The Status of Eelgrass, Zostera marina, as Bay Scallop Habitat: Consequences for the Fishery in the Western Atlantic

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Authors Fonseca, Mark S.; Uhrin, Amy V.

Download date 28/09/2021 11:17:50

Link to Item http://hdl.handle.net/1834/26298 The Status of Eelgrass, Zostera marina, as Bay Scallop Habitat: Consequences for the Fishery in the Western Atlantic

MARK S. FONSECA and AMY V. UHRIN

Description of the Plant The plant is almost always submerged Relatively thin, flattened, blade-like or partially floating at low tide. In the leaves up to ~ 1 cm in width, dark Zostera marina L. is one of a small western Atlantic it is only occasionally green in color; genus of widely distributed seagrasses, intertidal (Fig. 2). all commonly called eelgrass (Fig. 1). However, eelgrass is actually not a Leaves usually 20–50 cm but up to This genus contains twelve grass—it is in the same Class grouping 2 m in length, 4–10 mm wide, with worldwide but only three species are as other monocotyledonous plants, but it 5–11 veins and rounded leaf tips, found in (Z. asiatica then branches into strictly aquatic plant sometimes with a very small, sharp and Z. japonica on the west coast) with groups at lower taxonomic levels: point; Z. marina as the only confirmed native species. Eelgrass is found on sandy Phylum: Anthophyta (flowering Leaf sheath forms an envelope around substrates or in estuaries, and rarely plants), the aboveground stem; on the open ocean coastline and then, Class: Liliopsida (monocots), usually, in the shelter of boulders or Order: Potamogetonales, Reproductive shoot, terminal, other similarly immobile structures. Family: Zosteraceae (Greek ‘zoster,’ branched, and substantially longer meaning ‘belt’), than vegetative shoots; Genus/species: Zostera marina. Authority: Linnaeus, 1758. Seeds ovoid or ellipsoid, ~2–3 mm Mark S. Fonseca and Amy V. Uhrin are with the U.S. Department of Commerce, NOAA, National long with 16–25 distinct ribs; Ocean Service, Center for Coastal and Fisheries A summary of the key identification Habitat Research, 101 Pivers Island Road, Beau- features are as follows: Rhizome color (when living) is fort, NC 28516 (email: Mark.Fonseca@noaa. gov). dark brown and has a polished appearance;

At each rhizome node, there are typi- ABSTRACT—Zostera marina is a mem- Today, increased turbidity arising from cally two root bundles; ber of a widely distributed genus of sea- point and non-point source nutrient load- grasses, all commonly called eelgrass. ing and sediment runoff are the primary Branching is alternate along the The reported distribution of eelgrass along threats to eelgrass along the Atlantic coast the east coast of the United States is from and, along with recruitment limitation, are rhizome and frequently irregular; Maine to North Carolina. Eelgrass inhabits likely reasons for the lack of recovery by each branch becomes an independent a variety of coastal habitats, due in part to eelgrass to pre-1930’s levels. Eelgrass is shoot. its ability to tolerate a wide range of envi- at a historical low for most of the western ronmental parameters. Eelgrass meadows Atlantic with uncertain prospects for sys- provide habitat, nurseries, and feeding tematic improvement. However, of all the To the casual observer there is little grounds for a number of commercially and North American seagrasses, eelgrass has morphological difference between the ecologically important species, including a growth rate and strategy that makes it two seagrass species that co-occur with the bay scallop, Argopecten irradians. In especially conducive to restoration and eelgrass in the western Atlantic, shoal the early 1930’s, a marine event, termed several states maintain ongoing mapping, grass, Halodule wrightii Aschers, and the “wasting disease,” was responsible for monitoring, and restoration programs to catastrophic declines in eelgrass beds of enhance and improve this critical resource. widgeon grass, Ruppia maritima L. the coastal waters of North America and The lack of eelgrass recovery in some However, the three species can be distin- Europe, with the virtual elimination of Z. areas, coupled with increasing anthropo- guished particularly by their blade tips marina meadows in the Atlantic basin. Fol- genic impacts to seagrasses over the last and rhizomes (Fig. 3). The leaf tip of lowing eelgrass declines, disastrous losses century and heavy fishing pressure on scal- were documented for bay scallop popula- lops which naturally have erratic annual eelgrass is round, sometimes with a very tions, evidence of the importance of eel- quantities, all point to a fishery with pro- small apical point, whereas H. wrightii grass in supporting healthy scallop stocks. found challenges for survival. has a bicuspidate (crowned) appearance

20 Marine Fisheries Review Figure 3.—Sketches of blade tips for the three cogeners. Reproduced from Thayer et al., 1984.

left behind, rooted in place as with the other seagrass species—instead the terminal shoot actually migrates across the seafloor leaving a trail of rhizome rooted in place behind it which gives the plant unusual pattern development Figure 1.—Zostera marina (eelgrass) showing the whole plant structure. capabilities and high spatial recoloniza- tion rates. The life history of eelgrass has been well-described for almost a century (Setchell, 1929). The plant typically follows a 2-year (perennial) life his- tory (Fig. 4). For most of the range in the western Atlantic, eelgrass seeds germinate in the late winter and grow vegetatively through the summer, cre- ating daughter shoots (ramets) almost continuously every 2–4 weeks. These clones then over-winter in a slow growth phase. In the second year of their existence, shoots of that age undergo a dramatic alternation of generation and transform into luxurious flowering structures that produce dozens of seeds. After setting seed, the shoot dies. Seeds tend to stay very near the parent plant yet the role of seeding in eelgrass bed maintenance remains somewhat of a mystery. Like terrestrial plants, there appears to be “mast years” where extraordinary Figure 2.—Eelgrass bed in Long Island Sound (Photograph by C. Pickerell). numbers of seedlings germinate which can result in significant new bed forma- tion in locations otherwise long devoid and R. maritima is lancelate (pointed). Eelgrass is unlike all the other native of cover. Flowering stalks can break off Also, the living rhizome of eelgrass is North American seagrass species in and float for many miles (Phillips and brown while the rhizomes of the other that each seagrass shoot is a “terminal Meñez, 1988; Harwell and Orth, 2002), species are much lighter, almost white shoot”; that is, it is always located at the providing a means for colonization at far depending on sediment type. end of the rhizome. There are no shoots distant locations.

71(3) 21 Figure 4.—Stylized life history of perennial eelgrass. Redrawn from Setchell, 1929.

