Use of protozoan communities for pollution monitoring.

A gradient of chronic organic pollution was identified in a small river in south-east England. The parasite fauna of the ubiquitous three-spined stickleback (Gasterosteus aculeatus L.) was studied at the extremes of the pollution gradient and trichodinid ciliates identified as a potential bioindicator. A simple technique was developed for the quantification of whole body-burdens of trichodinids on small fish. Three species of trichodinids were identified: Trichodina domerguei, T. tenuidens and Trichodinella epizootica at combined infestation intensities of < 14 to 137522/fish. Preliminary results are reported which may link the increased intensity of trichodinid infestation with increased concentration of sewage treatment works effluent.