MJ Paul Tetra Tech Inc. Center for Ecological Sciences RTP, NC

1. Using biological responses in nutrient criteria development: applications, opportunities, and concerns MJ Paul Tetra Tech Inc. Center for Ecological Sciences RTP, NC

2. Nutrient Pollution Impacts Biology • We can simplify the linkages • This has Clean Water Act implications

3. Nutrient Criteria Development 40 CFR § 131.11   Criteria • States must adopt water quality criteria that protect designated uses, based on science and composed of sufficient parameters; • These should be: • Numeric or; • Narrative “where numerical criteria cannot be established or to supplement numerical criteria” • Focus has been on deriving numeric nutrient criteria • How is this done? • 4 major approaches – often in a weight of evidence approach

4. Numeric Nutrient Criteria Development • Reference based – biology can be used here 90th 75th 25th

5. Numeric Nutrient Criteria Development • Stressor-response based – biology most definitely used here IBI Score Ln(TP)

6. Numeric Nutrient Criteria Development • Mechanistic Models • E.g., WASP, QUAL-2k, EFDC, CE-QUAL, HSPF, MIKE… • Model specific endpoints to generate nutrient goals

7. Numeric nutrient criteria development • Scientific Literature

8. Numeric Nutrient Criteria • Outcome – numeric value • One or more lines of evidence

9. Implementing numeric nutrient criteria • Typically criteria are implemented as they are written: • E.g., 40 ug/L annual average not to be exceeded more than 1 in 3 years • With nutrients, some states have proposed linked biological and nutrient criteria: • Or as a multimetric: Composite Criteria = Pchla+ PDO + B + N Nutrients ok Nutrients not ok Biology ok Biology not ok

10. Linked Biological and Nutrient Criteria • Why? • Lack of cause-effect • Variability of response of algae/invertebrates/water chemistry to nutrient enrichment • Cannot reliably predict a value that will produce aquatic life use impact • False positives would be costly C B A X X IBI Score X D Ln(TP)

11. Linked Biological and Nutrient Criteria Issues • If nutrient concentrations cannot predict biological response, then how can a biological response be used to infer nutrients are too high? If they can, why do you need confirmation? Does not improve with a “building the case” approach • If cannot reliably link nutrients to algae, DO and/or IBI, then how can they be combined to infer a numeric nutrient impairment? B A X D B A C X X X

12. Linked Biological and Nutrient Criteria Issues • If models are inaccurate, immediately concluding that biological impacts are due to nutrients is questionable stressor identification

13. Linked Biological and Nutrient Criteria Issues • What would such an approach open up for other criteria (e.g., priority pollutants)? • E.g., Cd limits derived to protect 5th percentile of sensitive lab species • Combine with proof of in-stream aquatic life impact?

14. Linked Biological and Nutrient Criteria Issues • Waiting for evidence of impacts on aquatic life use before acting on nutrient pollution may conflict with 131.11(a) - States must adopt water quality criteria that protect designated uses; • It is also ecologically risky… “Expectations that ecosystems will return to original conditions …following reduced nutrient inputs may be fundamentally flawed….”

15. Solutions • Reduce the variability – a big part of our problem may be classification… • Accept and apply risk based reasoning • Derive numbers based on reducing the risk of impacts, not on being 100% correct; • Existing water quality criteria are very precautionary Classification Ecology

16. Solutions • Incorporate the variability into the criteria setting step, not the assessment step • If response conditions are fine and nutrients elevated (within an acceptable range), then refine numeric nutrient criterion site-specifically • Such an approach protects existing biological condition from nutrients rather than requiring proof of impact before action

17. Solutions • Incorporate measures with safety levels – range concept • Reference based values = lower trigger • Stressor-response based values (invertebrate/fish) = upper values • But, use biological measures EARLY in the causal pathway Listed for Nutrients Listed for Nutrients Listed for Nutrients Yes Biological Threshold Exceeded Not Listed Not Listed SSC Listed for Nutrients No Low High No Yes Yes Nutrient Threshold Exceeded

18. Solutions • Incorporate early warning measures for bio-confirmation

19. Solutions

20. Solutions • Require proof on multiple biological endpoints • If nutrients elevated, but chlorophyll is not; then you need to confirm that all aspects of aquatic life are okay. • Nutrients can affect many aspects of aquatic life in streams (even shaded headwaters): • Algae • Invertebrates • Fish • Bacteria • Fungi • Function

21. Solutions • This discussion is all VERY good for biology • Whichever way it goes • Bio-confirmation or No (Focus on ALU) • Support technical research • Fund more experimental work • Field and lab dosing experiments • Develop and apply statistical approaches for reducing variability • Develop new and refine existing biological response tools • Ask experts what they think

22. Thanks Huffy The Bug Slayer