scholarly journals Comparisons of Late Ordovician ecosystem dynamics before and after the Richmondian invasion reveal consequences of invasive species in benthic marine paleocommunities

Paleobiology ◽  
2020 ◽  
Vol 46 (3) ◽  
pp. 320-336
Author(s):  
Hannah L. Kempf ◽  
Ian O. Castro ◽  
Ashley A. Dineen ◽  
Carrie L. Tyler ◽  
Peter D. Roopnarine
Keyword(s):  
Food Webs ◽  
Late Ordovician ◽  
Ecosystem Dynamics ◽  
Trophic Levels ◽  
Museum Collections ◽  
Variable Response ◽  
Food Web Structure ◽  
Online Data ◽  
Data Repositories ◽  
Before And After

AbstractA thorough understanding of how communities respond to extreme changes, such as biotic invasions, is essential to manage ecosystems today. Here we constructed fossil food webs to identify changes in Late Ordovician (Katian) shallow-marine paleocommunity structure and functioning before and after the Richmondian invasion, a well-documented ancient invasion. Food webs were compared using descriptive metrics and cascading extinction on graphs models. Richness at intermediate trophic levels was underrepresented when using only data from the Paleobiology Database relative to museum collections, resulting in a spurious decrease in modeled paleocommunity stability. Therefore, museum collections and field sampling may provide more reliable sources of data for the reconstruction of trophic organization in comparison to online data repositories. The invasion resulted in several changes in ecosystem dynamics. Despite topological similarities between pre- and postinvasion food webs, species loss occurred corresponding to a minor decrease in functional groups. Invaders occupied all of the preinvasion functional guilds, with the exception of four incumbent guilds that were lost and one new guild, corroborating the notion that invaders replace incumbents and fill preexisting niche space. Overall, models exhibited strong resistance to secondary extinction, although the postinvasion community had a lower threshold of collapse and more variable response to perturbation. We interpret these changes in dynamics as a decrease in stability, despite similarities in overall structure. Changes in food web structure and functioning resulting from the invasion suggest that conservation efforts may need to focus on preserving functional diversity if more diverse ecosystems are not inherently more stable.

USING FOOD WEBS TO EXAMINE ECOSYSTEM DYNAMICS DURING BIOTIC INVASIONS IN LATE ORDOVICIAN SHALLOW MARINE COMMUNITIES

2016 ◽  
Author(s):  
Hannah L. Kempf ◽  
◽  
Ashley A. Dineen ◽  
Peter D. Roopnarine ◽  
Carrie L. Tyler
Keyword(s):  
Food Webs ◽  
Late Ordovician ◽  
Ecosystem Dynamics ◽  
Shallow Marine ◽  
Marine Communities

scholarly journals Mesoscale variations in the assemblage structure and trophodynamics of mesozooplankton communities of the Adriatic basin (Mediterranean Sea)

2021 ◽  
Author(s):  
Emanuela Fanelli ◽  
Samuele Menicucci ◽  
Sara Malavolti ◽  
Andrea De Felice ◽  
Iole Leonori
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Mediterranean Sea ◽  
Environmental Variables ◽  
Complex Structure ◽  
Assemblage Structure ◽  
Trophic Levels ◽  
Ecosystem Functions ◽  
Food Web Structure ◽  
Adriatic Basin

