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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Food webs 2
The importance of pelagic subsidies and zooplankton abundance to chironomids: a totally tubular nutrient enrichment experiment
G.A. Burkart1, L. Lyndon Valicenti2, G.M. Gettel3, C. Luecke1, T. Stephenson1, and K. Hill1. 1Ecology Center, Utah State University, Logan, UT, USA, 84322, 2University of California Santa Barbara, 3Cornell University
Most nutrient amendment studies in lakes have not only disregarded the importance of benthic production but also the importance of links between benthic and pelagic food webs (Vadeboncouer et al. 2002). We used in situ mesocosm (500-L transparent, closed-bottom tubes) experiments to observe whether nutrient amendments (6µmols N + 0.375µmols P), zooplankton abundance (low and high) and pelagic subsidies (sedimenting particulate matter) affect growth of individual chironomids in an oligotrophic arctic lake at the Toolik Lake LTER. Within individual mesocosms, chironomids were placed in small tubes which were open or closed to pelagic subsidies. Fertilized mesocosms with low zooplankton abundance had the highest pelagic chl-a concentrations; whereas, unfertilized mesocosms with high zooplankton biomass had the lowest. Biomass of chironomids was higher in treatments with high zooplankton biomass. Furthermore, chironomids that received pelagic subsidies in both the fertilized, high zooplankton treatment and the unfertilized low zooplankton treatment had higher biomass than chironomids that did not receive pelagic subsidies. Effects of nutrient enrichment on chironomid growth varied depending on at least two pelagic variables: zooplankton abundance and availability of pelagic subsidies. These data suggest that understanding benthic-pelagic links is important for a more complete understanding of nutrient amendment studies in lakes.
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