Plymouth Pond & Lake Atlas 2015
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Town of Plymouth Pond and Lake Atlas FINAL REPORT MAY, 2015 Prepared by: Coastal Systems Program School for Marine Science and Technology University of Massachusetts Dartmouth Prepared for: Town of Plymouth Department of Marine & Environmental Affairs Town of Plymouth Pond and Lake Atlas May, 2015 Prepared by: Coastal Systems Program, School for Marine Science and Technology University of Massachusetts Dartmouth Eduard M. Eichner, Water Scientist/Project Manager Brian L. Howes, Ph.D., Director CSP Sara Sampieri Horvet, Senior Technical Associate Prepared for: Town of Plymouth Department of Marine & Environmental Affairs David Gould, Director Kim Tower, Environmental Technician With funding provided by: Massachusetts Environmental Trust Town of Plymouth and Volunteers including the following Associations: Herring Ponds Watershed Association, Six Ponds Watershed Association, Billington Sea Watershed Association, White Island Pond Conservation Alliance, Friends of Ellisville Marsh, Southeastern Massachusetts Pine Barren Alliance, and Sands of White Horse Beach Association This project has been partially funded by the Massachusetts Environmental Trust. The contents do not necessarily reflect the views and policies of Trust, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Plymouth Pond and Lake Atlas 1 May, 2015 EXECUTIVE SUMMARY Plymouth is a town blessed with hundreds of ponds and lakes. Early histories of the town recount use of the ponds for fishing and establishment of herring runs. 1 Later developments show the use of the ponds as drinking water supplies, water sources for cranberry bogs and active management to encourage recreational fishing. In more recent times, Plymouth’s ponds and lakes have become recreational centers and premium prices are paid to live near or along their shorelines. However, as populations around the ponds and lakes have increased, so have concerns about their water quality. Plymouth has an active community of pond associations and the Town of Plymouth has made ponds and lakes a priority focus of the Department of Marine & Environmental Affairs (DMEA). In the late 1970’s the Town conducted baseline water quality surveys for 41 ponds in Plymouth 2, but since then surveys have generally been limited to periodic snapshots of individual ponds. Pond and watershed associations have assisted by collecting limited data with their available resources, but inquiries and concerns from the residents of Plymouth regarding water quality of their ponds have continued to increase. In order to begin to address resident concerns and lay the groundwork for more effective pond and lake management, the Town DMEA working in concert with the Coastal Systems Program, School for Marine Science and Technology, University of Massachusetts Dartmouth (CSP/SMAST) and the local pond associations has begun the Plymouth Pond and Lakes Stewardship (PPALS) program. The PPALS program has begun by organizing past pond water quality data, standardizing procedures for current and future sampling of all ponds, and assessing the current status of 38 selected ponds based on a unified PPALS water quality sampling effort during late summer 2014. These sampling results are included and discussed in this Atlas. This Atlas also includes a listing of all Plymouth ponds and lakes, synthesis of available past sampling data, comparison of current data to past data where possible, and assessment of the current water quality status of individual ponds. This Atlas documents the initial year of an on-going effort to engage and educate the community and provide reliable water quality data for effective management of the ponds and lakes of Plymouth. The first step in the Plymouth PALS program was to identify all the ponds within the Town of Plymouth, gather past sampling results, and identify details to facilitate additional pond sampling. Town and CSP-SMAST staff worked together to develop a town-wide pond database, including numbering of individual ponds, review of potential sampling sites within the ponds, and confirmation of pond access. The resulting Plymouth Ponds database includes a unique number for each pond, its area, whether it has bathymetric (depth) information, the source and age of the bathymetric information, and whether it has a boat ramp. The Plymouth Ponds database shows there are 450 ponds within the Town of Plymouth with a total combined area of 5,002 acres. Among this count, 83 ponds are greater than 1 Thacher, J. 1835. History of the town of Plymouth, from its first settlement in 1620, to the present time. Marsh, Capen & Lyon, Boston, MA. 2 Lyons-Skwarto Associates. 