Skip to main content

The lowdown on our lakes

March 12, 2012

SOUTH KINGSTOWN—The Rhode Island Department of Environmental Management (DEM) has released its report on the status of the state’s lakes and ponds. The 147-page report focuses on water quality and the impact of aquatic invasive plant species of Rhode Island’s lakes, providing information on current conditions, methodology, and future strategies for the mitigation of environmental problems.

Rhode Island holds over 237 lakes, ponds, and reservoirs within its borders, covering an area of 20,749 acres. Fifty-nine of those bodies of water, or approximately 24 percent, have documented water quality issues associated with pollutants, as well as fish tissue contamination.

“Our lakes and ponds supply drinking water for the majority of Rhode Island residents and are highly valued resources for active and passive recreation,” said DEM Director Janet Coit. “This report will help ensure an informed discussion as we work to protect the state’s freshwater resources.”

A major concern identified in the report is the effects of blue-green algae blooms on the water quality of the state’s lakes and ponds. The University of Rhode Island’s all-volunteer Watershed Watch program, which has monitored water quality at Rhode Island’s lakes and ponds for 24 years, has been the resource for much of DEM’s current data, and cites a growing need to mitigate the growth of algal blooms.

“Algae are an important and integral part of ecosystems, but can cause problems when they get out of control,” said Linda Green, Executive Director of URI’s Watershed Watch. “They produce, for example, higher levels of phosphorus, and if they grow too much, form ugly surface scum which uses up the oxygen in the water.”

“That is oxygen which is then not available for fish or fresh water mussels, and is thus harmful to aquatic life found in our lakes and ponds,” she added.

The blue-green algal blooms, which are formed from iridescent blue-green algae called cyanobacteria, form in more temperate periods of the year, from the middle of the growing season until winter. According to Green, some strains of cyanobacteria release toxins which can also be harmful to terrestrial animals and people when they are borne by the wind onto shore, and notes that identifying the impact of blue-green algal blooms on the surrounding ecosystem can be difficult.

“You can’t tell just by looking at a lake if it has toxins or not, so we have to err on the side of caution,” said Green. “[The impact of blue-green algal blooms] is a real growing research topic across the country because the algae in lakes are often patchy, and sometimes where the lake is the greenest is not where there is the highest concentration of toxins. It is difficult to pin down.”

“The Environmental Protection Agency (EPA) does not have standards set yet for blue-green algal blooms and the current standards set by the World Health Organization,” she added. “In general, if a pond looks green and gross and you wouldn’t want your dog in it, you don’t want to be in it. That is a handy rule of thumb.”

Green stated that although blue-green algal blooms are more typical of urban-area lakes and ponds, places such as Yawgoo Pond in West Kingston and Pasquiset Pond in Charlestown have had significant blooms in the past.

DEM’s report also details lakes and ponds which have recorded higher than normal levels of mercury. The testing is performed on the tissue of fish, which consume the mercury.

“We’ve had very limited testing of levels of fish,” said Green. “Larger fish eat smaller fish, so mercury is accumulating in their bodies. Once mercury gets into an animals body, it stays in it. There is not a lot of fishing pressure in some of Rhode Island’s lakes where elevated levels of mercury have been found.”

“[The harmful effects of mercury] is why there have been big efforts to get rid of all mercury products, such as thermometers in the home,” she added. “It is a very serious issue.”

Green cited that higher levels of mercury in Rhode Island lakes and ponds are a product of airborne chemicals from coal-burning power plants in the mid-western parts of the United States which precipitate into local aquatic environments.

“In all likelihood, mercury is coming from power plants burning coal, which is a trace contaminant of coal in many cases,” said Green. “Mercury deposition is a big concern across all of New England, which is why the EPA has made efforts through the Clean Air Act to protect air quality and human health.”

DEM’s report also documents the impact of invasive plant species such as variable milfoil and fanwort on Rhode Island’s lakes and ponds. Eighty lakes across the state, or 59 percent of the recorded data, have at least one invasive species within its ecosystem. In South County, invasive species have been found in Worden Pond, although places such as Watchaug Pond in Charlestown are free of them.

“The space invasive species occupy within freshwater ponds and lakes is quite dense compared with native species,” said Hope Leeson of the Rhode Island Natural History Survey. “They create a layer of shade which out-competes many native species. Then when they decompose, invasive species decrease the oxygen levels in the water. That can negatively affect the fish.”

The Rhode Island Natural History Survey (RINHS) is one of the major organizations in the state which trains volunteers and organizes projects to mitigate the effects of invasive species. Leeson noted that greatest danger which aquatic species pose to Rhode Island’s lakes and ponds is that they are often introduced, boats or other aquatic vehicles, into clean environments and spread quickly.

“Variable milfoil, for example, can dry out on a boat and when it comes in to another water body, it can re-grow,” said Leeson.

Leeson furthermore noted that the aquatic environment makes it difficult for volunteers to remove invasive plant species from native ecosystems.
“It is a whole different environment, and invasive species tend to be more widespread,” said Leeson. “As you try to remove the plants themselves, the fragments can get carried, and which we have to be careful to contain so they are not drifting through the water body and replanting somewhere else in the pond.”

“On land, you can control the application [of invasive species removal] better,” she added. “It is difficult even to try and target the plants in the aquatic environment because you have the elements of water, currents and wind.”

Programs such as RINHS, Watershed Watch, and others contribute significantly to public education and awareness of aquatic invasive plant species so that they can recognize threats to native species and mitigate individual circumstances. Formal funding for invasive species removal in the state is minimal and often attached to specific projects, and not more holistic programs.

“It is important from educational standpoint to understand how we all impact a water body and the potential issues of carrying plants from one place to the other,” said Leeson. Education programs are there for people to understand that there are ponds in the state that don’t have invasive species in them, and also to develop an awareness of what is and isn’t an invasive species.”

“We want to eliminate the opportunities for something to arise unexpectedly,” she added.

DEM recognizes that resources for formal invasive species mitigation programs are limited, but will continue to support local lake associations and volunteer organizations with their efforts in removing invasive species from Rhode Island’s lakes and ponds.
For a text of the full report, visit

Southern Rhode Island Newspapers
View more articles in:


Premium Drupal Themes by Adaptivethemes