Michael Suplee, Ph.D. Montana Dept. of Environmental Quality. Prepared For: Flathead Lake Watershed Advisory Group Meeting June 17, 2013

Transcription

1 Michael Suplee, Ph.D. Montana Dept. of Environmental Quality Prepared For: Flathead Lake Watershed Advisory Group Meeting June 17, 2013

2 Review of events leading to the lake targets proposed in late 1990s Considerations for Standards Setting Lake s use-classification, Flathead Basin Commission s mission, how these affect DEQ s views on setting the lake s standards Brief overview of scientific literature pertaining to Flathead Lake What DEQ is considering proposing to BER Role of Nutrient Work Group, WPCAC, and BER

3 1970s -present: Scientific study of lake by UM s Flathead Lake Biological Station, and others, including annual measure of primary productivity 1983: Legislature creates Flathead Basin Commission. Its goal: protect the existing high quality of the Flathead Lake aquatic environment ( , MCA) : Series of meetings by TMDL team, comprising local, state, federal, and tribal agency representatives, scientists, and other stakeholders. Goal: establish lake targets Targets set in late 1990s were: Primary Productivity: 80 g C/m 2 /year No declining trend in hypolimnetic dissolved oxygen No blooms of nuisance cyanobacteria, control shoreline algae Epilimnetic chlorophyll a: 1.0 µg/l Total phosphorus (TP): 5.0 µg/l; total nitrogen (TN): 95.0 µg/l SRP: <0.5 µg/l; NO 2+3 : 30 µg-n/l; NH 3 : <1.0 µg-n/l

4 Setting Water Quality Standards is about establishing the Desired Condition for the waterbody

5 Use Class is A-1: Highest level of protection afforded a state water short of A-closed, which is for drinking water supplies Flathead Basin Commission s Goal: protect the existing high quality of the Flathead Lake aquatic environment ( , MCA). Together, indicate WQ standards should maintain and protect the lake s condition, circa mid 1980s Lake was experiencing major ecological change in mid-1980s

6 Ellis et al., Long-tem Effects of a Trophic Cascade in a Large Lake Ecosystem. Proceedings of the National Academy of Sciences USA 108: Spencer et al., Impact of Predation by Mysis relicta on Zooplankton in Flathead Lake, Montana, USA. Journal of Plankton Research 21: Spencer et al., Role of Nutrients and Zooplankton in Regulation of Phytoplankton in Flathead Lake (Montana, U.S.A.), a Large Oligotrophic Lake. Freshwater Biology 39: Tohtz, J., Lake Whitefish Diet and Growth after the Introduction of Mysis relicta to Flathead Lake, Montana. Transactions of the American Fisheries Society 122: Spencer et al., Shrimp Stocking, Salmon Collapse, and Eagle Displacement: Cascading Interactions in the Food Web of a Large Aquatic Ecosystem. BioScience 41: Dodds et al., Simultaneous Nitrogen and Phosphorus Deficiency in Natural Phytoplankton Assemblages: Theory, Empirical Evidence, and Implications for Lake Management. Lake and Reservoir Management 5:

7 Findings that Bear on Standards Setting: Arrival of opossum shrimp (Mysis relicta) in mid 1980s drastically changed the lake s foodweb Collapse of kokanee fishery, ascendance of lake trout and lake whitefish, smaller zooplankton, faster C turnover Studies after shrimp s arrival indicate N and P co-limit phytoplankton growth rate Due to foodweb changes, lake maintains higher primary productivity than before shrimp Stabilized at ~ 100 g C/m 2 /yr, up from 80 g C/m 2 /yr Interactions among fish, shrimp, zooplankton, phytoplankton and nutrients very complex Lake ecosystem appears to have entered new stable state

8 Protect the existing high quality of the Flathead Lake aquatic environment Avoid Law of Unintended Consequences Effects of allowing alteration of N:P ratios, loads, etc. not predictable; could lead to undesirable outcomes Current ecological status of lake documented Establishing standards that reflect current conditions is DEQ s best means of meeting goal Lake is now hovering near most criteria, except TN (now closer to 100 µg/l) and primary productivity If a fully integrated lake ecosystem model can be developed, criteria could be updated Potential to alter allowable N and P concentrations in and loads to the lake

9 Contain: Criteria General variance procedures Individual variances Permitting requirements Non-degradation

10 Update to 100 µg/l? Discuss Flathead Lake standards are to be monitored at the Midlake Deep site

11 Nutrient Work Group WPCAC BER EPA approval Law Rule Making Comments can be made at Nutrient Work Group meetings (next: July 9 th ), or during formal rule making in front of the Board of Environmental Review (BER)

12 Contact Information: (406) Michael Suplee (406) Eric Urban (Standards Section Chief)