Protozoan grazing of freshwater biofilms.

Publisher Summary This chapter reviews the corresponding information on protozoa in biofilms, such as their grazing rates, evidence of nutrient remineralization, and their susceptibility to mesoinvertebrate grazing. Protozoan participation in the formation and maintenance of freshwater biofilms has received little attention even though it has been estimated that 99% of microbial activity is associated with surfaces. The behavior of protozoan differs from planktons in the biofilm because of the different protozoan community structure in biofilms. Protozoans exhibit a variety of mechanisms to capture their prey, and this has led to a considerable diversification of protozoan morphologies. However, for simplicity sake they can be divided into amoebae, flagellates, and ciliates. In addition, the close proximity of microbial components could lead to increased levels of cell–cell signaling and increased interaction with pathogenic bacteria. Only a handful of studies have attempted to quantify the grazing impact of these biofilm-associated protozoa but a picture is now starting to develop, though it is far from complete.