Physiological responses: Their measurement and use as environmental biomarkers in ecotoxicology

This paper briefly reviews the utility of physiological measurements as biomarkers of pollutant exposure and biological effect, and then gives a step by step description of methodologies used to measure physiological parameters in mostly fish and invertebrates, but also higher vertebrates where appropriate. The effects of pollutants on respiratory, cardiovascular, osmoregulatory, and neuro-endocrine processes are relatively well described in laboratory experiments and some of these responses (particularly ventilation, heart rate, and also body ion fluxes) have been evaluated as biomonitors or potential biomarkers in the field. Physiological assays are especially useful for monitoring fluctuating or complex exposures, or acting as 'early warning' systems for acute events. Some biomarkers rely on a change in physiological response, and a prerequisite of such assay must be to establish the normal resting response in defined environmental conditions (e.g., temperature, pH, photoperiod, etc.). Biomarkers that rely on variability of response, rather than absolute values, may not require this 'laboratory calibration.' Methods are described for on line cardiovascular monitoring with shore crabs, field applications of closed respirometry and ion flux measurements with fish; and a range of blood parameters for animals including haemoglobin, haematocrit, cell counts, glucose, triglycerides, and protein from blood and organ perfusates. Each method includes a short critic of the approach.