Katarina Hedlund

2008-01-01

68

Host Centrality in Food Web Networks Determines Parasite Diversity  

PubMed Central

Background Parasites significantly alter topological metrics describing food web structure, yet few studies have explored the relationship between food web topology and parasite diversity. Methods/Principal Findings This study uses quantitative metrics describing network structure to investigate the relationship between the topology of the host food web and parasite diversity. Food webs were constructed for four restored brackish marshes that vary in species diversity, time post restoration and levels of parasitism. Our results show that the topology of the food web in each brackish marsh is highly nested, with clusters of generalists forming a distinct modular structure. The most consistent predictors of parasite diversity within a host were: trophic generality, and eigenvector centrality. These metrics indicate that parasites preferentially colonise host species that are highly connected, and within modules of tightly interacting species in the food web network. Conclusions/Significance These results suggest that highly connected free-living species within the food web may represent stable trophic relationships that allow for the persistence of complex parasite life cycles. Our data demonstrate that the structure of host food webs can have a significant effect on the establishment of parasites, and on the potential for evolution of complex parasite life cycles. PMID:22046360

Anderson, Tavis K.; Sukhdeo, Michael V. K.

2011-01-01

69

Food web structure and the evolution of ecological communities  

E-print Network

Food web structure and the evolution of ecological communities Christopher Quince1 , Paul G. Higgs2 the population dynamics of the species for any structure of the food web. The equations account for competition, the `child' species usually adds to the same trophic level as the parent. The chance of the child species

McKane, Alan

70

Food Web Stability: The Influence of Trophic Flows across Habitats  

Microsoft Academic Search

In nature, fluxes across habitats often bring both nu- ory, which plays a central role in consumer-resource in- trient and energetic resources into areas of low productivity from areas of higher productivity. These inputs can alter consumption teractions and food web dynamics. They further rates of consumer and predator species in the recipient food webs, suggested that multichannel omnivory can

Kevin McCann

1998-01-01

71

Ecological food web analysis for chemical risk assessment  

Microsoft Academic Search

Food web analysis can be a critical component of ecological risk assessment, yet it has received relatively little attention among risk assessors. Food web data are currently used in modeling bioaccumulation of toxic chemicals and, to a limited extent, in the determination of the ecological significance of risks. Achieving more realism in ecological risk assessments requires new analysis tools and

Damian V. Preziosi; Robert A. Pastorok

2008-01-01

72

Environmental controls on food web regimes: A fluvial perspective  

Microsoft Academic Search

Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes

Mary E. Power

2006-01-01

73

Investigation a food web: producers, consumers, and decomposers  

NSDL National Science Digital Library

This activity is a field investigation where students list plants and animals they observe. Students will organize their data as producers, consumers, or decomposers and create a food web showing how they affect each other. They will predict what will happen if the food web becomes imbalanced by extinction or over population.

74

A "Bottom-Up" Approach to Food Web Construction  

ERIC Educational Resources Information Center

The ability to comprehend trophic (nutritional) relationships and food web dynamics is an essential part of environmental literacy. However, students face severe difficulties in grasping the variety of causal patterns in food webs. We propose a curriculum for comprehending trophic relations in elementary school. The curriculum allows students to…

Demetriou, Dorita; Korfiatis, Konstantinos; Constantinou, Constantinos

2009-01-01

75

TOWARD AN INTEGRATION OF LANDSCAPE AND FOOD WEB ECOLOGY:The Dynamics of Spatially Subsidized Food Webs  

Microsoft Academic Search

We focus on the implications of movement, landscape variables, and spatial het- erogeneity for food web dynamics. Movements of nutrients, detritus, prey, and consumers among habitats are ubiquitous in diverse biomes and can strongly influence population, consumer-resource, food web, and community dynamics. Nutrient and detrital subsidies usually increase primary and secondary produc- tivity, both directly and indirectly. Prey subsidies, by

Gary A. Polis; Wendy B. Anderson; Robert D. Holt

1997-01-01

76

Food marketing on popular children's web sites: a content analysis.  

PubMed

In 2006 the Institute of Medicine (IOM) concluded that food marketing was a contributor to childhood obesity in the United States. One recommendation of the IOM committee was for research on newer marketing venues, such as Internet Web sites. The purpose of this cross-sectional study was to answer the IOM's call by examining food marketing on popular children's Web sites. Ten Web sites were selected based on market research conducted by KidSay, which identified favorite sites of children aged 8 to 11 years during February 2005. Using a standardized coding form, these sites were examined page by page for the existence, type, and features of food marketing. Web sites were compared using chi2 analyses. Although food marketing was not pervasive on the majority of the sites, seven of the 10 Web sites contained food marketing. The products marketed were primarily candy, cereal, quick serve restaurants, and snacks. Candystand.com, a food product site, contained a significantly greater amount of food marketing than the other popular children's Web sites. Because the foods marketed to children are not consistent with a healthful diet, nutrition professionals should consider joining advocacy groups to pressure industry to reduce online food marketing directed at youth. PMID:18375231

Alvy, Lisa M; Calvert, Sandra L

2008-04-01

77

Amphipod-supported food web: Themisto gaudichaudii, a key food resource for fishes in the southern Patagonian Shelf  

NASA Astrophysics Data System (ADS)

The trophic role of the hyperiid amphipod Themisto gaudichaudii in the southern Patagonian shelf food web was assessed from the analysis of stomach contents of the local fish assemblage. A total of 461 trawl samples were collected during seven seasonal cruises. A total of 17 out of 38 fish species were found to ingest T. gaudichaudii. This amphipod was a main prey item in five of these species, showing high values of alimentary index: Seriolella porosa (99.9%), Macruronus magellanicus (68.8%), Micromesistius australis (59.1%), Patagonotothen ramsayi (48.6%), and Merluccius hubbsi (10.9%). The contribution of T. gaudichaudii, in weight, to their summer diet was 60%, on average. This contribution was minimal in winter and maximal in summer. Fisheries studies have indicated that these five species, mainly M. magellanicus, account for almost 85% of the fish biomass in the area. Although the remaining 15% did not feed heavily on T. gaudichaudii, they are known to prey on the main hyperiid predators. Our study shows that T. gaudichaudii contributes greatly, both directly and indirectly, to supporting the fish community. We thus proposed that T. gaudichaudii plays a key role as a "wasp-waist" species in the sub-Antarctic region, similar to that of krill in Antarctic waters, channeling the energy flow and enabling a short and efficient food chain.

Padovani, Luciano N.; Viñas, María Delia; Sánchez, Felisa; Mianzan, Hermes

2012-01-01

78

Isotopic Diversity Indices: How Sensitive to Food Web Structure?  

PubMed Central

Recently revisited, the concept of niche ecology has lead to the formalisation of functional and trophic niches using stable isotope ratios. Isotopic diversity indices (IDI) derived from a set of measures assessing the dispersion/distribution of points in the ?-space were recently suggested and increasingly used in the literature. However, three main critics emerge from the use of these IDI: 1) they fail to account for the isotopic sources overlap, 2) some indices are highly sensitive to the number of species and/or the presence of rare species, and 3) the lack of standardization prevents any spatial and temporal comparisons. Using simulations we investigated the ability of six commonly used IDI to discriminate among different trophic food web structures, with a focus on the first two critics. We tested the sensitivity of the IDI to five food web structures along a gradient of sources overlap, varying from two distinct food chains with differentiated sources to two superimposed food chains sharing two sources. For each of the food web structure we varied the number of species (from 10 to 100 species) and the type of species feeding behaviour (i.e. random or selective feeding). Values of IDI were generally larger in food webs with distinct basal sources and tended to decrease as the superimposition of the food chains increased. This was more pronounced when species displayed food preferences in comparison to food webs where species fed randomly on any prey. The number of species composing the food web also had strong effects on the metrics, including those that were supposedly less sensitive to small sample size. In all cases, computing IDI on food webs with low numbers of species always increases the uncertainty of the metrics. A threshold of ?20 species was detected above which several metrics can be safely used. PMID:24391910

Brind'Amour, Anik; Dubois, Stanislas F.

2013-01-01

79

Food web complexity and stability across habitat connectivity gradients.  

PubMed

The effects of habitat connectivity on food webs have been studied both empirically and theoretically, yet the question of whether empirical results support theoretical predictions for any food web metric other than species richness has received little attention. Our synthesis brings together theory and empirical evidence for how habitat connectivity affects both food web stability and complexity. Food web stability is often predicted to be greatest at intermediate levels of connectivity, representing a compromise between the stabilizing effects of dispersal via rescue effects and prey switching, and the destabilizing effects of dispersal via regional synchronization of population dynamics. Empirical studies of food web stability generally support both this pattern and underlying mechanisms. Food chain length has been predicted to have both increasing and unimodal relationships with connectivity as a result of predators being constrained by the patch occupancy of their prey. Although both patterns have been documented empirically, the underlying mechanisms may differ from those predicted by models. In terms of other measures of food web complexity, habitat connectivity has been empirically found to generally increase link density but either reduce or have no effect on connectance, whereas a unimodal relationship is expected. In general, there is growing concordance between empirical patterns and theoretical predictions for some effects of habitat connectivity on food webs, but many predictions remain to be tested over a full connectivity gradient, and empirical metrics of complexity are rarely modeled. Closing these gaps will allow a deeper understanding of how natural and anthropogenic changes in connectivity can affect real food webs. PMID:25227679

LeCraw, Robin M; Kratina, Pavel; Srivastava, Diane S

2014-12-01

80

Compilation and Network Analyses of Cambrian Food Webs  

PubMed Central

A rich body of empirically grounded theory has developed about food webs—the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple “niche model,” which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid diversification of species, body plans, and trophic roles during the Cambrian radiation. More research is needed to explore the generality of food-web structure through deep time and across habitats, especially to investigate potential mechanisms that could give rise to similar structure, as well as any differences. PMID:18447582

Dunne, Jennifer A; Williams, Richard J; Martinez, Neo D; Wood, Rachel A; Erwin, Douglas H

2008-01-01

81

Compilation and network analyses of cambrian food webs.  

PubMed

A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple "niche model," which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid diversification of species, body plans, and trophic roles during the Cambrian radiation. More research is needed to explore the generality of food-web structure through deep time and across habitats, especially to investigate potential mechanisms that could give rise to similar structure, as well as any differences. PMID:18447582

Dunne, Jennifer A; Williams, Richard J; Martinez, Neo D; Wood, Rachel A; Erwin, Douglas H

2008-04-29

82

Food webs: reconciling the structure and function of biodiversity.  

PubMed

The global biodiversity crisis concerns not only unprecedented loss of species within communities, but also related consequences for ecosystem function. Community ecology focuses on patterns of species richness and community composition, whereas ecosystem ecology focuses on fluxes of energy and materials. Food webs provide a quantitative framework to combine these approaches and unify the study of biodiversity and ecosystem function. We summarise the progression of food-web ecology and the challenges in using the food-web approach. We identify five areas of research where these advances can continue, and be applied to global challenges. Finally, we describe what data are needed in the next generation of food-web studies to reconcile the structure and function of biodiversity. PMID:22959162

Thompson, Ross M; Brose, Ulrich; Dunne, Jennifer A; Hall, Robert O; Hladyz, Sally; Kitching, Roger L; Martinez, Neo D; Rantala, Heidi; Romanuk, Tamara N; Stouffer, Daniel B; Tylianakis, Jason M

2012-12-01

83

Consumers indirectly increase infection risk in grassland food webs  

E-print Network

Consumers indirectly increase infection risk in grassland food webs Elizabeth T. Borera,1 , Charles by increasing the relative abundance of highly-competent hosts in the grassland community. This large

Crews, Stephen

84

Tracking contaminant flux from aquatic to terrestrial food webs  

EPA Science Inventory

Aquatic insects provide a critical energy subsidy to riparian food webs, yet their role as vectors of contaminants to terrestrial ecosystems is poorly understood. We investigated aquatic resource utilization and contaminant exposure among riparian invertivores (spiders and herpt...

85

The structure of food webs along river networks  

Microsoft Academic Search

Do changes in the species composition of riverine fish assemblages along river networks lead to predictable changes in food-web structure? We assembled empirical ''fish-centered'' river food webs for three rivers located along a latitudinal gradient in the South Saskatchewan River Basin (SSRB) that differ in land-use impacts and geomorphology but flow through similar mountain, foothill, and prairie physiographic regions. We

Tamara N. Romanuk; Leland J. Jackson; John R. Post; Ed McCauley; Neo D. Martinez

2006-01-01

86

Soil food web structure during ecosystem development after land abandonment  

Microsoft Academic Search

The re-establishment of natural species rich heathlands on abandoned agricultural land is a common land use change in North-West Europe. However, it can take several decades to re-establish natural species rich heathland vegetation. The development rate has found to depend both on soil food web composition and on soil processes.We measured the soil food web composition in three ex-arable fields

Remko Holtkamp; Paul Kardol; Annemieke van der Wal; Stefan C. Dekker; Wim H. van der Putten; Peter C. de Ruiter

2008-01-01

87

A patch-dynamic framework for food web metacommunities  

Microsoft Academic Search

The metacommunity concept has proved to be a valuable tool for studying how space can affect the properties and assembly of\\u000a competitive communities. However, the concept has not been as extensively applied to the study of food webs or trophically\\u000a structured communities. Here, we demonstrate how to develop a modelling framework that permits food webs to be considered\\u000a from a

Pradeep Pillai; Michel Loreau; Andrew Gonzalez

2010-01-01

88

Spatial Scales of Carbon Flow in a River Food Web  

Microsoft Academic Search

Spatial extents of food webs that support stream and river consumers are largely unknown, but such information is essential for basic understanding and management of lotic ecosystems. We used predictable variation in algal d13C with water velocity, and measurements of consumer d13C and d15N to examine carbon flow and trophic structure in food webs of the South Fork Eel River

Jacques C. Finlay; Sapna Khandwala; Mary E. Power

2002-01-01

89

Phylogeny versus body size as determinants of food web structure  

PubMed Central

Food webs are the complex networks of trophic interactions that stoke the metabolic fires of life. To understand what structures these interactions in natural communities, ecologists have developed simple models to capture their main architectural features. However, apparently realistic food webs can be generated by models invoking either predator–prey body-size hierarchies or evolutionary constraints as structuring mechanisms. As a result, this approach has not conclusively revealed which factors are the most important. Here we cut to the heart of this debate by directly comparing the influence of phylogeny and body size on food web architecture. Using data from 13 food webs compiled by direct observation, we confirm the importance of both factors. Nevertheless, phylogeny dominates in most networks. Moreover, path analysis reveals that the size-independent direct effect of phylogeny on trophic structure typically outweighs the indirect effect that could be captured by considering body size alone. Furthermore, the phylogenetic signal is asymmetric: closely related species overlap in their set of consumers far more than in their set of resources. This is at odds with several food web models, which take only the view-point of consumers when assigning interactions. The echo of evolutionary history clearly resonates through current food webs, with implications for our theoretical models and conservation priorities. PMID:22628467

Naisbit, Russell E.; Rohr, Rudolf P.; Rossberg, Axel G.; Kehrli, Patrik; Bersier, Louis-Felix

2012-01-01

90

Soil food web changes during spontaneous succession at post mining sites: a possible ecosystem engineering effect on food web organization?  

PubMed

Parameters characterizing the structure of the decomposer food web, biomass of the soil microflora (bacteria and fungi) and soil micro-, meso- and macrofauna were studied at 14 non-reclaimed 1- 41-year-old post-mining sites near the town of Sokolov (Czech Republic). These observations on the decomposer food webs were compared with knowledge of vegetation and soil microstructure development from previous studies. The amount of carbon entering the food web increased with succession age in a similar way as the total amount of C in food web biomass and the number of functional groups in the food web. Connectance did not show any significant changes with succession age, however. In early stages of the succession, the bacterial channel dominated the food web. Later on, in shrub-dominated stands, the fungal channel took over. Even later, in the forest stage, the bacterial channel prevailed again. The best predictor of fungal bacterial ratio is thickness of fermentation layer. We argue that these changes correspond with changes in topsoil microstructure driven by a combination of plant organic matter input and engineering effects of earthworms. In early stages, soil is alkaline, and a discontinuous litter layer on the soil surface promotes bacterial biomass growth, so the bacterial food web channel can dominate. Litter accumulation on the soil surface supports the development of the fungal channel. In older stages, earthworms arrive, mix litter into the mineral soil and form an organo-mineral topsoil, which is beneficial for bacteria and enhances the bacterial food web channel. PMID:24260281

Frouz, Jan; Thébault, Elisa; Pižl, Václav; Adl, Sina; Cajthaml, Tomáš; Baldrián, Petr; Hán?l, Ladislav; Starý, Josef; Tajovský, Karel; Materna, Jan; Nováková, Alena; de Ruiter, Peter C

2013-01-01

91

Stable Isotope Tracers of Process in Great Lakes Food Webs  

EPA Science Inventory

Stable isotope analyses of biota are now commonly used to discern trophic pathways between consumers and their foods. However, those same isotope data also hold information about processes that influence the physicochemical setting of food webs as well as biological processes ope...

92

Environmental controls on food web regimes: A fluvial perspective  

NASA Astrophysics Data System (ADS)

Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of functional relationships that link environments, fluxes and food web interactions to understand how they will respond to intensifying anthropogenic forcing over the coming decades.

Power, Mary E.

2006-02-01

93

FoodFit: A Web Application to Illustrate Healthier Food and Physical Activity Choices  

E-print Network

FoodFit: A Web Application to Illustrate Healthier Food and Physical Activity Choices Meriyan Eren their lifestyles to include healthier food choices and more frequent physical activities. Lack of motivation your diet with physical activities - Familiar nutrition facts label, colorful bar plots and face

Toronto, University of

94

Key Features of Intertidal Food Webs That Support Migratory Shorebirds  

PubMed Central

The migratory shorebirds of the East Atlantic flyway land in huge numbers during a migratory stopover or wintering on the French Atlantic coast. The Brouage bare mudflat (Marennes-Oléron Bay, NE Atlantic) is one of the major stopover sites in France. The particular structure and function of a food web affects the efficiency of carbon transfer. The structure and functioning of the Brouage food web is crucial for the conservation of species landing within this area because it provides sufficient food, which allows shorebirds to reach the north of Europe where they nest. The aim of this study was to describe and understand which food web characteristics support nutritional needs of birds. Two food-web models were constructed, based on in situ measurements that were made in February 2008 (the presence of birds) and July 2008 (absence of birds). To complete the models, allometric relationships and additional data from the literature were used. The missing flow values of the food web models were estimated by Monte Carlo Markov Chain – Linear Inverse Modelling. The flow solutions obtained were used to calculate the ecological network analysis indices, which estimate the emergent properties of the functioning of a food-web. The total activities of the Brouage ecosystem in February and July are significantly different. The specialisation of the trophic links within the ecosystem does not appear to differ between the two models. In spite of a large export of carbon from the primary producer and detritus in winter, the higher recycling leads to a similar retention of carbon for the two seasons. It can be concluded that in February, the higher activity of the ecosystem coupled with a higher cycling and a mean internal organization, ensure the sufficient feeding of the migratory shorebirds. PMID:24204666

Saint-Béat, Blanche; Dupuy, Christine; Bocher, Pierrick; Chalumeau, Julien; De Crignis, Margot; Fontaine, Camille; Guizien, Katell; Lavaud, Johann; Lefebvre, Sébastien; Montanié, Hélène; Mouget, Jean-Luc; Orvain, Francis; Pascal, Pierre-Yves; Quaintenne, Gwenaël; Radenac, Gilles; Richard, Pierre; Robin, Frédéric; Vézina, Alain F.; Niquil, Nathalie

2013-01-01

95

Stability in Real Food Webs: Weak Links in Long Loops  

NASA Astrophysics Data System (ADS)

Increasing evidence that the strengths of interactions among populations in biological communities form patterns that are crucial for system stability requires clarification of the precise form of these patterns, how they come about, and why they influence stability. We show that in real food webs, interaction strengths are organized in trophic loops in such a way that long loops contain relatively many weak links. We show and explain mathematically that this patterning enhances stability, because it reduces maximum ``loop weight'' and thus reduces the amount of intraspecific interaction needed for matrix stability. The patterns are brought about by biomass pyramids, a feature common to most ecosystems. Incorporation of biomass pyramids in 104 food-web descriptions reveals that the low weight of the long loops stabilizes complex food webs. Loop-weight analysis could be a useful tool for exploring the structure and organization of complex communities.

Neutel, Anje-Margriet; Heesterbeek, Johan A. P.; de Ruiter, Peter C.

2002-05-01

96

8 Food Webs in the Ocean: Who Eats Whom and How Much?  

Microsoft Academic Search

Over 100 food webs have been published for marine ecosystems to describe the transfer of food energy from its source in plants, through herbivores, to carnivores and higher order predators. The webs suggest that the lengths of the chains that form food webs are typically short (3-4 links), and that ecosystems with long food chains may be less stable than

Andrew W. Trites

97

The relationship between the duration of food web evolution and the vulnerability to biological invasion  

Microsoft Academic Search

I conducted computer simulations of food web evolution and investigated the relationship between the duration of food web evolution and the vulnerability to biological invasion. Model food webs without evolution consisted of animal species with a limited number of prey species and producer species with small intrinsic growth rates. Because these species were not resistant to predation pressure, model food

Katsuhiko Yoshida

2008-01-01

98

Ecological tracers can quantify food web structure and change.  

PubMed

Disruption of natural food webs is becoming a commonplace occurrence as a result of human activities. Considering this, there is a need to improve our ability to define food web structure as well as to detect and understand the implications of trophodynamic change. This requires the development, validation, and application of ecologicaltracers that can provide insights into the movement of energy, nutrients, and contaminants through food webs. In this study, we examine the utility of two groups of naturally occurring intrinsic tracers (stable nitrogen isotopes and fatty acids) to provide such information in a predatory seabird, the herring gull (Larus argentatus). Spatial and temporal patterns in gull trophic position (inferred from egg stable nitrogen isotope values) were related to gull diet composition (inferred from egg fatty acid concentrations). These two independent groups of ecological tracers provided corroborating evidence that gull trophic position was related to the degree to which aquatic foods, namely fish, were consumed. The use of these tracers in concert led to a better understanding of routes of energy flow and contaminant transfer in food webs and how these pathways may be affected by ecosystem change. PMID:17007117

Hebert, Craig E; Arts, Michael T; Weseloh, D V Chip

2006-09-15

99

UNSTRUCTURED MARINE FOOD WEBS AND "POLLUTANT ANALOGUES"  

E-print Network

of cesium (and cesium in respect to potassium) than the same species of fish living in the Salton Sea. The Salton Sea fish display simple trophic steps of concentration, whereas those in the Gulf all show about envi- ronments. The concentration factor found in the known and describable food chain of the Salton

100

Aquatic Food Web Interactions: Microcosms as Lake Models  

NSDL National Science Digital Library

As a laboratory exercise for increasing knowledge of trophic cascades in aquatic ecosystems has led to a better understanding of several basic ecological tenets, including competition, predation, and a variety of other community-level food web interactions using microcosms from whole water plankton collections. This lab exercise incorporates student use of rigorous quantitative skills in enumeration, data collection, and statistical inference.

John C. Holz (University of Nebraska;); Kyle D. Hoagland (University of Nebraska;); Anthony Joern (University of Nebraska;)

2000-01-01

101

The trophodynamics of PCBs in the Lake Ontario food web  

SciTech Connect

Samples of water, sediment, invertebrates, fish, and herring gull eggs were collected in north-central Lake Ontario and were analyzed to determine the concentrations of PCBs, including non-ortho substituted PCB congeners, in the benthic and pelagic components of the Lake Ontario food web. There was biomagnification of PCBs in the food web from benthic and planktonic invertebrates through to lake trout and gulls. However, all of the fish species had about the same lipid-normalized concentrations of PCBs. The relative proportions of the PCB congeners changed as they passed through the food web. An index of metabolism for each PCB congener was calculated by comparing the concentrations of PCB congeners in various predator/prey groupings within the food web. These data indicate that invertebrates, fish and gulls have different capabilities in metabolizing and eliminating specific PCB congeners. While tri and tetrachlorinated congeners with no chlorine substitution at meta-para carbons on the biphenyl ring were readily metabolized by all taxa, only gulls appeared to be capable of metabolizing the PCBs with no chlorine substitution at ortho-meta positions. The trophodynamics of nonortho substituted (coplanar) PCBs did not differ from other PCB congeners of similar chlorine number, which indicates that non-ortho congeners are not any more persistent in biota than other PCBs.

Metcalfe, T.L.; Metcalfe, C.D. [Trent Univ., Peterborough, Ontario (Canada). Environmental and Resource Studies Program

1995-12-31

102

Model of carbon cycling in planktonic food webs  

Microsoft Academic Search

A mathematical model of carbon fluxes through the heterotrophic microbial food web is developed from a synthesis of laboratory and field research. The basis of the model is the segregation of organic carbon into lability classes that are defined by bioassay experiments. Bacteria, phytoplankton, three trophic levels of zooplankton, and dissolved organic carbon (DOC) and particulate organic carbon (POC) are

John P. Connolly; Richard B. Coffin

1995-01-01

103

CONTROLS ON FOOD WEBS IN GRAVEL-BEDDED RIVERS: THE  

E-print Network

", that dynamically link predators, primary consumers (herbivores and detritivores), and primary producers, marine, or lentic) habitats. Food web models provide one conceptual framework for organizing our efforts with even numbers, with grazers as top consumers, or with grazers protected by predators of predators

Power, Mary Eleanor

104

Adaptations in a hierarchical food web of southeastern Lake Michigan  

Microsoft Academic Search

Two issues in ecological network theory are: (1) how to construct an ecological network model and (2) how do entire networks (as opposed to individual species) adapt to changing conditions? We present a novel method for constructing an ecological network model for the food web of southeastern Lake Michigan (USA) and we identify changes in key system properties that are

Ann E. Krause; Ken A. Frank; Michael L. Jones; Thomas F. Nalepa; Richard P. Barbiero; Charles P. Madenjian; Megan Agy; Marlene S. Evans; William W. Taylor; Doran M. Mason; Nancy J. Leonard

2009-01-01

105

RAPID COMMUNICATION / COMMUNICATION RAPIDE Simplified food webs lead to energetic  

E-print Network

diet and community analysis indicated that the food web leading to yellow perch (Perca flavescens modelling, we show how this has severe consequences on the efficiency of energy transfer to perch from types are not available to growing perch. These observations provide a much needed ecological

Hontela, Alice

106

Abiotic controls on the functional structure of soil food webs  

Microsoft Academic Search

The hypothesis that the trophic structure of soil food webs changes as a result of the abiotic environment was examined by reviewing studies of soil biota. In dry soils with a water potential below -1.5 MPa, most bacteria, protozoans, and many species of nematodes are not active. These taxa persist in the soil in a state of anhydrobiosis. Because soil

Walter G. Whitford

1989-01-01

107

Barcoding a Quantified Food Web: Crypsis, Concepts, Ecology and Hypotheses  

Microsoft Academic Search

The efficient and effective monitoring of individuals and populations is critically dependent on correct species identification. While this point may seem obvious, identifying the majority of the more than 100 natural enemies involved in the spruce budworm (Choristoneura fumiferana – SBW) food web remains a non-trivial endeavor. Insect parasitoids play a major role in the processes governing the population dynamics

M. Alex Smith; Eldon S. Eveleigh; Kevin S. McCann; Mark T. Merilo; Peter C. McCarthy; Kathleen I. Van Rooyen

2011-01-01

108

BENTHOS AS THE BASIS FOR ARCTIC FOOD WEBS  

EPA Science Inventory

Plankton have traditionally been viewed as the basis for limnetic food webs, with zooplankton acting as a gateway for energy passing between phytoplanktonic primary producers and fish. Often, benthic production is considered to be important primarily in shallow systems or as a su...

109

Perfluoroalkyl Contaminants in an Arctic Marine Food Web: Trophic  

E-print Network

Perfluoroalkyl Contaminants in an Arctic Marine Food Web: Trophic Magnification and Wildlife significantly (P magnification factors (TMFs) of organochlorines ranged ),exceedstheoralreferencedoseforPFOS (7.5 � 10-5 mg·kg bw-1 ·d-1 ), which raises concern for potential biological effects

Gobas, Frank

110

Food Webs and the Dimensionality of Trophic Niche Space  

Microsoft Academic Search

If the trophic niche of a kind of organism is a connected region in niche space, then it is possible for trophic niche overlaps to be described in a one-dimensional niche space if and only if the trophic niche overlap graph is an interval graph. An analysis of 30 food webs, using the combinatorial theory of interval graphs, suggests that

Joel E. Cohen

1977-01-01

111

Predator foraging behaviour drives food-web topological structure  

Microsoft Academic Search

Summary 1. The structure and dynamics of prey populations are shaped by the foraging behaviours of their predators. Yet, there is still little documentation on how distinct predator foraging types control biodiversity, food-web architecture and ecosystem functioning. 2. We experimentally compared the effects of model fish species of two major foraging types of lake planktivores: a size-selective visual feeder (bluegill),

Xavier Lazzaro; Gérard Lacroix; Benoît Gauzens; Jacques Gignoux; Stéphane Legendre

2009-01-01

112

ORIGINAL PAPER Food web overlap among native axolotl (Ambystoma  

E-print Network

ORIGINAL PAPER Food web overlap among native axolotl (Ambystoma mexicanum) and two exotic fishes period, wild populations of the microendemic axolotl salamander (Ambystoma mexicanum) have been dra two exotic fishes: carp and tilapia, and the native axolotl. Axolotl had more diverse diets

Vander Zanden, Jake

113

Using a Simulation To Teach Food Web Dynamics.  

ERIC Educational Resources Information Center

Reports on research that tested the effect of using a computer simulation to teach the concept of a food web to nonbiology majors in a large introductory course. Concludes that the use of the simulation resulted in significantly better performance on an open-ended essay question for those students who used the software, particularly for average…

Rueter, John G.; Perrin, Nancy A.

1999-01-01

114

Food caching in orb-web spiders (Araneae: Araneoidea)  

NASA Astrophysics Data System (ADS)

Caching or storing surplus prey may reduce the risk of starvation during periods of food deprivation. While this behaviour occurs in a variety of birds and mammals, it is infrequent among invertebrates. However, golden orb-web spiders, Nephila edulis, incorporate a prey cache in their relatively permanent web, which they feed on during periods of food shortage. Heavier spiders significantly reduced weight loss if they were able to access a cache, but lost weight if the cache was removed. The presence or absence of stored prey had no effect on the weight loss of lighter spiders. Furthermore, N. edulis always attacked new prey, irrespective of the number of unprocessed prey in the web. In contrast, females of Argiope keyserlingi, who build a new web every day and do not cache prey, attacked fewer new prey items if some had already been caught. Thus, a necessary pre-adaptation to the evolution of prey caching in orb-web spiders may be a durable or permanent web, such as that constructed by Nephila.

Champion de Crespigny, Fleur E.; Herberstein, Marie E.; Elgar, Mark A.

2001-01-01

115

Food caching in orb-web spiders (Araneae: Araneoidea).  

PubMed

Caching or storing surplus prey may reduce the risk of starvation during periods of food deprivation. While this behaviour occurs in a variety of birds and mammals, it is infrequent among invertebrates. However, golden orb-web spiders, Nephila edulis, incorporate a prey cache in their relatively permanent web, which they feed on during periods of food shortage. Heavier spiders significantly reduced weight loss if they were able to access a cache, but lost weight if the cache was removed. The presence or absence of stored prey had no effect on the weight loss of lighter spiders. Furthermore, N. edulis always attacked new prey, irrespective of the number of unprocessed prey in the web. In contrast, females of Argiope keyserlingi, who build a new web every day and do not cache prey, attacked fewer new prey items if some had already been caught. Thus, a necessary preadaptation to the evolution of prey caching in orb-web spiders may be a durable or permanent web, such as that constructed by Nephila. PMID:11261355

Champion de Crespigny, F E; Herberstein, M E; Elgar, M A

2001-01-01

116

Designing an Illustrated Food Web to Teach Ecological Concepts: Challenges and Solutions.  

ERIC Educational Resources Information Center

Argues that food webs are an efficient method through which to communicate the core idea of ecology--that all living things are interconnected. Assesses the challenges and solutions to using illustrated food webs. (Author/CCM)

Godkin, Celia M.

1999-01-01

117

TROPHIC NETWORK MODELS AND PREDICTION OF TOXIC SUBSTANCES ACCUMULATION IN FOOD WEBS  

Microsoft Academic Search

The term food web or trophic network defines a set of interconnected food chains by which energy and materials circulate within\\u000a an ecosystem. The classical food web could be divided into two broad categories: the grazing web, which typically begins with\\u000a green plants, algae, or photosynthesizing plankton, and the detrital web, which begins with organic debris. In a grazing web,

Arturas Razinkovas

118

Assimilation of Diazotrophic Nitrogen into Pelagic Food Webs  

PubMed Central

The fate of diazotrophic nitrogen (ND) fixed by planktonic cyanobacteria in pelagic food webs remains unresolved, particularly for toxic cyanophytes that are selectively avoided by most herbivorous zooplankton. Current theory suggests that ND fixed during cyanobacterial blooms can enter planktonic food webs contemporaneously with peak bloom biomass via direct grazing of zooplankton on cyanobacteria or via the uptake of bioavailable ND (exuded from viable cyanobacterial cells) by palatable phytoplankton or microbial consortia. Alternatively, ND can enter planktonic food webs post-bloom following the remineralization of bloom detritus. Although the relative contribution of these processes to planktonic nutrient cycles is unknown, we hypothesized that assimilation of bioavailable ND (e.g., nitrate, ammonium) by palatable phytoplankton and subsequent grazing by zooplankton (either during or after the cyanobacterial bloom) would be the primary pathway by which ND was incorporated into the planktonic food web. Instead, in situ stable isotope measurements and grazing experiments clearly documented that the assimilation of ND by zooplankton outpaced assimilation by palatable phytoplankton during a bloom of toxic Nodularia spumigena Mertens. We identified two distinct temporal phases in the trophic transfer of ND from N. spumigena to the plankton community. The first phase was a highly dynamic transfer of ND to zooplankton with rates that covaried with bloom biomass while bypassing other phytoplankton taxa; a trophic transfer that we infer was routed through bloom-associated bacteria. The second phase was a slowly accelerating assimilation of the dissolved-ND pool by phytoplankton that was decoupled from contemporaneous variability in N. spumigena concentrations. These findings provide empirical evidence that ND can be assimilated and transferred rapidly throughout natural plankton communities and yield insights into the specific processes underlying the propagation of ND through pelagic food webs. PMID:23840744

Woodland, Ryan J.; Holland, Daryl P.; Beardall, John; Smith, Jonathan; Scicluna, Todd; Cook, Perran L. M.

2013-01-01

119

Network structure and biodiversity loss in food webs: robustness increases with connectance  

Microsoft Academic Search

Food-web structure mediates dramatic effects of biodiversity loss including secondary and 'cascading' extinctions. We studied these effects by simulating primary species loss in 16 food webs from terrestrial and aquatic ecosystems and measuring robustness in terms of the secondary extinctions that followed. As observed in other networks, food webs are more robust to random removal of species than to selective

Jennifer A. Dunne; Santa Fe

120

Effects of Sampling Effort on Characterization of Food-Web Structure  

Microsoft Academic Search

A critical and poorly understood aspect of food-web theory concerns the possibility that variable observation effort, such as widely different sampling intensities among investigators, confounds structural food-web patterns. We evaluated this pos- sibility by simulating the effects of variable observation effort on the structure of a food web including 77 insect species found inside the stems of 10 species of

Neo D. Martinez; Bradford A. Hawkins; Hassan Ali Dawah; Brian P. Feifarek

1999-01-01

121

Humans in the urban food web: Emerging insights from Phoenix and  

E-print Network

of trophic dynamics in urban vs. desert settings (see Urban Food Web diagram, below). However, the natureHumans in the urban food web: Emerging insights from Phoenix and Baltimore P. S. Warren, E. Adley intense human activity, urbanization, alters food webs and trophic structure in biological communities

Hall, Sharon J.

122

Bacterial traits, organism mass, and numerical abundance in the detrital soil food web of Dutch  

E-print Network

LETTER Bacterial traits, organism mass, and numerical abundance in the detrital soil food web in the detrital soil food webs of grasslands in the Netherlands, using the relationship between average body mass, collembolans, detritus, food web, microbial quotient, mites, nematodes, qCO2, soil basal respiration. Ecology

Cohen, Joel E.

123

Linking soil food web structure to above-and belowground ecosystem processes: a meta-analysis  

E-print Network

1984 Linking soil food web structure to above- and belowground ecosystem processes: a meta. Soil food webs regulate nutrient flow in terrestrial soil eco- systems and control the nutrient supply, Chapman et al. 2006). A growing number of studies indicate that higher trophic levels in soil food webs (e

Sanders, Nathan J.

124

Soil acidity, ecological stoichiometry and allometric scaling in grassland food webs  

E-print Network

Soil acidity, ecological stoichiometry and allometric scaling in grassland food webs C H R I S T I associated with allometry in soil food webs (supporting information available online). Our results have broad relationships, nitrogen, phosphorus, soil food webs Received 15 December 2008; revised version received 14

Elser, Jim

125

Carbon steady-state model of the planktonic food web of Lake Biwa, Japan  

E-print Network

after degradation of detritus to release dissolved organic carbon. Keywords: detritus, food web, lakeCarbon steady-state model of the planktonic food web of Lake Biwa, Japan NATHALIE NIQUIL,* GRETTA planktonic food web in the surface mixed-layer of the North Basin in Lake Biwa, Japan. This model synthesised

Jackson, George

126

DEVELOPMENT, EVALUATION, AND APPLICATION OF A FOOD WEB BIOACCUMULATION MODEL FOR PCBS  

E-print Network

DEVELOPMENT, EVALUATION, AND APPLICATION OF A FOOD WEB BIOACCUMULATION MODEL FOR PCBS IN THE STRAIT Management Title of Research Project: Development, Evaluation, and Application of a Food Web Bioaccumulation of Georgia; food web; sediment quality guidelines iii #12;ACKNOWLEDGEMENTS I sincerely thank Frank Gobas, my

127

Food webs and the transmission of parasites to marine fish.  

PubMed

Helminth parasites of fish in marine systems are often considered to be generalists, lacking host specificity for both intermediate and definitive hosts. In addition, many parasites in marine waters possess life cycles consisting of long-lived larval stages residing in intermediate and paratenic hosts. These properties are believed to be adaptations to the long food chains and the low densities of organisms distributed over broad spatial scales that are characteristic of open marine systems. Moreover, such properties are predicted to lead to the homogenization of parasite communities among fish species. Yet, these communities can be relatively distinct among marine fishes. For benthos, the heterogeneous horizontal distribution of invertebrates and fish with respect to sediment quality and water depth contributes to the formation of distinct parasite communities. Similarly, for the pelagic realm, vertical partitioning of animals with depth will lead to the segregation of parasites among fish hosts. Within each habitat, resource partitioning in terms of dietary preferences of fish further contributes to the establishment of distinct parasite assemblages. Parasite distributions are predicted to be superimposed on distributional patterns of free-living animals that participate as hosts in parasite life cycles. The purpose of this review is first, to summarize distribution patterns of invertebrates and fish in the marine environment and relate these patterns to helminth transmission. Second, patterns of transmission in marine systems are interpreted in the context of food web structure. Consideration of the structure and dynamics of food webs permits predictions about the distribution and abundance of parasites. Lastly, parasites that influence food web structure by regulating the abundance of dominant host species are briefly considered in addition to the effects of pollution and exploitation on food webs and parasite transmission. PMID:12396218

Marcogliese, D J

2002-01-01

128

Benchmarking successional progress in a quantitative food web.  

PubMed

Central to ecology and ecosystem management, succession theory aims to mechanistically explain and predict the assembly and development of ecological communities. Yet processes at lower hierarchical levels, e.g. at the species and functional group level, are rarely mechanistically linked to the under-investigated system-level processes which drive changes in ecosystem properties and functioning and are comparable across ecosystems. As a model system for secondary succession, seasonal plankton succession during the growing season is readily observable and largely driven autogenically. We used a long-term dataset from large, deep Lake Constance comprising biomasses, auto- and heterotrophic production, food quality, functional diversity, and mass-balanced food webs of the energy and nutrient flows between functional guilds of plankton and partly fish. Extracting population- and system-level indices from this dataset, we tested current hypotheses about the directionality of successional progress which are rooted in ecosystem theory, the metabolic theory of ecology, quantitative food web theory, thermodynamics, and information theory. Our results indicate that successional progress in Lake Constance is quantifiable, passing through predictable stages. Mean body mass, functional diversity, predator-prey weight ratios, trophic positions, system residence times of carbon and nutrients, and the complexity of the energy flow patterns increased during succession. In contrast, both the mass-specific metabolic activity and the system export decreased, while the succession rate exhibited a bimodal pattern. The weighted connectance introduced here represents a suitable index for assessing the evenness and interconnectedness of energy flows during succession. Diverging from earlier predictions, ascendency and eco-exergy did not increase during succession. Linking aspects of functional diversity to metabolic theory and food web complexity, we reconcile previously disjoint bodies of ecological theory to form a complete picture of successional progress within a pelagic food web. This comprehensive synthesis may be used as a benchmark for quantifying successional progress in other ecosystems. PMID:24587353

Boit, Alice; Gaedke, Ursula

2014-01-01

129

Anthropogenic alterations of lotic food web structure: evidence from the use of nitrogen isotopes  

Microsoft Academic Search

Understanding the processes that regulate food chain length in nature is a classic theme in ecology. Two factors expected to explain variation in food chain length are resource availability (productivity) and environmental stress. We examined the impact of anthropogenic activities, both a source of stress and productivity, on lotic food webs using two simple food web descriptors based on stable

Caroline Anderson; Gilbert Cabana

2009-01-01

130

Ingestion and transfer of microplastics in the planktonic food web.  

