The role of biomarkers in the health assessment of aquatic ecosystems

Abstract

Much progress has been made in abating the impacts on aquatic ecosystems of industrial wastewaters, intensive agriculture, and large urban centres. Nowadays the short term consequence of stress from such sources is less frequently the death and destruction of fish populations or entire communities of organisms. Large scale fish kills are now less common. Scientific attention has shifted to the effects on ecosystems of long term exposures to sublethal stressors. Although use of the term 'ecosystem health' is a topic of debate, the metaphor can usefully reflect a state of well being or absence of impaired survival, growth, reproduction, and recruitment problems in an ecosystem's key organisms. The present article explores the use of the physiological and biochemical responses of organisms to stressors, the so-called 'biomarkers, ' to assess and study the sublethal effects of chemical stressors in fish. Fish were chosen as the organism of example because they are key components of practically all aquatic ecosystems. Most biomarkers can be used as an early warning that fish have been exposed to putative stressors, and can often be used to help identify the stressor(s). Biomarkers, however, tell us little about the eventual ecological outcome of such exposures. Some biomarkers are mechanistically linked to toxic modes of action, and can thus be classed as 'biomarkers of effect' at the level of the individual organism. None, however, have been fully validated and calibrated as predictive indicators of adverse ecological effects at either the population or community levels. Biomarkers are valueable as part of a broader strategy for monitoring the effects of stressors on aquatic ecosystems.

Heat-shock protein 90 alpha (HSP90α) modulates signaling pathways towards tolerance of oxidative stress and enhanced survival of hepatocytes of Mugil cephalus

“…Iwama et al (1998) and Vijayan et al (1998) have also demonstrated induction of HSPs in response to aquatic contaminants. Studies that reported the induction of various HSP families in fish following exposure to various environmental stressors demonstrated a protective role of HSPs, also suggesting the use of the HSP response as an indicator of stress status in fish (Sherry 2003;.…”

Helminths and lipid peroxidation in Astyanax aeneus (Pisces: Characidae) from a river in the humid subtropics of southeastern Mexico

“…In turn, the presence of parasites induces higher energy and oxygen consumption in the host fish (Voutilainen et al 2008), which increases oxidative metabolism (ROS) as well as damage at the cellular membrane level. An increase or decrease in ROS levels can lead to major changes (Sherry 2003) which compromise the function of the immune system through increased susceptibility to pathogens such as parasitic worms (Romano 1999). The results of the present study suggest that mean abundances of Clinostomum complanatum, Contracaecum sp., and Polymorphus sp.…”

“…One such case is that of oxidative stress, which occurs through disruption of the balance between reactive oxygen species (ROS) and antioxidant defenses. Oxidative stress damages biomolecules such as lipids and induces various physi-ological and biochemical changes which cause cell impairment and death (Sherry 2003, Van der Oost et al 2003. ROS convert fatty acids into fatty acid radicals that are able to oxidize adjacent molecules.…”

Physiological Adaptations of Stressed Fish to Polluted Environments: Role of Heat Shock Proteins

“…Basu et al (2002), in a previous review, have demonstrated that HSPs play a key role in various aspects of fish physiology, including development, aging, stress physiology, endocrinology, immunology, environmental physiology, adaptation, and stress tolerance. Researchers have reported the induction of various HSP families in fish following exposure to various environmental stressors and have demonstrated that these HSPs provide a protective role (Currie et al1999;Sherry 2003). Other studies have affirmed the use of the HSP response as an indicator of stress status in fish (Samali and Orrenius 1998;.…”

“…Fish are physiologically similar to mammals and typically experience long-term exposure in habitats that range from the pristine to ones that are highly polluted, making them an ideal organism for assessing the protective role of HSPs (Currie et al1999;Sherry 2003). HSP expression has been examined in many species (Feder and Hofmann 1999), including fish , and the majority of such studies have been performed in the laboratory.…”