Hypoxia, or lack of oxygen, in bottom waters is a well known environmental problem. New research at the University of Gothenburg, Sweden adds to the list of ill effects: hypoxia leads to increased levels of manganese, which damages the immune response in marine animals.

Water eutrophication and the resulting hypoxia is an ever-current issue, not least in connection with summer algal blooms. A more recently acknowledged problem is that hypoxia, which occurs when algae is broken down, increases the release of toxic metals from bottom sediments. Researchers at the University of Gothenburg have found that one of these metals, manganese, may damage the immune response in marine animals.

Essential - and toxic
While low doses of manganese are essential to life in both humans and animals, it has been known for a long time that higher doses can be detrimental to health. Manganese is abundant in soft ocean bottoms, but since it is normally bound to the sediments it usually does not cause any ill effects. However, hypoxia releases the manganese from the sediments, making it a threat to the health of marine species.

Researcher Carolina Oweson, Department of Marine Ecology at the University of Gothenburg, has studied how manganese in Swedish coastal waters affects the Norway lobster, the blue mussel and the common sea star. Her conclusion is that while manganese does not seem to have a permanent effect, it does threaten the survival of several species during periods of hypoxia.

'While the effects of manganese on the immune response in the studied animals vary, they are all affected in some way. The Norway lobster and mussels are affected the most, for example through an increased susceptibility to infections', says Oweson.

Similar to humans
Marine animals are of great interest to researchers since their immune systems are similar to those of humans in many ways. The species in Oweson's study also make up an important part of our marine ecosystem. In addition, new findings indicating that hypoxia is becoming increasingly common in coastal areas around the world make Oweson's study even more relevant.

(Science Daily, 11/08/2009)