FY 1979

Microzooplankton in the surface waters of the Strait of Juan de Fuca

Chester, A.J.

NOAA Tech. Rep. ERL 403-PMEL 30, NTIS: PB-297233/AS, 26 pp (1978)

Microzooplankton organisms were enumerated from surface seawater samples obtained at three stations in the Strait of Juan de Fuca during 13 cruises from 1976 to 1977 (tabulated data appear in Appendix). Ciliates were the most abundant group; maximum concentrations exceeded 10,000 liter. The ciliate community was composed almost exclusively of oligotrichs, tintinnids, and the gymnostome species, Mesodinium rubrum. These groups made up an average 60%, 10%, and 30%, respectively, of the total ciliate numbers at each station. Twenty-six tintinnid species and 15 oligotrich species were identified during the 2-year study. The population peaks of most of these organisms coincided with periods of high biological activity during spring and summer. Certain species, however, such as the tintinnid Stenosemella ventricosa, were most common during winter months. The ecological role of oligotrichs and tintinnids as particle grazers is distinguished from that of M. rubrum, a ciliate deriving its nutrition from photosynthetic endosymbionts.