Nutrient Loading and River Responses in the Tidal Potomac
March 18, 2008
W. R. Boynton
Work supported by UMCES, NSF, MD-DNR, MD-MDE, NOAA, EPA Outline • Some Background and Definitions • Nutrient loads…Past and Present • Water Quality Conditions (historical and current) • A short SAV story • Some special features (blooms, pH, sediment/bloom interactions) • A budget for Nitrogen…where does this stuff go? • Chesapeake and Potomac Fisheries • Some concluding remarks
Eutrophication
A Global Issue
Harmful Algal Blooms Seagrass Loss Hypoxia/Anoxia Compiled by K. Mikita 1996
Agnes 2003 June 72 Potomac River Point of Rocks Ranked Flow Data Daily Average Cubic Feet Per Second (cfs)
25000
20000
s 15000
10000 Daily avg cf
5000
0 1996 2003 1998 1984 1994 1993 2004 1985 1989 1987 1997 1992 2005 1990 2006 1991 1995 1988 1986 2000 2001 2002 1999 Year
Wet Moderate Dry
4X variability in flow during 23 year record From P. Tango Potomac in Flood Potomac NOT in Flood Sea level is rising in Chesapeake Bay (from J C Stevenson)
Source: Permanent Service Baltimore sea level for Mean Sea Level
Issue of Long-term MD Water Temperature 39º N Change DE
38º N VA
37º N
Pa 77º W 76º W tux en t R iv er Water temperature (C) 13 14 15 16 17 18 1930 Water Temperature(solid symbol) 1.5 Cincreasefrom1938 to2006 1940 Five warmestyears≥ 1950 +0.22 Cperdecade CBL PierDataSet 1960 1938-2006 Year 1970 1980 1990 1990
Secor and Wingate. In review 2000 2010
10 11 12 13 14
8 9 Air temperature (C) temperature Air Warming in the Chesapeake: Heading South??
61 F* Ches. Biol. Lab 2050 2100
63 F* +3 F +7 F Goodwin Isl.
66 F* Cape Fear
70 F* Winyah Bay
* Average Annual Temperature, 2006 7-8 F rise in temp – A new ecosystem!? N. Jaworski 2007
W. Scheldt 34 Back River Tokyo Bay Boston Harbor 33 100 32 31 -1
Potomac 29 yr Potomac 30 28 Estuary 26 N. San Fran Bay -2 27 24 25 23 22 21 20 35 19 18 Mobile Bay 16 100 10 Himmerfjarden 14 15 11 13 12 -1 10 80 N yr 9 Gulf Riga 6 78 6 TN Load, gN m TN gN Load, 5 60 4 2 3 Kaneohe Bay (post-div) 40 Sinepuxent Bay Susquehanna River 25 year record MD 1 Buzzards Bay 10 x kg Load, TN 1 20 023451 TP Load, kg x 106 P yr-1 0.1 1 10 100
TP Load, gP m-2 yr -1
Potomac River Estuary Nitrogen Budget (1985-1986)
Atmos Point Diffuse Upper Portion Sources Sources Deposition of Basin
Tidal Portion of Basin ~0 2.6 19.8 Export to Atmos 1.9 Chesapeake Bay Deposition Potomac River 14.1 9.3 Point Estuary 40% Sources
Diffuse 1.9 1.6 Sources Removal via Fisheries
5.6 16% 14.2 40%
Denitrification Long-Term Burial
-2 -1 Boynton et al 1995 Total Load = 30-35 g m yr
• Hypoxia in 2007 was not particularly severe…but not good •Potomac one of the large hypoxic zones of the Bay system •Note the disconnect between the Bay and Potomac low DO waters
Hypoxia vs. Mean Depth in Chesapeake Bay and Tributaries 1986-1998 100
60 Rappahannock River Potomac River Chesapeake Bay 40 York Hypoxia (%) River
20
James River 0 345678910 Mean Depth (m)
Microcystis Bloom 2004
(P. Tango, MDDNR) Summer (June-September) % bloom samples (>10,000 cells/milliliter Microcystis ) for 9 Potomac River stations, 1985-2006. 35 30 25 s 20 15 % sample 10 5 % samples > 10K/ml 0
9 1 95 7 9 3 5 985 98 99 993 9 99 99 001 00 00 1 1987 1 1 1 1 1 1 2 2 2 Year % bloom samples
P. Tango, pers comm.
“Gotta Love these Babies”
Bloom Year Potomac Sediment PO4 Flux A case where bad gets worse…and fast!