PubMed

Experiments were carried out with different Baltic Sea zooplankton taxa to scan their potential to ingest plastics. Mysid shrimps, copepods, cladocerans, rotifers, polychaete larvae and ciliates were exposed to 10 ?m fluorescent polystyrene microspheres. These experiments showed ingestion of microspheres in all taxa studied. The highest percentage of individuals with ingested spheres was found in pelagic polychaete larvae, Marenzelleria spp. Experiments with the copepod Eurytemora affinis and the mysid shrimp Neomysis integer showed egestion of microspheres within 12 h. Food web transfer experiments were done by offering zooplankton labelled with ingested microspheres to mysid shrimps. Microscopy observations of mysid intestine showed the presence of zooplankton prey and microspheres after 3 h incubation. This study shows for the first time the potential of plastic microparticle transfer via planktonic organisms from one trophic level (mesozooplankton) to a higher level (macrozooplankton). The impacts of plastic transfer and possible accumulation in the food web need further investigations. PMID:24220023

Setälä, Outi; Fleming-Lehtinen, Vivi; Lehtiniemi, Maiju

2014-02-01

131

Food webs and carbon flux in the Barents Sea  

Microsoft Academic Search

Within the framework of the physical forcing, we describe and quantify the key ecosystem components and basic food web structure of the Barents Sea. Emphasis is given to the energy flow through the ecosystem from an end-to-end perspective, i.e. from bacteria, through phytoplankton and zooplankton to fish, mammals and birds. Primary production in the Barents is on average 93gCm?2y?1, but

Paul Wassmann; Marit Reigstad; Tore Haug; Bert Rudels; Michael L. Carroll; Haakon Hop; Geir Wing Gabrielsen; Stig Falk-Petersen; Stanislav G. Denisenko; Elena Arashkevich; Dag Slagstad; Olga Pavlova

2006-01-01

132

Simulating Food Web Dynamics along a Gradient: Quantifying Human Influence  

PubMed Central

Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics could greatly contribute to understanding various aspects of functional diversity. PMID:22768346

Jordan, Ferenc; Gjata, Nerta; Mei, Shu; Yule, Catherine M.

2012-01-01

133

Road Salt Stress Induces Novel Food Web Structure and Interactions  

Microsoft Academic Search

Freshwater salinization is an emerging global concern, and in northern latitudes can be largely attributed to road deicer\\u000a applications during winter and spring. To investigate the effects of road salt contamination on pond food webs, we manipulated\\u000a trophic structure and salt in experimental pond communities. In May 2008, we inoculated forty 600-L pond mesocosms with algae\\u000a and zooplankton. Using a

Robin J. Van Meter; Christopher M. Swan; Jeff Leips; Joel W. Snodgrass

134

Does invasion of hybrid cordgrass change estuarine food webs?  

Microsoft Academic Search

Studies examining the impacts of introduced species on food webs often focus on the top-down effects of introduced predators.\\u000a However, marine and estuarine systems have been invaded by plants that have the potential to alter carbon and nitrogen sources\\u000a available to consumers. In San Francisco Bay, California, USA, hybridized cordgrass Spartina alterniflora × foliosa is adding C4 carbon biomass to this system.

Elizabeth D. Brusati; Edwin D. Grosholz

2009-01-01

135

Simulating food web dynamics along a gradient: quantifying human influence.  

PubMed

Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics could greatly contribute to understanding various aspects of functional diversity. PMID:22768346

Jordán, Ferenc; Gjata, Nerta; Mei, Shu; Yule, Catherine M

2012-01-01

136

Rescaling the trophic structure of marine food webs  

PubMed Central

Measures of trophic position (TP) are critical for understanding food web interactions and human-mediated ecosystem disturbance. Nitrogen stable isotopes (?15N) provide a powerful tool to estimate TP but are limited by a pragmatic assumption that isotope discrimination is constant (change in ?15N between predator and prey, ?15N = 3.4‰), resulting in an additive framework that omits known ?15N variation. Through meta-analysis, we determine narrowing discrimination from an empirical linear relationship between experimental ?15N and ?15N values of prey consumed. The resulting scaled ?15N framework estimated reliable TPs of zooplanktivores to tertiary piscivores congruent with known feeding relationships that radically alters the conventional structure of marine food webs. Apex predator TP estimates were markedly higher than currently assumed by whole-ecosystem models, indicating perceived food webs have been truncated and species-interactions over simplified. The scaled ?15N framework will greatly improve the accuracy of trophic estimates widely used in ecosystem-based management. PMID:24308860

Hussey, Nigel E; MacNeil, M Aaron; McMeans, Bailey C; Olin, Jill A; Dudley, Sheldon FJ; Cliff, Geremy; Wintner, Sabine P; Fennessy, Sean T; Fisk, Aaron T

2014-01-01

137

Modelling PCB bioaccumulation in a Baltic food web.  

PubMed

A steady state model is developed to describe the bioaccumulation of organic contaminants by 14 species in a Baltic food web including pelagic and benthic aquatic organisms. The model is used to study the bioaccumulation of five PCB congeners of different chlorination levels. The model predictions are evaluated against monitoring data for five of the species in the food web. Predicted concentrations are on average within a factor of two of measured concentrations. The model shows that all PCB congeners were biomagnified in the food web, which is consistent with observations. Sensitivity analysis reveals that the single most sensitive parameter is log K(OW). The most sensitive environmental parameter is the annual average temperature. Although not identified amongst the most sensitive input parameters, the dissolved concentration in water is believed to be important because of the uncertainty in its determination. The most sensitive organism-specific input parameters are the fractional respiration of species from the water column and sediment pore water, which are also difficult to determine. Parameters such as feeding rate, growth rate and lipid content of organism are only important at higher trophic levels. PMID:17291648

Nfon, Erick; Cousins, Ian T

2007-07-01

138

Tracking the autochthonous carbon transfer in stream biofilm food webs.  

PubMed

Food webs in the rhithral zone rely mainly on allochthonous carbon from the riparian vegetation. However, autochthonous carbon might be more important in open canopy streams. In streams, most of the microbial activity occurs in biofilms, associated with the streambed. We followed the autochthonous carbon transfer toward bacteria and grazing protozoa within a stream biofilm food web. Biofilms that developed in a second-order stream (Thuringia, Germany) were incubated in flow channels under climate-controlled conditions. Six-week-old biofilms received either ¹³C- or ¹²C-labeled CO?, and uptake into phospholipid fatty acids was followed. The dissolved inorganic carbon of the flow channel water became immediately labeled. In biofilms grown under 8-h light/16-h dark conditions, more than 50% of the labeled carbon was incorporated in biofilm algae, mainly filamentous cyanobacteria, pennate diatoms, and nonfilamentous green algae. A mean of 29% of the labeled carbon reached protozoan grazer. The testate amoeba Pseudodifflugia horrida was highly abundant in biofilms and seemed to be the most important grazer on biofilm bacteria and algae. Hence, stream biofilms dominated by cyanobacteria and algae seem to play an important role in the uptake of CO? and transfer of autochthonous carbon through the microbial food web. PMID:22067054

Risse-Buhl, Ute; Trefzger, Nicolai; Seifert, Anne-Gret; Schönborn, Wilfried; Gleixner, Gerd; Küsel, Kirsten

2012-01-01

139

Rescaling the trophic structure of marine food webs.  

PubMed

Measures of trophic position (TP) are critical for understanding food web interactions and human-mediated ecosystem disturbance. Nitrogen stable isotopes (?(15) N) provide a powerful tool to estimate TP but are limited by a pragmatic assumption that isotope discrimination is constant (change in ?(15) N between predator and prey, ?(15) N = 3.4‰), resulting in an additive framework that omits known ?(15) N variation. Through meta-analysis, we determine narrowing discrimination from an empirical linear relationship between experimental ?(15) N and ?(15) N values of prey consumed. The resulting scaled ?(15) N framework estimated reliable TPs of zooplanktivores to tertiary piscivores congruent with known feeding relationships that radically alters the conventional structure of marine food webs. Apex predator TP estimates were markedly higher than currently assumed by whole-ecosystem models, indicating perceived food webs have been truncated and species-interactions over simplified. The scaled ?(15) N framework will greatly improve the accuracy of trophic estimates widely used in ecosystem-based management. PMID:24308860

Hussey, Nigel E; Macneil, M Aaron; McMeans, Bailey C; Olin, Jill A; Dudley, Sheldon F J; Cliff, Geremy; Wintner, Sabine P; Fennessy, Sean T; Fisk, Aaron T

2014-02-01

140

Ecological significance of hazardous concentrations in a planktonic food web.  

PubMed

Species sensitivity distributions (SSDs) are statistical distributions that are used to estimate the potentially affected fraction (PAF) of species at a given toxicant concentration, the hazardous concentration for that fraction of species (HC(PAF)). Here, we use an aquatic food web model that includes 14 phytoplankton and 6 zooplankton species to estimate the number of species experiencing a biomass reduction when the food web is exposed to the HC(PAF) and this for 1000 hypothetical toxicants and for PAF=5-30%. When choosing a 20% decrease as a cut-off to categorize a species' biomass as affected, 0-1 and 2-5 out of the 20 species were affected at the HC(5) and HC(30), respectively. From this, it can be concluded that the PAF is a relatively good estimator of the number of affected species. However, when phytoplankton species experiencing >or=20% biomass increase were also classified as affected, the number of affected species predicted by the food web model varied strongly among toxicants for PAF >5, with 2-16 out of 20 species affected at the HC(30). Phytoplankton species with extreme (both high and low) values for uptake rates and light limitation constants experienced smaller effects on their biomass than phytoplankton species with more average parameter values. We conclude that, next to measures of toxicity, ecological characteristics of species may help understanding ecological effects occurring in ecosystems also. PMID:20045193

De Laender, Frederik; Soetaert, Karline; De Schamphelaere, Karel A C; Middelburg, Jack J; Janssen, Colin R

2010-03-01

141

Scaling behaviors of weighted food webs as energy transportation networks.  

PubMed

Food webs can be regarded as energy transporting networks in which the weight of each edge denotes the energy flux between two species. By investigating 21 empirical weighted food webs as energy flow networks, we found several ubiquitous scaling behaviors. Two random variables A(i) and C(i) defined for each vertex i, representing the total flux (also called vertex intensity) and total indirect effect or energy store of i, were found to follow power law distributions with the exponents alpha approximately 1.32 and beta approximately 1.33, respectively. Another scaling behavior is the power law relationship, C(i) approximately A(i)(eta), where eta approximately 1.02. This is known as the allometric scaling power law relationship because A(i) can be treated as metabolism and C(i) as the body mass of the sub-network rooted from the vertex i, according to the algorithm presented in this paper. Finally, a simple relationship among these power law exponents, eta=(alpha-1)/(beta-1), was mathematically derived and tested by the empirical food webs. PMID:20303987

Zhang, Jiang; Guo, Liangpeng

2010-06-01

142

Successional dynamics in the seasonally forced diamond food web.  

PubMed

Plankton seasonal succession is a classic example of nonequilibrium community dynamics. Despite the fact that it has been well studied empirically, it lacks a general quantitative theory. Here we investigate a food web model that includes a resource, two phytoplankton, and a shared grazer-the diamond food web-in a seasonal environment. The model produces a number of successional trajectories that have been widely discussed in the context of the verbal Plankton Ecology Group model of succession, such as a spring bloom of a good competitor followed by a grazer-induced clear-water phase, setting the stage for the late-season dominance of a grazer-resistant species. It also predicts a novel, counterintuitive trajectory where the grazer-resistant species has both early- and late-season blooms. The model often generates regular annual cycles but sometimes produces multiyear cycles or chaos, even with identical forcing each year. Parameterizing the model, we show how the successional trajectory depends on nutrient supply and the length of the growing season, two key parameters that vary among water bodies. This model extends nonequilibrium theory to food webs and is a first step toward a quantitative theory of plankton seasonal succession. PMID:22673647

Klausmeier, Christopher A; Litchman, Elena

2012-07-01

143

Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea  

NASA Astrophysics Data System (ADS)

The structure of the food web in the vicinity of a marginal ice zone was investigated in the western Weddell Sea during austral autumn 1986. The diets of 40 species of zooplankton and micronekton occurring in the epipelagic zone were examined and compared using non-hierarchical clustering procedures. Over half the species were in three clusters of predominantly small-particle (phytoplankton; protozoans) grazers. These included biomass dominants Calanoides acutus, Calanus propinquus, Metridia gerlachei and Salpa thompsoni. Six clusters contained omnivores that had diets consisting of small particles as well as a substantial fraction of metozoan food. Among these was Euphausia superba. Seven groups were carnivorous, including species of copepods (1), chaetognaths (3), and fishes (5). Copepods were the most frequent food of carnivores; however krill also were important in the diets of three fish species. Among small-particle grazers, phytoplankton occurred more frequently in guts of individuals from open water; carnivory was more in evidence in samples collected under the pack ice. Regional comparisons of material taken on this and several previous cruises indicate that, in most of the dominant species, diets remain relatively consistent with respect to major food categories. Seasonal impact on feeding dynamics appears to be great: the guts of grazing species were generally much more full (visual evidence) during summer bloom conditions than during the autumn. The following trophic sequence is suggested for grazing zooplankton species in ice-covered regions of the Antarctic: (1) Active small-particle grazing during the summer bloom period; (2) reduced ingestion rates in autumn as primary production declines and the system becomes more oligotrophic, with some species augmenting grazing with carnivory; (3) descent of zooplankton biomass species into the mesopelagic zone in late autumn-early winter with feeding largely terminated. The sequence applies to the dominant zooplankton biomass species. Feeding dynamics and vertical distribution of several of the important larger sized grazing species, such as Euphausia superba and Salpa thompsoni, remain largely unknown

Hopkins, Thomas L.; Torres, Joseph J.

1989-04-01

144

Food-Web Structure of Seagrass Communities across Different Spatial Scales and Human Impacts  

PubMed Central

Seagrass beds provide important habitat for a wide range of marine species but are threatened by multiple human impacts in coastal waters. Although seagrass communities have been well-studied in the field, a quantification of their food-web structure and functioning, and how these change across space and human impacts has been lacking. Motivated by extensive field surveys and literature information, we analyzed the structural features of food webs associated with Zostera marina across 16 study sites in 3 provinces in Atlantic Canada. Our goals were to (i) quantify differences in food-web structure across local and regional scales and human impacts, (ii) assess the robustness of seagrass webs to simulated species loss, and (iii) compare food-web structure in temperate Atlantic seagrass beds with those of other aquatic ecosystems. We constructed individual food webs for each study site and cumulative webs for each province and the entire region based on presence/absence of species, and calculated 16 structural properties for each web. Our results indicate that food-web structure was similar among low impact sites across regions. With increasing human impacts associated with eutrophication, however, food-web structure show evidence of degradation as indicated by fewer trophic groups, lower maximum trophic level of the highest top predator, fewer trophic links connecting top to basal species, higher fractions of herbivores and intermediate consumers, and higher number of prey per species. These structural changes translate into functional changes with impacted sites being less robust to simulated species loss. Temperate Atlantic seagrass webs are similar to a tropical seagrass web, yet differed from other aquatic webs, suggesting consistent food-web characteristics across seagrass ecosystems in different regions. Our study illustrates that food-web structure and functioning of seagrass habitats change with human impacts and that the spatial scale of food-web analysis is critical for determining results. PMID:21811637

Coll, Marta; Schmidt, Allison; Romanuk, Tamara; Lotze, Heike K.

2011-01-01

145

Food web dynamics in the Scotia Sea in summer: A stable isotope study  

NASA Astrophysics Data System (ADS)

The pelagic food web of the Scotia Sea was studied by analysing natural abundances of nitrogen and carbon stable isotopes of primary producers and pelagic consumers, sampled from the seasonal ice edge in the south to the Antarctic Polar Front in the north. The analysis covered, within a single mid-summer period, particulate organic matter (POM) and 38 taxa, ranging from suspension feeding copepods and salps to omnivorous euphausiids, pelagic fish and higher, land-based predators including fur seals, penguins and flying birds. Spatial variation in ? 15N of POM correlated well with nutrient availability and primary productivity. Latitudinal differences in ? 13C of POM were closely linked to variations in temperature, nutrients and productivity depending on the frontal region sampled. This translated to equivalent (although smaller) regional ? 13C differences among higher trophic levels. The trophic positions of species based on isotope values broadly agreed with previously published dietary data with three important exceptions. First, the carnivorous amphipod Themisto gaudichaudii had anomalously low ? 15N values. Second, Euphausia superba had ? 15N values that were also surprisingly low, considering the abundant literature suggesting its omnivory. Third, the copepod Rhincalanus gigas, considered a suspension feeder, had unexpectedly high ? 15N values rather more in keeping with omnivorous feeding. The consumer ? 15N values ranged from 1.2‰ (min.) measured in Salpa thompsoni (designated here as trophic level (TL) 2 across all regions) to 15.2‰ (max.) measured in white-chinned petrels ( Procellaria aequinoctialis, calculated as TL5 relative to the TL2 of salps). Excluding seabirds, the resulting food chain length of 3.7 TL (above POM at TL1) was lower than in most other Southern Ocean and temperate marine pelagic ecosystems. The majority (60%) of vertebrate predators occupied only 1-1.5 trophic levels above the herbivorous suspension feeders such as krill. This indicates the existence of the classic short food chain of POM-suspension feeder-vertebrate predator. However the presence of trophic levels 4 and above indicates the existence of alternative trophic pathways, for example involving myctophid fish or carrion, and that some wide-ranging predators which breed at South Georgia also feed outside the region. This conclusion is supported first by the continuum of ? 15N values between krill, suspension feeding copepods and myctophid fish, and secondly by higher trophic levels in several of the myctophid species in the low-krill region of the northern Scotia Sea, suggesting latitudinal differences in food web structure and food chain length.

Stowasser, G.; Atkinson, A.; McGill, R. A. R.; Phillips, R. A.; Collins, M. A.; Pond, D. W.

2012-01-01

146

Ecological Stoichiometry, Biogeochemical Cycling, Invasive Species, and Aquatic Food Webs: San Francisco Estuary and Comparative Systems  

Microsoft Academic Search

Eutrophication has altered food webs across aquatic systems, but effects of nutrient stoichiometry (varying nutrient ratios) on ecosystem structure and function have received less attention. A prevailing assumption has been that nutrients are not ecologically relevant unless concentrations are limiting to phytoplankton. However, changes in nutrient stoichiometry fundamentally affect food quality at all levels of the food web. Here, 30-year

Patricia M. Glibert; David Fullerton; Joann M. Burkholder; Jeffrey C. Cornwell; Todd M. Kana

2011-01-01

147

8 Food Webs in the Ocean: Who Eats Whom and How Much?  

E-print Network

8 Food Webs in the Ocean: Who Eats Whom and How Much? Andrew W. Trites Marine Mammal Research Unit, Fisheries Centre, University of British Columbia, Vancouver, Canada Abstract Over 100 food webs have been published for marine ecosystems to describe the transfer of food energy from its source in plants, through

148

Deep-Sea Research II 52 (2005) 757780 Linking oceanic food webs to coastal production and  

E-print Network

Deep-Sea Research II 52 (2005) 757­780 Linking oceanic food webs to coastal production and growth (NEMURO), a food web model (Ecopath/Ecosim), and a bioenergetics model for pink salmon (Oncorhynchus gorbuscha)--were linked to examine the relationship between seasonal zooplankton dynamics and annual food

149

Nutrient subsidies to belowground microbes impact aboveground food web interactions.  

PubMed

Historically, terrestrial food web theory has been compartmentalized into interactions among aboveground or belowground communities. In this study we took a more synthetic approach to understanding food web interactions by simultaneously examining four trophic levels and investigating how nutrient (nitrogen and carbon) and detrital subsidies impact the ability of the belowground microbial community to alter the abundance of aboveground arthropods (herbivores and predators) associated with the intertidal cord grass Spartina alterniflora. We manipulated carbon, nitrogen, and detrital resources in a field experiment and measured decomposition rate, soil nitrogen pools, plant biomass and quality, herbivore density, and arthropod predator abundance. Because carbon subsidies impact plant growth only indirectly (microbial pathways), whereas nitrogen additions both directly (plant uptake) and indirectly (microbial pathways) impact plant primary productivity, we were able to assess the effect of both belowground soil microbes and nutrient availability on aboveground herbivores and their predators. Herbivore density in the field was suppressed by carbon supplements. Carbon addition altered soil microbial dynamics (net potential ammonification, litter decomposition rate, DON [dissolved organic N] concentration), which limited inorganic soil nitrogen availability and reduced plant size as well as predator abundance. Nitrogen addition enhanced herbivore density by increasing plant size and quality directly by increasing inorganic soil nitrogen pools, and indirectly by enhancing microbial nitrification. Detritus adversely affected aboveground herbivores mainly by promoting predator aggregation. To date, the effects of carbon and nitrogen subsidies on salt marshes have been examined as isolated effects on either the aboveground or the belowground community. Our results emphasize the importance of directly addressing the soil microbial community as a factor that influences aboveground food web structure by affecting plant size and aboveground plant nitrogen. PMID:16869430

Hines, Jes; Megonigal, J Patrick; Denno, Robert F

2006-06-01

150

Fluctuating silicate:nitrate ratios and coastal plankton food webs.  

PubMed

Marine diatoms require dissolved silicate to form an external shell, and their growth becomes Si-limited when the atomic ratio of silicate to dissolved inorganic nitrogen (Si:DIN) approaches 1:1, also known as the "Redfield ratio." Fundamental changes in the diatom-to-zooplankton-to-higher trophic level food web should occur when this ratio falls below 1:1 and the proportion of diatoms in the phytoplankton community is reduced. We quantitatively substantiate these predictions by using a variety of data from the Mississippi River continental shelf, a system in which the Si:DIN loading ratio has declined from around 3:1 to 1:1 during this century because of land-use practices in the watershed. We suggest that, on this shelf, when the Si:DIN ratio in the river decreases to less than 1:1, then (i) copepod abundance changes from >75% to <30% of the total mesozooplankton, (ii) zooplankton fecal pellets become a minor component of the in situ primary production consumed, and (iii) bottom-water oxygen consumption rates become less dependent on relatively fast-sinking (diatom-rich) organic matter packaged mostly as zooplankton fecal pellets. This coastal ecosystem appears to be a pelagic food web dynamically poised to be either a food web composed of diatoms and copepods or one with potentially disruptive harmful algal blooms. The system is directed between these two ecosystem states by Mississippi River water quality, which is determined by land-use practices far inland. PMID:9789038

Turner, R E; Qureshi, N; Rabalais, N N; Dortch, Q; Justi?, D; Shaw, R F; Cope, J

1998-10-27

151

Land use alters the resistance and resilience of soil food webs to drought  

NASA Astrophysics Data System (ADS)

Soils deliver several ecosystem services including carbon sequestration and nutrient cycling, which are of central importance to climate mitigation and sustainable food production. Soil biota play an important role in carbon and nitrogen cycling, and, although the effects of land use on soil food webs are well documented, the consequences for their resistance and resilience to climate change are not known. We compared the resistance and resilience to drought--which is predicted to increase under climate change--of soil food webs of two common land-use systems: intensively managed wheat with a bacterial-based soil food web and extensively managed grassland with a fungal-based soil food web. We found that the fungal-based food web, and the processes of C and N loss it governs, of grassland soil was more resistant, although not resilient, and better able to adapt to drought than the bacterial-based food web of wheat soil. Structural equation modelling revealed that fungal-based soil food webs and greater microbial evenness mitigated C and N loss. Our findings show that land use strongly affects the resistance and resilience of soil food webs to climate change, and that extensively managed grassland promotes more resistant, and adaptable, fungal-based soil food webs.

de Vries, Franciska T.; Liiri, Mira E.; Bjørnlund, Lisa; Bowker, Matthew A.; Christensen, Søren; Setälä, Heikki M.; Bardgett, Richard D.

2012-04-01

152

Perfluoroalkyl contaminants in a food web from Lake Ontario.  

PubMed

Perfluorooctane sulfonate (PFOS) is a persistent and bioaccumulative perfluorinated acid detectable in humans and wildlife worldwide that has alerted scientists to examine the environmental fate of other fluorinated organic contaminants. Recently a homologous series of perfluoroalkyl carboxylates (PFCAs) was detected in the Arctic, yet little is known about their sources, breadth of contamination, or environmental distribution. In this study we analyzed for PFOS, the homologous series of PFCAs ranging from 8 to 15 carbons in chain length, and the PFOS-precursor heptadecafluorooctane sulfonamide (FOSA) in various organisms from a food web of Lake Ontario. The sampled organisms included a top predator fish, lake trout (Salvelinus namaycush), three forage fish species including rainbow smelt (Osmerus mordax), slimy sculpin (Cottus cognatus), and alewife (Alosa pseudoharengus), and two invertebrates Diporeia (Diporeia hoyi) and Mysis (Mysis relicta). A striking finding was that the highest mean concentration for each fluorinated contaminantwas detected in the benthic macroinvertebrate Diporeia, which occupies the lowest trophic level of all organisms analyzed. Perfluorinated acid concentrations in Diporeia were often 10-fold higher than in Mysis, a predominantly pelagic feeder, suggesting that a major source of perfluoroalkyl contaminants to this food web was the sediment, not the water. PFOS was the dominant acid in all samples, but long-chain PFCAs, ranging in length from 8 to 15 carbons, were also detected in most samples between <0.5 and 90 ng/ g. Among Mysis and the more pelagic fish species (e.g. excluding Diporeia and sculpin) there was evidence for biomagnification, but the influence of foraging on highly contaminated Diporeia and sculpin by these fish may have overestimated trophic magnification factors (TMFs), which ranged from 0.51 for FOSA to 5.88 for PFOS. By accounting for the known diet composition of lake trout, it was shown that bioaccumulation was indeed occurring at the top of the food web for all perfluoroalkyl compounds except PFOA. Future monitoring at other locations in Lake Ontario, and in other aquatic environments, is necessary to determine if these food web dynamics are widespread. Archived lake trout samples collected between 1980 and 2001 showed that mean whole body PFOS concentrations increased from 43 to 180 ng/g over this period, but not linearly, and may have been indirectly influenced by the invasion and proliferation of zebra mussels (Dreissena polymorpha) through effects on the population and ecology of forage fishes. PMID:15543740

Martin, Jonathan W; Whittle, D Michael; Muir, Derek C G; Mabury, Scott A

2004-10-15

153

Food-web based unified model of macro- and microevolution  

NASA Astrophysics Data System (ADS)

We incorporate the generic hierarchical architecture of foodwebs into a “unified” model that describes both micro- and macroevolutions within a single theoretical framework. This model describes the microevolution in detail by accounting for the birth, ageing, and natural death of individual organisms as well as prey-predator interactions on a hierarchical dynamic food web. It also provides a natural description of random mutations and speciation (origination) of species as well as their extinctions. The distribution of lifetimes of species follows an approximate power law only over a limited regime.

Chowdhury, Debashish; Stauffer, Dietrich

2003-10-01

154

Chemoattraction to dimethylsulfoniopropionate throughout the marine microbial food web.  

PubMed

Phytoplankton-produced dimethylsulfoniopropionate (DMSP) provides underwater and atmospheric foraging cues for several species of marine invertebrates, fish, birds, and mammals. However, its role in the chemical ecology of marine planktonic microbes is largely unknown, and there is evidence for contradictory functions. By using microfluidics and image analysis of swimming behavior, we observed attraction toward microscale pulses of DMSP and related compounds among several motile strains of phytoplankton, heterotrophic bacteria, and bacterivore and herbivore microzooplankton. Because microbial DMSP cycling is the main natural source of cloud-forming sulfur aerosols, our results highlight how adaptations to microscale chemical seascapes shape planktonic food webs, while potentially influencing climate at the global scale. PMID:20647471

Seymour, Justin R; Simó, Rafel; Ahmed, Tanvir; Stocker, Roman

2010-07-16

155

Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watershed  

E-print Network

­ Food web shifts Knobs #12;Reservoir · Elective strategies ­ Slow knobs · THg inputs ­ Fast knobs#12;#12;Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local food web Hg Gehrke et al. 2011. ES&T 45 (4), pp 1264­1270 #12;0 0.1 0.2 0.3 0.4 0.5 Louisiana

156

A comparison of soil food webs beneath C 3 - and C 4 -dominated grasslands  

Microsoft Academic Search

Soil food webs influence organic matter mineralization and plant nutrient availability, but the potential for plants to capitalize\\u000a on these processes by altering soil food webs has received little attention. We compared soil food webs beneath C3- and C4-grass plantings by measuring bacterial and fungal biomass and protozoan and nematode abundance repeatedly over 2 years. We\\u000a tested published expectations that C3

Mathew Dornbush; Cynthia Cambardella; Elaine Ingham; James Raich

2008-01-01

157

Rigorous conditions for food-web intervality in high-dimensional trophic niche spaces  

Microsoft Academic Search

Food webs represent trophic (feeding) interactions in ecosystems. Since the late 1970s, it has been recognized that food-webs\\u000a have a surprisingly close relationship to interval graphs. One interpretation of food-web intervality is that trophic niche\\u000a space is low-dimensional, meaning that the trophic character of a species can be expressed by a single or at most a few quantitative\\u000a traits. In

Åke Brännström; Linus Carlsson; Axel G. Rossberg

158

Biochemical tracers reveal intra-specific differences in the food webs utilized by individual seabirds  

Microsoft Academic Search

Food web structure regulates the pathways and flow rates of energy, nutrients, and contaminants to top predators. Ecologically\\u000a and physiologically meaningful biochemical tracers provide a means to characterize and quantify these transfers within food\\u000a webs. In this study, changes in the ratios of stable N isotopes (e.g., ?15N), fatty acids (FA), and persistent contaminants were used to trace food web

Craig E. Hebert; D. V. Chip Weseloh; Lewis T. Gauthier; Michael T. Arts; Robert J. Letcher

2009-01-01

159

The Past and Present Topology and Structure of Mediterranean Subtidal Rocky-shore Food Webs  

Microsoft Academic Search

The understanding of the taxonomic composition of Mediterranean subtidal rocky-shore food webs is extraordinary; the information on trophic links and food-web structure is, however, still meager. An initial description of the rocky-bottom food web of the Medes Islands off the Catalan coast includes a minimum of 1350 species organized in five trophic levels. A minimum of 151 trophic links have

Enric Sala

2004-01-01

160

Food web expansion and contraction in response to changing environmental conditions.  

PubMed

Macroscopic ecosystem properties, such as major material pathways and community biomass structure, underlie the ecosystem services on which humans rely. While ecologists have long sought to identify the determinants of the trophic height of food webs (food chain length), it is somewhat surprising how little research effort is invested in understanding changes among other food web properties across environmental conditions. Here we theoretically and empirically show how a suite of fundamental macroscopic food web structures respond, in concert, to changes in habitat accessibility using post-glacial lakes as model ecosystems. We argue that as resource accessibility increases in coupled food webs, food chain length contracts (that is, reduced predator trophic position), habitat coupling expands (that is, increasingly coupled macrohabitats) and biomass pyramid structure becomes more top heavy. Our results further support an emerging theoretical view of flexible food webs that provides a foundation for generally understanding ecosystem responses to changing environmental conditions. PMID:23033081

Tunney, Tyler D; McCann, Kevin S; Lester, Nigel P; Shuter, Brian J

2012-01-01

161

The ecological potentials of Phytomyxea ("plasmodiophorids") in aquatic food webs  

PubMed Central

The Phytomyxea (“plasmodiophorids”) including both Plasmodiophorida and Phagomyxida is a monophyletic group of Eukaryotes composed of obligate biotrophic parasites of green plants, brown algae, diatoms and stramenopiles commonly found in many freshwater, soil and marine environments. However, most research on Phytomyxea has been restricted to plant pathogenic species with agricultural importance, thereby missing the huge ecological potential of this enigmatic group of parasites. Members of the Phytomyxea can induce changes in biomass in their hosts (e.g. hypertrophies of the host tissue) under suitable environmental conditions. Upon infection they alter the metabolism of their hosts, consequently changing the metabolic status of their host. This results in an altered chemical composition of the host tissue, which impacts the diversity of species which feed on the tissues of the infected host and on the zoospores produced by the parasites. Furthermore, significant amounts of nutrients derived from the hosts, both primary producers (plants and algae) and primary consumers (litter decomposers and plant parasites [Oomycetes]), can enter the food web at different trophic levels in form of zoospores and resting spores. Large numbers of zoospores and resting spores are produced which can be eaten by secondary and tertiary consumers, such as grazing zooplankton and metazoan filter-feeders. Therefore, these microbes can act as energy-rich nutrient resources which may significantly alter the trophic relationships in fresh water, soil and marine habitats. Based on the presented data, Phytomyxea can significantly contribute to the complexity and energy transfer within food webs. PMID:21339888

2011-01-01

162

Model of carbon cycling in planktonic food webs  

SciTech Connect

A mathematical model of carbon fluxes through the heterotrophic microbial food web is developed from a synthesis of laboratory and field research. The basis of the model is the segregation of organic carbon into lability classes that are defined by bioassay experiments. Bacteria, phytoplankton, three trophic levels of zooplankton, and dissolved organic carbon (DOC) and particulate organic carbon (POC) are modeled. The descriptions of bacterial growth and utilization of the various classes of substrate were treated as universal constants in the application of the model to three distinct ecosystems, ranging from oligotrophic to highly eutrophic. The successful application of the model to these diverse ecosystems supports the basic validity of the description of the microbial food web and the dynamics of carbon flux. The model indicates that the dynamics of bacteria and protozoan zooplankton production govern the rates of oxidation of carbon entering the water column. Explicit consideration of these groups would improve the capability of eutrophication models to predict dissolved oxygen dynamics, particularly when projecting responses to loading changes.

Connolly, J.P. [HydroQual, Inc., Mahwah, NJ (United States); Coffin, R.B. [Environmental Protection Agency, Gulf Breeze, FL (United States). Environmental Research Lab.

1995-10-01

163

The ecological potentials of Phytomyxea ("plasmodiophorids") in aquatic food webs.  

PubMed

The Phytomyxea ("plasmodiophorids") including both Plasmodiophorida and Phagomyxida is a monophyletic group of Eukaryotes composed of obligate biotrophic parasites of green plants, brown algae, diatoms and stramenopiles commonly found in many freshwater, soil and marine environments. However, most research on Phytomyxea has been restricted to plant pathogenic species with agricultural importance, thereby missing the huge ecological potential of this enigmatic group of parasites. Members of the Phytomyxea can induce changes in biomass in their hosts (e.g. hypertrophies of the host tissue) under suitable environmental conditions. Upon infection they alter the metabolism of their hosts, consequently changing the metabolic status of their host. This results in an altered chemical composition of the host tissue, which impacts the diversity of species which feed on the tissues of the infected host and on the zoospores produced by the parasites. Furthermore, significant amounts of nutrients derived from the hosts, both primary producers (plants and algae) and primary consumers (litter decomposers and plant parasites [Oomycetes]), can enter the food web at different trophic levels in form of zoospores and resting spores. Large numbers of zoospores and resting spores are produced which can be eaten by secondary and tertiary consumers, such as grazing zooplankton and metazoan filter-feeders. Therefore, these microbes can act as energy-rich nutrient resources which may significantly alter the trophic relationships in fresh water, soil and marine habitats. Based on the presented data, Phytomyxea can significantly contribute to the complexity and energy transfer within food webs. PMID:21339888

Neuhauser, Sigrid; Kirchmair, Martin; Gleason, Frank H

2011-01-01

164

Non-Deterministic Modelling of Food-Web Dynamics  

PubMed Central

A novel approach to model food-web dynamics, based on a combination of chance (randomness) and necessity (system constraints), was presented by Mullon et al. in 2009. Based on simulations for the Benguela ecosystem, they concluded that observed patterns of ecosystem variability may simply result from basic structural constraints within which the ecosystem functions. To date, and despite the importance of these conclusions, this work has received little attention. The objective of the present paper is to replicate this original model and evaluate the conclusions that were derived from its simulations. For this purpose, we revisit the equations and input parameters that form the structure of the original model and implement a comparable simulation model. We restate the model principles and provide a detailed account of the model structure, equations, and parameters. Our model can reproduce several ecosystem dynamic patterns: pseudo-cycles, variation and volatility, diet, stock-recruitment relationships, and correlations between species biomass series. The original conclusions are supported to a large extent by the current replication of the model. Model parameterisation and computational aspects remain difficult and these need to be investigated further. Hopefully, the present contribution will make this approach available to a larger research community and will promote the use of non-deterministic-network-dynamics models as ‘null models of food-webs’ as originally advocated. PMID:25299245

Planque, Benjamin; Lindstr?m, Ulf; Subbey, Sam

2014-01-01

165

Non-deterministic modelling of food-web dynamics.  

PubMed

A novel approach to model food-web dynamics, based on a combination of chance (randomness) and necessity (system constraints), was presented by Mullon et al. in 2009. Based on simulations for the Benguela ecosystem, they concluded that observed patterns of ecosystem variability may simply result from basic structural constraints within which the ecosystem functions. To date, and despite the importance of these conclusions, this work has received little attention. The objective of the present paper is to replicate this original model and evaluate the conclusions that were derived from its simulations. For this purpose, we revisit the equations and input parameters that form the structure of the original model and implement a comparable simulation model. We restate the model principles and provide a detailed account of the model structure, equations, and parameters. Our model can reproduce several ecosystem dynamic patterns: pseudo-cycles, variation and volatility, diet, stock-recruitment relationships, and correlations between species biomass series. The original conclusions are supported to a large extent by the current replication of the model. Model parameterisation and computational aspects remain difficult and these need to be investigated further. Hopefully, the present contribution will make this approach available to a larger research community and will promote the use of non-deterministic-network-dynamics models as 'null models of food-webs' as originally advocated. PMID:25299245

Planque, Benjamin; Lindstrøm, Ulf; Subbey, Sam

2014-01-01

166

Coupled predator-prey oscillations in a chaotic food web.  

PubMed

Coupling of several predator-prey oscillations can generate intriguing patterns of synchronization and chaos. Theory predicts that prey species will fluctuate in phase if predator-prey cycles are coupled through generalist predators, whereas they will fluctuate in anti-phase if predator-prey cycles are coupled through competition between prey species. Here, we investigate predator-prey oscillations in a long-term experiment with a marine plankton community. Wavelet analysis of the species fluctuations reveals two predator-prey cycles that fluctuate largely in anti-phase. The phase angles point at strong competition between the phytoplankton species, but relatively little prey overlap among the zooplankton species. This food web architecture is consistent with the size structure of the plankton community, and generates highly dynamic food webs. Continued alternations in species dominance enable coexistence of the prey species through a non-equilibrium 'killing-the-winner' mechanism, as the system shifts back and forth between the two predator-prey cycles in a chaotic fashion. PMID:19845726

Benincà, Elisa; Jöhnk, Klaus D; Heerkloss, Reinhard; Huisman, Jef

2009-12-01

167

Food web structure and the evolution of ecological communities  

NASA Astrophysics Data System (ADS)

Simulations of the coevolution of many interacting species are performed using the Webworld model. The model has a realistic set of predator-prey equations that describe the population dynamics of the species for any structure of the food web. The equations account for competition between species for the same resources, and for the diet choice of predators between alternative prey according to an evolutionarily stable strategy. The set of species present undergoes long-term evolution d ue to speciation and extinction events. We summarize results obtained on the macro-evolutionary dynamics of speciations and extinctions, and on the statistical properties of the food webs that are generated by the model. Simulations begin from small numbers of species and build up to larger webs with relatively constant species number on average. The rate of origination and extinction of species are relatively high, but remain roughly balanced throughout the simulations. When a 'parent' species undergoes sp eciation, the 'child' species usually adds to the same trophic level as the parent. The chance of the child species surviving is significantly higher if the parent is on the second or third trophic level than if it is on the first level, most likely due to a wider choice of possible prey for species on higher levels. Addition of a new species sometimes causes extinction of existing species. The parent species has a high probability of extinction because it has strong competition with the new species. Non-pa rental competitors of the new species also have a significantly higher extinction probability than average, as do prey of the new species. Predators of the new species are less likely than average to become extinct.

Quince, Christopher; Higgs, Paul G.; McKane, Alan J.

