Spatio-temporal Patterns and Multi-decadal Trends in Nutrients in Narragansett Bay David Borkman ( dborkman@gso.uri.edu ) & Ted Smayda ( tsmayda@gso.uri.edu ) Narragansett Bay University of Rhode Island Graduate School of Oceanography NY Bight Nutrient Workshop 7&8 July 2010
Long-term Station Aerial photo of Narragansett Bay (Courtesy of R. L. Wilke) Narragansett Bay (ca. 328 km 2 ) Mean depth: 8m (~60m maximum) Salinity range: 20-32 Temperature range: -2 to 25 C ca. 1 m tidal range, 10-28d residence time ca. 1.8 x 10 6 people in 4,000 km 2 watershed
Blackstone River Pawtuxet River Taunton River 41 40 N Hunt / Potowomut Long-term monitoring site (station II) 41 30 N 71 20 W
Narragansett Bay time series: 1959 to 1997 (+ ongoing) Meteorological Nutrients River flow 1959-97 NO3 1959-63, 69-97 Precipitation 1959-97 NH3 1972-97 Wind speed 1959-97 PO4 1959-63, 69-97 Irradiance 1959-97 SiO3 1959-63, 69-97 Temperature 1959-97 Urea 1972-78 Salinity 1959-97 NO3 reductase 1975-77 Secchi depth 1972-97 PO4 reductase 1976-77 Phytoplankton Zooplankton Species composition 1959-97 Species composition 1972-90 Abundance 1959-97 Numerical abundance 1972-90 Chlorophyll 1968-69, 72-97 Dry wt. biomass 1972-97 ATP-C biomass 1972-97 C, N biomass 1972-97 Primary production 1979-90 Ctenophore abundance 1973-97 Size fractionation 1972-78, 87-88
Annual Mean Surface Temperature ( o C) lower Narragansett Bay 13 y = 0.029x - 46.87 R 2 = 0.48 12 11 10 1950 1960 1970 1980 1990 2000 2010 Year
Temperature ( o C) and winter diatoms (cells ml -1 ) lower Narragansett Bay 4,000 3,500 3,000 y = -240.47x + 5944.8 R 2 = 0.2543 2,500 10 11 12 13 Temperature ( C Smayda et al., 2004
µg L -1 20 15 Chlorophyll y = -1.49x + 10.43 R 2 = 0.87 10 5 0 60s 70s 80s 90s 00s Decade
Chlorophyll, surface 12 10 1970s 2000s µg L -1 8 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 Month
8 7 NH4, surface (umol) 6 5 4 3 2 1 0 1950 1960 1970 1980 1990 2000 2010 Year Lower Bay NH4 relatively stable mid-1990s on
8 7 6 Surface NO3 (µm) 5 4 3 2 1 0 1950 1960 1970 1980 1990 2000 2010
Annual Mean Secchi Depth & Long-term Trend (m) 5.0 4.5 Clearer water 4.0 3.5 3.0 2.5 2.0 Turbid water 1970 1975 1980 1985 1990 1995 2000 Year -Water clarity has increased 1980 to 1992 (Borkman and Smayda, 1998)
Monthly TSS Load (10 6 kg) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1980 1985 1990 1995 Year (1983 to 1996)
Mean Secchi disk depth (m) 5 4 3 2 0 2 4 6 8 10 Annual TSS load (10 6 kg yr -1 ) Y = -0.17 x + 4.02, r 2 = 0.43 Borkman and Smayda, 1998
Monthly TSS Nitrogen Discharge (kg) 25,000 20,000 15,000 10,000 5,000 Nitrogen 0 1980 1985 1990 1995 3,500 Monthly TSS Phosphorus Discharge (kg) 3,000 2,500 2,000 1,500 1,000 500 0 1980 1985 1990 1995 Phosphorus Year
Estimated Chlorophyll from TSS Nitrogen (mg m -3 ) 12 10 8 6 4 2 Chlorophyll potential from TSS Nitrogen 0 1980 1985 1990 1995 Year
100 r 2 = 0.46 (all data); r 2 = 0.75 (w/o 1983, 1996) Mean Annual Chlorophyll (mg m -2 ) 80 60 40 20 Predicted Chl from TSS nitrogen Mean annual Chl (Li & Smayda, '98) 0 1980 1985 1990 1995 Year
Also, Need to consider oceanic variability Borkman & Smayda, 2009
Nutrient Ratios Skeletonema level declined : 400 cells ml -1 pre-1980 90 cells ml -1 1980-96 Updated: 111 cells ml-1 1997-2008 deseasonalized Skeletonema costatum (cells ml -1 ) 10000 1000 100 10 1950 1960 1970 1980 1990 2000 2010 Year Source: Borkman & Smayda (2009)
6 Mean Annual Diatom : Flagellate Ratio 5 4 3 2 1 0 1955 1965 1975 1985 1995 Year
0.4 6 Si : N Ratio 0.3 0.2 0.1 r 2 = 0.46, p<0.0005 5 4 3 2 1 Diatom : Flagellate Ratio 0 1955 1965 1975 1985 1995 0 Year
