The taxonomy and seasonal dynamics of heterotrophic flagellates in Southampton Water, U.K.

Tong, Susan Mary (1994) The taxonomy and seasonal dynamics of heterotrophic flagellates in Southampton Water, U.K. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The diversity of heterotrophic nanoflagellates and other protists was examined at various sites around Southampton Water from October 1991 to June 1994. A total of 122 species are described using light and electron microscopy, including 14 new species. The taxonomy, morphological variation and other aspects of poorly known taxa are discussed in detail.

The abundance of heterotrophic flagellates, autotrophic flagellates and bacteria at the N.W. Netley station was determined at approximately fortnightly intervals between March 1993 and June 1994, together with taxonomic analysis of the flagellate populations. The major taxa of heterotrophic flagellates were the chrysomonads, choanoflagellates, bicosoecids, bodonids and dinoflagellates. It was found that although the abundance of these taxa fluctuated because of seasonal changes in the overall abundance of heterotrophic flagellates, they accounted for similar proportions of the population throughout the year. The majority of heterotrophic flagellates were found to be small (mainly 2.5-5μm) and bacterivorous. Larger nanoflagellates (mostly 10-20μm) formed about 12% of the total population, but accounted for 75% of the biomass. It is concluded that heterotrophic flagellates have an equal grazing impact on the bacterial and nanoplankton populations in Southampton Water, and that the trophic role of larger non-bacterivorous flagellates has been greatly underestimated.

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