Estuaries Vol. 23, No. 6, p. 743±764 December 2000

Estuaries of the Northeastern United States: Habitat and Land Use Signatures

CHARLES T. ROMAN1,*, NORBERT JAWORSKI2,FREDERICK T. SHORT3,STUART FINDLAY4, and R. SCOTT WARREN5

1 USGS Patuxent Wildlife Research Center, Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882 2 (retired, U.S. Environmental Protection Agency), 2004 Magnolia Avenue, Sanford, Florida 32771 3 Jackson Estuarine Laboratory, University of New Hampshire, 85 Adams Point Road, Durham, New Hampshire 03824 4 Institute of Ecosystem Studies, Box AB, Millbrook, New York 12545 5 Department of Botany, Connecticut College, New London, Connecticut 06320

ABSTRACT: Geographic signatures are physical, chemical, biotic, and human-induced characteristics or processes that help define similar or unique features of estuaries along latitudinal or geographic gradients. Geomorphologically, estu- aries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons occur within the northeast region, but the domiant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast estuaries are generally greater when compared to estuaries of the more southern U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drainage basins, low riverine flows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water clarity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and rocky shores represent major habitat types that fringe northeast estuaries, supporting commercially-important fauna, forage nekton and benthos, and coastal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a century of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment facilities and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast, with relative importance increasing for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure, function, and processes of estuaries along latitudinal gradients.

Introduction responses within a region. For example, Chapman Estuaries have been classified as drowned-river (1960) observed that salt marshes in New England valleys or coastal plain, bar-built, lagoons, fjords, are often small in area with organic peat substrates and tectonically-caused (Pritchard 1967a). Within resulting from small drainage basins with relatively this geomorphic classification, estuaries are de- low suspended sediment loads. In contrast, south- fined by a diverse suite of characteristics, including eastern U.S. drainage basins are large with high circulation patterns (Pritchard 1967b) and related suspended sediment loads resulting in extensive physical factors (e.g., tidal range, freshwater input, salt marshes with substrates of high inorganic con- sediment load, etc.), dominant habitat types, and tent. Physiography of the drainage basin and sus- watershed factors, including physiography and pended sediment load can be considered as key land use. These characteristics often vary geo- characteristics, or signatures, that define the vari- graphically and can be evaluated to define funda- ability of salt marshes across regions. Similarly, mental signatures of estuaries on a regional basis. these factors regulate seagrass distribution and Geographic signatures, as defined in this paper, growth along the U.S. Atlantic coast. As the high are considered as physical, chemical, biotic, and suspended sediment load of southeast coastal plain human-induced characteristics or processes that re- estuaries reduces water clarity, seagrass is limited sult in particular, or sometimes unique, ecosystem in extent and where present, it is limited to less than 2 m depth (Thayer et al. 1984). Seagrass meadows in New England and Canada can exceed * Corresponding author: tele: 401/874-6886; fax: 401/874- 10 m depth (Harrison and Mann 1975; Dennison 6887; e-mail: charles࿞[email protected]. and Alberte 1985; Short and Neckles 1999).

ᮊ 2000 Estuarine Research Federation 743 744 C. T. Roman et al.

Fig. 1. Geographic extent of northeast estuaries. Many of the estuaries and sub-estuaries discussed in this paper are listed.

This paper will focus on the northeastern Unit- natures that define past and current trends in the ed States coastal zone, from the Hudson River and structure and function of estuarine habitats within Long Island Sound to the (Fig. 1). the northeastern U.S. The region is characterized by a diversity of estu- arine types including, glacially-carved (e.g., Penob- Estuarine Geomorphology scot Bay, Maine) and fjord-like systems (Somes GEOLOGICAL HISTORY Sound, Maine), drowned-river valleys (e.g., Con- The shoreline of New England, from the Hud- necticut River, Hudson River) and lagoons (e.g., son River and northward is extremely diverse when Rhode Island salt ponds). There is a wide range of compared to the barrier island-lagoon dominated development pressure and land use history with coast that prevails from the south shore of Long some watersheds exposed to over two centuries of Island, extending along the east coast of the Atlan- intense urbanization (e.g., Lower Hudson River), tic and into the Gulf of Mexico. The basic or gross while others have endured less development (e.g., configuration of the New England shoreline is re- Maine estuaries). This paper identifies the varied lated to the composition of bedrock and its differ- geomorphologies, land use histories, and other sig- ential weathering (FitzGerald et al. 1994). As an Northeast Atlantic U.S. Estuaries 745 example, the coast of Maine has a diversity of shoreline types that are closely related to bedrock geology (Kelly 1987). The northern coast of Maine is a cliffed shoreline, the only continuous bedrock cliff on the U.S. east coast (FitzGerald et al. 1994), composed of volcanic rock eroding in a somewhat uniform manner resulting in a fairly straight shore- line. To the south, encompassing and vicinity, the shoreline is composed of a com- plex of granitic islands and broad embayments, while further south a highly indented shoreline ( region) represents an example of dif- ferential erosion between resistent bedrock pen- insulas and sedimentary deposits. From southern Maine and extending to the Boston area, a series of broad embayments are separated by erosion re- sistent headlands or capes (e.g., Cape Ann, Mas- Fig. 2. Extent of Wisconsin glaciation showing end moraines sachusetts). on Long Island, Rhode Island, and the offshore islands (re- In southern New England, the bedrock was cov- drawn after Oldale 1992). ered by sediment eroded from uplands and de- posited toward the ocean defining the northern- most extent of the Atlantic Coastal Plain. In areas Northward retreat of the ice sheet was rapid, with from New Jersey and south, coastal plain sediments deglaciation of the coastal Gulf of Maine region can be quite thick and extend far inland; however, occurring from between 17,000 to 13,000 BP (years in southern New England the coastal plain is not Before Present). In areas north of Boston land sub- as extensive. The basic shoreline was originally mergence occurred as the ice sheet retreated until shaped as these coastal plain sediments were erod- rebound of the earth’s crust exceeded eustatic sea ed by south flowing drainages, integrated within level rise. During this marine transgression, about less resistant bedrock. The numerous estuaries, ori- 14,000 BP, sea level ranged from 18 m to over 100 ented north-south, along the Connecticut (Lewis m higher than it is today. This high level, or high- and Stone 1991), Rhode Island (McMaster 1984), stand, was brief and with dramatic rebound of the and Buzzards Bay shorelines (FitzGerald et al. crust relative sea level dropped up to 60 m below 1987), such as the Thames River, Housatonic River, present levels, with the lowstand occurring about Narragansett Bay, and Westport River estuaries, 12,000 to 11,000 BP. Sea level then rose rapidly along with a nearly continuous band of smaller es- from about 9,500 to 6,000 BP (about 6 mm yrϪ1) tuaries were formed within this valley-ridge topog- and then began to slow toward the current rate of raphy. 2–3 mm yrϪ1. Areas south of Boston did not ex- New England’s gross shoreline configuration was perience the marine transgression following glacial basically shaped by bedrock geology and estab- retreat because crustal rebound exceeded the rate lished by the Early Tertiary period, but more re- of eustatic sea level rise. cently, during repeated glaciations of the Pleisto- Glacial activity served to shape estuaries by carv- cene Epoch, river valleys and shorelines were deep- ing or scouring bedrock, as evidenced by the fjord- ened, widened, shaped, and/or sediment-filled. like Somes Sound estuary in Maine (Folger et al. The most recent continental glacier, the Lauren- 1972), to re-shape or widen pre-glacial valleys, to tide ice sheet of the late Wisconsin stage, and sub- deliver large amounts of sediments that are the sequent changes in sea level, had an extraordinary foundation for barrier beaches, spits and other re- influence on northeastern U.S. estuaries. The gen- cent shoreline features, and most importantly, to eral chronology of glacial processes and sea level dramatically influence sea level. The present Cape fluctuations since the late Wisconsinan stage, and Cod landscape is defined almost exclusively by sed- relevant to coastal New England, has been de- iment deposition associated with the last glaciation, scribed and interpreted by many (Kelley et al. followed by about 15,000 years of reshaping by 1986; FitzGerald et al. 1994; and references there- modern shoreline processes and sea level rise in). About 20,000 years ago the ice sheet reached (Fisher 1987; Oldale 1992; Uchupi et al. 1996). its maximum southerly position, extending from When the rate of sea level rise began to slow, about near the mouth of the Hudson River, through 6,000 BP, barrier spits began to form throughout Long Island, Block Island, Martha’s Vineyard, Nan- Cape Cod with subsequent establishment of shal- tucket, and eastward to Georges Bank (Fig. 2). low estuarine embayments (e.g., Pleasant Bay and 746 C. T. Roman et al.

