ABSTRACT
CONTENTS Introduction ............................................................................................................................................ 316
Background and Need.................................................................................................................. 316 Definition of Macrobenthic Process Indicators ........................................................................... 316 Hypothesis .................................................................................................................................... 318 Objectives ..................................................................................................................................... 318
Methods.................................................................................................................................................. 319 Standard Operating Procedures.................................................................................................... 319 Field Methods............................................................................................................................... 319
Site-Event Characterization ............................................................................................ 319 Water Column Profile ..................................................................................................... 319 Macrofaunal Samples...................................................................................................... 319 Sediment Samples ........................................................................................................... 319
Laboratory Methods ..................................................................................................................... 320 Processing Macrofaunal Samples ................................................................................... 320 Processing Sediment Samples ........................................................................................ 321
Results .................................................................................................................................................... 321 Process-Indicator Development.................................................................................................... 321
Volume Conversions........................................................................................................ 321 Mass Conversions............................................................................................................ 321 Daily Production Estimates ............................................................................................ 321 Aggregation to Macrobenthic Production ...................................................................... 322 Estimating the P:B Ratio ................................................................................................ 322 Standardized Biomass-Size Spectra................................................................................ 322
Case Study — Grand Bay National Estuarine Research Reserve .............................................. 322 Study Design ................................................................................................................... 322 Spatial Patterns in Process Indicators............................................................................. 323 Linking Macrobenthic Process Indicators ...................................................................... 324 Relating Macrobenthic Process Indicators and Ecosystem Function ............................ 324
Discussion .............................................................................................................................................. 325 Conclusions and Recommendations...................................................................................................... 328 Acknowledgments.................................................................................................................................. 328 References .............................................................................................................................................. 329
Healthy estuaries within the Gulf of Mexico of the United States contribute high fisheries production, ample biodiversity, recreational benefits, transportation, and water supply (U.S. EPA, 1999). In response to mounting pressures on national estuarine resources, however, the U.S. Environmental Protection Agency (EPA) Environmental Monitoring and Assessment Program-Estuaries (EMAP-E) was implemented to quantify the status and condition of estuaries (Summers et al., 1991). The objective of the EMAP-E multiyear monitoring program was to assess the ecological condition and biotic integrity of entire coastal regions, or provinces. Macrobenthic organisms provide reliable indicators of biotic integrity; and the benthic index was one of the most useful measures of estuarine condition developed by the U.S. EPA EMAP-E Program. However, there are various disadvantages of existing benthic indices: (1) they represent a static expression of ecological condition; (2) they are not explicitly linked to changes in ecological function; (3) they may not be specific with respect to different kinds of stressors; (4) they are subject to underlying taxonomic changes across estuarine gradients; (5) they can be labor intensive (e.g., sorting specimens and taxonomic identification); and (6) they are not applied consistently across biogeographic provinces.
