Impact of fertilization and stocking on trophic interactions and growth of juvenile sockeye salmon (Oncorhynchus nerka)

2002 ◽  
Vol 59 (8) ◽  
pp. 1361-1373 ◽  
Author(s):  
Asit Mazumder ◽  
Jim A Edmundson
Keyword(s):  
Food Web ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Web Structure ◽  
Mean Size ◽  
Average Size ◽  
The Impact

Using 16 years of data on nutrients, plankton, and sockeye fry and smolts from Packers Lake, Alaska, we test the impact of nutrients and fry stocking on the growth and productivity of juvenile sockeye salmon (Oncorhynchus nerka). To enhance sockeye production, this lake was fertilized (1983–1996) and stocked annually (1987–1996) with sockeye fry. Before fertilization, the density of sockeye fry was low (<0.20 fry·m–2), the size and biomass of Daphnia were low, and sockeye smolts were relatively small. Before stocking, all trophic levels responded positively to fertilization. The biomass and mean size of Daphnia increased significantly. The average size of age-1 and age-2 smolts increased three- to four-fold. Fry stocking produced dramatic declines in both biomass and mean length of Daphnia and in size of smolts. When large-sized (>1 mm) Daphnia were significantly reduced in density under heavy predation by sockeye fry, the growth of juvenile sockeye declined, even under continued fertilization. We show that fry density and associated food web structure are major determinants of juvenile sockeye responses to fertilization and stocking. This study probably provides the first long-term experimental results linking limnological and nutrient – food web concepts to trophodynamics and productivity of juvenile sockeye salmon.

scholarly journals Cladocera paleocommunity to disentangle the impact of anthropogenic and climatic stressors on a deep subalpine lake ecosystem (Lake Iseo, Italy)

2021 ◽  
Author(s):  
Barbara Leoni ◽  
Martina Patelli ◽  
Veronica Nava ◽  
Monica Tolotti
Keyword(s):  
Species Composition ◽  
Food Web ◽  
Anthropogenic Pressure ◽  
Food Web Structure ◽  
Subfossil Cladocera ◽  
Web Structure ◽  
Pelagic Food Web ◽  
The Impact ◽  
Plankton Communities

AbstractIn big lakes with strong anthropogenic pressure, it is usually difficult to disentangle the impacts of climate variability from those driven by eutrophication. The present work aimed at the reconstruction of change in the species distribution and density of subfossil Cladocera in Lake Iseo (Italy) in relation to climate and anthropogenic pressure. We related subfossil Cladocera species composition and density in an 80-cm sediment core collected in the pelagic zone of Lake Iseo to long-term temperature trends and phosphorus concentration inferred by diatoms frustules. The Cladocera remains detected in Lake Iseo sediment reflected the species composition and density of modern pelagic Cladocera assemblages. Cladocera rapidly respond to environmental change, and that climate change combined with eutrophication can induce changes in community composition and species density. At the beginning of twentieth century, when global warming was not yet so accentuated, the nutrient increase in water resulted as the principal driver in determining the long-term development of plankton communities and pelagic food web structure. Moreover, catchment-related processes may decisively affect both species composition and density of the lake planktonic communities due to the decrease of lake water transparency induced by input of inorganic material from the catchment area to the lake. The paleolimnological investigation, through the combined study of biotic and abiotic factor, allowed clarifying the synergic effects of the most important drivers of change in lake ecosystems, suggesting that climatic factors should be considered with nutrient availability as determinant element in controlling the temporal development of plankton communities and pelagic food web structure.

scholarly journals The impact of intraspecific variation on food web structure

Ecology ◽  
2018 ◽  
Vol 99 (12) ◽  
pp. 2712-2720 ◽  
Author(s):  
Tom Clegg ◽  
Mohammad Ali ◽  
Andrew P. Beckerman
Keyword(s):  
Food Web ◽  
Intraspecific Variation ◽  
Food Web Structure ◽  
Web Structure ◽  
The Impact

scholarly journals Untangling the roles of parasites in food webs with generative network models

2015 ◽  
Author(s):  
Abigail Z. Jacobs ◽  
Jennifer A. Dunne ◽  
Cristopher Moore ◽  
Aaron Clauset
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Statistical Physics ◽  
Network Models ◽  
Food Web Structure ◽  
Free Living ◽  
Web Structure ◽  
Living Species ◽  
Parasitic Interactions ◽  
The Impact

Food webs represent the set of consumer-resource interactions among a set of species that co-occur in a habitat, but most food web studies have omitted parasites and their interactions. Recent studies have provided conflicting evidence on whether including parasites changes food web structure, with some suggesting that parasitic interactions are structurally distinct from those among free-living species while others claim the opposite. Here, we describe a principled method for understanding food web structure that combines an efficient optimization algorithm from statistical physics called parallel tempering with a probabilistic generalization of the empirically well-supported food web niche model. This generative model approach allows us to rigorously estimate the degree to which interactions that involve parasites are statistically distinguishable from interactions among free-living species, whether parasite niches behave similarly to free-living niches, and the degree to which existing hypotheses about food web structure are naturally recovered. We apply this method to the well-studied Flensburg Fjord food web and show that while predation on parasites, concomitant predation of parasites, and parasitic intraguild trophic interactions are largely indistinguishable from free-living predation interactions, parasite-host interactions are different. These results provide a powerful new tool for evaluating the impact of classes of species and interactions on food web structure to shed new light on the roles of parasites in food webs.

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.