) 200 -1 h -2
150 Huge Fluxes
100
moles-P m Large μ 50 Fluxes
0 Flux ( 4
PO -50 7 8 9 10 11 12 pH
From Bailey et al. 2006 Potomac Estuary SAVs Patuxent River Estuary Circa 1832 • “Of all the bright rivers that flow into it (Chesapeake Bay) there is not one which excels the Clearwater (Patuxent) in the purity of its waters.”
• “So transparent are its waters that far out from shore you may see, in the openings of the sea- weed forest, on its bottom the flashing sides of the finny tribe as they glide over the pearly sands.” The Old Plantation by Hungerford (1859)
Solomons Island SAV - 1933
Solomons Island SAV - 1963
SAV Coverage and Secchi Depth Tidal Potomac River Estuary (1983 – 1989)
Turbid water and SAV Clearer water and beds contract SAV beds expand
From Carter et al. 1994
Potomac River Fisheries
• Another issue the public cares about
• Possibly a catch…hug…and release fishery is the answer Chesapeake Bay
10000 Marine Systems (r2=0.84)
1000 540kg
140 kg 140 kg 100
18 kg 10 Lakes (Oglesby 1977) 2 r =0.74 Adapted From Nixon, 1988 1 10 100 1000 10000
PRIMARY PRODUCTION (g C m-2 y-1)
Chesapeake Bay yields 30 times more fish than an average lake with the same primary production ... MARYLAND OYSTER HARVEST
16 4 200 700 days days days 14
12
10
8 Oyster Diseases
6 Millions of Bushels Millions
Oyster Harvest Oyster 4
2
0 1840 1860 1880 1900 1920 1940 1960 1980 2000 Year ) 20.00
6 Potomac River Estuary
10 18.00 x Total Landings Commercial Fishery Yields 16.00 14.00 1965 - 2001 12.00 10.00 8.00 6.00 4.00 Total Annual Landings(kg 2.00 • General downward 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 trend since mid-1980’s
7.00
) Striped Bass 6 • Variable amount 6.00 Oysters 10 x 5.00 know concerning these
4.00 trends 3.00
2.00 • What do we know
Annual Landings(kg 1.00 about stock size and 0.00 fishing effort? 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
5.00 • Potomac River
) Blue Crab 6 Fisheries Commission 4.00 has detailed spatial 3.00 catch data…the best in 2.00 the Bay region
1.00 Annual x (kg Landings 10
0.00 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year
(a)
Trajectories of Response(a) to Nutrient Loading
Linear Response (a) • Theory suggests alternative ecosystem
))) D response to changes in environmental 22 2 e gr ad ati conditions (e.g., nutrient loading, climate) on Nutrient Loading R est Ecosystem State Ecosystem Ecosystem State Ecosystem Ecosystem State Ecosystem or (SAV, bottom O (SAV, (SAV, bottom O (SAV, (SAV, bottom O (SAV, ati Nutrient Loading on • Responses can follow ~linear pathways with direct proportional response (a) (b) Nutrient Loading
Threshold (b) De grad ) ) at 22 ion • Responses can follow “sigmoidal” shape with apparent threshold shift within narrow range of environmental conditions R Ecosystem State Ecosystem State Ecosystem (SAV, bottom O (SAV, (SAV, bottom O (SAV, es tora Nutrient Loading tion
(c) Nutrient Loading
De gradation Hysteresis • Responses can exhibit multiple stable ) 2 Backward Shift states with abrupt transitions and hysteretic
Forward patterns where degradation and restoration Shift Ecosystem State Ecosystem (SAV, bottom O (SAV, follow different trajectories R estoration
Nutrient Loading From Scheffer et al. 2001 Summary and Recommendations
• The Potomac is a typical“OVER-ENRICHED” estuary…too much of a good thing • Nutrient inputs need to be reduced by a large margin…there has been success with P and now N reductions need attention • Climate variability and change are emerging issues and complicate forecasts • Upper estuary SAV recovery very positive; lower estuary habitats are still degraded • What are the likely recovery trajectories…we need to know for better management planning!! Acknowledgements Figures, maps, photos and data with help from: J. Cornwell (UMCES-HPL) L. Wainger (UMCES-CBL) J. Anderson (MERC) J. Julian (UMCES-APL) N. Rybiki (USGS) M. Kemp (UMCES-HPL)
M. Hall (MDDNR)
P. Tango (USGS/CHPO)
N. Jaworski