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Benthic Community Assessment Benthic Community Assessment Tool DevelopmentTool Development
Ananda Ranasinghe (Ana)Southern California Coastal Water Research Project (SCCWRP)
Sediment Quality Objectives
for California Bays and Estuaries
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OutlineOutline
Background: Why Benthic Communities?
Approach– Refine and Validate Benthic Indicators– Evaluate Field and Laboratory Methods
Task Details and Schedule
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Why Benthos?Why Benthos? Benthos are living resources
– Direct measure of what legislation intends to protect
Benthic organisms are good indicators of conditions at a site because of– Limited mobility, high exposure to anthropogenic impacts,
integrate different types of impacts, and over time
Already being used to make Regulatory and Sediment Management decisions– Santa Monica Bay removed from 303(d) list
• Was listed for metals in early 1990’s
– 301(h) waivers granted to dischargers
– Toxic hotspot cleanup decisions in San Diego Bay
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Benthic Assessments Pose Benthic Assessments Pose Several ChallengesSeveral Challenges
Interpreting species abundances is difficult– Samples may have tens of species and hundreds of
organisms
Benthic species and abundances vary naturally with habitat– Comparisons to determine altered states should vary
accordingly
Sampling methods vary– Gear, sampling area and sieve size affect species and
individuals captured
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Benthic Indices Meet These Benthic Indices Meet These Challenges Challenges
Benthic Indices
Are Single values
Account for habitat differences
Remove much of the subjectivity associated with data interpretation
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
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California Benthic IndicesCalifornia Benthic Indices Three benthic indices have been developed for California
bays– BRI (Benthic Response Index) for Southern California
• Smith et al. (2001, 2003)– IBI (Index of Biotic Integrity) for San Francisco Bay
• Thompson and Lowe (In press)– RBI (Relative Benthic Index) for several bays
• Hunt et al. 2001
They can all benefit by refinement– Data limitations constrained development
How assessment results relate is not known– Except for some preliminary work completed recently
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Refine And ValidateRefine And ValidateBenthic IndicatorsBenthic Indicators
(3 Tasks)(3 Tasks)
Task 1: Refine existing benthic indices
Task 2: Compare and evaluate benthic tools
Task 3: Identify natural assemblages and the habitat factors that structure them
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Task 1: Refine Benthic ToolsTask 1: Refine Benthic Tools
Initial development of the three indices was constrained by data limitations– Lack of independent data for validation– Insufficient data from highly disturbed sites to define
the entire range of the impact gradient– Uncertainty in the effect of environmental variables
regardless of pollution impacts
Subsequent data collection has removed this constraint for two regions– Southern California bays & San Francisco Bay
Refine all three indices for the two regions– Same approaches as before, but more data
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Task 2: Evaluate Benthic ToolsTask 2: Evaluate Benthic Tools
For the three indices, it is not known– How assessment results relate
– How robust they are to
• Taxonomy (level and accuracy)
• Seasonality, Grain size distribution, TOC and other habitat factors
Evaluate based on:– Agreement with sediment chemistry and sediment toxicity
– Conformity with known spatial and temporal gradients
– Repeatability
– Agreement with each other
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Task 3: Identify Natural Task 3: Identify Natural Assemblages (Biogeography)Assemblages (Biogeography)
Identify naturally occurring assemblages and the habitat factors that structure them– To define habitats for determination of altered states– Evaluate annual and seasonal stability of habitat definitions
Approach– Eliminate potentially contaminated sites from data collected
throughout California using consistent methods– Use cluster analysis to identify assemblages and test habitat
variables across dendrogram splits– Follows Bergen et al. (2001)
Leverages the EMAP West Coast benthic index effort– Potentially increase data availability for index development in
northern CA bays– Preliminary analysis indicates OR & WA coastal bays are similar
to northern CA bays
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Support Methods GuidanceSupport Methods Guidance(2 Tasks)(2 Tasks)
Task 4: Evaluate field sampling methods– Three gear sizes and two sieve mesh sizes are used in
California
– What is the nature and magnitude of these effects on assessment results?
Task 5: Develop sample processing QA procedures– Assessment results vary depending on
• Sorting efficiency, and
• Identification and counting accuracy
– Develop procedures to ensure consistent assessments regardless of which laboratory processes samples
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Task 4: Evaluate Field MethodsTask 4: Evaluate Field MethodsWhy?Why?
Sampling gear affects benthic assessments– Larger gear collect more species and organisms
– Smaller sieves catch
• More and smaller species
• More organisms that can’t be identified to species
Three gears and two sieves are used in California– Gears:
• 0.1m2 Van Veen grab
• 0.05 m2 Van Veen grab
• 0.00785 m2 corer
– Sieves:
• 1.0 mm or 0.5 mm apertures
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Task 4: Evaluate Field MethodsTask 4: Evaluate Field MethodsApproach & DataApproach & Data
Approach: Evaluate assessment differences– For samples processed with different gear and sieves
– Apply indices and measures from Tasks 1 & 2
– Identify the nature and magnitude of gear and sieve effects
Data– For gear questions: 89 sites sampled in summer 2004
– For sieve questions:
• 89 sites sampled in summer 2004
• 64 EMAP 1999 sites (Process 0.5 mm fractions)
• 103+ sites have existing data for San Francisco Bay and Marina Del Rey
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Task 5: Develop QA Task 5: Develop QA ProceduresProcedures
Sample processing and taxonomy affect assessment results– Recovery of organisms from samples– Accuracy of taxonomy and enumeration
QA approach will build on successful models– EMAP, SCBPP, Bight’98, Bight’03 and SCAMIT
Procedures will address three areas– Sorting (organism recovery)– Accuracy of counts– Accuracy of identifications
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ScheduleScheduleTask Activity or Deliverable Completion Date
1: Refine Benthic Tools
1.1 Data available
1.2 Data analysis
October 2004
January 2005
2: Evaluate Benthic Tools
2.1 Data analysis
2.2 Develop application strategy
May 2005
June 2005
3: Identify Natural Assemblages
3.1 Data available
3.2 Data analysis
3.3 Results summary
September 2004
December 2004
January 2005
4: Evaluate Field Methods
4.1 Data available
4.2 Data analysis
February 2005
May 2005
5: Develop QA protocols
5.1 Develop QA Program June 2005