Nauset Marsh, Sandy Neck/Barnstable Marsh). age of the types of estuaries found in the northeast. The sequence of barrier spit growth and subse- For instance, it is estimated that just 25% of the quent salt marsh development within the protect- Massachusetts and Connecticut shoreline is com- ed embayment is best typified by Redfield’s (1965) posed of barrier systems, despite being the portion classic study of Sandy Neck/Barnstable Marsh of the region with most abundant sediment sup- (Cape Cod, Massachusetts), where growth of the plies for barrier formation (FitzGerald et al. 1994). spit and salt marsh began about 4,000 years ago. Most of the major estuarine systems in the region Similar to the Cape Cod example, barrier sys- are of the drowned-river valley (e.g., Hudson River, tems and salt marshes that are present today began Connecticut River, Narragansett Bay, Kennebec to form throughout the New England region about River) or drowned-basin type (e.g., Long Island 4,000 years ago, under a regime of slowed sea level Sound). The bedrock shorelines of the estuaries rise. In southern Maine (Wells, Maine), a basal ra- throughout the region were carved by glacial ac- diocarbon date of 4,220 BP is reported for back tivity, but just one estuary in the northeast has the barrier salt marsh peat (Kelley et al. 1988). On typical geomorphology of a fjord-type estuary. Long Island Sound, Orson et al. (1987) describe a Somes Sound is a long (8 km), narrow (Ͻ 1 km), scenario of marsh development beginning about U-shaped valley flanked by mountains that rise 3,800–4,000 years ago that was independent of bar- over 250 m above sea level, with a maximum depth rier formation; freshwater marsh was replaced by of 50 m and a shallow 10 m sill at the mouth (Pet- salt marsh as the Pataguanset River valley was tigrew et al. 1997). drowned with sea level rise. On the northern coast Reflecting the glacial history of the region, of Maine, a salt marsh located along the estuarine northeast estuaries are generally deep, except for shore of a major river system dates to 4,095 BP, the back-barrier systems (Fig. 3). Based on the Na- with salt marsh peat overlying freshwater peat (Kel- tional Oceanic and Atmospheric Administration ley et al. 1988), similar to the Pataguanset example. National Estuarine Inventory database, the average depth of northeast estuaries (, GEOMORPHOLOGICAL CHARACTERISTICS Maine to Hudson River/Raritan Bay, New York/ Because of this complex of bedrock geology, gla- New Jersey) is 13 m, compared to the much shal- cial history, and sea level rise, coupled with factors lower coastal plain and back-barrier estuaries to like sediment supply and wave exposure, the shore- the south (Middle Atlantic, 3 m; South Atlantic, 4 lines of New England estuaries and associated hab- m; Gulf of Mexico, 2 m; National Oceanic and At- itats are extremely variable. Extensive barrier is- mospheric Administration 1990). land shorelines (often extending for 50 km or more) fronting large shallow lagoonal estuaries PHYSICAL CHARACTERISTICS (e.g., Barnegat Bay, New Jersey; Pamlico Sound, Because of high tidal range and relatively low North Carolina) or large salt marsh complexes freshwater discharge from riverine sources, tidal (e.g., associated with the Georgia and South Car- mixing is the dominant factor determining circu- olina coastal barriers) are limited in New England. lation patterns in northeast estuaries. Mean range The barrier system (e.g., Plum of the semidiurnal tide in Passamaquoddy Bay can Island, Massachusetts; FitzGerald et al. 1994), the approach 6 m and is generally up to 3 m elsewhere outer Cape Cod barrier complex (e.g., Nauset Spit, throughout Gulf of Maine estuaries (Fig. 3). Tidal Monomoy Island, Massachusetts; Uchupi et al. range of more southern New England estuaries is 1996), and the southern shore of Rhode Island less (about 1–2 m), but still greater than in estu- (Boothroyd et al. 1985) contain sandy barriers of aries along the coastal plain to the south. There about 30 km in length that front shallow estuaries are obvious exceptions, such as the minimal tidal dominated by Spartina marsh or tidal lagoons. range of Rhode Island’s coastal pond estuaries (Ͻ However, most of the barrier shorelines of New 0.5 m; Isaji et al. 1985), or portions of the Georgia England are short, generally less than 1 km, and coast exhibiting tidal ranges of 2 m or more. De- unlike the sand substrate of barriers to the south, spite these exceptions, tides of the northeast coast, they can be composed of sediment ranging from and especially within the Gulf of Maine, are am- fine sand to gravel and cobble, reflecting local bed- plified with the highest recorded tides in the world rock and glacial geology (FitzGerald et al. 1994). occurring in the (15 m). Shallow estuaries are often associated with these With regard to freshwater flow, Fig. 4 clearly il- small barriers. lustrates that estuaries in the northeast have sig- While barrier shorelines are found throughout nificantly lower average daily riverine flow than es- the region from northern Maine to the Hudson tuaries of the middle and south Atlantic coastal River estuary, back barrier estuaries, lagoons and plain and Gulf of Mexico. In the northeast, water- coastal ponds represent a relatively small percent- sheds are generally smaller as exemplified by the Northeast Atlantic U.S. Estuaries 747

Fig. 3. Maximum depth and mean tidal range of selected estuaries in the northeast (data from National Oceanic and Atmospheric Administration 1990). ratio of watershed drainage area to estuary water el, and sandy shores, tidal mudflats, tidal wetlands, surface area for selected estuaries (Table 1). and seagrass. It is estimated that salt marshes exist Owing to the relatively small drainage basins, along just 20% of Maine’s 5,790 km of tidally in- low freshwater flows, a bedrock substrate and rel- fluenced coastline ( Jacobson et al. 1987), with the atively dense forest cover throughout the northeast remainder presumably occupied by bedrock, grav- region, sediment loads delivered to northeast es- el/cobble, or sand/mud shores. Similarly, most tuaries are generally lower when compared to shorelines of Narragansett Bay are narrow beaches more southern coastal plain watersheds. Conse- of cobble and gravel and some bedrock shores, quently, water clarity in northeast estuaries is great- with salt marshes being much less conspicuous (Ol- er than to the south, as reflected by a review of sen et al. 1980). Estuarine beaches are common light extinction coefficient data distributed along throughout the northeast because there is a suffi- a geographic gradient (Table 2). cient supply of sand or gravel and adequate wave Estuarine Habitats and tidal energy to rework the sediments (Nords- OVERVIEW trom 1992). Small gravel pocket beaches are com- The major nearshore and intertidal habitats of mon along the shoreline of Maine’s estuaries, with northeastern estuaries include rocky, cobble, grav- the sediment derived from eroding bedrock (Duffy 748 C. T. Roman et al.

