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Development of Toxicity Indicators

Sediment Quality Objectives For California Enclosed Bays and Estuaries. Development of Toxicity Indicators. Scientific Steering Committee Meeting July 26, 2005. Presentation Overview. Objectives Selection of candidate test methods Evaluation of candidates Recommendations

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Development of Toxicity Indicators

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  1. Sediment Quality Objectives For California Enclosed Bays and Estuaries Development of Toxicity Indicators Scientific Steering Committee Meeting July 26, 2005

  2. Presentation Overview • Objectives • Selection of candidate test methods • Evaluation of candidates • Recommendations • Application and integration issues

  3. Toxicity Indicators • Many available data and methods • Several challenges to effective use • Differential sensitivity/ reliability of methods • Confounding factors • Ecological relevance

  4. Objectives • Select a suite of recommended acute and chronic toxicity test methods • Describe sensitivity, reliability, and ecological relevance for each method • Develop thresholds for use in MLOE framework

  5. Attributes of Toxicity Indicator Suite • Protective of benthos and ecologically relevant • Sensitive at the scale of benthic impacts • Dependable • Results are reproducible and comparable among labs • Diverse endpoints • Mortality and sublethal response • Different taxa • Greater representation of benthos • Diverse exposure conditions • Matrix and duration

  6. Approach for Test Selection • Establish a list of candidate methods • Potential to meet desired attributes • Compile and synthesize information about tests • Relate to desired test characteristics • SQO database, literature, lab studies, other scientists • Select recommended tests • Match indicator attributes • Best combination of desired characteristics

  7. California Test Data

  8. Candidate Test Characteristics • Well-documented and feasible for use in California • Appropriate exposure method • Good sensitivity and precision

  9. Candidate Toxicity Indicators • Short-term survival • Multiple species of amphipods • Direct sediment exposure • Widely used in California • Short-term/embryo development and fertilization • Sea urchins and mussels • Frequently used in California • Pore water or sediment-water interface exposure • Chronic/sublethal response • Usually species with limited use in California • Diverse endpoints and exposure methods

  10. Growth Tests • Polychaete • 28 day exposure, fed • Dry weight • Frequently used in California • Seed clam • 7 day exposure, fed • Dry weight • Not used in California

  11. Life Cycle Tests • Amphipod • 28 day exposure, fed • Dry weight, offspring • Occasionally used in California • Copepod • 14 day exposure, fed • Offspring • Not used in California

  12. Cell Stability Test • Oyster • 4 day exposure, fed • Digestive gland cell stability • Not used in California

  13. Candidate Tests • Amphipod survival (10 day sediment exposure) • Ampelisca abdita • Eohaustorius estuarius • Leptocheirus plumulosus • Rhepoxynius abronius • Growth/Reproduction (28 day sediment exposure) • L. plumulosus • Neanthes arenaceodentata (polychaete) • Sea urchin fertilization (1 day pore water exposure) • Purple sea urchin (Strongylocentrotus purpuratus)

  14. Candidate Tests Continued • Embryo development (2-3 day pore water or sediment-water interface exposure) • Purple sea urchin • Mussel (Mytilus galloprovincialis) • Copepod life cycle (14 day sediment exposure) • Amphiascus tenuiremus • Clam growth (7 day sediment exposure) • Mercenaria mercenaria • Oyster lysosomal stability (4 day sediment exposure) • Crassostrea virginica

  15. Presentation Overview • Objectives • Selection of candidate test methods • Evaluation of candidates • Recommendations • Application and integration issues

  16. Evaluation Process • Separate evaluation for short-term survival and sublethal test methods • Short-term survival • 10-day amphipod tests are accepted • Species selection is primary issue • Sublethal tests (many issues) • Feasibility • Consistency • Confounding factors • Sensitivity • Relevance • Cost

  17. Evaluation Process • Short-term survival tests • Compared attributes of four species typically used in 10-day amphipod tests • Technical feasibility and supply • Sensitivity • Confounding factors

  18. Amphipod Survival Test Characteristics * Special permit needed ** Higher test failure rate

  19. Amphipod Survival Ampelisca is markedly less sensitive to CA sediment samples

  20. Amphipod Species Recommendations • Recommended • Eohaustorius estuarius • Leptocheirus plumulosus • Not recommended • Rhepoxynius abronius • Limited availability • Grain size sensitivity • Ampelisca abdita • Low sensitivity • Low test success rate

  21. Evaluation of Sublethal Tests • Compared characteristics of candidate tests • Technical feasibility and supply • Relevance to program objectives • Reproducibility and precision • Documentation and history • Sensitivity • Cost • Sequential process

  22. Sublethal Test Characteristics

  23. Sublethal Test Characteristics * Compared to 10 day amphipod test

  24. Sublethal Tests: Relative Sensitivity

  25. Sublethal Tests: Relative Sensitivity

  26. Sublethal Tests: Relative Sensitivity

  27. Sublethal Tests:Feasibility and Supply • Not recommended • Copepod life cycle test • No commercial test lab capability in California or U.S. • Technically difficult • No information on reproducibility • No standard method • Oyster lysosome stability • No commercial test lab capability in California or U.S. • Technically difficult • No information on reproducibility • No standard method

  28. Sublethal Tests:Exposure Method • Not recommended • Interstitial water tests with sea urchins or mussels • High sensitivity to confounding factors • Less realistic exposure scenario • Remaining candidates have differing combinations of desirable attributes for use in SQO program • Clam growth • Polychaete growth • Amphipod growth/reproduction • Embryo development at sediment-water interface

  29. Sublethal Tests:Documentation and History • Not recommended • Juvenile clam growth test • No standard method • Limited applied experience with method in California

  30. Sublethal Tests:Sensitivity and Cost • Not recommended • Leptocheirus reproduction and growth • Higher relative cost • Lower relative sensitivity

  31. Recommendations • Conduct both acute survival and sublethal test to evaluate sediment toxicity • Acute survival test • Either • E. estuarius • L. plumulosus • Sublethal response test • Either • Polychaete growth test (N. arenaceodentata) • Sediment-water interface test using mussel or sea urchin embryos

  32. Application and Integration Issues • Thresholds • How to interpret results of each test • Integration of results • Multiple tests • Weighting • Applications • New studies • Past data

  33. Thresholds • Several options for establishment • Statistical • Significant difference from control • Variability • Biological • Magnitude of response • Association with benthic community response • A combined approach is recommended • Unaffected (good) vs. affected (bad) • Desire confidence in choice • Statistically-based threshold • Severity of effect • Magnitude and ecological relevance of response is important • Biological-based threshold

  34. Proposed Thresholds • Response not statistically significant different from control • Response different from control, but less than test-specific minimum significant difference (msd) • Result may be within test variability • Clear effect, but below level associated with high probability of benthic effects • Up to 50% effect relative to control (if benthic association unknown) • Above level associated with likely benthic community impacts • > 50% response relative to control (if association unknown) • Reference/no effect • Low effect • Moderate effect • High effect

  35. Integration of Results • A combination of concordance and magnitude of response • Sublethal test results receive less weight • Four categories of effect

  36. Integration of Results

  37. Proposed Integration FrameworkLOE Category

  38. Applications • New studies • Should use both types of tests • If only one used • Reject information? • Only amphipod survival: use result as LOE classification? • Only sublethal data: Use conditionally with modified weighting? • Other test methods used • Ancillary information, not a substitute for specified tests

  39. Applications • Past data • Incomplete test suite? • Other amphipod species? • Other methods?

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