168

Australian Antarctic Data Centre  

NSDL National Science Digital Library

The Australian Antarctic Division is part of the Australian Government's Department of the Environment and Heritage. Within the department's Web site is the Australian Antarctic Data Centre, which makes all scientific observations and results freely available. Data topics include weather, GIS and mapping, marine science, flora and fauna, and many other topics related to the southern continent.

2002-01-01

169

Coalescence in the Lake Washington story: Interaction strengths in a planktonic food web  

Microsoft Academic Search

Lake Washington is arguably the most famous case study of lake pollution and subsequent recovery, and the widely cited story implicates just a few major players in the lake's food web transformations. ''The Lake Washington story'' historically highlights key players that negatively affect other taxa—filamentous cyanobacteria, the influential grazer Daphnia, and its predator Neomysis. This food web model has been

Stephanie E. Hampton; Mark D. Scheuerell; Daniel E. Schindler

2006-01-01

170

Simplification of seagrass food webs across a gradient of nutrient enrichment  

Microsoft Academic Search

Anthropogenic nutrient enrichment has resulted in significant changes in food web structure. Although such changes have been associated with the loss of diversity and ecosystem services, little empirical work has been done to study food webs of similar systems across a nutrient enrichment gradient. We examined 11 seagrass beds along a gra- dient of increasing ?15N of primary consumers, where

Alexander Tewfik; Joseph B. Rasmussen; Kevin S. McCann

2007-01-01

171

Hydrological and Biogeochemical Controls on Seasonal and Spatial Differences in Food Webs in the Everglades  

Microsoft Academic Search

Stable isotopes can be used to determine the relative trophic positions of biota within a food web, and to improve our understanding of the biomagnification of contaminants. Plants at the base of the food web uptake dissolved organic carbon (DIC) and nitrogen (DIN) for growth, and their tissue reflects the isotopic composition of these sources. Animals then mirror the isotopic

C. Kendall; S. D. Wankel; B. E. Bemis; P. S. Rawlik; D. P. Krabbenhoft; T. Lange

2002-01-01

172

Neighborhood Effects on Arthropod Diversity and Food Webs Laura Taylor-Taft and Stan Faeth  

E-print Network

biodiversity and food web structure and function of arthropod communities. North Desert Village (NDV) has fourNeighborhood Effects on Arthropod Diversity and Food Webs Laura Taylor-Taft and Stan Faeth School the native Sonoran desert plant, brittlebush (Encelia farinosa) have indicated that desert remnants behave

Hall, Sharon J.

173

Suppressive service of the soil food web: Effects of environmental management  

Microsoft Academic Search

Soil food webs perform the important ecosystem services necessary to maintain both agricultural productivity and ecosystem health. Higher trophic levels in soil food webs can play a role suppressing plant parasites and affecting nutrient dynamics by modifying abundance of intermediate consumers. Natural and agricultural landscapes were sampled to compare soil faunal structure. Top-down soil suppressiveness of a parasitic nematode, Meloidogyne

Sara Sánchez-Moreno; Howard Ferris

2007-01-01

174

Soil food web components affect plant community structure during early succession  

Microsoft Academic Search

There is a growing awareness among ecologists of the strong links that exist between above- and belowground food webs. So far, the majority of studies have considered these links from the microbial point of view, usually with single plants or very simple plant communities. Here, we report the interactions between two components of the soil food web, root-feeding insects and

Alan C. Gange; Valerie K. Brown

2002-01-01

175

Exploring Fish Diversity as a Determinant of Ecosystem Properties in Aquatic Food Webs  

ERIC Educational Resources Information Center

Dramatic biodiversity changes occurring globally from species loss and invasion have altered native food webs and ecosystem processes. My research objectives are to understand the consequences of fish diversity to freshwater systems by (1) examining the food web consequences of multiple top predators, (2) determining how biodiversity influences…

Carey, Michael P.

2009-01-01

176

Benthic versus Planktonic Foundations of Three Lake Superior Coastal Food Webs  

EPA Science Inventory

The structure of aquatic food webs can provide information on system function, trophic dynamics and, potentially, responses to anthropogenic stressors. Stable isotope analyses in a Lake Superior coastal wetland (Allouez Bay, WI, USA) revealed that the food web was based upon carb...

177

The Role of Food Web Models in the Environmental Management of Bioaccumulative Chemicals  

Microsoft Academic Search

When properly calibrated, food web models can be used to estimate the tissue concentrations of bioaccumulative chemicals in aquatic organisms at various trophic levels. In general, such models are dependent on the knowledge of the bioenergetics and feeding interactions within a food web and the sediment and water concentrations of chemicals. The results of a preliminary probabilistic model that was

Timothy J. Iannuzzi; David F. Ludwig

2000-01-01

178

Influence of food web structure on the growth and bioenergetics of lake trout (Salvelinus namaycush)  

E-print Network

Influence of food web structure on the growth and bioenergetics of lake trout (Salvelinus namaycush energy budgets of lake trout (Salvelinus namaycush) populations in contrasting food webs. Nonpiscivorous des populations de touladis (Salvelinus namaycush) dans divers réseaux trophiques. Les populations de

Rasmussen, Joseph

179

Developing a broader scientific foundation for river restoration: Columbia River food webs  

PubMed Central

Well-functioning food webs are fundamental for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure—without explicitly considering food webs—has been less successful than hoped in terms of enhancing the status of targeted species and often overlooks important constraints on ecologically effective restoration. We identify three priority food web-related issues that potentially impede successful river restoration: uncertainty about habitat carrying capacity, proliferation of chemicals and contaminants, and emergence of hybrid food webs containing a mixture of native and invasive species. Additionally, there is the need to place these food web considerations in a broad temporal and spatial framework by understanding the consequences of altered nutrient, organic matter (energy), water, and thermal sources and flows, reconnecting critical habitats and their food webs, and restoring for changing environments. As an illustration, we discuss how the Columbia River Basin, site of one of the largest aquatic/riparian restoration programs in the United States, would benefit from implementing a food web perspective. A food web perspective for the Columbia River would complement ongoing approaches and enhance the ability to meet the vision and legal obligations of the US Endangered Species Act, the Northwest Power Act (Fish and Wildlife Program), and federal treaties with Northwest Indian Tribes while meeting fundamental needs for improved river management. PMID:23197837

Naiman, Robert J.; Alldredge, J. Richard; Beauchamp, David A.; Bisson, Peter A.; Congleton, James; Henny, Charles J.; Huntly, Nancy; Lamberson, Roland; Levings, Colin; Merrill, Erik N.; Pearcy, William G.; Rieman, Bruce E.; Ruggerone, Gregory T.; Scarnecchia, Dennis; Smouse, Peter E.; Wood, Chris C.

2012-01-01

180

Estuarine Microbial Food Web Patterns in a Lake Erie Coastal P.J. Lavrentyev1  

E-print Network

Estuarine Microbial Food Web Patterns in a Lake Erie Coastal Wetland P.J. Lavrentyev1 , M.J. Mc protists were examined relative to microbial food web dynamics (growth, grazing, and nitrogen cycling rates pattern. Large light/dark NH4 + uptake differences were observed in the hypereutrophic OWC interior

Jochem, Frank J.

181

BRIEF COMMUNICATIONS ARISING NATURE|Vol 435|16 June 2005 FOOD-WEB TOPOLOGY  

E-print Network

BRIEF COMMUNICATIONS ARISING NATURE|Vol 435|16 June 2005 E4 FOOD-WEB TOPOLOGY Garlaschelliet al curves shown in their Fig. 1a for three-level food webs define a `narrow' region1 , several power laws that the observed values of (including that for the C0 versus A0 curve) are due merely to the number of trophic

Caldarelli, Guido

182

Trophic transfer of metals along freshwater food webs: Evidence of cadmium biomagnification in nature  

Microsoft Academic Search

We conducted a study with cadmium (Cd) and copper (Cu) in the delta of San Francisco Bay, using nitrogen and carbon stable isotopes to identify trophic position and food web structure. Cadmium is progressively enriched among trophic levels in discrete epiphyte-based food webs composed of macrophyte-dwelling invertebrates (the first link being epiphytic algae) and fishes (the first link being gobies).

Marie-Noële Croteau; Samuel N. Luoma; A. Robin Stewart

2005-01-01

183

TROPHIC LEVELS AND TROPHIC TANGLES: THE PREVALENCE OF OMNIVORY IN REAL FOOD WEBS  

Microsoft Academic Search

The concept of trophic levels is one of the oldest in ecology and informs our understanding of energy flow and top-down control within food webs, but it has been criticized for ignoring omnivory. We tested whether trophic levels were apparent in 58 real food webs in four habitat types by examining patterns of trophic position. A large proportion of taxa

Ross M. Thompson; Martin Hemberg; Brian M. Starzomski; Jonathan B. Shurin

2007-01-01

184

Carp Exclusion, Food-web Interactions, and the Restoration of Cootes Paradise Marsh  

E-print Network

Carp Exclusion, Food-web Interactions, and the Restoration of Cootes Paradise Marsh Vanessa L percent, respectively, following carp exclusion. However, responses by plants and other trophic levels dominated state. INDEX WORDS: Carp exclusion, coastal wetlands, restoration, food web. J. Great Lakes Res

McMaster University

185

Are Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads?  

E-print Network

of the detrital food web in shaded bromeliads but accounted for up to 30 percent of the living microbial carbonAre Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads? Olivier Brouard1 , Anne and with regard to the structure of other aquatic microbial communities held in the tanks. Algae were retrieved

Boyer, Edmond

186

Indirect effects of zebra mussels (Dreissena polymorpha) on the planktonic food web  

E-print Network

Indirect effects of zebra mussels (Dreissena polymorpha) on the planktonic food web Erik G. Noonburg, Brian J. Shuter, and Peter A. Abrams Abstract: The exotic zebra mussel (Dreissena polymorpha) has the abundance of their phytoplankton prey. We analyze food web models to test hypothesized mechanisms

Noonburg, Erik

187

Comparative food web structure of larval macrolepidoptera and their parasitoids on two riparian tree species  

Microsoft Academic Search

Single species or groups of species can be subjected to differing levels of parasitism on different plants. Previous studies\\u000a have reported that parasitism of larval macrolepidoptera in an assemblage on box elder (Acer negundo L.) was significantly greater than on black willow [Salix nigra (Marsh)]. In this study, quantitative food webs, parasitoid overlap diagrams and other food web attributes were

Pedro Barbosa; Astrid Caldas; H. Charles J. Godfray

2007-01-01

188

EMERGENCE OF LOCAL CONNECTION PATTERNS AND OTHER FOOD WEB TRAITS: AN EVOLUTIONARY MODEL  

Microsoft Academic Search

Some general properties have been found in food web descriptions. One of the most relevant structural traits is the presence of characteris- tic local connection patterns. Here we address the question of whether these properties can emerge in a simple evolutionary model based on predator-prey dynamics. Ecosystems ina steady state arise in our general network model of food web evolution

Mariana Ben ´; Carlos Espinosa-Soto

189

Biodiversity, ecosystem functioning and food webs in fresh waters: assembling the jigsaw puzzle  

Microsoft Academic Search

SUMMARY 1. Dramatic advances have been made recently in the study of biodiversity-ecosystem functioning (B-EF) relations and food web ecology. These fields are now starting to converge, and this fusion has the potential to improve our understanding of how environmental stressors modulate ecosystem processes and the supply of 'goods and services'. 2. Food web structure and dynamics can exert particularly

GUY W OODWARD

2009-01-01

190

Form and function: Metabolic footprints of nematodes in the soil food web  

Microsoft Academic Search

Metabolic footprints provide metrics for the magnitudes of ecosystem functions and services provided by component organisms of the soil food web. Nematodes occupy various trophic roles and perform important functions within the web. They are convenient indicators of similar functions performed by other organisms in the web and are well-documented indicators of ecosystem condition. The generally vermiform shapes of nematodes,

Howard Ferris

2010-01-01

191

Biological vs. physical mixing effects on benthic food web dynamics.  

PubMed

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 (13)C 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 (??(13)C) of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13)C 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 TO(13)C 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. PMID:21455308

Braeckman, Ulrike; Provoost, Pieter; Moens, Tom; Soetaert, Karline; Middelburg, Jack J; Vincx, Magda; Vanaverbeke, Jan

2011-01-01

192

Facilitating Scientific Collaboration and Education with Easy Access Web Maps Using the AGAP Antarctic Geophysical Data  

NASA Astrophysics Data System (ADS)

Science and science education benefit from easy access to data yet often geophysical data sets are large, complex and difficult to share. The difficulty in sharing data and imagery easily inhibits both collaboration and the use of real data in educational applications. The dissemination of data products through web maps serves a very efficient and user-friendly method for students, the public and the science community to gain insights and understanding from data. Few research groups provide direct access to their data, let alone map-based visualizations. By building upon current GIS infrastructure with web mapping technologies, like ArcGIS Server, scientific groups, institutions and agencies can enhance the value of their GIS investments. The advantages of web maps to serve data products are many; existing web-mapping technology allows complex GIS analysis to be shared across the Internet, and can be easily scaled from a few users to millions. This poster highlights the features of an interactive web map developed at the Polar Geophysics Group at the Lamont-Doherty Earth Observatory of Columbia University that provides a visual representation of, and access to, data products that resulted from the group's recently concluded AGAP project (http://pgg.ldeo.columbia.edu). The AGAP project collected more than 120,000 line km of new aerogeophysical data using two Twin Otter aircrafts. Data included ice penetrating radar, magnetometer, gravimeter and laser altimeter measurements. The web map is based upon ArcGIS Viewer for Flex, which is a configurable client application built on the ArcGIS API for Flex that works seamlessly with ArcGIS Server 10. The application can serve a variety of raster and vector file formats through the Data Interoperability for Server, which eliminates data sharing barriers across numerous file formats. The ability of the application to serve large datasets is only hindered by the availability of appropriate hardware. ArcGIS is a proprietary product, but there are a few data portals in the earth sciences that have a map interface using open access products such as MapServer and OpenLayers, the most notable being the NASA IceBridge Data Portal. Indeed, with the widespread availability of web mapping technology, the scientific community should advance towards this direction when disseminating their data.

Abdi, A.

2012-12-01

193

Global Multi-Level Analysis of the 'Scientific Food Web'  

PubMed Central

We introduce a network-based index analyzing excess scientific production and consumption to perform a comprehensive global analysis of scholarly knowledge production and diffusion on the level of continents, countries, and cities. Compared to measures of scientific production and consumption such as number of publications or citation rates, our network-based citation analysis offers a more differentiated picture of the ‘ecosystem of science’. Quantifying knowledge flows between 2000 and 2009, we identify global sources and sinks of knowledge production. Our knowledge flow index reveals, where ideas are born and consumed, thereby defining a global ‘scientific food web’. While Asia is quickly catching up in terms of publications and citation rates, we find that its dependence on knowledge consumption has further increased. PMID:23378902

Mazloumian, Amin; Helbing, Dirk; Lozano, Sergi; Light, Robert P.; Borner, Katy

2013-01-01

194

Bioaccumulation of organochlorines in the Arctic marine food web  

SciTech Connect

Five classes of organochlorine (OC) compounds (hexachlorocyclohexane (HCB and HCHs), cyclodienes, isomers of DDT and its metabolites and congeners of polychlorinated biphenyls (PCBs) and toxaphene (CHBs)) have been detected in under-ice epontic particulate matter and tissue samples of marine biota from lower trophic levels of the Arctic Ocean at sites in Barrow Strait within the Canadian archipelago (75{degree}N), coastal (79{degree}N) and central Arctic basin (85{degree}N) locations. HCBs, PCBs, isomers of DDT and DDE, chlordane, dieldrin, alpha-endosulphan, HCB and {alpha}-HCH were present in quantifiable amounts in all samples. {beta}- and {gamma}-HCH and the cyclodienes aldrin, endrin, heptachlor, heptachlor epoxide, methoxychlor and mirex were detected but could not be quantified. All OCs measured in biota were also present in the Arctic atmosphere, particulate and dissolved fractions of snow, ice melt water and seawater, Small bodied marine organisms such as zooplankton and amphipods which are short-lived have a lower lipid content for storage of OCs than larger animals such as fish and mammals. Biomagnification factors calculated from presumed predator-prey links in the marine food web varied over two orders of magnitude for different OCs. Ratios for epontic particulates and plankton (< 10) were generally lower than values for trophic links between amphipods and published values for arctic marine fish and mammals (10--100). PCBs, DDT and chlordanes are biomagnified in the Arctic marine food web to a far greater degree than more abundant OC compounds such as HCHs and HCB that have a higher water solubility.

Hargrave, B.; Phillips, G.; Vass, W.; Harding, G. [Department of Fisheries and Oceans, Dartmouth, Nova Scotia (Canada). Bedford Inst. of Oceanography; Welch, H. [Department of Fisheries and Oceans, Winnipeg, Manitoba (Canada). Freshwater Inst.

1995-12-31

195

Marine subsidies have multiple effects on coastal food webs.  

PubMed

The effect of resource subsidies on recipient food webs has received much recent attention. The purpose of this study was to measure the effects of significant seasonal seaweed deposition events, caused by hurricanes and other storms, on species inhabiting subtropical islands. The seaweed represents a pulsed resource subsidy that is consumed by amphipods and flies, which are eaten by lizards and predatory arthropods, which in turn consume terrestrial herbivores. Additionally, seaweed decomposes directly into the soil under plants. We added seaweed to six shoreline plots and removed seaweed from six other plots for three months; all plots were repeatedly monitored for 12 months after the initial manipulation. Lizard density (Anolis sagrei) responded rapidly, and the overall average was 63% higher in subsidized than in removal plots. Stable-isotope analysis revealed a shift in lizard diet composition toward more marine-based prey in subsidized plots. Leaf damage was 70% higher in subsidized than in removal plots after eight months, but subsequent damage was about the same in the two treatments. Foliage growth rate was 70% higher in subsidized plots after 12 months. Results of a complementary study on the relationship between natural variation in marine subsidies and island food web components were consistent with the experimental results. We suggest two causal pathways for the effects of marine subsidies on terrestrial plants: (1) the "fertilization effect" in which seaweed adds nutrients to plants, increasing their growth rate, and (2) the "predator diet shift effect" in which lizards shift from eating local prey (including terrestrial herbivores) to eating mostly marine detritivores. PMID:20503874

Spiller, David A; Piovia-Scorr, Jonah; Wright, Amber N; Yang, Louie H; Takimoto, Gaku; Schoener, Thomas W; Iwata, Tomoya

2010-05-01

196

Food webs: a ladder for picking strawberries or a practical tool for practical problems?  

PubMed Central

While food webs have provided a rich vein of research material over the last 50 years, they have largely been the subject matter of the pure ecologist working in natural habitats. While there are some notable exceptions to this trend, there are, as I explain in this paper, many applied questions that could be answered using a food web approach. The paper is divided into two halves. The first half provides a brief review of six areas where food webs have begun to be used as an applied tool: restoration ecology, alien species, biological control, conservation ecology, habitat management and global warming. The second half outlines five areas in which a food web approach could prove very rewarding: urban ecology, agroecology, habitat fragmentation, cross-habitat food webs and ecosystem services. PMID:19451120

Memmott, Jane

2009-01-01

197

Food webs: a ladder for picking strawberries or a practical tool for practical problems?  

PubMed

While food webs have provided a rich vein of research material over the last 50 years, they have largely been the subject matter of the pure ecologist working in natural habitats. While there are some notable exceptions to this trend, there are, as I explain in this paper, many applied questions that could be answered using a food web approach. The paper is divided into two halves. The first half provides a brief review of six areas where food webs have begun to be used as an applied tool: restoration ecology, alien species, biological control, conservation ecology, habitat management and global warming. The second half outlines five areas in which a food web approach could prove very rewarding: urban ecology, agroecology, habitat fragmentation, cross-habitat food webs and ecosystem services. PMID:19451120

Memmott, Jane

2009-06-27

198

Parasites as prey in aquatic food webs: implications for predator infection and parasite transmission  

USGS Publications Warehouse

While the recent inclusion of parasites into food-web studies has highlighted the role of parasites as consumers, there is accumulating evidence that parasites can also serve as prey for predators. Here we investigated empirical patterns of predation on parasites and their relationships with parasite transmission in eight topological food webs representing marine and freshwater ecosystems. Within each food web, we examined links in the typical predator–prey sub web as well as the predator–parasite sub web, i.e. the quadrant of the food web indicating which predators eat parasites. Most predator– parasite links represented ‘concomitant predation’ (consumption and death of a parasite along with the prey/host; 58–72%), followed by ‘trophic transmission’ (predator feeds on infected prey and becomes infected; 8–32%) and predation on free-living parasite life-cycle stages (4–30%). Parasite life-cycle stages had, on average, between 4.2 and 14.2 predators. Among the food webs, as predator richness increased, the number of links exploited by trophically transmitted parasites increased at about the same rate as did the number of links where these stages serve as prey. On the whole, our analyses suggest that predation on parasites has important consequences for both predators and parasites, and food web structure. Because our analysis is solely based on topological webs, determining the strength of these interactions is a promising avenue for future research.

Thieltges, David W.; Amundsen, Per-Arne; Hechinger, Ryan F.; Johnson, Pieter T. J.; Lafferty, Levin D.; Mouritsen, Kim N.; Preston, Daniel L.; Reise, Karsten; Zander, C. Dieter; Poulin, Robert

2013-01-01

199

Food and Beverage Brands That Market to Children and Adolescents on the Internet: A Content Analysis of Branded Web Sites  

Microsoft Academic Search

ObjectiveTo identify food and beverage brand Web sites featuring designated children's areas, assess marketing techniques present on those industry Web sites, and determine nutritional quality of branded food items marketed to children.

Anna E. Henry; Mary Story

2009-01-01

200

Food web structure of sandy beaches: Temporal and spatial variation using stable isotope analysis  

NASA Astrophysics Data System (ADS)

The food web structure of two sandy beach ecosystems with contrasting morphodynamics (dissipative vs. reflective) was examined using stable carbon (? 13C) and nitrogen (? 15N) isotope analysis. Organic matter sources (POM: particulate organic matter; SOM: sediment organic matter) and consumers (zooplankton, benthic invertebrates and fishes) were sampled seasonally in both sandy beaches. Food webs significantly differed between beaches: even though both webs were mainly supported by POM, depleted ? 13C and ? 15N values for food sources and consumers were found in the dissipative system (following the reverse pattern in ? 13C values for consumers) for all the four seasons. Primary consumers (zooplankton and benthic invertebrates) use different organic matter sources on each beach and these differences are propagated up in the food web. The higher productivity found in the dissipative beach provided a significant amount of food for primary consumers, notably suspension feeders. Thus, the dissipative beach supported a more complex food web with more trophic links and a higher number of prey and top predators than the reflective beach. Morphodynamic factors could explain the contrasting differences in food web structure. The high degree of retention (nutrients and phytoplankton) recorded for the surf zone of the dissipative beach would result in the renewed accumulation of POM that sustains a more diverse and richer fauna than the reflective beach. Further studies directed to assess connections between the macroscopic food web, the surf-zone microbial loop and the interstitial compartment will provide a deeper understanding on the functioning of sandy beach ecosystems.

Bergamino, Leandro; Lercari, Diego; Defeo, Omar

2011-03-01

201

Food Web Architecture and Basal Resources Interact to Determine Biomass and Stoichiometric Cascades along a Benthic Food Web  

PubMed Central

Understanding the effects of predators and resources on primary producers has been a major focus of interest in ecology. Within this context, the trophic cascade concept especially concerning the pelagic zone of lakes has been the focus of the majority of these studies. However, littoral food webs could be especially interesting because base trophic levels may be strongly regulated by consumers and prone to be light limited. In this study, the availability of nutrients and light and the presence of an omnivorous fish (Hyphessobrycon bifasciatus) were manipulated in enclosures placed in a humic coastal lagoon (Cabiúnas Lagoon, Macaé – RJ) to evaluate the individual and interactive effects of resource availability (nutrients and light) and food web configuration on the biomass and stoichiometry of periphyton and benthic grazers. Our findings suggest that light and nutrients interact to determine periphyton biomass and stoichiometry, which propagates to the consumer level. We observed a positive effect of the availability of nutrients on periphytic biomass and grazers' biomass, as well as a reduction of periphytic C?N?P ratios and an increase of grazers' N and P content. Low light availability constrained the propagation of nutrient effects on periphyton biomass and induced higher periphytic C?N?P ratios. The effects of fish presence strongly interacted with resource availability. In general, a positive effect of fish presence was observed for the total biomass of periphyton and grazer's biomass, especially with high resource availability, but the opposite was found for periphytic autotrophic biomass. Fish also had a significant effect on periphyton stoichiometry, but no effect was observed on grazers' stoichiometric ratios. In summary, we observed that the indirect effect of fish predation on periphyton biomass might be dependent on multiple resources and periphyton nutrient stoichiometric variation can affect consumers' stoichiometry. PMID:21789234

Guariento, Rafael D.; Carneiro, Luciana S.; Caliman, Adriano; Leal, Joao J. F.; Bozelli, Reinaldo L.; Esteves, Francisco A.

2011-01-01

202

Snow Web 2.0: The Next Generation of Antarctic Meteorological Monitoring Systems?  

NASA Astrophysics Data System (ADS)

Adequate in-situ observation of the Antarctic lower atmosphere has proved problematic, due to a combination of the inhospitable nature and extent of the continent. Traditional weather stations are expensive, subject to extreme weather for long periods and are often isolated, and as such are prone to failure and logistically difficult to repair. We have developed the first generation of an extended system of atmospheric sensors, each costing a fraction of the price of a traditional weather station. The system is capable of performing all of the monitoring tasks of a traditional station, but has built-in redundancy over the traditional approach because many units can be deployed in a relatively small area for similar expenditure as one large weather station. Furthermore, each unit is equipped with wireless networking capabilities and so is able to share information with those units in its direct vicinity. This allows for the ferrying of collected information to a manned observation station and hence the ability to monitor data in real-time. The distributed nature of the data collected can then be used as a stand-alone product to investigate small-scale weather and climate phenomena or integrated into larger studies and be used to monitor wide regions. GPS hardware installed on each unit also allows for high-resolution glacier or ice-shelf tracking. As a testing and data gathering study, eighteen such weather stations were deployed in the vicinity of Scott Base, Ross Island, Antarctica over the 2011/12 summer season. This presentation reports on findings from this field study, and discusses possibilities for the future.

Coggins, J.; McDonald, A.; Plank, G.; Pannell, M.; Ward, R.; Parsons, S.

2012-04-01

203

Effects of cover crop quality and quantity on nematode-based soil food webs and nutrient cycling  

Microsoft Academic Search

Soil food webs cycle nutrients and regulate parasites and pathogens, services essential for both agricultural productivity and ecosystem health. Nematodes provide useful indicators of soil food web dynamics. This study was conducted to determine if nematode soil food web indicators and crop yield can be enhanced by combinations of cover crops in a conservation tillage system. The effects of three

S. Tianna DuPont; Howard Ferris; Mark Van Horn

2009-01-01

204

Plant diversity effects on soil food webs are stronger than those of elevated CO2 and N deposition  

E-print Network

Plant diversity effects on soil food webs are stronger than those of elevated CO2 and N deposition examined the responses of soil food webs (soil microorganisms, nematodes, microarthropods) to 13-y was a strong driver of the structure and functioning of soil food webs through several bottom-up (resource

Minnesota, University of

205

Global change belowground: impacts of elevated CO2, nitrogen, and summer drought on soil food webs and  

E-print Network

Global change belowground: impacts of elevated CO2, nitrogen, and summer drought on soil food webs this gap by examining the responses of soil food webs and biodiversity to enrichment of CO2, elevated N availability resulted in modest altera- tions of soil biotic food webs and biodiversity via several mechanisms

Minnesota, University of

206

Modelling the role of highly unsaturated fatty acids in planktonic food web processes: Sensitivity analysis and examination of contemporary hypotheses  

E-print Network

food web models typically treat the constituent trophic levels as static elements interacting with oneModelling the role of highly unsaturated fatty acids in planktonic food web processes: Sensitivity evolutionary responses in said elements. The incorporation of organismal response in food web models holds

Arhonditsis, George B.

207

Subsidy from the detrital food web, but not microhabitat complexity, affects the role of generalist predators in an aboveground herbivore  

E-print Network

Subsidy from the detrital food web, but not microhabitat complexity, affects the role of generalist predators in an aboveground herbivore food web Klaus Birkhofer, David H. Wise and Stefan Scheu K. Birkhofer affect predation rates on herbivores in the aboveground food web. We tested this hypothesis

Illinois at Chicago, University of

208

Deep-Sea Research I 51 (2004) 12451274 Carbon fluxes through food webs of the eastern equatorial  

E-print Network

Deep-Sea Research I 51 (2004) 1245­1274 Carbon fluxes through food webs of the eastern equatorial inverse and network analyses to examine food web interactions at 0 , 140 W during EqPac time approach allowed us to trace the pathway of fixed carbon through a representative food web

Jackson, George

209

Hydrology and grazing jointly control a large-river food web.  

PubMed

Inputs of fresh water and grazing both can control aquatic food webs, but little is known about the relative strengths of and interactions between these controls. We use long-term data on the food web of the freshwater Hudson River estuary to investigate the importance of, and interactions between, inputs of fresh water and grazing by the invasive zebra mussel (Dreissena polymorpha). Both freshwater inputs and zebra mussel grazing have strong, pervasive effects on the Hudson River food web. High flow tended to reduce population size in most parts of the food web. High grazing also reduced populations in the planktonic food web, but increased populations in the littoral food web, probably as a result of increases in water clarity. The influences of flow and zebra mussel grazing were roughly equal (i.e., within a factor of 2) for many variables over the period of our study. Zebra mussel grazing made phytoplankton less sensitive to freshwater inputs, but water clarity and the littoral food web more sensitive to freshwater inputs, showing that interactions between these two controlling factors can be strong and varied. PMID:18376541

Strayer, David L; Pace, Michael L; Caraco, Nina F; Cole, Jonathan J; Findlay, Stuart E G

2008-01-01

210

Fluorinated organic compounds in an eastern Arctic marine food web.  

PubMed

An eastern Arctic marine food web was analyzed for perfluorooctanesulfonate (PFOS, C8F17SO3-), perfluorooctanoate (PFOA, C7F15COO-), perfluorooctane sulfonamide (PFOSA, C8F17SO2NH2), and N-ethylperfluorooctane sulfonamide (N-EtPFOSA, C8F17SO2NHCH2CH3) to examine the extent of bioaccumulation. PFOS was detected in all species analyzed, and mean concentrations ranged from 0.28 +/- 0.09 ng/g (arithmetic mean +/- 1 standard error, wet wt, whole body) in clams (Mya truncata) to 20.2 +/- 3.9 ng/g (wet wt, liver) in glaucous gulls (Larus hyperboreus). PFOA was detected in approximately 40% of the samples analyzed at concentrations generally smaller than those found for PFOS; the greatest concentrations were observed in zooplankton (2.6 +/- 0.3 ng/g, wet wt). N-EtPFOSA was detected in all species except redfish with mean concentrations ranging from 0.39 +/- 0.07 ng/g (wet wt) in mixed zooplankton to 92.8 +/- 41.9 ng/g (wet wt) in Arctic cod (Boreogadus saida). This is the first report of N-EtPFOSA in Arctic biota. PFOSA was only detected in livers of beluga (Delphinapterus leucas) (20.9 +/- 7.9 ng/g, wet wt) and narwhal (Monodon monoceros) (6.2 +/- 2.3 ng/g, wet wt), suggesting that N-EtPFOSA and other PFOSA-type precursors are likely present but are being biotransformed to PFOSA. A positive linear relationship was found between PFOS concentrations (wet wt) and trophic level (TL), based on delta15N values, (r2 = 0.51, p < 0.0001) resulting in a trophic magnification factor of 3.1. TL-corrected biomagnification factor estimates for PFOS ranged from 0.4 to 9. Both results indicate that PFOS biomagnifies in the Arctic marine food web when liver concentrations of PFOS are used for seabirds and marine mammals. However, transformation of N-EtPFOSA and PFOSA and potential other perfluorinated compounds to PFOS may contribute to PFOS levels in marine mammals and may inflate estimated biomagnification values. None of the other fluorinated compounds (N-EtPFOSA, PFOSA, and PFOA) were found to have a significant relationship with TL, but BMF(TL) values of these compounds were often >1, suggesting potential for these compounds to biomagnify. The presence of perfluorinated compounds in seabirds and mammals provides evidence that trophic transfer is an important exposure route of these chemicals to Arctic biota. PMID:15669302

Tomy, Gregg T; Budakowski, Wes; Halldorson, Thor; Helm, Paul A; Stern, Gary A; Friesen, Ken; Pepper, Karen; Tittlemier, Sheryl A; Fisk, Aaron T

2004-12-15

211

Dispersed oil disrupts microbial pathways in pelagic food webs.  

PubMed

Most of the studies of microbial processes in response to the Deepwater Horizon oil spill focused on the deep water plume, and not on the surface communities. The effects of the crude oil and the application of dispersants on the coastal microbial food web in the northern Gulf of Mexico have not been well characterized even though these regions support much of the fisheries production in the Gulf. A mesocosm experiment was carried out to determine how the microbial community off the coast of Alabama may have responded to the influx of surface oil and dispersants. While the addition of glucose or oil alone resulted in an increase in the biomass of ciliates, suggesting transfer of carbon to higher trophic levels was likely; a different effect was seen in the presence of dispersant. The addition of dispersant or dispersed oil resulted in an increase in the biomass of heterotrophic prokaryotes, but a significant inhibition of ciliates, suggesting a reduction in grazing and decrease in transfer of carbon to higher trophic levels. Similar patterns were observed in two separate experiments with different starting nutrient regimes and microbial communities suggesting that the addition of dispersant and dispersed oil to the northern Gulf of Mexico waters in 2010 may have reduced the flow of carbon to higher trophic levels, leading to a decrease in the production of zooplankton and fish on the Alabama shelf. PMID:22860136

Ortmann, Alice C; Anders, Jennifer; Shelton, Naomi; Gong, Limin; Moss, Anthony G; Condon, Robert H

2012-01-01

212

javaFoodWeb: Bridging the gap between Excel and Niches  

NSDL National Science Digital Library

javaFoodWeb is a portable application that will take data from an Excel spreadsheet showing Predators (consumers) and the Prey (resources) which they depend upon and allow students to visualize the competition spaces (niches) that they define.

Vince Steif (University of Wisconsin-- Madison;)

2005-06-11

213

Indirect effects of metal contamination on energetics of yellow perch (Perca flavescens) resulting from food web  

E-print Network

Indirect effects of metal contamination on energetics of yellow perch (Perca flavescens) resulting of Biology, Montreal, Quebec, Canada SUMMARY 1. Benthic invertebrate community composition and yellow perch, lake food web, metal contamination, Perca flavescens, stunting, Sudbury, yellow perch Introduction

Rasmussen, Joseph

214

E.2. Electronic Appendix -Food Web Elements of the Fraser River Upper River (above rkm 210)  

E-print Network

are brook trout (stoc al. 1983, Rogers et al. 1988, Levings and Lauzier 1991). Rainbow trout and northern pikeminnow). Stressors: Water quality and habitat conditions have changed food webs in specific locations in the upper

215

IDENTIFYING LOCAL SCALE FOOD WEB VARIATION USING N ISOTOPES IN A CENTRAL INDIANA  

E-print Network

- turing food webs can serve as a tool for aquatic conservation. Previous studies have indicated that alter habitats, and shift functional organization (Poff & Ward 1990; Poff & Allan 1995). Impound- ment of lotic

Pyron, Mark

216

Rapid food web recovery in response to removal of an introduced apex predator  

E-print Network

a native apex predator (lake trout (Salvelinus namaycush)) were used to measure food web changes following d'un prédateur du sommet du réseau alimentaire (le touladi, Salvelinus namaycush) nous servent à

Kraft, Clifford E.

217

Marine carbon and nitrogen in southeastern Alaska stream food webs: evidence from artificial  

E-print Network

Marine carbon and nitrogen in southeastern Alaska stream food webs: evidence from artificial in biota from artificial and natural streams. Biofilm, aquatic macroinvertebrates (detritivores, shredders consumption of salmon material by macroinvertebrates and fish and uptake of mineralized MDN by biofilm

Wipfli, Mark S.

218

Vertical heterogeneity of a forest floor invertebrate food web as indicated by stable-isotope analysis  

Microsoft Academic Search

Diverse populations of invertebrates constitute the food web in detritus layers of a forest floor. Heterogeneity in trophic\\u000a interactions within such a species-rich community food web may affect the dynamic properties of biological communities such\\u000a as stability. To examine the vertical heterogeneity in trophic interactions among invertebrates in litter and humus layers,\\u000a we studied differences in species composition and variations

Yutaka Okuzaki; Ichiro Tayasu; Noboru Okuda; Teiji Sota

2009-01-01

219

UV Effects on Aquatic Microbial Food Webs in Northern Lakes and Rivers  

Microsoft Academic Search

\\u000a Lakes, ponds and rivers occur throughout the arctic and subarctic landscape and provide the habitat for a variety of aquatic\\u000a life including zooplankton, insects, fish and birds. The base of the food webs supporting these animal populations is still\\u000a poorly understood, but at many sites examined to date the biomass and energy flow in the lower food web is mostly

W. F. Vincent; C. Belzile

220

Abundance, diversity and connectance of soil food web channels along environmental gradients in an agricultural landscape  

Microsoft Academic Search

Soil food webs respond to anthropogenic and natural environmental variables and gradients. We studied abundance, connectance (a measure of the trophic interactions within each channel), and diversity in three different channels of the soil food web, each comprised of a resource-consumer pair: the microbivore channel (microbes and their nematode grazers), the plant–herbivore channel (plants and plant-feeding nematodes), and the predator–prey

Sara Sánchez-Moreno; Howard Ferris; Anna Young-Mathews; Steven W. Culman; Louise E. Jackson

2011-01-01

221

Interplay of omnivory, energy channels and C availability in a microbial-based soil food web  

Microsoft Academic Search

To study the effects of omnivory on the structure and function of soil food webs and on the control of trophic-level biomasses\\u000a in soil, two food webs were established in microcosms. The first one contained fungi, bacteria, a fungivorous nematode (Aphelenchoides saprophilus) and a bacterivorous nematode (Caenorhabditis elegans), and the second one fungi, bacteria, the fungivore and an omnivorous nematode

J. Mikola; H. Setälä

1999-01-01

222

Assessing Ecosystem Effects of Reservoir Operations Using Food Web–Energy Transfer and Water Quality Models  

Microsoft Academic Search

We investigated the effects on the reservoir food web of a new temperature control device (TCD) on the dam at Shasta Lake,\\u000a California. We followed a linked modeling approach that used a specialized reservoir water quality model to forecast operation-induced\\u000a changes in phytoplankton production. A food web–energy transfer model was also applied to propagate predicted changes in phytoplankton\\u000a up through

Laurel Saito; Brett M. Johnson; John Bartholow; R. Blair Hanna

2001-01-01

223

Coupled energy pathways and the resilience of size-structured food webs  

Microsoft Academic Search

Size-based food-web models, which focus on body size rather than species identity, capture the generalist and transient feeding\\u000a interactions in most marine ecosystems and are well-supported by data. Here, we develop a size-based model that incorporates\\u000a dynamic interactions between marine benthic (detritus-based) and pelagic (primary producer based) pathways to investigate\\u000a how the coupling of these pathways affects food web stability

Julia L. Blanchard; Richard Law; Matthew D. Castle; Simon Jennings

224

Predator hunting mode influences patterns of prey use from grazing and epigeic food webs.  

PubMed

Multichannel omnivory by generalist predators, especially the use of both grazing and epigeic prey, has the potential to increase predator abundance and decrease herbivore populations. However, predator use of the epigeic web (soil surface detritus/microbe/algae consumers) varies considerably for reasons that are poorly understood. We therefore used a stable isotope approach to determine whether prey availability and predator hunting style (active hunting vs. passive web-building) impacted the degree of multichannel omnivory by the two most abundant predators on an intertidal salt marsh, both spiders. We found that carbon isotopic values of herbivores remained constant during the growing season, while values for epigeic feeders became dramatically more enriched such that values for the two webs converged in August. Carbon isotopic values for both spider species remained midway between the two webs as values for epigeic feeders shifted, indicating substantial use of prey from both food webs by both spider species. As the season progressed, prey abundance in the grazing food web increased while prey abundance in the epigeic web remained constant or declined. In response, prey consumption by the web-building spider shifted toward the grazing web to a much greater extent than did consumption by the hunting spider, possibly because passive web-capture is more responsive to changes in prey availability. Although both generalist predator species engaged in multichannel omnivory, hunting mode influenced the extent to which these predators used prey from the grazing and epigeic food webs, and could thereby influence the strength of trophic cascades in both food webs. PMID:22926724

Wimp, Gina M; Murphy, Shannon M; Lewis, Danny; Douglas, Margaret R; Ambikapathi, Ramya; Van-Tull, Lie'Ann; Gratton, Claudio; Denno, Robert F

2013-02-01

225

The effects of riparian alterations on stream food webs Kevin M. Kingsland, Beloit College  

E-print Network

cranberry bogs is worth the cost and effort. INTRODUCTION Human alterations of ecosystems alter the physical webs, and by changing the plants in an ecosystem humans change the species composition of otherThe effects of riparian alterations on stream food webs Kevin M. Kingsland, Beloit College

Vallino, Joseph J.