Limiting Factors its upper limit. The emersion tolerance irradiance (Dennison, 1987; Gallegos, of eelgrass is not well quantified, but 1994) but these values are undergoing Eelgrass inhabits a wide range of observations indicate that it has a low re-evaluation (Kenworthy2). Depth dis- coastal habitats, due in part to its ability desiccation tolerance and thus cannot tribution of eelgrass varies with water to tolerate a wide range of environmen- withstand prolonged exposure at low quality on a local scale. For example, tal parameters. These parameters are tide unless the environment is cool (typi- in both Chesapeake Bay and the North discussed in more detail below. cally below 20°C) and a film of water Carolina coastal zone, where waters can persists to keep the plant wetted. When be turbid, eelgrass is usually limited Substrate exposed to truly dry conditions and a to depths of 2 m or less (Dennison et Eelgrass is limited to unconsolidated mild breeze, eelgrass blades can desic- al., 1993; Ferguson and Korfmacher, sediments, and thus, comparatively cate beyond recovery in minutes while 1997; Fonseca et al., 2002; Kemp et quiescent environments. However, luxu- the sheath bundle, which contains the al., 2004). In contrast, further north, rious eelgrass beds may be found cling- meristems, may withstand much longer estuaries become less turbid and light ing to cobble sediments behind highly periods of true desiccation (Fonseca1). is able to penetrate to greater depths, exposed islands along the New England Eelgrass is generally limited to depths with eelgrass growing in excess of 10 coast. where light is at least 15–25% of surface m in some areas (Maquoit Bay, ME: Light / Depth 1Fonseca, M. Unpubl. data. NOAA, Center for 2Kenworthy, J. NOAA, Center for Coastal Fish- Eelgrass is limited in its depth distri- Coastal Fisheries and Habitat Research, Beau- eries and Habitat Research, Beaufort, N.C. Per- bution by light at depth and emersion at fort, N.C. sonal commun., 2009.

22 Marine Fisheries Review Short and Short, 2003; Fort Weatherall, Jamestown, R.I.: Fonseca1). Moreover, the periodicity of light-reducing events (acute versus chronic diminishment of light) may play a significant yet diffi- cult-to-detect role in the distribution of eelgrass. Moore et al. (1997) found that a month-long elevated turbidity event at a site in Chesapeake Bay caused eelgrass to die off, an event that was otherwise very difficult to detect using data aver- aged over longer periods of time. Temperature Due to its widespread distribution, eelgrass can experience water tempera- ture fluctuations from less than 0°C to greater than 30°C. Although eelgrass may grow at temperature extremes, physiological processes within the plant (i.e. photosynthesis, respiration) require a more limited range for optimum performance (Fig. 5; Penhale, 1977; Evans et al., 1986, Marsh et al., 1986). Although there are a number of factors to consider, it is widely considered that Figure 5.—Graphic illustration of Setchell’s topology describing the relationship a sustained temperature approaching between temperature and eelgrass phenology. Redrawn from Setchell, 1929. 25°C is the upper tolerance limit for eelgrass (Zimmerman et al., 1989; Bintz et al., 2003). through the meadow, eelgrass shoots Nutrients wave in synchrony with the passing Water Motion crests (Grizzle et al., 1996) and troughs Eelgrass growth, abundance, and Eelgrass beds thrive in areas of and create drag that diminishes waves morphology are clearly linked to avail- moderate to high current speeds and rapidly especially if the plants occupy able nutrient pools (Short 1983a, b, can withstand current speeds of up to most of the water column. Under tidal 1987). In the siliceous sedimentary en- 1.5 m/s (Fonseca and Fisher, 1986; currents, an eelgrass canopy will bend vironment typical of temperate eelgrass Koch, 2001). Water motion plays a into a compact layer as current veloci- beds, plants appear to be nitrogen lim- role in structuring eelgrass meadows ties increase. By deflecting water over ited (Short, 1987 and references therein) (Fonseca and Bell, 1998). Scouring by it, the canopy shields the bottom from but typically have ample supplies of waves and currents at the leading edges erosive forces. phosphorous (McRoy and Barsdate, of a meadow can erode sediments and 1970; McRoy et al., 1972). Nutrients plants and prevent sediment deposition. Salinity are absorbed from the sediment and In some instances, large quantities of Eelgrass is euryhaline; it has been re- associated interstitial water at the roots sediment may actually be carried off ported from areas experiencing periods and are subsequently transferred to the and deposited, burying significant por- of nearly fresh water to full-strength sea- rest of the plant. In addition, plant leaves tions of existing meadows which have water or greater (Thayer et al., 1984). An are able to absorb nutrients from the limited burial tolerance (covering ~50% optimum salinity for this species has, to water column. of the leaves kills the plants; Mills and our knowledge, never been determined, Fonseca, 2003). but photosynthesis virtually ceases The Wasting Disease Eelgrass is effective in damping out below 10‰ and is probably optimal at In the early 1930’s, a marine event of waves and reducing current veloci- oceanic salinity levels (approximately near catastrophic proportions occurred ties within the canopy as water passes 32‰). Given the generally estuarine in eelgrass beds of the coastal waters through the meadow, especially when distribution of eelgrass, the importance of North America and Europe. Within the canopy extends to the water’s sur- of periodic freshwater events may play a two years of its first observation, the face (Fonseca et al., 1983; Fonseca significant role in periodically resetting “wasting disease,” as it was termed, and Cahalan, 1992). As a wave passes its distribution. had eliminated over 90% of eelgrass

