Who Is Where in Marine Food Webs? A Trait-Based Analysis of Network Positions

Networks of trophic interactions provide a lot of information on the functioning of marine ecosystems. Beyond feeding habits, three additional traits (mobility, size, and habitat) of various organisms can complement this trophic view. The combination of traits and food web positions are studied here on a large food web database. The aim is a better description and understanding of ecological roles of organisms and the identification of the most important keystone species. This may contribute to develop better ecological indicators (e.g., keystoneness) and help in the interpretation of food web models. We use food web data from the Ecopath with Ecosim (EwE) database for 92 aquatic ecosystems. We quantify the network position of organisms by 18 topological indices (measuring centrality, hierarchy, and redundancy) and consider their three, categorical traits (e.g., for mobility: sessile, drifter, limited mobility, and mobile). Relationships are revealed by multivariate analysis. We found that topological indices belong to six different categories and some of them nicely separate various trait categories. For example, benthic organisms are richly connected and mobile organisms occupy higher food web positions.

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Feeding habits and trophic level of the smooth hammerhead shark, Sphyrna zygaena (Carcharhiniformes: Sphyrnidae), off Ecuador

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315418000474 ◽

2018 ◽

Vol 99 (3) ◽

pp. 673-680 ◽

Cited By ~ 2

Author(s):

Colombo Estupiñán-Montaño ◽

Luis Cedeño-Figueroa ◽

José F. Estupiñán-Ortiz ◽

Felipe Galván-Magaña ◽

Alejandro Sandoval-Londoño ◽

...

Keyword(s):

Trophic Level ◽

Feeding Habits ◽

Trophic Niche ◽

Commercial Fishing ◽

Dosidicus Gigas ◽

Apex Predators ◽

Marine Food Webs ◽

Fishing Vessels ◽

Marine Food ◽

Index Of Relative Importance

As apex predators, sharks are known to play an important role in marine food webs. Detailed information on their diet and trophic level is however needed to make clear inferences about their role in the ecosystem. A total of 335 stomachs of smooth hammerhead sharks, Sphyrna zygaena, were obtained from commercial fishing vessels operating in the Ecuadorian Pacific between January and December 2004. A total of 53 prey items were found in the stomachs. According to the Index of Relative Importance (%IRI), cephalopods were the main prey (Dosidicus gigas, Sthenoteuthis oualaniensis, Ancistrocheirus lesueurii and Lolliguncula [Loliolopsis] diomedeae). Sphyrna zygaena was thus confirmed to be a teutophagous species. The estimated trophic level of S. zygaena was between 4.6 and 5.1 (mean ± SD: 4.7 ± 0.16; males: 4.7; females: 4.8). Levin's index (BA) was low (overall: 0.07; males: 0.08; females: 0.09), indicating a narrow trophic niche. We found that sharks <150 cm in total length consumed prey of coastal origin, whereas sharks ≥150 cm foraged in oceanic waters and near the continental shelf. The analyses indicate that S. zygaena is a specialized predator consuming mainly squids.

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Architecture of Marine Food Webs: to be or not be a ‘small-world’

10.1101/274415 ◽

2018 ◽

Author(s):

Tomás Ignacio Marina ◽

Leonardo A. Saravia ◽

Georgina Cordone ◽

Vanesa Salinas ◽

Santiago R. Doyle ◽

...

Keyword(s):

Food Web ◽

Food Webs ◽

Path Length ◽

Small World ◽

Marine Ecosystems ◽

Characteristic Path Length ◽

Structural Pattern ◽

Marine Food Webs ◽

Marine Habitats ◽

Marine Food

AbstractThe search for general properties in network structure has been a central issue for food web studies in recent years. One such property is the small-world topology that combines a high clustering and a small distance between nodes of the network. This property may increase food web resilience but make them more sensitive to the extinction of connected species. Food web theory has been developed principally from freshwater and terrestrial ecosystems, largely omitting marine habitats. If theory needs to be modified to accommodate observations from marine ecosystems, based on major differences in several topological characteristics is still on debate. Here we investigated if the small-world topology is a common structural pattern in marine food webs. We developed a novel, simple and statistically rigorous method to examine the largest set of complex marine food webs to date. More than half of the analyzed marine networks exhibited a similar or lower characteristic path length than the random expectation, whereas 39% of the webs presented a significantly higher clustering than its random counterpart. Our method proved that 5 out of 28 networks fulfilled both features of the small-world topology: short path length and high clustering. This work represents the first rigorous analysis of the small-world topology and its associated features in high-quality marine networks. We conclude that such topology is a structural pattern that is not maximized in marine food webs; thus it is probably not an effective model to study robustness, stability and feasibility of marine ecosystems.

