Sediment Quality Objectives for California Enclosed Bays and Estuaries: Benthic Indicator Development

1. Sediment Quality Objectivesfor California Enclosed Bays and EstuariesBenthic Indicator Development Scientific Steering Committee 26th July 2005

2. Overview • Why Benthos and Benthic Indices? • The Index Development Process • Define Habitat Strata • Calibrate Candidate Benthic Indices • Validate and Evaluate Candidate Indices • Proposed Next Steps

3. Why Benthos? • Benthic organisms are living resources • Direct measure of what legislation intends to protect • They are good indicators • Sensitive, limited mobility, high exposure, integrate impacts, integrate over time • Already being used to make regulatory and sediment management decisions • Santa Monica Bay removed from 303(d) list • Listed for metals in the early 1990’s • 301(h) waivers granted to dischargers • Toxic hotspot designations for the Bay Protection and Toxic Cleanup Program

4. Benthic Assessments Pose Several Challenges • Interpreting species abundances is difficult • Samples may have tens of species and hundreds of organisms • Benthic species and abundances vary naturally with habitat • Different assemblages occur in different habitats • Comparisons to determine altered states should vary accordingly • Sampling methods vary • Gear, sampling area and sieve size affect species and individuals captured

5. Benthic Indices Meet These Challenges • Benthic Indices • Remove much of the subjectivity associated with data interpretation • Account for habitat differences • Are single values • Provide simple means of • Communicating complex information to managers • Tracking trends over time • Correlating benthic responses with stressor data • Are included in the U.S. EPA’s guidance for biocriteria development

6. Overview • Why Benthos and Benthic Indices? • The Index Development Process • Define Habitat Strata • Calibrate Candidate Benthic Indices • Validate and Evaluate Candidate Indices • Proposed Next Steps

7. Define Habitat Strata • Rationale • Species and abundances vary naturally from habitat to habitat • Benthic indicators and definitions of reference condition should vary accordingly • Objectives • Identify naturally occurring benthic assemblages, and • The habitat factors that structure them

8. Approach • Identify assemblages by cluster analysis • Standard choices • Species in ≥ 2 samples • ³√ transform, species mean standardization • Bray Curtis dissimilarity with step-across adjustment • Flexible sorting ß=-0.25 • Evaluate habitat differences between assemblages • Salinity, % fines, depth, latitude, longitude, TOC • Using Mann-Whitney tests

9. Data • EMAP data enhanced by regional data sets • Comparable methods • Sampling, measurements, taxonomy • OR and WA data included • Potential to increase amount of data for index development • 1164 samples in database • Eliminated potentially contaminated sites • ≥ 1 chemical > ERM or ≥ 4 chemicals > ERL • Toxic to amphipods • Located close to point sources • DO < 2 ppm • 714 samples analyzed

10. Identified Eight Assemblages

13. Overview • Why Benthos and Benthic Indices? • The Index Development Process • Define Habitat Strata • Calibrate Candidate Benthic Indices • Validate and Evaluate Candidate Indices • Proposed Next Steps

14. Six Candidate Indices

15. Candidate IndicesComponents

16. Index Development Teams

17. Common Definitions • A common set of definitions were established • For “Good” and “Bad” sites • Used in two ways • Identify data to be withheld from index development • Subsequently used to validate index • Goal: A set of clearly affected or reference sites to evaluate index performance • “A Gold Standard” • Identify reference and degraded condition for index calibration

18. Common Criteria“Good” (Reference) Sites • Meet all the following criteria: • Far from known point sources • Data available for sediment chemistry and at least one amphipod toxicity test • No ERM* exceedences • No more than 3 ERL* exceedences • No toxicity • Amphipod survival > 83% • Species abundance list does not indicate bad biology (In progress) *: As, Cd, Cu, Pb, Hg, Ag, Zn, Hmw(8) & Lmw(11) PAH, Total PCB

19. Common Criteria“Bad” (Degraded) Sites • Meet both of the following criteria • 1 or more ERM exceedences, or 3 or more ERL exceedences, and • >50% mortality in an acute amphipod test

20. National vs. CA data North South

21. Data For Benthic Index Development

22. Data For Benthic Index DevelopmentNumbers of samples

23. The Calibration Process • Identify habitats with sufficient data • “Good” and “Bad” sites • For index calibration and validation • Distribute calibration data • Teams calibrate candidate indices • Distribute independent data for validation • Teams apply candidates to data • Results compiled for evaluation

24. Overview • Why Benthos and Benthic Indices? • The Index Development Process • Define Habitat Strata • Calibrate Candidate Benthic Indices • Validate and Evaluate Candidate Indices • Proposed Next Steps

25. Index Validation Approaches • Classification accuracy • Chemistry and toxicity • Biologist best professional judgment • Repeatability • Same day • Same site on different days • Independence from natural gradients • Correlations with other information • Species richness • Other indices

26. Overall Classification AccuracyValidation Data (%)

27. Habitat Classification Accuracy Validation Data (%)

28. Status Classification Accuracy Validation Data (%)

29. Potential Reasons for Low Classification Accuracy • Do threshold and scaling problems exist? • Does an index correlate well with condition, but an incorrect threshold lead to the wrong interpretation? • Are chemistry-toxicity “bad” definitions inadequate? • Chemistry criteria were less stringent than many other benthic index efforts

33. Are Validation Sites Misclassified? • Is our “Gold Standard” correct? • Are multiple indices disagreeing? • How do index disagreements relate to biology? • Samples with multiple disagreements evaluated • Using biologist best professional judgment

34. Disagreements with Status Designations

35. Biology Comparison • For six of seven samples • Biologists agreed that the chemistry-toxicity status was incorrect • All four biologists agreed for four samples • 75% agreement for other two • “Gold Standard” is tarnished

36. Effect of Status Changeon Overall Classification Accuracy

37. Overview • Why Benthos and Benthic Indices? • The Index Development Process • Define Habitat Strata • Calibrate Candidate Benthic Indices • Validate and Evaluate Candidate Indices • Proposed Next Steps

38. Complete the Index Validation Process • Classification accuracy • Chemistry and toxicity • Biologist best professional judgment • Repeatability • Same day • Same site on different days • Independence from natural gradients • Correlations with other information • Species richness • Other indices

39. Biology Classification • Panel of six external experts • Evaluate 20-25 samples • Samples where 5 of 6 experts agree will establish a new “Gold Standard” • To be used in the same way as the chemistry-toxicity classification

40. Repeatability • Identify sites where • Multiple samples were collected on the same visit • Multiple visits to the same site • Evaluate candidate index stability

41. Summary • We will be able to develop benthic indices for two habitats • Some indices validating well • Validation rates with sediment toxicity and chemistry data are low • Need to re-visit our scaling methods for some indices • Need to establishing biology-based good and bad criteria • Best professional judgment of an independent panel of experts • Have more validation steps to complete before making final selections