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State of Sanctuary Resources
This section provides summaries of the condition and trends within four resource areas: water, habitat, living resources, and archaeological resources. For each, sanctuary staff and selected outside experts considered a series of questions about each resource area. Answers are supported by specific examples of data, investigations, monitoring, and observations, and the basis for judgment is provided in the text and summarized in the table for each resource area. Where published or additional information exists, the reader is provided with appropriate references and web links.
Much of the pollution reaching the sanctuary comes from non-point sources or from distant point sources. Several waste water treatment facilities discharge into Massachusetts Bay to the north and south of the sanctuary, the largest being the Massachusetts Water Resources Authority (MWRA) Boston Harbor outfall located 9.5 miles from Boston and 12 miles west of the Stellwagen Bank sanctuary border. Air pollution from power plants comes from as far away as the Midwest. A variety of chemicals move from the air to the water where they can be accumulated by organisms. In addition, the region is heavily traveled by commercial and recreational vessels and cruise ships that discharge wastes during their voyages. Other sources of contamination include clean material disposal at the Massachusetts Bay Disposal Site, and disturbances during the laying of underwater pipes and cables (only one of which crosses the sanctuary). Of concern are the cumulative impacts of multiple activities that may affect the resources of the sanctuary.
In 2001, sanctuary staff developed a monitoring plan to examine whether the MWRA outfall (which began operating in September 2000) was causing increased eutrophication and contaminant loading in the sanctuary. To maximize the use of resources and obtain compatible information with ongoing monitoring efforts, the sanctuary added four stations to MWRA's existing five stations within the sanctuary. Since 2001, independent contractors have sampled those four additional stations in August and October (this sample collection coincides with two of the six MWRA surveys each year). Sampling includes measurements of water column physical variables (salinity, temperature, density structure), nutrients, chlorophyll and dissolved oxygen, as well as phytoplankton and zooplankton. The four sanctuary stations are strategically placed to detect nutrient inputs to the sanctuary from the Gulf of Maine to the north, and from the MWRA outfall to the west. The data allow inferences about fine scale circulation patterns and water column productivity in the sanctuary, and are used for a three-dimensional model that has been developed to assist managers with understanding how the system might respond to increased and decreased levels of nutrients, dilution of outfall, and dispersion. Results to date show no evidence of increased eutrophication or contaminant loading in the sanctuary (MWRA 2004).
|Nutrient and chlorophyll levels appear to decline or remain stable in the first two years after the MWRA Boston Harbor outfall was activated in September 2000. (Source: C.Hunt, Battelle Ocean Sciences)
Nutrient enrichment is one factor in the development of harmful algal blooms (HAB). HABs are high densities of toxic phytoplankton (Alexandrium sp.), that can kill marine life and impair human health. The most recent HAB event occurred in 2005 and covered a broad area encompassing all of Massachusetts Bay (including Stellwagen Bank) and Cape Cod Bay. The highest concentration of Alexandrium cysts were recorded in the sediment of the sanctuary. The presence of these cysts may cause another bloom in the future although none occurred in 2006.
Since the 1970s there have only been a few adequate water quality studies that have provided contaminant concentrations in the water column within or adjacent to Stellwagen Bank sanctuary. Results from the most recent study in 2004 are discussed below in the section on habitat status.
Although studies show that water quality in and around the sanctuary is currently at acceptable levels of most contaminants, the continuing pressures of point- and non-point sources of pollution are cause for concern. Therefore, it will be critical to continue water quality monitoring and improve methods of conducting these activities.
The following information provides an assessment by sanctuary staff of the status and trends pertaining to water quality and its effects on the environment:
- Numerous contaminants have been identified, but they are at low levels, suggesting fair to good conditions; at present, conditions appear to be stable.
- Eutrophication does not appear to be a problem, and conditions appear favorable for both habitat and living resource quality.
- Water quality does not pose a risk to human health at this time, and conditions appear to be relatively stable.
- The high levels of human activities that may influence water quality (particularly discharges from vessel traffic) are not currently having an adverse effect on water quality conditions, and appear to be stable.
