RESPONSE TO NUTRIENT LOAD REDUCTIONS IN A TEMPERATE ESTUARY

1. RESPONSE TO NUTRIENT LOAD REDUCTIONS IN A TEMPERATE ESTUARY Jason Krumholz, Candace Oviatt, Leslie Smith NEERS 4/13/2012

2. Talk Layout • Introduction and Background • How have inputs to the Bay changed? • How does this impact the standing stocks? • Do we see changes in biology? • What does it mean/Why do we care?

3. Narragansett Bay • 380 km2 surface area-Watershed is ~ 4250 km2 • Dominant circulation pattern is tidally driven • Watershed is home to 2 million people- very dense. • 65% of 2003 Nitrogen loading from sewage (Nixon et al. 2008) • Management intervention • (Brief) Survey Description

4. Why Do We Care About Nutrients? Lower Nutrients Less Chlorophyll Less Settling Organic Matter Less Benthic O2 Demand Less Hypoxia

5. Spatial Patterns Average of annual average concentrations (2006-2010)

6. DIN/DIP ratio <16:1 is traditionally viewed as a nitrogen limited system. • On an annual average basis, Narragansett Bay remains nitrogen limited throughout, though this limitation is more severe in the mid and lower bay. • On shorter time scales, some areas of the Upper Bay do show evidence of P limitation, which may become even more important as N inputs continue to drop. Average of annual average concentrations (2006-2010)

8. *= P<0.05 **= P<0.01 ** * ** * * **

9. Is there a change driven by the reduction?

10. Long term Chlorophyll

11. Kolmogorov-smirnov (KS) distribution

12. sUMMARY • Recent management efforts to reduce nitrogen loading have resulted in an approximately 1:1 reduction in standing stock. • Phosphorus loads are already 30-50% less than peak levels. • WWTF & non-point sources • May become more important to biology, especially in upper bay. • At present, no or minimal biological response to the loading reductions can be detected. • Future reductions may be large enough to elicit some biological response Adapted from Oviatt et al. 1986

13. acknoqwledgements Rossie Ennis Leslie Smith Scott Nixon Angelo Liberti Steve Granger Ashley Bertrand Catherine Walker Brooke Longval Christine Comeau Danielle Dionne Jamie Vaudrey Conor McManus Chris Melrose & NOAA/DEM Shuttle Team Funding Support: NOAA CHRP - Libby Jewett & Alan Lewitus, Project Officers NOAA Bay Window – Sarah Pike, Project Officer References Oviatt, C. (1980). Some aspects of water quality in and pollution sources to the Providence River. In R. Pastore, Report for Region 1 EPA. September 1979-September 1980. Boston, MA: United States Environmental Protection Agency. Oviatt, C., Keller, A., & Reed, L. (2002) Annual primary production in Narragansett Bay with no bay-wide winter-spring phytoplankton bloom. Estuarine Coastal and Shelf Science, 54, 1013-1026. Nixon, S.W., Buckley, B.A., Granger, S.L., Harris, L.A., Oczkowski, A.J., Fulweiler, R.W., & Cole, L.W. (2008). Nitrogen and Phosphorus Inputs to Narragansett Bay: Past, Present, and Future. In B. Costa-Pierce, & A. Desbonnet, Science for Ecosystem-based Management (pp. 101-175). New York: Springer. Kremer, J. N., J. M. P. Vaudrey, D. S. Ullman, D. L. Bergondo, N. LaSota, C. Kincaid, D. L. Codiga, and M. J. Brush. 2010. Simulating property exchange in estuarine ecosystem models at ecologically appropriate scales. Ecological Modelling221:1080-1088.

14. NET EXPORT 451 NET EXPORT 283

15. P>0.001

21. Phase 1: Operational 11/2008 Phase 2: 2009-2013 Phase 3: 2015-2021

22. General Form: Nd=N0e-kd 1:1 1:1

24. Sound to Bay Phosphate flux 2006

27. Intercept: NS Slope: NS

28. * indicates facilities that do not have annual data. a Average and standard deviation values are for 2007-2010 to avoid averaging over upgrade completion. b Average nitrogen and phosphorus load values are 2010 load values as this is the only year of data available after upgrades were completed. c Average and standard deviation values are for 2009-2010 to avoid averaging over upgrade completion. d Average DIP load values for the Field’s Point, Bucklin Point, and East Providence facilities were calculated using the ratio between DIP and TP values from earlier measurements (Nixon, et al., 1995). The ratio between DIP and TP for the remaining facilities was calculated by taking the average of the DIP to TP ratios of the Field’s Point, Bucklin Point, and East Providence facilities. Average DIP load values for the remaining facilities were calculated using this average ratio.

32. Sources of nutrients to the bay

34. * indicates facilities that do not have annual data. a Average and standard deviation values are for 2007-2010 to avoid averaging over upgrade completion. b Average nitrogen and phosphorus load values are 2010 load values as this is the only year of data available after upgrades were completed. c Average and standard deviation values are for 2009-2010 to avoid averaging over upgrade completion. d Average DIP load values for the Field’s Point, Bucklin Point, and East Providence facilities were calculated using the ratio between DIP and TP values from earlier measurements (Nixon, et al., 1995). The ratio between DIP and TP for the remaining facilities was calculated by taking the average of the DIP to TP ratios of the Field’s Point, Bucklin Point, and East Providence facilities. Average DIP load values for the remaining facilities were calculated using this average ratio.

37. Sound to Bay Phosphate flux 2006