71(3) 23 populations worldwide (Muehlstein, seaboard, catastrophic population Distribution 1989). Total losses along the Atlantic declines were documented for bay coast of the United States cannot be scallop, Argopecten irradians, popula- Throughout its range along the North quantified as systematic documentation tions (see review in MacKenzie, 2008). American east coast, eelgrass is the of eelgrass distribution did not exist Following the wasting disease event, dominant species of rooted submerged prior to the 1930’s. Although often eelgrass and bay scallops were absent aquatic vegetation (SAV). The reported suspected, decades later the marine from Nantucket Harbor for nearly 20 distribution of eelgrass along the east slime mold, Labyrinthula zosterae, was years (Andrews, 1990) and scallop coast of the United States is from Maine suggested as the responsible pathogen landings reached an all-time low for to North Carolina (Fig. 6 and 7). Cur- (Muehlstein et al., 1991). However, the the Long Island, New York fishery rent estimates of eelgrass cover range actual conditions leading to the wide- (MacKenzie, 2008). In Rhode Island, from 6.75 km2 in Connecticut to nearly spread outbreak have never been clearly a tremendous harvest of scallops was 160 km2 in Massachusetts (Table 1). determined. One long-held contention described from “The Cove” at the north When other SAV species are included, is that climatic shifts, particularly a end of Aquidneck Island both in 1956 cover increases to ~500 km2 (Table 1). sudden increase in water temperature and again ~ 1959; intense dredging Eelgrass populations are characterized and reduced incoming solar radiation apparently destroyed the eelgrass beds by spatially and temporally fluctuat- in the 1930’s led to increased suscep- in this water body and scallops were ing levels of abundance which is to be tibility of eelgrass to infection through no longer found after that time (Ca- expected for a plant that is a prolific the influence of these abiotic factors vanaugh3). Commercial harvest of the seed-setter and has a life history of only on seagrass metabolism and photobiol- bay scallop fell precipitously in North two years. Dynamic coverage has been ogy (Tutin, 1938; Rasmussen, 1977). Carolina and Chesapeake Bay (Thayer well documented for many years (den The controversy over the cause of the and Stuart, 1974; Orth and Moore4). In Hartog, 1971) and is strongly associated wasting disease, particularly in lieu of North Carolina, populations returned with disturbance regime; for example, numerous studies regarding thermal to near pre-event levels in the 1960’s, prior to the wasting disease, there is tolerance and light requirements of Z. but have fluctuated dramatically since evidence that eelgrass had previously marina, and a paucity of good meteoro- that time. Moreover, North Carolina disappeared from many portions of the logical data for the early 20th century, populations have exhibited a steady U.S. Atlantic coast in 1893–94, largely is debated even today. decline since 1995 to such a degree that due to an extremely cold period, with Eelgrass recovery was not apparent the main harvest season was not opened additional losses along New England before the mid 1950’s. By the 1960’s, in January 2006 and remained closed coasts in 1908 (Cottam, 1934, 1935). eelgrass populations had generally through 2009 (Burgess and Bianchi5; However, losses at that time were appar- re-established and 30–40 years later NCDMF6,7), although this does not ently nowhere comparable to the loss of had largely recovered, although many appear to be the result of concomitant eelgrass in the 1930’s. locations which once supported thriv- changes in eelgrass abundance. Bay As coastal development accelerated ing eelgrass habitat have never re- scallop populations in Chesapeake in the post WWII economic boom of colonized (Short et al., 1988, 1993; Bay have never been restored to com- the United States, the depleted eel- Short and Short, 2003). It is believed mercially harvestable levels since the grass populations beginning to recover that those populations inhabiting lower decline of the 1930’s (MacKenzie, from the 1930’s event were faced with salinity environments (upper reaches 2008; Orth and Moore4). deteriorating water quality, increased of estuaries) were able to avoid infec- physical disturbance from vessels and tion and thus provide a stock of plants fishing, and even potential impacts from 3Cavanaugh, D. (deceased) Fisherman, Ports- for recovery as salinity clearly plays a mouth, Rhode Island. Personal commun., 1972. invasive species (e.g. European green role in regulating L. zosterae activity, 4Orth, R., and K. Moore. 1982. The biology and crab, Carcinus maenas; and mute swan, with reduced activity below 20–25‰ propagation of Zostera marina, in the Chesa- Cygnus olor). As a result, eelgrass is at peake Bay, Virginia. Final Rep. to U.S. Environ. (Muehlstein et al., 1988, Burdick et Protect. Agency, Chesapeake Bay Program pur- a historical low for most of the region al., 1993). Although a large-scale event suant to Grant No. R805953, 195 p. with uncertain prospects for systematic akin to that of the 1930’s has not oc- 5Burgess, C., and A. Bianchi. 2004. An eco- improvement. As suggested by MacK- nomic profile analysis of the commercial fishing curred in recent history, symptoms and industry in North Carolina including profiles for enzie (2008) the lowered abundance of epidemiology of this alleged disease state-managed species. N. C. Dep. Environ. Nat. eelgrass has direct and negative impli- have manifested themselves in local Resour., Div. Mar. Fish. Morehead City, Unpubl. cations for the scallop fisheries in the eelgrass populations in the mid 1980’s rep., 228 p. western Atlantic given this plant is his- 6N.C. Dep. Environ. Nat. Resour., Div. Mar. Fish. and may be associated with some small- 2008. Stock status of important coastal fisheries torically a critical substrate for scallop. scale die-offs (Short et al., 1986, 1987, in North Carolina. http://00de17f.netsolhost. 1988). com/stocks/index.html Maine 7N.C. Dep. Environ. Nat. Resour., Div. Mar. Fish. Following the virtual elimination of 2009.Proclamation SC-1-2009. http://00de17f. Information regarding the historical Z. marina meadows along the eastern netsolhost.com/procs/procs2k9/SC-1-2009.html distribution of eelgrass in Maine prior

24 Marine Fisheries Review Figure 6.—Eelgrass distribution along the north Atlantic coast of the United States: Maine to New Jersey. Reprinted with per- mission from Green and Short (2003). Copyright (2003) by the UNEP World Conservation Monitoring Center. Published by the University of California Press.

Figure 7.—Eelgrass distribution along the mid Atlantic coast of the United States: Delaware to North Carolina. Reprinted with permission from Green and Short (2003). Copyright (2003) by the UNEP World Conservation Monitoring Center. Published by the University of Cali- fornia Press. to the wasting disease is scarce. Cottam that, “Though marked improvement eelgrass maps for Maine (utilizing data (1934) documented a fisherman’s has occurred in many places in this from 1992–2005) are available through account that most of the eelgrass in state during the past two or three years, the MEDMR website (MEDMR9). The Penobscot Bay had disappeared during eelgrass is still far below former preva- greatest area of eelgrass is found in 1893–94 and that many years passed lence, varying from absent or scarce to Casco Bay, particularly the northern before it returned. It would appear that moderately abundant.”Documentation region, where it appears to be at or near Maine eelgrass populations suffered as of eelgrass distribution is generally lack- elsewhere in 1908 and following the ing after the 1950’s, up until the early 8Barker, S. State of Maine, Department of 1930’s wasting disease event (Cottam, 1990’s when the Maine Department of Marine Resources, Boothbay Harbor. Personal 1934). In reference to post-1930’s recov- Marine Resources (MEDMR) began commun., 2009 ery, Cottam and Munro (1954) reported mapping efforts (Barker8). Current 9MEDMR http://www.maine.gov/dmr/index.htm

