Grazing and Windows of Opportunity for Dinoflagellate BloomsEPA Grant Number: R829366
Title: Grazing and Windows of Opportunity for Dinoflagellate Blooms
Investigators: Stoecker, Diane K. , Boicourt, William C. , Roman, Michael R.
Institution: University of Maryland Center for Environmental Science , Horn Point Laboratory
EPA Project Officer: Hiscock, Michael
Project Period: January 1, 2002 through December 31, 2004
Project Amount: $428,184
RFA: Ecology and Oceanography of Harmful Algal Blooms (2001) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water , Ecosystems
Description:Dinoflagellates can cause harmful algal blooms. The fact that high densities of some dinoflagellates appear to be resistant to grazing is probably the reason that grazing pressure has not often been considered in prediction of dinoflagellate blooms. However, in early stages of bloom formation, grazing may prevent blooms.
The objectives are to determine: if "windows of opportunity" occur when and where grazing pressure is low on dinoflagellates; if "windows" are a necessary condition for initiation of blooms; and to define the physical and biological parameters that can create them. The hypotheses are: 1. microzooplankton community grazing is greater than mesozooplankton community grazing on small (< 25 ?m) dinoflagellates; 2. microzooplankton community grazing coefficients (g) are usually higher than growth rates (?) of small dinoflagellates, and prevent net growth; 3. blooms occur when, in addition to environmental conditions being conducive to growth, there is a "window" of reduced grazing pressure in which ? > g. There is no bloom if g > ?; 4. "windows" occur following the spring diatom bloom because microzooplankton that consume dinoflagellates are low in abundance, due to lack of appropriate sized food and top down control by copepods; and 5. "windows" occur after influxes of freshwater that alter boundaries between oligohaline and mesohaline waters. Transition areas that have sufficient nutrients and light, but where densities of microzooplankton grazers are low, support blooms.