Activities that currently have the greatest potential impact on the habitats of Stellwagen Bank are the laying of cables and pipelines, the use of mobile fishing gear, removal of key forage species and bycatch due to fishing activities, ocean dumping, and the disposal of dredged materials. Currently, regulations are in place that protect the sanctuary, to some extent, from the effects of fishing, laying cables and pipelines, ocean dumping, and disposal of dredged material. However, fishing activity continues to threaten the integrity of sanctuary habitats and trophic relationships.
Studies conducted to date indicate significant impacts of bottom fishing gear on benthic habitats in New England, particularly habitats with vertical relief and complex structure (Auster and Langton 1999, Dorsey and Pederson 1998). Hard bottom habitats support complex epifaunal communities that are removed, damaged, or destroyed by bottom trawling and dredging (Watling and Norse 1998). In contrast, mobile sand habitats that cover parts of Stellwagen Bank are less vulnerable to gear impacts because the sediment is routinely perturbed by storm events.
Fishing activities alter the structure of marine habitats and influence the diversity, composition, biomass, and productivity of the associated biota (Auster et al. 1996). These effects vary according to gear used, habitats fished, and the magnitude of natural disturbance, but tend to increase with depth and the stability of the substrate.
A long-term study (Seafloor Habitat Recovery and Monitoring Project) was initiated in 1998, when the Western Gulf of Maine habitat closed area, overlapping 22% of the sanctuary, went into effect. The study took advantage of the opportunistic closure to quantify the recovery of communities and habitats previously subject to fishing activities and to understand the dynamics of communities and habitats over time. The study design initially included sites inside and outside the closure in mud, sand, gravel, and boulder habitat types. The study was designed to compare and contrast the effects on community structure from natural disturbance versus anthropogenic disturbance (e.g. a single acute impact, such as a cable installation, and chronic impacts from a range of fishing activities).
In 2001, the seafloor monitoring study was expanded when a telecommunications company installed a fiber-optic cable across the sanctuary after receiving a NOAA permit. Monitoring is now conducted at sampling sites to distinguish differences between recovery rates from fishing and cable impacts. Separate projects are focusing on dynamics and effects on infaunal communities, epifaunal communities, fish microhabitat structure, and landscape dynamics.
To date samples have been collected from 1998-2006. Analysis and preliminary results of the various approaches are at different stages. However, preliminary analyses demonstrate some interesting patterns and trends:
- There are significant differences in epifaunal community structure between boulder and gravel habitats despite the fact that both are composed of hard substrate (Tamsett in prep).
- Within boulder and gravel habitat types there are differences in community structure between sites inside and outside the habitat closed area indicative of impacts from fishing activities (Tamsett in prep).
- Within mud habitat types there are differences in community structure between sites inside and outside the habitat closed area indicative of impacts from fishing activities (Grannis 2001).
- Contrasts in the composition of sand habitat communities inside and outside of the habitat closed area are not clearly different, suggesting that fishing effects superimposed on background patterns of natural disturbance have similar effects on sand communities (Grannis 2001).
- Community structure is changing across time both inside and outside the habitat closed area in all habitats, suggesting a dynamic environment where both natural and human caused disturbances (from fishing) mediate the composition and trajectory of seafloor communities (Grannis 2001, Tamsett in prep).
- Samples from inside and outside the habitat closed area along the route of the fiber-optic cable do not demonstrate an effect of the acute impact of the cable but do suggest an effect from fishing (Grannis 2001).
- The trench that was produced during the cable burial operation in 2001 was still visible along significant parts of the path through the sanctuary in 2006. The side scan sonar records demonstrate that 5 years of time have been insufficient for sediment transport processes to fill in the feature (Auster and Lindholm, unpublished).
There are also some trends in the composition of particular species and groups (Tamsett in prep). The abundance of ascidians (primarily Mogula sp.) has increased significantly inside the closed area over time while the brachiopod Terebratulina septentrionalis has increased outside. The exact mechanism is not clear from these observations but we can hypothesize various types of direct and indirect interactions where either differential rates of survivorship or competitive interactions mediated by fishing disturbance result in such patterns. Across the entire area there has been a decline in brittle stars, obviously resulting from some type of area-wide effect, such as increased predation by increasing demersal fish populations. Finally, there is a general pattern in species groups that provide shelter resources for fishes, such as sponges and erect bryozoans, to be more abundant inside the closed area than outside (McNaught, unpublished ms). This pattern is supported by multiple reviews of fishing effects studies.
