Abstract

  Ciliated protists are important components of marine and freshwater ecosystems. As such, their usefulness as indicators of aquatic ecosystem health has been recognized. Two major technical approaches have been employed: (1) community assessment, and (2) toxicological tests. Community assessment of an aquatic ecosystem must at least include comparisons to either baseline data on the ecosystem under study or to 'pristine' ecosystems, since abundance, diversity, and biomass of ciliates are correlated with ecosystem trophic status. Common sampling approaches include sampling of populations and colonization rate determination. The first method may involve nets, bottles, pumps, or integrating samplers. Samples are either counted live or fixed. The choice of fixative may influence estimates of abundance, diversity, and biomass. Colonization rates are determined using polyurethane foam units (PFU's), microscope slides, coverslips, plastic films or petri plates. Live counts are routine with this approach, but undoubtedly give less precise estimates of diversity. Toxicological tests have been devised using a number of indicators of ecosystem health, including respiration rates, growth rates, and chemotactic responses.

Keywords: ciliates, water quality, techniques, community structure, bioassays