Grazing Processes and the Structure and Persistence of Thin Biological Layers

Gifford, Dian J.; Donaghay, Percy L.

Grazing Processes and the Structure and Persistence of Thin Biological Layers

1998

Gifford, Dian J. | Donaghay, Percy L.

My long-term goal is to understand the functional roles of microzooplankton (20-200 microns) in the sea, with emphasis on their contribution to grazing. It has been argued that on a timescale of days the instantaneous grazing rate of zooplankton in toto is greater than the instantaneous rates of vertical and horizontal mixing by at least an order of magnitude, and is the same order of magnitude as the instantaneous rate of phytoplankton cell division. Hence, grazing is a critically important term in the dynamics of phytoplankton loss (Banse 1992). Because microzooplankton are the major grazers in pelagic food webs under most circumstances, their grazing activities exert an important impact on phytoplankton losses in the sea. My specific interests lie in (1) studying their processes of feeding and reproduction at the level of the individual organisms and the community and (2) understanding their function as prey for higher order consumers. The objectives of the current research are two-fold: (1) to measure the impact of grazing by microzooplankton on thin biological layers of phytoplankton and (2) to collect fine-scale (10-25 cm resolution) vertical profiles of nanoplankton (2-20 microns) and microplankton (20-200 microns) in the water column. Data on the vertical distribution and abundance of organisms is used to fully interpret the grazing experiments.

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