Assessing ecological integrity for impaired waters decisions in Chesapeake Bay, USA

Versar Inc., Ecological Sciences and Applications, 9200 Rumsey Road, Columbia, Maryland 21045, USA.
Marine Pollution Bulletin (Impact Factor: 2.99). 01/2009; 59(1-3):48-53. DOI: 10.1016/j.marpolbul.2008.11.011
Source: PubMed


To meet the requirements of the Clean Water Act, the States of Maryland and Virginia are using benthic biological criteria for identifying impaired waters in Chesapeake Bay and reporting their overall condition. The Chesapeake Bay benthic index of biotic integrity (B-IBI) is the basis for these biological criteria. Working together with the states and the US Environmental Protection Agency, we developed a method for impairment decisions based on the B-IBI. The impaired waters decision approach combines multiple benthic habitat-dependent indices in a Bay segment (equivalent to water bodies in the European Water Framework Directive) with a statistical test of impairment. The method takes into consideration uncertainty in reference conditions, sampling variability, multiple habitats, and sample size. We applied this method to 1430 probability-based benthic samples in 85 Chesapeake Bay segments. Twenty-two segments were considered impaired for benthic community condition. The final decision for each segment considers benthic condition in combination with key stressors such as dissolved oxygen and toxic contaminants.

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Available from: Daniel Dauer, Aug 05, 2014
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    • "Benthic macroinfaunal communities are a central part of habitat assessment programs in coastal waters around the world (Diaz et al., 2004; Borja et al., 2006; Llansó et al., 2009). Macroinfauna are used because they are relatively immobile residents in sediments, where contaminants accumulate, and have a diversity of life stages and feeding modes that make them responsive to multiple types of disturbance (McIntyre 1985; Warwick 1988; Gray and Elliott, 2009). "
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    ABSTRACT: The AZTI Marine Biotic Index (AMBI) requires less geographically-specific calibration than other benthic indices, but has not performed as well in US coastal waters as it has in the European waters for which it was originally developed. Here we examine the extent of improvement in index performance when the Ecological Group (EG) classifications on which AMBI is based are derived using local expertise. Twenty-three US benthic experts developed EG scores for each of three regions in the United States, as well as for the US as a whole. Index performance was then compared using: (1) EG scores specific to a region, (2) national EG scores, (3) national EG scores supplemented with standard international EG scores for taxa that the US experts were not able to make assignments, and (4) standard international EG scores. Performance of each scheme was evaluated by diagnosis of condition at pre-defined good/bad sites, concordance with existing local benthic indices, and independence from natural environmental gradients. The AMBI performed best when using the national EG assignments augmented with standard international EG values. The AMBI using this hybrid EG scheme performed well in differentiating apriori good and bad sites (>80% correct classification rate) and AMBI scores were both concordant and correlated (rs = 0.4–0.7) with those of existing local indices. Nearly all of the results suggest that assigning the EG values in the framework of local biogeographic conditions produced a better-performing version of AMBI. The improved index performance, however, was tempered with apparent biases in score distribution. The AMBI, regardless of EG scheme, tended to compress ratings away from the extremes and toward the moderate condition and there was a bias with salinity, where high quality sites received increasingly poorer condition scores with decreasing salinity.
    Ecological Indicators 03/2015; 50:99-107. DOI:10.1016/j.ecolind.2014.11.005 · 3.44 Impact Factor
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    • "The CBP design divides the Maryland Mid-Bay Mainstem into two strata, the Mid-Bay Mainstem proper and the Upper Bay Mainstem (Dauer and Llansó 2003). The Mid-Bay Mainstem is usually in worse condition than the Upper Bay Mainstem because it has a higher incidence of low dissolved oxygen events (Dauer and Llansó 2003; Llansó et al. 2008), which is one reason why these two strata are considered separately by CBP. In addition , the deep (>12 m) trough of the Mid-Bay Mainstem is azoic (Llansó et al. 2003). "
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    ABSTRACT: Federal and state environmental agencies conduct several programs to characterize the environmental condition of Chesapeake Bay. These programs use different benthic indices and survey designs, and have produced assessments that differ in the estimate of the extent of benthic community degradation in Chesapeake Bay. Provided that the survey designs are unbiased, differences may exist in the ability of these indices to identify environmental degradation. In this study we compared the results of three indices calculated on the same data, and the assessments of two programs: the Chesapeake Bay Program and the Mid-Atlantic Integrated Assessment (MAIA). We examined the level of agreement of index results using site-based measures of agreement, evaluated sampling designs and statistical estimation methods, and tested for significant differences in assessments. Comparison of ratings of individual sites was done within separate categories of water and sediment quality to identify which indices summarize best pollution problems in Chesapeake Bay. The use of different benthic indices by these programs produced assessments that differed significantly in the estimate of degradation. A larger fraction of poor sites was classified as good by the Environmental Monitoring and Assessment Program's Virginian Province and MAIA benthic indices compared to the Chesapeake Bay benthic index of biotic integrity, although overall classification efficiencies were similar for all indices. Differences in survey design also contributed to differences in assessments. The relative difference between the indices remained the same when they were applied to an independent dataset, suggesting that the indices can be calibrated to produce consistent results.
    Environmental Monitoring and Assessment 01/2009; 150(1-4):119-27. DOI:10.1007/s10661-008-0678-7 · 1.68 Impact Factor
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    • "They established that (i) validation should test index performance on data independent of those used to develop (calibrate) the index, and potentially be performed by scientists other than those proposing the index, (ii) classification criteria for acceptance should be set a priori, and (iii) alternatively or additionally, include strong a posteriori justification based on best professional judgment (Borja and Dauer, 2008). In this special issue, old and new indices have been validated for different areas, such as Chesapeake Bay (Llansó et al., 2009; Williams et al., 2009). There are at least two aspects of validation in which improvements are desirable in the next decade. "
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    ABSTRACT: During the last decade, there have been substantial scientific advances in the development of indices that measure the condition of biological ecosystem elements in coastal and estuarine waters. Though successful, these advances were only the initial steps and a special session on use of indices in ecological integrity assessments was held at the Coastal and Estuarine Research Federation meeting to focus the field on the most appropriate directions for the next decade. The session identified four primary scientific challenges: (i) reduce the array of indices by identifying the index approaches that are most widely successful; (ii) establish minimum criteria for index validation; (iii) intercalibrate methods to achieve uniform assessment scales across geographies and habitats; and (iv) integrate indices across ecosystem elements. Where an explosion of indices characterized the last decade, the next decade needs to be characterized by consolidation. With increased knowledge and understanding about the strengths and weaknesses of competing index approaches, the field needs to unify approaches that provide managers with the simple answers they need to use ecological condition information effectively and efficiently.
    Marine Pollution Bulletin 01/2009; 59(1-3):1-4. DOI:10.1016/j.marpolbul.2008.11.006 · 2.99 Impact Factor
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