Friends of Sengekontacket, Inc

State of the Pond Report for 2004

With the assistance of William Wilcox, Water Resource Planner with the Martha’s Vineyard Commission, the Friends of Sengekontacket has prepared a “State of the Pond” analysis for 2004.  The “Friends” intend to prepare this report on an annual basis.

1.  Pond Quality

Sengekontacket Pond is a shallow, 700-acre coastal salt pond and is connected by a culvert to another tidal water body called Trapp’s Pond.  In a preliminary review, William Wilcox, of the Martha’s Vineyard Commission, stated that 2003 water quality in the system generally fell into the good to fair range for the key parameters: phytoplankton pigments, inorganic nitrogen, total organic nitrogen, transparency and oxygen saturation.  The data for 2004 is still being collected and analyzed, but it is felt that water quality has remained stable or improved slightly.

In brackish and marine water bodies, the addition of significant amounts of nutrients, especially nitrogen, can stimulate excess plant growth, which will eventually die, settle to the bottom of the pond, and decay.  Bacteria then feed on the decaying plants consuming much of the available oxygen in the water, leading to a decline in water quality.  In severe cases, the body of water becomes unsuitable for marine life.

Nitrogen is introduced into the system by acid rainfall and by sources in the watershed including wastewater disposal, fertilizers and storm water run off.  Brian Howes, a Professor at the University of Massachusetts, Dartmouth, recently said on the Vineyard that eighty percent of nitrogen loading is from septic systems.  “We need to be looking at development in the watersheds,” said Mr. Howes.  Nitrogen is removed from the system by deposition of dying vegetation to the bottom sediment and by tidal exchange with Nantucket Sound.  Sengekontacket Pond is vigorously flushed by the tides and the residence time for nutrients entering the system is about 3 days.  This is good, as the quicker the nitrogen entering the system is removed to the Sound, the less plant growth is stimulated.  Upper and lower Trapp’s Pond is not as lucky since it flushes through an inadequate culvert on Beach Road.  As a result, Trapp’s Pond and portions of Sengekontacket have been closed to shell fishing for most of 2004.

There are many measures of resource water including chemical analysis, phytoplankton quantities, the mass of algae, the eelgrass bed condition, production of shellfish and fin fish to name a few.  The following is a brief summary of the condition of Sengekontacket Pond:

• Sengekontacket displays relatively clear water.  Summer Secchi depths are typically well over 1 meter and, in 2004, were up to 2 meters.  Secchi depths are measured by lowering a black and white disc into the water and recording the depth when it is no longer visible.  The favorable clarity is the result of somewhat less phytoplankton production than occurs in other similar ponds, like the Lagoon. 
• The pond is host to large number of green crabs that are predators of small shellfish.  They probably play a role in the smaller harvest of bay scallops from the pond. 
• Nutrients entering the pond appear to be primarily utilized in production of wrack algae and growth of slime coatings rather than in phytoplankton.  Wrack algae production has been excessive in Major’s Cove, Trapp’s Pond and embayment on the west side of the pond, south of the main inlet channel.
• Salinity is typically about 30 ppt unless sampled in the recesses of the pond where fresh water becomes more dominant.  This is a result of vigorous tidal circulation that exchanges 95% of pond water for new, Nantucket Sound water about every 3 days.  As a result, the availability of nitrogen is limited by flushing.  By comparison, salinity in Nantucket Sound is about 35 ppt.
• Sediment from Sylvia State Beach continues to enter the pond from the two openings causing shoaling and reducing tidal flushing.  A preliminary observation appears to indicate that the existing openings for the Big and Little Bridges are adequate for flushing, but it is uncertain whether circulation could be improved with larger openings.
• In a preliminary observation, water quality in the system during 2004 has probably not deteriorated from 2003.

2.   2004-2005 Sengekontacket Pond Mitigation and Preservation Activities

During 2004, the Friends of Sengekontacket, Inc., the Commonwealth of Massachusetts, Martha’s Vineyard Commission, and the Towns of Edgartown and Oak Bluff have been active in a number of programs that have significant potential to limit damage to Sengekontacket Pond from excessive nutrient loading.  The bottom line for pond health is to reduce excess nutrient and nitrogen loading, enhance tidal flushing, and improve circulation within the Pond.  Here are some of the efforts:

The Massachusetts Estuary Project.   The Massachusetts Estuaries Project (MEP.) was initiated to address the problems of excess nitrogen discharge into the estuaries and embayments of southeastern Massachusetts.   MEP has become the crown jewel of estuary and embayment mitigation efforts in southeastern Massachusetts.   The MEP is a joint effort of the Department of Environmental Protection (DEP), The School of Marine Science and Technology (SMAST) at the University o Massachusetts – Dartmouth, USEPA, Martha’s Vineyard Commission, the communities, and the Governor’s Office.  During 2004, the Estuaries Project collected twenty sediment cores for analysis of nutrient release from bottom mud.  In 2004 the Project collected continuous dissolved oxygen, chlorophyll, salinity and temperature data using four automatic recording devices from UMASS.  Volunteers from the “Friends” supplemented that effort and collected samples twice a week until the automatic devices were installed.  These are two of a number of key components to the Estuaries Project process.  Once MEP participation of  Sengekontacket Pond is funded by the towns and the Commonwealth, the Estuaries Project will produce an evaluation of the system and identify tools and recommendations to improve water quality. 

