THE CHARACTERISTICS AND TRANSPARENT EXOPOLYMER PARTICLE (TEP) CONTENTOF MARINE SNOW FORMED FROM THECATE DINOFLAGELLATES

Abundant marine snow containing diatoms and detritus, but dominated by large, bioluminescent thecate dinoflagellates and their temporary veg etative cysts, especially several species of the genus Gonyaulax, was observed at six stations in the Santa Barbara Channel, California, in 1989 and 1994. These aggregates were unusually cohesive and mucus rich , and contained 2-4 times more mass, particulate organic carbon (POC), particulate organic nitrogen (PON) and chlorophyll a per unit aggrega te volume than more common types of marine snow formed from diatoms, f ecal matter, larvacean houses or miscellaneous detritus. However, the relationship between aggregate size and the concentration of TEP (tran sparent exopolymer particles which form the mucus matrix of most marin e snow) was similar to that of other types of aggregates, suggesting t hat much of the copious gel-like material within dinoflagellate aggreg ates was not TEP. While this is the first report of abundant thecate d inoflagellates occurring within large, rapidly sinking marine aggregat es, the data do not support the conclusion that mass aggregation and s ubsequent sedimentation of blooms is part of the life history adaptati ons of thecate dinoflagellates, as it is for some diatoms. The high ab undance of free-living dinoflagellate cells and temporary cysts, and t he similar proportion of dinoflagellates relative to other algal and c hemical components in both aggregates and the surrounding seawater, in dicate that the dinoflagellates were not differentially aggregating. E ven so, passive accumulation of dinoflagellates in marine snow through aggregation processes may result in more rapid transport of dinoflage llate-generated material to the deep ocean, alter the nature of sinkin g particulate matter following dinoflagellate blooms, and increase the nutritional value of marine snow as a food source for zooplankton and fish.