What We've Been Noticing
The Weed Warriors
FPAC's Weed Warriors program continued this year with a small group of volunteers keeping an eye on different areas of the pond (FPAC would love to expand this group!). FPAC is happy to report that no invasive aquatic plants were reported as being present in the pond this year! Farm Pond fortunately continues to be free of invasive aquatics as far as known, unlike just about every other lake/pond in our area.
A motorized craft was observed on the pond several times this past season. The bylaw against such crafts is in place to keep petroleum out of the pond, avoid added noise, avoid wakes that could cause erosion of the shore, and preclude the introduction of weeds or invasive species that may be attached to boats or motors coming from nearby ponds/rivers that are full of invasive weeds. FPAC is aware of these observations with plans to help discourage this activity through continued education for all residents.
You may have come across press reports in recent years about many Massachusetts lakes and rivers experiencing large blue-green cyanobacteria "blooms". A few small and scattered HCB (sometimes also referred to by the older term HAB) blooms (less than 1/2 foot in width) were reported in Farm Pond this summer. These blooms appeared as patches of localized green "scum" and have been described as looking like spots of paint floating in the water. Several initiatives were implemented by FPAC and the Town to help identify and respond to HCB blooms over the past 18 months. A subcommittee of FPAC worked with the SYC to set up a Cyanoscope microscope and HCB sampling kit in the SYC shed. Weekly, and whenever any sign of potential HCB blooms were observed, we collected a sample for microscopy identification. Once a month, we also delivered Farm Pond water samples to the City of Worcester's lab for additional HCB testing (Worcester Cyanobacteria Monitoring Collaborative). The microscopy work and lab analysis of these water samples found frequent occurrences of potentially harmful cyanobacteria (HCB)s present in low abundance in Farm Pond in 2021.
We took three types of samples throughout the summer: surface grab samples, 1-meter integrated tube samples, and 10-meter plankton mesh net samples. A summary report on the HCB findings will be finalized and shared after the last of the data comes back from the WCMC program. Detection of even low levels of potentially harmful Cyanobacteria in our pond continues to pose a threat of larger blooms that could release cyanotoxins under the right conditions.
Most recently, a green algae (not capable of cyanotoxin production) bloom of about 10 feet length was observed in early October along the shore between the public boat ramp and the Sherborn Yacht Club (SYC) dock, submerged in about 3 feet depth of water. It was found not to be from potentially harmful cyanobacteria but rather was identified via microscopy to be a common green algae. The green algae bloom in this photo was identified as Mougeotia, a green algae very commonly found in shallow ponds and wetlands in our area. But this is the first time we have seen such a large green algae bloom at Farm Pond.
Because there were confirmed HCBs noted in 2020 and 2021, the town posted signs at the entrance to the public beach and boat ramp all season to warn swimmers and pet owners that HCBs had been observed. FPAC drafted an Emergency Response Plan for responding to blooms. This document is still in draft form and under review. We hope to have it finalized and published by next spring. Additionally, FPAC and the Town are exploring funding sources and planning to upgrade erosion control systems at the parking lot, boat ramp, and the beach to significantly reduce surface runoff from these areas.
E Coli Levels at the Town Beach
High E Coli bacteria levels were detected in water samples at the Town beach in mid-August and are attributed to higher water temps and the increase in the numbers of geese which gets worse during this annual geese molting season (late July through August); see a good resource from MA Div Fish and Wildlife on geese behavior. This coincides with the time when the beach is no longer staffed (when the lifeguards start to leave for college). The geese like to gather on the beach during the molting season when they are unable to fly, plus there is a reduction in human presence to scare them away. The high E Coli numbers shut down swimming at the beach for several weeks due to Sherborn BOH and MA DPH regulations. This year, snow-fencing went up along the beach waterfront after the lifeguards were no longer staffing the waterfront. Volunteers from FPAC attended to the fence each evening to make sure it was securely staked (swimmers and visitors to the pond on warm days often moved the fencing). The town was unsuccessful at finding a service to scare away the geese with dogs and will be looking into other measures to deter the geese next year. FPAC and the town are also developing a plan for next year to deter geese when we lose waterfront staff.
Water Quality Testing
FPAC and volunteers conducted twelve sampling events at the sampling mooring at the center of Farm Pond. Two concerning trends observed in the last two seasons at Farm Pond have been: 1) lower Secchi disk transparency depths (water clarity), and 2) slightly increasing Total Phosphorus concentrations. Phosphorus is a naturally occurring element that feeds lake plankton (green algae, cyanobacteria, etc), a normal situation of any lake ecosystem. But too much phosphorus can put a lake out of balance, triggering cyanobacteria blooms (the HCBs described above) that turn water green, degrade wildlife habitat, and potentially harm human and pet health.
We would like to start monitoring a few times a year the concentration of Total P in the lower depths (sediment bound Phosphorus gets released into the water as bottom water layer dissolved oxygen levels go under 2 milligrams per liter, which happens every summer during times of stratification). With the expected general trends of higher temperatures (water and air) and longer time periods of elevated temperature due to climate change, we may be facing a slow continued increase in Total P throughout the water column at Farm Pond (and related negative effects - lower water clarity, greater chance of HCB blooms, green algae blooms, non-native invasive weeds, etc.). FPAC has consulted with lakes experts in MA and other states. We have conducted two rounds of Total P sampling in October and November using a new horizontal depth sampler, allowing for water sampling near the lake bottom in addition to our annual surface Total P sampling.