Phytoplankton Blooms: Their Occurrence and Composition Within Virginia's Tidal Tributaries

Sporadic algal bloom development within a IO year monitoring program in Virginia tidal tributaries of Chesapeake Bay is reviewed. These blooms were common events, characteristically producing a color signature to the surface water, typically short lived, occurring mainly from spring into autumn throughout different salinity regions of these rivers. and were produced primarily by dinoflagcilatcs. The abundance threshold levels that would identify bloom status from a non-bloom presence were species specific, varied with the taxon's cell size, and ranged from ca. 10 to \() cells ml • Among the most consistent sporadic bloom producers were the dinoflagcllatcs Akashiwo sanguinea, Cochlodinium polvkrikoides, Heterocapsa rotundata, Hetcrocapsa triquetra, Karlodinium l'eneficum, Prorocentrum minimum, Scrippsiella trochoidea, the cyanobacterium lvficrocystis aeruginosa, and two categories containing several species of often unidentified Gymnodinium spp. and Gyrodinium spp. Additional bloom producers within these tributaries arc also discussed.