Tiered Aquatic Life Use Model

Tiered Aquatic Life Use Model

Christy Pickens, Physical Research Scientist

Water Quality Control Division

Colorado Dept. of Public Health and Environment

30 July 2003

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Purpose of Model

• The tiered aquatic life use framework is a conceptual model predicting the response of aquatic communities to increasing human disturbance.

• The conceptual model is a draft framework for using biological assessment information to refine designated aquatic life uses.


Purpose of Model

EPA developed the TALU model for a nationally consistent approach.

• Scientifically defensible benchmarks• Common framework for communication and

evaluation- public, stakeholders, across political boundaries

• Protection for excellent quality waters• Achievable goals for incremental restoration


Purpose of Model

National ALUS Workgroup • Biological Condition Gradient (BCG)

focus of workgroup in 2001.• Human Disturbance Gradient (HDG)

focus of workgroup in 2002.• Workgroup recommendations going

forward to EPA this spring with the conceptual models, implementation options, case examples.


TALU Model Basics

Bioassessments help states develop expectations for acceptable biological conditions. This is accomplished through the technical process of developing aquatic life goals, aquatic life uses (ALUs). Biological assessments allow various levels of ALUs. Using several types, or tiers, of ALUs allows states and tribes to allocate limited resources to waterbodies in proportion to their need for protection.


ALUS Integrity

ALUS is determined by assessing:

• Response variable (biological condition) to determine impairments and full support

• Stressors (physical and chemical conditions) to determine impairment


TALU Conceptual Model


TALU Model Basics

The tiered system of use designations provides for different levels of protection and reflects the choices implicit in reconciling the “ideal” (represented by least impacted reference conditions) with the “reality”, the ongoing effects of two centuries of intensive human use of the state’s land and water resources.


TALU Model Basics

Key Points to Emphasize:

• Framework is conceptual• Number of tiers to be determined by

State• “Best Fit” approach recommended• The framework may be quantitatively

defined by many possible methods• BCG is a quality gradient, not a

classification


TALU Model Basics

• Human Disturbance Gradient

(HDG)

• Biological Condition Gradient

(BCG)


TALU Model Basics


TALU Model Basics


TALU Model Basics

Human Disturbance Gradient


TALU Model BasicsHDG Layout

Six tiers (A-F)

Six major stressor classes• Habitat Structure• Flow Regime• Water Quality• Toxics and Bioengineered Chemicals• Energy Sources• Biotic Interactions


TALU Model BasicsHDG Layout

Six major disturbance classes• Landscape Character• Riparian Condition• Barriers• Channel Morphology (map scale)• Atmospheric Deposition• Biotic Interactions


TALU Model BasicsHDG Rationale

• Essential for determining reference sites and minimal disturbance

• Necessary for metric and index development and evaluation

• Often represents half the variability in biological response scores

• Easier to assess than large suite of stressors• Assists in diagnosing stressors• Source of most manageable stressors• Critical for stream protection, BMPs and

restoration


TALU Model Basics

Draft Model Tiers – 6 levels

1. Natural structure and function of biotic community maintained

2. Minimal changes in structure and function

3. Evident changes in structure and minimal changes in function

4. Moderate changes in structure and minimal changes in function

5. Major changes in structure and moderate changes in function

6. Severe changes in structure and function






HDG Concepts

Human disturbance gradient does not necessarily imply degradation.

Human disturbance gradient addresses two basic questions:

What is the departure from expected condition as a result from human activities?

What is the impact of this departure from expected condition on the biotic community?


TALU Model Basics

Biological Condition Gradient


TALU Model Basics


TALU Model Basics

Biological Condition Gradient (BCG)

BCG is a quality gradient, with the upper end of the scale reflecting “natural conditions” corresponding with the CWA integrity objective.

BCG is not a model to be used for classification of natural systems, such as ecoregions. BCG would only be applied once they have been appropriately classified.

BCG provides consistency among states using different approaches.


TALU Model Basics

Biological Condition Gradient (BCG)

The first tier of the model characterizes the natural expectations for a waterbody unimpacted or minimally impacted by human activities. The subsequent tiers show the response of the biological community to increasing human disturbance.


TALU Model Basics

BCG Layout10 Major Attributes• Taxonomic composition and tolerance

– Attributes I-V– Regionally Endemic through Tolerant

• Non-Native taxa– Attribute VI

• Organism condition– Attribute VII

• Ecosystem function– Attribute VI

• Physical-biotic interactions– Attributes IX-X


BCG Attributes

Overview of AttributesOverview of Attributes I I -- Historically documented, sensitive, long-

lived, regionally endemic taxa documented presence prior to CWAdocumented presence prior to CWA

unique life history requirementsunique life history requirements

may be a listed RTE or Special Concern speciesmay be a listed RTE or Special Concern species

ex: ex: Brook Floater mussel; Apache trout; steelheadBrook Floater mussel; Apache trout; steelhead

