Suzanne Faubl MESM Program, University of Rhode Island RINHS Annual Conference April 25, 2011

1. Phosphorus Dynamics, Cyanobacteria and Wildlife Values at Trustom Pond:A Management-Oriented Water Quality Investigation Suzanne Faubl MESM Program, University of Rhode Island RINHS Annual Conference April 25, 2011

2. Trustom Pond Location in Coastal Pond Region

3. Overview of Trustom Pond Setting and History • Managed for agricultural production previously • Rapid development in region beginning in 1940-50s • Acquired by FWS in 1974 • Co-dominated by widgeon grass and sago pondweed during 1978 veg survey • Estuarine conditions through early 2000s (due to breaching)

4. Threats to Salt Ponds Often Associated with Development • Individual septic disposal systems (ISDS) contribute nitrate to water table • Road runoff (salts, petrochemicals, phosphates, fertilizer) development in coastal pond watershed increased from 2,821 houses in 1949 to 14,691 houses in 2003

5. But… Trustom is its Own Pond • US FWS property • Maintained to optimize wildlife values • Critical habitat for rare and endangered birds • Swimming and boating prohibited • Undeveloped shoreline Source: US Fish & Wildlife Service

6. Trustom Pond Surface Watershed Dominated by Undeveloped Land

7. Trustom Pond Watershed Has Low Impermeable Surface Area (~ 2%) IMPERVIOUS COVER SHOULD HAVE LIMITED EFFECT ON WATER QUALITY AT TRUSTOM

8. Despite Protection,Trustom Experiences Water Quality Issues Blue-green algal bloom Trustom Pond, 10/13/2010 Blue-green algae bloom Trustom Pond, 10/20/2010

9. Water Management Goals for Trustom Pond • Provide high-quality habitat for waterfowl • Maintain sufficient high-quality food sources • Control invasive and/or low value plant species • Minimize disturbance to vulnerable populations (e.g., nesting birds) Photo credit: Rick Newton

10. Objectives of This Study • Document key water quality parameters • Characterize nutrient status, sources, dynamics • (2) Evaluate algal population • (3) Recommend management and monitoring processes

11. Water Quality Parameters Monitored Monthly at Trustom Pond • Phosphorus (P), total and dissolved • Nitrogen (N), total, nitrate and ammonia • Bacteria (fecal coliform & enterococci) • pH Samples from two sites in basin and two tributaries upgradient

12. Approaches Used • Field monitoring (Jun 16 – Oct 29, 2010) • Determine limiting nutrient (P vs N) • Calculate phosphorus loading from land use • Estimate waterfowl nutrient contribution • Characterize role ofsediment in nutrient cycle

13. Changes in Trustom Pond Due to Cessation of Forced Breaching • Breached regularly until FWS stopped in ~2006 • Evolution from estuarine (~15 ppt ) to fresh water habitat (0.2 ppt) • Dominated by Najas flexilis (freshwater species) • Higher SAV diversity at Trustom than in other (breached) RI coastal ponds Najas flexilis (water nymph) Source: USDA

14. Water Quality Parameters Monitored Weekly at Trustom Pond (17 sample dates) • Secchi depth (clarity) 264 readings total • Chlorophyll-a296 samples analyzed • Dissolved oxygen 252 readings total • Temperature 124 readings total • Total dissolved solids (TDS / salinity) collected from 5 sampling sites in pond

15. Results: Temperature and Dissolved Oxygen • Average DO ~7.5 mg/L (minimum of 5 mg/L recommended) • All values > 5.0 except one reading (3.9) at Otter Point on 10/13 • DO and T at surface and one meter nearly identical • WELL MIXED • ADEQUATE OXYGEN

16. Results: Water Clarity • Clarity generally decreasing through July • Increasing from August through September • Depths of < 1 meter on 29% and 41% of dates at Otter and Osprey Points • Low clarity coincided with high chlorophyll-a • Secchi depth is good indicator of algae in the water column at Trustom

17. Results: Chlorophyll–a and Secchi Depth

18. Results: Total Phosphorus TOTAL P > 24 INDICATES EUTROPHIC CONDITIONS NOTE: US EPA and RIDEM use a target of 25 ppb P for some shallow ponds

20. Results: Nitrogen to Phosphorus Ratio • N:P ratio for Trustom ranged from 19-26 • N:P ratio > 16 indicates P-limited • RI coastal ponds tend to be N-limited due to marine influence • Recommendations for salt pond management assume N-limitation

21. Results: Chlorophyll–a (Algal Biomass) • Trends consistent with NE phytoplankton succession • Green algae appeared to dominate in July • Blue-green algae blooms visible in Sept - Oct • Elevated values coincided with low Secchi depths Source: Water on the Web, 2004

22. Results: Chlorophyll–a (Algal Biomass)

24. Results: Fecal Coliform • RIDEM allows maximum of 14 for shellfish waters • Tributaries may show influence of wildlife, manure fertilizers, human impacts in watershed • Enterococci in pond was below RIDOH limit for swimming