TABLE 1. Ratio of watershed drainage area to estuary water surface area for selected estuaries along the Atlantic and Gulf of Mexico coasts (data from National Oceanic and Atmospheric Administration 1990).

Estuary Ratio Northeast Passamaquoddy Bay 20 Penobscot Bay 26 Casco Bay 7 3 Buzzards Bay 3 Narragansett Bay 11 Long Island Sound 13 Hudson/Raritan, New York/New Jersey 55 Middle Atlantic Barnegat Bay 14 Delaware Bay 18 Chesapeake Bay 18 Southeast Atlantic Cape Fear River 239 Winyah Bay 603 Fig. 4. Average daily freshwater flow to northeast, middle Altamaha River 947 and south Atlantic, and Gulf of Mexico estuaries (data from St. Andrews, St. Simons Sounds 56 National Oceanic and Atmospheric Administration 1990). Gulf of Mexico Apalachicola Bay 96 Mobile Bay 109 Atchafalaya 143 et al. 1989). In contrast, a coastal plain estuary like Galveston Bay 45 Delaware Bay contains a nearly continuous salt marsh border (Daiber and Roman 1988), yet es- tuarine beaches often front the marshes. Along the South Carolina and Georgia coasts salt marshes are TIDAL MARSHES extensive, with these two states containing over Compared to the signature of salt marshes of the 60% of all east coast salt marshes from Maine to middle and south Atlantic coasts and the Gulf of Florida (Reimold 1977). The following discussion Mexico, northeast salt marshes are small in spatial focuses on signatures of tidal marsh, seagrass, in- extent and often exist as narrow fringing systems. tertidal mudflat, and rocky intertidal habitats of The mean area of discrete marsh polygons in the northeast region. Maine is just 0.26 ha ( Jacobson et al. 1987), while

TABLE 2. Light extinction coefficients for estuaries along the Atlantic and Gulf of Mexico coasts of the U.S. As water clarity increases, extinction coefficient decreases.

Extinction Coefficient Estuary (mϪ1) Source Northeast Somes Sound, Maine 0.38–0.46 Roman and Doering unpublished data , Maine 0.45–0.72 Nixon 1986 Narragansett Bay, Rhode Island 0.58–0.76 Schenck and Davis 1973 Hudson River, New York 1.68–2.80 Sirois and Fredrick 1978 Middle Atlantic Delaware Bay, Delaware 0.3–7.0 Biggs et al. 1983 Chesapeake Bay 0.4–Ͼ2.0 Flemer 1970 Chesapeake Bay 1–5 Champ et al. 1980 Southeast Atlantic Core Sound, North Carolina 1.5–2.0 Thayer 1971 Fort Pierce Inlet, Florida 2.0–4.4 Thompson et al. 1979 Gulf of Mexico Charlotte Harbor, Florida 0.46–5.1 McPherson and Miller 1987 Barataria Bay, Louisiana 2.1 Nixon 1986 Sabine-Neches estuary, Louisiana/Texas 0.8–3.4 Bianchi et al. 1997 Northeast Atlantic U.S. Estuaries 749

along the Connecticut shoreline of the Long Is- northeast they are rare, except for the major river land Sound estuary the mean area is larger (39 ha; valley systems of the northeast (Odum et al. 1984). calculated from data provided in Niering and War- For example, brackish water tidal marshes domi- ren 1974), but still small when compared to south- nated by Typha angustifolia (narrow-leaved cattail) ern latitudes. Marshes in the Hudson River estuary and freshwater tidal marshes with Zizania aquatica range from saline to freshwater and are spread (wild rice), Pontederia cordata (pickerelweed), and along the 240 km tidal portion. Like other north- Scirpus pungens (common three-square) are com- east marshes, they are small with a mean area of mon along tidal reaches of the Connecticut River just 23 ha. The lack of a broad and relatively flat (Metzler and Tiner 1992) and Hudson River (Kiv- coastal plain tends to limit the areal extent of iat 1974). The rocky and steep-sided geomorphol- marshes in the northeast. While small salt marshes ogy of most tidal riverine systems throughout the dominate, there are some New England systems of northeast precludes the formation of extensive notable size that are associated with barrier island fresh and brackish tidal marshes (Odum et al. or spit systems (e.g., Scarborough Marsh, Maine; 1984). Most major rivers throughout the northeast Plum Island/Parker River marshes and Barnstable have been dammed and the effect of this altered Marsh, Massachusetts). hydrology and sediment transport on tidal fresh- The physiography and vegetation of northeast water wetland development remains unstudied. In tidal marshes has been described by many, but with addition to dams, most of the tidal marshes along most detail provided for southern New England the Hudson River occur behind a railroad em- salt marshes (Miller and Egler 1950; Redfield 1972; bankment that runs parallel to the river. Niering and Warren 1980; Nixon 1982). Here, a The geographically widespread effects of physi- distinct pattern of vegetation is observed, with a cal, human-caused, alterations on salt marshes is a narrow band of tall Spartina alterniflora occupying fundamental habitat signature in the northeast. the low marsh, areas flooded twice daily by tides, These impacts include filling, draining, mosquito and with high marsh areas flooded less frequently ditching, and alteration of tidal exchange by roads, and forming a mosaic of vegetation types that may dikes, impoundments, culverts, tide gates, and oth- include, Spartina patens, Distichlis spicata, short er structures. Prior to passage of coastal wetland form S. alterniflora, and Juncus gerardii. Salt marsh protection legislation by northeast states, begin- pannes, shallow depressions on the marsh surface ning in the 1960s, salt marsh losses due to filling often vegetated with forbs, and salt marsh pools were extraordinary. For example, in Connecticut can be present throughout the high marsh mosaic. 30–50% of tidal marshes have been lost (Metzler Descriptions of vegetation patterns on northern and Tiner 1992; Rozsa 1995). Thirty-five percent New England salt marshes are few, but differences of the United State’s coastal population (based on are apparent. The low marsh along the Maine census of coastal counties only) resides in the coast, north and east of Penobscot Bay, is domi- northeast (Maine to Virginia; Culliton et al. 1990) nated by S. alterniflora, but the high marsh has a and it is not surprising that a direct relationship greater diversity of plant species (Calhoun et al. between coastal wetland loss and population den- 1993). In addition to S. patens and J. gerardii, the sity has been noted (Gosselink and Baumann mosaic pattern of northern Maine salt marshes 1980). may include J. balticus, Festuca rubra, Agrostis gigan- Mosquito ditches represent one of the most tea, and Carex paleacea, among others. Along the common features on the northeastern salt marsh upland border of salt marshes throughout New with an estimated 90% of the marshes from Maine England and extending into southern Maine, to Virginia being ditched (Bourne and Cottam Phragmites australis commonly occurs; it has not 1950). In New England, salt marsh ditching began been noted in more northern salt marshes of during Colonial times, the 17th century, primarily Maine and the Bay of Fundy region ( Jacobson and to drain the marsh and enhance opportunities for Jacobson 1989; Calhoun et al. 1993; Chmura et al. salt hay farming, but became most prevalent in the 1997). The northern region of Maine may repre- 1930s when ditches were dug in an effort to sys- sent a transition to Bay of Fundy salt marshes tematically drain mosquito breeding areas. In the where vegetation zones of S. alterniflora, Plantago small marshes that dominate the New England maritima, S. patens, C. paleacea, and J. balticus are coast, ditches were often dug by hand, spanning noted (Pielou and Routledge 1976; Chmura et al. entire marshes in dense parallel grid patterns, with 1997). about 40–50 m spacing. Unditched salt marshes Extensive areas of freshwater and brackish water are rarely encountered in the northeast (Fig. 5). tidal marshes are a common signature of the upper Ditching, channelization, and impounding were reaches of river-dominated estuaries throughout common practices on marshes of the southeast and the middle and south Atlantic regions, but in the Gulf coast, but these practices were not nearly as 750 C. T. Roman et al.

