The biological condition gradient: updates and opportunities

The biological condition gradient: updates and opportunitiesMichael PaulJeroen Gerritsen

Tetra Tech, Inc.Center for Ecological Sciences

Clean Water ActGoal = Integrity: “Restore and maintain…biological

integrity” – 101(a)

Interim Goal = Aquatic Life Use: “…water quality which provides for the

protection and propagation of fish, shellfish, and wildlife…” – 101(a)(2)

Intro

Biological Integrity The ability of an aquatic ecosystem

to support and maintain a balanced, integrated and adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of natural habitats within a region

CLASSIFICATION

REFERENCE

Intro

Convention – Single Indicator Thresholds

Inde

x S

core

0

10

20

30

40

50

60

70

80

90

100

Reference Stressed

x

x

x

Is this the tool we need?

Is it a race to the middle?

Does is protect the best sites?

(Anti-deg, ORW)

Does it protect further degradation?

Is it a realistic goal for restoration?

(TMDL prioritization; setting realistic expectations)

What if reference condition varies?

Intro

Chemistry, habitat, and/or flow regime severely altered from natural

conditions.

Watershed, habitat, flow regime and water chemistry as naturally

occurs.

5

6

4

3

2

1

Levels of Biological Condition

Bio

logi

cal C

ondi

tion

Level of Exposure to Stressors

Natural structural, functional, and taxonomic integrity is preserved.

Structure & function similar to natural community with some additional taxa & biomass; ecosystem level functions are fully maintained.

Evident changes in structure due to loss of some rare native taxa; shifts in relative abundance; ecosystem level functions fully maintained.

Moderate changes in structure due to replacement of sensitive ubiquitous taxa by more tolerant taxa; ecosystem functions largely maintained.

Sensitive taxa markedly diminished; conspicuously unbalanced distribution of major taxonomic groups; ecosystem function shows reduced complexity & redundancy.

Extreme changes in structure and ecosystem function; wholesale changes in taxonomic composition; extreme alterations from normal densities.

Another Option: The Biological Condition Gradient

Biological Condition

The Biological Condition Gradient

NaturalVariability

Increasing Level of Stressors

Minimal changes in structure & function

Evident changes in structure and minimal changes in function

Severe changes in structure & function

2

3

6

Moderate changes in structure & minimal changes in function

Major changes in structure & moderate changes in function

14

5

Natural structural, functional, and taxonomic integrity is preserved.



NaturalVariability

Increasing Level of Stressors






4

5

3Natural structure and function of biotic community maintained

1

6

Evident changes in structure due to loss of some rare native taxa; shifts in relative abundance; ecosystem level functions fully maintained

2



NaturalVariability

- - No Effect - -





Natural structure and function of biotic community maintained


12

3

6Extreme changes in structure and ecosystem function; wholesale changes in taxonomic composition; extreme alterations from normal densities.

4

The Biological Condition GradientConceptual model of aggregated

biological knowledge to describe changes with increasing stress

Based on combination of ecological theory and empirical knowledge

Regional calibration Conceptual model Quantitative decision model

Intro

Basic idea What attributes do we expect to see?

Species, abundances Habitats Biotopes Interactions

What attributes do we not expect to see? What is missing? What is present that shouldn’t be?

Have experts interpret samples into the BCG classes.

Operationalize their decisions – i.e., “train” a model

Method

How Classification (you know….) Identify reference condition and

stressor gradient (you know…) Expert panel:

Identify attributes and their metrics Assign sites to levels of BCG Develop rules for assigning sites

(decision criteria) Develop model(s) for automated

replication of panel decisions Test and iterate

Method

Evidence for “best” Present-day conditions Historical reconstruction

Historical documents (descriptions, journals, charts, aerial images)

Fish/shellfish landings records Museum collections Archeological evidence (middens, other

digs) Paleo evidence (diatoms, forams, pollen)

Method

AttributesI. Historically documented, sensitive, long-lived,

regionally endemic taxaII. Highly sensitive or specialist taxaIII. Sensitive and common taxaIV. Taxa of intermediate toleranceV. Tolerant taxaVI. Non-native taxaVII. Organism conditionVIII. Ecosystem FunctionIX. Spatial and temporal extent of detrimental effectsX. Ecosystem connectance

