Fish Surviving Ocean Dead Zones Face Substantial Reproductive Problems - Royal Society Proceedings

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It is no surprise that a dip in oxygen levels in water can kill fish, as has occurred in the Gulf of Mexico's notorious dead zone. But as new research published online on August 28 in Proceedings of the Royal Society of London, Series B shows, fish from the hypoxic coastal waters of Florida produce fewer eggs and less sperm, which can affect survival of the species.

Previous research by Rudolf Wu of the City University of Hong Kong suggested a potential link between hypoxia and endocrine function. In laboratory experiments, his group showed that reduced oxygen levels disrupted the development of ovaries and testes in adult carp. The group also reported that hypoxia masculinizes lab-bred female zebra fish, but effects on wild fish populations remained unknown.

In the present study, Peter Thomas and his colleagues at the Marine Sciences Institute of the University of Texas Austin looked at the reproductive system of the Atlantic croaker—a species that can tolerate moderate reductions in oxygen levels. Fish from low-oxygen areas of Pensacola Bay had significantly smaller ovaries and testes and produced fewer eggs and less sperm than those from nearby waters with normal oxygen levels. The researchers also observed similar effects in wild croakers exposed to hypoxic conditions in the lab. Further experiments showed that these changes are caused by reductions in the levels of the neurotransmitter serotonin, which controls the synthesis and release of sex hormones.

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http://pubs.acs.org/subscribe/journals/esthag-w/2007/sept/science/rc_hypoxia.html

[orpupilofnature57]

1. Al !!!!!!!!!!! 9/5/08 or bust.