226

Inferring chemical effects on carbon flows in aquatic food webs: methodology and case study.  

PubMed

The majority of ecotoxicological enclosure experiments monitor species abundances at different chemical concentrations. Here, we present a new modelling approach that estimates changes in food web flows from such data and show that population- and food web level effects are revealed that are not apparent from abundance data alone. For the case of cypermethrin in freshwater enclosures, photosynthesis and excretion (d(-1)) of phytoplankton at 3.643 microg L(-1) cypermethrin were 30% lower and 100% higher than in the control, respectively. The ingestion rate of mesozooplankton (d(-1)) was 6 times higher in the treated enclosures than in the control as food concentration increased with insecticide exposure. With increasing cypermethrin concentrations, nanoflagellates progressively relied on phytoplankton as their main food source, which rendered the food web less stable. We conclude that this tool has excellent potential to analyse the wealth of enclosure data as it only needs species abundance and general constraints. PMID:19954869

De Laender, Frederik; Soetaert, K; Middelburg, J J

2010-05-01

227

Road salts as environmental constraints in urban pond food webs.  

PubMed

Freshwater salinization is an emerging environmental filter in urban aquatic ecosystems that receive chloride road salt runoff from vast expanses of impervious surface cover. Our study was designed to evaluate the effects of chloride contamination on urban stormwater pond food webs through changes in zooplankton community composition as well as density and biomass of primary producers and consumers. From May - July 2009, we employed a 2×2×2 full-factorial design to manipulate chloride concentration (low?=?177 mg L(-1) Cl(-/)high?=?1067 mg L(-1) Cl(-)), gray treefrog (Hyla versicolor) tadpoles (presence/absence) and source of stormwater pond algae and zooplankton inoculum (low conductance/high conductance urban ponds) in 40, 600-L mesocosms. Road salt did serve as a constraint on zooplankton community structure, driving community divergence between the low and high chloride treatments. Phytoplankton biomass (chlorophyll [a] µg L(-1)) in the mesocosms was significantly greater for the high conductance inoculum (P<0.001) and in the high chloride treatment (P?=?0.046), whereas periphyton biomass was significantly lower in the high chloride treatment (P?=?0.049). Gray treefrog tadpole time to metamorphosis did not vary significantly between treatments. However, mass at metamorphosis was greater among tadpoles that experienced a faster than average time to metamorphosis and exposure to high chloride concentrations (P?=?0.039). Our results indicate differential susceptibility to chloride salts among algal resources and zooplankton taxa, and further suggest that road salts can act as a significant environmental constraint on urban stormwater pond communities. PMID:24587259

Van Meter, Robin J; Swan, Christopher M

2014-01-01

228

Biogeochemistry and the structure of tropical brown food webs.  

PubMed

Litter invertebrates are notoriously patchy at small scales. Here we show that the abundance of 10 litter taxa also varies 100-fold at landscape and regional scales across 26 forest stands in Peru and Panama. We contrast three hypotheses that link gradients of abundance to ecosystem biogeochemistry. Of 14 factors considered (12 chemical elements, plus fiber and litter depth), four best predicted the abundance of litter invertebrates. In the Secondary Productivity Hypothesis, phosphorus limits abundance via the conversion of detritus to microbial biomass. Two of four microbivore taxa, collembola and isopods, increased with the percentage of P (%P) of decomposing litter. However, percentage of S (correlated with %P) best predicted the abundance of collembola, oribatids, and diplopods (r2 = 0.38, 0.33, 0.21, respectively). In the Structural Elements Hypotheses, N and Ca limit the abundance of silk-spinning and calcareous taxa, respectively. Mesostigmatids, pseudoscorpions, and spiders, all known to make silk, each increased with percentage of N of litter (r2 = 0.22, 0.31, 0.26, respectively). Calcareous isopods, but not diplopods, increased with percentage of Ca of litter (r2 = 0.59). In the Ecosystem Size Hypothesis, top predators are limited by available space. The abundance of the three remaining predators, chilopods, staphylinids, and ants, increased with litter depth (r2 = 0.31, 0.74, 0.69, respectively), and food webs from forests with deeper litter supported a higher ratio of predators to microbivores. These results suggest that biogeochemical gradients can provide a mechanism, through stoichiometry and trophic theory, shaping the geography of community structure. PMID:20120804

Kaspari, Michael; Yanoviak, Stephen P

2009-12-01

229

Road Salts as Environmental Constraints in Urban Pond Food Webs  

PubMed Central

Freshwater salinization is an emerging environmental filter in urban aquatic ecosystems that receive chloride road salt runoff from vast expanses of impervious surface cover. Our study was designed to evaluate the effects of chloride contamination on urban stormwater pond food webs through changes in zooplankton community composition as well as density and biomass of primary producers and consumers. From May – July 2009, we employed a 2×2×2 full-factorial design to manipulate chloride concentration (low?=?177 mg L?1 Cl?/high?=?1067 mg L?1 Cl?), gray treefrog (Hyla versicolor) tadpoles (presence/absence) and source of stormwater pond algae and zooplankton inoculum (low conductance/high conductance urban ponds) in 40, 600-L mesocosms. Road salt did serve as a constraint on zooplankton community structure, driving community divergence between the low and high chloride treatments. Phytoplankton biomass (chlorophyll [a] µg L?1) in the mesocosms was significantly greater for the high conductance inoculum (P<0.001) and in the high chloride treatment (P?=?0.046), whereas periphyton biomass was significantly lower in the high chloride treatment (P?=?0.049). Gray treefrog tadpole time to metamorphosis did not vary significantly between treatments. However, mass at metamorphosis was greater among tadpoles that experienced a faster than average time to metamorphosis and exposure to high chloride concentrations (P?=?0.039). Our results indicate differential susceptibility to chloride salts among algal resources and zooplankton taxa, and further suggest that road salts can act as a significant environmental constraint on urban stormwater pond communities. PMID:24587259

Van Meter, Robin J.; Swan, Christopher M.

2014-01-01

230

The authors of the ISAB Report Columbia River Basin Food Webs: Developing a Broader Scientific Foundation for Fish and Wildlife Restoration (ISAB 2011-1)  

E-print Network

The authors of the ISAB Report Columbia River Basin Food Webs: Developing a Broader Scientific restoration: Columbia River food webs Abstract. Well-functioning food webs are fundamental for sustaining on restoring habitat structure--without explicitly considering food webs--has been less successful than hoped

231

Spatial differences in East scotia ridge hydrothermal vent food webs: influences of chemistry, microbiology and predation on trophodynamics.  

PubMed

The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. ?(13)C of dissolved inorganic carbon from vent fluids ranged from -4.6‰ to 0.8‰ at E2 and from -4.4‰ to 1.5‰ at E9. The lowest macroconsumer ?(13)C was observed in peltospiroid gastropods (-30.0‰ to -31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest ?(13)C occurred in Kiwa sp. (-19.0‰ to -10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. ?(13)C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the ?(13)C and ?(34)S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites. PMID:23762393

Reid, William D K; Sweeting, Christopher J; Wigham, Ben D; Zwirglmaier, Katrin; Hawkes, Jeffrey A; McGill, Rona A R; Linse, Katrin; Polunin, Nicholas V C

2013-01-01

232

Spatial Differences in East Scotia Ridge Hydrothermal Vent Food Webs: Influences of Chemistry, Microbiology and Predation on Trophodynamics  

PubMed Central

The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. ?13C of dissolved inorganic carbon from vent fluids ranged from ?4.6‰ to 0.8‰ at E2 and from ?4.4‰ to 1.5‰ at E9. The lowest macroconsumer ?13C was observed in peltospiroid gastropods (?30.0‰ to ?31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest ?13C occurred in Kiwa sp. (?19.0‰ to ?10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. ?13C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the ?13C and ?34S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites. PMID:23762393

Reid, William D. K.; Sweeting, Christopher J.; Wigham, Ben D.; Zwirglmaier, Katrin; Hawkes, Jeffrey A.; McGill, Rona A. R.; Linse, Katrin; Polunin, Nicholas V. C.

2013-01-01

233

Trophic transfer of metals along freshwater food webs: Evidence of cadmium biomagnification in nature  

USGS Publications Warehouse

We conducted a study with cadmium (Cd) and copper (Cu) in the delta of San Francisco Bay, using nitrogen and carbon stable isotopes to identify trophic position and food web structure. Cadmium is progressively enriched among trophic levels in discrete epiphyte-based food webs composed of macrophyte-dwelling invertebrates (the first link being epiphytic algae) and fishes (the first link being gobies). Cadmium concentrations were biomagnified 15 times within the scope of two trophic links in both food webs. Trophic enrichment in invertebrates was twice that of fishes. No tendency toward trophic-level enrichment was observed for Cu, regardless of whether organisms were sorted by food web or treated on a taxonomic basis within discrete food webs. The greatest toxic effects of Cd are likely to occur with increasing trophic positions, where animals are ingesting Cd-rich prey (or food). In Franks Tract this occurs within discrete food chains composed of macrophyte-dwelling invertebrates or fishes inhabiting submerged aquatic vegetation. Unraveling ecosystem complexity is necessary before species most exposed and at risk can be identified. ?? 2005, by the American Society of Limnology and Oceanography, Inc.

Croteau, M. -N.; Luoma, S. N.; Stewart, A. R.

2005-01-01

234

Importance of parasites and their life cycle characteristics in determining the structure of a large marine food web  

Microsoft Academic Search

Summary 1. Despite their documented effects on trophic interactions and community structure, parasites are rarely included in food web analyses. The transmission routes of most parasitic helminths follow closely the trophic relationships among their successive hosts and are thus embedded in food webs, in a way that may influence energy flow and the structure of the web. 2. We investigated

ROSS M. THOMPSON; KIM N. MOURITSEN; ROBERT POULIN

235

Development of a Food Web Model (DOVE-Digital Organisms in a Virtual Ecosystem) to Examine Indirect Interactions in Food Webs and  

E-print Network

Indirect Interactions in Food Webs and Invasive Species Primary Investigator: Scott Peacor - Michigan State) to the net effect of predators and invasive species. There are two principal initial goal applications of Michigan, Katrina Button, Erik Goodman - Michigan State University, Tim Hunter - NOAA GLERL, Thomas Mehner

236

Food web structure of two Mediterranean lagoons under varying degree of eutrophication  

Microsoft Academic Search

The food web structure and functioning of two north-western Mediterranean lagoons exhibiting contrasting degrees of eutrophication and marine influences were compared through ?13C and ?15N analysis of major potential food sources and consumers. The Lapalme Lagoon is well preserved and has kept a natural and temporary connection with the open sea. Conversely, the Canet Lagoon is heavily eutrophicated and its

Antoine Carlier; Pascal Riera; Jean-Michel Amouroux; Jean-Yves Bodiou; Martin Desmalades; Antoine Grémare

2008-01-01

237

A framework for soil food web diagnostics: extension of the nematode faunal analysis concept  

Microsoft Academic Search

Nematodes, the earth’s most abundant metazoa, are ubiquitous in the soil environment. They are sufficiently large to be identifiable by light microscopy and sufficiently small to inhabit water films surrounding soil particles. They aggregate around and in food sources. They include component taxa of the soil food web at several trophic levels. They can be categorized into functional guilds whose

H. Ferris; T. Bongers; R. G. M. de Goede

2001-01-01

238

Food Chains & Webs. A Multimedia CD-ROM. [CD-ROM].  

ERIC Educational Resources Information Center

This CD-ROM is designed for classroom and individual use to teach and learn about food chains and food webs. Integrated animations, custom graphics, three-dimensional representations, photographs, and sound are featured for use in user-controlled activities. Interactive lessons are available to reinforce the subject material. Pre- and post-testing…

2001

239

Basic and Applied Ecology 13 (2012) 587596 Trophic diversity in a Mediterranean food web--Stable isotope analysis of  

E-print Network

Basic and Applied Ecology 13 (2012) 587­596 Trophic diversity in a Mediterranean food web levels is essential for a better understanding of food web structures and a better prediction of changes species. The possible role of soil fauna as a second main food resource besides the most commonly analyzed

Richner, Heinz

240

Parameter uncertainty, sensitivity, and sediment coupling in bioenergetics-based food web models  

SciTech Connect

A bioenergetics-based food web model was developed and calibrated using measured PCB water and sediment concentrations in two Great Lakes food webs: Green Bay, Michigan and Lake Ontario. The model incorporated functional based trophic levels and sediment, water, and food chain exposures of PCBs to aquatic biota. Sensitivity analysis indicated the parameters with the greatest influence on PCBs in top predators were lipid content of plankton and benthos, planktivore assimilation efficiency, Kow, prey selection, and ambient temperature. Sediment-associated PCBs were estimated to contribute over 90% of PCBs in benthivores and less than 50% in piscivores. Ranges of PCB concentrations in top predators estimated by Monte Carlo simulation incorporating parameter uncertainty were within one order of magnitude of modal values. Model applications include estimation of exceedences of human and ecological thresholds. The results indicate that point estimates from bioenergetics-based food web models have substantial uncertainty that should be considered in regulatory and scientific applications.

Barron, M.G.; Cacela, D.; Beltman, D. [Hagler Bailly, Boulder, CO (United States)

1995-12-31

241

Cycling Through the Food Web: Let's Go on a Research Cruise  

NSDL National Science Digital Library

This site presents an account of a research cruise to investigate how the food webs in different oceanic habitats vary. The scientists wanted to see ocean life in its natural environment and conduct experiments that would not be possible in the laboratory. They looked specifically at three types of ocean habitat: the open ocean, the continental shelf, and an upwelling area. The researchers were hoping to learn the answers to two questions: 'How well do the actual marine food webs match our food chain models for the three habitats?' and 'How does the microbial community in each food web change with depth?'. Students can follow their research and fill out an activity and question checklist as they go along. There is also a page of information for teachers.

242

Sources and transfers of methylmercury in adjacent river and forest food webs.  

PubMed

Nearly all ecosystems are contaminated with highly toxic methylmercury (MeHg), but the specific sources and pathways leading to the uptake of MeHg within and among food webs are not well understood. In this study, we report stable mercury (Hg) isotope compositions in food webs in a river and an adjacent forest in northern California and demonstrate the utility of Hg isotopes for studying MeHg sources and cross-habitat transfers. We observed large differences in both ?(202)Hg (mass-dependent fractionation) and ?(199)Hg (mass-independent fractionation) within both food webs. The majority of isotopic variation within each food web could be accounted for by differing proportions of inorganic Hg [Hg(II)] and MeHg along food chains. We estimated mean isotope values of Hg(II) and MeHg in each habitat and found a large difference in ?(202)Hg between Hg(II) and MeHg (?2.7‰) in the forest but not in the river (?0.25‰). This is consistent with in situ Hg(II) methylation in the study river but suggests Hg(II) methylation may not be important in the forest. In fact, the similarity in ?(202)Hg between MeHg in forest food webs and Hg(II) in precipitation suggests that MeHg in forest food webs may be derived from atmospheric sources (e.g., rainfall, fog). Utilizing contrasting ?(202)Hg values between MeHg in river food webs (-1.0‰) and MeHg in forest food webs (+0.7‰), we estimate with a two-source mixing model that ?55% of MeHg in two riparian spiders is derived from riverine sources while ?45% of MeHg originates from terrestrial sources. Thus, stable Hg isotopes can provide new information on subtle differences in sources of MeHg and trace MeHg transfers within and among food webs in natural ecosystems. PMID:23033864

Tsui, Martin Tsz Ki; Blum, Joel D; Kwon, Sae Yun; Finlay, Jacques C; Balogh, Steven J; Nollet, Yabing H

2012-10-16

243

Is benthic food web structure related to diversity of marine macrobenthic communities?  

NASA Astrophysics Data System (ADS)

Numerical structure and the organisation of food webs within macrozoobenthic communities has been assessed in the European waters (Svalbard, Barents Sea, Baltic Sea, North Sea, Atlantic Ocean and the Mediterranean Sea) to address the interactions between biodiversity and ecosystem functioning. Abundance and classical species diversity indices (S, H', J) of macrofaunal communities were related to principal attributes of food webs (relative trophic level and food chain length, FCL) that were determined from carbon and nitrogen stable isotope values. Structure of marine macrobenthos varies substantially at a geographical scale; total abundance ranges from 63 ind. m-2 to 34,517 ind. m-2, species richness varies from 3 to 166 and the Shannon-Weaver diversity index from 0.26 to 3.26 while Pielou's evenness index is below 0.73. The major source of energy for macrobenthic communities is suspended particulate organic matter, consisting of phytoplankton and detrital particles, sediment particulate organic matter, and microphytobenthos in varying proportions. These food sources support the presence of suspension- and deposit-feeding communities, which dominate numerically on the sea floor. Benthic food webs include usually four to five trophic levels (FCL varies from 3.08 to 4.86). Most species are assigned to the second trophic level (primary consumers), fewer species are grouped in the third trophic level (secondary consumers), and benthic top predators are the least numerous. Most species cluster primarily at the lowest trophic level that is consistent with the typical organization of pyramidal food webs. Food chain length increases with biodiversity, highlighting a positive effect of more complex community structure on food web organisation. In more diverse benthic communities, energy is transferred through more trophic levels while species-poor communities sustain a shorter food chain.

Soko?owski, A.; Wo?owicz, M.; Asmus, H.; Asmus, R.; Carlier, A.; Gasiunaité, Z.; Grémare, A.; Hummel, H.; Lesutiené, J.; Razinkovas, A.; Renaud, P. E.; Richard, P.; K?dra, M.

2012-08-01

244

Antarctic marine biodiversity and deep-sea hydrothermal vents.  

PubMed

The diversity of many marine benthic groups is unlike that of most other taxa. Rather than declining from the tropics to the poles, much of the benthos shows high diversity in the Southern Ocean. Moreover, many species are unique to the Antarctic region. Recent work has shown that this is also true of the communities of Antarctic deep-sea hydrothermal vents. Vent ecosystems have been documented from many sites across the globe, associated with the thermally and chemically variable habitats found around these, typically high temperature, streams that are rich in reduced compounds and polymetallic sulphides. The animal communities of the East Scotia Ridge vent ecosystems are very different to those elsewhere, though the microbiota, which form the basis of vent food webs, show less differentiation. Much of the biological significance of deep-sea hydrothermal vents lies in their biodiversity, the diverse biochemistry of their bacteria, the remarkable symbioses among many of the marine animals and these bacteria, and the prospects that investigations of these systems hold for understanding the conditions that may have led to the first appearance of life. The discovery of diverse and unusual Antarctic hydrothermal vent ecosystems provides opportunities for new understanding in these fields. Moreover, the Antarctic vents south of 60°S benefit from automatic conservation under the Convention on the Conservation of Antarctic Marine Living Resources and the Antarctic Treaty. Other deep-sea hydrothermal vents located in international waters are not protected and may be threatened by growing interests in deep-sea mining. PMID:22235192

Chown, Steven L

2012-01-01

245

Antarctic Marine Biodiversity and Deep-Sea Hydrothermal Vents  

PubMed Central

The diversity of many marine benthic groups is unlike that of most other taxa. Rather than declining from the tropics to the poles, much of the benthos shows high diversity in the Southern Ocean. Moreover, many species are unique to the Antarctic region. Recent work has shown that this is also true of the communities of Antarctic deep-sea hydrothermal vents. Vent ecosystems have been documented from many sites across the globe, associated with the thermally and chemically variable habitats found around these, typically high temperature, streams that are rich in reduced compounds and polymetallic sulphides. The animal communities of the East Scotia Ridge vent ecosystems are very different to those elsewhere, though the microbiota, which form the basis of vent food webs, show less differentiation. Much of the biological significance of deep-sea hydrothermal vents lies in their biodiversity, the diverse biochemistry of their bacteria, the remarkable symbioses among many of the marine animals and these bacteria, and the prospects that investigations of these systems hold for understanding the conditions that may have led to the first appearance of life. The discovery of diverse and unusual Antarctic hydrothermal vent ecosystems provides opportunities for new understanding in these fields. Moreover, the Antarctic vents south of 60°S benefit from automatic conservation under the Convention on the Conservation of Antarctic Marine Living Resources and the Antarctic Treaty. Other deep-sea hydrothermal vents located in international waters are not protected and may be threatened by growing interests in deep-sea mining. PMID:22235192

Chown, Steven L.

2012-01-01

246

Linking Water Quality and Quantity in Environmental Flow Assessment in Deteriorated Ecosystems: A Food Web View  

PubMed Central

Most rivers worldwide are highly regulated by anthropogenic activities through flow regulation and water pollution. Environmental flow regulation is used to reduce the effects of anthropogenic activities on aquatic ecosystems. Formulating flow alteration–ecological response relationships is a key factor in environmental flow assessment. Traditional environmental flow models are characterized by natural relationships between flow regimes and ecosystem factors. However, food webs are often altered from natural states, which disturb environmental flow assessment in such ecosystems. In ecosystems deteriorated by heavy anthropogenic activities, the effects of environmental flow regulation on species are difficult to assess with current modeling approaches. Environmental flow management compels the development of tools that link flow regimes and food webs in an ecosystem. Food web approaches are more suitable for the task because they are more adaptive for disordered multiple species in a food web deteriorated by anthropogenic activities. This paper presents a global method of environmental flow assessment in deteriorated aquatic ecosystems. Linkages between flow regimes and food web dynamics are modeled by incorporating multiple species into an ecosystem to explore ecosystem-based environmental flow management. The approach allows scientists and water resources managers to analyze environmental flows in deteriorated ecosystems in an ecosystem-based way. PMID:23894669

Chen, He; Ma, Lekuan; Guo, Wei; Yang, Ying; Guo, Tong; Feng, Cheng

2013-01-01

247

Legacy effects of drought on plant growth and the soil food web.  

PubMed

Soils deliver important ecosystem services, such as nutrient provision for plants and the storage of carbon (C) and nitrogen (N), which are greatly impacted by drought. Both plants and soil biota affect soil C and N availability, which might in turn affect their response to drought, offering the potential to feed back on each other's performance. In a greenhouse experiment, we compared legacy effects of repeated drought on plant growth and the soil food web in two contrasting land-use systems: extensively managed grassland, rich in C and with a fungal-based food web, and intensively managed wheat lower in C and with a bacterial-based food web. Moreover, we assessed the effect of plant presence on the recovery of the soil food web after drought. Drought legacy effects increased plant growth in both systems, and a plant strongly reduced N leaching. Fungi, bacteria, and their predators were more resilient after drought in the grassland soil than in the wheat soil. The presence of a plant strongly affected the composition of the soil food web, and alleviated the effects of drought for most trophic groups, regardless of the system. This effect was stronger for the bottom trophic levels, whose resilience was positively correlated to soil available C. Our results show that plant belowground inputs have the potential to affect the recovery of belowground communities after drought, with implications for the functions they perform, such as C and N cycling. PMID:22555357

de Vries, Franciska Trijntje; Liiri, Mira E; Bjørnlund, Lisa; Setälä, Heikki M; Christensen, Søren; Bardgett, Richard D

2012-11-01

248

The role of body mass in diet contiguity and food-web structure.  

PubMed

1. The idea that species occupy distinct niches is a fundamental concept in ecology. Classically, the niche was described as an n-dimensional hypervolume where each dimension represents a biotic or abiotic characteristic. More recently, it has been hypothesised that a single dimension may be sufficient to explain the system-level organization of trophic interactions observed between species in a community. 2. Here, we test the hypothesis that species body mass is that single dimension. Specifically, we determine how the intervality of food webs ordered by body size compares to that of randomly ordered food webs. We also extend this analysis beyond the community level to the effect of body mass in explaining the diets of individual species. 3. We conclude that body mass significantly explains the ordering of species and the contiguity of diets in empirical communities. 4. At the species-specific level, we find that the degree to which body mass is a significant explanatory variable depends strongly on the phylogenetic history, suggesting that other evolutionarily conserved traits partly account for species' roles in the food web. 5. Our investigation of the role of body mass in food webs thus helps us to better understand the important features of community food-web structure and the evolutionary forces that have led us to the communities we observe. PMID:21401590

Stouffer, Daniel B; Rezende, Enrico L; Amaral, Luís A Nunes

2011-05-01

249

The cesium:potassium index of food web structure -- A complementary approach to stable isotope indicators  

SciTech Connect

Stable isotope shifts with trophic or average feeding level are an important tool in characterizing sampled food webs for biomagnification and other studies. However, spatial and temporal variations in isotope ratios in the environment can introduce uncertainties in interpreting such data. An elemental index, the Cs/K ratio, has proved to be a useful tool in assessing the reliability of the trophic level approach to characterizing marine and estuarine food webs. A major advantage is the constant value of this elemental ratio in seawater. Studies conducted over the last three decades in a variety of aquatic ecosystems generally have yielded consistent results using the Cs/K Index. The mean Trophic Transfer Factor obtained from twelve food web surveys was 2.0 +/- 0.1 (SE), indicating substantial structure for most of the food webs sampled. An empirical technique, termed the Exponential Biomagnification Model, was developed to simplify the observed variation of Cs/K with Trophic Level Assignment. This approach has proved useful in assessing sampled food webs with non-integer Trophic Level Assignments, and obtaining average Trophic Transfer Factors for the Cs/K ratio and corresponding tissue concentrations of environmental contaminants.

Young, D. [Environmental Protection Agency, Newport, OR (United States)

1995-12-31

250

Soil food web properties explain ecosystem services across European land use systems.  

PubMed

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world. PMID:23940339

de Vries, Franciska T; Thébault, Elisa; Liiri, Mira; Birkhofer, Klaus; Tsiafouli, Maria A; Bjørnlund, Lisa; Bracht Jørgensen, Helene; Brady, Mark Vincent; Christensen, Søren; de Ruiter, Peter C; d'Hertefeldt, Tina; Frouz, Jan; Hedlund, Katarina; Hemerik, Lia; Hol, W H Gera; Hotes, Stefan; Mortimer, Simon R; Setälä, Heikki; Sgardelis, Stefanos P; Uteseny, Karoline; van der Putten, Wim H; Wolters, Volkmar; Bardgett, Richard D

2013-08-27

251

FOOD WEBS IN URBAN FISH `COMMUNITIES' FROM THE SALT RIVER PROJECT CANALS Lara A. Ferry, Bonnie Ahr  

E-print Network

al. (2009)*who quantified food webs flathead catfish Pylodictis olivaris channel catfish Ictalurus punctatus sonora sucker Catostomus insignis desert sucker Pantosteus clarki largemouth bass Micropterus

Hall, Sharon J.

252

Macrofaunal abundance and composition on the West Antarctic Peninsula continental shelf: Evidence for a sediment ‘food bank’ and similarities to deep-sea habitats  

NASA Astrophysics Data System (ADS)

To assess the impact and fate of the summer phytoplankton bloom on Antarctic benthos, we evaluated temporal and spatial patterns in macrofaunal abundance and taxonomic composition along a transect crossing the West Antarctic Peninsula (WAP) continental shelf. As part of the FOODBANCS project, we sampled three sites at 550-625 m depths during five cruises occurring in November 1999, February-March 2000, June 2000, October 2000 and March 2001. We used a combination of megacore and box-core samplers to take 81 samples, and collected over 30,000 macrofaunal individuals, one of the largest sampling efforts on the Antarctic shelf to date. Comparison of the two sampling methodologies (box core and megacore) indicates similar macrofaunal densities, but with significant differences in taxonomic composition, a reflection of the different spatial scales of sampling. Macrofaunal abundances on the WAP shelf were relatively high compared to other Antarctic shelf settings. At two of the three sampling sites, macrofaunal abundance remained constant throughout the year, which is consistent with the presence of a sediment 'food bank'. Differences were observed in taxonomic composition at the site closest to the coast (Station A), driven by higher abundances of sub-surface-deposit feeders. A significant temporal response was observed in the ampharetid polychaetes at Station A, with an abundance peak in the late fall post-bloom period; this may have resulted from juvenile recruitment during the summer bloom. Familial composition of macrofaunal polychaetes on the WAP shelf is more closely related to deep-sea abyssal fauna than to other shelf regions, and we hypothesize that this is a result of both local ecological conditions (low temperatures) and a reflection of historical processes such as extinctions on the Antarctic shelf during previous glacial maxima followed by recolonization from the deep sea.

Glover, Adrian G.; Smith, Craig R.; Mincks, Sarah L.; Sumida, Paulo Y. G.; Thurber, Andrew R.

2008-11-01

253

More than a meal… integrating non-feeding interactions into food webs.  

PubMed

Ecology Letters (2012) ABSTRACT: Organisms eating each other are only one of many types of well documented and important interactions among species. Other such types include habitat modification, predator interference and facilitation. However, ecological network research has been typically limited to either pure food webs or to networks of only a few (<3) interaction types. The great diversity of non-trophic interactions observed in nature has been poorly addressed by ecologists and largely excluded from network theory. Herein, we propose a conceptual framework that organises this diversity into three main functional classes defined by how they modify specific parameters in a dynamic food web model. This approach provides a path forward for incorporating non-trophic interactions in traditional food web models and offers a new perspective on tackling ecological complexity that should stimulate both theoretical and empirical approaches to understanding the patterns and dynamics of diverse species interactions in nature. PMID:22313549

Kéfi, Sonia; Berlow, Eric L; Wieters, Evie A; Navarrete, Sergio A; Petchey, Owen L; Wood, Spencer A; Boit, Alice; Joppa, Lucas N; Lafferty, Kevin D; Williams, Richard J; Martinez, Neo D; Menge, Bruce A; Blanchette, Carol A; Iles, Alison C; Brose, Ulrich

2012-02-01

254

More than a meal: integrating non-feeding interactions into food webs  

USGS Publications Warehouse

Organisms eating each other are only one of many types of well documented and important interactions among species. Other such types include habitat modification, predator interference and facilitation. However, ecological network research has been typically limited to either pure food webs or to networks of only a few (<3) interaction types. The great diversity of non-trophic interactions observed in nature has been poorly addressed by ecologists and largely excluded from network theory. Herein, we propose a conceptual framework that organises this diversity into three main functional classes defined by how they modify specific parameters in a dynamic food web model. This approach provides a path forward for incorporating non-trophic interactions in traditional food web models and offers a new perspective on tackling ecological complexity that should stimulate both theoretical and empirical approaches to understanding the patterns and dynamics of diverse species interactions in nature.

Kéfi, Sonia; Berlow, Eric L.; Wieters, Evie A.; Navarrete, Sergio A.; Petchey, Owen L.; Wood, Spencer A.; Boit, Alice; Joppa, Lucas N.; Lafferty, Kevin d.; Williams, Richard J.; Martinez, Neo D.; Menge, Bruce A.; Blanchette, Carol A.; Iles, Alison C.; Brose, Ulrich

2012-01-01

255

Seasonal variation in mercury and food web biomagnification in Lake Ontario, Canada.  

PubMed

Seasonal variation in mercury (Hg) concentrations and food web structure was assessed for eastern Lake Ontario. Hg concentrations, measured in 6 species of invertebrates and 8 species of fishes, tended to be highest in the spring and lowest in the summer for most biota. Yellow perch (Perca flavescens) exhibited significant ontogenetic shifts in diet and Hg, although such patterns were not evident for other species. Food web structure, as indicated by stable isotope values (?(15)N, ?(13)C) was not static. Log-transformed Hg data were strongly and consistently correlated with ?(15)N values for the whole food web in each of the three seasons (slopes, 0.17-0.24) and across the entire year (slope, 0.2). While significantly different between seasons, the regression slope values are still consistent with published global Hg biomagnification rates. Our results indicate that the assessment of Hg trends in Great Lakes must take into account seasonal patterns and time of sampling. PMID:22230083

Zhang, Liang; Campbell, Linda M; Johnson, Timothy B

2012-02-01

256

Indicator species for limited budgets: Profiles of trophic levels, food web placement, and ecotoxicological sensitivity  

SciTech Connect

The identification of indicator and/or keystone species is directly related to the success of a quantitative Ecological Risk Assessment (ERA) at a hazardous waste site. In a fiscally perfect world, species would be selected to represent each and every trophic level within the aquatic and/or terrestrial food web. However, because limited budgets are the norm, scientifically valid ``shortcuts`` are in high demand. LAW has conducted quantitative ERAs at more than thirty hazardous waste sites, with as many as ten indicator species per site (selected to represent trophic levels within each habitat type present). Data from these assessments have been compiled and evaluated for the purpose of identifying species which demonstrate the highest toxicological sensitivity within the food web. Budgets can be reduced by incorporating this proposed quantitative screening-level ERA approach. This presentation will specify quantitative ERA methodology, ecotoxicological extrapolations, uncertainties to consider, trophic level profiles, food web placement, and indicator species sensitivity.

Sorenson, M.T.; Margolin, J.A.

1995-12-31

257

The microbial food web in the European Regional Seas Ecosystem Model  

NASA Astrophysics Data System (ADS)

In the framework of the complex dynamical European Regional Seas Ecosystem Model (ERSEM) a module describing the microbial part of the pelagic ecosystem has been developed. The module contains the carbon and nutrient dynamics of pelagic bacteria, heterotrophic flagellates and microzooplankton and interacts with the other parts of the model via phytoplankton, particulate and dissolved organic matter and mesozooplankton. A short description of the module is given and the results are discussed. It is demonstrated that in an application of ERSEM to the North Sea there is a gradual shift in dominance from the continental coast boxes to the offshore deeper areas between the different food webs, from what in the literature is termed the classical food web to the microbial food web, concomitant with a gradual decrease in the efficiency of the microbial loop.

Baretta-Bekker, J. G.; Baretta, J. W.; Koch Rasmussen, E.

258

From the Top of the World...to the Bottom of the Food Web  

NSDL National Science Digital Library

Four teaching units show how NASA satellites measure ocean productivity. Topics cover: marine food web from producers to consumers and decomposers; phytoplankton diversity, classification and adaptations; studying photosynthesis with technology, from microscopes to satellites; and biology of algal blooms. Units include: background, lesson plans using on-line data or instructions for classroom and field activities; web links for further study. Lessons are aligned to teaching standards from McREL. Order educational CD-ROM, Phytopia. DLESE and Homeschool featured site.

259

Biomagnification of mercury in aquatic food webs: a worldwide meta-analysis.  

PubMed

The slope of the simple linear regression between log10 transformed mercury (Hg) concentration and stable nitrogen isotope values (?(15)N), hereafter called trophic magnification slope (TMS), from several trophic levels in a food web can represent the overall degree of Hg biomagnification. We compiled data from 69 studies that determined total Hg (THg) or methyl Hg (MeHg) TMS values in 205 aquatic food webs worldwide. Hg TMS values were compared against physicochemical and biological factors hypothesized to affect Hg biomagnification in aquatic systems. Food webs ranged across 1.7 ± 0.7 (mean ± SD) and 1.8 ± 0.8 trophic levels (calculated using ?(15)N from baseline to top predator) for THg and MeHg, respectively. The average trophic level (based on ?(15)N) of the upper-trophic-level organisms in the food web was 3.7 ± 0.8 and 3.8 ± 0.8 for THg and MeHg food webs, respectively. For MeHg, the mean TMS value was 0.24 ± 0.08 but varied from 0.08 to 0.53 and was, on average, 1.5 times higher than that for THg with a mean of 0.16 ± 0.11 (range: -0.19 to 0.48). Both THg and MeHg TMS values were significantly and positively correlated with latitude. TMS values in freshwater sites increased with dissolved organic carbon and decreased with total phosphorus and atmospheric Hg deposition. Results suggest that Hg biomagnification through food webs is highest in cold and low productivity systems; however, much of the among-system variability in TMS values remains unexplained. We identify critical data gaps and provide recommendations for future studies that would improve our understanding of global Hg biomagnification. PMID:24151937

Lavoie, Raphael A; Jardine, Timothy D; Chumchal, Matthew M; Kidd, Karen A; Campbell, Linda M

2013-12-01

260

Parasites affect food web structure primarily through increased diversity and complexity.  

PubMed

Comparative research on food web structure has revealed generalities in trophic organization, produced simple models, and allowed assessment of robustness to species loss. These studies have mostly focused on free-living species. Recent research has suggested that inclusion of parasites alters structure. We assess whether such changes in network structure result from unique roles and traits of parasites or from changes to diversity and complexity. We analyzed seven highly resolved food webs that include metazoan parasite data. Our analyses show that adding parasites usually increases link density and connectance (simple measures of complexity), particularly when including concomitant links (links from predators to parasites of their prey). However, we clarify prior claims that parasites "dominate" food web links. Although parasites can be involved in a majority of links, in most cases classic predation links outnumber classic parasitism links. Regarding network structure, observed changes in degree distributions, 14 commonly studied metrics, and link probabilities are consistent with scale-dependent changes in structure associated with changes in diversity and complexity. Parasite and free-living species thus have similar effects on these aspects of structure. However, two changes point to unique roles of parasites. First, adding parasites and concomitant links strongly alters the frequency of most motifs of interactions among three taxa, reflecting parasites' roles as resources for predators of their hosts, driven by trophic intimacy with their hosts. Second, compared to free-living consumers, many parasites' feeding niches appear broader and less contiguous, which may reflect complex life cycles and small body sizes. This study provides new insights about generic versus unique impacts of parasites on food web structure, extends the generality of food web theory, gives a more rigorous framework for assessing the impact of any species on trophic organization, identifies limitations of current food web models, and provides direction for future structural and dynamical models. PMID:23776404

Dunne, Jennifer A; Lafferty, Kevin D; Dobson, Andrew P; Hechinger, Ryan F; Kuris, Armand M; Martinez, Neo D; McLaughlin, John P; Mouritsen, Kim N; Poulin, Robert; Reise, Karsten; Stouffer, Daniel B; Thieltges, David W; Williams, Richard J; Zander, Claus Dieter

2013-01-01

261

Parasites Affect Food Web Structure Primarily through Increased Diversity and Complexity  

PubMed Central

Comparative research on food web structure has revealed generalities in trophic organization, produced simple models, and allowed assessment of robustness to species loss. These studies have mostly focused on free-living species. Recent research has suggested that inclusion of parasites alters structure. We assess whether such changes in network structure result from unique roles and traits of parasites or from changes to diversity and complexity. We analyzed seven highly resolved food webs that include metazoan parasite data. Our analyses show that adding parasites usually increases link density and connectance (simple measures of complexity), particularly when including concomitant links (links from predators to parasites of their prey). However, we clarify prior claims that parasites “dominate” food web links. Although parasites can be involved in a majority of links, in most cases classic predation links outnumber classic parasitism links. Regarding network structure, observed changes in degree distributions, 14 commonly studied metrics, and link probabilities are consistent with scale-dependent changes in structure associated with changes in diversity and complexity. Parasite and free-living species thus have similar effects on these aspects of structure. However, two changes point to unique roles of parasites. First, adding parasites and concomitant links strongly alters the frequency of most motifs of interactions among three taxa, reflecting parasites' roles as resources for predators of their hosts, driven by trophic intimacy with their hosts. Second, compared to free-living consumers, many parasites' feeding niches appear broader and less contiguous, which may reflect complex life cycles and small body sizes. This study provides new insights about generic versus unique impacts of parasites on food web structure, extends the generality of food web theory, gives a more rigorous framework for assessing the impact of any species on trophic organization, identifies limitations of current food web models, and provides direction for future structural and dynamical models. PMID:23776404

Dunne, Jennifer A.; Lafferty, Kevin D.; Dobson, Andrew P.; Hechinger, Ryan F.; Kuris, Armand M.; Martinez, Neo D.; McLaughlin, John P.; Mouritsen, Kim N.; Poulin, Robert; Reise, Karsten; Stouffer, Daniel B.; Thieltges, David W.; Williams, Richard J.; Zander, Claus Dieter

2013-01-01

262

Parasites affect food web structure primarily through increased diversity and complexity  

USGS Publications Warehouse

Comparative research on food web structure has revealed generalities in trophic organization, produced simple models, and allowed assessment of robustness to species loss. These studies have mostly focused on free-living species. Recent research has suggested that inclusion of parasites alters structure. We assess whether such changes in network structure result from unique roles and traits of parasites or from changes to diversity and complexity. We analyzed seven highly resolved food webs that include metazoan parasite data. Our analyses show that adding parasites usually increases link density and connectance (simple measures of complexity), particularly when including concomitant links (links from predators to parasites of their prey). However, we clarify prior claims that parasites ‘‘dominate’’ food web links. Although parasites can be involved in a majority of links, in most cases classic predation links outnumber classic parasitism links. Regarding network structure, observed changes in degree distributions, 14 commonly studied metrics, and link probabilities are consistent with scale-dependent changes in structure associated with changes in diversity and complexity. Parasite and free-living species thus have similar effects on these aspects of structure. However, two changes point to unique roles of parasites. First, adding parasites and concomitant links strongly alters the frequency of most motifs of interactions among three taxa, reflecting parasites’ roles as resources for predators of their hosts, driven by trophic intimacy with their hosts. Second, compared to free-living consumers, many parasites’ feeding niches appear broader and less contiguous, which may reflect complex life cycles and small body sizes. This study provides new insights about generic versus unique impacts of parasites on food web structure, extends the generality of food web theory, gives a more rigorous framework for assessing the impact of any species on trophic organization, identifies limitations of current food web models, and provides direction for future structural and dynamical models.