Method

N Common Name19 American Brook lamprey5 Banded Sunfish3 Bridled shiner

29 Burbot15 Creek chubsucker

2194 Slimy sculpin21 Swamp darter

8221 Brook trout, wild

Slimy sculpin

Burbot

Attribute 2 taxa: most sensitive; the first to disappear

Wild brook trout

Attribute 3 taxa: moderately sensitive

Sensitive taxa

Attributes: New England FishMethod

N Common Name521 Chain pickerel

9046 Common shiner2552 Cutlips minnow

10020 Fallfish118 Fourspine stickleback

15499 Longnose dace1764 Pumpkinseed4485 Redbreast sunfish612 Redfin pickerel

1344 Spottail shiner8832 Tesselated darter

2 White perch

Attribute 4 taxa: broadly tolerant of many conditions

Fallfish

Redbreast sunfish

Longnose dace

Tesselated darter


N Common Name259 Banded killifish

55137 Blacknose dace479 Brown bullhead

4974 Creek chub595 Golden shiner

23426 White sucker187 Yellow bullhead

Attribute 5 taxa: Highly tolerant; increased abundance in stressed sites

White sucker

Blacknose dace


Assign sites to BCG levels Panel members assign sites to BCG

levels using species composition information

Best sites (reference) are not necessarily Level 1!

Capture critical information for decisions

Method

TALU_SampID HA03 Level Area (km²) 19.06

StationID AN0018 5 Pct Urban 13.98

Station Name Culvers Ck Pct Agr 1.59

WMA 1 Pct Forest 48.40

Gradient HighPct

Wetlands 18.16

CollDate 10/13/1992

Total Habitat

Score Not ScoredBCG

Attribute FinalIDIndividu

als OrderFamily (Tribe)

4Crangonyx pseudogracilis 8 Amphipoda Gammaridae

3 Stenonema smithae 3Ephemeroptera Heptageniidae

3 Nigronia serricornis 2 Megaloptera Corydalidae

4 Argia 1 OdonataCoenagrionidae

4 Cheumatopsyche 45 TrichopteraHydropsychidae

5 Hydropsyche betteni 43 TrichopteraHydropsychidae

Example site data

Operationalize the Decisions Apply fuzzy set theory to expert-derived

logic train: membership functions Results expressed as membership of levels (0 to

1) Discriminant function models (Maine DEP)

Requires sizable training set of expert-assigned sites

Calibrate other index models to BCG results

Method

Method

CompletePartial / In DevelopmentPlanning

Casco Bay

Tampa Bay

NarragansettBay

ColumbiaEstuary

Caribbean Coral Reefs

Application

Lessons learned Classification is key! Struggle against taxonomic chauvinism:

bugs don’t work everywhere, fish don’t work everywhere: use taxonomically rich assemblages that can be sampled frugally

Application

Multiple Assemblages Minnesota

Calibrated BCG model for 7 classes of warmwater streams, both invertebrates and fish

Quantitative BCG model incorporated in Access application

Will be used to help set biological criteria for MN waters

Region 5 states and tribes Calibrated BCG model for cold and cool-

transitional streams, both invertebrates and fish.

Recent Developments

Considerations for estuaries

Several habitat types in an estuary – estuary health not dependent on single habitat

Legacies of overexploitation (fish, shellfish)

Ocean changes Watershed/ input changes Direct habitat disruption/conversion Effects on keystone components

Recent Developments

Recent Developments

Coral BCG Coral reef scientists new to BCG conceptual

model All have observed reef declines during their

careers Instead of numeric data, participants viewed

video transects of shallow water reefs and rated quality of each reef

Biological Condition Gradient A conceptually simple framework for holding enormous,

user-defined complexity Scale up (more general) for communication Scale down (more detailed) for research

Organizes and prioritizes research needs Uncovers gaps in knowledge Uncovers discrepancies in assessment conclusions Enables hypothesis testing

Enhances communication Independent of methods Conceptually complete scale Translates observation and measurement into shared

meaning

Summary

BCG: A Flexible ApplicationIn

dex

Sco

re

0

10

20

30

40

50

60

70

80

90

100

Reference Stressed

Exceptional

Good

Fair

Poor

Very poorNon-reference

Summary

x

x

x

Documents

The biological condition gradient: updates and opportunities