Aquatic Sciences Meeting, Albuquerque 2001

CS34 Trophic Dynamics

Date: Friday, February 16, 2001, Time: 9:15:00 AM

Location: Mesilla

Wissel, B, , Louisiana State University, Baton Rouge, USA, bwissel@unix1.sncc.lsu.edu

Boeing, W, J, Louisiana State University, Baton Rouge, USA, wboeing@unix1.sncc.lsu.edu

Ramcharan, C, W, Louisiana State University, Baton Rouge, USA, cramcha@lsu.edu

DOES DISSOLVED ORGANIC CARBON (DOC) SHIFT THE BALANCE BETWEEN FISH AND INVERTEBRATE PREDATORS?

DOC has multiple effects on freshwater lakes, changing the vertical profiles of light, temperature, and oxygen. An increase in DOC concentration should reduce fish predation on zooplankton and invertebrate predators such as Chaoborus should become more important. Since fish prefer larger prey but Chaoborus can only ingest smaller zooplankton, an increase in DOC should cause a shift from small to large zooplankton species. To test this hypothesis, I performed a six-week enclosure experiment on the effects of DOC, Fish, and Chaoborus (2x2x2 factorial). Within a High-DOC and a Low-DOC Lake, I had a Control-, a Fish-, a Chaoborus-, and a Fish+Chaoborus-Treatment. In the Low-DOC Lake, fish eliminated large cladocerans and copepods and small cladocerans and rotifers were dominant, while in the High-DOC Lake, larger cladocerans and copepods were able to maintain higher abundances in treatments including fish. The zooplankton community in Control- and Chaoborus-Treatments consisted of large cladocerans and few small species. Generally, high DOC concentrations supported more and larger species in the presence of fish, probably due to a light and oxygen refugia.

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Aquatic Sciences Meeting, Albuquerque 2001

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