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)

& theLiving Resources Analysis Workgroup (LivRAW)

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

• 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

• 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

Index categories

Conceptual diagram

Indicators selection

• Proposed indicators for 2006 report

Water quality Habitat and lower food web

Dissolved oxygen Bay grasses Clarity (Secchi depth) Phytoplankton Chlorophyll a Bottom habitat

Water quality maps

Water Quality Index2002 – low flow year

Water Quality Index2003 – high flow year

Biotic indices maps

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

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

1. Upper Bay2. Mid Bay3. Lower Bay4. Patapsco-Back5. Patuxent6. Potomac7. Rappannock8. York9. James10.Elizabeth11.Tangier12.Choptank13.Chester14.Lower Eastern shore15.Upper Eastern shore16.Upper Western shore17.Lower Western shore

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)

Chesapeake Bay health assessment

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

Biotic Integrity

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

Retrospective analysis of biotic indicators

Example cumulative frequency distribution

-30

-20

-10

0

10

20

.01 .1 1 5 10 20 30 50 70 80 90 95 99 99.9 99.99

> 1 Km2

Percent

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)

Water quality Habitat and lower food web

Fish and Shellfish

Dissolved oxygen Bay grasses Blue crab Clarity (Secchi depth) Phytoplankton Oyster Chlorophyll a Bottom habitat Striped Bass Chemical contaminants Tidal wetlands Shad Menhaden

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

• 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• 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

• 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

• 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

• 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

• 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 IntegrityMetric Scoring System

Excess Abundance or Excess Biomass Indicative of Stress

Habitat Class

Metric TF

OL

LM

HM sand

HM mud

PO

sand

PO

mud

Shannon-Wiener species diversity index

X X X X X

Total species abundance

X X X X X X X

Total species biomass

X X X X X

Percent abundance of pollution-indicative taxa

X X X X

Percent abundance of pollution-sensitive taxa

X X X

Percent biomass of pollution-indicative taxa

X X X

Percent biomass of pollution-sensitive taxa

X X X

Percent abundance of carnivore & omnivores

X X X X

Percent abundance of deep-deposit feeders

X X

Tolerance Score

X X

Tanypodinae to Chironomidae percent abundance ratio

X

Percent biomass >5 cm below the sediment-water interface

X

X

Percent number of taxa >5 cm below the sediment-water interface

X

Metrics

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

• 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

• 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%?)

Application of BIBI method to PIBI

Application of BIBI method to PIBI

• 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

Findings

Recommendations

• 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

Phytoplankton-IBI: compliance assessment

Phytoplankton-IBI: compliance assessment

Biotic Index2002 data 2002 2002 2002 2002 2003 data 2003 2003 2003 2003

Reporting Regions P-IBI B-IBI SAV BI Reporting Regions P-IBI B-IBI SAV BI

Nanticoke NA NA 0 0 Nanticoke NA NA 0 0

Patapsco 0 27 2 10 Chester NA 13 4 8

Patuxent 18 36 17 24 Patuxent 8 24 18 17

James 17 50 21 29 Mid Bay 30 23 9 21

Elizabeth 33 29 NGZ 31 Choptank 12 31 30 24

York 11 60 34 35 Potomac 25 20 39 28

Chester NA 67 7 37 Rappahannoc 38 48 3 29

Potomac 41 28 47 39 Elizabeth 50 22 NGZ 36

Tangier Sound NA 48 39 43 York 57 16 35 36

Mid Bay 86 22 28 46 Patapsco 10 63 2 36

Choptank 18 60 68 49 James 54 35 24 38

N Bay 39 68 66 57 N Bay 41 56 52 50

Rappahannoc 56 52 70 59 Tangier Sound NA 76 25 50

S Bay 94 75 60 76 S Bay 51 56 57 55

2002 Bay Health Index2002 data 2002 2002 2002 2002 2002 2002 2002 2002 2002

Reporting Regions Chl-a DO Clarity WQI P-IBI B-IBI SAV BI BHI

Patapsco 0 0 0 0 0 27 2 10 5

Nanticoke 0 91 0 30 No data No data 0 0 15

Elizabeth 40 41 58 46 33 29 NGZ 31 39

York 55 93 21 56 11 60 34 35 46

James 73 100 29 67 17 50 21 29 48

Chester 0 100 89 63 No data 67 7 37 50

Potomac 88 65 57 70 41 28 47 39 54

Patuxent 97 100 68 88 18 36 17 24 56

N Bay 54 66 44 55 39 68 66 57 56

Mid Bay 100 56 100 85 86 22 28 46 65

Rappahannoc 86 100 46 77 56 52 70 59 68

Choptank 78 95 95 90 18 60 68 49 69

Tangier Sound 100 100 100 100 No data 48 39 43 72

S Bay 100 100 100 100 94 75 60 76 88

2003 Bay Health Index2003 data 2003 2003 2003 2003 2003 2003 2003 2003 2003

Reporting Regions Chl-a DO Clarity WQI P-IBI B-IBI SAV BI BHI

Nanticoke 9 100 0 36 No data No data 0 0 18

Patapsco 0 0 0 0 10 63 2 36 18

Chester 0 100 0 33 No data 13 4 8 21

Patuxent 3 49 34 29 8 24 18 17 23

Choptank 5 78 0 27 12 31 30 24 26

Mid Bay 0 25 92 39 30 23 9 21 30

Elizabeth 0 76 0 25 50 22 NGZ 36 31

Potomac 17 47 54 39 25 20 39 28 34

York 23 51 21 32 57 16 35 36 34

Rappahannoc 0 87 46 44 38 48 3 29 37

N Bay 35 66 0 33 41 56 52 50 42

James 40 100 20 53 54 35 24 38 46

Tangier Sound 0 100 50 50 No data 76 25 50 50

S Bay 0 88 92 60 51 56 57 55 57

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 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…

Phytoplankton-IBI: compliance assessment