In addition to calculating and monitoring the Total Maximum Daily Load (TMDL) of nitrogen, UMASS’s computer models will be adapted to Sengekontacket conditions and will be available to Martha’s Vineyard’s government agencies to evaluate the potential impact of future growth in the watershed and evaluate options to reduce adverse effects.  For example, the MEP computer programs can predict tidal exchange and show the effects of dredging programs.   Knowledge from the MEP should be of assistance to manage dredging, mitigate shoaling and increase tidal flushing and circulation. 

We hope to see Sengekontacket formally enter the program in the spring or early summer of 2005.  The Friends of Sengekontacket, Inc. fully endorses the Massachusetts Estuary Program and will continue to be a strong and active co-partner.

Eel Grass and Bay Scallop Restoration.  Sengekontacket once had large eelgrass beds so thick that boating and sailing were very difficult.  Eelgrass is a wide-bladed, brown-green plant that grows in shallow brackish tidal ponds and bays, and is essential for the production of bay scallops and other important residents such as eel and blue crabs.  Bay scallop larvae are attached to the blades and then the mature scallops remain in the eelgrass bed.  For forty or fifty years Sengekontacket had an abundant harvest of scallops, then the eelgrass beds started to die out in the 1980’s.  If there is no eelgrass in Sengekontacket Pond, there will be few if any bay scallops to harvest.  The loss of an eel grass bed is often the first sign of the loss of ecological health in a salt water pond.  The exact cause of the die out in Sengekontacket is unknown, but could be the result of disease or nutrient excess or a combination of factors.  A possible culprit could be a wasting disease that wiped out eelgrass in the 1930’s.  At this time the only eelgrass remaining in the system is in upper Trapp’s Pond, the inner reaches of Major’s Cove and Farm Pond.  Aided by a grant of $3,100 from the Friends of Sengekontacket, Inc., MVC’s William Wilcox and the two town shellfish wardens began an aggressive program of restoration in 1999.  In 2004 the team harvested eelgrass seed stalks from Trapp’s Pond and brought the grass to Sengekontacket.  Mr. Wilcox hopes that 40,000 seeds will be available for germination with a survival rate of 10%.  “It is a start,” Bill Wilcox said.  FOS Inc will continue support for the eelgrass restoration program.

The FOS Watershed Outreach Program.  Aided with a grant from the Edey Foundation, FOS, Inc. launched a program in 2004 to reduce excess nutrient pollution from households and non point sources within the Sengekontacket watershed.  Led by FOS director Hap Hamel, a brochure was prepared describing sound ecological practices that would reduce nutrient loading in the Pond.  During the summer months, volunteers from the “Friends” delivered the brochure to almost every household in the watershed. 

Land use development has a negative impact of excess nutrient loading by the use of lawn chemicals, septic effluent, and reducing the ability of the watershed to naturally remediate nitrogen and other nutrients.  Non point pollution is now the nation’s key source of nutrient pollution in our waterways.  This outreach program will be a continuing effort by the Friends.

The FOS, Inc and Dukes County Barrier Beach Task Force (BBTF) is co-chaired by County Manager E. Wynn Davis and FOS’s Christina Miller.  BBTF is a group of government and community leaders with a goal of producing a barrier beach management plan that will:

• Balance the environment and recreational users.
• Plan for the structural. integrity of the barrier beach system.
• Protect rare and endangered species.
• Enhance the water quality of Sengekontacket Pond.
• Provide a safe, pleasant, accessible and family friendly recreational facility.
• Combine the needs of transportation with recreation and the environment including the replacement of both bridges.

The Friends of Sengekontacket, Inc. will continue its support of the BBTF in 2005 and beyond.

Other Mitigation.  Both towns have an active program to rid Sengekontacket Pond of Green Crabs in order to encourage the restoration of both the eelgrass beds and bay scallops.  The towns continue to introduce contaminated clams to the pond to gradually help cleanse the Pond of nutrients by filtering out microscopic plankton.

The Friends of Sengekontacket, Inc., appreciates the cooperation and leadership of the Martha’s Vineyard Commission staff and both of the town’s shellfish wardens in preservation efforts.