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Water Quality Monitoring Program and Baseline Results

Water Quality Monitoring Program and Baseline Results. OMSAP Technical Meeting September 22, 1999 Carlton D. Hunt & P. Scott Libby Battelle Duxbury Operations Duxbury, MA 02332. Acknowledgements.

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Water Quality Monitoring Program and Baseline Results

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  1. Water Quality Monitoring Program and Baseline Results OMSAP Technical Meeting September 22, 1999 Carlton D. Hunt & P. Scott Libby Battelle Duxbury Operations Duxbury, MA 02332

  2. Acknowledgements • Numerous scientists, regulators, and citizens from the New England area have contributed to the design, implementation, interpretation and understanding of water quality in the Massachusetts Bay system • Siting studies • Research • Monitoring • Products of this work are included in over 20 major water quality reports available from MWRA at http://www.mwra.state.ma.us/harbor/enquad/trlist.htmand numerous peer reviewed publications

  3. Concerns Inflow Outflow Human Health Contaminants Bacteria Viruses Bioaccumulation Ecological Nutrients Contaminants Organic Material Food Chain Community Structure Living Resources ATMOSPHERE Light GasExchange WATER COLUMN N2, |O2, CO2 Mammals Planktivorous Fish Sources Rivers Boundary Nonpoint Effluents Piscivorous Fish Phytoplankton Dissolved Zooplankton Demersal Fish Microbes Particulate Detritus Regeneration Epibenthos Microbes N, P, Si, O2, CO2 SEDIMENT Infauna

  4. Presentation Summary • Overview • Water Quality Monitoring Program • Major Baseline Characteristics • Spatial and Temporal Responses • Nutrients • Chlorophyll • Dissolved Oxygen • Plankton • Thresholds • Future expectations

  5. Water Quality Monitoring Introduction WQ monitoring program objectives are to determine if changes occur in the nearfield (local) or farfield (regional) to • Nutrients, dissolved oxygen, or phytoplankton biomass • Phytoplankton and zooplankton community composition in the nearfield and farfield occur • Phytoplankton production rates in the water column near the outfall and outer Boston Harbor

  6. Water Quality Monitoring Overview • Nutrients, chlorophyll, and dissolved oxygen • Harbor signatures and gradients in Mass Bay • Plankton communities • Thresholds and detection of change • Expectations of conditions after the outfall begins discharging at the Massachusetts Bay location This presentation focuses on spatial and temporal responses in the following areas

  7. MWRA Monitors 21 Nearfield and 28 Farfield Water Quality Stations in Massachusetts Bay Water Quality Measurement Program

  8. Water Quality Monitoring Vertical profiles • Continuous vertical hydrographic profiles to within 5 m of the bottom • Temperature • Salinity • Dissolved oxygen • Chlorophyll fluorescence • Beam attenuation (particles) • Irradiance (light) • Discrete samples from 3 or 5 depths (depending on water depth)

  9. Water Quality Monitoring Parameters Measured

  10. Water Quality Monitoring Parameters Measured

  11. Water Quality Monitoring Data evaluation Response to weather (wind and rain) Light fields Hydrographic Plankton responses Primary production Nutrients Chlorophyll biomass Species composition Nuisance species Phytoplankton Zooplankton Species composition Dissolved Oxygen Production /Respiration To understand spatial and temporal trends and causal relationships

  12. Water Quality Baseline Characteristics • Gradients (nutrients, biomass, and dissolved oxygen) • Temporal • Offshore • Vertical • Tidal exchange and export from Boston Harbor • Plankton Communities • Phytoplankton • Zooplankton

  13. Water Quality Gradients • Gradients in the system are examined using • horizontal contours • vertical sections • temporal plots • individual stations • regions in the Bay

  14. Water Quality Horizontal Gradients • The gradient offshore of Boston Harbor and along the shore from the Harbor to Plymouth is a persistent feature in the surface waters under the present discharge regime.

  15. Water Quality Temporal Responses Nitrate

  16. Water Quality Temporal Responses Silicate

  17. Water Quality Horizontal GradientsSurface Salinity

  18. Water Quality Horizontal GradientsJune 1998 Storm Response Surface Salinity

  19. Water Quality Horizontal GradientsSurface Temperature

  20. Water Quality Horizontal GradientsSurface DIN

  21. Water Quality Horizontal GradientsSurface Silicate

  22. Water Quality Horizontal GradientsSurface Chlorophyll

  23. Water Quality Horizontal GradientsBottom Dissolved Oxygen

  24. Water Quality Horizontal GradientsSurface Ammonia

  25. Water Quality Harbor Gradient after Secondary Treatment - NH4

  26. Water Quality Harbor Gradient after secondary treatment - NH4

  27. Water Quality Vertical GradientsBoston to GOM Transect - Salinity

  28. Water Quality Vertical GradientsBoston to GOM Transect - Temperature

  29. Water Quality Vertical GradientsBoston to GOM Transect - DIN

  30. Water Quality Vertical GradientsBoston to GOM Transect - Silicate

  31. Water Quality Vertical GradientsBoston to GOM Transect - Chlorophyll

  32. Water Quality Vertical GradientsBoston to GOM Transect - Dissolved Oxygen

  33. Water Quality Summary Vertical & Horizontal Gradients Water column is well mixed over the winter Increasing temperature and runoff in early spring initiates stratification Spring/summer temperature differences intensify stratification Stratification remains until fall overturn (due to lower vertical temp gradient and increased storm activity) Return to winter conditions in early winter

