MEPS 345:63-73 (2007)  -  doi:10.3354/meps06841

Microzooplankton: major herbivores in an estuarine planktonic food web

J. N. Putland1,2,*, R. L. Iverson1

1Department of Oceanography, Florida State University, Tallahassee, Florida 32306-4320, USA
2Present address: Harbor Branch Oceanographic Institution, 5600 Highway U.S. 1 North, Ford Pierce, Florida 34946, USA

ABSTRACT: Microzooplankton, on average, ingested 10 times more phytoplankton productivity than Acartia tonsa, which dominates the mesozooplankton community in Apalachicola Bay, Florida, USA. Microzooplankton ingested <75 and >75% of phytoplankton productivity during winter and summer, respectively. Ciliates, particularly ciliates <20 µm in size, were abundant in all samples. Phytoplankton was the main (>50%) component of the microzooplankton diet during the summer high productivity period. Because microzooplankton are prey for organisms occupying higher trophic levels, such as copepods, fish larvae, and oysters, we propose that energy and mass flows mainly from phytoplankton through microzooplankton to higher trophic levels in Apalachicola Bay. A reduction in discharge from the Apalachicola River during our study period led to reductions in rates of grazing, ingestion, and productivity of microzooplankton at a particular salinity. Reduced river discharge also increased the areal extent of higher salinity water where ingestion and productivity of microzooplankton were relatively low. Because microzooplankton are key constituents of the estuarine food web in Apalachicola Bay, upstream water diversion that increases the areal extent of higher salinity water in the bay, can be expected to lower microzooplankton productivity and therefore reduce higher trophic level productivity in the bay.

KEY WORDS: River flow · Management · Estuarine · Food web structure · Microzooplankton

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Cite this article as: Putland JN, Iverson RL (2007) Microzooplankton: major herbivores in an estuarine planktonic food web. Mar Ecol Prog Ser 345:63-73

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