Benthic Community Assessment Benthic Community Assessment Tool DevelopmentTool Development

Ananda Ranasinghe (Ana)Southern California Coastal Water Research Project (SCCWRP)

anar@sccwrp.org

Sediment Quality Objectives

for California Bays and Estuaries

OutlineOutline

Background: Why Benthic Communities?

Approach– Refine and Validate Benthic Indicators– Evaluate Field and Laboratory Methods

Task Details and Schedule

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

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

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

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

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

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

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

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

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

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

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

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

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