Monitoring stress in warming oceans – a non-lethal approach for the tropical reef fish Amphiprion ocellaris

Climate warming presents new challenges for environmental biomonitoring. There is a need for the development of biomarkers that respond not only to chemical pollution but also to thermal stress events. Current research on biomarkers of cellular stress uses lethal methods, which should be avoided, particularly in sensitive and/or disturbed systems, like coral reefs. In this study, the effects of thermal stress were tested in ocellaris clownfish, <i>Amphiprion ocellaris</i>, in a non-lethal approach, using caudal fin tissue. Fish were exposed to a long-term experiment following two temperature treatments: control (26°C) and current average El Niño temperatures (30°C). Samples were taken at 0, 7, 14, 21 and 28 days for evaluation of stress biomarkers (catalase, glutathione-S-transferase, superoxide dismutase, lipid peroxidation, heat shock protein 70kDa (HSP70) and total ubiquitin). HSP70 showed a rapid increase at 30°C, followed by a temporary depletion, a typical response pattern previously reported for other tissues of several species, indicating it is appropriate for thermal stress biomonitoring. Other biomarkers were generally unresponsive to higher temperature. They should be useful for contamination monitoring, given that they have already been widely used for that purpose and this work showed temperature will not be a confounding variable in their assessment. It is concluded that <i>A. ocellaris</i>, as a site attached fish (to its anemone host) can be a good sentinel species to be monitored in field-conditions along time by using a simple sampling method – fin-clipping, and measuring biomarker levels under stressful conditions.

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