1970. A Base Line Survey and Modified Eutrophication Index for Forty-One Ponds in Plymouth, Massachusetts. Volumes I-V. Westwood, MA. Plymouth Pond and Lake Atlas i May, 2015 10 acres and are, therefore, Great Ponds under Massachusetts law and 130 of the ponds have assigned PALIS numbers under the MassDEP pond numbering system. Fifty-four (54) of the ponds have bathymetric/depth information, which is slightly more than the 41 bathymetric surveys completed for the initial 1970s baseline survey. 3 The largest portion of the ponds (46%) are less than 1 acre, but review of the aerial maps shows that all of these have standing water during even low groundwater conditions. 4 The pond list also includes 18 artifical ponds created after 1995; these are mostly golf course ponds although a few were created and/or expanded for use in cranberry bog operations. Review of this database indicates that basic physical information, such as bathymetry/depth data, is a significant data need for effective assessment and management of Plymouth ponds and lakes. Working with the local pond associations, the town and CSP-SMAST worked to develop a pond sampling list for the inaugural 2014 Plymouth PALS Water Quality Snapshot. The pond sampling list was developed based on ease of access, community interest, and whether depth/bathymetric information was available. A sampling protocol was developed based on the Cape Cod PALS sampling protocol, which has been used for 13 years. The protocol and other associated sampling procedures (such as sample handling and transfers to a laboratory) were incorporated into a Plymouth PALS QAPP that was approved by MassDEP. As part of project quality assurance, the town and CSP-SMAST staff conducted a training session on the sampling protocol for the Plymouth pond volunteers. For freshwater ponds in the Plymouth region and Cape Cod, the poorest water quality conditions generally occur in late summer, making this period the primary focus for management. Between August 15 and September 15, 2014, volunteers and town staff used the PPALS procedures to collect 104 water quality samples from 39 ponds. The collected samples were analyzed at the Coastal Systems Analytical Facility at SMAST-UMass Dartmouth using standard procedures for the following constituents: 1) pH, 2) alkalinity, 3) chlorophyll a, 4) pheophytin a, 5) total phosphorus, and 6) total nitrogen. While samplers were at the pond, they also collected measurements of dissolved oxygen and temperature throughout the water column and water clarity. Results from the 2014 Plymouth PALS sampling generally conform to other overviews of ponds and lakes in the ecoregion. Based on the water quality data, all of the ponds were phosphorus limited, which means that phosphorus levels are the key to water quality management. Three ponds had ratios close to nitrogen/phosphorus balance point which would suggest management control of both nutrients, but this would have to be explored in more refined, pond-specific assessments. Total phosphorus (TP) concentrations showed that 15 of the PPALS ponds (39%) had surface levels that sufficient to cause impairment. Most of the ponds (26 of 36) have TP concentrations in their deep waters that are higher than in the surface layer and, of these, 13 have deep water concentrations that are more than twice as high as their surface concentrations. Ratios greater than two indicate significant sediment TP regeneration into the overlying water column from the sediments. Review of ponds either above or below the TP thresholds does not initially appear to be related to their location, surrounding level of development, or size. This 3 Lyons-Skwarto Associates. 1970. A Base Line Survey and Modified Eutrophication Index for Forty-One Ponds in Plymouth, Massachusetts. Volumes I-V. Westwood, MA. 4 Based on comparison of USGS groundwater water level monitoring in Plymouth and dates of Google Earth aerials. Plymouth Pond and Lake Atlas ii May, 2015 finding combined with the sediment regeneration results suggests there are other factors, such as basin depth, stream inflows or historic uses, which would need to be evaluated in individual pond assessments to determine the causes of current water quality conditions. Phytoplankton pigments were measured as an indicator of phytoplankton/algal biomass in the water column. Concentrations of phytoplankton/algae pigments generally match up with the phosphorus results, although slightly more ponds have excessive chlorophyll-a concentrations. Twenty (or 51%) of the PPALS ponds had phytoplankton biomass levels that are consistent with habitat impairment. The average chlorophyll-a concentration among all the ponds sampled in the 2014 Snapshot (3.6 µg/L) was more than twice the ecoregion threshold. If pheophytin-a and chlorophyll-a surface water concentrations were added, only one pond had a combined concentration