U.S. Environmental Protection Agency
EPA Science Advisory Board
Background Information

Document NameLinkage between microzooplankton grazing and phytoplankton growth in a Gulf of Mexico estuary
Document AuthorMurrell, M.C.
Stanley, R.S.
Lores, E.M.
DiDonato, G.T.
Flemer, D.A.
Short DescriptionEstuaries 25: 19-29
CategorySubgroup 1: Characterization of the Cause(s) of Hypoxia
Publication Year2002

Abstract: Microzooplankton dilution grazing experiments were conducted with water collected from Pensacola Bay, Florida (USA) on 12 dates at 2 sites. Statistically significant grazing rates were observed in 22 of 24 experiments. Grazing rates in Upper Bay and Lower Bay were similar averaging 0.54 and 0.51 d(-1), respectively. Phytoplankton growth rates were also similar at the two sites, averaging 1.02 and 1.00 d(-1) at Upper Bay and Lower Bay, respectively. Phytoplankton growth rates usually exceeded grazing rates by about a factor of two, though microzooplankton grazing represented a significant mortality for phytoplankton. The literature suggests a linkage between phytoplankton growth and microzooplankton grazing that spans a wide variety of aquatic environments. While individual growth and grazing rates were variable, growth frequently exceeded grazing by about two-fold. This implies that the role of microzooplankton is similar across a wide variety of aquatic systems.