Contaminant levels are a concern due to the opening of the Boston Harbor outfall pipe in 2001, the historic and current discharge of municipal sewage from the Boston metropolitan area and other cities and towns along Massachusetts Bay, and the historic dumping of toxic material at the Massachusetts Bay Disposal Site. In 2004, field samples were taken to assess the status and trends of chemical contamination in sediments and resident biota, and to assess the biological condition of the various habitat types found in the region. Sampling efforts employed a combination of protocols from the NOAA National Status and Trends Bioeffects Program and the National Benthic Surveillance Program. The Bioeffects Program assesses sediment contamination, toxicity, and benthic community condition. The Benthic Surveillance Program also addresses sediment contamination, in addition to contaminant body burdens and histological indicators in resident fish. Sampling was coordinated between National Status and Trends in collaboration with the NOAA Northwest Fisheries Science Center. Data from 2004 were contrasted with historical data, and data from the Massachusetts Water Resources Authority (MWRA) to assess the spatial and temporal trends in chemical contamination in the region as a whole. Both the NOAA and MWRA sampling regimes included sampling sites within the following four zones: Boston Harbor, Massachusetts Bay, Area Between Bays, and Stellwagen Bank. The lowest contaminant concentrations were consistently found in the Stellwagen Bank sites (NOAA in prep, also see Bothner et al. 1993, Bothner et al. 1994, Bothner and Butman 2005).
|Concentrations of selected metals, cadmium (Cd) and lead (Pb), and organics (total PCBs and DDT) in sediments within Massachusetts Bay. Note the lowest concentration for each contaminant is at Stellwagen Bank. Click here for a larger view. (Source: National Status and Trends Bioeffects, 2004)
The following information provides an assessment by sanctuary staff of the status and trends pertaining to the current state of the marine habitat:
- Currently, the abundance and distribution of major habitat types within sanctuary boundaries are being affected by human activities, and are improving only in the habitat closed area overlapping the sanctuary.
- The condition of biologically structured habitats (i.e., those formed primarily by the presence of large benthic macrofauna or flora) is currently fair to poor, owing to ongoing disturbance, and is improving only in the habitat closed area overlapping the sanctuary.
- Contaminant concentrations in sanctuary habitats are low and currently stable.
- The levels of human activities that may influence benthic and water column habitats are considerable, primarily bottom dragging, dredging, shipping, and trap fishing.
The primary objective of sanctuary management is resource protection, including the restoration and maintenance of natural biological communities and ecological processes. Specific concerns related to this objective are the diversity, abundance, and size range of fishes (including sand lance and herring which serve as the primary prey of many fish, marine mammals, and seabirds), the health and integrity of marine mammals, the contaminant levels in marine organisms, and colonization by invasive species.
The Stellwagen Bank area has had a long history as a productive fishing ground, popular for finfish and crustaceans (including cod, haddock, yellowtail flounder (Limanda ferruginea), groundfish, crabs, lobsters, shrimp, scallops and bluefin tuna (Thunnus thynnus). This area has been fished for nearly 400 years since European colonization, and for the past half century with trawl and dredge gear. Fishing pressures have depleted populations of important local stocks, reducing the size and age structure of the populations, causing restructuring of food webs and resulting in changes to the composition of biological communities. Sanctuary-supported research is focused on determining patterns of diversity, status of communities, and effects of human-caused disturbance, as well as developing monitoring strategies for key species and habitats.
In a study using a 25-year trawl time series (1970 1994), Auster (2002) found that while the effects of exploitation of fish populations did not result in local extinctions, there were significant declines in a range of diversity metrics that take both species richness and abundance into account and that can be attributed to extensive exploitation of dominant species and bycatch mortality of species of lower abundance and of little economic value.
A more recent analysis of spatial patterns in the diversity of fishes shows trends in recovery of diversity to levels comparable to the 1970s. However, as years were teased apart (in five-year blocks of time), trends in diversity indices over the 30 year time series showed that diversity of fishes at Stellwagen Bank, measured using six different indices, varied over the time series. The fish community in fall was generally more diverse than in spring. This can be attributed to warmer surface waters in the fall, which allow warm water and cold water species to co-occur across the diversity of shallow and deep habitats that occur along a wide depth gradient within the sanctuary.
