Assessing sources of stress to aquatic ecosystems using integrated biomarkers

Establishing causal relationships between sources of environmental stressor s and aquatic ecosystem health is difficult because of the many biotic and abiotic factors which can influence or modify responses of biological syste ms to stress, the orders of magnitude involved in extrapolation over both s patial and temporal scales, and compensatory mechanisms such as density-dep endent responses that operate in populations. To address the problem of est ablishing causality between stressors and effects on aquatic systems, a dia gnostic approach, based on exposure-response profiles for various anthropog enic activities, was developed to help identify sources of stress responsib le for effects on aquatic systems at ecological significant levels of biolo gical organization (individual, population, community). To generate these e xposure-effects profiles, biomarkers of exposure were plotted against bioin dicators of corresponding effects for several major anthropogenic activitie s including petrochemical, pulp and paper, domestic sewage, mining operatio ns, land-development activities, and agricultural activities. Biomarkers of exposure to environmental stressors varied depending on the type of anthro pogenic activity involved. Bioindicator effects, however, including histopa thological lesions, bioenergetic status, individual growth, reproductive im pairment, and community-level responses, were similar among many of the maj or anthropogenic activities. This approach is valuable to help identify and diagnose sources of stressors in environments impacted by multiple stresso rs. By identifying the types and sources of environmental stressors, aquati c ecosystems can be more effectively protected and managed to maintain acce ptable levels of environmental quality and ecosystem fitness.