Dunne, Jennifer A.; Lafferty, Kevin D.; Dobson, Andrew P.; Hechinger, Ryan F.; Kuris, Armand M.; Martinez, Neo D.; McLaughlin, John P.; Mouritsen, Kim N.; Poulin, Robert; Reise, Karsten; Stouffer, Daniel B.; Thieltges, David W.; Williams, Richard J.; Zander, Claus Dieter

2013-01-01

263

The National Food Safety Database Web Site: Irradiation  

NSDL National Science Digital Library

The National Food Safety Database, a cooperative project of the United States Department of Agriculture and several universities, provides a section on food irradiation that discusses the process, the history of irradiation, and its relationship to food safety, among other features. It is highlighted by a 39-part, annotated slide show that supports the process. Previously approved for use on poultry and fruits and vegetables in the US, irradiation can kill disease-causing bacteria like Salmonella and Escherichia coli 0157:H7 (discussed in the Scout Report for Science and Engineering's In the News section, September 17, 1997), and molds and funguses that cause rot. With recent US Food and Drug Administration (FDA) approval, irradiation can now be used to process red meat (e.g., beef, pork, lamb, and byproducts). The process involves exposing food to a source of radiation such as gamma rays from radioactive cobalt 60, cesium 137, or x-rays. No radioactive material is added to the product, and the technique is routinely used on grains and spices, as well as for sterilizing disposable medical devices. In spite of a number of tests conducted over the last 30 years substantiating its safety, irradiation has not gained widespread public acceptance in the US. This is largely due to the public's general fear of processes utilizing radiation. Supporters of the technology claim that it will virtually eliminate food-borne illness in the US, while skeptics feel that technology such as steam treatment can accomplish adequate sterilization without the purported risks and public concern associated with irradiation. (8) The National Food Safety Database, a cooperative project of the United States Department of Agriculture and several universities, provides a section on food irradiation that discusses the process, history of irradiation, and its relationship to food safety, among other features. It features a 39-part, annotated slide show that strongly supports the process.

1994-01-01

264

High-resolution food webs based on nitrogen isotopic composition of amino acids  

PubMed Central

Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position estimates. In the present study, we employ this method to estimate the trophic positions of 200 free-roaming organisms, representing 39 species in coastal marine (a stony shore) and 38 species in terrestrial (a fruit farm) environments. Based on the trophic positions from the isotopic composition of amino acids, we are able to resolve the trophic structure of these complex food webs. Our approach reveals a high degree of trophic omnivory (i.e., noninteger trophic positions) among carnivorous species such as marine fish and terrestrial hornets.This information not only clarifies the trophic tendencies of species within their respective communities, but also suggests that trophic omnivory may be common in these webs. PMID:25360278

Chikaraishi, Yoshito; Steffan, Shawn A; Ogawa, Nanako O; Ishikawa, Naoto F; Sasaki, Yoko; Tsuchiya, Masashi; Ohkouchi, Naohiko

2014-01-01

265

The Serengeti food web: empirical quantification and analysis of topological changes under increasing human impact.  

PubMed

1.?To address effects of land use and human overexploitation on wildlife populations, it is essential to better understand how human activities have changed species composition, diversity and functioning. Theoretical studies modelled how network properties change under human-induced, non-random species loss. However, we lack data on realistic species-loss sequences in threatened, real-world food webs to parameterize these models. 2.?Here, we present a first size-structured topological food web of one of the most pristine terrestrial ecosystems in the world, the Serengeti ecosystem (Tanzania). The food web consists of 95 grouped nodes and includes both invertebrates and vertebrates ranging from body masses between 10(-7) and 10(4) kg. 3.?We study the topological changes in this food web that result from the simulated IUCN-based species-loss sequence representing current species vulnerability to human disturbances in and around this savanna ecosystem. We then compare this realistic extinction scenario with other extinction sequences based on body size and connectance and perform an analysis of robustness of this savanna food web. 4.?We demonstrate that real-world species loss in this case starts with the biggest (mega) herbivores and top predators, causing higher predator-prey mass ratios. However, unlike theoretically modelled linear species deletion sequences, this causes poor-connected species to be lost first, while more highly connected species become lost as human impact progresses. This food web shows high robustness to decreasing body size and increasing connectance deletion sequences compared with a high sensitivity to the decreasing connectance deletion scenario. 5.?Furthermore, based on the current knowledge of the Serengeti ecosystem, we discuss how the focus on food web topology alone, disregarding nontrophic interactions, may lead to an underestimation of human impacts on wildlife communities, with the number of trophic links affected by a factor of two. 6.?This study underlines the importance of integrative efforts between the development of food web theory and basic field work approaches in the quantification of the structure of interaction networks to sustain natural ecosystems in a changing world. PMID:21155772

de Visser, Sara N; Freymann, Bernd P; Olff, Han

2011-03-01

266

Bioaccumulation and biomagnification of polybrominated diphenyl ethers in a food web of Lake Michigan.  

PubMed

Polybrominated diphenyl ethers are hydrophobic chemicals and can biomagnify in food chains. Little is known about the biomagnification of PBDEs in the Lake Michigan food web. Plankton, Diporeia, lake whitefish, lake trout, and Chinook salmon were collected from Lake Michigan in 2006 between April and August. Fish liver and muscle and whole invertebrates were analyzed for six PBDEs (BDE-47, 99, 100, 153, 154, and 209). Carbon and nitrogen stable isotope ratios (delta(13)C and delta(15)N) were also quantified in order to establish the trophic structure of the food web. Geometric means of Sigma PBDE concentrations in fish ranged from 0.562 to 1.61 microg/g-lipid. BDE-209 concentrations ranged from 0.184 to 1.23 microg/g-lipid in all three fish species. Sigma BDE-47, 99, and 209 comprised 80-94% of Sigma PBDE molar concentration. Within each fish species, there were no significant differences in PBDE concentrations between liver and muscle. The highest concentration of BDE-209 (144 microg/g-lipid) was detected in Diporeia. Based on analysis of delta(15)N and PBDE concentrations, BDE-47 and 100 were found to biomagnify, whereas BDE-209 did not. A significant negative correlation between BDE-209 and trophic level was found in this food web. Biomagnification factors were also calculated and again BDE-47 and 100 biomagnified between food web members whereas BDE-209 did not. Diporeia could be one of the main dietary sources of BDE-209 for fish in Lake Michigan; BDE-47 and 100 biomagnified within this food chain; the concentration of BDE-209 decreased at higher trophic levels, suggesting partial uptake and/or biotransformation of BDE-209 in the Lake Michigan food web. PMID:19882349

Kuo, Yin-Ming; Sepúlveda, Maria S; Hua, Inez; Ochoa-Acuña, Hugo G; Sutton, Trent M

2010-04-01

267

Using stable isotopes to differentiate trophic feeding channels within soil food webs.  

PubMed

The soil is probably the most diverse habitat there is, with organisms ranging in sizes from less than 1 ?m to several metres in length. However, it is increasingly evident that we know little about the interactions occurring between these organisms, the functions that they perform as individual species, or together within their different feeding guilds. These interactions between groups of organisms and physical and chemical processes shape the soil as a habitat and influence the nature of the soil food web with consequences for the above-ground vegetation and food web. Protists are known as one of the most abundant groups of bacterivores within the soil; however, they are also consumers of a number of other food sources. Even though they are responsible for a large proportion of the mineralisation of bacterial biomass and have a large impact on the C and N cycles within the soil they are regularly overlooked when investigating the complete soil food web. Recently, stable isotopes have been used to determine trophic interactions and here we describe how this technique has been used to highlight linkages between protists and the soil food web. PMID:22299758

Crotty, Felicity V; Adl, Sina M; Blackshaw, Rod P; Murray, Philip J

2012-01-01

268

The role of cannibalism and contaminant source on bioaccumulation in aquatic food webs.  

PubMed

Two aspects of bioaccumulation in an aquatic food web are explored. First, the possible implications of cannibalism, including the scavenging of conspecifics, as a factor influencing food web bioaccumulation and biomagnification are explored by examining the behavior of total polychlorinated biphenyls (PCBs) in a simple aquatic food web consisting of plankton, juvenile and adult Mysis relicta, Diporeia, and alewife. From an analysis of trophic transfer efficiencies and food consumption rates, it is concluded that, for M. relicta, a maximum extent of cannibalism in a population is about 10%, although certain individuals may be more cannibalistic. The model suggests that cannibalism and scavenging of dead conspecifics generally result in an increase in concentration by self-biomagnification, but the effect is small and unlikely to exceed 5% on the average. Concentration differences also are likely to result from changes in the relative amounts of the dietary components. Highly cannibalistic individuals may achieve higher levels of bioaccumulation. In extreme cases, the food web model becomes mathematically unstable because of excessive feedback of high concentrations. A major implication is that differences in extent of cannibalism and scavenging probably contribute significantly to natural concentration variation in a population. Second, and more important, is the effect of benthic versus pelagic sources, especially when significant fugacity differences exist between these zones. A simple method is described by which the separate contributions from these sources can be estimated for organisms at higher trophic levels. PMID:15839566

Fraser, Alison J; Cahill, Thomas M; Lasenby, David C; Mackay, Donald; Milford, Lynne

2005-04-01

269

Planktonic microbes: Tiny cells at the base of the ocean's food webs.  

PubMed

Phytoplankton in the size range 5-100 ?m was originally thought to be the primary source of food for most life in the sea. However, smaller planktonic microbes, down to 0.2 ?m in size, have been the focus of intensive investigation by marine scientists during the past two decades. These microbes attain high abundance and biomass in all parts of the world ocean. They include non-photosynthesizing bacteria, at least two types of photosynthesizing prokaryotes, and eukaryotic phototrophs. The new information has resulted in a greatly revised concept of how pelagic ecosystems in both marine and freshwater environments function. The original idea of a basically linear food chain from diatoms to copepods to fish has given way to an extremely complex model of trophic interactions within a microbial food web, which supports metazoan food webs via biomass production of both heterotrophic and autotrophic cells. PMID:21232423

Sherr, E B; Sherr, B F

1991-02-01

270

Sardine cycles, krill declines, and locust plagues: revisiting 'wasp-waist' food webs.  

PubMed

'Wasp-waist' systems are dominated by a mid trophic-level species that is thought to exert top-down control on its food and bottom-up control on its predators. Sardines, anchovy, and Antarctic krill are suggested examples, and here we use locusts to explore whether the wasp-waist concept also applies on land. These examples also display the traits of mobile aggregations and dietary diversity, which help to reduce the foraging footprint from their large, localised biomasses. This suggests that top-down control on their food operates at local aggregation scales and not at wider scales suggested by the original definition of wasp-waist. With this modification, the wasp-waist framework can cross-fertilise marine and terrestrial approaches, revealing how seemingly disparate but economically important systems operate. PMID:24755099

Atkinson, Angus; Hill, Simeon L; Barange, Manuel; Pakhomov, Evgeny A; Raubenheimer, David; Schmidt, Katrin; Simpson, Stephen J; Reiss, Christian

2014-06-01

271

A standard protocol for stable isotope analysis of zooplankton in aquatic food web research using mass balance correction models  

Microsoft Academic Search

Stable isotope analysis has become a crucial tool for aquatic food web ecologists, but a lack of methodological standardization hinders comparisons between studies. One methodological inconsistency in stable isotope food web research is the decision whether to extract lipids before stable isotope analysis. The depletion in zooplankton stable carbon isotope values (d13C) due to fatty acid content and the accuracy

Peter M. Smyntek; Mark A. Teece; Kimberly L. Schulz; Stephen J. Thackeray

2007-01-01

272

Analogous aquatic and terrestrial food webs in the high Arctic: The structuring force of a harsh climate  

Microsoft Academic Search

Understanding food web structure and dynamics remains a central theme in ecology. Whilst differences between aquatic and terrestrial food webs have been the focus of several studies, we aim to reveal similarities where abiotic conditions are particularly extreme such as in the high Arctic. We propose that here, the combination of a short growing season, low temperature and low light,

René van der Wal; Dag O. Hessen

2009-01-01

273

Spatial Structure and Biophysical Coupling in Pelagic Food Webs connecting the Nearshore Shunt and Offshore Desert with the Laser  

E-print Network

Spatial Structure and Biophysical Coupling in Pelagic Food Webs­ connecting the Nearshore Shunt and Offshore Desert with the Laser Plankton Survey System (LPSS) Primary Investigator: Hank Vanderploeg - NOAA It is increasingly obvious from our projects in Lake Michigan and Erie that spatial coupling in pelagic food webs

274

Manipulations of a microbial based soil food web at two arctic sites — evidence of species redundancy among the nematode fauna?  

Microsoft Academic Search

Nutrient limitation is a major factor influencing ecosystem processes in arctic soils, but knowledge on the decomposer food web interactions and their effects on nutrient cycling is scarce. Manipulations of the soil food web were carried out at two contrasting subarctic sites, a low altitude heath and a high altitude fellfield. The amount of nutrients and energy in the soil

Liliane Ruess; Inger K. Schmidt; Anders Michelsen; Sven Jonasson

2001-01-01

275

The influence of seabird nutrient enrichment and grazing on the structure and function of island soil food webs  

Microsoft Academic Search

Marine inputs from seabirds (in the form of guano) to terrestrial coastal communities play an important role in supporting aboveground food webs. However, little is known about the importance of seabird-derived nutrient inputs for belowground food webs and their function relative to other factors that regulate belowground communities. Here, we tested the relative importance of nutrient enrichment from seabirds and

Daniel G. Wright; René van der Wal; Sarah Wanless; Richard D. Bardgett

2010-01-01

276

Modelling C and N mineralisation in soil food webs during secondary succession on ex-arable land  

Microsoft Academic Search

The rate of secondary succession after land abandonment depends on the interplay between aboveground and belowground processes. Changes in vegetation composition lead to altered amounts and composition of soil organic matter (SOM) with consequences for the abundance and functioning of the soil food web. In turn, soil food web structure determines the mineralisation rate of nutrients that can be taken

Remko Holtkamp; Annemieke van der Wal; Paul Kardol; Wim H. van der Putten; Peter C. de Ruiter; Stefan C. Dekker

2011-01-01

277

Divergent composition but similar function of soil food webs beneath individual plants: plant species and community effects  

Microsoft Academic Search

Soils are extremely rich in biodiversity, and soil organisms play pivotal roles in supporting terrestrial life, but the role that individual plants and plant communities play in influencing the diversity and functioning of soil food webs remains highly debated. Plants, as primary producers and providers of resources to the soil food web, are of vital importance for the composition, structure,

T. Martijn Bezemer; Michelle Fountain; José Barea; Soren Christensen; Stefan Dekker; Henk Duyts; Ralf van Hal; Jeff Harvey; Katarina Hedlund; Mark Maraun; Juha Mikola; Alexander Mladenov; Christophe Robin; Peter de Ruiter; Stefan Scheu; Heikki Setälä; Petr Šmilauer; Wim van der Putten

2010-01-01

278

Carbon fluxes in soil food webs of increasing complexity revealed by 14C labelling and 13C natural abundance  

Microsoft Academic Search

Soil food webs are mainly based on three primary carbon (C) sources: root exudates, litter, and recalcitrant soil organic matter (SOM). These C sources vary in their availability and accessibility to soil organisms, which could lead to different pathways in soil food webs. The presence of three C isotopes (12C, 13C and 14C) offers an unique opportunity to investigate all

Andrea Ruf; Yakov Kuzyakov; Olga Lopatovskaya

2006-01-01

279

Effects of agricultural management on nematode–mite assemblages: Soil food web indices as predictors of mite community composition  

Microsoft Academic Search

Biological indicators based on abundances of soil organisms are powerful tools for inferring functional and diversity changes in soils affected by agricultural perturbations. Field plots, combining organic and conventional practices with no tillage, conservation tillage and standard tillage maintained different nematode assemblages and soil food webs. Soil food web indices based on nematode assemblages were reliable predictors of the trophic

Sara Sánchez-Moreno; Nicole L. Nicola; Howard Ferris; Frank G. Zalom

2009-01-01

280

Nematode diversity and food web condition in heavy metal polluted soils in a river basin in southern Spain  

Microsoft Academic Search

Effects of heavy metal pollution on the nematode community and the soil food web were assessed (June 2000 to February 2002) by using nematode community composition, functional guild abundances and diversity, maturity and soil food web indices in polluted soils in a river basin in southern Spain. Soil content of Pb, Ni, Cu and Zn, soil pH and soil texture

S. Sánchez-Moreno; A. Navas

2007-01-01

281

Nutrient-limited food webs with up to three trophic levels: Feasibility, stability, assembly rules, and effects of nutrient enrichment  

Microsoft Academic Search

Community structure is controlled, among multiple factors, by competition and predation. Using the R* rule and graphical analysis, we analyse here the feasibility, stability and assembly rules of resource-based food webs with up to three trophic levels. In particular, we show that (1) the stability of a food web with two plants and two generalist herbivores does not require that

Florence D. Hulot; Michel Loreau

2006-01-01

282

Exploring the effects of multiple management objectives and exotic species on great lakes food webs and contaminant dynamics  

Microsoft Academic Search

A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter ( Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will decrease by

Thomas D. Fontaine; Donald J. Stewart

1992-01-01

283

Theoretical Population Biology 67 (2005) 8599 Adaptive omnivory and species coexistence in tri-trophic food webs  

E-print Network

-trophic food webs Vlastimil Kr ivana,Ã?, Sebastian Diehlb a Department of Theoretical Biology, Institute for intermediate consumers. r 2004 Elsevier Inc. All rights reserved. Keywords: Omnivory; Intraguild predation; Diet rule; Optimal foraging; Population dynamics; Food webs 1. Introduction Omnivory, the consumption

Krivan, Vlastimil

284

Impact of Fertilization on a Salt Marsh Food Web in Georgia Caroline R. McFarlin & J. Stephen Brewer &  

E-print Network

Impact of Fertilization on a Salt Marsh Food Web in Georgia Caroline R. McFarlin & J. Stephen 2008 Abstract We examined the response of a salt marsh food web to increases in nutrients at 19 coastal species. Fertilization increased Spartina cover, height, and biomass and Juncus height, but led

Pennings, Steven C.

285

Food-web inferences of stable isotope spatial patterns in copepods and yellowfin tuna in the pelagic eastern Pacific Ocean  

E-print Network

Food-web inferences of stable isotope spatial patterns in copepods and yellowfin tuna inshore­offshore, east to west gradient in yellowfin tuna trophic position was corroborated using compound by the distribution of yellowfin tuna of different sizes, by seasonal variability at the base of the food web

Hawai'i at Manoa, University of

286

Towards a mechanistic understanding of temperature and enrichment effects on species interaction strength, omnivory and food-web structure.  

PubMed

Revealing the links between species functional traits, interaction strength and food-web structure is of paramount importance for understanding and predicting the relationships between food-web diversity and stability in a rapidly changing world. However, little is known about the interactive effects of environmental perturbations on individual species, trophic interactions and ecosystem functioning. Here, we combined modelling and laboratory experiments to investigate the effects of warming and enrichment on a terrestrial tritrophic system. We found that the food-web structure is highly variable and switches between exploitative competition and omnivory depending on the effects of temperature and enrichment on foraging behaviour and species interaction strength. Our model contributes to identifying the mechanisms that explain how environmental effects cascade through the food web and influence its topology. We conclude that considering environmental factors and flexible food-web structure is crucial to improve our ability to predict the impacts of global changes on ecosystem diversity and stability. PMID:24751223

Sentis, Arnaud; Hemptinne, Jean-Louis; Brodeur, Jacques

2014-07-01

287

Food web interactions and nutrients dynamics in polyculture ponds  

Microsoft Academic Search

Artificial feed and fertilizers are the main sources of nutrients supporting fish growth in aquaculture ponds. The majority of the added nutrients are lost to the sediment, where they are no longer available for natural food production. By increasing resuspension of the sediment through the introduction of benthivorous fish, nutrient loss may be reduced, because of the re-mobilisation of nutrients

M. M. Rahman

2006-01-01

288

Depth-specific Analyses of the Lake Superior Food Web  

EPA Science Inventory

Characteristics of large, deep aquatic systems include depth gradients in community composition, in the quality and distribution of food resources, and in the strategies that organisms use to obtain their nutrition. In Lake Superior, nearshore communities that rely upon a combina...

289

Applying stable isotopes to examine food-web structure: an overview of analytical tools.  

PubMed

Stable isotope analysis has emerged as one of the primary means for examining the structure and dynamics of food webs, and numerous analytical approaches are now commonly used in the field. Techniques range from simple, qualitative inferences based on the isotopic niche, to Bayesian mixing models that can be used to characterize food-web structure at multiple hierarchical levels. We provide a comprehensive review of these techniques, and thus a single reference source to help identify the most useful approaches to apply to a given data set. We structure the review around four general questions: (1) what is the trophic position of an organism in a food web?; (2) which resource pools support consumers?; (3) what additional information does relative position of consumers in isotopic space reveal about food-web structure?; and (4) what is the degree of trophic variability at the intrapopulation level? For each general question, we detail different approaches that have been applied, discussing the strengths and weaknesses of each. We conclude with a set of suggestions that transcend individual analytical approaches, and provide guidance for future applications in the field. PMID:22051097

Layman, Craig A; Araujo, Marcio S; Boucek, Ross; Hammerschlag-Peyer, Caroline M; Harrison, Elizabeth; Jud, Zachary R; Matich, Philip; Rosenblatt, Adam E; Vaudo, Jeremy J; Yeager, Lauren A; Post, David M; Bearhop, Stuart

2012-08-01

290

Reciprocal diversification in a complex plant-herbivore-parasitoid food web  

Microsoft Academic Search

BACKGROUND: Plants, plant-feeding insects, and insect parasitoids form some of the most complex and species-rich food webs. According to the classic escape-and-radiate (EAR) hypothesis, these hyperdiverse communities result from coevolutionary arms races consisting of successive cycles of enemy escape, radiation, and colonization by new enemy lineages. It has also been suggested that \\

Tommi Nyman; Folmer Bokma; Jens-Peter Kopelke

2007-01-01

291

SHIFTS BETWEEN PERIPHYTON-AND PHYTOPLANKTON-BASED FOOD WEBS IN GREAT LAKES COASTAL WETLANDS  

EPA Science Inventory

Numerous studies have revealed the importance of algae as an energetic base for wetland food webs. Earlier carbon and nitrogen stable isotope analyses in a Lake Superior coastal wetland (Allouez Bay, WI) indicated that, despite the large amount of vascular plant biobass present, ...

292

Increasing isolation reduces predator:prey species richness ratios in aquatic food webs  

Microsoft Academic Search

The number of species that live in a habitat typically declines as that habitat becomes more isolated. However, the influence of habitat isolation on patterns of food web structure, in particular the ratio of predator to prey species richness, is less well understood. We placed aquatic mesocosms at varying distances from ponds that acted as sources of potential colonists; then

Rachel S. Shulman; Jonathan M. Chase

2007-01-01

293

Food-web structure and network theory: The role of connectance and size  

Microsoft Academic Search

Networks from a wide range of physical, biological, and social systems have been recently described as ''small-world'' and ''scale- free.'' However, studies disagree whether ecological networks called food webs possess the characteristic path lengths, clustering coefficients, and degree distributions required for membership in these classes of networks. Our analysis suggests that the disagree- ments are based on selective use of

Jennifer A. Dunne; Richard J. Williams; Neo D. Martinez

2002-01-01

294

Contribution of Allochthonous Carbon Subsidies to the Minho Estuary Lower Food Web  

EPA Science Inventory

To study the contribution of autochthonous and allochthonous organic matter (OM) sources fuelling the lower food web in Minho River estuary (N-Portugal, Europe), we characterized the carbon (?13C) and nitrogen (?15N) stable isotope ratios of zooplankton and their potential OM sou...

295

Structural and functional succession in the nematode fauna of a soil food web  

Microsoft Academic Search

Soil microplots were amended with organic materials of varying nature and complexity but providing similar amounts of carbon. Materials were either placed on the soil surface or incorporated. Unamended and mineral fertilizer control plots were established. Plots were maintained vegetation-free so that the food web activity was fueled by resident soil organic matter and the input material. Enrichment-opportunist bacterivore nematodes

H. Ferris; M. M. Matute

2003-01-01

296

Soil processes are not influenced by the functional complexity of soil decomposer food webs under disturbance  

Microsoft Academic Search

A 3yr experiment, using field lysimeters with seedlings of Scots pine (Pinus sylvestris) growing in raw humus, was established to study how functional complexity of the soil decomposer food web affects ecosystem functioning. The functional complexity of decomposer system was manipulated by (1) allowing either microfauna (fine mesh) or microfauna+mesofauna (coarse mesh) to enter the initially defaunated systems, and (2)

Mira Liiri; Heikki Setälä; Jari Haimi; Taina Pennanen; Hannu Fritze

2002-01-01

297

Identification of Bacterial Micropredators Distinctively Active in a Soil Microbial Food Web  

Microsoft Academic Search

The understanding of microbial interactions and trophic networks is a prerequisite for the elucidation of the turnover and transformation of organic materials in soils. To elucidate the incorporation of biomass carbon into a soil microbial food web, we added 13C-labeled Escherichia coli biomass to an agricultural soil and identified those indigenous microbes that were specifically active in its mineralization and

Tillmann Lueders; Reimo Kindler; Anja Miltner; Michael W. Friedrich; Matthias Kaestner

2006-01-01

298

Effects of grassland plant species diversity on soil animal food web components  

Microsoft Academic Search

To investigate the feedback of the plant community to the soil food web we set up a greenhouse experiment manipulating both (1) the diversity of a model grassland community, consisting of 43 common plant species of a Central European Arrhenatherion grassland following \\

Alexandru Milcu; Stephan Partsch; Stefan Scheu

299

Linking soil properties and nematode community composition: effects of soil management on soil food webs  

Microsoft Academic Search

Summary - The purported benefits of conservation tillage and continuous cropping in agricultural systems include enhancement of soil ecosystem functions to improve nutrient availability to crops and soil C storage. Studies relating soil management to community structure allow the development of bioindicators and the assessment of the consequences of management practices on the soil food web. During one year (December

Sara Sánchez-Moreno; Hideomi Minoshima; Howard Ferris; Louise E. Jackson

2006-01-01

300

Stoichiometric Constraints on Food-Web Dynamics: A Whole-Lake  

E-print Network

, microconsumer abundance, and concentration and carbon­phospho- rus (C:P) ratio of suspended particulate matter of existing food-web theory, such as the idea of cascading trophic interactions (CTI). While Daphnia biomass in bacterial biomass occurred in either lake. However, total concentrations of particulate matter appeared

Sterner, Robert W.

301

From the Top of the World...to the Bottom of the Food Web  

NSDL National Science Digital Library

This resource, by the Bigelow Laboratory, is designed to help teachers and students discover linkages among marine ecology, phytoplankton, the behavior of light at the ocean surface, and satellite-derived ocean color data. On-line standards, based educational activities, explore the topics of phytoplankton, food webs, and algal blooms using microscopy and remote sensing data.

Sciences, Bigelow L.

302

Structure and function Many scientists use food webs to portray ecolo-  

E-print Network

and change food-web structure and function. These include biological stoichiometry, body that there is something more complex than the genome currently under study in modern biology. Nevertheless, we propose do this yourself on the Internet at www.genome.ad. jp/kegg/). Yet more magnification, for example

Hessen, Dag Olav

303

Salmon Life Histories, Habitats, and Food Webs in the Columbia River Estuary  

E-print Network

Salmon Life Histories, Habitats, and Food Webs in the Columbia River Estuary Daniel J. Bottom NOAA management efforts in the Columbia River estuary on behalf of salmon: (1) the estuary is irrelevant stocks throughout the Columbia River Basin. The Columbia River estuary contributes to salmon life history

304

Seasonal Variation in Food Web Composition and Structure in a Temperate Tidal Estuary  

Microsoft Academic Search

Seasonal variation in aquatic food web structure at Mad Island Marsh, Matagorda Bay, Texas, was examined using dietary information obtained from the analysis of gut contents from large samples of fish and crustacean specimens. Unique aspects of this study include the use of large samples of consumer gut contents (n 5 6,452), long-term sampling (bimonthly surveys over 18 mo), and

S. AKIN; K. O. WINEMILLER

2006-01-01

305

Food web structure and trophic interactions of the tropical highland lake Hayq, Ethiopia  

Microsoft Academic Search

We generated a mass-balance model to figure out the food web structure and trophic interactions of the major functional groups of the Ethiopian highland Lake Hayq. Moreover, the study lay down a baseline data for future ecosystem-based investigations and management activities. Extensive data collection has been taken place between October 2007 and May 2009. Ecotrophic efficiency (EE) of several functional

Tadesse Fetahi; Michael Schagerl; Seyoum Mengistou; Simone Libralato

2011-01-01

306

Mercury biomagnification through food webs is affected by physical and chemical characteristics of lakes.  

PubMed

Mercury (Hg) contamination in aquatic systems remains a global concern because the organic form, methyl Hg (MeHg), can biomagnify to harmful concentrations in fish, fish-eating wildlife, and humans. Food web transfer of MeHg has been explored using models of log MeHg versus relative trophic position (nitrogen isotopes, ?(15)N), but regression slopes vary across systems for unknown reasons. In this study, MeHg biomagnification was determined for 11 lake food webs in Kejimkujik National Park, Nova Scotia, Canada, and compared to physical and chemical lake characteristics using principal component and multiple regression analyses. MeHg biomagnification (regression slopes of log MeHg versus baseline-adjusted ?(15)N for fishes and invertebrates) varied significantly across lakes and was higher in systems with lower aqueous nutrient/MeHg/chloride scores. This is one of the largest, consistent data sets available on MeHg biomagnification through temperate lake food webs and the first study to use a principal component and multiple regression approach to understand how lake chemical and physical characteristics interact to affect biomagnification among systems. Overall, our results show that the magnitude of MeHg biomagnification through lake food webs is related to the chemical and physical characteristics of the systems, but the underlying mechanisms warrant further investigation. PMID:24099312

Clayden, Meredith G; Kidd, Karen A; Wyn, Brianna; Kirk, Jane L; Muir, Derek C G; O'Driscoll, Nelson J

2013-11-01

307

Field evidence of trait-mediated indirect interactions in a rocky intertidal food web  

E-print Network

-mediated interactions. On rocky intertidal shores in New England, green crab (Carcinus maenas) predation is thought (Littorina littorea). We found, however, that risk cues from green crabs can dramatically suppress snail, crab predation, food web, indirect interactions, Littorina littorea, risk cues, rocky intertidal zone

Bertness, Mark D.

308

Estuarine Microbial Food Web Patterns in a Lake Erie Coastal Wetland  

Microsoft Academic Search

Composition and distribution of planktonic protists were examined relative to microbial food web dynamics (growth, grazing, and nitrogen cycling rates) at the Old Woman Creek (OWC) National Estuarine Research Reserve during an episodic storm event in July 2003. More than 150 protistan taxa were identified based on morphology. Species richness and microbial biomass measured via microscopy and flow cytometry increased

P. J. Lavrentyev; M. J. McCarthy; D. M. Klarer; F. Jochem; W. S. Gardner

2004-01-01

309

Food web interactions between larval bluegill ( Lepomis macrochirus ) and exotic zebra mussels ( Dreissena polymorpha )  

Microsoft Academic Search

Food web interactions between native larval bluegill (Lepomis macrochirus), exotic invasive zebra mussels (Dreissena polymorpha), and zooplankton were examined with a mesocosm experiment. Hatchling larval bluegill col- lected from nests were reared in the presence of size-structured populations of zebra mussels in 1500-L limnocorrals suspended in an artificial pond for 2 weeks. Chlorophyll a, other limnological variables, and zooplankton abundance

David F. Raikow

2004-01-01

310

Climatic seasonality may affect ecological network structure: food webs and mutualistic networks.  

PubMed

Ecological networks exhibit non-random structural patterns, such as modularity and nestedness, which determine ecosystem stability with species diversity and connectance. Such structure-stability relationships are well known. However, another important perspective is less well understood: the relationship between the environment and structure. Inspired by theoretical studies that suggest that network structure can change due to environmental variability, we collected data on a number of empirical food webs and mutualistic networks and evaluated the effect of climatic seasonality on ecological network structure. As expected, we found that climatic seasonality affects ecological network structure. In particular, an increase in modularity due to climatic seasonality was observed in food webs; however, it is debatable whether this occurs in mutualistic networks. Interestingly, the type of climatic seasonality that affects network structure differs with ecosystem type. Rainfall and temperature seasonality influence freshwater food webs and mutualistic networks, respectively; food webs are smaller, and more modular, with increasing rainfall seasonality. Mutualistic networks exhibit a higher diversity (particularly of animals) with increasing temperature seasonality. These results confirm the theoretical prediction that the stability increases with greater perturbation. Although these results are still debatable because of several limitations in the data analysis, they may enhance our understanding of environment-structure relationships. PMID:24907523

Takemoto, Kazuhiro; Kanamaru, Saori; Feng, Wenfeng

2014-07-01

311

Advances in molecular ecology: tracking trophic links through predator-prey food-webs  

Microsoft Academic Search

Summary 1. It is not always possible to track trophic interactions between predators and prey by direct observation. This is especially true when observing small or elusive animals with cryptic food-web ecology. Gut and\\/or faecal analysis can sometimes allow prey remains to be identified visually but is only possible when a component of the diet is resistant to digestion. In

S. K. SHEPPARD; J. D. HARWOOD

2005-01-01

312

Linking Landscapes and Food Webs: Effects of Omnivorous Fish and Watersheds on Reservoir Ecosystems  

NSDL National Science Digital Library

This peer-reviewed article from BioScience is the effects of omnivorous fish and watersheds on reservoirs. Ecologists increasingly recognize the need to understand how landscapes and food webs interact. Reservoir ecosystems are heavily subsidized by nutrients and detritus from surrounding watersheds, and often contain abundant populations of gizzard shad, an omnivorous fish that consumes plankton and detritus. Gizzard shad link terrestrial landscapes and pelagic reservoir food webs by consuming detritus, translocating nutrients from sediment detritus to the water column, and consuming zooplankton. The abundance of gizzard shad increases with watershed agriculturalization, most likely through a variety of mechanisms operating on larval and adult life stages. Gizzard shad have myriad effects on reservoirs, including impacts on nutrients, phytoplankton, zooplankton, and fish, and many of their effects vary with ecosystem productivity (i.e., watershed land use). Interactive feedbacks among watersheds, gizzard shad populations, and reservoir food webs operate to maintain dominance of gizzard shad in highly productive systems. Thus, effective stewardship of reservoir ecosystems must incorporate both watershed and food-web perspectives.

MICHAEL J. VANNI, KRISTIN K. AREND, MARY T. BREMIGAN, DAVID B. BUNNELL, JAMES E. GARVEY, MARÃÂA J. GONZÃÂLEZ, WILLIAM H. RENWICK, PATRICIA A. SORANNO, and ROY A. STEIN (;)

2005-02-01

313

Productivity and food web structure: association between productivity and link richness among top predators  

Microsoft Academic Search

Summary 1. A prime goal in ecology is to understand the consequences of different productivity levels on system structure and stability. The number of trophic connections per species is a main parameter of food web structure often associated with total number of species and disturbance but not with productivity. We analyse the association between number of trophic connections and productivity

MATÍAS ARIM; FABIAN M. JAKSIC

314

Preliminary Mass-Balance Food Web Model of the Eastern Chukchi Sea.  

National Technical Information Service (NTIS)

A preliminary mass-balance food web model was developed for the eastern Chukchi Sea continental shelf, describing the trophic structure and function of this ecosystem. The model was developed with the Ecopath framework and provides an annual snapshot of t...

G. A. Whitehouse

2013-01-01

315

Combined impacts of global warming and pollution: impacts on food web structure and ecosystem function  

Microsoft Academic Search

Effects of global species loss on ecosystem function have traditionally been extrapolated from studies which investigate the effect of random species loss or addition. Real species loss is highly patterned and clumped according to trophic position, taxonomic relatedness and interconnectedness with the remainder of the food web. Using pond microcosms, I evoked a realistic pattern of species loss using toxins

R. M. Thompson

2005-01-01

316

Pelagic food webs and eutrophication of coastal waters: Impact of grazers on algal communities  

Microsoft Academic Search

This review considers theoretical and empirical aspects of the role of grazers in the pelagic food web. We discuss how grazers may affect eutrophication development in coastal waters both through the direct effects of differential prey selectivity on the composition of the algal community, and through the indirect effects of nutrient sequestration and regeneration on the pelagic nutrient regime. We

Gismervik Ingrid; Tom Andersen; Olav Vadstein

1996-01-01

317

Seasonality of stable carbon isotopes within the pelagic food web of Lake Kinneret  

Microsoft Academic Search

Seasonal variations in the carbon isotope composition of components of the pelagic food web in Lake Kinneret were recorded and compared with those recorded for bulk plankton from the lake in the early 1970s. Individual planktonic components as well as bulk plankton were isotopically lightest shortly after overturn in January and heaviest in May, after the peak of the annual

TAMAR ZOHARY; JONATHAN EREZ; Moshe Gophenl; ILANA BERMAN-FRANK; MARIANA STILLER

1994-01-01

318

Effects of Diporeia Declines on Fish Diet, Growth and Food Web Dynamics in Southeast Lake Michigan  

E-print Network

Effects of Diporeia Declines on Fish Diet, Growth and Food Web Dynamics in Southeast Lake Michigan Pothoven - NOAA GLERL Overview Diporeia, the dominant benthic macroinvertebrate in offshore waters- 50 m, and 51-90 m between 1993 and 2002. The declines of Diporeia have been attributed to the spread

319

The role of a water bug, Sigara striata, in freshwater food webs  

PubMed Central

Freshwater food webs are dominated by aquatic invertebrates whose trophic relationships are often poorly known. Here, I used laboratory experiments to study the role of a water bug, Sigara striata, as a potential predator and prey in food webs of stagnant waters. Multiple-choice predation experiment revealed that Sigara, which had been considered mostly herbivorous, also consumed larvae of Chironomus midges. Because they often occur in high densities and are among the most ubiquitous aquatic insects, Sigara water bugs may be important predators in fresh waters. A second experiment tested the role of Sigara as a potential prey for 13 common invertebrate predators. Mortality of Sigara inflicted by different predators varied widely, especially depending on body mass, foraging mode (ambush/searching) and feeding mode (chewing/suctorial) of the predators. Sigara was highly vulnerable to ambush predators, while searching predators caused on average 8.1 times lower mortality of Sigara. Additionally, suctorial predators consumed on average 6.6 times more Sigara individuals than chewing predators, which supports previous results hinting on potentially different predation pressures of these two types of predators on prey populations. The importance of these two foraging-related traits demonstrates the need to move from body mass based to multiple trait based descriptions of food web structure. Overall, the results suggests that detailed experimental studies of common but insufficiently known species can significantly enhance our understanding of food web structure. PMID:24883250

2014-01-01

320

Linking Food Webs and Biogeochemical Processes in Wetlands: Insights From Sulfur Isotopes  

Microsoft Academic Search

To better understand the transfer of nutrients into prairie wetland food webs we have investigated the cycling of S (via S isotope systematics and geochemistry) in a prairie wetland landscape by characterizing sources (ground water, interstitial water, surface water) and processes in a small catchment comprised of four wetlands in eastern South Dakota. We focused on S to derive process

C. A. Stricker; G. R. Guntenspergen; R. O. Rye

2005-01-01

321

Effects of light reduction on food webs and associated ecosystem services of Yaquina Bay  

EPA Science Inventory

Reduced water clarity can affect estuarine primary production but little is known of its subsequent effects to consumer guilds or ecosystem services. We investigated those effects using inverse analysis of modeled food webs of the lower (polyhaline) and upper (mesohaline) reache...

322

Ecological community description using the food web, species abundance, and body size  

E-print Network

are not aware of any single community for which all of these relationships have been analyzed simultaneously sizes, and species abundances. A food web (4) is a directed graph or flow diagram. Each node is labeled on Tuesday Lake from 1984 (Fig. 1). This brief report focuses on the trivariate relationships (last line

Cohen, Joel E.

323

Developing a broader scientific foundation for river restoration: Columbia River food webs  

E-print Network

, OR 97331; n US Department of Agriculture Forest Service, Rocky Mountain Research Station, Seeley Lake, MT for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure--without explicitly considering food webs--has been less successful

324

FOOD WEB STRUCTURE AND TROPHIC DYNAMICS OF A SUBTROPICAL PLANKTON COMMUNITY, WITH AN EMPHASIS ON  

E-print Network

FOOD WEB STRUCTURE AND TROPHIC DYNAMICS OF A SUBTROPICAL PLANKTON COMMUNITY, WITH AN EMPHASIS of a subtropical plankton community were investigated to assess the ecological importance of metazoan organisms community. The feeding capabilities of warrn- water appendicularians on natural plankton prey were

Luther, Douglas S.

