Choanoflagellates of the central California waters: Abundance and distribution

Choanoflagellates have been enumerated at between 7 and 10 stations on a transect > 300 km in length off the central California coast on 7 cruises from August 1989 to June 1990. Abundances and biomass of choanoflagellates, estimated from epifluorescence counts, ranged from 2900 to 3900,000 cells per liter and from 0.01 to 38.44 .mu.gC per liter. Minimum abundances were associated with offshore stations during March and maximum abundances with the coastal stations during the same cruise, coincident witha Chaetoceros bloom. Choanoflagellate biomass comprised approxiamtely 12% of the total heterotrophic biomass was significantly correlated (r = 0.54, P <0.001) with the heterotrophic flagellates. An average of 17% of the choanoflagellates had autotrophic picoplankton in their vacuoles. Choanoflagellates were calculated to clear between <0.1 and 180% of the water column per day.