NOAA National Marine Fisheries Service research trawl data (1963-2000) from within sanctuary boundaries have been analyzed to determine the effects of fishing on fish size and structure. Data on the change in length of the largest individuals for 15 species, and the change in length of those individuals that fell within the top 10 percent for length were examined. The 15 species were: white hake (Urophycis tenuis), goosefish (Lophius americanus), pollock (Pollachius virens), winter flounder (Pseudopleuronectes americanus), silver hake, cod, windowpane flounder (Scophthalmus aquosus), yellowtail flounder, haddock, American plaice (Hippoglossoides platessoides), redfish, ocean pout (Macrozoarces americanus), witch flounder (Glyptocephalus cynoglossus), red hake (Urophycis chuss), and dogfish (Squalus acanthias).
All of the species examined showed decreasing trends in maximum length over the 37-year period. For seven of these (white hake, goosefish, winter flounder, silver hake, cod, yellowtail flounder, haddock), regressions were highly significant, and 37-year length decreases ranged from 15 to 49 percent. The average 37-year decrease was 20 percent + 14 standard deviations and the distribution of decreases was highly significant (Crawford in prep).
The selective removal of top predators in large numbers by commercial and recreational fishing has been shown to have cascading effects on trophic dynamics that reduces ecological integrity (Jackson et al. 2001, Steneck et al. 2004, Frank et al. 2005).
The sand lance is a key species within the sanctuary and serves as the primary prey of humpback whales. Sand lance availability is largely dependent on environmental conditions and predator-prey interactions, which can be highly variable and difficult to predict. According to researchers at the University of New Hampshire, the southern range of the copepod, Calanus finmarchicus, is receding northward from Cape Cod as part of a warming trend. This copepod is considered to be an important prey species for sand lance. Additionally, the availability of sand lance is associated with the species mix and abundance of its principal larval predators, herring and mackerel. A dramatic population increase in herring is being observed, and it is uncertain how the ecosystem-shift favoring small pelagic species factors into the rate of predation on sand lance. Also, there are two species of sand lance in Massachusetts waters, and it is uncertain which predominates within sanctuary waters, complicating the understanding of their respective population dynamics. Finally, there is the possibility that sand lance spawn in the sanctuary, where they deposit their eggs in sand habitats. The cyclic availability of sand lance may partly or entirely be due to variations in year class strength associated with local inter-annual spawning success.
There are few studies that have measured contaminant concentrations in Stellwagen Bank organisms. In cases where analyses have been conducted on species from the bank or adjacent areas, concentrations of contaminants appear to be the same or only slightly elevated compared to clean control sites. At present, it is not possible to determine whether these slightly elevated contaminant concentrations are adversely affecting the health of sanctuary organisms. A number of studies on species closer to shore have shown much higher levels of contaminant body burdens, such as metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides, than the species sampled from Stellwagen Bank. However, a measurable adverse impact on organism health has only been demonstrated for the most contaminated sites (e.g. Boston Harbor, Salem Harbor, New Bedford Harbor). Therefore, it is unlikely that the low levels of contaminants measured in Stellwagen Bank species are having adverse effects on organisms' health.
Vessel collisions with whales along the east coast of the United States have received a great deal of attention in recent years because of their role in inhibiting the recovery of North Atlantic right whales. Vessel strikes are the leading cause of human-induced mortality in this species, followed by entanglement in fixed fishing gear (NOAA 2001). Given the precarious position and current decline of the right whale population, and the probability that saving only two additional right whale females per year would halt the decline, the issue is serious and demands immediate attention.
Research indicates that approximately 10% of the worldwide data regarding collisions were reported from the Stellwagen Bank area (including Cape Cod Bay and Boston Harbor) and that the sanctuary area is a “hot spot” for vessel strikes along the eastern U.S. seaboard (Anon 2004). Data indicate that about 39% of reported strikes result in mortality or serious injury (Anon 2004). Species involved included four endangered species (humpback, finback, sei (Balaenoptera borealis), and right) and one protected species (minke) with most strikes involving humpback whales. Vessels involved in the strikes include commercial whale watch vessels, private recreational-type boats and large commercial ships.