71(3) 25 Table 1.—Reported eelgrass coverage along the eastern seaboard of the United States. *dominated by Z. marina and of New Hampshire, continues to survey R. maritima but also includes additional species of SAV; **includes shoal grass, Halodule wrightii, and R. maritima. eelgrass cover in the GBE on an annual State Year Area (km2) Source basis. Additional information can be 13 Maine 1992–2005 126.08 Barker1 found at the NHEP website. New Hampshire 2006 8.0 NHEP2 Massachusetts 1995–2001 137.86 Costello3 Massachusetts Rhode Island 2006 1.88 Bradley et al.4 Connecticut 2006 6.75 Tiner et al., 2007 Nautical charts and herbarium records New York (Peconic Estuary, Long Island Sound) 2001, 2006 7.20 Tiner et al., 2007; PEP5 from the mid 1800’s through the 1920’s New Jersey (Barnegat Bay, Little Egg Harbor) 1999 60.83 Lathrop et al., 2001 Delaware 2008 0.01 Anderson6 document the prevalence of eelgrass Maryland Coastal Bays 2007 27.60* Orth et al.7 in rivers, embayments, and nearshore Chesapeake Bay + tributaries 2007 262.71* Orth et al.7 Virginia Coastal Bays 2007 16.03* Orth et al.7 coastal environments north of Boston North Carolina 1985–1992 500** Ferguson et al., 1991, 1993; as well as extensive eelgrass meadows Ferguson and Wood8; NOAA9, 10, 11 throughout Boston Harbor and further 1 Barker, S. State of Maine, Department of Marine Resources, Boothbay Harbor. Personal commun., 2009 south in Duxbury, Plymouth, eastern 2 New Hampshire Estuaries Project (NHEP). 2006. 2006 State of the Estuaries. Durham, 32 p. Cape Cod Bay, Waquoit Bay, and Buz- 3 Costello, C. 2007. MassDEP Eelgrass Mapping Program, 1994–2007.Unpubl. rep., State of Mass., Dep. Environ. Protect., 14 Boston. zards Bay (Colarusso ). Eelgrass loss 4 Bradley, M., K. Raposa, and S. Tuxbury. 2007. Report on the analysis of true color aerial photography to map and inventory was documented in Massachusetts Zostera marina L. in Narragansett Bay and Block Island, Rhode Island. Environ. Data Ctr., Univ. Rhode Island, unpubl. rep., 17 p. + Eelgrass Atlas. during the 1893–94 cold snap and again 5 Peconic Estuary Program (PEP), Yaphank, NY. Unpubl. data in 1908 (Cottam, 1934, 1935). Follow- 6 Anderson, B. State of Delaware, Department of Natural Resources and Environmental Control, Dover. Personal commun., 2009. ing the near elimination of eelgrass 7 Orth, R. J., D. J. Wilcox, L. S. Nagey, A. L. Owens, J. R. Whiting, and A. K. Kenne 2008. 2007 Distribution of submerged during the 1930’s, Addy and Aylward aquatic vegetation in Chesapeake Bay and Coastal Bays.Virginia Inst. Mar. Sci., College of William and Mary, Gloucester Point, VIMS Special Scientific Report No. 151 pursuant to U.S. Environ. Prot. Agency Award #CB973013-01-0. (1944) recounted, “Eelgrass is returning 8 Ferguson, R., and L. Wood. 1994. Rooted vascular beds in the Albemarle–Pamlico estuarine system. Albemarle–Pamlico in substantial amounts at many points Estuarine Study Report No. 94-02, 108 p. 9 National Oceanic and Atmospheric Administration. 1994. SAV habitat from Ocracoke Inlet to Pea Island, North Carolina. along the Massachusetts coast and has NOAA, Center for Coastal Fisheries and Habitat Research, Beaufort, N.C. Unpubl. GIS data steadily increased during the past four 10 National Oceanic and Atmospheric Administration. 1992. Submerged aquatic vegetation of Bogue Sound, North Carolina 1992. NOAA, Coastal Services Center, Charleston, N.C., Unpubl. GIS data years, but is not as abundant anywhere as 11 National Oceanic and Atmospheric Administration. 1990. Core Sound, North Carolina Composite SAV Data Set 1985– before 1930.” Observations by Cottam 1990. NOAA, Coastal Services Center, Charleston, N.C., Unpubl. GIS data. and Munro (1954) highlight the spatial and temporal variability of the recovery its maximum areal distribution cover- ceded, accompanied by a decline in total process, “In some of these areas the ing much of the lower intertidal and eelgrass biomass (NHEP11), ostensibly plant is so plentiful as to impede boat shallow subtidal areas (Neckles et al., due to rapidly declining water quality travel and hinder commercial fishing. 2005; CBEP10). Commercial fishing (nutrient loading and sedimentation; Least improvement is reported in the activities contribute to localized impacts NHEP11; Short12; Beem and Short, Gloucester–Plum Island–Newburyport in smaller coves and embayments, par- 2009). The largest expanse of eelgrass section, parts of which are devoid of ticularly Maquoit Bay (Neckles et al., in New Hampshire remains in Great eelgrass.” 2005; CBEP10). Additional eelgrass Bay, despite a 49% decline in coverage The Massachusetts Department of habitat is found in the Great Bay Estu- since the 1996 peak (Short12). Smaller Environmental Protection (MassDEP) ary system, on the border of Maine and patches once scattered throughout Little began a comprehensive state-wide New Hampshire (see New Hampshire Bay and deeper portions of the Pisca- eelgrass mapping program in 1993 section below). taqua River have all but disappeared, and interactive maps are currently with a combined 99% loss reported in available from data collected in 2001 New Hampshire a one-year period (2006–2007; Short12). (MassDEP15). Prior to this effort, Eelgrass was prevalent throughout Losses include an established bed of quantitative mapping of the extent of the Great Bay Estuary system (GBE) transplanted eelgrass (0.8 hectares) eelgrass in Massachusetts is lacking, prior to a reported re-occurrence of the in the Piscataqua River from the New limiting efforts for longer trend analysis. wasting disease in the mid 1980’s which Hampshire Port Authority Mitigation However, Costa (1988) examined his- virtually eliminated the population by Project (Beem and Short, 2009). The toric trends for Buzzards Bay although 1989 (Nelson, 1981; Short et al., 1986, New Hampshire Estuaries Project current changes (after 1980’s) are not 1993). Recovery was slow, and after (NHEP), administered by the University documented. reaching peak extent in 1996, eelgrass distribution in the GBE has steadily re- 11New Hampshire Estuaries Project (NHEP). 2006. 2006 State of the Estuaries. Durham, 32 p. 13http://www.nhep.unh.edu/about/index.htm 10Casco Bay Estuary Partnership (CBEP). 12Short, F. 2008. Eelgrass distribution in the Great 14Colarusso, P. U.S. Environmental Protection 2005. 2005 State of the Bay Report. Portland, Bay Estuary 2007. Final rep. of the Univ. N. H. to Agency, Boston. Personal commun., 2009. ME, 50 p. the N. H. Estuaries Project, Durham, 7 p. 15MassDEP http://www.mass.gov/dep/

