The Use of Sessile Ciliates Collected in Plastic Petri Dishes for Rapid Assessment Of Water Pollution

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Abstract
SYNOPSIS. Species of sessile Stentor, Vorticella and colonial peritrichs were collected in boxtype plastic petri dishes. Thru a hole in the wall of the dish, various concentrations of mercuric chloride, a standard bactericidal agent, were introduced. Following a 3‐hour exposure to the toxicant, the death of the sessile ciliates followed a set pattern with a clearcut toxicity threshold of 0.1–0.5 parts per million with an LD 50 of about 0.25 ppm. Furthermore, the sessile ciliates were not dislodged when the natural pond water in the dish was poured out and replaced with water from other sources. Various responses were elicited by 4‐hour exposure to 4 changes of environment. By this procedure, the protozoan community was subjected to new sets of conditions. Such a technic could serve as a method of detecting and assessing water pollution.