The Contribution of Ciliated Protozoa to Zooplankton Biomass in an Acidic, Subtropical Lake

<p> Ciliated protozoa accounted for up to 50% of the mean daily zooplankton biomass in McCloud Lake, a small (5 ha), oligotrophic, acidic (pH 4.7) lake in north&hyphen;central Florida. Food resources (algae and bacterioplankton) were limiting for crustacean and rotifer zooplankton during much of the year. Myxotrophic ciliates were a dominant component of the planktonic food web. <em> Stentor niger </em> , an uncommon species in the plankton of lakes, dominated the ciliate assemblage and usually comprised &gt; 90% of total ciliate biomass. <em> Stentor niger </em> always contained high densities of photosynthetic zoochlorellae and contributed an estimated 30% to the total autotrophic biomass.</p>