26 Marine Fisheries Review By the 1980’s it appeared as if eel- dicates that upper-Bay eelgrass popula- were used to selectively remove eelgrass grass “had saturated most available sub- tions have been entirely lost in the past in an attempt to improve water circula- strate” in Buzzards Bay (Costa, 1988). 50–100 years due to nutrient enrichment tion (Ludwig, 1977). However, despite a However, mapping efforts in the early (Bradley et al.18). Present-day distribu- number of restoration attempts, eelgrass 1990’s and in 2001 indicated a renewed tions are limited to coastal ponds and populations in western LIS never recov- steady decline; over 60% of eelgrass in isolated pockets in the lower-Bay from ered following the wasting disease. Buzzards Bay had been lost primarily Prudence Island south and along the Throughout the 1980’s and 1990’s, from nutrient enrichment (Haupert and rocky eastern coast at Sakonnet Point eelgrass populations experienced a Rasmussen16). Similarly, nitrogen load- (Bradley et al.18). The Rhode Island number of localized declines, most ing from coastal development has led to Coastal Resources Management Council notably in the Niantic River where extensive eelgrass loss in Waquoit Bay, (CRMC) and the University of Rhode eelgrass became virtually non-existent with 60% loss reported in a 5-year period Island’s Environmental Data Center (Short et al., 1988). More recently, (Short and Burdick, 1996; Hauxwell et (EDC) have created a comprehensive 2006 aerial surveys conducted by the al., 2003). Moreover, the once abundant repository for eelgrass distribution data. Connecticut Department of Environ- eelgrass beds in Boston Harbor are now Interactive maps of eelgrass distribu- mental Protection and U.S. Fish and limited to a few locations, a result of tion are available through the CRMC Wildlife Service inventoried 6.75 km2 urbanization. Despite localized losses, website.19 of eelgrass throughout eastern Long the coastal waters of Massachusetts Island Sound (Connecticut waters), an support the largest quantity of eelgrass Connecticut increase of 1.13 km2 from 2002 mapping in New England. Historically, the distribution and efforts (Tiner et al., 2007). However, abundance of eelgrass in Long Island coverage continues to vary spatially and Rhode Island Sound (LIS) has experienced dramatic temporally within and among coves and For a detailed reconstruction of his- fluctuations. A detailed description of small embayments. Declines are typi- torical eelgrass locations in Narragansett historical distributions of eelgrass in cally attributed to nutrient enrichment Bay, consult Doherty17 and references LIS can be found in a report by the Con- (Keser et al., 2003) with recovery often therein. Eelgrass is reported from 1848 necticut Department of Environmental a result of removal of nutrient inputs herbarium records and from U.S. Coast Protection and Department of Agricul- (Vaudrey21). Following the diversion of and Geodetic Survey 1865 survey sheets ture and references therein (CTDEP and a sewage-treatment facility wastewater (Doherty17). In the early 1900’s, eelgrass CTDA20). In Connecticut, at the begin- outflow in 1987, portions of Mumford was “harvested for fertilizer and insula- ning of the 20th century, eelgrass was Cove were transformed from algal domi- tion,” perhaps an indication of its wide- “common along the coast in bays, salt nated communities to Zostera marina spread prevalence in Narragansett Bay rivers, and creeks . . . extensively used dominated communities within 10 years (Doherty17). Setchell (1929) observed by farmers as a fertilizer” (Graves et al., (Vaudrey21). that “Zostera marina occurs abundantly 1910). The wasting disease event virtu- in the inner waters of Narragansett Bay ally eliminated eelgrass from the region New York as well as in the large protected salt (Marshall, 1947) but eelgrass had shown By the 1950’s, although a number of ponds of southern Rhode Island.” Al- “encouraging improvement” following Long Island locales showed “noticeable though the wasting disease did impact the event (Cottam and Munro, 1954). improvement” following the wasting a number of eelgrass populations in By the 1970’s, populations in eastern disease, eelgrass had attained less than Narragansett Bay, significant declines LIS had rebounded so remarkably that a quarter of its 1931 status (Cottam and are often attributed to a 1938 hurricane eelgrass was considered a nuisance. In Munro, 1954). In the 1960’s, a number (Doherty17). In the 1950’s, Rhode Island the Niantic River Estuary, explosives of small embayments along the southern eelgrass exhibited substantial recovery shore of Long Island reportedly harbored following the natural disturbances of the extensive eelgrass beds to the point of 1930’s, “In some places it is regarded as 18Bradley, M., K. Raposa, and S. Tuxbury. impeding small boat traffic (Dennison et 2007. Report on the analysis of true color plentiful as before 1931” (Cottam and aerial photography to map and inventory Zos- al., 1989). Brown tide events in the mid Munro, 1954). tera marina L. in Narragansett Bay and Block 1980’s caused additional large-scale die Island, Rhode Island. Environ. Data Ctr., Univ. Trend analysis conducted by the Rhode Island, Unpubl. rep., 17 p. + Eelgrass offs of eelgrass in Long Island coastal Narragansett Bay Estuary Program in- Atlas. waters (Cosper et al., 1987; Dennison 19http://www.edc.uri.edu/Eelgrass/default. et al., 1989). Only about 12% of the html 16Haupert, C., and M. Rasmussen. 2003. 2003 20CTDEP, and CTDA. 2007. An assessment State of the Bay. Coalition for Buzzards Bay, of the impacts of commercial and recreational 21Vaudrey, J. 2008. Establishing restoration New Bedford, MA, 11 p. fishing and other activities to eelgrass in Con- objectives for eelgrass in Long Island Sound Part 17Doherty, A. 1995. Historical distributions of necticut’s waters and recommendations for I: Review of the seagrass literature relevant to eelgrass (Zostera marina) in Narragansett Bay, management. A report to the Environmental Long Island Sound. Univ. Conn. final rep. pursu- Rhode Island. Narragansett Bay Estuary Prog. Committee of the Connecticut General Assem- ant to Conn. Dep. Environ. Protect. cooperative Rep. NBEP-95-121, 25 p. + app. bly pursuant to Public Act 01-115. agreement LI-97107201/CDFA#66-437. 58 p.

71(3) 27 7.69 km2 of eelgrass mapped in LIS in the 1970’s and 1980’s, followed by small region of Indian River Bay (An- in 2006 are in New York waters (Tiner significant declines in the 1990’s and derson30), excessive nutrient loading et al., 2007). Cornell University’s Co- present day (Lathrop et al., 2001; Bo- elsewhere prevents successful re-intro- operative Extension Eelgrass Program logna et al.26). Recurring brown tide, duction of eelgrass (Price, 1998). (CCE) monitors a number of existing phytoplankton, and macroalgae blooms eelgrass beds around Long Island and have plagued the region since the mid Maryland has established a number of restoration 1990’s, worsening the situation (Bolo- Eelgrass can be found from the sites in Long Island Sound, Peconic gna et al., 2001; Olsen and Mahoney, Choptank River south to the mouth of Estuary, South Shore Estuary, and the 2001; Gastrich et al., 2004). In 2006, a the Chesapeake Bay and throughout Hudson–Raritan Estuary. reported 50–88% of seagrass biomass the coastal bays. The extent of eelgrass Prior to the wasting disease, eelgrass in the Barnegat Bay–Little Egg Harbor habitat in Maryland’s coastal bays is was prevalent in the Peconic Estuary, Estuary was lost, a result of accelerated nowhere near its reported coverage of with an estimated coverage of 35.29 km2 macroalgal growth (Kennish et al.25). the 1900’s. However, eelgrass cover- (CCE22). Eelgrass acreage from 2000 The Center for Remote Sensing and age in the bays has increased steadily aerial surveys reported by Tiner et al. Spatial Analysis (CRSSA) at Rutgers since annual monitoring began in 1986 (2003) indicate an approximate 85% University has digitized existing SAV (Wazniak et al., 2004). In contrast, many loss in a 70 year period. Data from the maps dating from 1968 through 2003 of Maryland’s river estuaries, which are Peconic Estuary Program’s Long-Term to create a regional SAV time series. tributaries of Chesapeake Bay, have ex- Eelgrass Monitoring Program, initiated The interactive maps may be viewed at perienced significant declines in eelgrass in 1997, indicates a continual steady CRSSA’s website.27 primarily due to water quality issues decline in eelgrass since the late 1990’s (Stankelis et al., 2003). Large-scale (Pickerell and Schott23,24). Delaware restoration efforts (via seed broadcast- The Inland Bays of Delaware never ing) initiated by the Maryland Depart- New Jersey recovered from the wasting disease of ment of Natural Resources in 2003 for Roughly 75% of New Jersey’s SAV is the 1930’s. Cottam and Munro (1954) the Potomac and Patuxent Rivers have found in Barnegat Bay (Lathrop et al., reported “no known stands” although met with mixed success (Busch and 2001). Following the wasting disease restoration attempts were being made. Golden31). event, Cottam and Munro (1954) re- By the late 1960’s, declining water qual- ported “excellent recovery” of eelgrass ity led to the local extinction of eelgrass Chesapeake Bay and Tributaries in northern Barnegat Bay but less so in the region (Orth and Moore28; Sell- Information regarding the abundance in the southern part of the bay. Further ner29). New environmental regulations and distribution of eelgrass prior to south, beyond the bay, “the plant is in the 1980’s, in addition to natural ero- the 1950’s is lacking (Stevenson and absent, or nearly so, in areas where sion events that led to increased flushing Confer, 1978) although it appears as if it was once abundant” (Cottam and of the bays, greatly improved water eelgrass populations in the Chesapeake Munro, 1954). Continued escalation quality in the region. Although a restora- Bay succumbed to the cold snap expe- in coastal development since the mid tion program initiated by the Delaware rienced by New England in 1893–94 1970’s has led to the progressive eutro- Department of Natural Resources and (Cottam, 1934). In 1889, eelgrass was phication of the Barnegat Bay–Little Environmental Control (DNREC) in also reported to have “almost died out Egg Harbor Estuary (Kennish et al.25). 1997 has resulted in approximately in the Chesapeake area and that it were Eelgrass acreage in the estuary peaked 0.02 km2 of viable eelgrass habitat in a upwards of 25 years before the maxi- mum growth had returned” (Cottam, 22CCE http://counties.cce.cornell.edu/suffolk/ 1934). habitat_restoration/seagrassli/index.html 26Bologna, P. A. X., R. Lathrop, P. D. Bowers, In the early 1900’s, evidence suggests 23Pickerell, C., and S. Schott. 2004. Eelgrass and K. W. Able. 2000. Assessment of the health that eelgrass and other species of SAV trend analysis report: 1997–2002. Rep. to and distribution of submerged aquatic vegetation were prevalent throughout the bay and the Peconic Estuary Program, Yaphank, NY, from Little Egg Harbor, New Jersey. Inst. Mar. 100 p. Coast. Sci., Rutgers Univ., Tech. Rep. #2000-11, its tributaries (Orth and Moore, 1984). 24Pickerell, C., and S. Schott. 2008. Peconic 30 p. Following the wasting disease event, Estuary Program 2006 eelgrass (Zostera 27http://www.crssa.rutgers.edu/ SAV beds experienced increasing re- marina) long-term monitoring program. Prog- 28Orth, R, and K. Moore. 1988. Submerged ress rep. to the Peconic Estuary Program, aquatic vegetation in Delaware’s inland bays. Yaphank, NY, 27 p. In K. Sellner (Editor), Phytoplankton, nutrients, 25Kennish, M. J., S. M. Haag, and G. P. Sako- macroalgae, and submerged aquatic vegeta- 30Anderson, B. State of Delaware, Dep. Nat. wicz. 2007. Demographic investigation of tion in Delaware inland bays, 1985–1986, p. Resour. Environ. Control, Dover. Personal com- submerged aquatic vegetation (SAV) in the 86–109.Acad. Nat. Sci. final rep. to D. E. Dep. mun., 2009. Barnegat Bay-Little Egg Harbor Estuary with Nat. Res. 31Busch, K., and R. Golden. 2009. Large-scale assessment of potential impacts of benthic 29Sellner, K. 1988. Phytoplankton, nutrients, restoration of eelgrass (Zostera marina) in the macroalgae and brown tides. Inst. Mar. Coast. macroalgae, and submerged aquatic vegetation Patuxent and Potomac Rivers, Maryland. Final Sci., Rutgers Univ. New Brunswick, Tech. Rep. in Delaware inland bays, 1985–1986. Acad. Nat. rep. of the Maryland Dep. Nat. Resour. pursuant 107-15, 366 p. Sci. final rep. to D. E. Dep. Nat. Res., 140 p. to NOAA Award #NA03NMF4570470.