Diatom : : Flagellate ratio Ratio 6 5 4 3 2 1 0 5 10 15 20 25 30 35 Si : P ratio y = 0.228x - 1.192 R 2 = 0.75 (all data) Station II, Narragansett Bay
NBAY & TIME SERIES SUMMARY Major changes, trends have occurred in Physical properties (temperature; transparency) Macronutrients (concentrations and ratios) Plankton Phytoplankton biomass, production; bloom cycles, species Copepod abundance Plankton dynamics are regulated by two primary and confluent drivers: Internal forcing (nutrient supply, ratios) External forcing (climate; coastal shelf physics) Strong field evidence that plankton dynamics sensitive to nutrient and thermal conditions, consistent with transect and experimental data NBay a biogeographic transition zone; sensitivity to winter T
60 50 2 Surface 1985-86 1986-87 40 30 20 10 0 y = 7E+10x R 2 = 0.91-6.86 20 22 24 26 28 30 32 Mean Annual S (psu) 7 1985 1987 Transect Study Smayda and Borkman, 2008
50 Surface 1985-86 1986-87 Mean Annual Si(OH) 4 (µm) 40 30 20 10 20 22 24 26 28 30 32 Mean Annual S (psu) Smayda and Borkman, 2008
14 12 2 Surface 1985-86 1986-87 Mean Annual N:P (atoms) 10 8 6 4 3 4 4 N sensitive 5 5 1 6 7 2 20 22 24 26 28 30 32 Mean Annual S (psu) Smayda and Borkman, 2008
2.0 1.8 Si sensitive Surface 1985-86 Mean Annual N:Si (atoms) 1.6 1.4 1.2 1.0 0.8 0.6 2 3 4 1986-87 N sensitive 0.4 0.2 0.0 20 22 24 26 28 30 32 Mean Annual S (psu) Smayda and Borkman, 2008
Mean Annual Chlorophyll (mg m -3 ) 30 20 10 7 6 Surface 1985-86 4 1986-87 5 3 1 3 5 4 2 6 1 7 2 0 y = -0.02x 2 + 1.03x + 10.75 R 2 = 0.83 0 10 20 30 40 50 60 Mean Annual NH4 + NO3 (µm) Smayda and Borkman, 2008
300 Surface Annual Carbon Production (g C m -3 ) 200 100 1985-86 1986-87 2 y = -0.25x 2 + 14.92x + 36.87 R 2 = 0.83 0 0 10 20 30 40 50 60 Mean Annual NH4 + NO3 (µm) Smayda and Borkman, 2008
100 1 1 day N y = -27.54Ln(x) + 124.17 R 2 = 0.95 6 % residual N used daily 80 60 40 7 5 1.5 days N 2.3 days N 4 4 days N 20 3 2 Surface 1985 7.5 days N 0 2 10 18 26 34 42 50 NO3 + NH4 (µm) Smayda and Borkman, 2008
Saturation concentration Mean Annual Chlorophyll (mg m -3 ) 30 20 10 Dose-yield region Assimilatory capacity exceeded Surface 1985-86 4 1986-87 5 3 6 1 3 5 4 2 6 7 1 7 2 0 y = -0.02x 2 + 1.03x + 10.75 R 2 = 0.83 0 10 20 30 40 50 60 Mean Annual NH4 + NO3 (µm) Smayda and Borkman, 2008
Smayda & Borkman, 2008
2 ENRICHMENT ZONE Si sensitive 3 NAYATT PT GREENWICH BAY 1 4 5 DEPURATION ZONE 6 7 ADVECTION ZONE N sensitive NARRAGANSETT BAY
Gradients occur in GRADIENT ANALYSIS SUMMARY Salinity, Nutrients, Phytoplankton (biomass, production), Zooplankton & Ctenophore biomass Upper NBay exports nutrients, ctenophores downbay NBay Sanctuary region an important nutrient depuration zone Nutrient gradient pulsates with riverine discharge Uniform bloom behavior characterizes NBay Spatial shift from Si limitation in upper NBay to N limitation downbay Coupling occurs between Nutrients and salinity Chlorophyll and nutrients Primary production and nutrients Zooplankton - Phytoplankton Biomass Zooplankton - Phytoplankton Production Ctenophore - Zooplankton Biomass
Buzzards Bay Nutrient Patterns David Borkman University of Rhode Island Graduate School of Oceanography ( dborkman@gso.uri.edu ) & Jeff Turner University of Massachusetts - Dartmouth Center for Marine Science and Technology ( jturner@umassd.edu ) NY Bight Nutrient Workshop 7&8 July 2010
Buzzards Bay - 45 km by 12 km, 590 km 2 area - ca. 560 km of coastline - 11 m mean depth - ca. 1,100 km2 watershed area - Population = ca. 260,000 people -New Bedford = ca. 100,000 people - 30MGD effluent discharge @ New Bedford -1996 secondary treatment -1987 to present monitoring by Jeff Turner (UMass Dartmouth).
