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A PROTOCOL FOR MONITORING
ESTUARINE NUTRIENT ENRICHMENT
IN COASTAL PARKS OF THE NATIONAL PARK SERVICE NORTHEAST REGION
Natural Resource Report NPS/NCBN/NRR—2009/110
Blaine S. Kopp and Hilary A. Neckles
USGS Patuxent Wildlife Research Center
196 Whitten Road
Augusta, ME 04330
207-622-8201
bkopp@usgs.gov
hneckles@usgs.gov
May 2009
U.S. Department of the Interior
National Park Service
Natural Resource Program Center
Fort Collins, Colorado
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Introduction
Nutrient enrichment of the coastal zone is a worldwide consequence of human population
growth. Land clearing, fertilizer production and application, discharge of sewage and septic
systems, and fossil fuel combustion have accelerated nitrogen and phosphorus loading to coastal
ecosystems since the 1950’s (Nixon 1995, Cloern 2001). Estuaries in the northeastern U.S. are
particularly threatened by human disturbances within the densely populated coastal zone (Roman
et al. 2000). The Northeast (from Maine to Maryland) currently accounts for about one third of
the coastal population of the entire United States (NOAA 1998). The population density of this
narrow coastal fringe is more than double that of any other region of the country, and it continues
to grow. The consequent residential, agricultural, and urban expansion will result in a continued
increase in anthropogenic nutrient loading to the region’s coastal zone. Estuaries can generally
assimilate some degree of enrichment without major ecological ramifications, but excessive nutrient inputs typically lead to dense blooms of phytoplankton and fast-growing macroalgae
loss of seagrasses, and decreased oxygen availability in sediments and bottom waters (Valiela et
al. 1992, Nixon 1995, Borum 1996, Bricker et al. 1999). Ultimately, cascading effects include
changes in the species composition and abundance of invertebrates, decline in fish and wildlife
habitat value, and the collapse of fin- and shellfish stocks.
Within the Northeast Region (NER), the National Park Service (NPS) protects a total of about
1,891 square kilometers between Virginia and Maine. Approximately one quarter of this area is
submerged as estuaries, bays, and lagoons (NPS 2000a). The NER coastal parks are dependent
on high-quality aquatic resources to sustain the complex estuarine and nearshore ecosystems they
represent. Diverse threats to NPS estuaries exist, including natural disturbances (e.g. storms, sea
level rise), direct impacts of human activities (e.g. fishing, boating, dock construction), indirect
effects of watershed development, and disasters (e.g. oil and toxic spills.) Of these, park
managers have repeatedly identified threats to coastal water quality as one of their highest
priority issues (PWRC 1999). Much of the watershed area of NPS coastal ecosystems lies
outside protective park boundaries and is subject to intense developmental pressures. Therefore,
there is great potential for human alterations of coastal watersheds to result in increased nutrient
loading to park waters. Protecting the ecological integrity of park estuaries depends on
implementing a scientifically-based monitoring program that is capable of diagnosing local
causes of nutrient enrichment, detecting changes in nutrient loads, and determining if nutrient
inputs are near to exceeding thresholds that would result in shifts in ecosystem structure and
function (cf. NRC 2000).
The NPS Northeast Coastal and Barrier Network (NCBN) consists of eight parks from
Massachusetts to Virginia. The four largest parks include extensive estuarine habitat:
Assateague Island National Seashore (ASIS), Maryland/Virginia; Cape Cod National Seashore
(CACO), Massachusetts; Gateway National Recreation Area (GATE), New York/New Jersey;
and Fire Island National Seashore (FIIS), New York. Colonial National Historic Park (COLO),
Virginia, is a park of almost 8000 ha with a moderate amount of estuarine shoreline, and two small parks, Sagamore Hill National Historic Site (SAHI), New York, and George Washington
Birthplace National Monument (GEWA), Virginia, also include short stretches of estuarine
shoreline. The last of the network parks, Thomas Stone National Historic Site, neither contains
nor directly abuts any estuarine resources. In addition, two parks within the Northeast
Temperate Network (NETN) also include extensive estuarine habitat: Acadia National Park
(ACAD), Maine; and Boston Harbor Islands National Park Area (BOHA), Massachusetts.
Collectively, these park units represent a wide range of sizes (33 ha to almost 20,000 ha),
latitudes (37°11.3’N to 44°25.6’N or more than 800 km), watershed geologies (shallow soils
overlying granite bedrock vs. thick sandy glacial deposits), tidal range (micro-tidal to over 3m),
and fresh water sources (surface water vs. ground water; Roman et al. 2000). Estuaries within
these parks share fundamental characteristics, however, including temperate zone flora and fauna
and the threat of nutrient enrichment as a primary management concern (Roman et al. 2000).
Their broad similarities are the basis for development of a uniform regional protocol for
monitoring estuarine nutrient enrichment within the nine park units of the NCBN and the NETN
that contain estuarine resources.
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