28 Marine Fisheries Review covery through the 1960’s (Cottam and eelgrass (i.e. Albemarle Sound, west- eelgrass plants, primarily due to the Munro, 1954; Orth and Moore, 1984) ern Pamlico Sound). There has been high cellulose content of the leaves, but experienced a major setback from no sustained effort to monitor or map which is difficult to digest. The domi- the effects of runoff following Tropical seagrass state-wide until very recently, nant food pathway for eelgrass itself Storm Agnes in 1972. Again, increas- although portions of the coast were is through the detrital food chain; its ing nutrient and sediment loads from mapped in the mid 1980’s and early contribution to estuarine productivity development led to a precipitous bay- 1990’s (Ferguson et al., 1991, 1993; is more complex and is intertwined wide decline of all submerged aquatic Ferguson and Wood34; NOAA35,36,37). with habitat-associated microalgae. The vegetation in the 1970’s (Kemp et al., The Submerged Aquatic Vegetation detritivores (crabs, shrimps, mollusks) 1983; Orth and Moore, 1983). Annual Mapping Partnership, facilitated by the in turn, are prey items for larger species surveys initiated in 1984 and conducted Albemarle–Pamlico National Estuary (fish, birds). by the Virginia Institute of Marine Program (APNEP), acquired digital Eelgrass meadows provide habitat, Science (VIMS) indicate that there aerial photography from along the entire nurseries, and feeding grounds for a continues to be considerable annual coast of North Carolina in 2007–2008. number of commercially, recreation- variation in all SAV coverage across A state-wide GIS eelgrass database ally, and ecologically important species the bay, with declines in some areas resulting from this imagery is in prog- (Table 2), including the bay scallop, and recovery in others. Interactive maps ress. For more information, consult the Argopecten irradians. As juveniles, bay can be viewed at the VIMS website.32 APNEP website.38 scallops attach directly to the blades Water quality issues continue to be the of eelgrass plants, but later drop to the primary factors affecting SAV growth Faunal Communities sediment surface (Thayer and Stuart, in Chesapeake Bay. Faunal use of eelgrass habitat is 1974; Eckman, 1987; Garcia-Esquivel widely divergent; eelgrass fauna may and Bricelj, 1993). In North Carolina, Virginia Southern Coastal Bays include seasonal or year-round resi- eelgrass is often the only available Following the wasting disease event dents, may use eelgrass meadows for “hard” substrate for scallops to settle on, and a catastrophic hurricane in 1933, all or a portion of their life cycle, or keeping the scallops away from preda- eelgrass beds in this region were deci- may only visit the meadow for grazing tors, indicating its local importance as mated. In the mid 1990’s, the discovery purposes. The structural organization of essential fish habitat for this species of small, natural patches of eelgrass individual eelgrass plants and eelgrass (Kirby-Smith, 1970). In addition to prompted an eelgrass restoration effort meadows as a whole allows for exploi- individual plants serving as habitat, in the Delmarva Southern Coastal tation of a number of habitat types. the structure of the eelgrass meadow Bays of Virginia. Between 2001 and Eelgrass fauna may attach directly to influences the population dynamics of 2004, 24.2 million eelgrass seeds were the leaves of the plant, bury into the the bay scallop. It has been shown that broadcast by hand, resulting in the re- sediments within a meadow, live on top the spatial patterning of eelgrass beds introduction of eelgrass to areas devoid of the sediment, associate with blades can alter rates of predation on bay scal- since 1933 (Orth et al., 2006).The final, but remain unattached, or actively swim lops (Irlandi et al., 1995); higher rates sustained acreage arising from this work amongst the canopy. With the exception of predation were observed as the level remains undetermined. of some fishes, sea turtles, Brant and of fragmentation of the bed increased Canada geese, and some mollusks, few (Irlandi et al., 1995). Due to the tight North Carolina actually feed directly on live linkages between eelgrass and bay North Carolina represents the south- scallops, any change in eelgrass popula- ern geographic boundary for eelgrass tions should directly affect that of the 34Ferguson, R., and L. Wood. 1994. Rooted vas- along the U.S. eastern seaboard. Al- cular beds in the Albemarle-Pamlico estuarine bay scallop. though affected by the wasting disease, system. Albemarle-Pamlico Estuarine Study eelgrass populations in North Carolina Rep. No. 94-02, 108 p. Human Threats to Eelgrass 35National Oceanic and Atmospheric Adminis- were able to substantially recover and tration. 1994. SAV habitat from Ocracoke Inlet Point and non-point source nutrient have remained relatively stable since to Pea Island, North Carolina. NOAA, Center for loading and sediment runoff are the the 1970’s (Fonseca33). Eelgrass is Coastal Fisheries and Habitat Research, Beau- primary threats to eelgrass along the fort, N.C. Unpubl. GIS data. found south of Oregon Inlet down 36National Oceanic and Atmospheric Admin- Atlantic coast and are believed to be the through Bogue Sound. As is typical istration. 1992. Submerged aquatic vegetation number one cause of eelgrass decline in most regions, estuaries and sounds of Bogue Sound, North Carolina 1992. NOAA, locally. Orth and Moore (1983) reported Coastal Services Center, Charleston, N.C., with higher turbidity do not support Unpubl. GIS data significant declines of eelgrass in Ches- 37National Oceanic and Atmospheric Adminis- apeake Bay in the late 1970’s and early tration. 1990. Core Sound, North Carolina Com- 1980’s apparently the result of increased 32http://www.vims.edu/bio/sav/ posite SAV Data Set 1985-1990. NOAA, Coastal runoff and watershed development. 33Fonseca, M. NOAA, Center for Coastal Fish- Services Center, Charleston, N.C., Unpubl. GIS eries and Habitat Research, Beaufort, N.C. Per- data Similar trends were documented by sonal observ. 38http://www.apnep.org/ Costa (1988) for Buzzards Bay, Mass..