Abstract. Zooplankton are critical to the functioning of ocean food webs because of their utter abundance and vital ecosystem roles. Zooplankton communities are highly diverse and thus perform a variety of ecosystem functions, thus changes in their community or food web structure may provide evidence of ecosystem alteration. Assemblage structure and trophodynamics of mesozooplantkon communities were examined across the Adriatic basin, the northernmost and most productive basin of the Mediterranean Sea. Samples were collected in June–July 2019 along coast-offshore transects covering the whole western Adriatic side, consistently environmental variables were also recorded. Results showed a clear separation between samples from the northern-central Adriatic and the southern ones, with a further segregation, although less clear, of inshore vs. off-shore stations, the latter mostly dominated in the central and southern stations by gelatinous plankton. Such patterns were mainly driven by chlorophyll-a concentration (as a proxy of primary production) for northern-central stations, i.e. closer to the Po river input, and by temperature and salinity, for southern ones, with the DistLM model explaining 46 % of total variance. The analysis of stable isotopes of nitrogen and carbon allowed to identify a complex food web characterized by 3 trophic levels from herbivores to carnivores, passing through the mixed feeding behavior of omnivores, shifting from phytoplankton/detritus ingestion to microzooplankton. Trophic structure also spatially varied according to sub-area, with the northern-central sub-areas differing from each other and from the southern stations. Our results highlighted the importance of environmental variables as drivers of zooplanktonic communities and the complex structure of their food webs. Disentangling and considering such complexity is crucial to generate realistic predictions on the functioning of aquatic ecosystems, especially in high productive and, at the same time, overexploited area such as the Adriatic Sea.

Decrease in diatom dominance at lower Si:N ratios alters plankton food webs

2020 ◽  
Vol 42 (4) ◽  
pp. 411-424
Author(s):  
Kriste Makareviciute-Fichtner ◽  
Birte Matthiessen ◽  
Heike K Lotze ◽  
Ulrich Sommer
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Phytoplankton Community ◽  
Plankton Community ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Web Structure ◽  
Copepod Grazing ◽  
Important Food Source

Abstract Many coastal oceans experience not only increased loads of nutrients but also changes in the stoichiometry of nutrient supply. Excess supply of nitrogen and stable or decreased supply of silicon lower silicon to nitrogen (Si:N) ratios, which may decrease diatom proportion in phytoplankton. To examine how Si:N ratios affect plankton community composition and food web structure, we performed a mesocosm experiment where we manipulated Si:N ratios and copepod abundance in a Baltic Sea plankton community. In high Si:N treatments, diatoms dominated. Some of them were likely spared from grazing unexpectedly resulting in higher diatom biomass under high copepod grazing. With declining Si:N ratios, dinoflagellates became more abundant under low and picoplankton under high copepod grazing. This altered plankton food web structure: under high Si:N ratios, edible diatoms were directly accessible food for copepods, while under low Si:N ratios, microzooplankton and phago-mixotrophs (mixoplankton) were a more important food source for mesograzers. The response of copepods to changes in the phytoplankton community was complex and copepod density-dependent. We suggest that declining Si:N ratios favor microzoo- and mixoplankton leading to increased complexity of planktonic food webs. Consequences on higher trophic levels will, however, likely be moderated by edibility, nutritional value or toxicity of dominant phytoplankton species.

scholarly journals The rise of the three-spined stickleback – eco-evolutionary consequences of a mesopredator release

2020 ◽  
Author(s):  
Britas Klemens Eriksson ◽  
Casey Yanos ◽  
Sarah Bourlat ◽  
Serena Donadi ◽  
Michael C. Fontaine ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Stomach Content ◽  
Ecological Effects ◽  
Trophic Levels ◽  
Predatory Fish ◽  
Series Data ◽  
Food Web Structure ◽  
Benthic Production ◽  
Invertebrate Herbivores

AbstractDeclines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human-induced rapid evolution may in turn affect ecological dynamics. In the central Baltic Sea, abundances of the mesopredatory fish, the three-spined stickleback (Gasterosteus aculeatus), have increased dramatically during the past decades. Time-series data covering 22 years show that this increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We studied the interaction between evolutionary and ecological effects of this mesopredator take-over, by surveying the armour plate morphology of stickleback and the structure of the associated food web. First, we investigated the distribution of different stickleback phenotypes depending on predator abundances and benthic production; and described the stomach content of the stickleback phenotypes using metabarcoding. Second, we explored differences in the relation between different trophic levels and benthic production, between bays where the relative abundance of fish was dominated by stickleback or not; and compared this to previous cage-experiments to support causality of detected correlations. We found two distinct lateral armour plate phenotypes of stickleback, incompletely and completely plated. The proportion of incompletely plated individuals increased with increasing benthic production and decreasing abundances of adult perch. Stomach content analyses showed that the completely plated individuals had a stronger preference for invertebrate herbivores (amphipods) than the incompletely plated ones. In addition, predator dominance interacted with ecosystem production to determine food web structure and the propagation of a trophic cascade: with increasing production, biomass accumulated on the first (macroalgae) and third (stickleback) trophic levels in stickleback-dominated bays, but on the second trophic level (invertebrate herbivores) in perch-dominated bays. Since armour plates are defence structures favoured by natural selection in the presence of fish predators, the phenotype distribution suggest that a novel low-predation regime favours sticklebacks with less armour. Our results indicate that an interaction between evolutionary and ecological effects of the stickleback take-over has the potential to affect food web dynamics.