An Inverse Model Analysis of Planktonic Food Webs in Experimental Lakes

1994 ◽  
Vol 51 (9) ◽  
pp. 2034-2044 ◽  
Author(s):  
Alain F. Vézina ◽  
Michael L. Pace
Keyword(s):  
Food Web ◽  
Heterotrophic Bacteria ◽  
Grazing Pressure ◽  
Inverse Methods ◽  
Trophic Levels ◽  
Microbial Food Web ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Size Groups ◽  
The Impact

We used inverse methods to reconstruct carbon flows in experimental lakes where the fish community had been purposely altered. These analyses were applied to three years of data from a reference lake and two experimental lakes located in Gogebic County, Michigan. We reconstructed seasonally averaged flows among two size groups of phytoplankton, heterotrophic bacteria, microzooplankton, cladocerans, and copepods. The inverse analysis produced significantly different flow networks for the different lakes that agreed qualitatively with known chemical and biological differences between lakes and with other analyses of the impact of fish manipulations on food web structure and dynamics. The results pointed to alterations in grazing pressure on the phytoplankton that parallel changes in the size and abundance of cladocerans and copepods among lakes. Estimated flows through the microbial food web indicated low bacterial production efficiencies and small carbon transfers from the microbial food web to the larger zooplankton. This study demonstrates the use of inverse methods to identify and compare flow patterns across ecosystems and suggests that microbial flows are relatively insensitive to changes at the upper trophic levels.

scholarly journals Benthic biodiversity and food web structure in the European sector of the Arctic Ocean during spring time

2018 ◽  
Author(s):  
Barbara Oleszczuk ◽  
Katarzyna Grzelak ◽  
Monika Kędra
Keyword(s):  
Sea Ice ◽  
Food Web ◽  
Barents Sea ◽  
Benthic Communities ◽  
Trophic Levels ◽  
The Arctic ◽  
Feeding Guild ◽  
Food Web Structure ◽  
Web Structure ◽  
Ice Conditions

Arctic marine ecosystems are currently facing sea ice decrease. Changes in the sea ice cover will influence the Organic Matter (OM) fluxes to the bottom and thus benthic communities. We aimed to examine meio- and macrobenthic biodiversity and community structure, and food web, with use of stable isotopes of carbon (δ13C) and nitrogen (δ15N), in relation to depth, sea ice type, and bloom stage. Benthic samples were collected in Svalbard area during spring time in 2015 and 2016 along with samples of particulate and sediment OM. Svalbard fjords, Storfjorden, Barents Sea shelf, continental slope, and Nansen Basin were characterized by different environmental settings including various sea ice conditions, bloom stage, sediment OM and particulate OM in bottom water. The highest biodiversity and biomass were found at the shelf and slope stations where intensive bloom was observed and was related to higher concentrations of fresh, high-quality OM. Low benthic infaunal diversity, abundance, and biomass were noted in fjords and deep stations where quality and quantity of OM was markedly lower. Deposit feeders were the only feeding guild sampled in the deep stations while at other stations 3-4 trophic levels were found.

Impacts of macrozoobenthic invasions on a temperate coastal food web

2020 ◽  
Vol 653 ◽  
pp. 19-39
Author(s):  
AS Jung ◽  
HW van der Veer ◽  
CJM Philippart ◽  
AM Waser ◽  
BJ Ens ◽  
...  
Keyword(s):  
Food Web ◽  
Native Species ◽  
Wadden Sea ◽  
Marine Species ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Total Consumption ◽  
Predator Prey ◽  
Carbon Transfer ◽  
The Impact

Invasions of marine species are changing coastal food webs worldwide, impacting on trophic interactions between native species (e.g. predator-prey relationships). Here, the impact of 3 macrozoobenthic invasive species on food web structure and functioning at Balgzand (western Wadden Sea) is quantified by using ecological network analysis (ENA). The bivalves Ensis leei and Magallana gigas were observed for the first time in 1984 and 2001, respectively, and the polychaete Marenzelleria viridis appeared in 1989. Although E. leei and M. viridis reached similar peak biomasses in the 2000s (ca. 1700 and 2000 mg C m-2, respectively), the bivalve consumption was higher (>45% of total consumption) than that of the polychaete (<10%). Biomass and impact of M. gigas remained relatively low. E. leei occupied an ecological niche that was relatively unoccupied, which led to competitive advantage with respect to other suspension feeders. Increasing biomass of E. leei coincided with a 70% increase of trophic carbon transfer from primary to secondary producers and an 80% increase from secondary producers to detritus. Carbon flows from secondary producers to higher trophic levels were reduced by more than 60%. These shifts in trophic transfer were stronger than those observed during the invasion of M. gigas in the NE Wadden Sea. At Balgzand, biomass of M. gigas and M. viridis rapidly declined to low values in the 2010s, implying a temporally limited impact. In the 2010s, E. leei was still responsible for 30% of the total consumption in the 2010s, indicating a longer-term impact.

Spatio-temporal reproducibility of the microbial food web structure associated with the change in temperature: Long-term observations in the Adriatic Sea

2018 ◽  
Vol 161 ◽  
pp. 87-101 ◽  
Author(s):  
Mladen Šolić ◽  
Branka Grbec ◽  
Frano Matić ◽  
Danijela Šantić ◽  
Stefanija Šestanović ◽  
...  
Keyword(s):  
Food Web ◽  
Adriatic Sea ◽  
Microbial Food Web ◽  
Food Web Structure ◽  
Web Structure ◽  
Spatio Temporal
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