II II -- Sensitive - rare or specialist taxa may require special habitats;may require special habitats;

intolerant of disturbance in environmental conditionsintolerant of disturbance in environmental conditions

naturally low densities; naturally low densities;

commonly kcommonly k--strategists (slow development, longer lifespan, stable strategists (slow development, longer lifespan, stable population density over time)population density over time)

ex: ex: TaeniopteryxTaeniopteryx; slimy ; slimy sculpinsculpin, bull trout; plains , bull trout; plains killifishkillifish


BCG Attributes

Overview of Attributes (cont.)Overview of Attributes (cont.) III III -- Sensitive - ubiquitous taxa

ordinarily common and abundantordinarily common and abundant

broader range of thermal and habitat tolerance; mild broader range of thermal and habitat tolerance; mild pollution loads have a negative effect on populations;pollution loads have a negative effect on populations;

ex: ex: AcroneuriaAcroneuria; ; BaetidaeBaetidae; ; EphemerellidaeEphemerellidae; brook ; brook trout; black trout; black redhorseredhorse

IV IV -- Taxa of intermediate tolerance may have generalist feeding strategies may have generalist feeding strategies

densities commonly increase in response to nutrient densities commonly increase in response to nutrient enrichmentenrichment

may be rmay be r--strategists (early colonizers with rapid turnover strategists (early colonizers with rapid turnover times and boom/bust populations)times and boom/bust populations)

ex: ex: HydropsychidaeHydropsychidae; ; PolycentropodidaePolycentropodidae; common ; common shiner; mooneye; Rio Grande suckershiner; mooneye; Rio Grande sucker


BCG Attributes

Overview of Attributes (cont.)Overview of Attributes (cont.) V V -- Tolerant taxa

often tolerant of a broad range of environmental often tolerant of a broad range of environmental conditionsconditions

often roften r--strategists or opportunist strategists or opportunist taxataxa; densities may ; densities may increase greatly in absence of competition and predationincrease greatly in absence of competition and predation

ex: ex: leeches; gastropods; white sucker; green sunfishleeches; gastropods; white sucker; green sunfish

VI VI -- Non-native taxa

species that do not naturally occur in a given locale or species that do not naturally occur in a given locale or ecosystem ecosystem

ex: ex: CorbiculaCorbicula; zebra mussels; ; zebra mussels; ruddrudd

VII VII -- Organism condition

DELT anomalies and parasites of fish;DELT anomalies and parasites of fish;

evidence of reproduction; sex ratios; biomass of YOYevidence of reproduction; sex ratios; biomass of YOY


BCG Attributes

Overview of Attributes (cont.)Overview of Attributes (cont.)

VIII - Ecosystem Function processes required for normal performance of a processes required for normal performance of a

biological systembiological system

may be applied to any level of biological organizationmay be applied to any level of biological organization

Not commonly measured directly by state/tribal Not commonly measured directly by state/tribal programsprograms

ExamplesExamples:: IndividualIndividual-- % organisms with …(anomalies, disease, % organisms with …(anomalies, disease,

parasites, etc.)parasites, etc.)

PopulationPopulation-- fecundity, age class distributions, sex ratios, fecundity, age class distributions, sex ratios, presence/absencepresence/absence

CommunityCommunity-- structural composition and complexitystructural composition and complexity

EcosystemEcosystem-- Primary and secondary production, P/R, Primary and secondary production, P/R, immigration and emigration, immigration and emigration, trophic trophic complexity, resource complexity, resource leakageleakage


BCG Attributes

March 31 – April 4, 2003 National Biological Assessment and Criteria Workshop, TALU101_05 21

Overview of Attributes (cont.)Overview of Attributes (cont.)

IX- Spatial and temporal extent of detrimental effects and X- Ecosystem connectance physical:biological interactions

Cross-cutting attributes

Provides linkage to the “Human Disturbance Gradient”

Expands the interpretation to larger spatio-temporal scales

Informs the management perspective

(e.g., prioritization)


BCG AttributesB

iolo

gic

al

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Stressor GradientLow High

1 Native or natural condition

2 Minimal loss of species; some density changes may occur

3Some replacement of sensitive-rare species; functions fully maintained

4

Some sensitive species maintained but notable replacement by more tolerant taxa; altered distributions; functions largely maintained

5

6

Tolerant species show increasing dominance; sensitive species are rare; functions altered

Severe alteration of structure and function

Natural

Degraded


BCG Attributes EX

33www.brainybetty.com

Susan P. Davies, MDEP

11 22 33 44 55 66

ALUS Tiers Provide Consistency

a b c d e fNatural Degraded


TALU Model

Thinking ahead…

How can we transition from describing what we see to establishing thresholds?

Bio

logi

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Con

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Designated Aquatic Life Uses in Vermont

Not meeting CWA 101a uses for protection & propagation of aquatic life

Human Disturbance

natural/minimally altered

Low High

Class B1: Very Good - Minor changes to structure and function; tolerant/intolerant forms within the range of reference condition.

Class B2/3: Good - Moderate changes in the relative proportions of tolerant, intolerant, taxonomic and functional components.

Class A1: Excellent - Biota within the range of the natural condition

Non-Support: Fair-Very Poorhighly altered

1

2

3

4

5

6 Bio

cond

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radi

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Threshold criterion A1

Threshold criterion B1

Threshold criterion B2/3

Documents

Tiered Aquatic Life Use Model