  34. Water Quality Summary Vertical & Horizontal Gradients • Boston Harbor is localized source of nutrients • Sewage effluent comprises 90% of the land source nutrients added to Boston Harbor (Kelly 1997) • Strong inshore/offshore nutrient gradient away from Harbor in surface waters • Gradients are less distinct in the bottom waters • Seasonal nutrients cycle (stratification) • Upwelling and winds may be a factor in bringing nutrients to surface waters in the summer

  35. Water Quality Harbor/Nearfield Exchange A strong physical front is evident off the mouth of Boston Harbor Front analysis

  36. Water Quality Harbor/Nearfield Exchange outfall outfall

  37. Water Quality Harbor/Nearfield Exchange

  38. Water Quality Harbor/Nearfield Exchange From Kelly 1997 0.6 - 0.8 N2 23-25 TN (11-12 DIN) 6.6 TN (4.5 DIN) ~15 TN (5.2-6.6 DIN) 0.2 TN 1.7 DIN Units are in 105 kmols/yr Baseline Period Post-Discharge Period <0.6 - 0.8 N2 Freshwater 0.8 TN 12-16 TN (2.5-3.9 DIN) Ocean exchange 100% of the nutrients from the Deer Island outfall will be exported into Massachusetts Bay in the future <0.2 TN <1.7 DIN Ocean exchange dominates the nutrients mass balance in Boston Harbor 85% of the nutrients from the Deer Island outfall are currently exported into Massachusetts Bay

  39. Water Quality Summary Harbor Exchange • Effluent from Deer Island outfall presently enters Massachusetts Bay • Exchange of Boston Harbor waters with nearfield and coastal waters results in a plume of Harbor water extending southward along the coast in western Massachusetts Bay • Harbor plume is primarily in the western nearfield surface waters and coastal waters to the south

  40. Water Quality Regional Responses • Stations in six regions are examined for temporal and spatial responses • Boston Harbor • Coastal • Nearfield • Cape Cod Bay • Boundary with Gulf of Maine • Offshore (south and east of the nearfield)

  41. Water Quality Chlorophyll • An indicator of phytoplankton biomass • Key measurement and indicator in the water quality program • Temporal and regional distribution are variable • Responds to light and nutrient fields (see Keller et al. Poster) • Summer surface water nutrient limitation • Winter light limitation • Influenced by weather and storm events • Results in a generally consistent seasonal progression • Maximum values are in the pycnocline during stratification and in the waters of the western nearfield and outer Boston Harbor

  42. Water Quality Chlorophyll Distribution • Seasonal peaks are observed in the spring, summer, and fall • Classic winter/spring bloom does not always occur • Frequently observe a major fall boom • Large sustained bloom occurred in the winter/spring of 1999 following a late winter bloom in December 1998 Asterionellopsis glacialis Phaeocystis pouchetii Phaeocystis pouchetii

  43. Water Quality Nearfield Chlorophyll - Fall Blooms 1993 1995 1998

  44. Water Quality Nearfield Chlorophyll - Spring Blooms 1992 1994 1996

  45. Water Quality Nearfield Chlorophyll Winter Bloom 1998-1999 Nearfield Chlorophyll 1998 - 1999 Satellite imagery suggests chlorophyll levels in the surface waters of Massachusetts Bay remained elevated between mid-Dec 1998 and early February 1999

  46. Water Quality Annual Chlorophyll Data

  47. Water Quality Seasonal Chlorophyll Data

  48. Water Quality Chlorophyll Summary • Spring bloom not as consistent as conventional wisdom would suggest • Fall bloom appears to be a consistent event • having occurred in 5 of 7 years • Elevated summer concentrations observed in Nearfield (98 & 99)

  49. Water Quality Dissolved Oxygen • Degradation of particulate organic matter (POM) • water column • deposited POM in sediments • Other factors • duration and strength of stratification • bottom water temperature • initial DO concentration at onset stratification • downwelling/intrusion events Many factors affect dissolved oxygen levels in the water

  50. Water Quality Dissolved Oxygen • Mean DO in bottom waters has exceeded the caution level once • 1999 may have an exceedance in September or October

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