325

NEARSHORE-OFFSHORE PATTERNS IN FOOD WEB CHARACTERISTICS IN LAKE SUPERIOR  

EPA Science Inventory

We are exploring the use of food web properties to characterize nearshore and offshore habitats in the Great lakes. We analyzed the stable isotope signatures of benthos (predominantly Diporeia hoyi) and plankton from Lake Superior habitats ranging from 20m to 300m depth......

326

From Ontology Selection and Semantic Web to an Integrated Information System for Food-  

E-print Network

From Ontology Selection and Semantic Web to an Integrated Information System for Food- borne and information); c) integration of collected pa- thogen profiling data, Foodrisk.org (http and other cutting-edge "omics" technolo- gies have dramatically improved our ability to rapidly determine

Peng, Yun

327

Propagation of Cascades in Complex Networks: From Supply Chains to Food Webs  

Microsoft Academic Search

A general theory of top-down cascades in complex networks is described which explains two similar types of perturbation amplifications in the complex networks of business supply chains (the `bullwhip effect') and ecological food webs (trophic cascades). The dependence of the strength of the effects on the interaction strength and covariance in the dynamics as well as the graph structure allows

Reginald D. Smith

2011-01-01

328

Seeking Emotional Involvement in Science Education: Food-Chains and Webs.  

ERIC Educational Resources Information Center

Documents a study of emotion in two grade 8 science classrooms. Describes a lesson on food-chains and webs designed with a conceptual and an emotional agenda. Discusses issues of emotion, sensation and relevance in science teaching. (Author/MM)

Alsop, Steve

2001-01-01

329

Comparing energetic and dynamic descriptions of a single food web linkage  

E-print Network

194 Comparing energetic and dynamic descriptions of a single food web linkage Christopher T. Energetic and dynamic metrics gave different descriptions of the linkage strength from the perspective a strong linkage because smelt extirpated cisco, but the energetic metric indicated a weak linkage because

Vander Zanden, Jake

330

Food-Web Structure in Relation to Environmental Gradients and Predator-Prey Ratios in Tank-Bromeliad Ecosystems  

PubMed Central

Little is known of how linkage patterns between species change along environmental gradients. The small, spatially discrete food webs inhabiting tank-bromeliads provide an excellent opportunity to analyse patterns of community diversity and food-web topology (connectance, linkage density, nestedness) in relation to key environmental variables (habitat size, detrital resource, incident radiation) and predators:prey ratios. We sampled 365 bromeliads in a wide range of understorey environments in French Guiana and used gut contents of invertebrates to draw the corresponding 365 connectance webs. At the bromeliad scale, habitat size (water volume) determined the number of species that constitute food-web nodes, the proportion of predators, and food-web topology. The number of species as well as the proportion of predators within bromeliads declined from open to forested habitats, where the volume of water collected by bromeliads was generally lower because of rainfall interception by the canopy. A core group of microorganisms and generalist detritivores remained relatively constant across environments. This suggests that (i) a highly-connected core ensures food-web stability and key ecosystem functions across environments, and (ii) larger deviations in food-web structures can be expected following disturbance if detritivores share traits that determine responses to environmental changes. While linkage density and nestedness were lower in bromeliads in the forest than in open areas, experiments are needed to confirm a trend for lower food-web stability in the understorey of primary forests. PMID:23977128

Dezerald, Olivier; Leroy, Celine; Corbara, Bruno; Carrias, Jean-Francois; Pelozuelo, Laurent; Dejean, Alain; Cereghino, Regis

2013-01-01

331

Carbon flows in the benthic food web at the deep-sea observatory HAUSGARTEN (Fram Strait)  

NASA Astrophysics Data System (ADS)

The HAUSGARTEN observatory is located in the eastern Fram Strait (Arctic Ocean) and used as long-term monitoring site to follow changes in the Arctic benthic ecosystem. Linear inverse modelling was applied to decipher carbon flows among the compartments of the benthic food web at the central HAUSGARTEN station (2500 m) based on an empirical data set consisting of data on biomass, prokaryote production, total carbon deposition and community respiration. The model resolved 99 carbon flows among 4 abiotic and 10 biotic compartments, ranging from prokaryotes up to megafauna. Total carbon input was 3.78±0.31 mmol C m -2 d -1, which is a comparatively small fraction of total primary production in the area. The community respiration of 3.26±0.20 mmol C m -2 d -1 is dominated by prokaryotes (93%) and has lower contributions from surface-deposit feeding macro- (1.7%) and suspension feeding megafauna (1.9%), whereas contributions from nematode and other macro- and megabenthic compartments were limited to <1%. The high prokaryotic contribution to carbon processing suggests that functioning of the benthic food web at the central HAUSGARTEN station is comparable to abyssal plain sediments that are characterised by strong energy limitation. Faunal diet compositions suggest that labile detritus is important for deposit-feeding nematodes (24% of their diet) and surface-deposit feeding macrofauna (˜44%), but that semi-labile detritus is more important in the diets of deposit-feeding macro- and megafauna. Dependency indices on these food sources were also calculated as these integrate direct (i.e. direct grazing and predator-prey interactions) and indirect (i.e. longer loops in the food web) pathways in the food web. Projected sea-ice retreats for the Arctic Ocean typically anticipate a decrease in the labile detritus flux to the already food-limited benthic food web. The dependency indices indicate that faunal compartments depend similarly on labile and semi-labile detritus, which suggests that the benthic biota may be more sensitive to changes in labile detritus inputs than when assessed from diet composition alone. Species-specific responses to different types of labile detritus inputs, e.g. pelagic algae versus sympagic algae, however, are presently unknown and are needed to assess the vulnerability of individual components of the benthic food web.

van Oevelen, Dick; Bergmann, Melanie; Soetaert, Karline; Bauerfeind, Eduard; Hasemann, Christiane; Klages, Michael; Schewe, Ingo; Soltwedel, Thomas; Budaeva, Nataliya E.

2011-11-01

332

Nearshore energy subsidies support Lake Michigan fishes and invertebrates following major changes in food web structure.  

PubMed

Aquatic food webs that incorporate multiple energy channels (e.g., nearshore benthic and pelagic) with varying productivity and turnover rates convey stability to biological communities by providing independent energy sources. Within the Lake Michigan food web, invasive dreissenid mussels have caused rapid changes to food web structure and potentially altered the channels through which consumers acquire energy. We used stable C and N isotopes to determine how Lake Michigan food web structure has changed in the past decade, coincident with the expansion of dreissenid mussels, decreased pelagic phytoplankton production, and increased nearshore benthic algal production. Fish and invertebrate samples collected from sites around Lake Michigan were analyzed to determine taxa-specific 13C:12C (delta13C) and 15N:14N (delta15N) ratios. Sampling took place during two distinct periods, 2002-2003 and 2010-2012, that spanned the period of dreissenid expansion, and included nearshore, pelagic and profundal fish and invertebrate taxa. The magnitude and direction of the delta13C shift indicated significantly greater reliance upon nearshore benthic energy sources among nearly all fish taxa as well as profundal invertebrates following dreissenid expansion. Although the mechanisms underlying this delta13C shift likely varied among species, possible causes include the transport of benthic algal production to offshore waters and increased feeding on nearshore prey items by pelagic and profundal species. delta15N shifts were more variable and of smaller magnitude across taxa, although declines in delta15N among some pelagic fishes suggest a shift to alternative prey resources. Lake Michigan fishes and invertebrates appear to have responded to dreissenid-induced changes in nutrient and energy pathways by switching from pelagic to alternative nearshore energy subsidies. Although large shifts in energy allocation (i.e., pelagic to nearshore benthic) resulting from invasive species appear to affect total production at upper trophic levels, changes in trophic structure and utilization of novel energy pathways may help to stabilize food webs following species invasions. PMID:25000756

Turschak, Benjamin A; Bunnell, David; Czesny, Sergiusz; Höök, Tomas O; Janssen, John; Warner, David; Bootsma, Harvey A

2014-05-01

333

Biochemical tracers reveal intra-specific differences in the food webs utilized by individual seabirds.  

PubMed

Food web structure regulates the pathways and flow rates of energy, nutrients, and contaminants to top predators. Ecologically and physiologically meaningful biochemical tracers provide a means to characterize and quantify these transfers within food webs. In this study, changes in the ratios of stable N isotopes (e.g., delta(15)N), fatty acids (FA), and persistent contaminants were used to trace food web pathways utilized by herring gulls (Larus argentatus) breeding along the shores of the St Lawrence River, Canada. Egg delta(15)N values varied significantly among years and were used as an indicator of gull trophic position. Temporal trends in egg delta(15)N values were related to egg FA profiles. In years when egg delta(15)N values were greater, egg FA patterns reflected the consumption of more aquatic prey. Egg delta(15)N values were also correlated with annual estimates of prey fish abundance. These results indicated that temporal changes in aquatic prey availability were reflected in the gull diet (as inferred from ecological tracer profiles in gull eggs). Analysis of individual eggs within years confirmed that birds consuming more aquatic prey occupied higher trophic positions. Furthermore, increases in trophic position were associated with increased concentrations of most persistent organic contaminants in eggs. However, levels of highly brominated polybrominated diphenyl ether congeners, e.g, 2,2',3,3',4,4',5,5',6,6'-decabromoDE (BDE-209), showed a negative relationship with trophic position. These contrasting findings reflected differences among contaminant groups/homologs in terms of their predominant routes of transfer, i.e., aquatic versus terrestrial food webs. High trophic level omnivores, e.g., herring gulls, are common in food webs. By characterizing ecological tracer profiles in such species we can better understand spatial, temporal, and individual differences in pathways of contaminant, energy, and nutrient flow. PMID:19219461

Hebert, Craig E; Weseloh, D V Chip; Gauthier, Lewis T; Arts, Michael T; Letcher, Robert J

2009-05-01

334

Protozoan pulses unveil their pivotal position within the soil food web.  

PubMed

Protozoa are one of the most abundant groups of bacterivores within the soil and are responsible for mineralisation of bacterial biomass, having a large impact on C and N cycling. Little is known of their contribution to soil nutrient transfers or the identity of their consumers. Here, for the first time indigenous flagellates and ciliates, enriched to 83 atom% for (13)C and 10 atom% for (15)N, were introduced to soil cores from two different land managements, grassland and woodland with the same soil type, to trace the flow of protozoan C and N through the soil food web. Nematodes, Collembola, earthworms and insect larvae obtained the greatest amounts of C and N of protozoan origin, either through direct consumption or uptake of biomass post-cell death. Our results show that changes in management, affect the functioning of the soil food web and the utilisation of protozoa as a food source. PMID:21990016

Crotty, Felicity V; Adl, Sina M; Blackshaw, Rod P; Murray, Philip J

2012-05-01

335

The role of ammonites in the Mesozoic marine food web revealed by jaw preservation.  

PubMed

Ammonites are prominent in macroevolutionary studies because of their abundance and diversity in the fossil record, but their paleobiology and position in the marine food web are not well understood due to the lack of preserved soft tissue. We present three-dimensional reconstructions of the buccal apparatus in the Mesozoic ammonite Baculites with the use of synchrotron x-ray microtomography. Buccal mass morphology, combined with the coexistence of food remains found in the buccal mass, suggests that these ammonites fed on plankton. This diet may have extended to all aptychophoran ammonites, which share the same buccal mass morphology. Understanding the role of these ammonites in the Mesozoic food web provides insights into their radiation in the Early Jurassic, as well as their extinction at the end of the Cretaceous/early Paleogene. PMID:21212354

Kruta, Isabelle; Landman, Neil; Rouget, Isabelle; Cecca, Fabrizio; Tafforeau, Paul

2011-01-01

336

Land-use type changes the belowground food-web in an arid, urban ecosystem. Karl A. Wyant, Yevgeniy Y. Marusenko, Sharon J. Hall, and John L. Sabo  

E-print Network

-use modifications affect belowground soil food webs in arid, urban areas. 2. Research Question and Hypothesis · Who (water and SOM) in mesic lawns will lead to an increase in soil food web biomass and functional groups -1[5] · Unclear whether urban soil food webs are structured primarily by SM or SOM 4. Results · Fig

Hall, Sharon J.

337

Soil life in reconstructed ecosystems: Initial soil food web responses after rebuilding a forest soil profile for a climate change experiment  

E-print Network

Soil life in reconstructed ecosystems: Initial soil food web responses after rebuilding a forest that was planted with Douglas-fir (Pseudotsugo menziesii Mirb. Franco) seedlings. Generally. soil food web that initial food web population responses were related to increased availability of soil carbon caused

Fried, Jeremy S.

338

River food web response to large-scale riparian zone manipulations.  

PubMed

Conservation programs often focus on select species, leading to management plans based on the autecology of the focal species, but multiple ecosystem components can be affected both by the environmental factors impacting, and the management targeting, focal species. These broader effects can have indirect impacts on target species through the web of interactions within ecosystems. For example, human activity can strongly alter riparian vegetation, potentially impacting both economically-important salmonids and their associated river food web. In an Olympic Peninsula river, Washington state, USA, replicated large-scale riparian vegetation manipulations implemented with the long-term (>40 yr) goal of improving salmon habitat did not affect water temperature, nutrient limitation or habitat characteristics, but reduced canopy cover, causing reduced energy input via leaf litter, increased incident solar radiation (UV and PAR) and increased algal production compared to controls. In response, benthic algae, most insect taxa, and juvenile salmonids increased in manipulated areas. Stable isotope analysis revealed a predominant contribution of algal-derived energy to salmonid diets in manipulated reaches. The experiment demonstrates that riparian management targeting salmonids strongly affects river food webs via changes in the energy base, illustrates how species-based management strategies can have unanticipated indirect effects on the target species via the associated food web, and supports ecosystem-based management approaches for restoring depleted salmonid stocks. PMID:23284786

Wootton, J Timothy

2012-01-01

339

From projected species distribution to food-web structure under climate change.  

PubMed

Climate change is inducing deep modifications in species geographic ranges worldwide. However, the consequences of such changes on community structure are still poorly understood, particularly the impacts on food-web properties. Here, we propose a new framework, coupling species distribution and trophic models, to predict climate change impacts on food-web structure across the Mediterranean Sea. Sea surface temperature was used to determine the fish climate niches and their future distributions. Body size was used to infer trophic interactions between fish species. Our projections reveal that 54 fish species of 256 endemic and native species included in our analysis would disappear by 2080-2099 from the Mediterranean continental shelf. The number of feeding links between fish species would decrease on 73.4% of the continental shelf. However, the connectance of the overall fish web would increase on average, from 0.26 to 0.29, mainly due to a differential loss rate of feeding links and species richness. This result masks a systematic decrease in predator generality, estimated here as the number of prey species, from 30.0 to 25.4. Therefore, our study highlights large-scale impacts of climate change on marine food-web structure with potential deep consequences on ecosystem functioning. However, these impacts will likely be highly heterogeneous in space, challenging our current understanding of climate change impact on local marine ecosystems. PMID:24214576

Albouy, Camille; Velez, Laure; Coll, Marta; Colloca, Francesco; Le Loc'h, François; Mouillot, David; Gravel, Dominique

2014-03-01

340

Methylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National Park, Wyoming.  

PubMed

Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pH approximately 3.0) thermal springs were found to serve as a food source for stratiomyid (Diptera: Stratiomyidae) larvae. Mercury in spring source water was taken up and concentrated by the mat biomass. Monomethylmercury compounds (MeHg(+)), while undetectable or near the detection limit (0.025 ng l(-1)) in the source water of the springs, was present at concentrations of 4-7 ng g(-1) dry weight of mat biomass. Detection of MeHg(+) in tracheal tissue of larvae grazing the mat suggests that MeHg(+) enters this geothermal food web through the phototrophic microbial mat community. The concentration of MeHg(+) was two to five times higher in larval tissue than mat biomass indicating MeHg(+) biomagnification occurred between primary producer and primary consumer trophic levels. The Zygogonium mat community and stratiomyid larvae may also play a role in the transfer of MeHg(+) to species in the food web whose range extends beyond a particular geothermal feature of YNP. PMID:19170726

Boyd, Eric S; King, Susan; Tomberlin, Jeffery K; Nordstrom, D Kirk; Krabbenhoft, David P; Barkay, Tamar; Geesey, Gill G

2009-04-01

341

Application of nitrogen stable isotope analysis in size-based marine food web and macroecological research.  

PubMed

Interacting human and environmental pressures influence the structure and dynamics of marine food webs. To describe and predict the effects of these pressures, theoretical advances need to be supported by a capacity to validate the underlying models and assumptions. Here, we review recent applications of nitrogen stable isotope analysis in marine food web and macroecological research, with a focus on work that has paralleled a resurgence of interest in the development and application of size-based models. Nitrogen stable isotope data have been used to estimate intra- and inter-specific variation in trophic level, predator-prey size ratios, transfer efficiency, food chain length, relationships between predator and prey species diversity and the dynamics of energy use. Many of these estimates have contributed to the development, testing and parameterisation of food web and ecosystem models, some of which have been used to establish baselines for assessing the scale of human impacts. The interpretation of results depends on assumed fractionation but, when supported by sensitivity analyses and experimental validation, nitrogen stable isotope data provide valuable insights into the structuring of marine communities and ecosystems. PMID:18438766

Jennings, Simon; Barnes, Carolyn; Sweeting, Christopher J; Polunin, Nicholas V C

2008-06-01

342

Canyon conditions impact carbon flows in food webs of three sections of the Nazaré canyon  

NASA Astrophysics Data System (ADS)

Submarine canyons transport large amounts of sediment and organic matter (OM) from the continental shelf to the abyssal plain. Three carbon-based food web models were constructed for the upper (300-750 m water depth), middle (2700-3500 m) and lower section (4000-5000 m) of the Nazaré canyon (eastern Atlantic Ocean) using linear inverse modeling to examine how the food web is influenced by the characteristics of the respective canyon section. The models were based on an empirical dataset consisting of biomass and carbon processing data, and general physiological data constraints from the literature. Environmental conditions, most notably organic matter (OM) input and hydrodynamic activity, differed between the canyon sections and strongly affected the benthic food web structure. Despite the large difference in depth, the OM inputs into the food webs of the upper and middle sections were of similar magnitude (7.98±0.84 and 9.30±0.71 mmol C m -2 d -1, respectively). OM input to the lower section was however almost 6-7 times lower (1.26±0.03 mmol C m -2 d -1). Carbon processing in the upper section was dominated by prokaryotes (70% of total respiration), though there was a significant meiofaunal (21%) and smaller macrofaunal (9%) contribution. The high total faunal contribution to carbon processing resembles that found in shallower continental shelves and upper slopes, although the meiofaunal contribution is surprisingly high and suggest that high current speeds and sediment resuspension in the upper canyon favor the role of the meiofauna. The high OM input and conditions in the accreting sediments of the middle canyon section were more beneficial for megafauna (holothurians), than for the other food web compartments. The high megafaunal biomass (516 mmol C m -2), their large contribution to respiration (56% of total respiration) and secondary production (0.08 mmol C m -2 d -1) shows that these accreting sediments in canyons are megafaunal hotspots in the deep-sea. Conversely, carbon cycling in the lower canyon section was strongly dominated by prokaryotes (86% of respiration) and the food web structure therefore resembled that of lower slope and abyssal plain sediments. This study shows that elevated OM input in canyons may favor the faunal contribution to carbon processing and create hotspots of faunal biomass and carbon processing along the continental shelf.

van Oevelen, Dick; Soetaert, Karline; Garcia, R.; de Stigter, Henko C.; Cunha, Marina R.; Pusceddu, Antonio; Danovaro, Roberto

2011-12-01

343

Mercury bioaccumulation and trophic transfer in the terrestrial food web of a montane forest.  

PubMed

We investigated mercury (Hg) concentrations in a terrestrial food web in high elevation forests in Vermont. Hg concentrations increased from autotrophic organisms to herbivores < detritivores < omnivores < carnivores. Within the carnivores studied, raptors had higher blood Hg concentrations than their songbird prey. The Hg concentration in the blood of the focal study species, Bicknell's thrush (Catharus bicknelli), varied over the course of the summer in response to a diet shift related to changing availability of arthropod prey. The Bicknell's thrush food web is more detrital-based (with higher Hg concentrations) in early summer and more foliage-based (with lower Hg concentrations) during late summer. There were significant year effects in different ecosystem compartments indicating a possible connection between atmospheric Hg deposition, detrital-layer Hg concentrations, arthropod Hg concentrations, and passerine blood Hg concentrations. PMID:19960247

Rimmer, Christopher C; Miller, Eric K; McFarland, Kent P; Taylor, Robert J; Faccio, Steven D

2010-04-01

344

Fear begets function in the 'brown' world of detrital food webs.  

PubMed

Theory suggests that predators in detritus-based food webs should negatively influence plants, through direct effects on plant-facilitating detritivores. In a three-level food web of predaceous beetles, earthworms and plants, Zhao et al. (2013) report evidence to the contrary. They found that predators drove positive indirect effects on both plant-facilitating soil properties and above-ground plant biomass and that these positive effects were driven by predator-mediated vertical shifts in detritivore habitat use. Their study reinforces the importance of trait-mediated indirect interactions across both 'green' and 'brown' trophic cascades and emphasizes that understanding the spatial dimension of trophic cascade mechanisms remains a critical research priority. PMID:24758400

Nichols, Elizabeth

2013-07-01

345

Climatic seasonality may affect ecological network structure: Food webs and mutualistic networks  

E-print Network

Ecological networks exhibit non-random structural patterns, such as modularity and nestedness, which indicate ecosystem stability, species diversity, and connectance. Such structure-stability relationships are well known. However, another important perspective is less well understood: the relationship between the environment and structure. Inspired by theoretical studies that suggest that network structure can change due to environmental variability, we collected data on a number of empirical food webs and mutualistic networks and evaluated the effect of climatic seasonality on ecological network structure. As expected, we found that climatic seasonality affects ecological network structure. In particular, an increase in modularity due to climatic seasonality was observed in food webs; however, it is debatable whether this occurs in mutualistic networks. Interestingly, the type of climatic seasonality that affects network structure differs with ecosystem type. Rainfall and temperature seasonality influence fr...

Takemoto, Kazuhiro; Feng, Wenfeng

2014-01-01

346

Mercury and nitrogen isotope in a marine species from a tropical coastal food web.  

PubMed

The present study raised the hypothesis that the trophic status in a tropical coastal food web from southeastern Brazil can be measured by the relation between total mercury (THg) and nitrogen isotope (?(15)N) in their components. The analysed species were grouped into six trophic positions: primary producer (phytoplankton), primary consumer (zooplankton), consumer 1 (omnivore shrimp), consumer 2 (pelagic carnivores represented by squid and fish species), consumer 3 (demersal carnivores represented by fish species) and consumer 4 (pelagic-demersal top carnivore represented by the fish Trichiurus lepturus). The values of THg, ?(15)N, and trophic level (TLv) increased significantly from primary producer toward top carnivore. Our data regarding trophic magnification (6.84) and biomagnification powers (0.25 for ?(15)N and 0.83 for TLv) indicated that Hg biomagnification throughout trophic positions is high in this tropical food web, which could be primarily related to the quality of the local water. PMID:21858737

Di Beneditto, Ana Paula Madeira; Bittar, Vanessa Trindade; Camargo, Plínio Barbosa; Rezende, Carlos Eduardo; Kehrig, Helena Amaral

2012-02-01

347

Food webs of two intermittently open estuaries receiving 15N-enriched sewage effluent  

NASA Astrophysics Data System (ADS)

Carbon and nitrogen stable isotope signatures were used to assess the response of food webs to sewage effluent discharged into two small intermittently open estuaries in northern New South Wales, Australia. One of these systems, Tallows Creek, has a history of direct sewage inputs, whilst the other, Belongil Creek, receives wastewater via an extensive wetland treatment system. The food webs of both systems were driven by algal sources of carbon, reflecting high autotrophic productivity in response to the nutrients entering the system from sewage effluent. All aquatic biota collected from Tallows Creek had significantly enriched ?15N signatures relative to their conspecifics from Belongil Creek, indicating that sewage nitrogen had been assimilated and transferred throughout the Tallows Creek food web. These ?15N values were higher than those reported from studies in permanently open estuaries receiving sewage effluent. We suggest that these enriched signatures and the transfer of nitrogen throughout the entire food web reflect differences in hydrology and associated nitrogen cycling processes between permanently open and intermittently open estuaries. Although all organisms in Tallows Creek were generally 15N-enriched, isotopically light (less 15N-enriched) individuals of estuary perchlet ( Ambassis marianus) and sea mullet ( Mugil cephalus) were also collected. These individuals were most likely recent immigrants into Tallows Creek, as this system had only recently been opened to the ocean. This isotopic discrimination between resident (enriched) and immigrant (significantly less enriched) individuals can provide information on fish movement patterns and the role of heavily polluted intermittently open estuaries in supporting commercially and recreationally valuable estuarine species.

Hadwen, Wade L.; Arthington, Angela H.

2007-01-01

348

Resource-Consumer Relationships and Baseline Stable Isotopic Signatures of Food Webs in Isolated Wetlands  

Microsoft Academic Search

We examined isolated wetland food webs using stable C and N isotopes to understand resource-consumer relationships and controls\\u000a on baseline isotopic signatures. Marshes were usually more 13C-enriched than cypress savannas and cypress gum swamps. Analysis of coarse particulate organic matter (CPOM) fractions indicated\\u000a that C3 plants contributed the majority of organic matter to isolated wetlands. Individual wetlands of the same

Stephen P. Opsahl; Stephen W. Golladay; Lora L. Smith; Stephanie E. Allums

2010-01-01

349

Mercury and Nitrogen Isotope in a Marine Species from a Tropical Coastal Food Web  

Microsoft Academic Search

The present study raised the hypothesis that the trophic status in a tropical coastal food web from southeastern Brazil can\\u000a be measured by the relation between total mercury (THg) and nitrogen isotope (?15N) in their components. The analysed species were grouped into six trophic positions: primary producer (phytoplankton), primary\\u000a consumer (zooplankton), consumer 1 (omnivore shrimp), consumer 2 (pelagic carnivores represented

Ana Paula Madeira Di Beneditto; Vanessa Trindade Bittar; Plínio Barbosa Camargo; Carlos Eduardo Rezende; Helena Amaral Kehrig

350

Distribution of PCB congeners in seven lake systems: Interactions between sediment and food-web transport  

Microsoft Academic Search

A study was conducted to examine the role of two processes, partitioning of PCBs between sediment and biota and food-web transport, in determining the concentration of PCB congeners in the biota of seven lakes. Biota PCB concentration (lipid)-to-sediment PCB concentration (organic carbon), or BSF, ratios were calculated as markers of the partitioning of PCBs between biota and sediment, and biota

Colin R. Macdonald; Chris D. Metcalfe; Gordon C. Balch; Tracy L. Metcalfe

1993-01-01

351

Soil resource supply influences faunal size–specific distributions in natural food webs  

Microsoft Academic Search

The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities.\\u000a The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning,\\u000a and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of\\u000a soil organisms in

Christian Mulder; Henri A. Den Hollander; J. Arie Vonk; Axel G. Rossberg; Gerard A. J. M. Jagers op Akkerhuis; Gregor W. Yeates

2009-01-01

352

Mercury biomagnification in the food web of Lake Tanganyika (Tanzania, East Africa).  

PubMed

Lake Tanganyika is a globally important lake with high endemic biodiversity. Millions of people in the lake basin depend on several fish species for consumption. Due to the importance of fish consumption as an exposure route of mercury to humans, we sampled Lake Tanganyika in 2000 to assess total mercury concentrations and biomagnification of total mercury through the food web. Stable nitrogen and carbon isotope analyses of food web structure indicate a complex food web with overlapping omnivory with some specialist fish species. Stable nitrogen isotope analyses further confirm that mercury is biomagnifying through the Tanganyika food web at rates similar to those seen in Lakes Malawi and Victoria, the other two African Great Lakes. Most collected fish species and all invertebrate species had mercury concentrations below 0.2 microg Hg/g wet weight. However, several fish species, Ctenochromis horei (average 0.15 microg/g ww), Neolamprologus boulengeri (0.2 microg/g ww) , Bathybates spp.spp. (0.21 microg/g ww), Mastacembelus cunningtoni (0.22 microg/g ww) and Clarias theodorae (0.22 microg/g ww) approached or slightly exceeded the World Health Organization (WHO)'s recommended guideline of 0.2 microg Hg/g for vulnerable populations with high rates of fish consumption. Two individuals of the piscivorous fish species Lates microlepis (0.54, 0.78 microg/g ww) and a Polypterus congicus (1.3 microg/g ww) exceeded the international marketing limit value of 0.5 microg/g ww. Because C. theodorae and L. microlepis are also important market fish species, there is a need to monitor mercury concentrations in internationally marketed fish from Lake Tanganikya to ensure that those fish do not present a risk to human consumers. PMID:18559282

Campbell, L; Verburg, Piet; Dixon, D G; Hecky, R E

2008-09-01

353

Selection of an Aquatic Indicator Species to Monitor Organic Contaminants in Trophically Simple Lotic Food Webs  

Microsoft Academic Search

.   A four-step procedure was used to identify an aquatic macroinvertebrate with which to monitor organic contaminant burdens\\u000a in trophically simple lake food webs of Alberta, Canada. We identified leeches (Oligochaeta: Hirudinea) as the potential indicator\\u000a assemblage (Step 1), and then documented their abundance and distribution in 16 lakes to identify a species-level bioindicator\\u000a (Step 2). The latter two steps

G. J. Scrimgeour; D. Wicklum; S. D. Pruss

1998-01-01

354

Effects of organic matter removal on the soil food web: Forestry practices meet ecological theory  

Microsoft Academic Search

We examine the long-term effects of removing forest harvesting residues (above-ground whole-tree harvesting; WTH) in the soil food web, using data from two different experiments on slash removal and addition in Sweden. Removal of harvesting residues had negative effects on the abundances of animals at higher trophic positions and on more mobile animals. Predators such as gamasid mites, spiders and

Jan Bengtsson; Heléne Lundkvist; Peter Saetre; Björn Sohlenius; Berit Solbreck

1998-01-01

355

The relationships between mercury and selenium in plankton and fish from a tropical food web  

Microsoft Academic Search

Background, aim, and scope  Selenium (Se) has been shown to reduce mercury (Hg) bioavailability and trophic transfer in aquatic ecosystems. The study\\u000a of methylmercury (MeHg) and Se bioaccumulation by plankton is therefore of great significance in order to obtain a better\\u000a understanding of the estuarine processes concerning Hg and Se accumulation and biomagnification throughout the food web. In\\u000a the western South

Helena do A. Kehrig; Tércia G. Seixas; Elisabete A. Palermo; Aida P. Baêta; Christina W. Castelo-Branco; Olaf Malm; Isabel Moreira

2009-01-01

356

Food Web Changes over Fourteen Years Following Introduction of Rainbow Smelt into a Colorado Reservoir  

Microsoft Academic Search

Rainbow smelt Osmerus mordaxwere introduced into Horsetooth Reservoir, Colorado, in 1983 to increase prey availability for walleyes Stizostedion vitreum.The introduction was highly successful. Rainbow smelt abundance reached at least 0.4 fish\\/m 3 within 6 years, and walleye growth improved by 50%. Zooplankton sampling provided the first clues that the Horsetooth Reservoir food web was undergoing dramatic changes in response to

Brett M. Johnson; John P. Goettl

1999-01-01

357

Influence of lake characteristics on the biomagnification of persistent organic pollutants in lake trout food webs.  

PubMed

The biomagnification of polychlorinated biphenyls (PCBs) and major organochlorine pesticides (OCPs) was studied using lake trout (Salvelinus namaycush) and other food web organisms collected from 17 lakes in Canada and the northeastern United States between 1998 and 2001. Whole lake trout (n = 357) concentrations of the sum (Sigma) of 57 PCB congeners ranged between 1.67 and 2,890 ng/g wet weight (median 61.5 ng/g wet wt). Slimy sculpin had the highest mean concentrations of SigmaPCB of all forage fish (32-73 ng/g wet wt). Positive relationships between log (lipid wt) concentrations of PCB congener 153, PCB congener 52, p,p'-dichlorodiphenyldichloroethylene, hexachlorobenzene, cis-chlordane, trans-nonachlor, or dieldrin and trophic level (determined using stable nitrogen isotope ratios) were found for most of the 17 food webs, indicating biomagnification of these PCBs and OCPs. The p,p'-dichlorodiphenyldichloroethylene had the highest trophic magnification factors (TMFs) of the 14 individual compounds studied, averaging 4.0 +/- 1.8 across the 17 lakes, followed by trans-nonachlor (3.6 +/- 1.5) and PCB congener 153 (3.4 +/- 1.2). Average TMFs for 14 individual PCBs or OCPs were significantly correlated with log octanol-water partition coefficient, implying that the rate of accumulation along the food web is dependent on hydrophobicity and recalcitrance. Significant correlations (p < 0.05) were found between TMFs of SigmaPCBs, hexachlorobenzene, alpha-hexachlorocyclohexane, and lindane and lake area, latitude, and longitude, but not for 11 other PCBs or OCPs. Overall, the results of the present study show that biomagnification of PCBs and most OCPs, as measured by TMFs, is only weakly influenced by such factors as latitude and longitude. Exceptions are hexachlorocyclohexane isomers and hexachlorobenzene, which had generally greater TMFs in northern lakes, possibly due to lower rates of elimination and biotransformation in the food web. PMID:18444699

Houde, Magali; Muir, Derek C G; Kidd, Karen A; Guildford, Stephanie; Drouillard, Ken; Evans, Marlene S; Wang, Xiaowa; Whittle, D Michael; Haffner, Doug; Kling, Hedy

2008-10-01

358

Effects of shrimp-farm effluents on the food web structure in subtropical coastal lagoons  

Microsoft Academic Search

Although numerous studies have reported the negative effects of shrimp aquaculture on water quality, little is known about the ecological effects of these practices in coastal lagoons and near-shore marine habitats. The impact of shrimp-farm effluents on the food webs of an impacted subtropical coastal lagoon in the Gulf of California was evaluated through measurements of isotopic (?13C, ?15N) signatures

L. Serrano-Grijalva; S. Sánchez-Carrillo; D. G. Angeler; R. Sánchez-Andrés; M. Álvarez-Cobelas

2011-01-01

359

Facing the necessity of describing estuarine ecosystems: a review of food web ecology study techniques  

Microsoft Academic Search

Estuarine areas are sites of human pressures and degradation. In order to maintain and\\/or restore the quality of estuarine\\u000a ecosystems, it is necessary to describe their structure and functioning. For that reason, many recent scientific works focus\\u000a on food webs, which are depicted as being good indicators of the functioning of aquatic ecosystems. Hence it is necessary\\u000a to question how

Stéphanie Pasquaud; Jérémy Lobry; Pierre Elie

2007-01-01

360

Seasonal variation in food web composition and structure in a temperate tidal estuary  

Microsoft Academic Search

Seasonal variation in aquatic food web structure at Mad Island Marsh, Matagorda Bay, Texas, was examined using dietary information\\u000a obtained from the analysis of gut contents from large samples of fish and crustacean specimens. Unique aspects of this study\\u000a include the use of large samples of consumer gut contents (n=6,452), long-term sampling (bimonthly surveys over 18 mo), and\\u000a standard methods

S. Akin; K. O. Winemiller

2006-01-01

361

Emergence and maintenance of biodiversity in an evolutionary food-web model  

Microsoft Academic Search

Ecological communities emerge as a consequence of gradual evolution, speciation, and immigration. In this study, we explore\\u000a how these processes and the structure of the evolved food webs are affected by species-level properties. Using a model of\\u000a biodiversity formation that is based on body size as the evolving trait and incorporates gradual evolution and adaptive radiation,\\u000a we investigate how conditions

Åke Brännström; Nicolas Loeuille; Michel Loreau; Ulf Dieckmann

362

Persistent organic pollutants in river food webs: influence of trophic position and degree of heterotrophy  

Microsoft Academic Search

We investigated how the degree of autotrophy\\/heterotrophy and organism trophic position influenced the bioaccumulation of polychlorinated biphenyls (PCBs) in 10 benthic river food webs consisting of terrestrial detritus, periphyton, invertebrates, and age-0 brown trout (Salmo trutta) in southern Sweden. Concentrations of PCBs increased with trophic position, estimated from ?15N and ?13C, on a dry weight basis (ng·g-1 dry weight) but

Olof Berglund; Per Nyström; Per Larsson

2005-01-01

363

Organochlorine compounds in Lake Superior: chiral polychlorinated biphenyls and biotransformation in the aquatic food web.  

PubMed

The enantiomeric composition of seven chiral PCB congeners was measured in the Lake Superior aquatic food web sampled in 1998, to determine the extent of enantioselective biotransformation in aquatic biota. All chiral PCB congeners studied (CBs 91, 95, 136, 149, 174, 176, and 183) biomagnified in the Lake Superior aquatic food web, based on biomagnification and food web magnification factors greater than unity. PCB atropisomers were racemic in phytoplankton and zooplankton, suggesting no biotransformation potential toward PCBs for these low trophic level organisms. However, Diporeia and mysids had significantly nonracemic residues for most chiral congeners studied. This observation suggests that these macrozooplankton can stereoselectively metabolize chiral congeners. Alternatively, macrozooplankton obtained nonracemic residues from feeding on organic-rich suspended particles and sediments, which would imply that stereoselective microbial PCB biotransformation may be occurring in Lake Superior sediments at PCB concentrations far lower than that previously associated with such activity. Widely nonracemic PCB residues in forage fish (lake herring, rainbow smelt, and slimy sculpin) and lake trout suggest a combination of both in vivo biotransformation and uptake of nonracemic residues from prey for these species. Minimum biotransformation rates, calculated from enantiomer mass balances between predators and prey, suggest metabolic half-lives on the order of 8 yr for CB 136 in lake trout and 2.6 yr for CB 95 in sculpins. This result suggests that significant biotransformation may occur for metabolizable PCB congeners over the lifespan of these biota. This study highlights the potential of chiral analysis to study biotransformation processes in food webs. PMID:14740721

Wong, Charles S; Mabury, Scott A; Whittle, D Michael; Backus, Sean M; Teixeira, Camilla; DeVault, David S; Bronte, Charles R; Muir, Derek C G

2004-01-01

364

Food web analysis of southern California coastal wetlands using multiple stable isotopes  

Microsoft Academic Search

Carbon, nitrogen, and sulfur stable isotopes were used to characterize the food webs (i.e., sources of carbon and trophic\\u000a status of consumers) in Tijuana Estuary and San Dieguito Lagoon. Producer groups were most clearly differentiated by carbon,\\u000a then by sulfur, and least clearly by nitrogen isotope measurements. Consumer 15N isotopic enrichment suggested that there are four trophic levels in the

Thomas J. Kwak; Joy B. Zedler

1997-01-01

365

Trophic magnification and isomer fractionation of perfluoroalkyl substances in the food web of Taihu Lake, China.  

PubMed

Biomagnification of perfluoroalkyl substances (PFASs) are well studied in marine food webs, but related information in fresh water ecosystem and knowledge on fractionation of their isomers along the food web are limited. The distribution, bioaccumulation, magnification, and isomer fractionation of PFASs were investigated in a food web of Taihu Lake, China. Perfluorooctanesulfonate (PFOS) and perfluorocarboxylates (PFCAs) with longer carbon chain lengths, such as perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnA), were predominant in organisms, while perfluorohexanoate (PFHxA) and perfluorooctanoate (?PFOA) contributed more in the water phase. The consistent profile signature of PFOA isomers in water phase with 3M electrochemical fluorination (ECF) products suggests that ECF production of PFOA still exists in China. Linear proportions of PFOA, PFOS and perfluorooctane sulfonamide (PFOSA) in the biota were in the range of 91.9-100%, 78.6-95.5%, and 72.2-95.5%, respectively, indicating preferential bioaccumulation of linear isomers in biota. Trophic magnification factors (TMFs) were estimated for PFDA (2.43), perfluorododecanoate (PFDoA) (2.68) and PFOS (3.46) when all biota were included, suggesting that PFOS and long-chained PFCAs are biomagnified in the fresh water food web. The TMF of PFOS isomers descended in the order: n-PFOS (3.86) > 3+5m-PFOS (3.35) > 4m-PFOS (3.32) > 1m-PFOS (2.92) > m2-PFOS (2.67) > iso-PFOS (2.59), which is roughly identical to their elution order on a FluoroSep-RP Octyl column, suggesting that hydrophobicity may be an important contributor for isomer discrimination in biota. PMID:24460088

Fang, Shuhong; Chen, Xinwei; Zhao, Shuyan; Zhang, Yifeng; Jiang, Weiwei; Yang, Liping; Zhu, Lingyan

2014-02-18

366

Chain or Web?  

NSDL National Science Digital Library

This reference provides a brief description of marine food webs. It presents food web terminology, explains the relationship between food chains and food webs, and introduces the concept of microbial loops.

367

A food web bioaccumulation model for organic chemicals in aquatic ecosystems.  

