By Don Williams
The burning water quality question is will we have a cyano bloom this summer? We know that higher phosphorus pollutant levels, higher water temperatures and more sunny days favor cyanobacteria blooms. I looked back at existing data for 2019 (no cyano bloom), 2020 (bad cyano bloom) and 2021 (mild cyano bloom) and compared it what we have so far this year. The early algae bloom this spring could reduce the phosphorus level in the pond but, in fact, phosphorus is a bit higher this April and May than in April and May of 2021. In addition, thus far the 2022 water temperature is higher than the 2021 water temperature. On the other hand, the 2022 April phosphorus concentration is the same as it was in April 2019, a year in which there was no cyanobacteria bloom. Our fate may depend on how warm the water gets in the early summer. Geri is using the fluorometer that Plymouth bought for us (the value of a good partnership!) to monitor phycocyanin which increases with higher cyanobacteria level. Cyanobacteria is always present at a low level but only “blooms” when heat and pollutant conditions are right. By watching the phycocyanin level trends and water temperature, we may be able to predict whether there will be a bloom or not.
The Herring Ponds Watershed Association will attend the July 12 Plymouth Conservation Committee virtual Zoom meeting to ask for more enforcement of Plymouth’s regulations regarding clear cutting next to the pond. The number of pond front homeowners cutting down trees in the 35 foot “no touch” buffer adjacent to the pond shore is rapidly increasing and jeopardizes HPWA’s and Plymouth’s efforts to protect our fresh water. You can read about the importance of a vegetated buffer in another aricle in this newsletter. If you wish to sit in, Zoom information is posted on the Plymouth Conservation Commission website four days before the meeting. A show of solidarity will help our cause.
We will take water samples near the Great Herring Ponds beaches on June 23 to have E. coli results before the July 4 holiday. We will take these samples every summer month to make sure there is no E. coli bacteria present. E. coli can cause severe gastronomical distress when ingested and is especially harmful to pets and young children. We have never seen unsafe levels but it’s better to be vigilant.
Plymouth is paying for our general quality samples that we are taking monthly from April thru October (a really good partner!). Every year we track total phosphorus, pond clarity, dissolved oxygen, etc. at different depths to monitor overall pond health and detect both good and bad trends.
On our own, we are looking at total phosphorus and nitrate at the idle bog north of Little Herring Pond (LHP), the northernmost spring feeding LHP (which eventually winds up in Great Herring Pond (GHP), the north, central and south thirds of LHP, Carters River and GHP. The measurements are tracking pollution. The spring is the purest water than we can expect since it comes from the underlying aquifer. We can subsequently follow what happens to the pollutant levels as the water makes its way to GHP. We know from this data, for example that the idle bog has very high concentrations of phosphorus pollutant that it can feed into our water system when bog water is high, e.g. after a storm. We have also seen that pollutant levels are very low in the spring for GHP, builds up during the summer months and then decreases again in the fall. Our data over the last 3 years should give our consultant enough information to chart how much GHP pollution is due to the bog and/or LHP. This could be very valuable since if some of our phosphorus problem comes from LHP, fixing that could be a lot less expensive than treating the much larger GHP.