Molecular and Organismal Indicators of Chronic and Intermittent Hypoxia In Marine Crustacea

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Book Chapter

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Human population growth in coastal regions and their watersheds, accompanied by agricultural, industrial, and urban development, has led to an unprecedented acceleration of contaminant and nutrient inputs into estuaries. Both the nutrients that fuel primary productivity and the near-coastal hydrodynamics that generate water column stratification contribute to the formation of hypoxic zones. Of the total estuarine area in the Gulf of Mexico that was surveyed in 1994-1995, oxygen depletion (anoxia or hypoxia) events occurred in 32 of 38 estuaries (U.S. EPA, 1999), whereas an expansive area of seasonal hypoxia/anoxia develops yearly on the Louisiana continental shelf (Turner and Rabalais, 1994). Eutrophication and ensuing bottom water hypoxia and anoxia are regarded as major factors responsible for declines in habitat quality and harvestable resources in estuarine ecosystems (Justic et al., 1993; Turner and Rabalais, 1994; Paerl et al., 1998). In addition, increased nutrient loading amplifies cyclic dissolved oxygen (DO) patterns that often develop in shallow waters during the summer months, leading to conditions of intermittent hypoxia. Estuarine organisms are therefore not only at risk of being subjected to chronic hypoxic conditions, but also face increases in duration and frequency of hypoxic-normoxic cycles (Ringwood and Keppler, 2002). However, because we lack fundamental information regarding sublethal effects of chronic or intermittent hypoxia on estuarine organisms, indicators of adaptive responses to these conditions are largely unknown.

Publication Title

Estuarine Indicators

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