71(3) 29 Table 2.—Non-inclusive list of representative commercially, recreationally, and ecologically important species Biological Disturbance using eelgrass beds along the Atlantic coast of the United States. Life history stages are represented as A = adult, J = juvenile, L = larvae, E = eggs, M = migratory. Modified from Thayer et al., 1979, 1984. Distribution of eelgrass is also medi- Common Name Scientific Name Life Stage ated by biological disturbance (animals). Fish Orth (1975) described substantial Spotted seatrout Cynoscion nebulosus J Mullet Mugil cephalus J removal of healthy eelgrass by large Spot Leiostomus xanthurus A, J numbers of cownose rays. Townsend Pinfish Lagodon rhomboides A, J Pigfish Orthopristis chrysoptera J and Fonseca (1998) showed the role of Gag grouper Mycteroperca microlepis J disturbance in the maintenance Sheepshead Archosargus probatocephalus A, J of eelgrass bed margins. Biological Thread herring Opisthonema oglinum J Permit Trachinotus falcatus J disturbance is also one of the primary White grunt Haemulon plumieri J problems facing restoration projects Bluefish Pomatomus saltatrix A, J (Fonseca et al., 1998; see Restoring Tautog Tautoga onitis J, E Summer flounder Paralichthys dentatus A, J Eelgrass below). Southern flounder Paralichthys lethostigma A, J Winter flounder Pseudopleuronectes americanus J Restoring Eelgrass Menhaden Brevoortia tyrannus A, J, L Smelt Osmerus mordax M Addy’s (1947) basic logic was to Striped bass Morone saxatilis A match eelgrass planting and harvest Elasmobranchs Cownose ray Rhinoptera bonasus A, J site environments, and this remains a Southern stingray Dasyatis sabina A, J fundamental tenet in almost all sea- Decapods grass planting today. Aside from early Brown shrimp Penaeus aztecus A, J Pink shrimp Penaeus duorarum A, J interest by Phillips (1960), almost 30 Blue crab Callinectes sapidus A years elapsed before serious attention American lobster Homarus americanus J Limulus polyphemus A, J to planting seagrass developed. It was Mollusks not until the 1970’s that documents Bay scallop Argopecten irradians A, J again began to emerge presenting sea- Hard clam Mercenaria mercenaria A. J Soft-shell clam Mya arenaria A, J grass planting in a guideline format, Whelks Busycon spp. A, J culminating in a national guidelines Blue mussels Mytilus edulis A, J document (Fonseca et al., 1998). But Variable Bittium Bittium varium A, J, E Slipper limpet convexa A, J, E even though suitable planting methods Birds have long existed, the track record for Brant goose Branta bernicla M Canada goose Branta canadensis M successful mitigation of impacts to eel- Greater scaup Aythya marila M grass beds remains variable (see review duck Aythya americana M by Phillips, 1982). Great blue heron Ardea herodias A Great egret Casmerodius albus A Much emphasis was placed on tech- Reptiles nique development in the late 1970’s Kemp’s ridley sea turtle Lepidochelys kempii A, J and early 1980’s, but relatively little Loggerhead sea turtle Caretta caretta A, J Green sea turtle Chelonia mydas A, J attention was given to developing a management framework within which these techniques could be effectively Nutrient inputs from land development, Eelgrass meadows are also vulner- implemented. As a result, most seagrass sewage treatment plants, agricultural able to disturbance from commercial mitigation projects have failed to achieve activities, and impervious surfaces can fishing activities, especially those as- even the goal of 1:1 habitat replacement lead to eutrophication (i.e. algal and sociated with scallop harvesting. The (i.e. offset a net loss of seagrass habitat). phytoplankton blooms which reduce the epibenthic dredges used to harvest bay Nonetheless, eelgrass beds have often amount of light penetrating to the grass scallops lead to dramatically decreased been successfully planted and have bed leading to large-scale declines and/ shoot densities and biomass of eelgrass come to perform much as naturally- or dieoffs; Short et al., 1995; Short and (Fonseca et al., 1984). Bishop et al. propagated beds (see review by Fonseca Burdick, 1996). Deforestation and other (2005) reported a 9% loss of meadow et al., 1998). disturbances to the coastal terrain (i.e. biomass in just 10 minutes of dredge Of all the North American seagrasses, land development) deliver high amounts activity. Orth et al. (2002) reported on eelgrass has a growth rate and strategy of sediment to inshore waters leading significant eelgrass impacts resulting that makes it especially conducive to to increased turbidity and reduced light from hard clam harvest and how careful restoration. As mentioned earlier, eel- penetration at depth. As the coastal zone monitoring was used to quickly modify grass plants migrate across the seafloor continues to be developed, these threats fishing regulations to prevent further and are morphologically plastic which will not go away. habitat loss. provides an adaptive advantage in that

