CR Environmental, Inc. 639 Boxberry Hill Road East Falmouth, Massachusetts 02536 (508)563-7970 www.crenvironmental.com

Lake Massapoag Geophysical and Ecological Surveys
Dunstable, Tyngsboro & Groton, Massachusetts

These not-for-profit surveys are being conducted as part of a multi-tiered assessment designed to address accelerated eutrophication and the spread of nuisance vegetation through this Northern Massachusetts impounded lake.  Current management techniques are limited to cyclic winter drawdown.   This process has had marginal to fair success controlling vegetation in near-shore sandy substrates exposed during winter months, but appears to increase sediment burdens to deeper water.   Hydrophytes inhabiting sediments with poor drainage (organic silts) appear to be less impacted than those in sandy substrates.  CTD and other multi-parameter probes demonstate that meta- and hypolimnetic anoxic waters are present throughout the ice-free months, including periods of isothermal (i.e., same temperature throughout the water column) conditions.  We hope that these surveys, combined with the efforts of the local volunteer lake management group, will significantly assist a formal feasibility study focused on additional lake management options.

Nuisance vegetation inhabiting sub-drawdown elevations appears to be abnormally dense.  The drawdown method does not address primary causes of eutrophication and hydrophytic invasion,  water column nutrient loading (e.g., phosphorus & nitrogen), particularly internal phosphorus flux from deep anoxic sediments subject to increased depositional rates.  The sonar data presented below was collected in order to identify: (1) the thickness of lakebed sediment; (2) geological formations which may influence circulation; and, (3) the extent of anoxic sediment as indicated by apparent methane entrainment and associated intermittently obscured sub-bottom data.  The data below is a small subset of a comprehensive biogeophysical survey project which includes water column chemical/physical profiling, water & sediment sampling, shallow water acoustic Doppler current measurements, and mapping of depth, habitats and vegetation using high-frequency sonar, DGPS and underwater digital photography.

Project Information
NAD83 Massachusetts State Planes, Mainland Zone, Meter
Item	Description	Click thumbnail to see full navigation	Preliminary Bathymetric Contour  Map
Number of Acoustic Data Files	8
Total Acoustic Data Size (MB)	8.6
Total Line Length (Meters)	2257.9