PubMed

The present study examines a new bioaccumulation model for hydrophobic organic chemicals in aquatic food webs. The purpose of the model is to provide site-specific estimates of chemical concentrations and associated bioconcentration factors, bioaccumulation factors, and biota-sediment accumulation factors in organisms of aquatic food webs using a limited number of chemical, organism, and site-specific data inputs. The model is a modification of a previous model and incorporates new insights regarding the mechanism of bioaccumulation derived from laboratory experiments and field studies as well as improvements in model parameterization. The new elements of the model include: A model for the partitioning of chemicals into organisms; kinetic models for predicting chemical concentrations in algae, phytoplankton, and zooplankton; new allometric relationships for predicting gill ventilation rates in a wide range of aquatic species; and a mechanistic model for predicting gastrointestinal magnification of organic chemicals in a range of species. Model performance is evaluated using empirical data from three different freshwater ecosystems involving 1,019 observations for 35 species and 64 chemicals. The effects of each modification on the model's performance are illustrated. The new model is able to provide better estimates of bioaccumulation factors in comparison to the previous food web bioaccumulation model while the model input requirements remain largely unchanged. PMID:15511097

Arnot, Jon A; Gobas, Frank A P C

2004-10-01

368

Nitrogen addition and warming independently influence the belowground micro-food web in a temperate steppe.  

PubMed

Climate warming and atmospheric nitrogen (N) deposition are known to influence ecosystem structure and functioning. However, our understanding of the interactive effect of these global changes on ecosystem functioning is relatively limited, especially when it concerns the responses of soils and soil organisms. We conducted a field experiment to study the interactive effects of warming and N addition on soil food web. The experiment was established in 2006 in a temperate steppe in northern China. After three to four years (2009-2010), we found that N addition positively affected microbial biomass and negatively influenced trophic group and ecological indices of soil nematodes. However, the warming effects were less obvious, only fungal PLFA showed a decreasing trend under warming. Interestingly, the influence of N addition did not depend on warming. Structural equation modeling analysis suggested that the direct pathway between N addition and soil food web components were more important than the indirect connections through alterations in soil abiotic characters or plant growth. Nitrogen enrichment also affected the soil nematode community indirectly through changes in soil pH and PLFA. We conclude that experimental warming influenced soil food web components of the temperate steppe less than N addition, and there was little influence of warming on N addition effects under these experimental conditions. PMID:23544140

Li, Qi; Bai, Huahua; Liang, Wenju; Xia, Jianyang; Wan, Shiqiang; van der Putten, Wim H

2013-01-01

369

Soil resource supply influences faunal size-specific distributions in natural food webs  

NASA Astrophysics Data System (ADS)

The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities. The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning, and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of soil organisms in 20 Dutch meadows and heathlands were investigated. Using principles of allometry, maximal use can be made of ecological theory to build and explain food webs. The aggregate contribution of small invertebrates such as nematodes to the entire community is high under low soil phosphorus content and causes shifts in the mass-abundance relationships and in the trophic structures. We show for the first time that the average of the trophic link lengths is a reliable predictor for assessing soil fertility responses. Ordered trophic link pairs suggest a self-organizing structure of food webs according to resource availability and can predict environmental shifts in ecologically meaningful ways.

Mulder, Christian; den Hollander, Henri A.; Vonk, J. Arie; Rossberg, Axel G.; Jagers Op Akkerhuis, Gerard A. J. M.; Yeates, Gregor W.

2009-07-01

370

Stable isotopes and organochlorines in the food webs of Lakes Baikal and Superior  

SciTech Connect

Quantifying organochlorine biomagnification in aquatic ecosystems is traditionally accomplished by assigning discreet trophic levels, which does not adequately describe feeding relationships except in well defined systems. {delta}{sup 15}N and {delta}{sup 13}C, particularly {delta}{sup 15}N values, measured in aquatic food webs provide additional information on trophic position such that it may be treated as a continuous variable. To evaluate this technique, samples were collected from the pelagic zone of Lake Baikal in August and September, 1993 for organochlorine (PCBs, DDTs, chlordanes and HCHS) and stable isotope ({delta}{sup 13}C and {delta}{sup 15}N) analyzed. These included high volume water samples, seston, net plankton, two species of pelagic sculpin Comephorus dybowskii, C. baikalensis, the omul, (Coregonus autumnalis migratorious), and 9 seal (Phoca siberica) samples of known sex and age. Food web samples from Lake Superior will be collected in June, 1994 to include benthic infauna, sculpins, Mysis and surface phytoplankton and zooplankton. Results from this study will provide a comparison of organochlorine trophodynamics between a system with a predominant pelagic food web (Lake Baikal) to one with substantial benthic/pelagic coupling (Lake Superior).

Kucklick, J.R.; Baker, J.E. [Univ. of Maryland System, Solomons, MD (United States). Chesapeake Biological Lab.; Ostrom, N.E.; Ostrom, P.H. [Michigan State Univ., East Lansing, MI (United States). Dept. of Geological Sciences; Lee, D.S. [Univ. of Connecticut, Groton, CT (United States)

1994-12-31

371

An isotopic investigation of mercury accumulation in terrestrial food webs adjacent to an Arctic seabird colony.  

PubMed

At Cape Vera (Devon Island, Nunavut, Canada), a seabird colony of northern fulmars (Fulmarus glacialis) congregates and releases nutrients through the deposition of guano to the coastal terrestrial environment, thus creating nutrient-fertilized habitats important to insects, birds, and mammals. Here we determined whether mercury was similarly enriched in various terrestrial food web components in this High Arctic coastal ecosystem due to seabird inputs. Stable isotopes (delta(15)N, delta(13)C) were used to identify trophic linkages and possible routes of contaminant transfer in the food web. Values of delta(15)N were significantly higher in lichens and certain plants collected closer to the bird colony, demonstrating a gradient of seabird influence, and were higher at Cape Vera than our reference site at Cape Herschel, on eastern Ellesmere Island, an area relatively unaffected by seabirds. In contrast, delta(13)C showed little variation among terrestrial species, suggesting minimal influence by seabirds. Concentrations of total mercury (THg) in primary producers and phyto/zooplankton were not significantly correlated with distance from the seabird colony or delta(15)N values, and were similar to other taxa from the High Arctic. Our results provide novel data on THg in several Arctic taxa where concentrations have not been reported previously. Moreover, the analyses indicate that delta(15)N is significantly enriched in the adjacent environment by guano fertilization, but our study was unable to show an enrichment of THg and delta(13)C in the terrestrial food web near the seabird colony. PMID:20153017

Choy, Emily S; Gauthier, Martine; Mallory, Mark L; Smol, John P; Douglas, Marianne S V; Lean, David; Blais, Jules M

2010-03-15

372

Evolution mediates the effects of apex predation on aquatic food webs.  

PubMed

Ecological and evolutionary mechanisms are increasingly thought to shape local community dynamics. Here, I evaluate if the local adaptation of a meso-predator to an apex predator alters local food webs. The marbled salamander (Ambystoma opacum) is an apex predator that consumes both the spotted salamander (Ambystoma maculatum) and shared zooplankton prey. Common garden experiments reveal that spotted salamander populations which co-occur with marbled salamanders forage more intensely than those that face other predator species. These foraging differences, in turn, alter the diversity, abundance and composition of zooplankton communities in common garden experiments and natural ponds. Locally adapted spotted salamanders exacerbate prey biomass declines associated with apex predation, but dampen the top-down effects of apex predation on prey diversity. Countergradient selection on foraging explains why locally adapted spotted salamanders exacerbate prey biomass declines. The two salamander species prefer different prey species, which explains why adapted spotted salamanders buffer changes in prey composition owing to apex predation. Results suggest that local adaptation can strongly mediate effects from apex predation on local food webs. Community ecologists might often need to consider the evolutionary history of populations to understand local diversity patterns, food web dynamics, resource gradients and their responses to disturbance. PMID:23720548

Urban, Mark C

2013-07-22

373

Using food web dominator trees to catch secondary extinctions in action  

PubMed Central

In ecosystems, a single extinction event can give rise to multiple ‘secondary’ extinctions. Conservation effort would benefit from tools that help forecast the consequences of species removal. One such tool is the dominator tree, a graph-theoretic algorithm that when applied to food webs unfolds their complex architecture, yielding a simpler topology made of linear pathways that are essential for energy delivery. Each species along these chains is responsible for passing energy to the taxa that follow it and, as such, it is indispensable for their survival. To assess the predictive potential of the dominator tree, we compare its predictions with the effects that followed the collapse of the capelin (Mallotus villosus) in the Barents Sea ecosystem. To this end, we first compiled a food web for this ecosystem, then we built the corresponding dominator tree and, finally, we observed whether model predictions matched the empirical observations. This analysis shows the potential and the drawbacks of the dominator trees as a tool for understanding the causes and consequences of extinctions in food webs. PMID:19451123

Bodini, Antonio; Bellingeri, Michele; Allesina, Stefano; Bondavalli, Cristina

2009-01-01

374

Trophic magnification of poly- and perfluorinated compounds in a subtropical food web.  

PubMed

Perfluorinated compounds (PFCs) are known to biomagnify in temperate and Arctic food webs, but little is known about their behavior in subtropical systems. The environmental distribution and biomagnification of PFCs, extractable organic fluorine (EOF), and total fluorine were investigated in a subtropical food web. Surface water, sediment, phytoplankton, zooplankton, gastropods, worms, shrimps, fishes, and waterbirds collected in the Mai Po Marshes Nature Reserve in Hong Kong were analyzed. Trophic magnification was observed for perfluorooctanesulfonate (PFOS), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA), and perfluorododecanoate (PFDoDA) in this food web. Risk assessment results for PFOS, PFDA, and perfluorooctanoate (PFOA) suggest that current PFC concentrations in waterbird livers are unlikely to pose adverse biological effects to waterbirds. All hazard ratio (HR) values reported for PFOS and PFOA are less than one, which suggests that the detected levels will not cause any immediate health effects to the Hong Kong population through the consumption of shrimps and fishes. However, only 10-12% of the EOF in the shrimp samples was comprised of known PFCs, indicating the need for further investigation to identify unknown fluorinated compounds in wildlife. PMID:21644538

Loi, Eva I H; Yeung, Leo W Y; Taniyasu, Sachi; Lam, Paul K S; Kannan, Kurunthachalam; Yamashita, Nobuyoshi

2011-07-01

375

Lipids of Prokaryotic Origin at the Base of Marine Food Webs  

PubMed Central

In particular niches of the marine environment, such as abyssal trenches, icy waters and hot vents, the base of the food web is composed of bacteria and archaea that have developed strategies to survive and thrive under the most extreme conditions. Some of these organisms are considered “extremophiles” and modulate the fatty acid composition of their phospholipids to maintain the adequate fluidity of the cellular membrane under cold/hot temperatures, elevated pressure, high/low salinity and pH. Bacterial cells are even able to produce polyunsaturated fatty acids, contrarily to what was considered until the 1990s, helping the regulation of the membrane fluidity triggered by temperature and pressure and providing protection from oxidative stress. In marine ecosystems, bacteria may either act as a sink of carbon, contribute to nutrient recycling to photo-autotrophs or bacterial organic matter may be transferred to other trophic links in aquatic food webs. The present work aims to provide a comprehensive review on lipid production in bacteria and archaea and to discuss how their lipids, of both heterotrophic and chemoautotrophic origin, contribute to marine food webs. PMID:23342392

de Carvalho, Carla C. C. R.; Caramujo, Maria Jose

2012-01-01

376

Growth, feeding and ecological roles of the mixotrophic and heterotrophic dinoflagellates in marine planktonic food webs  

NASA Astrophysics Data System (ADS)

Planktonic mixotrophic and heterotrophic dinoflagellates are ubiquitous protists and often abundant in marine environments. Recently many phototrophic dinoflagellate species have been revealed to be mixotrophic organisms and also it is suggested that most dinoflagellates may be mixotrophic or heterotrophic protists. The mixotrophic and heterotrophic dinoflagellates are able to feed on diverse prey items including bacteria, picoeukaryotes, nanoflagellates, diatoms, other dinoflagellates, heterotrophic protists, and metazoans due to their diverse feeding mechanisms. In turn they are ingested by many kinds of predators. Thus, the roles of the dinoflagellates in marine planktonic food webs are very diverse. The present paper reviewed the kind of prey which mixotrophic and heterotrophic dinoflagellates are able to feed on, feeding mechanisms, growth and ingestion rates of dinoflagellates, grazing impact by dinoflagellate predators on natural prey populations, predators on dinoflagellates, and red tides dominated by dinoflagellates. Based on this information, we suggested a new marine planktonic food web focusing on mixotrophic and heterotrophic dinoflagellates and provided an insight on the roles of dinoflagellates in the food web.

Jeong, Hae Jin; Yoo, Yeong Du; Kim, Jae Seong; Seong, Kyeong Ah; Kang, Nam Seon; Kim, Tae Hoon

2010-06-01

377

Food quantity and quality regulation of trophic transfer between primary producers and a keystone grazer (Daphnia) in pelagic freshwater food webs  

Microsoft Academic Search

The transfer of energy and nutrients from plants to animals is a key process in all ecosystems. In lakes, inefficient transfer of primary producer derived energy can result in low animal growth rates, accumulation of nuisance phytoplankton blooms and dissipation of energy from the ecosystem. Most research on carbon transfer efficiency in pelagic food webs has focused on either food

Jonas Persson; Michael T. Brett; Tobias Vrede; Joseph L. Ravet

2007-01-01

378

Exploring the effects of multiple management objectives and exotic species on great lakes food webs and contaminant dynamics  

Microsoft Academic Search

A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in\\u000a the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter\\u000a (Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will\\u000a decrease by nearly

Thomas D. Fontaine; Donald J. Stewart

1992-01-01

379

Linking oceanic food webs to coastal production and growth rates of Pacific salmon ( Oncorhynchus spp.), using models on three scales  

Microsoft Academic Search

Three independent modeling methods—a nutrient-phytoplankton–zooplankton (NPZ) model (NEMURO), a food web model (Ecopath\\/Ecosim), and a bioenergetics model for pink salmon (Oncorhynchus gorbuscha)—were linked to examine the relationship between seasonal zooplankton dynamics and annual food web productive potential for Pacific salmon feeding and growing in the Alaskan subarctic gyre ecosystem. The linked approach shows the importance of seasonal and ontogenetic prey

Kerim Y. Aydin; Gordon A. McFarlane; Jacquelynne R. King; Bernard A. Megrey; Katherine W. Myers

2005-01-01

380

Linking oceanic food webs to coastal production and growth rates of Pacific salmon (Oncorhynchus spp.), using models on three scales  

Microsoft Academic Search

Three independent modeling methods---a nutrient-phytoplankton zooplankton (NPZ) model (NEMURO), a food web model (Ecopath\\/Ecosim), and a bioenergetics model for pink salmon (Oncorhynchus gorbuscha)---were linked to examine the relationship between seasonal zooplankton dynamics and annual food web productive potential for Pacific salmon feeding and growing in the Alaskan subarctic gyre ecosystem. The linked approach shows the importance of seasonal and ontogenetic

Kerim Y. Aydin; Gordon A. McFarlane; Jacquelynne R. King; Bernard A. Megrey; Katherine W. Myers

2005-01-01

381

Do stable isotopes reflect the food web development in regenerating ecosystems?  

PubMed

We evaluated the use of delta15N- and delta13C-values to monitor the development of food web complexity and biodiversity in a regenerating ecosystem. Therefore a model food chain was established feeding cultivated woodlice (Porcellio dilatatus) on a cellulolytic fungus (Chaetomium globosum) grown on cellulose paper. Two diets of different quality (C:N ratios of 54 vs. 200) with different delta15N- (1.3% vs. 3.1%) but identical delta13C-values caused low and high dietary stress in animals of treatment A and B, respectively. After an incubation time of 7 weeks amount, elemental and isotopic composition of collected faeces and exuviae as well as woodlice and remaining food were determined. The increase of delta15N-values of woodlice relative to the diet was 5.7% and 2.5% in treatments A and B, respectively, whereas delta13C-shifts were 1.0% and 1.6%, showing a reverse relationship. Modelling of elemental and isotopic mass balances indicated that faeces recycling explains the unexpected high 15N-enrichments. Moreover, 13C-enrichments were positively correlated to the degree of starvation. Considering the effects of starvation and recycling of faeces, stable isotopes represent a useful tool to elucidate trophic interactions in regenerating food webs. PMID:11501706

Rothe, J; Gleixner, G

2000-01-01

382

Food web structure of the coastal area adjacent to the Tagus estuary revealed by stable isotope analysis  

NASA Astrophysics Data System (ADS)

The identification of energy sources, pathways and trophic linkages among organisms is crucial for the understanding of food web dynamics. Stable isotopes were used to identify the trophic level of food web components and track the incorporation of organic matter of different origins in the coastal ecosystem adjacent to the Tagus estuary. It was shown that the river Tagus is a major source of organic carbon to this system. Also, the wide difference in ? 13C among the primary consumers allowed the identification of the pelagic and the benthic energy pathways. The maximum trophic level observed was 2.4 for Sepia officinalis. This value is indicative of a short food web. It was concluded that the diet of the upper trophic level species relies directly on the lower food web levels to a considerable extent, instead of relying mostly on intermediate trophic level species. Moreover, the ? 15N values of primary consumers were very close to that of particulate organic matter, probably due to poorly known processes occurring at the basis of the food web. This lowers the trophic length of the whole food web. Reliance on benthic affinity prey was high for all upper trophic level secondary consumers.

Vinagre, C.; Máguas, C.; Cabral, H. N.; Costa, M. J.

2012-01-01

383

Evidence of butyltin biomagnification along the Northern Adriatic food-web (Mediterranean Sea) elucidated by stable isotope ratios.  

PubMed

The biomagnification of tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), and total butyltins (?BT) was analyzed in the Northern Adriatic food-web (Mediterranean) considering trophodynamic interactions among species and carbon sources in the food-web. Although it is acknowledged that these contaminants bioaccumulate in marine organisms, it is still controversial whether they biomagnify along food-webs. A wide range of species was considered, from plankton feeders to top predators, whose trophic level (TL) was assessed measuring the biological enrichment of nitrogen stable isotopes (?(15)N). Carbon isotopic signature (?(13)C) was used to trace carbon sources in the food-web (terrestrial vs marine). At least one butyltin species was detected in the majority of samples, and TBT was the predominant contaminant. A significant positive relationship was found between TL and butyltin concentrations, implying food-web biomagnification. Coherently, the Trophic Magnification Factor resulted higher than 1, ranging between 3.88 for ?BT and 4.62 for DBT. A negative but not significant correlation was instead found between ?(13)C and butyltin concentrations, indicating a slight decreasing gradient of contaminants concentrations in species according to the coastal influence as carbon source in their diet. However, trophodynamic mechanisms are likely more important factors in determining butyltin distribution in the Northern Adriatic food-web. PMID:23465397

Fortibuoni, Tomaso; Noventa, Seta; Rampazzo, Federico; Gion, Claudia; Formalewicz, Malgorzata; Berto, Daniela; Raicevich, Saša

2013-04-01

384

The Impact of 850,000 Years of Climate Changes on the Structure and Dynamics of Mammal Food Webs  

PubMed Central

Most evidence of climate change impacts on food webs comes from modern studies and little is known about how ancient food webs have responded to climate changes in the past. Here, we integrate fossil evidence from 71 fossil sites, body-size relationships and actualism to reconstruct food webs for six large mammal communities that inhabited the Iberian Peninsula at different times during the Quaternary. We quantify the long-term dynamics of these food webs and study how their structure changed across the Quaternary, a period for which fossil data and climate changes are well known. Extinction, immigration and turnover rates were correlated with climate changes in the last 850 kyr. Yet, we find differences in the dynamics and structural properties of Pleistocene versus Holocene mammal communities that are not associated with glacial-interglacial cycles. Although all Quaternary mammal food webs were highly nested and robust to secondary extinctions, general food web properties changed in the Holocene. These results highlight the ability of communities to re-organize with the arrival of phylogenetically similar species without major structural changes, and the impact of climate change and super-generalist species (humans) on Iberian Holocene mammal communities. PMID:25207754

Nenzen, Hedvig K.; Montoya, Daniel; Varela, Sara

2014-01-01

385

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web.  

PubMed

The Scotia Sea ecosystem is a major component of the circumpolar Southern Ocean system, where productivity and predator demand for prey are high. The eastward-flowing Antarctic Circumpolar Current (ACC) and waters from the Weddell-Scotia Confluence dominate the physics of the Scotia Sea, leading to a strong advective flow, intense eddy activity and mixing. There is also strong seasonality, manifest by the changing irradiance and sea ice cover, which leads to shorter summers in the south. Summer phytoplankton blooms, which at times can cover an area of more than 0.5 million km2, probably result from the mixing of micronutrients into surface waters through the flow of the ACC over the Scotia Arc. This production is consumed by a range of species including Antarctic krill, which are the major prey item of large seabird and marine mammal populations. The flow of the ACC is steered north by the Scotia Arc, pushing polar water to lower latitudes, carrying with it krill during spring and summer, which subsidize food webs around South Georgia and the northern Scotia Arc. There is also marked interannual variability in winter sea ice distribution and sea surface temperatures that is linked to southern hemisphere-scale climate processes such as the El Niño-Southern Oscillation. This variation affects regional primary and secondary production and influences biogeochemical cycles. It also affects krill population dynamics and dispersal, which in turn impacts higher trophic level predator foraging, breeding performance and population dynamics. The ecosystem has also been highly perturbed as a result of harvesting over the last two centuries and significant ecological changes have also occurred in response to rapid regional warming during the second half of the twentieth century. This combination of historical perturbation and rapid regional change highlights that the Scotia Sea ecosystem is likely to show significant change over the next two to three decades, which may result in major ecological shifts. PMID:17405210

Murphy, E J; Watkins, J L; Trathan, P N; Reid, K; Meredith, M P; Thorpe, S E; Johnston, N M; Clarke, A; Tarling, G A; Collins, M A; Forcada, J; Shreeve, R S; Atkinson, A; Korb, R; Whitehouse, M J; Ward, P; Rodhouse, P G; Enderlein, P; Hirst, A G; Martin, A R; Hill, S L; Staniland, I J; Pond, D W; Briggs, D R; Cunningham, N J; Fleming, A H

2007-01-29

386

Common Patterns of Energy Flow and Biomass Distribution on Weighted Food Webs  

E-print Network

Weights of edges and nodes on food webs which are available from the empirical data hide much information about energy flows and biomass distributions in ecosystem. We define a set of variables related to weights for each species $i$, including the throughflow $T_i$, the total biomass $X_i$, and the dissipated flow $D_i$ (output to the environment) to uncover the following common patterns in 19 empirical weighted food webs: (1) DGBD distributions (Discrete version of a Generalized Beta Distribution), a kind of deformed Zipf's law, of energy flow and storage biomass; (2) The allometric scaling law $T_i\\propto X_i^{\\alpha}$, which can be viewed as the counterpart of the Kleiber's 3/4 law at the population level; (3) The dissipation law $D_i\\propto T_i^{\\beta}$; and (4) The gravity law, including univariate version $f_{ij}\\propto (T_iT_j)^{\\gamma}$ and bivariate approvement $f_{ij}\\propto T_i^{\\gamma_1}T_j^{\\gamma_2}$. These patterns are very common and significant in all collected webs, as a result, some remark...

Zhang, Jiang

2012-01-01

387

Trophic structure and mercury distribution in a Gulf of St. Lawrence (Canada) food web using stable isotope analysis  

Microsoft Academic Search

Even at low concentrations in the environment, mercury has the potential to biomagnify in food chains and reaches levels of concern in apex predators. The aim of this study was to relate the transfer of total mercury (THg) and methylmercury (MeHg) in a Gulf of St. Lawrence food web to the trophic structure, from primary consumers to seabirds, using stable

Raphael A. Lavoie; Craig E. Hebert; Jean-François Rail; Birgit M. Braune; Emmanuel Yumvihoze; Laura G. Hill; David R. S. Lean

2010-01-01

388

Appendix A: Study system and species We studied the food web based on the marsh elder, Iva frutescens (Asteraceae)  

E-print Network

1 Appendix A: Study system and species We studied the food web based on the marsh elder, Iva frutescens (Asteraceae) (henceforth Iva) (Plate A1). Iva is a common shrub at the terrestrial border of salt the Gulf Coast (Duncan and Duncan 1987). Iva quality as food for herbivores varies with latitude. Along

Pennings, Steven C.

389

Overview and History of the Food Web Dynamics Program of the Northeast Fisheries Science Center, Woods Hole, Massachusetts.  

National Technical Information Service (NTIS)

The authors provide an overview of the National Marine Fisheries Service (NMFS), Northeast Fisheries Science Center (NEFSC), Food Web Dynamics Program (FWDP). The FWDP's food habits database is one of the largest in the world and extends from 1973 to pres...

J. S. Link, F. P. Almeida

2000-01-01

390

Bioaccumulation patterns of methyl mercury and essential fatty acids in lacustrine planktonic food webs and fishB  

E-print Network

Bioaccumulation patterns of methyl mercury and essential fatty acids in lacustrine planktonic food September 2005 Available online 14 October 2005 Abstract Organisms of the planktonic food web convey categories of planktonic organisms ­ seston (10­64 Am), micro-(100­200 Am), meso-(200­500 Am

Mazumder, Asit

391

Antarctic Benthic Fauna in the Global Climate Change  

NASA Astrophysics Data System (ADS)

In the last 50 years a significant climatic shift has been observed along the Antarctic Peninsula (air and seawater temperature rise, glacial retreat, localized instances of lowered shallow waters salinities). Many Antarctic marine benthic invertebrates are adapted to specific environmental conditions (e.g. low stable temperatures, high salinity and oxygen content). Changes caused by global climate changes and subsequent glacial melting can be expected to have significant impacts on species physiology and distribution. The rise of sea water temperature coupled with such additional stress factors as melt water run-off, increased ice disturbance, disruption of food webs or invasion of alien species can be a serious problem for their long-term survival.

Kidawa, Anna; Janecki, Tomasz

2011-01-01

392

An innovative statistical approach to constructing a readily comprehensible food web for a demersal fish community  

NASA Astrophysics Data System (ADS)

Many food webs are so complex that it is difficult to distinguish the relationships between predators and their prey. We have therefore developed an approach that produces a food web which clearly demonstrates the strengths of the relationships between the predator guilds of demersal fish and their prey guilds in a coastal ecosystem. Subjecting volumetric dietary data for 35 abundant predators along the lower western Australia coast to cluster analysis and the SIMPROF routine separated the various species × length class combinations into 14 discrete predator guilds. Following nMDS ordination, the sequence of points for these predator guilds represented a 'trophic' hierarchy. This demonstrated that, with increasing body size, several species progressed upwards through this hierarchy, reflecting a marked change in diet, whereas others remained within the same guild. A novel use of cluster analysis and SIMPROF then identified each group of prey that was ingested in a common pattern across the full suite of predator guilds. This produced 12 discrete groups of taxa (prey guilds) that each typically comprised similar ecological/functional prey, which were then also aligned in a hierarchy. The hierarchical arrangements of the predator and prey guilds were plotted against each other to show the percentage contribution of each prey guild to the diet of each predator guild. The resultant shade plot demonstrates quantitatively how food resources are spread among the fish species and revealed that two prey guilds, one containing cephalopods and teleosts and the other small benthic/epibenthic crustaceans and polychaetes, were consumed by all predator guilds.

French, Ben; Clarke, K. Robert; Platell, Margaret E.; Potter, Ian C.

2013-07-01

393

River and Wetland Food Webs in Australia's Wet-Dry Tropics: General Principles and Implications for Management.  

NASA Astrophysics Data System (ADS)

The tropical rivers of northern Australia are internationally recognised for their high ecological and cultural values. They have largely unmodified flow regimes and are comparatively free of the impacts associated with intensive land use. However, there is growing demand for agricultural development and existing pressures, such as weeds and feral animals, threaten their ecological integrity. Using the international literature to provide a conceptual framework and drawing on limited published and unpublished data on rivers in northern Australia, we have derived five general principles about food webs and related ecosystem processes that both characterise tropical rivers of northern Australia and have important implications for their management. These are: (1) Seasonal hydrology is a strong driver of ecosystem processes and food web structure; (2) Hydrological connectivity is largely intact and underpins important terrestrial-aquatic food web subsidies; (3) River and wetland food webs are strongly dependent on algal production; (4) A few common macroconsumers species have a strong influence on benthic food webs; (5) Omnivory is widespread and food chains are short. These principles have implications for the management and protection of tropical rivers and wetlands of northern Australia and provide a framework for the formation of testable hypotheses in future research programs.

Douglas, M. M.; Bunn, S. E.; Davies, P. M.

2005-05-01

394

THE CONTRIBUTION OF MICROARTHROPODS TO ABOVE GROUND FOOD WEBS: A REVIEW AND MODEL OF BELOW GROUND TRANSFER IN A CONIFEROUS FOREST  

EPA Science Inventory

Although belowground food webs have received much attention, studies concerning microarthropods in nondetrital food webs are scarce. Because adult oribatid mites often number between 250,000-500,000/m(2) in coniferous forests, microarthropods are a potential food resource for mic...

395

Reorganization of Southern Ocean plankton ecosystem at the onset of Antarctic glaciation.  

PubMed

The circum-Antarctic Southern Ocean is an important region for global marine food webs and carbon cycling because of sea-ice formation and its unique plankton ecosystem. However, the mechanisms underlying the installation of this distinct ecosystem and the geological timing of its development remain unknown. Here, we show, on the basis of fossil marine dinoflagellate cyst records, that a major restructuring of the Southern Ocean plankton ecosystem occurred abruptly and concomitant with the first major Antarctic glaciation in the earliest Oligocene (~33.6 million years ago). This turnover marks a regime shift in zooplankton-phytoplankton interactions and community structure, which indicates the appearance of eutrophic and seasonally productive environments on the Antarctic margin. We conclude that earliest Oligocene cooling, ice-sheet expansion, and subsequent sea-ice formation were important drivers of biotic evolution in the Southern Ocean. PMID:23599491

Houben, Alexander J P; Bijl, Peter K; Pross, Jörg; Bohaty, Steven M; Passchier, Sandra; Stickley, Catherine E; Röhl, Ursula; Sugisaki, Saiko; Tauxe, Lisa; van de Flierdt, Tina; Olney, Matthew; Sangiorgi, Francesca; Sluijs, Appy; Escutia, Carlota; Brinkhuis, Henk; Dotti, Carlota Escutia; Klaus, Adam; Fehr, Annick; Williams, Trevor; Bendle, James A P; Carr, Stephanie A; Dunbar, Robert B; Flores, José-Abel; Gonzàlez, Jhon J; Hayden, Travis G; Iwai, Masao; Jimenez-Espejo, Francisco J; Katsuki, Kota; Kong, Gee Soo; McKay, Robert M; Nakai, Mutsumi; Pekar, Stephen F; Riesselman, Christina; Sakai, Toyosaburo; Salzmann, Ulrich; Shrivastava, Prakash K; Tuo, Shouting; Welsh, Kevin; Yamane, Masako

2013-04-19

396

Planktonic food webs revisited: Reanalysis of results from the linear inverse approach  

NASA Astrophysics Data System (ADS)

Identification of the trophic pathway that dominates a given planktonic assemblage is generally based on the distribution of biomasses among food-web compartments, or better, the flows of materials or energy among compartments. These flows are obtained by field observations and a posteriori analyses, including the linear inverse approach. In the present study, we re-analysed carbon flows obtained by inverse analysis at 32 stations in the global ocean and one large lake. Our results do not support two “classical” views of plankton ecology, i.e. that the herbivorous food web is dominated by mesozooplankton grazing on large phytoplankton, and the microbial food web is based on microzooplankton significantly consuming bacteria; our results suggest instead that phytoplankton are generally grazed by microzooplankton, of which they are the main food source. Furthermore, we identified the “phyto-microbial food web”, where microzooplankton largely feed on phytoplankton, in addition to the already known “poly-microbial food web”, where microzooplankton consume more or less equally various types of food. These unexpected results led to a (re)definition of the conceptual models corresponding to the four trophic pathways we found to exist in plankton, i.e. the herbivorous, multivorous, and two types of microbial food web. We illustrated the conceptual trophic pathways using carbon flows that were actually observed at representative stations. The latter can be calibrated to correspond to any field situation. Our study also provides researchers and managers with operational criteria for identifying the dominant trophic pathway in a planktonic assemblage, these criteria being based on the values of two carbon ratios that could be calculated from flow values that are relatively easy to estimate in the field. Ratio 1. Consumption rate of total phytoplankton by microzooplankton divided by total consumption rate by microzooplankton [phtTOmic/D1, where D1 = phtTOmic + bacTOmic + (doc + det)TOmic]. Ratio 2. Consumption rate of bacteria by microzooplankton divided by total consumption rate by microzooplankton [bacTOmic/D1]. Ratio 3. Consumption rate of detrital and dissolved organic carbon by microzooplankton divided by total consumption rate by microzooplankton [(detTOmic + docTOmic)/D1]. Although consumption of DOC by microzooplankton is generally assumed to be negligible in most field or experimental studies, that potential flow is often included in the food-web structure used for inverse analysis (e.g. Fig. 1). Ratio 4. Total phytoplankton net production divided by net production of potential microzooplankton food [Pnetpht/D2, where Pnetpht = (Pgropht - phtTOres) and D2 = Pnetpht + Pnetbac + Pnetdet + Pnetdoc]. Ratio 5. Net bacterial production divided by net production of potential microzooplankton food [Pnetbac/D2, where Pnetbac = (docTObac - bacTOres)]. Ratio 6. Net production of dissolved and detrital organic carbon divided by net production of potential microzooplankton food [(Pnetdet + Pnetdoc)/D2, where Pnetdet = bacTOdet + phtTOdet + micTOdet + mesTOdet] and Pnetdoc = (bacTOdoc + phtTOdoc + micTOdoc + mesTOdoc + detTOdoc). Ratio 7. Picophytoplankton net production divided by total phytoplankton net production [Pnetph1/Pnetpht, where Pnetph1 = (Pgroph1 - ph1TOres)]. Ratio 8. Consumption rate of total phytoplankton by microzooplankton divided by the consumption rate of total phytoplankton by micro- and mesozooplankton [phtTOmic/(phtTOmic + phtTOmes)]. Ratios 7 and 8 were among the six ratios proposed by Legendre and Rassoulzadegan (1995) to assess the dominance of different trophic pathways in natural planktonic communities. Their four other ratios could not be implemented in the present study because they used nitrogen whereas the currency of the linear inverse studies we reanalysed here was carbon. Our first six ratios above include in the determination of trophic pathways two effects related to microzooplankton, i.e. the differential feeding of microzooplankton on its potential food sources (ratios 1-3), and the differ

Hlaili, Asma Sakka; Niquil, Nathalie; Legendre, Louis

2014-01-01

397

Antarctic Meteorology Online from the British Antarctic Survey  

NSDL National Science Digital Library

The Antarctic Meteorology Online Web site is provided by the British Antarctic Survey and the Natural Environment Research Council. Visitors will find weather reports provided by the dozens of stations located in the Antarctic. The Web master has made these data accessible by each specific station; by a clickable map; by a list of all land, ship, or buoy stations; or by an oracle database interface. The reports are at least 10 minutes old and are normally not more than six hours old. The information provided includes a graph of pressure and temperature, as well as links to previous reports, which make the site a good and easily accessible resource. This site is also reviewed in the November 27, 2002 Scout Report.

2001-01-01

398

Global uncertainty and sensitivity analysis of a food-web bioaccumulation model.  

PubMed

A global uncertainty and sensitivity analysis (UA/SA) of a state-of-the-art, food-web bioaccumulation model was carried out. We used an efficient screening analysis technique to identify the subset of the most relevant input factors among the whole set of 227 model parameters. A quantitative UA/SA was then applied to this subset to rank the relevance of the parameters and to partition the variance of the model output among them by means of a nonlinear regression of the outcomes of 1,000 Monte Carlo simulations. The concentrations of four representative persistent organic pollutants (POPs) in two representative species of the coastal marine food web of the Lagoon of Venice (Italy) were taken as model outputs. The screening analysis showed that the ranking was remarkably different in relation to the species and chemical being considered. The subsequent Monte Carlo-based quantitative analysis pointed out that the relationships among some of the parameters and the model outputs were nonlinear. The nonlinear regression showed that the fraction of output variance accounted for by each parameter was strongly dependent on the range of the octanol-water partition coefficient (K(OW)) values being considered. For the less hydrophobic chemicals, the main sources of model uncertainty were the parameters related to the respiratory bioaccumulation, whereas for the more hydrophobic ones, K(OW) and the other parameters related to the dietary uptake explained the largest fractions of the variance of the chemical concentrations in the organisms. The analysis highlighted that efforts are still needed for reducing uncertainty of model parameters to get reliable results from the application of food web bioaccumulation models. PMID:19391679

Ciavatta, Stefano; Lovato, Tomas; Ratto, Marco; Pastres, Roberto

2009-04-01

399

Terrestrial contributions to the aquatic food web in the middle Yangtze River.  

PubMed

Understanding the carbon sources supporting aquatic consumers in large rivers is essential for the protection of ecological integrity and for wildlife management. The relative importance of terrestrial and algal carbon to the aquatic food webs is still under intensive debate. The Yangtze River is the largest river in China and the third longest river in the world. The completion of the Three Gorges Dam (TGD) in 2003 has significantly altered the hydrological regime of the middle Yangtze River, but its immediate impact on carbon sources supporting the river food web is unknown. In this study, potential production sources from riparian and the main river channel, and selected aquatic consumers (invertebrates and fish) at an upstream constricted-channel site (Luoqi), a midstream estuarine site (Huanghua) and a near dam limnetic site (Maoping) of the TGD were collected for stable isotope (?13C and ?15N) and IsoSource analyses. Model estimates indicated that terrestrial plants were the dominant carbon sources supporting the consumer taxa at the three study sites. Algal production appeared to play a supplemental role in supporting consumer production. The contribution from C4 plants was more important than that of C3 plants at the upstream site while C3 plants were the more important carbon source to the consumers at the two impacted sites (Huanghua and Maoping), particularly at the midstream site. There was no trend of increase in the contribution of autochthonous production from the upstream to the downstream sites as the flow rate decreased dramatically along the main river channel due to the construction of TGD. Our findings, along with recent studies in rivers and lakes, are contradictory to studies that demonstrate the importance of algal carbon in the aquatic food web. Differences in system geomorphology, hydrology, habitat heterogeneity, and land use may account for these contradictory findings reported in various studies. PMID:25047656

Wang, Jianzhu; Gu, Binhe; Huang, Jianhui; Han, Xingguo; Lin, Guanghui; Zheng, Fawen; Li, Yuncong

2014-01-01

400

Bioaccumulation syndrome: identifying factors that make some stream food webs prone to elevated mercury bioaccumulation  

PubMed Central

Mercury is a ubiquitous contaminant in aquatic ecosystems, posing a significant health risk to humans and wildlife that eat fish. Mercury accumulates in aquatic food webs as methylmercury (MeHg), a particularly toxic and persistent organic mercury compound. While mercury in the environment originates largely from anthropogenic activities, MeHg accumulation in freshwater aquatic food webs is not a simple function of local or regional mercury pollution inputs. Studies show that even sites with similar mercury inputs can produce fish with mercury concentrations ranging over an order of magnitude. While much of the foundational work to identify the drivers of variation in mercury accumulation has focused on freshwater lakes, mercury contamination in stream ecosystems is emerging as an important research area. Here, we review recent research on mercury accumulation in stream-dwelling organisms. Taking a hierarchical approach, we identify a suite of characteristics of individual consumers, food webs, streams, watersheds, and regions that are consistently associated with elevated MeHg concentrations in stream fish. We delineate a conceptual, mechanistic basis for explaining the ecological processes that underlie this vulnerability to MeHg. Key factors, including suppressed individual growth of consumers, low rates of primary and secondary production, hydrologic connection to methylation sites (e.g. wetlands), heavily forested catchments, and acidification are frequently associated with increased MeHg concentrations in fish across both streams and lakes. Hence, we propose that these interacting factors define a syndrome of characteristics that drive high MeHg production and bioaccumulation rates across these freshwater aquatic ecosystems. Finally, based on an understanding of the ecological drivers of MeHg accumulation, we identify situations when anthropogenic effects and management practices could significantly exacerbate or ameliorate MeHg accumulation in stream fish. PMID:20536817

Ward, Darren M.; Nislow, Keith H.; Folt, Carol L.

2010-01-01

401

Microbial food web dynamics along a soil chronosequence of a glacier forefield  

NASA Astrophysics Data System (ADS)

Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web dynamics in soils at different developmental stages. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PLFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria, especially actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

Esperschütz, J.; Pérez-de-Mora, A.; Schreiner, K.; Welzl, G.; Buegger, F.; Zeyer, J.; Hagedorn, F.; Munch, J. C.; Schloter, M.

2011-11-01

402

Microbial food web dynamics along a soil chronosequence of a glacier forefield  

NASA Astrophysics Data System (ADS)

Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web development at differently developed soils. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PUFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria and actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

Esperschütz, J.; Pérez-de-Mora, A.; Schreiner, K.; Welzl, G.; Buegger, F.; Zeyer, J.; Hagedorn, F.; Munch, J. C.; Schloter, M.

