Quantity and quality: the role of terrestrial subsidies in food web pathways and ecosystem metabolism in Horonai Stream

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Conference Proceeding

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High-quality subsidies may be low magnitude fluxes, but have disproportionate effects in food webs (e.g., terrestrial invertebrate prey for fish). Alternately, low-quality subsidies may be large fluxes but have weak food web effects (e.g., leaf litter and DOC). We asked, what is the relative role of different terrestrial subsidies (leaf litter vs. terrestrial invertebrates) for organic matter flow through the food web of forested Horonai Stream (Hokkaido, Japan)? The annual flux of terrestrial invertebrate biomass into this stream is equal to only 5% of the flux of leaf litter biomass, yet terrestrial invertebrates contribute 44% to the energy budget of the fish assemblage. In contrast, measures of open-water primary production and respiration suggest that leaf litter inputs drive metabolism of the ecosystem. We compiled data on algal, invertebrate and fish production and trophic connections between these organisms to determine what proportion of animal production is derived from terrestrial inputs directly via consumption and indirectly via food web linkages. Comparisons like this will shed light on how subsidies of different quality and to different trophic levels compare in aquatic food webs.

Publication Title

American Society of Limnology and Oceanography and the North American Benthological Society Joint Meeting 2010