Tough Lives: Fish in Extreme Environments
The physical environment has a major influence on the ecology and evolution of all living organisms. For fish, the availability of dissolved oxygen is one of the most critical factors in their environment, limiting habitat quality, growth, and survival.
Oxygen scarcity (hypoxia) occurs naturally in systems characterized by low light and low mixing (e.g., heavily vegetated swamps, flooded forests). Unfortunately, environmental degradation also elevates the occurrence of hypoxia, as municipal wastes accelerate the pollution of water bodies and fertilizer runoff adds excess nutrients, stimulating the growth of algae and nuisance plants (eutrophication) at the expense of other organisms. Thus it has become increasingly important to understand the consequences of low-oxygen for fish.
In their studies of dense African swamps, Dr. Lauren Chapman and her research group have discovered how fish respond to extreme hypoxia and they have begun to explore the role of oxygen in the divergence of fish populations and the evolution of biological diversity. By comparing populations that cross oxygen gradients and by rearing fish under different oxygen conditions, the researchers have been able to detect changes in the morphology, physiology, and behaviour of fish in response to low-oxygen stress. They have also uncovered how alternative oxygen environments can contribute to faunal diversification. In addition, in their studies of the Lake Victoria basin, where the introduction of the predatory Nile perch coincided with the mass extinction of hundreds of fish species, they have demonstrated that oxygen-scarce wetlands serve as a suitable safe habitat for endangered fishes.
As a Canada Research Chair, Dr. Chapman continues her study of conservation issues in East Africa, where two decades after the introduction of the Nile perch, some native species that were in retreat - or even thought to be extinct - are re-emerging. The impact of faunal collapse and recovery on resurging species is the focus of her studies. She hopes her work will help inform conservation and management initiatives and provide a deeper understanding of the role of hypoxic swamps in the generation, maintenance, loss, and recovery of aquatic biodiversity.