Development of Toxicity Indicators

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

• Objectives
• Selection of candidate test methods
• Evaluation of candidates
• Recommendations
• Application and integration issues

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Toxicity Indicators

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

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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

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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

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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

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California Test Data
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Candidate Test Characteristics

• Well-documented and feasible for use in
  California
• Appropriate exposure method
• Good sensitivity and precision

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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

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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

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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

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Cell Stability Test

• Oyster
• 4 day exposure, fed
• Digestive gland cell stability
• Not used in California

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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)

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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

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Presentation Overview

• Objectives
• Selection of candidate test methods
• Evaluation of candidates
• Recommendations
• Application and integration issues

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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

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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

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Amphipod Survival Test Characteristics
Species Availability(months) Suppliers TechnicalDifficulty ConfoundingFactors
Ampelisca 8 Field/few Moderate Ammonia
Eohaustorius 12 Field/few Low Ammonia
Leptocheirus 12 Lab/few Low Ammonia
Rhepoxynius 12 Field/few Low AmmoniaGrain size
Special permit needed Higher test failure
rate
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Amphipod Survival

• Ampelisca is markedly less sensitive to CA
  sediment samples

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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

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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

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Sublethal Test Characteristics
Test Availability(months) Suppliers TechnicalDifficulty Method Guidance
Amphipod growth 12 Lab/few Moderate Standard
Polychaete growth 12 Lab/one Moderate Standard
Pore water fertilization 8 Field/many Moderate Standard
Pore water development 6-12 Field/many Low Standard
SWI development 6-12 Field/many Low Published
Copepod life cycle 12 Lab/one High Published
Clam growth 8 Lab/many Low Published
Oyster lysosome 8 Field/many Moderate Report
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Sublethal Test Characteristics
Test Among Lab Variability Within Lab Variability More Sensitive Than Amphipod Survival Test Relative Precision of Response
Amphipod growth Fair Good Sometimes Low
Polychaete growth Good Good Sometimes Low
Pore water fertilization Good Fair Sometimes High
Pore water development Good Good Sometimes High
SWI development Fair Good Sometimes Low
Copepod life cycle ? Good Often High
Clam growth Good Fair Sometimes Similar
Oyster lysosome ? ? Rarely Low
Compared to 10 day amphipod test
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Sublethal Tests Relative Sensitivity
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Sublethal Tests Relative Sensitivity
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Sublethal Tests Relative Sensitivity
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Sublethal TestsFeasibility 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

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Sublethal TestsExposure 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

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Sublethal TestsDocumentation and History

• Not recommended
• Juvenile clam growth test
• No standard method
• Limited applied experience with method in
  California

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Sublethal TestsSensitivity and Cost

• Not recommended
• Leptocheirus reproduction and growth
• Higher relative cost
• Lower relative sensitivity

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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

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Application and Integration Issues

• Thresholds
• How to interpret results of each test
• Integration of results
• Multiple tests
• Weighting
• Applications
• New studies
• Past data

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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

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Proposed Thresholds

• Reference/no effect
• Low effect
• Moderate effect
• High effect

• 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
• gt 50 response relative to control (if
  association unknown)

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Integration of Results

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

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Integration of Results
Category Description
Reference No effect in any test
Marginal Deviation Low effect in only one test, may not be reproducible or ecologically significant
Moderate Effect measured in multiple tests or a severe effect in one test
High Severe effect in one test and concordance of effects among tests
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Proposed Integration FrameworkLOE Category
Amphipod Survival Result Amphipod Survival Result Amphipod Survival Result Amphipod Survival Result
Sublethal Result Ref Low Moderate High
Ref Ref Marginal Deviation Moderate Moderate?
Low Ref Moderate Moderate High
Moderate Marginal Deviation Moderate High High
High Moderate Moderate High High
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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

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Applications

• Past data
• Incomplete test suite?
• Other amphipod species?
• Other methods?