engleski

The role of ciliates within microbial food web in the eutrophicated part of Kaštela Bay (middle Adriatic Sea)

Interactions among phytoplankton, bacterioplankton, heterotrophic nanoflagellates (HNF), ciliated protozoa and copepod nauplii were studied in the eutrophicated part of Kaštela Bay from May 1998 till November 1999. Special emphasis was dedicated to relationships between size categories of nonloricate ciliates (NLC) and other microbial food web components. Biomasses of phytoplankton and bacteria were primarily influenced by abiotic parameters. Temperature controlled variation in HNF biomass indirectly through the changes in biomass of bacteria and smaller phytoplankton fraction. Besides HNF, bacterial biomass was affected by the NLC <103 &#956; m3 (Cell Length <20 &#956; m). Small NLC size category (<104 &#956; m3, CL <40 &#956; m) could limit the growth of HNF as they compete for bacteria and also by direct grazing. Nonloricate ciliates >104 &#956; m3 (CL >40 &micro ; ; m) were in strong mutual correlation and they seemed to be controlling the microphytoplankton fraction. During the colder part of the year, HNF abundance was regulated by ciliate grazing. The high impact of ciliates in summer 1998 could be influenced by changed taxonomic composition of phytoplankton community, as well as higher eutrophication level of the investigated area. Predation by copepod nauplii on ciliates and carbon transfer to higher trophic level appears to be of relative importance only in period of their highest abundance. This paper points out the dominant relationships within microbial food web and suggests that significant amount of bacterial production, phytoplankton and HNF biomass could be transferred to higher trophic level through the microbial food web.

ciliated protozoa; biotic factors; abiotic factors; microbial food web; Adriatic Sea

nije evidentirano