Physiological studies clarify how copper pollution and hypoxia affect fish

Two major problems in the oceans are the spreading of hypoxic areas (areas with low oxygen level) and copper pollution. The ocean deoxygenation problem is the subject of an IUCN report, downloadable from https://www.iucn.org/resources/publications, and it has been discussed also in this blog on December 13, 2019 (Deoxygenation of oceans is an increasing problem with effects on sealife). Copper pollution is caused especially because copper is a component of antifouling paints of ship hulls and boats. These paints are used to kill all organisms attaching on boats (discussed in this blog, Environmental Effects of Shipping, January 15, 2020). These two problems interact. Exposure to copper decreases tolerance to low oxygen level in fish. This is possibly due to copper causing thickening of gill epithelium, whereby oxygen transfer across the epithelium is decreased. In contrast, previous hypoxia reduces tha effects of copper on fish. This is probably due to copper effects being reduced after hypoxia-inducible factor (HIF)-dependent pathway is activated.

Several studies on copper-hypoxia interactions on the functions of fish have been published from 2004 onwards (e.g. van Heerden et al. Aquatic Toxicology 69, 271-280, 2004; Fitzgerald et al Aquatic Toxicology 217, 105325, 2019; Zeng et al. Science of the Total Environment 708, 134961, 2020). They indicate how important physiological studies are for understanding, how humans affect the ocean ecosystems.