Harmful Algal Blooms

Unfortunately the EPA letter grades don’t tell the whole story. Each summer blooms of toxin-producing cyanobacteria exceed the thresholds for recreational water.

​Since 2009 the Massachusetts Department of Public Health has posted 11 advisories, restricting recreational activity on the river for an average of 48 days each year. These blooms are visible as peaks in turbidity and phycocyanin on data plotted from the EPA’s Charles River Buoy.

​Source: EPA-Charles River Buoy

---

Nutrient Pollution and Eutrophication

In 2007 the Massachusetts Department of Environmental Protection and the EPA drafted a plan to control harmful blooms by limiting the amount of phosphorous entering the river. Chlorophyll a, a measure of algal biomass, was chosen as a surrogate water quality target.

---

While these efforts have succeeded in reducing nutrient concentrations, no change is observed in algal growth.  Summer Chlorophyll concentrations remains elevated above the target levels indicating excessive algal growth, characteristic of a eutrophic condition. 

Source: Lower Basin Nutrient TMDL, MWRA-sampling data

---

Can Floating Wetlands Improve Water Quality?

​This installation is designed to test the theory that enhancing in-river habitat can contribute to the control of harmful algal blooms by shielding zooplankton from the predatory pressure of small fish. We hope that the floating wetland will have a measurable local effect of shifting the distribution of zooplankton from predominantly smaller bodied animals like rotifers, to larger “micro-crustaceans” like copepods and daphnia.

We are currently collecting preliminary data as part of a three year study monitoring changes in zooplankton density, relative abundance, and mean body size. Data and preliminary findings will be presented to the public during each year of the study.