dick et al. 1997). Numerous studies throughout New England have documented the hydrologic, vegetation, faunal, and biogeochemical responses of tidal marshes to restriction of tidal flow, and in turn, many successful efforts are underway to re- introduce tidal flow and restore the structure and function of degraded marshes (e.g., Roman et al. 1984; Sinicrope et al. 1990; Fell et al. 1991; Barrett and Niering 1993; Roman et al. 1995; Anisfeld and Benoit 1997; Burdick et al. 1997; Dionne et al. 1999; Portnoy 1999). Although not a direct human impact, like ditch- ing or tide restriction, rising sea level is a factor that has a strong influence on tidal marsh devel- opment processes. Several studies in the northeast report that rates of salt marsh accretion generally exceed rates of sea level rise, and thus, marshes are being maintained (Orson et al. 1987; Bricker- Urso et al. 1989; Wood et al. 1989; Orson and Howes 1992). Conversely, some marshes in the Chesapeake Bay (Stevenson et al. 1985) and large areas associated with the Mississippi delta region (Turner 1997) are becoming submerged and lost. Widespread submergence of northeast marshes is not reported; however, based on long-term trends in vegetation, Warren and Niering (1993) suggest that a Long Island Sound salt marsh may not be keeping up with sea level rise. On Cape Cod, an- other study found that sedimenation rate and rate of relative sea level rise were nearly similar, and like Fig. 5. Unditched (Nauset Marsh, Eastham, Massachusetts) and ditched salt marshes (Hammock River, Clinton, Connecti- the Long Island Sound marsh, vegetation patterns cut). Note the extensive network of tidal creeks and marsh pools indicate that the marsh is getting wetter, repre- on the unditched marsh. senting an initial response to wetland submer- gence (Roman et al. 1997).

all encompassing and extensive as encountered in SEAGRASSES the northeast. The effects of ditching include a Habitats dominated by seagrass and other sub- lowering of the marsh water table level, shifts in merged aquatic vegetation occur along the estua- vegetation, draining of marsh pools and pannes, rine gradient from marine to freshwater tidal por- and subsequent loss of preferred waterfowl and tions of northeast estuaries. Seagrass species of wildlife habitat (Daiber 1986). Today, ditches that northeast estuaries include eelgrass (Zostera mari- have been free from periodic maintenance clean- na) and widgeon grass (Ruppia maritima). Both spe- ing for many decades still remain as conspicuous cies have broad salinity tolerances, but Ruppia in features on the marsh landscape. the northeast commonly occurs in brackish to Restriction of tidal flow is a significant hydrolog- freshwater estuarine areas or in salt marsh pools ic signature of many northeast tidal marshes. (Richardson 1980; Thayer et al. 1984). Within Causeways and dikes that cross marshes often have freshwater or brackish water tidal portions of the inadequately sized culverts or bridges and tidal ex- relatively shallow Hudson and Connecticut River change is restricted. In addition to transportation estuaries, submerged aquatic vegetation can be ex- corridors, tidal flow was historically restricted to tensive (e.g., Ruppia, Vallisneria americana, Potamo- salt marshes throughout the northeast for salt hay geton perfoliatus). In the Hudson River, beds of sub- farming and mosquito control purposes, and flow merged vegetation, primarily Vallisneria, can occu- restriction was frequently exacerbated by tide py as much as 20% of the river bottom in areas gates. More recently, tide gates have been used for shallow enough for establishment and growth of flood protection. In New Hampshire, it is estimat- these light-limited plants (Harley and Findlay ed that 20% of the state’s salt marshes are presently 1994). degraded because of inadequate tidal flow (Bur- Zostera is the dominant seagrass of the northeast Northeast Atlantic U.S. Estuaries 751

TABLE 3. Percentage of the total area of estuarine habitat types classified as intertidal flat for several states in the northeast and mid-Atlantic coastal plain. Percentages for some specific estuaries or portions of shoreline are also presented. Classifications are according to the National Wetlands Inventory (Cowardin et al. 1979).

% of Total Estuarine Area Classified as Coastal State Intertidal Flat Source Northeast Maine 32 Fefer and Schettig 1980 Cobscook Bay/St. Croix estuary 50 Foulis and Tiner 1994a Mount Desert Island and vicinity 75 Calhoun et al. 1993 Casco Bay estuary 52 Foulis and Tiner 1994b Maine, New Hampshire, Massachusetts Gulf of Maine (York, Maine to Rowley, Massachusetts) 25 Foulis et al. 1994 Gulf of Maine (Plum Island, Massachusetts to Scituate, Massachusetts) 35 Foulis and Tiner 1994c Rhode Island 41 Tiner 1989 Connecticut 33 Metzler and Tiner 1992 Mid-Atlantic Coastal Plain New Jersey 17 Tiner 1985a Delaware 10 Tiner 1985b

often forming extensive underwater meadows. In lished in much of their historic habitat throughout terms of supporting detritus-based estuarine food the northeast (Conover 1961; Dexter 1985; Costa webs, it is estimated that six new leaf crops are pro- 1988), although some areas (such as parts of Nar- duced annually in a Cape Cod eelgrass meadow ragansett Bay) do not appear to have recovered (Roman and Able 1988). This high turnover con- (Short et al. 1993). tributes to estuarine detritus, including extensive A recurrence of the wasting disease occurred in areas of eelgrass wrack that dominate many estua- the 1980s (Short et al. 1986), with symptoms sim- rine shorelines throughout the northeast (e.g., Jos- ilar to those in the 1930s. Localized die-offs oc- selyn and Mathieson 1980; Thorne-Miller et al. curred along the east coast of the United States in 1983). upper Casco Bay, Maine; Great Bay, New Hamp- Historically, eelgrass grew in most of the bays shire; Stage Harbor, Massachusetts; and the Niantic and estuaries of the northeast (e.g., Cottam 1934; River, Connecticut. Although eliminated from the Renn 1934; Addy and Aylward 1944; Costa 1988). developed parts of estuaries and often fragmented The historic distribution of eelgrass in estuaries by human activity, eelgrass remains an important has been poorly documented, although it is likely and widespread estuarine habitat in the northeast. that eelgrass disappeared in the 19th century from With an increasing awareness of the values of many systems of the northeast as a result of land eelgrass habitat, every northeast coastal state has clearing, deforestation, and industrial develop- initiated restoration, with mixed success. Site selec- ment. For example, in Great Bay, New Hampshire tion, insuring sufficient water quality, and appro- extensive logging and operation of saw mills on priate geomorphological conditions are critical to most rivers entering the estuary created a deposi- restoration efforts (Fonseca et al. 1998). At a 2.5 tional layer of sawdust that likely eliminated eel- ha restoration site in the Great Bay estuary, eel- grass from many parts of the estuary (Short 1992). grass has survived for 6 years with plant and animal Such losses of eelgrass were generally localized and populations comparable to natural eelgrass beds related specifically to human activity. However, in (Short et al. 2000). Development and refinement the 1930s an epidemic disease threatened to elim- of planting methods (Orth et al. 1994; Davis and inate eelgrass from the northeast and elsewhere Short 1997), coupled with an emerging knowledge throughout the North Atlantic and Europe (Ras- of site selection criteria (Fonseca 1992; Davis et al. mussen 1977). This eelgrass decline, known as the 1998), will result in the long-term success of eel- wasting disease (Milne and Milne 1951), was a nat- grass habitat restoration efforts throughout the urally occurring disease event likely caused by the northeast. marine slime mold Labryrinthula zosterae (Muehl- stein et al. 1991). It devastated eelgrass popula- INTERTIDAL MUDFLATS tions, eliminating 90% of North Atlantic eelgrass. Intertidal flats are a common and extensive hab- Following the extensive wasting disease epidemic itat type in the northeast (Table 3). In some parts of the 1930s, eelgrass populations slowly reestab- of the Gulf of Maine, intertidal flats represent over 752 C. T. Roman et al.

50% of the total area of estuarine habitat types. At tuarine shores throughout the northeast (Topinka more southern latitudes, such as along the New et al. 1981; Bertness 1999). Productivity of rocky Jersey and Delaware estuarine shorelines, intertidal shore algae represents a dominant proportion of flats are less conspicuous, mainly because of re- total primary production in shallow systems in duced tidal range. Mudflats, the dominant type of Nova Scotia, Canada (Mann 1972, 1973). In the unconsolidated intertidal bottom in the Gulf of Great Bay Estuary, New Hampshire, Ascophyllum Maine, occur within protected areas often in as- and other fucoid algae are also reported to be valu- sociation with salt marshes, eelgrass meadows and able contributors to the estuarine detrital pool barrier systems. Over the long-term mudflats are ( Josselyn and Mathieson 1978; Chock and Mathie- depositional environments responding to rising son 1983). sea level, but on seasonal or daily time scales they Recent species introductions have had a dra- are both depositional and erosional features, re- matic influence on the ecology of northeastern sponding to tidal currents, waves, ice scour, and rocky shorelines, as well as other habitats. Bertness bioturbation (Anderson et al. 1981; Pethick 1996). (1984), studying the rocky cobble beaches of Nar- Mudflats support microalgal production, domi- ragansett Bay, found densities of the common per- nated by benthic diatoms (Whitlatch 1982) and iwinkle (Littorina littorea) in excess of 1,000 mϪ2 some are dominated by macroalgal mats. Welsh and reports grazing of all algae, except crustose (1980) reports dense mats of the green macroalga, forms. L. littorea, introduced in the mid 1800s, has Ulva lactuca, in association with a Long Island become the dominant intertidal herbivore along Sound estuary under a regime of high nutrient the northeast coast. Lubchenco’s (1980) classic loading. In a relatively undeveloped northern study clearly documents the role of L. littorea in Maine estuary, dense mats of the green filamen- controlling the structure of New England rocky in- tous macroalga, Enteromorpha intestinalis, have been tertidal communities. observed on mudflats, but the cause is unknown Another introduced species, the green crab (Vadas and Beal 1987). These microalgal and ma- (Carcinus maenus), is a predator on both rocky and croalgal primary producers, coupled with the in- soft-substrate habitats of the northeast, and like L. put of organic matter from adjacent habitats, play littorea has assumed an important role in shaping an important role in structuring and supporting a estuarine intertidal community structure. The is- rich benthic fauna. Fefer and Schettig (1980), sue of introduced species has become a serious Whitlatch (1982), and Reise (1985), among others, concern, to the point that the structure and func- provide excellent reviews on the role of tidal mud- tion of native estuarine communities in the north- flats in coastal detritus-based food webs. Tidal flats east are difficult to define (Bertness 1999). are closely linked to adjacent habitats such as salt marshes, eelgrass meadows, and open water. NURSERY ROLE OF NORTHEAST ESTUARINE Predators are especially important in shaping HABITATS benthic community structure and abundance in Salt marshes and seagrass meadows have long the mudflats. Bertness (1999), based on a litera- been recognized as providing essential habitat for ture review, has suggested that large mobile pred- economically-important species and/or serving as ators, such as blue crab (Callinectes sapadis) and an important nursery for marine species, yet most spot (Leiostomus xanthurus), predominate to the studies documenting nursery function have been south of Cape Cod. To the north, mobile predators from the mid-Atlantic and south. Young of the year are less abundant (especially blue crab which is ab- penaeid shrimp (Penaeus aztecus, Penaeus setiferus), sent) and infaunal predators, like polychaete an economically valuable species, commonly use worms, dominate. Comparing the role of predators salt marshes along the southeast Atlantic and Gulf in controlling benthic community structure and of Mexico coasts and are numerically abundant function of the biogeographically distinct regions compared to other nekton using the marsh (e.g., north and south of Cape Cod deserves further Turner 1977; Boesch and Turner 1984; Zimmer- study (Bertness 1999). man and Minello 1984; Kneib and Wagner 1994; McIvor and Rozas 1996). In Chesapeake Bay, it is ROCKY SHORELINES well-documented that Zostera beds support high Coupled directly to glacial history and geomor- densities of the commercially and recreationally phology, rocky shoreline habitats are perhaps the important blue crab (Heck and Thoman 1984). most unique habitat signature of northeast estu- Published quantitative studies for decapod utiliza- aries. This habitat is virtually absent along mid-At- tion of shallow estuarine systems in the northeast lantic, southeast, and Gulf of Mexico coasts of the are few; but a comparison of studies from Massa- U.S. Ascophyllum nodosum (knotted wrack) domi- chusetts to Texas does demonstrate that commer- nates the intertial rocky habitats of protected es- cially-important species, like blue crab and penaeid Northeast Atlantic U.S. Estuaries 753

shrimp begin to be numerically abundant in the Cape Cod (Heck et al. 1995). Regarding intertidal middle-Atlantic and south (Table 4). Although not mudflats in the northeast, commercial harvest of a numerically dominant decapod, American lob- soft-shelled clams (Mya arenaria) and baitworms ster (Homarus americanus) was collected from Cape (bloodworm, Glycera dibranchiata; sandworm, Nereis Cod eelgrass meadows (Heck et al. 1989), and in virens) is prevalent, especially in northern New the same estuary it was discovered that salt marsh England (Fefer and Schettig 1980). creek banks are used by American lobster as a Salt marshes, eelgrass beds, and mudflats of the nursery area for inshore populations (Able et al. northeast support commercially-harvested estua- 1988). We acknowledge that sampling methods rine fauna, but they also serve an especially im- and sampled habitats varied for the studies pre- portant role in providing habitat for forage species, sented in Table 4 and direct comparisons should which in turn support commercial and recreation- be made with caution; however, a trend does al fishes and coastal bird populations. This brief emerge suggesting a greater relative abundance of review of nursery role focuses on the intertidal and commercially or recreationally important deca- shallow water habitats that fringe northeast estu- pods using southern estuarine habitats when com- aries. Subtidal and deeper estuarine habitats also pared to northern latitudes. serve an important nursery function and support Regarding fishes using salt marsh and seagrass of commercial and recreational fisheries through- habitats as nursery areas, investigations from more out the region, including among others, American southern latitudes have found commercially im- lobster, hard clam (Mercenaria mercenaria), bay scal- portant species, such as spot (Leiostomus xanthu- lop, winter flounder, tautog, and anadromous fin- rus), mullet (Mugil curema), and bay anchovy (An- fish species. The shallow and emergent habitats of choa mitchilla), to be ranked as abundant (see ref- northeast estuaries serve an important link to the erences cited in Fig. 6 and Southeast and Gulf of deeper estuarine waters and habitats through the Mexico review by McIvor and Rozas 1996). Fishes estuarine detritus-based trophic structure. with life history strategies classified as nursery, ma- rine, diadromous, or transient visitor appear to Land Use and Nutrients represent a much greater percentage of fishes us- HISTORIC TRENDS ing shallow estuarine habitats from more southern latitudes. In shallow estuarine habitats of the There have been over two centuries of intense northeast, it is clear that resident fishes, such as development pressure within the northeast as evi- mummichogs (Fundulus heteroclitus) and stickle- denced by transformation of the landscape from backs (e.g., Gasterosteus aculeatus, Apeltes quadracus), deforested (1750–1860), extensive agriculture and seasonal residents (e.g., Menidia menidia) dom- (1790–1860), and then reforestation (1860 to the inate the fauna (Fig. 6). About 90% of fishes col- present; Fig. 7; Foster et al. 1992). This land clear- lected from northeast estuaries (from Maine to ing marked the start of the American Industrial New Jersey) were classified as resident, except for Revolution with the nation’s first mill established one site in southern Maine where the marine spe- in 1790 on the Blackstone River, Rhode Island, a cies sand launce (Ammodytes americanus) was dom- tributary to the Narragansett Bay estuary. With inant. land clearing and industry, contaminants were dis- New England and northeast salt marsh and eel- charged into northeast estuaries, as evidenced in grass habitats serve an important habitat function estuarine sediment records. In Narragansett Bay, for commercially and recreationally important nek- metals such as lead, chromium, and copper first ton species (e.g., menhaden, Brevoortia tyrannus; appeared in the sediment record by the early winter flounder, Pseudopleuronectes americanus; white 1800s, with pronounced increases beginning in the hake, Urophycis tenuis; herrings, Alosa aestivalis, Alo- 1850s as industrial activities accelerated (Bricker- sa pseudoharengus, Clupea harengus; American lob- Urso et al. 1989; Nixon 1995a). ster; and tautog, Tautoga onitis, among others; Nix- Regarding the history of nutrient loading to on and Oviatt 1973; Teal 1986; Heck et al. 1989; northeast estuaries, estimates were made of the av- Ayvazian et al. 1992; Dorf and Powell 1997), albeit erage annual loading of total nitrogen from water- not as abundant fauna like the blue crab, brown sheds, for the period of 1900 to 1994, and included shrimp or spot from more southern systems. In the contribution of various sources, including terms of commercial molluscs, eelgrass in the wastewater, atmospheric deposition, and agricul- northeast provides settlement substratum for spat tural runoff. The method for developing these his- and juvenile shellfish as noted for blue mussels torical reconstructions is presented elsewhere ( Ja- (Mytilus edulis; Newell et al. 1991; Heck et al. 1995; worski et al. 1997; Hetling et al. 1999) and only Grizzle et al. 1996) and bay scallops (Argopecten ir- briefly described here. The historical wastewater radians) in Great South Bay (Pohle et al. 1991) and flows were assumed to be proportional to water- 754 C. T. Roman et al. ng at least 90% of the Kneib and Wagner 1994 Zimmerman and Minello 1984 Peterson and Turner 1994 Heck and Thoman 1984 Rountree and Able 1992 Sogard and Able 1991 6 9 9 25 15 84 16 81 53 18 14 14 52 26 17 52 Weinstein 1979 55 Heck et al. 1989 66 29 35 33 30 100 Fell et al. 1998 catch) Source Relative (% of total Abundance (Green crab) 38 sp. (White shrimp) (Pink shrimp) (Brown shrimp) (Blue crab) (Grass shrimp) (Grass shrimp) (Sand shrimp) (Grass shrimp) Penaeus setiferus Palaemonetes pugio Penaeus setiferus Palaemonetes Penaeus setiferus Callinectes sapidus Palaemontes pugio Penaeus aztecus Penaeus setiferus Callinectes sapidus Callinectes sapidus Penaeus duorarum Penaeus aztecus Palaemonetes vulgaris Crangon septemspinosa Callinectes sapidus Carcinus maenas Palaemonetes pugio Palaemonetes vulgaris Crangon septemspinosa Crangon septemspinosa Palaemonetes vulgaris Crangon septemspinosa Hippolyte pleuracantha Salt marsh Seine Salt marsh Weir Eelgrass Enclosure trap Eelgrass Trawl Estuary Habitat Gear Species North Carolina New Jersey New Jersey Massachusetts Sapelo Island, GeorgiaCocodrie, Louisiana Salt marsh Salt marsh Flume weir Seine Galveston Bay, Texas Salt marsh Enclosure trap Cape Fear River, Great Bay-Little Egg Harbor, Great Bay-Little Egg Harbor, , Virginia Eelgrass Trawl Connecticut River, Connecticut Brackish Marsh Fyke net TABLE 4. Relative abundance of decapods collected from shallow estuarine habitats along a gradient from Massachusetts to Texas. Species representi Nauset Marsh Estuary, total decapod catch are presented. Habitats sampled and gear types used are variable as noted. Northeast Atlantic U.S. Estuaries 755

Fig. 6. Percent of total number of fishes that are classified as resident or seasonal resident species (after Ayvazian et al. 1992; Peterson and Turner 1994; Able et al. 1996), collected from several shallow estuarine salt marsh and eelgrass habitats from Maine to Texas. ME-1 ϭ Montsweag Bay (Targett and McCleave 1974); ME-2 ϭ Wells Harbor (Ayvazian et al. 1992); MA-1 ϭ Nauset Marsh (Heck et al. 1989); MA-2 ϭ Waquoit Bay (Ayvazian et al. 1992); MA-3 ϭ Great Sippewissett (Werme Fig. 7. Historic trends in percent forest cover in the state of 1981); MA-4 ϭ Slocum River (Hoff and Ibara 1977); RI ϭ Pet- Massachusetts and a portion of the Harvard Forest in central taquamscutt River and Point Judith Pond (Mulkana 1966); CT Massachusetts (redrawn after Foster 1992). ϭ Connecticut River (Fell et al. 1998); NY ϭ Great South Bay (Briggs and O’Connor 1971); NJ ϭ Great Bay-Little Egg Harbor (Rountree and Able 1992); VA ϭ York River (Heck and Tho- man 1984); NC ϭ Cape Fear River (Weinstein 1979); SC ϭ fold increase in atmospheric deposition as a source North Inlet (Cain and Dean 1976); LA ϭ Cocodrie (Peterson from 1900–1994 (Fig. 8a). A more urban water- and Turner 1994); TX ϭ Galveston Bay (Zimmerman and Mi- shed, such as Massachusetts Bay, revealed that nello 1984). wastewater inputs of total nitrogen dominated over time, as would be expected (Fig. 8b). An analysis of 10 watersheds along a latitudinal shed population, and for total nitrogen, the his- gradient from Maine to Virginia shows that total torical wastewater effluent concentrations were set nitrogen loading increased from about 200 to equal to current effluent concentrations. For total 1,000 kg N kmϪ2 yrϪ1 since 1900, with atmospheric phosphorus, wastewater effluent concentrations deposition clearly representing the largest anthro- have changed dramatically because of the chang- pogenic source to coastal watersheds ( Jaworski et ing composition of detergents, thus historical total al. 1997). Going back further in historic time to phosphorus effluent concentrations were estimat- pre-industrial conditions, Nixon (1997) has sug- ed from historical sampling data. By assuming the gested that atmospheric deposition of nitrogen current ratio of emissions to deposition has re- within the Narragansett Bay watershed was only 5% mained the same since 1900, historical nitrogen of present deposition. deposition loadings were computed from estimates The loading of total phosphorus from wastewa- of the historical emissions of nitrogen oxides to the ter discharges has changed dramatically over the atmosphere. Loadings from agricultural runoff past 95 years, as noted for the Merrimack River were estimated from animal census and fertilizer (Fig. 8c). With the introduction of high phospho- use data. Detailed presentations and discussions of rus detergents in the late 1940s phosphorus load- nutrient loading data, both historic and current, ing from wastewater facilities increased dramatical- are being prepared and are summarized here ly. The advent of low phosphorus detergents in the (Hetling and Jaworski in preparation; Jaworski and 1970s has resulted in the precipitous decline in re- Hetling in preparation). cent decades. The reconstructed riverine source apportion- In addition to determining historic nutrient ments in Fig. 8 are based on average annual inputs loading trends to northeast estuaries, we have re- and do not show the considerable variability of av- constructed the historic annual average concentra- erage annual loadings calculated from actual mon- tions of total nitrogen and total phosphorus enter- itoring programs. Regardless, the match between ing estuaries (i.e., point-of-entry concentrations) as observed loadings and average annual estimates is another means of studying the impact of human reasonable. Historic trends in total nitrogen for activity on estuarine nutrient status (Fig. 9). These the Merrimack River, Massachusetts show a four- concentration estimates were derived from average 756 C. T. Roman et al.

Fig. 8. Average annual nutrient loadings from various sources in kg of nutrient kmϪ2 of watershed per year, estimated for the period 1900 to 1994. Top panel: total nitrogen for Merrimack River. Middle panel: total nitrogen for Massachusetts Bay. Bottom panel: total phosphorus for Merrimack River. Northeast Atlantic U.S. Estuaries 757

Fig. 9. Average annual concentration of nutrients entering several northeast estuaries, reconstructed for the period 1900–1994. Top panel: total nitrogen. Bottom panel: total phosphorus. annual loadings, in kg kmϪ2 of watershed yrϪ1, di- taining atmospherically-deposited nitrogen ( Jawor- vided by the annual river discharge. The point-of- ski et al. 1997). entry nutrient concentrations do not include any Total phosphorus point-of-entry concentrations tidal dilution or dispersion. Total nitrogen point- in the estuarine plumes for the eight northeast sys- of-entry concentrations in eight northeast estuaries tems reached highest levels in the 1960s and have have increased by a factor of over three since 1900 declined since, reflecting detergent bans (Fig. 9b). (Fig. 9a). The estuaries to the north, in Maine, As with total nitrogen, the more urban estuaries in have lower average annual concentrations than the the southern portion of the region have higher more southern systems. It is noted that total nitro- concentrations. gen concentration in the more urban systems of the northeast appears to have leveled in recent de- CURRENT TRENDS cades, while concentration in the more northern Based on an assessment of coastal counties, the systems is increasing, presumably due to increased northeast (defined from Maine to Virginia by Cul- urbanization and atmospheric deposition. Maine liton et al. 1990) is the most densely populated watersheds, with high riverine flows, thin soils, and coastal region in the U.S. Sixteen percent of the short growing seasons may be less effective at re- entire national population resides within this nar- 758 C. T. Roman et al.

TABLE 5. Average annual loading (1988–1994) and relative sources (atmospheric, agricultural runoff, wastewater treatment facilities, background) of total nitrogen and total phosphorus loading to northeast estuaries compared to some mid-Atlantic coastal plain estuaries.

% Total N Source % Total P Source Total N Loading Total P Loading Estuary (kg kmϪ2 yϪ1) Atmos Agri Waste (kg kmϪ2 yϪ1) Agri Waste Backgd Northeast Less Developed Penobscot Bay, Maine 310 82 13 6 12 27 30 43 , Maine 372 77 12 11 25 25 36 39 Casco Bay, Maine 573 50 6 44 63 8 82 10 , Maine 387 82 8 10 22 19 35 45 Northeast Urban Massachusetts Bay, Massachusetts 1373 24 6 70 198 3 92 5 Buzzards Bay, Massachusetts 1373 33 8 59 139 6 87 7 Narragansett Bay, Massachusetts/ Rhode Island 1597 23 4 73 233 2 93 5 Long Island Sound, Connecticut/ New York 1571 29 11 61 143 11 83 7 New York/New Jersey Harbor 1882 27 15 58 253 12 84 4 Coastal Plain Delaware Bay, Pennsylvania/ New Jersey/Delaware 1825 34 22 45 124 31 60 8 Upper Chesapeake, Maryland 1083 48 36 17 44 36 45 18 Potomac River, Maryland 1245 36 36 28 58 72 21 7 Rappahannock River, Virginia 641 60 32 8 69 65 13 22

row fringe of northeast coastal counties. Over 60% charges, while almost 90% of the total phosphorus of the region’s total population, in 1990, lived with- loading to the urban northeast estuaries was from in coastal counties, representing just 25% of the wastewater treatment discharges. Agricultural in- region’s total land area. fluences dominated total phosphorus loadings to Related to the high population density, waste- the coastal plain estuaries. water strongly influences the current loading of nutrients to northeast estuaries (Table 5). Estuaries SHALLOW ESTUARINE SYSTEMS:NUTRIENTS AND to the south, along the mid-Atlantic coastal plain, HABITAT RESPONSES have a greater agricultural influence. For the pe- A shift from seagrass to macroalgal-dominated riod of 1988–1994, sources of total nitrogen and communities appears to be an increasingly recog- total phosphorus were quantified by combining nizable signature within shallow nutrient-enriched the source apportionment watershed loading data estuaries of the urban and urbanizing northeastern and wastewater effluent loading data that discharg- U.S. There is a clear relationship between in- es directly into tidal waters. The average annual creased housing density and decreased cover of total nitrogen loading flux, normalized by water- eelgrass at the Ninigret Pond, Rhode Island and shed area, for the estuaries in Maine was 410 kg Waquoit Bay, Massachusetts shallow estuarine em- kmϪ2 yrϪ1, while the average loading for the more bayments (Fig. 10; Short et al. 1996; Short and Bur- urban estuaries from Massachuestts Bay to New dick 1996). With increased housing density, cor- York/New Jersey Harbor was substantially greater, responding increased nutrient loading, and de- 1,560 kg kmϪ2 yrϪ1. About 65% of total nitrogen creased eelgrass cover, there is an increase in ma- loading for the urban estuaries was from municipal croalgal biomass at these two southern New wastewater discharges. In contrast, atmospheric de- England systems (Thorne-Miller et al. 1983; Valiela position represented over 70% of total nitrogen et al. 1992; Peckol and Rivers 1996). Similarly, Kin- loading to the Maine estuaries. Agricultural runoff ney and Roman (1998) have documented the re- represents less that 10% of total nitrogen loading lationship between increased nutrient loading and for all of the northeast estuaries, while for the the conversion of a Ruppia-dominated shallow es- more southern coastal plain estuaries agriculture tuary in Maine to green macroalgae, and along has a much greater influence on total nitrogen Connecticut’s Long Island Sound shoreline the loadings, often exceeding 30% of all sources (Ta- green macroalga, Ulva lactuca, often dominates in ble 5). shallow nutrient enriched embayments (Mumford As would be expected, total phosphorus loading Cove, see Harlin 1995). Competition for light is a for the Maine estuaries averaged 30 kg kmϪ2 yrϪ1 key factor responsible for the seagrass declines un- with about 59% from municipal wastewater dis- der nutrient enriched conditions (Short et al. Northeast Atlantic U.S. Estuaries 759

shorelines are common from New York to south- eastern Massachusetts and concentrations of groundwater-delivered nitrate can be exceptionally elevated within developed watersheds, in excess of 400 ␮M (Table 6). In contrast to sandy shorelines, as groundwater discharges through highly organic intertidal/subtidal sediments, removal of nitrate by denitrification would be expected before discharge to estuarine waters (Valiela and Teal 1979; Capone and Bautista 1985; Howes et al. 1996).

Summary Statements that highlight typical characteristics of estuaries for discrete geographic regions should Fig. 10. Relationship between housing density and eelgrass at Ninigret Pond, Rhode Island (data from Short et al. 1996). be made with caution because there are always ex- ceptions. For the northeastern U.S. general or common signatures of estuaries are evident, but 1995; Taylor et al. 1995). Light limitation of en- since the geomorphology is so complex, ranging riched seagrass communities can also be attributed from bedrock-dominated shores to sand-dominat- to phytoplankton blooms and seagrass epiphyte ed barriers, there are many exceptions to the typ- growth (Ryther and Dunstan 1971; Harlin 1995). ical northeast estuary. Acknowledging this variabil- Pathways of nitrogen delivery to estuarine sys- ity, northeast estuaries are relatively deep when tems include atmospheric deposition, river dis- compared to more southern systems along the charge, oceanic fluxes, and groundwater, while coastal plain, tidal range is high, drainage basins most significant sources of nitrogen may include are small and forested, leading to low riverine atmospheric contamination, wastewater from treat- freshwater flows and low suspended sediment ment facilities or on-site septic systems, and fertil- loads. Tidal marshes are small in area and often izer use (Nixon 1995b; Jaworski et al. 1997; Valiela occur as fringing systems. Resident fishes, includ- et al. 1997). In shallow estuarine systems through- ing mummichogs, sticklebacks, and silversides, out the northeast, especially within watersheds dominate shallow estuarine habitats of northeast dominated by highly permeable sand/gravel gla- estuaries (salt marshes, eelgrass meadows). Related cial outwash aquifers, groundwater is a dominant to the high tidal range, intertidal mudflats are ex- source of freshwater and associated nitrate contam- tensive in northern New England. Compared to ination (Valiela et al. 1990; Short et al. 1996; Port- mid-Atlantic, southeast, and Gulf of Mexico coasts, noy et al. 1998). In some shallow southern New rocky shorelines are a unique feature of northeast England estuaries, over 80% of total inorganic ni- estuaries and a direct result of the region’s glacial trogen inputs are from groundwater discharge (Ta- history. Urban land use is a striking feature of ble 6). There is minimal removal of nitrate as northeast estuarine watersheds, especially from groundwater discharges from highly permeable Boston to New York. In response, nutrient enrich- watersheds into estuarine shorelines that have ment is an increasingly recognizable signature, es- sandy and low organic sediments, with little or no pecially within shallow estuarine embayments of fringe of salt marsh (Valiela and Costa 1988; Giblin the region. and Gaines 1990; Nowicki et al. 1999). These Understanding fundamental characteristics or

TABLE 6. Role of groundwater in delivering nitrate to shallow estuarine systems of southern New England. * denotes average range from several sites.

% of Total Freshwater % of Total Input by N Inputs by Groundwater Nitrate Estuary Groundwater Groundwater Concentration (␮M) Source Rhode Island Salt Ponds, Rhode Island 88 Lee and Olsen 1985 Buttermilk Bay, Massachusetts 85 0.2–450 Valiela and Costa 1988 318–431* Weiskel and Howes 1992 Waquoit Bay, Massachusetts 89 Cambareri and Eichner 1998 0.3–352 Valiela et al. 1990 Little Pond, Massachusetts 95 Milham and Howes 1994 Nanset Marsh, Massachusetts 6–203* Portnoy et al. 1998 760 C. T. Roman et al. signatures of estuaries from throughout the U.S. on salt marshes: An instance of acidification. Environmental coastal zone, and other areas worldwide, is espe- Science and Technology 31:1650–1657. AYVAZIAN, S. G., L. A. DEEGAN, AND J. T. FINN. 1992. Comparison cially important to recognizing unique processes, of habitat use by estuarine fish assemblages in the Acadian trends, or forcing functions that define particular and Virginian zoogeographic provinces. Estuaries 15:368–383. regions. For example, deep estuarine basins are BARRETT,N.E.AND W. A. NIERING. 1993. Tidal marsh restora- unique to northeast estuaries. What are the eco- tion: Trends in vegetation change using a Geographical In- logical linkages between these basins and shallow formation System (GIS). Restoration Ecology 1:18–28. BERTNESS, M. D. 1984. Habitat and community modification by estuarine habitats, such as seagrass beds, marshes, an introduced herbivorous snail. Ecology 65:370–381. and mudflats? Rocky shores, dominated by ma- BERTNESS, M. D. 1999. The Ecology of Atlantic Shorelines. Sin- croalgae, are common throughout the northeast, auer Associates Inc., Sunderland, Massachusetts. and in some estuaries may represent the dominant BIANCHI, T. S., M. BASKARAN,J.DELORD, AND M. RAVICHANDRAN. 1997. Carbon cycling in a shallow turbid estuary of southeast shallow water habitat. The relative contribution of Texas: The use of plant pigment biomarkers and water quality these habitats to total system primary production parameters. Estuaries 20:404–415. needs to be quantified. And what is the nekton BIGGS, R. B., J. H. SHARP,T.M.CHURCH, AND J. M. TRAMONTANO. support function of these rocky habitats? Within 1983. Optical properties, suspended sediments, and chemis- the northeast region, Cape Cod is a major biogeo- try associated with the turbidity maxima of the Delaware Es- tuary. Canadian Journal of Fisheries and Aquatic Sciences 40:172– graphic boundary between boreal species and tem- 179. perate/southern species. How will global climate BOESCH,D.F.AND R. E. TURNER. 1984. Dependence of fishery change, and associated alteration of physical char- species on salt marshes: The role of food and refuge. Estuaries acteristics of northeast estuaries, influence species 7:460–468. composition and abundances along this biogeo- BOOTHROYD, J. C., N. E. FRIEDRICH, AND S. R. 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