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

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Sediment Quality Objectivesfor California
Enclosed Bays and EstuariesBenthic Indicator
Development

• Scientific Steering Committee
• 26th July 2005

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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

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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 1990s
• 301(h) waivers granted to dischargers
• Toxic hotspot designations for the Bay Protection
  and Toxic Cleanup Program

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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

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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. EPAs guidance for
  biocriteria development

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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

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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

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Approach

• Identify assemblages by cluster analysis
• Standard choices
• Species in 2 samples
• ³v 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

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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 gt ERM or 4 chemicals gt ERL
• Toxic to amphipods
• Located close to point sources
• DO lt 2 ppm
• 714 samples analyzed

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Identified Eight Assemblages
A Puget Sound Fine Sediments
B Puget Sound Coarse Sediments
C Southern California Euhaline Bays
D Polyhaline San Francisco Bay
E Estuaries and Wetlands
F Very Coarse Sediments
G Mesohaline San Francisco Bay
H Limnetic or Freshwater
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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

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Six Candidate Indices
Acronym Name
IBI Index of Biotic Integrity
RBI Relative Benthic Index
BRI Benthic Response Index
RIVPACS River Invertebrate Prediction and Classification System
BQI Benthic Quality Index
Two variations Two variations
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Candidate IndicesComponents
Candidate Index Data
IBI Community measures
RBI Community measures
BRI-TC Species abundances
BRI-MNDF Species abundances
RIVPACS Presence/absence of multiple species
BQI Species abundances community measures
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Index Development Teams
Candidate Index Index Leader Reference
IBI Bruce Thompson Thompson and Lowe (2004)
RBI Jim Oakden Hunt et al. (2001)
BRI Bob Smith Smith et al. (2001, 2003)
RIVPACS David Huff Wright et al. 1993
BQI Bob Smith Rosenberg et al. (2004)
Two variations Two variations Two variations
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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

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Common CriteriaGood (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 gt 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
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Common CriteriaBad (Degraded) Sites

• Meet both of the following criteria
• 1 or more ERM exceedences, or
• 3 or more ERL exceedences, and
• gt50 mortality in an acute amphipod test

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National vs. CA data
South
North
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Data For Benthic Index Development
Habitat Habitat Samples Samples
Habitat Habitat Good Bad
C Euhaline California Bays 85 17
D Polyhaline San Francisco Bay 18 12
E Estuaries and Wetlands 102 3
F Very Coarse Sediments 56 0
G Mesohaline San Francisco Bay 20 4
H Tidal Freshwater 65 0
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Data For Benthic Index DevelopmentNumbers of
samples
Habitat Habitat Calibration Calibration Validation Validation
Habitat Habitat G B G B
C Euhaline California Bays 75 9 10 8
D Polyhaline San Francisco Bay 9 6 11 6
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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

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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

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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

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Overall Classification AccuracyValidation Data
()
Index Overall (n35)
RIVPACS 83
BRI-TC 77
IBI 70
BRI-MNDF 63
BQI 63
RBI 51
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Habitat Classification Accuracy Validation Data
()
Index Southern California (n18) San Francisco Bay (n17)
RIVPACS 72 94
BRI-TC 72 82
IBI 67 73
BRI-MNDF 56 71
BQI 50 76
RBI 22 82
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Status Classification Accuracy Validation Data
()
Index Good Sites (n21) Bad Sites (n14)
RIVPACS 86 79
BRI-TC 81 71
IBI 100 29
BRI-MNDF 67 57
BQI 81 36
RBI 52 50
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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

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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

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Disagreements with Status Designations
Number of Candidates Disagreeing N (S35)
0 8
1 9
2 5
3 6
4 4
5 2
6 1
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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

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Effect of Status Changeon Overall Classification
Accuracy
Index Original After Change
RIVPACS 83 83
BRI-TC 77 89
IBI 70 76
BRI-MNDF 63 74
BQI 63 80
RBI 51 63
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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

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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

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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

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Repeatability

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

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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