scholarly journals Understanding the structure and functioning of polar pelagic ecosystems to predict the impacts of change

2016 ◽  
Vol 283 (1844) ◽  
pp. 20161646 ◽  
Author(s):  
E. J. Murphy ◽  
R. D. Cavanagh ◽  
K. F. Drinkwater ◽  
S. M. Grant ◽  
J. J. Heymans ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Energy Flow ◽  
Life Histories ◽  
Trophic Levels ◽  
Individual Species ◽  
Polar Regions ◽  
Ecosystem Structure ◽  
Food Web Structure ◽  
Pelagic Ecosystems

The determinants of the structure, functioning and resilience of pelagic ecosystems across most of the polar regions are not well known. Improved understanding is essential for assessing the value of biodiversity and predicting the effects of change (including in biodiversity) on these ecosystems and the services they maintain. Here we focus on the trophic interactions that underpin ecosystem structure, developing comparative analyses of how polar pelagic food webs vary in relation to the environment. We highlight that there is not a singular, generic Arctic or Antarctic pelagic food web, and, although there are characteristic pathways of energy flow dominated by a small number of species, alternative routes are important for maintaining energy transfer and resilience. These more complex routes cannot, however, provide the same rate of energy flow to highest trophic-level species. Food-web structure may be similar in different regions, but the individual species that dominate mid-trophic levels vary across polar regions. The characteristics (traits) of these species are also different and these differences influence a range of food-web processes. Low functional redundancy at key trophic levels makes these ecosystems particularly sensitive to change. To develop models for projecting responses of polar ecosystems to future environmental change, we propose a conceptual framework that links the life histories of pelagic species and the structure of polar food webs.

scholarly journals Food web persistence in fragmented landscapes

2017 ◽  
Vol 284 (1859) ◽  
pp. 20170350 ◽  
Author(s):  
Jinbao Liao ◽  
Daniel Bearup ◽  
Bernd Blasius
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Position ◽  
Biodiversity Loss ◽  
Habitat Destruction ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Spatially Extended ◽  
Biodiversity Maintenance ◽  
Patch Connectivity

Habitat destruction, characterized by patch loss and fragmentation, is a key driver of biodiversity loss. There has been some progress in the theory of spatial food webs; however, to date, practically nothing is known about how patch configurational fragmentation influences multi-trophic food web dynamics. We develop a spatially extended patch-dynamic model for different food webs by linking patch connectivity with trophic-dependent dispersal (i.e. higher trophic levels displaying longer-range dispersal). Using this model, we find that species display different sensitivities to patch loss and fragmentation, depending on their trophic position and the overall food web structure. Relative to other food webs, omnivory structure significantly increases system robustness to habitat destruction, as feeding on different trophic levels increases the omnivore's persistence. Additionally, in food webs with a dispersal–competition trade-off between species, intermediate levels of habitat destruction can enhance biodiversity by creating refuges for the weaker competitor. This demonstrates that maximizing patch connectivity is not always effective for biodiversity maintenance, as in food webs containing indirect competition, doing so may lead to further species loss.

scholarly journals Phenotypic variation explains food web structural patterns

2017 ◽  
Vol 114 (42) ◽  
pp. 11187-11192 ◽  
Author(s):  
Jean P. Gibert ◽  
John P. DeLong
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Level ◽  
Phenotypic Variation ◽  
Structural Features ◽  
Trophic Levels ◽  
Intake Rate ◽  
Food Web Structure ◽  
Total Food Intake ◽  
Variation Sets

