ABSTRACT
CONTENTS Introduction and Background ................................................................................................................ 261
Brief Review of Molecular Biomarkers....................................................................................... 262 Indicators of Hypoxia in Crustacea ............................................................................................. 264
Materials and Methods .......................................................................................................................... 264 Exposure Methods........................................................................................................................ 264 Cloning and Macroarrays of Blue Crab Genes ........................................................................... 265 Subtractive Hybridization for Identification of Hypoxia-Responsive Genes in Blue Crabs
and Grass Shrimp............................................................................................................ 265 Western Blots ............................................................................................................................... 265 Statistical Analyses....................................................................................................................... 266
Results .................................................................................................................................................... 266 Laboratory Survival under Hypoxic Conditions.......................................................................... 266 Changes in Gene and Protein Expression in Blue Crabs in Response to Hypoxia ................... 266 Effects of Hypoxia on Grass Shrimp........................................................................................... 269
Discussion .............................................................................................................................................. 271 Scaling Molecular Biomarker Responses to Population Responses........................................... 272
Conclusions ............................................................................................................................................ 273 Acknowledgments.................................................................................................................................. 273 References .............................................................................................................................................. 274
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.
