The Impact of Excess Phosphorus on Minnesota s Lakes and Rivers presented at SERA 17 November 2015

Transcription

1 The Impact of Excess Phosphorus on Minnesota s Lakes and Rivers presented at SERA 17 November 2015 Steven Heiskary Research Scientist III Environmental Analysis and Outcomes Division

2 Overview 1. Minnesota geographic & lake patterns 2. P Impacts on lakes 3. Development of lake phosphorus water quality standards (WQS) 4. P Impacts to rivers 5. Development of river phosphorus WQS 6. Summary

3 Impact of P on lakes has been firmly established for decades e.g. Experimental Lakes Area Canada ELA Lake & 1994 ELA Lake 226 c 1973

4 Eutrophication & Lake Assessment Since mid 1980s MPCA routinely monitored & assessed lake status for Clean Water Act 305(b) report to Congress; Conducted detailed assessments of 100 s of lakes, Wide range of research and numerous publications on this work; After almost two decades of work (c ) MN promulgated lake eutrophication (nutrient) WQS in 2008 (in support of CWA);

5 Minnesota exhibits distinct patterns in geomorphology, soils, potential natural vegetation & land use hence ecoregion approach. Lake condition varies regionally.

6 Sediment cores as a basis for assessing change over time & regional patterns Diatom-inferred TP: Pre-European vs. Modern-day TP ppb NLF (n=20) CHF-Metro (n=20) CHF-Rural (n=15) CHF- Shallow (n=5) WCP - Deep (n=5) WCP/NGP - Shallow (n=6) Pre-E Modern

7 Shaokotan a prairie lake in SW MN with long history of monitoring, excessive P loading & BMP implementation.

8 Shaokotan responds to decreased TP input; 2013 TP decreased but yet blue green dominated TP declined further 2014 & 2015, algal levels low, clarity increased, rooted vegetation present across the lake

9

10 Harmful algal blooms (blue green algae) Principal drivers: high phosphorus warm water >75 80 F calm sunny conditions

11 HAB toxin production & concerns Three classes of toxins (all highly toxic) Hepatotoxins (liver) Neurotoxins (nervous system) Dermatoxins (skin) In MN reports of dog deaths & illness occur each summer, e.g. 3 in 2015, 5 in 2007; Human illness gasterointestinal, rash and allergic reactions common response to contact with toxins; One case of youth hospitalized after contact with HAB in 2015.

12 Fish species vary relative to lake trophic status (Carlson s TSI) As TP increases across this gradient, fishery composition changes Based on work of Dennis Schupp & paper by Schupp & Wilson 1993

13 Lake Eutrophication Standards: Use to assess lake condition in MN for Clean Water Act 303(d)

14 Excess nutrients impact rivers too Blue Earth River Watonwan River Pipestone Creek Minnesota River 14

15 P impacts more subtle in rivers & there was a need to establish linkages in support of WQS Bacteria Phosphorus Suspended Algae BOD Daily DO Flux Conceptual model influenced extensive studies & statistical analysis, which led to river WQS Biological Condition 15

16 River Eutrophication WQS: 2014 in MN Rule Region Total Phosphorus ppb Chlorophyll ppb Response criteria DO flux ppm BOD 5 ppm North Central South Includes causative criteria: summer mean TP and 3 response criteria If TP and one or more response variables is exceeded, WQS is violated (river reach impaired) 16

17 2014 Lake Assessment a. 1,859 fully assessed (using lake WQS), b. 29% impaired & placed on 303(d) list; c.~573 lakes listed as impaired; d. Of these: 263 (46%) have a NPDES discharge in their watershed

18 Stream status (~c2013) Assessments relative to river WQS underway

19 Summary There is no dispute on the impact of excess P on lakes and rivers in MN & elsewhere for that matter; Excess P in lakes & rivers yields excessive growth of algae that negatively impacts recreational use, aesthetics and aquatic life; Blue greens are the most common bloom forming algae many of which produce toxins, a world wide concern; MN has done extensive monitoring & assessment of its surface waters and has developed eutrophication standards for both lakes and rivers. Excess P arises from regulated & un regulated sources and all must be addressed to improve water quality

20 Questions?