Findings: lots of duck clams, clam worms and
some soft-shell clams.

 

Washing the mud to collect clams and worms

 

Upper Mill River, Gloucester
Clam Survey

Thanks to all the 2009 volunteers who helped with the clam survey. We did it in two days!

Report and pictures will be updated soon.

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Salem Sound Coastwatch is conducting a benthic survey to monitor change in the Mill River inter-tidal zone (formerly an impoundment) after the installation of the new tidegate. The first sampling took place in October 2008 with repeat monitoring to take place in the fall of 2009 and 2010. The restoration and associated monitoring of the Gloucester Mill Pond is supported by technical and financial assistance from the Massachusetts Wetlands Restoration Program, the NOAA Restoration Center/ Restore America's Estuaries partnership, and The Massachusetts Corporate Wetlands Restoration Partnership (CWR) (from Bruce J. Anderson Foundation and Metcalf Eddy, Inc).

As part of the Bruce J. Anderson grant, SSCW conducted educational activities with the O'Maley sixth graders.

Maps of the Study Site

2008 Summary of Findings:

1. The first benthic shellfish and worm survey in the upper Mill River since tidal flow restoration found a return of benthic marine species.

2. Soft-shell clams immediately recolonized the newly exposed mudflats in 2004.

By aging the Mya arenaria (soft-shell clams), it is apparent that colonization occurred as soon as the tide gate was opened in 2004. From her study of M. arenaria in Gloucester, Brousseau (1978) established a life table (see report, Appendix 6). Extrapolating the life table to the upper Mill River places the majority of M. arenaria to be 3 to 4 years in age. Five clams were in the two-year class range and one within the under one-year class.

3. Macoma balthica (duck clam) was the dominant species.

A species of small saltwater clam in the family Tellinidae, M. balthica lives in muddy bays and is quite tolerant of low levels of salinity. its shell color normally varies between pink, purple, yellow, and white, but the Mill River specimens had blackened shells from sulphide-rich sediments (Budd 2001). Also, important to note is the fact that M. balthica are not filter feeders. They live a few centimeters below the surface and are deposit feeders. Their long inhalent siphons sweep over the mud, like vacuum cleaners. The tidal restriction and muddy conditions of upper Mill River provide the ideal habitat for Macoma balthica.

4. Initial findings are encouraging. However, community recovery in restored estuarine ecosystems is largely dependent on the level of tidal exchange. Estuarine structure and function return relatively quickly when tidal flow is unrestricted. Sites with only partial tidal exchange may never fully recover without additional modification of the hydrologic regime (Thelen 2007; Burdick et al. 1997). It appears that the levels of salinity at the mudflat are affecting the density and location of saline sensitive marine species, such as Mya arenaria.

To read more,  
2008 Benthic Survey Report

Gloucester Times article 2008:
New life in the old Mill Pond

Cape Ann Beacon article 2008:
Restoration brings clams back to Mill Pond in Riverdale

Collecting the mud to sample