The characteristics and transparent exopolymer particle (TEP) content of marine snow formed from thecate dinoflagellates

Abundant marine snow containing diatoms and detritus, but dominated by large, bioluminescent thecate dinoflagellates and their temporary vegetative 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 aggregate volume than more common types of marine snow formed from diatoms, fecal matter, larvacean houses or miscellaneous detritus. However, the relationship between aggregate size and the concentration of TEP (transparent exopolymer particles which form the mucus matrix of most marine snow) was similar to that of other types of aggregates, suggesting that much of the copious gel-like material within dinoflagellate aggregates was not TEP. While this is the first report of abundant thecate dinoflagellates occurring within large, rapidly sinking marine aggregates, the data do not support the conclusion that mass aggregation and subsequent sedimentation of blooms is part of the life history adaptations of thecate dinoflagellates, as it is for some diatoms. The high abundance of free-living dinoflagellate cells and temporary cysts, and the similar proportion of dinoflagellates relative to other algal and chemical components in both aggregates and the surrounding seawater, indicate that the dinoflagellates were not differentially aggregating. Even so, passive accumulation of dinoflagellates in marine snow through aggregation processes may result in more rapid transport of dinoflagellate-generated material to the deep ocean, alter the nature of sinking particulate matter following dinoflagellate blooms, and increase the nutritional value of marine snow as a food source for zooplankton and fish.