2011-02-01

403

Linking Food Webs and Biogeochemical Processes in Wetlands: Insights From Sulfur Isotopes  

NASA Astrophysics Data System (ADS)

To better understand the transfer of nutrients into prairie wetland food webs we have investigated the cycling of S (via S isotope systematics and geochemistry) in a prairie wetland landscape by characterizing sources (ground water, interstitial water, surface water) and processes in a small catchment comprised of four wetlands in eastern South Dakota. We focused on S to derive process information that is not generally available from carbon isotopes alone. The wetlands chosen for study spanned a considerable range in SO4 concentration (0.1-13.6 mM), which corresponded with landscape position. Ground water ?34SSO4 values remained relatively constant (mean = -13.2 per mil) through time. However, ?34SSO4 values of wetland surface waters ranged from -2.9 to -30.0 per mil (CDT) and were negatively correlated with SO4 concentrations (p<0.05). The isotopic variability of surface water SO4 resulted from mixing with re-oxidized sulfides associated with recently flushed wetland soils. The ?34S signatures of wetland primary (Gastropoda: Stagnicola elodes) and secondary (Odonata: Anax sp.) consumers were significantly related to surface water ?34SSO4 values (p<0.05) suggesting that food web components were responding to changes in the isotopic composition of the S source. Both primary and secondary consumer ?34S signatures differed between wetlands (ANOVA, p<0.05). These data illustrate the complexity of S cycling in prairie wetlands and the influence of wetland hydrologic and biogeochemical processes on prairie wetland food webs. Additionally, this work has demonstrated that sulfur isotopes can provide unique source and process information that cannot be derived from traditional carbon and nitrogen isotope studies.

Stricker, C. A.; Guntenspergen, G. R.; Rye, R. O.

2005-05-01

404

Divergent composition but similar function of soil food webs of individual plants: plant species and community effects.  

PubMed

Soils are extremely rich in biodiversity, and soil organisms play pivotal roles in supporting terrestrial life, but the role that individual plants and plant communities play in influencing the diversity and functioning of soil food webs remains highly debated. Plants, as primary producers and providers of resources to the soil food web, are of vital importance for the composition, structure, and functioning of soil communities. However, whether natural soil food webs that are completely open to immigration and emigration differ underneath individual plants remains unknown. In a biodiversity restoration experiment we first compared the soil nematode communities of 228 individual plants belonging to eight herbaceous species. We included grass, leguminous, and non-leguminous species. Each individual plant grew intermingled with other species, but all plant species had a different nematode community. Moreover, nematode communities were more similar when plant individuals were growing in the same as compared to different plant communities, and these effects were most apparent for the groups of bacterivorous, carnivorous, and omnivorous nematodes. Subsequently, we analyzed the composition, structure, and functioning of the complete soil food webs of 58 individual plants, belonging to two of the plant species, Lotus corniculatus (Fabaceae) and Plantago lanceolata (Plantaginaceae). We isolated and identified more than 150 taxa/groups of soil organisms. The soil community composition and structure of the entire food webs were influenced both by the species identity of the plant individual and the surrounding plant community. Unexpectedly, plant identity had the strongest effects on decomposing soil organisms, widely believed to be generalist feeders. In contrast, quantitative food web modeling showed that the composition of the plant community influenced nitrogen mineralization under individual plants, but that plant species identity did not affect nitrogen or carbon mineralization or food web stability. Hence, the composition and structure of entire soil food webs vary at the scale of individual plants and are strongly influenced by the species identity of the plant. However, the ecosystem functions these food webs provide are determined by the identity of the entire plant community. PMID:21058562

Bezemer, T M; Fountain, M T; Barea, J M; Christensen, S; Dekker, S C; Duyts, H; van Hal, R; Harvey, J A; Hedlund, K; Maraun, M; Mikola, J; Mladenov, A G; Robin, C; de Ruiter, P C; Scheu, S; Setälä, H; Smilauer, P; van der Putten, W H

2010-10-01

405

The Role of Highly Unsaturated Fatty Acids in Aquatic Food Webs  

NASA Astrophysics Data System (ADS)

Highly unsaturated fatty acids (HUFAs) are important molecules transferred across the plant-animal interface in aquatic food webs. Defined here as carbon chains of length 18 (carbons) or more, with a double bond in the third (Omega 3) or sixth (Omega 6) bond from the methyl end, HUFAs are formed in primary producers (phytoplankton). With limited abilities to synthesize de novo, consumers and higher trophic organisms are required to obtain their HUFAs primarily from diet. Bioconversion of HUFAs from one form to another is in theory possible, as is synthesis via elongation and the transformation of a saturated to highly saturated fatty acid, but the enzymes required for these processes are absent in most species. HUFAs are hypothesized to be somatic growth limiting compounds for herbivorous zooplankton and have been shown to be critical for juvenile fish growth and wellbeing. Zooplankton tend to vary their fatty acid concentrations, collection strategies and utilization methods based on taxonomy, and various mechanisms have been suggested to account for these differences i.e., seasonal and nervous system hypotheses. Considering also the facts that copepods overwinter in an active state while daphnids overwinter as resting eggs, and that copepods tend to accumulate Docosahexaenoic acid (DHA) through collection and bioconversion, while daphnids focus on Eicosapentaenoic acid (EPA), one can link high DHA concentrations to active overwintering; but both EPA and DHA have similar melting points, putting DHA's cold weather adaptation abilities into question. Another characteristic setting copepods apart from daphnids is nervous system complexity: copepod axons are coated in thick myelin sheaths, permitting rapid neural processing, such as rapid prey attack and intelligent predator avoidance; DHA may be required for the proper functioning of copepod neurons. Recent modeling results have suggested food webs with high quality primary producers (species high in HUFAs, i.e. diatoms), at their base can attain inverted biomass distributions with efficient energy transfer between trophic levels, making HUFA pathways in aquatic food webs of special interest to fisheries and environmental managers. Built on our previous work, which implicitly considered HUFAs through a proxy (generic food quality term, which also indexes ingestibility, digestibility and toxicity), our aim is to elucidate the underlying mechanisms controlling HUFA transport through the lower aquatic food web, with an emphasis on the hypothesized somatic growth limiting potential. A biochemical submodel coupled to a plankton model has been formulated and calibrated, accounting explicitly for the omega 3 and omega 6 families of fatty acids; specifically, Alpha Linoleic acid (ALA, a precursor to EPA), EPA and DHA. Further insights into the role of HUFAs on food web dynamics and the subsequent implications on ecosystem functioning are gained through bifurcation analysis of the model. Our research aims to elucidate the existing gaps in the literature pertaining to the role and impact of HUFAs on plankton dynamics, which have traditionally been thought to be driven by stoichiometric ratios and limiting nutrients. In this study, we challenge the notion of nutrients being the primary driving factor of aquatic ecosystem patterns by introducing a modeling framework that accounts for the interplay between nutrients and HUFAs.

Perhar, G.; Arhonditsis, G. B.

2009-05-01

406

Prey Vulnerability Limits Top-Down Control and Alters Reciprocal Feedbacks in a Subsidized Model Food Web  

PubMed Central

Resource subsidies increase the productivity of recipient food webs and can affect ecosystem dynamics. Subsidies of prey often support elevated predator biomass which may intensify top-down control and reduce the flow of reciprocal subsidies into adjacent ecosystems. However, top-down control in subsidized food webs may be limited if primary consumers posses morphological or behavioral traits that limit vulnerability to predation. In forested streams, terrestrial prey support high predator biomass creating the potential for strong top-down control, however armored primary consumers often dominate the invertebrate assemblage. Using empirically based simulation models, we tested the response of stream food webs to variations in subsidy magnitude, prey vulnerability, and the presence of two top predators. While terrestrial prey inputs increased predator biomass (+12%), the presence of armored primary consumers inhibited top-down control, and diverted most aquatic energy (?75%) into the riparian forest through aquatic insect emergence. Food webs without armored invertebrates experienced strong trophic cascades, resulting in higher algal (?50%) and detrital (?1600%) biomass, and reduced insect emergence (?90%). These results suggest prey vulnerability can mediate food web responses to subsidies, and that top-down control can be arrested even when predator-invulnerable consumers are uncommon (20%) regardless of the level of subsidy. PMID:24465732

Atlas, William I.; Palen, Wendy J.

2014-01-01

407

Indirect food web interactions mediated by predator-rodent dynamics: relative roles of lemmings and voles.  

PubMed

Production cycles in birds are proposed as prime cases of indirect interactions in food webs. They are thought to be driven by predators switching from rodents to bird nests in the crash phase of rodent population cycles. Although rodent cycles are geographically widespread and found in different rodent taxa, bird production cycles appear to be most profound in the high Arctic where lemmings dominate. We hypothesized that this may be due to arctic lemmings inducing stronger predator responses than boreal voles. We tested this hypothesis by estimating predation rates in dummy bird nests during a rodent cycle in low-Arctic tundra. Here, the rodent community consists of a spatially variable mix of one lemming (Lemmus lemmus) and two vole species (Myodes rufocanus and Microtus oeconomus) with similar abundances. In consistence with our hypothesis, lemming peak abundances predicted well crash-phase nest predation rates, whereas the vole abundances had no predictive ability. Corvids were found to be the most important nest predators. Lemmings appear to be accessible to the whole predator community which makes them particularly powerful drivers of food web dynamics. PMID:24173526

Ims, Rolf A; Henden, John-André; Thingnes, Anders V; Killengreen, Siw T

2013-01-01

408

Millennial-aged organic carbon subsidies to a modern river food web.  

PubMed

Recent studies indicate that highly aged material is a major component of organic matter transported by most rivers. However, few studies have used natural 14C to trace the potential entry of this aged material into modern river food webs. Here we use natural abundance 14C, 13C, and deuterium (2H) to trace the contribution of aged and contemporary organic matter to an important group of consumers, crustacean zooplankton, in a large temperate river (the Hudson River, New York, USA). Zooplankton were highly 14C depleted (mean delta14C = -240 per thousand) compared to modern primary production in the river or its watershed (delta14C = -60 per thousand to +50 per thousand). In order to account for the observed 14C depletion, zooplankton must be subsidized by highly aged particulate organic carbon. IsoSource modeling suggests that the range of the aged dietary subsidy is between approximately 57%, if the aged organic matter source was produced 3400 years ago, and approximately 21%, if the organic carbon used is > or = 50 000 years in age, including fossil material that is millions of years in age. The magnitude of this aged carbon subsidy to river zooplankton suggests that modern river food webs may in some cases be buffered from the limitations set by present-day primary production. PMID:20836460

Caraco, Nina; Bauer, James E; Cole, Jonathan J; Petsch, Steven; Raymond, Peter

2010-08-01

409

Invasive crayfish as vectors of mercury in freshwater food webs of the Pacific Northwest.  

PubMed

Invasive species are important drivers of environmental change in aquatic ecosystems and can alter habitat characteristics, community composition, and ecosystem energetics. Such changes have important implications for many ecosystem processes, including the bioaccumulation and biomagnification of contaminants through food webs. Mercury concentrations were measured in 2 nonnative and 1 native crayfish species from western Oregon (USA). Nonnative red swamp crayfish had mercury concentrations similar to those in native signal crayfish (0.29?±?0.05?µg/g dry wt and 0.36?±?0.06?µg/g dry wt, respectively), whereas the nonnative ringed crayfish had lower mercury concentrations (0.10?±?0.02?µg/g dry wt) than either of the other species. The mean energy content of muscle was similar between the native signal crayfish and nonnative ringed crayfish but was significantly higher in the nonnative red swamp crayfish. Across species, mercury concentrations were negatively correlated with energy density. Such energetic differences could exacerbate changes in mercury transfer through trophic pathways of food webs, especially via alterations to the growth dynamics of consumers. Thus, it is important to consider the role of energy content in determining effective mercury exposure even when mercury concentrations on a per-unit mass basis do not differ between species. Environ Toxicol Chem 2014;33:2639-2645. Published 2014 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US Government work and as such, is in the public domain in the United States of America. PMID:25143076

Johnson, Branden L; Willacker, James J; Eagles-Smith, Collin A; Pearl, Christopher A; Adams, Michael J

2014-11-01

410

Herbivore diet breadth mediates the cascading effects of carnivores in food webs.  

PubMed

Predicting the impact of carnivores on plants has challenged community and food web ecologists for decades. At the same time, the role of predators in the evolution of herbivore dietary specialization has been an unresolved issue in evolutionary ecology. Here, we integrate these perspectives by testing the role of herbivore diet breadth as a predictor of top-down effects of avian predators on herbivores and plants in a forest food web. Using experimental bird exclosures to study a complex community of trees, caterpillars, and birds, we found a robust positive association between caterpillar diet breadth (phylodiversity of host plants used) and the strength of bird predation across 41 caterpillar and eight tree species. Dietary specialization was associated with increased enemy-free space for both camouflaged (n = 33) and warningly signaled (n = 8) caterpillar species. Furthermore, dietary specialization was associated with increased crypsis (camouflaged species only) and more stereotyped resting poses (camouflaged and warningly signaled species), but was unrelated to caterpillar body size. These dynamics in turn cascaded down to plants: a metaanalysis (n = 15 tree species) showed the beneficial effect of birds on trees (i.e., reduced leaf damage) decreased with the proportion of dietary specialist taxa composing a tree species' herbivore fauna. We conclude that herbivore diet breadth is a key functional trait underlying the trophic effects of carnivores on both herbivores and plants. PMID:24979778

Singer, Michael S; Lichter-Marck, Isaac H; Farkas, Timothy E; Aaron, Eric; Whitney, Kenneth D; Mooney, Kailen A

2014-07-01

411

Assessing the Health of Puget Sound's Pelagic Food Web at Multiple Trophic Levels  

NASA Astrophysics Data System (ADS)

Puget Sound is an estuarine fjord in the northwestern United State surrounded by variable upland uses, ranging from industrial and urban to agricultural to forested lands. The quality of Puget Sound's ecosystem is under scrutiny because of the biological resources that depend on its function. In 2011, we undertook a study of the Sound's pelagic food web that measured water quality, microbial parameters, and abundance of higher trophic levels including gelatinous zooplankton, forage fish, and salmon. More than 75 sites spanning the latitudinal expanse of Puget Sound and the range of developed and agricultural land uses were sampled monthly from April to October. Strong relationships between water quality and microbial parameters suggest that microbes may modulate water quality indicators, such as dissolved inorganic nitrogen and pH, and that land use may be an influential factor. Basins within Puget Sound exhibit distinct biological profiles at the microbial and macrobiotic levels, emphasizing that Puget Sound is not a homogenous water body and suggesting that informative food web indicators may vary across the basins.

Rhodes, L. D.; Greene, C. M.; Rice, C. A.; Hall, J. E.; Baxter, A. E.; Naman, S. M.; Chamberlin, J.

2012-12-01

412

Contrasting Food Web Factor and Body Size Relationships with Hg and Se Concentrations in Marine Biota  

PubMed Central

Marine fish and shellfish are primary sources of human exposure to mercury, a potentially toxic metal, and selenium, an essential element that may protect against mercury bioaccumulation and toxicity. Yet we lack a thorough understanding of Hg and Se patterns in common marine taxa, particularly those that are commercially important, and how food web and body size factors differ in their influence on Hg and Se patterns. We compared Hg and Se content among marine fish and invertebrate taxa collected from Long Island, NY, and examined associations between Hg, Se, body length, trophic level (measured by ?15N) and degree of pelagic feeding (measured by ?13C). Finfish, particularly shark, had high Hg content whereas bivalves generally had high Se content. Both taxonomic differences and variability were larger for Hg than Se, and Hg content explained most of the variation in Hg:Se molar ratios among taxa. Finally, Hg was more strongly associated with length and trophic level across taxa than Se, consistent with a greater degree of Hg bioaccumulation in the body over time, and biomagnification through the food web, respectively. Overall, our findings indicate distinct taxonomic and ecological Hg and Se patterns in commercially important marine biota, and these patterns have nutritional and toxicological implications for seafood-consuming wildlife and humans. PMID:24019976

Karimi, Roxanne; Frisk, Michael; Fisher, Nicholas S.

2013-01-01

413

Distribution of PCB congeners in seven lake systems: Interactions between sediment and food-web transport  

SciTech Connect

A study was conducted to examine the role of two processes, partitioning of PCBs between sediment and biota and food-web transport, in determining the concentration of PCB congeners in the biota of seven lakes. Biota PCB concentration (lipid)-to-sediment PCB concentration (organic carbon), or BSF, ratios were calculated as markers of the partitioning of PCBs between biota and sediment, and biota PCB concentration (lipid)-to-zooplankton PCB concentration (lipid), or BAS, ratios were calculated as markers of the transport of PCBs through food webs. The lakes ranged from a shallow, well-mixed lake with a historic input of Aroclor technical mixtures to deeper, oligotrophic systems in which atmospheric deposition was the only known source. BSF ratios ranged from approximately one in cyprinids and zooplankton in all lakes to 30 in yellow perch in one lake. A significant correlation between lake maximum depth and combined BSF ratios for all biota indicated that PCBs were generally more available for accumulation in the shallower lakes, regardless of the PCB source. Principal component analysis (PCA) showed that the biota in the shallower lakes had higher ratios of higher chlorinated congeners, suggesting that predictions of equal concentrations of hydrophobic contaminants on a lipid basis in sediment and lower trophic levels may significantly underestimate the accumulation of very hydrophobic compounds in the organisms of some lake systems. BAF ratios ranged from approximately one in the lower trophic levels to approximately 10 in lake trout.

MacDonald, C.R.; Metcalfe, C.D.; Balch, G.C.; Metcalfe, T.L. (Trent Univ., Peterborough, Ontario (Canada). Environmental and Resource Studies)

1993-11-01

414

Indirect food web interactions mediated by predator-rodent dynamics: relative roles of lemmings and voles  

PubMed Central

Production cycles in birds are proposed as prime cases of indirect interactions in food webs. They are thought to be driven by predators switching from rodents to bird nests in the crash phase of rodent population cycles. Although rodent cycles are geographically widespread and found in different rodent taxa, bird production cycles appear to be most profound in the high Arctic where lemmings dominate. We hypothesized that this may be due to arctic lemmings inducing stronger predator responses than boreal voles. We tested this hypothesis by estimating predation rates in dummy bird nests during a rodent cycle in low-Arctic tundra. Here, the rodent community consists of a spatially variable mix of one lemming (Lemmus lemmus) and two vole species (Myodes rufocanus and Microtus oeconomus) with similar abundances. In consistence with our hypothesis, lemming peak abundances predicted well crash-phase nest predation rates, whereas the vole abundances had no predictive ability. Corvids were found to be the most important nest predators. Lemmings appear to be accessible to the whole predator community which makes them particularly powerful drivers of food web dynamics. PMID:24173526

Ims, Rolf A.; Henden, John-Andre; Thingnes, Anders V.; Killengreen, Siw T.

2013-01-01

415

Tracing Carbon Sources through Aquatic and Terrestrial Food Webs Using Amino Acid Stable Isotope Fingerprinting  

PubMed Central

Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring ?13C patterns among amino acids (?13CAA) could distinguish between multiple aquatic and terrestrial primary production sources. We found that ?13CAA patterns in contrast to bulk ?13C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their ?13CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk ?13C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer ?13C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs. PMID:24069196

Larsen, Thomas; Ventura, Marc; Andersen, Nils; O'Brien, Diane M.; Piatkowski, Uwe; McCarthy, Matthew D.

2013-01-01

416

Black carbon inclusive multichemical modeling of PBDE and PCB biomagnification and -transformation in estuarine food webs.  

PubMed

Bioavailability and bioaccumulation of polybrominated diphenylethers (PBDEs) are affected by adsorption on black carbon (BC) and metabolism in biota, respectively. Recent studies have addressed these two processes separately, illustrating their importance in assessing contaminant dynamics. In order to properly examine biomagnification of polychlorinated biphenyls (PCBs) and PBDEs in an estuarine food-web, here we set up a black carbon inclusive multichemical model. A dual domain sorption model, which accounted for sorption to organic matter (OM) and black carbon (BC), was used to estimate aqueous phase concentrations from the measured chemical concentrations in suspended solids. We adapted a previously published multichemical model that tracks the movement of a parent compound and its metabolites in each organism and within its food web. First, the model was calibrated for seven PCB congeners assuming negligible metabolism. Subsequently, PBDE biomagnification was modeled, including biotransformation and bioformation of PBDE congeners, keeping the other model parameters the same. The integrated model was capable of predicting trophic magnification factors (TMF) within error limits. PBDE metabolic half-lives ranged 21-415 days and agreed to literature data. The results showed importance of including BC as an adsorbing phase, and biotransformation and bioformation of PBDEs for a proper assessment of their dynamics in aquatic systems. PMID:20828201

Di Paolo, Carolina; Gandhi, Nilima; Bhavsar, Satyendra P; Van den Heuvel-Greve, Martine; Koelmans, Albert A

2010-10-01

417

Methane-derived carbon in the benthic food web in stream impoundments.  

PubMed

Methane gas (CH4) has been identified as an important alternative source of carbon and energy in some freshwater food webs. CH4 is oxidized by methane oxidizing bacteria (MOB), and subsequently utilized by chironomid larvae, which may exhibit low ?13C values. This has been shown for chironomid larvae collected from lakes, streams and backwater pools. However, the relationship between CH4 concentrations and ?13C values of chironomid larvae for in-stream impoundments is unknown. CH4 concentrations were measured in eleven in-stream impoundments located in the Queich River catchment area, South-western Germany. Furthermore, the ?13C values of two subfamilies of chironomid larvae (i.e. Chironomini and Tanypodinae) were determined and correlated with CH4 concentrations. Chironomini larvae had lower mean ?13C values (-29.2 to -25.5 ‰), than Tanypodinae larvae (-26.9 to -25.3 ‰). No significant relationships were established between CH4 concentrations and ?13C values of chironomids (p>0.05). Mean ?13C values of chironomid larvae (mean: -26.8‰, range: -29.2‰ to -25.3‰) were similar to those of sedimentary organic matter (SOM) (mean: -28.4‰, range: -29.3‰ to -27.1‰) and tree leaf litter (mean: -29.8 ‰, range: -30.5‰ to -29.1‰). We suggest that CH4 concentration has limited influence on the benthic food web in stream impoundments. PMID:25360609

Mbaka, John Gichimu; Somlai, Celia; Köpfer, Denis; Maeck, Andreas; Lorke, Andreas; Schäfer, Ralf B

2014-01-01

418

Invasive crayfish as vectors of mercury in freshwater food webs of the Pacific Northwest  

USGS Publications Warehouse

Invasive species are important drivers of environmental change in aquatic ecosystems and can alter habitat characteristics, community composition, and ecosystem energetics. Such changes have important implications for many ecosystem processes, including the bioaccumulation and biomagnification of contaminants through food webs. Mercury concentrations were measured in 2 nonnative and 1 native crayfish species from western Oregon (USA). Nonnative red swamp crayfish had mercury concentrations similar to those in native signal crayfish (0.29?±?0.05?µg/g dry wt and 0.36?±?0.06?µg/g dry wt, respectively), whereas the nonnative ringed crayfish had lower mercury concentrations (0.10?±?0.02?µg/g dry wt) than either of the other species. The mean energy content of muscle was similar between the native signal crayfish and nonnative ringed crayfish but was significantly higher in the nonnative red swamp crayfish. Across species, mercury concentrations were negatively correlated with energy density. Such energetic differences could exacerbate changes in mercury transfer through trophic pathways of food webs, especially via alterations to the growth dynamics of consumers. Thus, it is important to consider the role of energy content in determining effective mercury exposure even when mercury concentrations on a per-unit mass basis do not differ between species.

Johnson, Branden L.; Willacker, James J.; Eagles-Smith, Collin A.; Pearl, Christopher; Adams, Michael J.

2014-01-01

419

Incorporation of terrestrial wetland material into aquatic food webs in a tropical estuarine wetland  

NASA Astrophysics Data System (ADS)

Carbon and nitrogen stable isotope composition of a range of organisms collected from two intermittently connected floodplain pools in the Ross River estuary were analysed to assess the extent to which carbon fixed by terrestrial wetland producers is incorporated into adjacent aquatic food webs. The two pools differed in surrounding vegetation with one surrounded by mangroves and the other by the salt couch Sporobolus virginicus. At both pools, animals showed differences in ? 13C, indicating differences in sources of carbon. Since ? 13C values of C 3 mangroves (-29.7 to -26.3‰) were very different from those of the C 4 salt couch (-16.3 to -15.4‰), it was possible to determine the importance of terrestrial wetland producers by comparing isotope values of consumers between sites, in a species by species approach. Most animal species collected showed lower ? 13C at the mangrove pool than at the Sporobolus pool, which indicates a greater incorporation of mangrove carbon at the mangrove pool. However, the animals' isotopic shifts were also similar to that shown by epiphytes, and hence the differences in animal ? 13C could also be a result of a dependence on these producers. The IsoSource model was useful to clarify this question, indicating that mangrove and salt marsh material was a crucial contributor to the diet of several fish and invertebrate species at both sites, indicating that carbon of terrestrial origin is incorporated in the estuarine food web.

Abrantes, Kátya; Sheaves, Marcus

2008-11-01

420

Methane-Derived Carbon in the Benthic Food Web in Stream Impoundments  

PubMed Central

Methane gas (CH4) has been identified as an important alternative source of carbon and energy in some freshwater food webs. CH4 is oxidized by methane oxidizing bacteria (MOB), and subsequently utilized by chironomid larvae, which may exhibit low ?13C values. This has been shown for chironomid larvae collected from lakes, streams and backwater pools. However, the relationship between CH4 concentrations and ?13C values of chironomid larvae for in-stream impoundments is unknown. CH4 concentrations were measured in eleven in-stream impoundments located in the Queich River catchment area, South-western Germany. Furthermore, the ?13C values of two subfamilies of chironomid larvae (i.e. Chironomini and Tanypodinae) were determined and correlated with CH4 concentrations. Chironomini larvae had lower mean ?13C values (?29.2 to ?25.5 ‰), than Tanypodinae larvae (?26.9 to ?25.3 ‰). No significant relationships were established between CH4 concentrations and ?13C values of chironomids (p>0.05). Mean ?13C values of chironomid larvae (mean: ?26.8‰, range: ?29.2‰ to ?25.3‰) were similar to those of sedimentary organic matter (SOM) (mean: ?28.4‰, range: ?29.3‰ to ?27.1‰) and tree leaf litter (mean: ?29.8 ‰, range: ?30.5‰ to ?29.1‰). We suggest that CH4 concentration has limited influence on the benthic food web in stream impoundments. PMID:25360609

Mbaka, John Gichimu; Somlai, Celia; Köpfer, Denis; Maeck, Andreas; Lorke, Andreas; Schäfer, Ralf B.

2014-01-01

421

Insect-damaged fossil leaves record food web response to ancient climate change and extinction.  

PubMed

Plants and herbivorous insects have dominated terrestrial ecosystems for over 300 million years. Uniquely in the fossil record, foliage with well-preserved insect damage offers abundant and diverse information both about producers and about ecological and sometimes taxonomic groups of consumers. These data are ideally suited to investigate food web response to environmental perturbations, and they represent an invaluable deep-time complement to neoecological studies of global change. Correlations between feeding diversity and temperature, between herbivory and leaf traits that are modulated by climate, and between insect diversity and plant diversity can all be investigated in deep time. To illustrate, I emphasize recent work on the time interval from the latest Cretaceous through the middle Eocene (67-47 million years ago (Ma)), including two significant events that affected life: the end-Cretaceous mass extinction (65.5 Ma) and its ensuing recovery; and globally warming temperatures across the Paleocene-Eocene boundary (55.8 Ma). Climatic effects predicted from neoecology generally hold true in these deep-time settings. Rising temperature is associated with increased herbivory in multiple studies, a result with major predictive importance for current global warming. Diverse floras are usually associated with diverse insect damage; however, recovery from the end-Cretaceous extinction reveals uncorrelated plant and insect diversity as food webs rebuilt chaotically from a drastically simplified state. Calibration studies from living forests are needed to improve interpretation of the fossil data. PMID:18331425

Wilf, P

2008-01-01

422

Donor-Control of Scavenging Food Webs at the Land-Ocean Interface  

PubMed Central

Food webs near the interface of adjacent ecosystems are potentially subsidised by the flux of organic matter across system boundaries. Such subsidies, including carrion of marine provenance, are predicted to be instrumental on open-coast sandy shores where in situ productivity is low and boundaries are long and highly permeable to imports from the sea. We tested the effect of carrion supply on the structure of consumer dynamics in a beach-dune system using broad-scale, repeated additions of carcasses at the strandline of an exposed beach in eastern Australia. Carrion inputs increased the abundance of large invertebrate scavengers (ghost crabs, Ocypode spp.), a numerical response most strongly expressed by the largest size-class in the population, and likely due to aggregative behaviour in the short term. Consumption of carrion at the beach-dune interface was rapid and efficient, driven overwhelmingly by facultative avian scavengers. This guild of vertebrate scavengers comprises several species of birds of prey (sea eagles, kites), crows and gulls, which reacted strongly to concentrations of fish carrion, creating hotspots of intense scavenging activity along the shoreline. Detection of carrion effects at several trophic levels suggests that feeding links arising from carcasses shape the architecture and dynamics of food webs at the land-ocean interface. PMID:23826379

Schlacher, Thomas A.; Strydom, Simone; Connolly, Rod M.; Schoeman, David

2013-01-01

423

Inter-annual variations of planktonic food webs in the northern Adriatic Sea.  

PubMed

The temporal dynamics of microphytoplankton, microzooplankton and mesozooplankton were monitored over 37 months in the Adriatic Sea in order to identify alterations in the plankton structures, which can lead to, or enhance the production of macro-aggregates, that affected the entire northern basin in summers 2000 and 2002, and to assess any negative effects of mucilage on plankton temporal patterns. Samples were collected monthly, from June 1999 to July 2002, on three transects at 9 stations across the northern and central Adriatic Sea. Besides the high year-to-year variations in abundances and taxonomical composition, plankton communities only showed a clear seasonal succession during 2001, when since April a grazing food web developed and was able to control large sized phytoplankton increase. In spring-summer 2000 and 2002 consumer abundances remained quite low and the dominant mesozooplankton summer species (Penilia avirostris) did not reach its usual summer maximum. The lack of an efficient top control was more evident on the northernmost transect, where generally grazing food web prevails over the microbial one. A large part of the microphytoplankton blooms, although not particularly intense, was exported to the bottom in the particulate phase, where it was processed by bacteria, enhancing the production of refractory dissolved material. PMID:16257435

Fonda Umani, Serena; Milani, Luisella; Borme, Diego; de Olazabal, Alessandra; Parlato, Stefania; Precali, Robert; Kraus, Romina; Luci?, Davor; Njire, Jakica; Totti, Cecilia; Romagnoli, Tiziana; Pompei, Marinella; Cangini, Monica

2005-12-15

424

Interactions of multiple predators with different foraging modes in an aquatic food web.  

PubMed

Top predators can have different foraging modes that may alter their interactions and effects on food webs. Interactions between predators may be non-additive resulting from facilitation or interference, whereas their combined effects on a shared prey may result in emergent effects that are risk enhanced or risk reduced. To test the importance of multiple predators with different foraging modes, we examined the interaction between a cruising predator (largemouth bass, Micropterus salmoides) and an ambush predator (muskellunge, Esox masquinongy) foraging on a shared prey (bluegill sunfish, Lepomis macrochirus) with strong anti-predator defense behaviors. Additive and substitution designs were used to compare individual to combined predator treatments in experimental ponds. The multiple predator interaction facilitated growth of the cruising predator in the combined predator treatments, whereas predator species had substitutable effects on the growth of the ambush predator. The combined predator treatments created an emergent effect on the prey; however, the direction was dependent on the experimental design. The additive design found a risk-reducing effect, whereas the substitution design found a risk-enhancing effect for prey fish. Indirect effects from the predators weakly extended to lower trophic levels (i.e., zooplankton community). Our results highlight the need to consider differences in foraging mode of top predators, interactions between predators, and emergent effects on prey to understand food webs. PMID:19777265

Carey, Michael P; Wahl, David H

2010-02-01

425

Antarctic Krill 454 Pyrosequencing Reveals Chaperone and Stress Transcriptome  

PubMed Central

Background The Antarctic krill Euphausia superba is a keystone species in the Antarctic food chain. Not only is it a significant grazer of phytoplankton, but it is also a major food item for charismatic megafauna such as whales and seals and an important Southern Ocean fisheries crop. Ecological data suggest that this species is being affected by climate change and this will have considerable consequences for the balance of the Southern Ocean ecosystem. Hence, understanding how this organism functions is a priority area and will provide fundamental data for life history studies, energy budget calculations and food web models. Methodology/Principal Findings The assembly of the 454 transcriptome of E. superba resulted in 22,177 contigs with an average size of 492bp (ranging between 137 and 8515bp). In depth analysis of the data revealed an extensive catalogue of the cellular chaperone systems and the major antioxidant proteins. Full length sequences were characterised for the chaperones HSP70, HSP90 and the super-oxide dismutase antioxidants, with the discovery of potentially novel duplications of these genes. The sequence data contained 41,470 microsatellites and 17,776 Single Nucleotide Polymorphisms (SNPs/INDELS), providing a resource for population and also gene function studies. Conclusions This paper details the first 454 generated data for a pelagic Antarctic species or any pelagic crustacean globally. The classical “stress proteins”, such as HSP70, HSP90, ferritin and GST were all highly expressed. These genes were shown to be over expressed in the transcriptomes of Antarctic notothenioid fish and hypothesized as adaptations to living in the cold, with the associated problems of decreased protein folding efficiency and increased vulnerability to damage by reactive oxygen species. Hence, these data will provide a major resource for future physiological work on krill, but in particular a suite of “stress” genes for studies understanding marine ectotherms' capacities to cope with environmental change. PMID:21253607

Clark, Melody S.; Thorne, Michael A. S.; Toullec, Jean-Yves; Meng, Yan; Guan, Le Luo; Peck, Lloyd S.; Moore, Stephen

2011-01-01

426

Food web flows through a sub-arctic deep-sea benthic community  

NASA Astrophysics Data System (ADS)

The benthic food web of the deep Faroe-Shetland Channel (FSC) was modelled by using the linear inverse modelling methodology. The reconstruction of carbon pathways by inverse analysis was based on benthic oxygen uptake rates, biomass data and transfer of labile carbon through the food web as revealed by a pulse-chase experiment. Carbon deposition was estimated at 2.2 mmol C m -2 d -1. Approximately 69% of the deposited carbon was respired by the benthic community with bacteria being responsible for 70% of the total respiration. The major fraction of the labile detritus flux was recycled within the microbial loop leaving merely 2% of the deposited labile phytodetritus available for metazoan consumption. Bacteria assimilated carbon at high efficiency (0.55) but only 24% of bacterial production was grazed by metazoans; the remaining returned to the dissolved organic matter pool due to viral lysis. Refractory detritus was the basal food resource for nematodes covering ?99% of their carbon requirements. On the contrary, macrofauna seemed to obtain the major part of their metabolic needs from bacteria (49% of macrofaunal consumption). Labile detritus transfer was well-constrained, based on the data from the pulse-chase experiment, but appeared to be of limited importance to the diet of the examined benthic organisms (<1% and 5% of carbon requirements of nematodes and macrofauna respectively). Predation on nematodes was generally low with the exception of sub-surface deposit-feeding polychaetes that obtained 35% of their energy requirements from nematode ingestion. Carnivorous polychaetes also covered 35% of their carbon demand through predation although the preferred prey, in this case, was other macrofaunal animals rather than nematodes. Bacteria and detritus contributed 53% and 12% to the total carbon ingestion of carnivorous polychaetes suggesting a high degree of omnivory among higher consumers in the FSC benthic food web. Overall, this study provided a unique insight into the functioning of a deep-sea benthic community and demonstrated how conventional data can be exploited further when combined with state-of-the-art modelling approaches.

Gontikaki, E.; van Oevelen, D.; Soetaert, K.; Witte, U.

2011-11-01

427

Climate-driven warming during spring destabilises a Daphnia population: a mechanistic food web approach.  

PubMed

Temperature-driven changes in interactions between populations are crucial to the estimation of the impact of global warming on aquatic food webs. We analysed inter-annual variability in two data sets from Bautzen reservoir, Germany. In a long-term data set (1981-1999) we examined the pelagic phenology of Daphnia galeata, a keystone species, the invertebrate predator Leptodora kindtii, phytoplankton and Secchi depth in relation to water temperature and the North Atlantic Oscillation index. In a short-term data set (1995-1998) we examined food web relations, particularly the consumption of D. galeata by young-of-the-year (YOY) percids and L. kindtii and rates of population change of D. galeata (abundance, recruitment pattern and non-consumptive mortality). The start of the clear-water stage (CWS) was correlated with winter temperatures. It started 5.8 days earlier per degree warming after warm winters (mean January-March temperature>or=2.5 degrees C) compared to cold winters (mean temperature<2.5 degrees C). However, the end of the CWS remained relatively constant. Predation by L. kindtii and YOY percids on D. galeata started distinctly earlier, i.e. by 13.0 and 6.5 days per degree warming, respectively, in years when the average May temperature was high (>or=14 degrees C) compared to years when it was low (<14 degrees C). Significant reductions of Daphnia abundance in midsummer occurred only in years in which the mean May temperature exceeded 14 degrees C. This temperature regime resulted in a match of over-exploitation of food resources by Daphnia during the CWS and strong predation by YOY percids and L. kindtii. Consumptive mortality increased at higher rates with a rise in temperature than net recruitment, resulting in lower Daphnia densities at the end of the CWS. Our data suggest that even low warming by 1.7 degrees C during a short, but critical seasonal period, resulting in the coincidence of two or more factors adversely affecting a keystone species, such as Daphnia, may induce changes in whole lake food webs and thus alter entire ecosystems. PMID:17120058

Wagner, Annekatrin; Benndorf, Jürgen

2007-03-01

428

Exploring the effects of multiple management objectives and exotic species on great lakes food webs and contaminant dynamics  

NASA Astrophysics Data System (ADS)

A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter ( Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will decrease by nearly 20% if Bythotrephes successfully establishes itself in the lake. The model suggests that this decrease will result from lowered transfer efficiencies within the food web and increased flux of contaminants to the hypolimnion. The model also indicates that phosphorus management will have little effect on contaminant concentrations in salmonines. The modeling exercise helped identify weaknesses in the data base (e.g., incomplete information on contaminant loadings and on the biomass, production, and ecological efficiencies of dominant organisms) that should be corrected in order to make reliable management decisions.

Fontaine, Thomas D.; Stewart, Donald J.

1992-03-01

429

Bioaccumulation of per- and polyfluorinated alkyl substances (PFAS) in selected species from the Barents Sea food web.  

PubMed

The present study reports concentrations and biomagnification potential of per- and polyfluorinated alkyl substances (PFAS) in species from the Barents Sea food web. The examined species included sea ice amphipod (Gammarus wilkitzkii), polar cod (Boreogadus saida), black guillemot (Cepphus grylle) and glaucous gull (Larus hyperboreus). These were analyzed for PFAS, polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs) and polybrominated diphenyl ethers (PBDEs). Perfluorooctane sulfonate (PFOS) was the predominant of the detected PFAS. Trophic levels and food web transfer of PFAS were determined using stable nitrogen isotopes (delta(15)N). No correlation was found between PFOS concentrations and trophic level within species. However, a non-linear relationship was established when the entire food web was analyzed. Biomagnification factors displayed values >1 for perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), PFOS and SigmaPFAS(7). Multivariate analyses showed that the degree of trophic transfer of PFAS is similar to that of PCB, DDT and PBDE, despite their accumulation through different pathways. PMID:17258363

Haukås, Marianne; Berger, Urs; Hop, Haakon; Gulliksen, Bjørn; Gabrielsen, Geir W

2007-07-01

430

Networks within networks: floods, droughts, and the assembly of algal-based food webs in a Mediterranean river  

NASA Astrophysics Data System (ADS)

Riverine biota live within several networks. Organisms are embedded in food webs, whose structure and dynamics respond to environmental changes down river drainages. In sunlit rivers, food webs are fueled by attached algae. Primary producer biomass in the Eel River of Northwestern California, as in many sunlit, temperate rivers worldwide, is dominated by the macroalga Cladophora, which grows as a hierarchical, branched network. Cladophora proliferations vastly amplify the ecological surface area and the diversity microhabitats available to microbes. Environmental conditions (light, substrate age or stability, flow, redox gradients) change in partially predictable ways along both Cladophora fronds and river drainage networks, from the frond tips (or headwaters) to their base (or river mouth). We are interested in the ecological and biogeochemical consequences, at the catchment scale, of cross-scale interactions of microbial food webs on Cladophora with macro-organismal food webs, as these change down river drainages. We are beginning to explore how seasonal, hydrologic and macro-consumer control over the production and fate of Cladophora and its epiphytes could mediate ecosystem linkages of the river, its watershed, and nearshore marine ecosystems. Of the four interacting networks we consider, the web of microbial interactions is the most poorly known, and possibly the least hierarchical due to the prevalence of metabolic processing chains (waste products of some members become resources for others) and mutualisms.