You are here:
TOP DOWN CONTROL OF THE MICROBIAL LOOP IN ESTUARINE PHYTOPLANKTON
Citation:
Sipura, J., R. A. Snyder, AND E M. Lores. TOP DOWN CONTROL OF THE MICROBIAL LOOP IN ESTUARINE PHYTOPLANKTON. Presented at An Estuarine Odyssey, St. Pete Beach, FL, 4-8 Nov., 2001.
Description:
Top Down Control of the Microbial Loop in Estuarine Plankton (Abstract). To be presented at the 16th Biennial Conference of the Estuarine Research Foundation, ERF 2001: An Estuarine Odyssey, 4-8 November 2001, St. Pete Beach, FL. 1 p. (ERL,GB R846).
We examined the effects of copepod grazing on estuarine microbial plankton, including bacteria, cyanobacteria, heterotrophic nanoglagellates, microzooplankton, and phytoplankton to elucidate any cascade effects. Six 24L containers were filled with 202 ?m-filtered water from Bayou Texas, Pensacola Bay, Northwest Florida. Copepods were added to three of the cubitainers; all six were incubated in a shaker (150 RPM at 28? C under a 12 hour light - dark cycle (3220 lux). As expected, the copepods significantly decreased both microzooplankton and large phytoplankton populations, and blooms of ciliates and diatoms were apparent in copepod removal treatments. Effects were qualitative (species composition changes) as well as quantitative. Coupling between the diatom bloom and heterotrophic bacterial production was not found. Bacterial numbers, activity and community structure responded to copepod grazing of phytoplankton more than to growth of the phytoplankton itself. Previous reports of a linkage between phytoplankton production and bacterial production may thus be indirect, sustained by zooplankton feeding on planktonic production, rather than "leaky" phytoplankton being a significant source of DOM. Copepod effects on microbial plankton structure and function may thus be more complex than simple linear cascades might predict.