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Unraveling the intricate dynamics of planktonic Arctic marine food webs. A sensitivity analysis of a well-documented food web model

Progress In Oceanography ◽

10.1016/j.pocean.2018.01.003 ◽

2018 ◽

Vol 160 ◽

pp. 167-185 ◽

Cited By ~ 6

Author(s):

Blanche Saint-Béat ◽

Frédéric Maps ◽

Marcel Babin

Keyword(s):

Sensitivity Analysis ◽

Food Web ◽

Food Webs ◽

Marine Food Webs ◽

Marine Food ◽

Food Web Model

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Are Antarctic and sub-Antarctic marine food webs different?

10.1101/2021.04.12.439560 ◽

2021 ◽

Author(s):

Iara DIamela Rodriguez ◽

Tomas Ignacio Marina ◽

Leonardo Ariel Saravia

Keyword(s):

Food Web ◽

Food Webs ◽

Potter Cove ◽

Marine Food Webs ◽

Beagle Channel ◽

West Antarctic ◽

Antarctic Marine ◽

Marine Food ◽

West Antarctic Peninsula ◽

Mean Trophic Level

Aim: Food web structure plays an important role in determining ecosystem stability to perturbations. High latitude marine ecosystems are being affected by environmental stressors and ecological shifts. In the West Antarctic Peninsula these transformations are driven by climate change, and in the sub-Antarctic region by anthropogenic activities. Understanding the differences between these areas is necessary to monitor the changes that are expected to occur in the upcoming decades. Here, we compared the structure and stability of Antarctic and sub-Antarctic marine food webs. Location: Antarctic (Potter Cove, 25 de Mayo/King George Island, West Antarctic Peninsula) and sub-Antarctic (Beagle Channel, Tierra del Fuego, South America) regions. Time period: 1965 - 2019. Major taxa studied: from phytoplankton to fish. Methods: We compiled species trophic (predator-prey) interactions and calculated complexity (number of species and interactions, connectance), structure (mean trophic level, omnivory, degree distribution, modularity, species roles and traits) and stability (QSS) metrics. To be able to make statistical comparisons, we used a randomization algorithm (Strona Curveball) maintaining the number of prey and predators for each species and calculated metrics for each simulation. Results: The Beagle Channel food web presented higher values for complexity metrics (number of species and interactions), structure (mean trophic level, omnivory, modularity) but lower stability (QSS). Potter Cove fitted the exponential degree distribution, while Beagle Channel the power-law with exponential cutoff model. Both food webs presented the same connectance value (0.05), similar distribution of species in top, intermediate and top positions and topological roles, with only one network connector each. Main conclusions: Our results showed that Beagle Channel food web is more complex, but less stable and sensitive to the loss of its most connected species. While the Potter Cove food web presented less complexity and greater stability to perturbations.

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Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health

10.31230/osf.io/x2jft ◽

2018 ◽

Author(s):

Maddison Carbery ◽

Wayne O'Connor ◽

Palanisami Thavamani

Keyword(s):

Food Web ◽

Food Webs ◽

Human Health ◽

Trophic Transfer ◽

The Real ◽

Marine Food Web ◽

Marine Food Webs ◽

Bioaccumulation Factors ◽

Mixed Contaminants ◽

Marine Food

Plastic litter has become one of the most serious threats to the marine environment. Over 690 marine species have been impacted by plastic debris with small plastic particles being observed in the digestive tract of organisms from different trophic levels. The physical and chemical properties of microplastics facilitate the sorption of contaminants to the particle surface, serving as a vector of contaminants to organisms following ingestion. Bioaccumulation factors for higher trophic organisms and impacts on wider marine food webs remain unknown. The main objectives of this review were to discuss the factors influencing microplastic ingestion; describe the biological impacts of associated chemical contaminants; highlight evidence for the trophic transfer of microplastics and contaminants within marine food webs and outline the future research priorities to address potential human health concerns. Controlled laboratory studies looking at the effects of microplastics and contaminants on model organisms employ nominal concentrations and consequently have little relevance to the real environment. Few studies have attempted to track the fate of microplastics and mixed contaminants through a complex marine food web using environmentally relevant concentrations to identify the real level of risk. To our knowledge, there has been no attempt to understand the transfer of microplastics and associated contaminants from seafood to humans and the implications for human health. Research is needed to determine bioaccumulation factors for popular seafood items in order to identify the potential impacts on human health.

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