ssc benthicindicators

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

Sediment Quality Objectives for California Enclosed Bays and Estuaries Benthic Indicator Development Scientific Steering Committee 26th July 2005

Overview : 

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

Why Benthos?: 

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

Benthic Assessments Pose Several Challenges: 

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

Benthic Indices Meet These Challenges: 

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

Overview : 

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

Define Habitat Strata: 

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

Approach: 

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

Data: 

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

Identified Eight Assemblages: 

Identified Eight Assemblages

Overview : 

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

Six Candidate Indices: 

Six Candidate Indices

Candidate Indices Components: 

Candidate Indices Components

Index Development Teams: 

Index Development Teams

Common Definitions: 

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

Common Criteria “Good” (Reference) Sites: 

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

Common Criteria “Bad” (Degraded) Sites: 

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

National vs. CA data: 

National vs. CA data South North

Data For Benthic Index Development: 

Data For Benthic Index Development

Data For Benthic Index Development Numbers of samples: 

Data For Benthic Index Development Numbers of samples

The Calibration Process: 

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

Overview : 

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

Index Validation Approaches: 

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

Overall Classification Accuracy Validation Data (%): 

Overall Classification Accuracy Validation Data (%)

Habitat Classification Accuracy Validation Data (%): 

Habitat Classification Accuracy Validation Data (%)

Status Classification Accuracy Validation Data (%): 

Status Classification Accuracy Validation Data (%)

Potential Reasons for Low Classification Accuracy: 

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

Are Validation Sites Misclassified?: 

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

Disagreements with Status Designations: 

Disagreements with Status Designations

Biology Comparison: 

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

Effect of Status Change on Overall Classification Accuracy: 

Effect of Status Change on Overall Classification Accuracy

Overview : 

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

Complete the Index Validation Process: 

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

Biology Classification: 

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

Repeatability: 

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

Summary: 

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

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