Source = Turner et al., 2009
Source = Turner et al., 2009
Source = Turner et al., 2009
Source = Turner et al., 2009
Source = Turner et al., 2009
Source = Turner et al., 2009
Source = Turner et al., 2009
Regionally coherent changes in: Increasing temperature Declining chlorophyll Buzzards Bay Summary Improved sewage treatment practices evident in: Declining water column N Increased water clarity Reduced shellfish closures 22 year (1987-on) water column nutrient and related plankton data (contact Jeff Turner; jturner @umassd.edu)
Non-linear responses? Boston Harbor: 80-90% decrease in TN loading 1991-2000. Linear water column nutrient responses Curvilinear biological responses? Source = Taylor, Oviatt, Borkman. in press. Estuaries & Coasts.
Summary Eastern NY Bight Regionally coherent Temperature trends Phytoplankton biomass trends Phytoplankton and zooplankton species Need to manage regionally Consider oceanic variability (Gulf Stream, warm core rings, circulation) Estuarine gradient as a potential management tool Need to incorporate changing phytoplankton patterns into management strategies Management of loadings and nutrient ratios Need to maintain long-term monitoring programs Narragansett Bay data available: 1959-1997: ( http://www.narrbay.org/d_projects/plankton-tsv/plankton-tsv.htm ) RI SeaGrant funded data rescue 1999-on: (http://www.gso.uri.edu/phytoplankton/ ) URI Graduate School of Oceanography
References David I. Taylor, Candace A. Oviatt, David G. Borkman. 2010. Non-linear responses of a coastal aquatic ecosystem to large decreases in nutrient and organic loadings. Estuaries and Coasts. In press, accepted 1 June 2010. Borkman, DG and Smayda, TJ. 2009. Gulf Stream position and winter NAO as drivers of long-term variations in the bloom phenology of the diatom Skeletonema costatum "species-complex" in Narragansett Bay, RI, USA. J. Plankton Res. 31: 1407-1425. Borkman, DG and Smayda, TJ. 2009. Multidecadal (1959-1997) changes in Skeletonema abundance and seasonal bloom patterns in Narragansett Bay, Rhode Island, USA. Journal of Sea Research 61: 84-94. Turner, JT, DG Borkman, JA Lincoln, DA Gauthier, CM. Petitpas. 2009. Plankton Studies in Buzzards Bay, Massachusetts, USA. VI. Long-term studies of phytoplankton, bacterioplankton and environmental parameters, 1987 to 1998. Marine Ecology Progress Series 376: 103-122. Smayda, T.J. & D. Borkman. 2008. Nutrient and phytoplankton gradients in Narragansett Bay. Chapter 15 in: Desbonnet, A. and Costa-Pierce, B. (eds.), Science for Ecosystem-Based Management: Narragansett Bay in the 21 st Century. Springer, Berlin. pages 423 476. Smayda, T.J., D. Borkman, G. Beaugrand & A. Belgrano 2004. Ecological effects of climate variation in the North Atlantic: Phytoplankton. pp. 49-58. In Marine Ecosystems and Climate Variation -- the North Atlantic. N.C. Stenseth, G. Ottersen, J.W. Hurrell, A. Belgrano, and B. Planque, Eds. Oxford University Press, 266 pp. Borkman, D.G. & T.J. Smayda 1998. Long-term trends in water clarity revealed by Secchi disk measurements in lower Narragansett Bay, Rhode Island, USA. ICES Journal of Marine Science 55: 668-679. Borkman, D.G. & J.T. Turner 1993. Plankton studies in Buzzards Bay, Massachusetts. II. Nutrients and phytoplankton pigments, 1987-1990. Mar. Ecol. Prog. Ser. 100: 27-34. Turner, J.T. & D.G. Borkman 1993. Plankton studies in Buzzards Bay, Massachusetts. I. Hydrography and bacterioplankton, 1987-1990. Mar. Ecol. Prog. Ser. 100: 17-26.