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MICROZOOPLANKTON GRAZING AND NUTRIENT BIOASSAY STUDIES IN PENSACOLA BAY: THE ROLE OF TOP-DOWN AND BOTTOM-UP CONTROLS.
Citation:
Murrell, M C., R S. Stanley, E M. Lores, AND D A. Flemer. MICROZOOPLANKTON GRAZING AND NUTRIENT BIOASSAY STUDIES IN PENSACOLA BAY: THE ROLE OF TOP-DOWN AND BOTTOM-UP CONTROLS. Presented at Fall 2000 Meeting of the Gulf Estuarine Research Society, Nashville, TN, 13-15 November 2000.
Description:
To better understand the causes and consequences of nutrient over-enrichment (eutrophication) in Gulf of Mexico estuaries, we examined roles of grazing and nutrient limitation in Pensacola Bay. One consequence of eutrophication is altering the function of plankton food webs; the basis of the marine food chain. Such an alteraton can have cascading effects on an ecosystem and result in multiple negative impacts including loss of habitat and loss of human resouce use. Microzooplankton grazing and nutrient limitation studies were conducted at 2 sites on 5 dates from December 1998 to September 1999. The grazing experiments examined the potential of top-down control on primary production, while the nutrient limitation experiments examined bottom-up controls. The grazing experiments measured changes in net phytoplankton growth in treatments with varying numbers of microzooplankton predators. Preliminary results suggest that microzooplankton often exerted a significant control (46% to over 100% of production) on phytoplankton growth. The nutrient limitation experiments measured the growth of phytoplankton in treatments with varying nutrient additions. Those results suggest that that phosphorus may limit primary production at certain times of the year. Combining these results allows a means to evaluate the relative importance of top-down and bottom-up controls on primary production.