25. Results: Fecal Coliform • Not harmful to birds • High level in October coincides with influx of migratory waterfowl • Evidence waterfowl are an important nutrient vector • High concentration of waterfowl at Trustom is a cultural impact Source: U.S. Fish & Wildlife

26. Is Cultural Eutrophication a Threat to Management Goals of Trustom Pond? Eutrophication tends to enhance growth of invasive species and inhibit native and sensitive species P not dangerous itself, but contributes to HABs, which can degrade habitat and harm wildlife Trustom Pond surface during BG algal bloom October 2010 Chlorophyll-asample from Trustom bloom October 13, 2010

27. Blue-green Algae Detected in Trustom are Potential HAB-forming Types samples collected from Aug 4 – Oct 20 were analyzed by UVM microarray facility; the genus Anabaena dominated two HABs detected at Trustom in October 2010

29. Microcystis Detected Under Microscope in July Microcystis, under fluorescence Microcystis, phase contrast photos by Lucie Maranda, GSO

30. Phosphorus Dynamics in Watershed and Basin • Immobile in groundwater • Sediments delivered by overland flow • Waterfowl deposition • Accumulates in the pond sediment • Recycles through mixing or under anoxic conditions • Equilibrium

31. Large Waterfowl are an Important Vector for Nutrients Canada geese and mute swans produce ~ 1.5 grams of P per day May feed outside the pond – result is net import of nutrients Mute swans remain in pond during molting (August) – 100% deposition Highest total and dissolved P levels detected in August Elevated fecal coliforms in October correspond with influx of migrants

32. P Loading from Waterfowl Appears Comparable to Watershed Inputs • Data: intermittent FWS bird counts • Estimated a range of values based on migratory counts and year-round residents NOTE: These are best guess estimates; actual loading depends on a complex set of variables beyond the scope of this study.

33. P Loading from the Watershed • Cropland largest source of the watershed • Soil and fertilizer management practices and precipitation will drive loading rate

34. Controlling Phosphorus Inputs From Agricultural Lands • USDA recommends trapping phosphorus in upland buffers • Sequester P beyond flood plain • Unfertilized, high-nutrient demand plants are best Source: USDA http://www.unl.edu/nac/bufferguidelines/

35. Watershed Management Can Help Protect Water Quality • Maintaining dense native vegetation throughout watershed and near pond is a best practice • Prevents soil erosion • Traps phosphorus • Promotes rapid infiltration • Reduces export of pollutants • Discourages large waterfowl from assembling on pond shore

36. Sediment in Trustom Pond Functions as Both Sink and Source for P • Sediment equilibrating with pond water (P ~ 6 ppb) released P into the water column (SOURCE) • At higher P concentrations, sediment removed P from the water column (SINK) • Dissolved P in pond ranged from 6 – 14 ppb • UNCLEAR if sediment is contributing P to water column– try extending P analysis through dormant periods

37. Potential Obstacles to Achieving Water Management Goals • Can we determine a threshold carrying capacity for wildfowl populations? • Lack of control over activities within the watershed but beyond FWS jurisdiction • Difficult to predict when and where HABs will occur • Implementing control measures can disturb wildlife

38. Expanding Waterfowl Survey Can Help Determine Carrying Capacity • More than 50% of annual P load from birds may be added during migration. Loading rate is influenced by: • Counts • Species • Behavior • Diet • Empirical evidence suggests bird droppings do not affect water chemistry immediately, so need to track changes over several years

39. Difficult to Predict Impact of Breaching on Trustom Pond Habitat Values • Significant water exchange needed to export nutrients • Tidal exchange causes increased salinity • Higher ionic strength of salt water may increase rate of P desorption from sediment (and increase P in water column) • Change in salinity may affect SAV dominance

40. Recommendations • Reduce nutrient inputs from land wherever possible • Survey watershed regularly for potential nutrient hot spots • Use LID for all construction • Track waterfowl use • Be alert for HAB poisoning • Samples water during HABs for more extensive analysis • Do not implement breaching without an expert study of breach hydrodynamics

41. Acknowledgements UF F&WS Erin King and Rhonda Smith Suzanne Paton and Dorie Stolley - the great FWS interns! Kevin, Lou, Mark and Matt URI Watershed Watch Linda green and Elizabeth Herron - more terrific interns! Amanda, Casey, Siobhan other uri people Art Gold, professor of watershed hydrology Kelly Addy, researcher, watershed hydrology lab, nrs Lucie Maranda, marine research scientist, gso UVM Microarray Facility My email is: sfaubl@my.uri.edu

42. Results: Temperature and Dissolved Oxygen

43. results: total nitrogen

44. results: nitrogen-phosphorus ratio EPA recommended limit for P in lakes: 25 ppb EPA recommended limit for N in lakes: 320 ppb

45. Trophic Status Index (TSI) indicates EUTROPHIC based on total phosphorus, Secchi depth, chlorophyll-a

46. trustom pond watershed

47. MANAGE model for estimating P loading from the watershed