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.
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
Moderate changes in structure & minimal changes in function
Major changes in structure & moderate changes in function
Severe changes in structure & function
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
Biological Condition
The Biological Condition Gradient
NaturalVariability
- - No Effect - -
Minimal changes in structure & function
Evident changes in structure and minimal changes in function
Major changes in structure & moderate changes in function
Severe changes in structure & function
Natural structure and function of biotic community maintained
Moderate changes in structure & minimal changes in function
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
Attributes: New England FishMethod
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
Attributes: New England FishMethod
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
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