engleski

The role of ciliate size structure in controlling bacterial and heterotrophic nanoflgellate abundances in the middle Adriatic Sea

Nonloricate ciliates (NLC) were divided into four size categories: NLC I < 20 um ; NLC II 20-40 um ; NLC III 40-80 um ; and NLC IV > 80 um. HNF were the most important bacterial grazers, particularly during the warmer part of the year. However, the strength of top-down control of bacteria was highly dependent on ciliates size structure. The smallest ciliates size category (NLC I) preyed upon both, bacteria and HNF. Therefore, NLC I limited the growth of HNF indirectly as they compete for bacteria and by direct grazing on HNF. During the spring peak, NLC II represented about 80% of total NLC number. Moreover, very high average density of NLC II was established throughout summer, suggesting that HNF were the most important prey for NLC II. NLC II as an important HNF consumers decreased the HNF abundance as well as their grazing impact on bacteria, which in turn increased the bacterial abundance. The effect of NLC III and NLC IV on prey-predator relationship between bacteria and HNF was less important.

Bacteria; heterotrophic nanoflagellates; ciliates

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