30 Marine Fisheries Review they have some capacity to locate more Conclusions Bintz, J. C., S. W. Nixon, B. A. Buckely, and S. L. Granger. 2003. Impacts of temperature and favorable conditions. They are also nutrients on coastal lagoon plant communi- prolific in their seed production, giving Eelgrass has been shown to be a ties. Estuaries 26(3):765–776. them another advantage in that they can critical part of the bay scallop life cycle, Bishop, M. J., C. H. Peterson, H. C. Summer- son, and D. Gaskill. 2005. Effects of harvest- disperse broadly. Finally, as each shoot providing substrate for settlement and ing methods on sustainability of a bay scallop is terminal on a rhizome, each shoot is subsequent shelter and feeding (Thayer fishery: dredging uproots seagrass and dis- places recruits. Fish. Bull. 103:712−719. a viable contributor to both daughter and Stuart, 1974; Eckman, 1987; Bologna, P., A. Wilbur, and K. Able. 2001. Repro- ramets (new members of the population) Garcia-Esquivel and Bricelj, 1993; duction, population structure, and recruitment and seeds (in their second year when Irlandi et al., 1995). Thus, bay scallop limitation in a bay scallop (Argopecten irra- dians Lamarck) population from New Jersey, in their perennial form). Unlike many abundance and the success of the fishery USA. J. Shellfish Res. 20(1):89–96. other seagrasses that put down stationary appear to be inextricably linked to the Burdick, D. M., F. T. Short, and J. Wolf. 1993. An shoots that do not subsequently add to health of eelgrass habitat. However, eel- index to assess and monitor the progression of wasting disease in eelgrass Zostera marina. population growth (with the exception of grass in the western Atlantic is almost Mar. Ecol. Prog. Ser. 94:83–90. infrequent branching for some species) certainly at an historic low since the Cosper, E. M., W. C. Dennison, E. J. Carpenter, V. M. Bricelj, J. G. Mitchell, S. H. Kuenster, and are thus not useful in vegetative wasting disease event of the 1930’s, D. Colflesh, and M. Dewey. 1987. Recurrent transplants, eelgrass shoots are all viable a result of human development of the and persistent brown tide blooms perturb transplanting units and thus fewer shoots coastal zone. We conclude that the re- coastal marine ecosystem. Estuaries 10(4): 284–290. are needed for harvest and installation. duced distribution of eelgrass, together Costa, J. 1988. Eelgrass in Buzzards Bay: dis- For a full review of eelgrass and other with periodic heavy fishing pressure on tribution, production, and historical changes seagrass restoration, see Fonseca et al. scallops (MacKenzie, 2008) combine to in abundance. U.S. Environ. Protect. Agency Rep. EPA 503/4-88-002, Wash. D.C., 204 p. (1998). produce the current marginal health of Cottam, C. 1934. Past periods of eelgrass scar- While methodological innovations that fishery. Moreover, natural fluctua- city. Rhodora 36(427):261–264. ______. 1935. Further notes on past periods of continue, the limitations to restoring tions in both eelgrass distribution and eelgrass scarcity. Rhodora 37(440):269–271. this crucial national resource are rarely the erratic nature of the bay scallop ______and D. A. Munro. 1954. Eelgrass technical (there are many viable tech- population cycle (MacKenzie, 2008) status and environmental relations. J. Wildl. Manage. 18(4):449–460. niques), but instead lay in the utilization may further limit scallop population den Hartog, C. 1971. The dynamic aspect in the of extant knowledge. Recent advances persistence through habitat fragmenta- ecology of seagrass communities. Thalassia in eelgrass seeding and whole plant tion and scallop recruitment limitation Jugosl. 7:101–112. Dennison, W. C. 1987. Effects of light on sea- restoration technologies (see review which all point to a fishery with pro- grass photosynthesis, growth and depth distri- in Fonseca et al., 1998) demonstrate found challenges for survival. bution. Aquat. Bot. 27(1):15–26. the ongoing decline of methodological ______, R. J. Orth, K. A. Moore, J. C. Ste- Acknowledgments venson, V. Carter, S. Kollar, P. Bergstrom, and limitations. Problems tend to emerge in R. A. Batiuk. 1993. Assessing water quality the application of this knowledge; for We would like to thank D. Field, with submersed aquatic vegetation. Biosci- ence 43(2):86–94. example, the expectations of eelgrass W. Hobart, D. Johnson, P. Marraro, G. ______, G. J. Marshall, and C. Wigand. restoration are grossly unrealistic being Matlock, J. Strader, J. VanderPluym, 1989. Effect of “brown tide” shading on eel- held as they are to standards often and two anonymous reviewers for con- grass (Zostera marina L.) distributions. In E. M. Cosper, V. M. Bricelj, and E. J. Carpen- higher than agricultural crops despite structive comments. Special thanks to ter (Editors), Novel phytoplankton blooms: the huge disparity in our knowledge B. Anderson, S. Barker, D. Cavanaugh, Causes and impacts of recurrent brown tides and other unusual blooms, p. 675–692. base and economic subsidy among P. Colarusso, J. Costa, C. Costello, K. Springer-Verlag, Berlin. these practices. Aside from unrealistic Hogeland, J. Kenworthy, C. MacKenzie, Eckman, J. E. 1987. The roll of hydrodynamics expectations of success, chief among R. Orth, C. Pickerell, K. Raposa, and F. in recruitment, growth, and survival of Argo- pecten irradians (L.) and Anomie simplex the problems facing resource manag- Short for providing unpublished data (D’Orbigny) within eelgrass meadows. J. ers today is the tendency for project and copies of grey literature, and for Exp. Mar. Biol. Ecol. 106(2):165–191. Evans, A. S., K. L. Webb, and P. A. Penhale. applicants to select planting areas permitting the use of photographs and 1986. Photosynthetic temperature acclima- where there is no prior history of their previously published graphics. tion in two coexisting seagrasses, Zostera existence (unless of course the site was marina L.and Ruppia maritima L. Aquat. Bot. Literature Cited 24(2):185–197. created for the purposes of planting sea- Ferguson, R. L., and K. Korfmacher. 1997. grass). The chronic absence of seagrass Addy, C. E. 1947. Eel grass planting guide. Remote sensing and GIS analysis of seagrass from a site, especially when there are Maryland Conserv. 24:16–17. meadows in North Carolina, USA. Aquat. ______and D. A. Aylward. 1944. Status of Bot. 58(3–4):241–258. propagule sources nearby, usually in- eelgrass in Massachusetts during 1943. J. ______, L. L. Wood, and D. B. Graham. 1993. dicates that the site cannot consistently Wildl. Manage. 8(4):269–275. Monitoring spatial change in seagrass habitat Andrews, J. C. 1990. Fishing around Nantucket. with aerial photography. Photogram. Eng. support seagrasses. Ensuring sufficient The Maria Mitchell Assoc. Nantucket, Mass., Rem. Sens. 59(6):1033–1038. light, moderate nutrient loads, and 76 p. ______, ______, and B. T. Pawlak. 1991. protecting plantings from disturbance Beem, N. T., and F. T. Short. 2009. Subtidal eel- SAV habitat from Drum Inlet to Ocracoke grass declines in the Great Bay estuary, New Inlet, North Carolina. NOAA Coastal Ocean constitute the other major caveats for Hampshire and Maine, USA. Estuaries Coasts Program Submerged Aquatic Vegetation developing a persistent eelgrass bed. 32:202–205. Study. U.S. Dep. Commer., NOAA, NMFS

71(3) 31 Beaufort Lab., Beaufort, N.C. (3- × 4-foot tion of seagrass habitat influences growth and yrinthula sp., a marine slime mold producing chart with text and illust.) survival of the bay scallop. Oikos 72(3):307– the symptoms of wasting disease in eelgrass, Fonseca, M. S., and S. S. Bell. 1998. Influence of 313. Zostera marina. Mar. Biol. 99:465–472. physical setting on seagrass landscapes near Kemp, M., R. Batiuk, R. Bartleson, P. Berg- ______, ______, and ______. 1991. Beaufort, North Carolina, USA. Mar. Ecol. strom, V. Carter, C. L. Gallegos, W. Hunley, Labyrinthula zosterae sp. vNo., the causative Prog. Ser. 171:109–121. L. Karrh, E. W. Koch, J. M. Landwehr, K. A. agent of wasting disease of eelgrass, Zostera ______and J. A. Cahalan. 1992. A prelimi- Moore, L. Murray. M. Naylor, N. B. Rybicki, marina. Mycologia 83(2):180–191. nary evaluation of wave attenuation by four J. C. Stevenson, and D. J. Wilcox. 2004. Neckles, H. A., F. T. Short, S. 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