Also of concern is the disturbance, or potential for disturbance, of marine mammals by human activities occurring within and around the sanctuary. Causes for behavioral disturbances include a large number of whale watching boats in the area (Stellwagen is one of the top 10 whale watching locations in the world), a high frequency of aircraft overflights in the vicinity, and noise from the high number of vessels passing through and near the bank.
|This map shows the location of entangled whales between 1985 and 2003, many of which were sighted within the sanctuary. Click here for a larger view. (Source: Provincetown Center for Coastal Studies, 2003)
Marine mammal entanglement in fishing gear is also a priority concern. Stellwagen Bank is heavily populated by marine mammals and fishing gear capable of entangling them (Wiley et al. 2003). The immediate effects of entanglement range from mortality to minor injuries. Long-term effects can include deteriorating health and decreased reproductive ability. Marine mammal species reported to be most susceptible to entanglement include baleen whales, harbor porpoises (Phocoena phocoena), white-sided dolphins (Lagenorhynchus acutus), and harbor seals.
Invasive species exist in the sanctuary and have for many decades. However, their abundance and distribution have not been documented. Most recently, the invasive tunicate Didemnum sp. was observed in the sanctuary (Auster personal comm.). Monitoring the trends in invasive species is an important consideration as they can alter ecosystem structure and function.
- The following information provides an assessment by sanctuary staff of the status and trends pertaining to the current state of the sanctuary’s living resources:
- Sanctuary biodiversity is currently in fair to poor condition, having sustained considerable impacts from high levels of prior and current human activity, but is improving.
- The condition of extracted species from the sanctuary is currently fair to poor, with considerable fishing pressure on resources throughout the sanctuary.
- The level of non-indigenous (invasive) species is not high, but new species are being identified, which could threaten other sanctuary resources.
- The populations of key species, such as sand lance, are unstable, and fluctuate widely from year to year, with concomitant effects on consumers, such as whales. Cod, a keystone species, is significantly depleted, affecting populations of numerous other species.
- Key resources, especially marine mammals, are vulnerable to vessel strikes, entanglement, and to an unknown extent, noise. All are currently under active investigation, and proposed management actions are expected to reduce impacts..
- Numerous types of human activities occur that may influence living resource quality; levels do not appear to be changing.
In the past, fishermen in the sanctuary have recovered paleontological remains representing a period when portions of Stellwagen Bank were dry land. However, most of the known archaeological resources are in the form of shipwrecks. Spanning the mouth of Massachusetts Bay, the sanctuary represents the current and historic gateway to several of America’s oldest ports. Vessels entering and leaving Gloucester, Salem, Boston, Plymouth and Provincetown traversed the sanctuary’s waters. Historical records indicate that several hundred vessels sank in the vicinity of the sanctuary.
Shipwrecks resting within the sanctuary’s boundaries have a level of protection unavailable in other federal and international waters off Massachusetts. Sanctuary regulations prohibit moving, removing, or injuring, or attempting to move, remove, or injure, any submerged cultural or historical resources, including artifacts and pieces of shipwrecks (unless under permit or while conducting traditional fishing activities). Anyone violating these regulations is subject to civil penalties.
The extent of the sanctuary’s archaeological inventory is just beginning to be known. Historical research indicates there could be more than 100 shipwrecks in the sanctuary. Sanctuary researchers are systematically exploring the seafloor to locate archaeological sites. They have confirmed the locations of three historic shipwrecks, the steamship Portland and the schooners Frank A. Palmer and Louise B. Crary. After several seasons of archaeological documentation and historical research, the three shipwrecks have been listed on the National Register of Historic Places. In addition to these shipwrecks, sanctuary researchers have located another eight shipwrecks that are now being documented.
Public meetings initiated in 2002 revealed several concerns regarding maritime archaeological resources in the Stellwagen Bank sanctuary. The three primary issues of concern are:
- The need for inventory and assessment
- The lack of a plan for management and protection
- The lack of interpretation.
The following information provides a summary by sanctuary staff of the status and trends pertaining to the current state of the sanctuary’s maritime archaeological resources: