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Finalizing the Chesapeake Bay Health Index (BHI) Part 1: Water Quality Index Part 2: Biotic Index. Bill Dennison Ben Longstaff, Michael Williams, Claire Buchanan, Roberto Llans ó , and Peter Bergstrom On behalf of the Tidal Monitoring and Analysis Workgroup (TMAW) & the

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Finalizing the chesapeake bay health index bhi part 1 water quality index part 2 biotic index

Finalizing the Chesapeake Bay Health Index (BHI)Part 1: Water Quality IndexPart 2: Biotic Index

Bill Dennison

Ben Longstaff, Michael Williams, Claire Buchanan, Roberto Llansó, and Peter Bergstrom

On behalf of the

Tidal Monitoring and Analysis Workgroup (TMAW)

& the

Living Resources Analysis Workgroup (LivRAW)

Major outcomes
Major outcomes

  • Water Quality Index (Chlorophyll, Dissolved Oxygen, Clarity) will be calculated and mapped, but not necessarily included in calculation of Bay Health Index

  • Bay Health Index (SAV, BIBI, PIBI) will be calculated, tabulated and used to compare reporting regions

  • Reporting regions will be altered to group smaller tributaries, more aligned with trib strategies

  • A 0-100 scale will be used with 5 divisions (stoplight color scheme)

  • A Bay-wide integration will be calculated from the area-weighted individual indices

Strengths of health assessment approach
Strengths of health assessment approach

  • Rigorous, ecosystem health-related thresholds

  • Biotic indicators are integrative in nature

    • SAV (long term)

    • Benthic IBI (medium term)

    • Phytoplankton IBI (short term)

  • Indicators provide assessment of different Chesapeake Bay habitats

    • Shallow water assessed with SAV

    • Deep water assessed with Benthic IBI

    • Open water assessed with Phytoplankton IBI

    • Mid-channel assessed with water quality

  • Long term data trends of each indicator available

Key communication issues
Key communication issues

  • Provide individual data maps

  • Express long term data trends of each indicator

  • Develop new table: sample size (146 x 12-20; 250 x 1; 25 x 12-13); time frame for integration (chl = Mar-Sep; DO = Jun-Sep; Clarity = Mar-Nov); range of values, etc.

  • Develop ways to calculate and express variability

  • Use conceptual diagrams to link indicators and various key living resources & habitats

Indicators selection
Indicators selection

  • Proposed indicators for 2006 report

Water Quality Index

2002 – low flow year

Water Quality Index

2003 – high flow year

Future indicator development
Future indicator development

  • Chemical contaminants

    • Human health threshold (not water quality)

    • Tissue samples (integrate over time)

    • Do not respond annually

    • Uncertain geographic representation

    • Confusion with EPA Coastal Condition vs. 303(d) listing

  • Nutrients

    • Trend data has linear and non-linear trends

    • Criteria definition needs to be elucidated

    • Other examples of separating nutrient concentrations from symptom expressions (e.g., National Estuarine Eutrophication Assessment)

    • Nutrient limitation approach (Fisher et al.) and nutrient concentration approach could be used

    • PIBI and Chl are good integrators of nutrients

    • Nutrients are ‘flashy’ vs. more integrative measures

Reporting regions issues
Reporting regions issues

  • Use detailed maps of depth contours, residence time

  • Indicate stations on data maps

  • Provide station by station data (e.g., pdf)

  • Develop a hyperlinked data set (2007)

  • Work toward developing mapping approaches and continuous data distributions so that reporting regions are less important

Revised reporting regions
Revised reporting regions

  • Upper Bay

  • Mid Bay

  • Lower Bay

  • Patapsco-Back

  • Patuxent

  • Potomac

  • Rappannock

  • York

  • James

  • Elizabeth

  • Tangier

  • Choptank

  • Chester

  • Lower Eastern shore

  • Upper Eastern shore

  • Upper Western shore

  • Lower Western shore

Benchmark approach issues
Benchmark approach issues

  • Investigate different methods of establishing benchmarks

    • Percentiles (cumulative frequency distributions)

    • Link benchmarks to living resources (e.g., DO from BIBI; Clarity from SAV)

    • Model results

  • Compare different thresholds (table)

Biotic indices: Bay grasses, Benthic Index of Biotic Integrity, Phytoplankton Index of Biotic Integrity

Next steps
Next steps

  • Link spatially explicit bay health index with Bay Health & Restoration Assessment

  • Continue to build technical supporting documentation

  • Mock up communication product(s) using alternative approaches

  • Engage communication specialists, IC, STAC and other reviewers and incorporate feedback

Indicators selection1
Indicators selection

  • Current indicators

  • Not all indicators can be included at this stage because:

    • Some are still being developed (tidal wetlands and menhaden)

    • Timeframe not suitable (chemical contaminants)

    • Goals and assessment at bay-wide scale (striped bass, blue crab, oysters)

    • Indicator is for a specific location only (shad)

Reporting regions1
Reporting regions

  • Discrete regions of the Bay used for purpose of reporting

  • Not too many in number (currently 14)

  • Must contain sufficient number of sampling stations for analysis

  • Based on current CBP segmentation

  • Group like water bodies

  • Align, where possible with tributary strategy boundaries, other strata (e.g., B-IBI)

Methods biotic index
Methods: Biotic Index

  • Aquatic grasses (SAV)

    • Michael Williams (CBP/UMCES)

  • Benthic Index of Biotic Integrity (B-IBI)

    • Roberto Llansó (Versar)

  • Phytoplankton Index of Biotic Integrity (P-IBI)

    • Claire Buchanan (ICPRB)

  • Biotic and Bay health index

    • Michael Williams (CBP/UMCES)

Aquatic grasses goals
Aquatic grasses: goals

  • Restoration goals for each Chesapeake Bay segment (Use Attainability Analysis)

  • All segment goals within a reporting region combined  reporting region goal (ha)

Aquatic grasses compliance assessment
Aquatic grasses: compliance assessment

  • Most recent year data

  • Compliance of a reporting region

    • Total area present (acres) as a proportion of the total restoration goal

  • If SAV acreages exceed the restoration acreages, that segment’s SAV was reduced to equal the restoration acreage (i.e., can only = 100% or less)

Benthic ibi data
Benthic-IBI: data

  • Chesapeake Bay Benthic Monitoring Program data

  • Collected August through September

  • Approximately 250 stratified random sampling stations

Location of Benthic monitoring probability-based sites in 2005

Benthic ibi goals
Benthic-IBI: goals

  • Chesapeake Bay Monitoring Programs have adopted Benthic Community Restoration Goals as a monitoring tool

  • The restoration goals are quantitative benchmarks: They describe the characteristics of benthic assemblages expected in non-degraded habitats

  • The B-IBI is scaled from 1 to 5, and sites with values of 3.0 or more are considered to meet the Restoration Goals.

Benthic ibi compliance assessment
Benthic-IBI: compliance assessment

  • Multi-metric, habitat-specific index of benthic community condition

  • Selection of metrics and the values for scoring metrics developed separately for each of seven benthic habitat types in Chesapeake Bay

  • Described in:

    • Weisberg et al. (1997), Estuaries 20:149-158

    • Alden et al. (2002), Environmetrics 13:473-498

Benthic Index of Biotic Integrity

Metric Scoring System

Benthic ibi compliance assessment1
Benthic-IBI: compliance assessment

  • Estimate the amount of area in a reporting region that meets the Restoration Goals (B-IBI >=3.0)

  • Every site that meets the goal assigned a value of 1, otherwise a site is assigned 0

  • Proportion of area meeting the goals and its variance is estimated

  • For some reporting regions, estimates were calculated for subregions and these were then combined using proportion of area as weighting factor.

Phytoplankton data
Phytoplankton: Data

  • VA and MD Phytoplankton Monitoring Survey Data

  • Approximately 25 stations

  • Collected 12-13 times a year

    • Spring (March, April, May)

    • Summer (July, August, September)

Phytoplankton ibi goal
Phytoplankton IBI - Goal

  • PIBI interim goal of 4.0 (1.0 - 5.0 scale)

    • high level of biological integrity is certain

    • very low risk of harmful algal blooms

    • assoc. WQ meets SAV habitat requirements

    • commensurate with Ches Bay water clarity and DO criteria attainment

  • Not establish how attainment of a PIBI goal of 4.0 should be measured (mean? median? threshold? 10th%?)


  • Pass/fail method currently used to report BIBI status can also be successfully applied to PIBI

  • Goal of “100% PIBI > 3.0 threshold criterion” is in general agreement with goal of “median or mean PIBI = 4.0”

  • “% of Goal” method used to report the 3 biotic and 3 water quality indicators differs from “% attainment of water quality criteria” methods


  • Align methods and goals to that used for the Benthic IBI

    • % achievement of the threshold criteria

    • Threshold criteria defined as median PIBI of 3

    • Area weighted

Question to address
Question to address:

Do we agree with the proposed approach for assessing compliance for each of the three indicators (Aquatic grass, BIBI, PIBI)?

  • Data sources?

  • Goals and thresholds?

  • Compliance assessment methods?

    Do we agree that Biotic index is determined as the average of the 3 compliance estimates

Question to address1
Question to address:

  • Do we agree that Bay health index is determined as the average of the 2 component indices (Water quality index & Biotic index)?

  • What are the appropriate groupings for the BHI values: Those proposed? Another?

  • How might the index be improved in the future…