Food webs (i.e., networks of species and their feeding interactions) share multiple structural features across ecosystems. The factors explaining such similarities are still debated, and the role played by most organismal traits and their intraspecific variation is unknown. Here, we assess how variation in traits controlling predator–prey interactions (e.g., body size) affects food web structure. We show that larger phenotypic variation increases connectivity among predators and their prey as well as total food intake rate. For predators able to eat only a few species (i.e., specialists), low phenotypic variation maximizes intake rates, while the opposite is true for consumers with broader diets (i.e., generalists). We also show that variation sets predator trophic level by determining interaction strengths with prey at different trophic levels. Merging these results, we make two general predictions about the structure of food webs: (i) trophic level should increase with predator connectivity, and (ii) interaction strengths should decrease with prey trophic level. We confirm these predictions empirically using a global dataset of well-resolved food webs. Our results provide understanding of the processes structuring food webs that include functional traits and their naturally occurring variation.

scholarly journals Climate change alters the structure of arctic marine food webs due to poleward shifts of boreal generalists

2015 ◽  
Vol 282 (1814) ◽  
pp. 20151546 ◽  
Author(s):  
Susanne Kortsch ◽  
Raul Primicerio ◽  
Maria Fossheim ◽  
Andrey V. Dolgov ◽  
Michaela Aschan
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Barents Sea ◽  
Ecosystem Dynamics ◽  
The Arctic ◽  
Food Web Structure ◽  
Marine Food Web ◽  
Web Structure ◽  
The Barents Sea ◽  
Marine Food

Climate-driven poleward shifts, leading to changes in species composition and relative abundances, have been recently documented in the Arctic. Among the fastest moving species are boreal generalist fish which are expected to affect arctic marine food web structure and ecosystem functioning substantially. Here, we address structural changes at the food web level induced by poleward shifts via topological network analysis of highly resolved boreal and arctic food webs of the Barents Sea. We detected considerable differences in structural properties and link configuration between the boreal and the arctic food webs, the latter being more modular and less connected. We found that a main characteristic of the boreal fish moving poleward into the arctic region of the Barents Sea is high generalism, a property that increases connectance and reduces modularity in the arctic marine food web. Our results reveal that habitats form natural boundaries for food web modules, and that generalists play an important functional role in coupling pelagic and benthic modules. We posit that these habitat couplers have the potential to promote the transfer of energy and matter between habitats, but also the spread of pertubations, thereby changing arctic marine food web structure considerably with implications for ecosystem dynamics and functioning.

scholarly journals Multiple species drive flexible lake food webs with warming

2018 ◽  
Author(s):  
Timothy J. Bartley ◽  
Tyler D. Tunney ◽  
Nigel P. Lester ◽  
Brian J. Shuter ◽  
Robert H. Hanner ◽  
...  
Keyword(s):  
Climate Change ◽  
Temperature Gradient ◽  
Food Webs ◽  
Lake Trout ◽  
Trophic Levels ◽  
Forage Fish ◽  
Food Web Structure ◽  
Web Structure ◽  
Nearshore Habitat ◽  
Multiple Species

AbstractClimate change is rewiring the food webs that determine the fate of diverse ecosystems. Mobile generalist consumers are responding to climate change by rapidly shifting their behaviour and foraging, driving food webs to flex. Although these responsive generalists form a key stabilizing module in food web structure, the extent to which they are present throughout whole food webs is largely unknown. Here, we show that multiple species comprising key trophic roles drive flexible lake food webs with warming. By examining lakes that span a 7°C air temperature gradient, we found significant reductions in nearshore derived carbon and nearshore habitat use with increased temperature in three of four fish species. We also found evidence that the response of lake trout to increased temperatures may reduce their biomass and cascade to release their preferred prey, the pelagic forage fish cisco. Our results suggest that climate warming will shift lake food webs toward increased reliance on offshore habitats and resources. We argue that species across trophic levels broadly couple lake macrohabitats, suggesting that potentially stabilizing responsive consumers are present throughout food webs. However, climate change appears to limit their ability to responsively forage, critically undermining a repeated stabilizing mechanism in food webs.

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