Three Bays Preservation Inc. Identifies Cause of Rust Tide Throughout Estuary

Monday, August 29, 2016
Media Contact:  Lindsey B. Counsell, Exec. Dir.

(Osterville, Mass.) – Three Bays Preservation Inc. has confirmed the principal cause of Rust Tide, the worst algae bloom to hit North, Cotuit and West Bays in over two decades, and one that has recently tinted the water a rusty red, and due to resulting low oxygen has killed dozens of fish in the 1,251-acre estuary.  

Although other species of algae are present, the chief culprit of this summer’s unwelcome bloom is a common saltwater microscopic organism, or plankton, called a dinoflagellate (Cochlodinium polykrikoides) that can quickly multiply or “bloom” in the upper water column.  Several factors can nurture a bloom of this magnitude including lack of rain and sustained sunny conditions and warm water temperatures.  All of these circumstances and especially the high water temperatures were present in Three Bays and many other estuaries throughout the region this summer.

“Our findings have been confirmed by Dr. Brian Howes of UMass Dartmouth’s School for Marine Science and Technology (SMAST,) as well as the Massachusetts Division of Marine Fisheries,” according to Lindsey B. Counsell, executive director of Three Bays Preservation Inc.   Surveys done by Dr. Christian Petitpas, also at UMass Dartmouth, have quantified the distribution and number of this nuisance plankton throughout Three Bays.

Phytoplankton blooms are prevalent throughout the region this summer, growing on nitrogen leaching from local septic systems, fertilizers and other land based sources that far exceed the state’s recommended threshold.  Other pollutants that are adding stress to our waters such as metals and hydrocarbons add to the problem and are known threats to water quality, human health, and can be extremely toxic to fin and shellfish, and plant life.  

“The hopeful news is we have a comprehensive plan to restore the Three Bays,” clarified Counsell.  Three Bays advocates both traditional—such as conventional sewers—and non-traditional methods, like rain gardens that use native plants to filter rainwater piped from storm drains before it flows into the bays, and ecological restoration projects that return an impaired ecosystem to a healthy state. The restoration plan for historic Mill Pond in Marstons Mills, for example, includes the removal of dense organic sediment and an increase in nitrogen elimination that will be protective of the receiving waters of Three Bays. Also, artificial floating wetlands are being examined, that utilize plant roots to absorb and synthesize dissolved nutrients.

These innovative technologies and many others are in the Town of Barnstable’s 208 Plan that Three Bays Preservation helped draft.  Section 208 of the Clean Water Act requires states and local governments to develop and implement plans to mitigate the impacts of wastewater, improve water quality, and eliminate point source discharges of pollutants.  The so-called Cape Cod 208 Plan focuses on a new watershed-based approach to ecosystem restoration and was developed and drafted by the Cape Cod Commission.

Huge algae blooms remain a vivid reminder of the tough shape our bays are in, and the need for the implementation of the 208 Plan.

Chlorophylls inside the bodies of this particular dinoflagellate make the animal red, in turn tinting the water rusty. This naturally occurring algae blooms globally but has been noticeably present in parts of the Chesapeake Bay and along the East coast. Rust tide may not be harmful to humans, but it’s certainly not inviting to swimmers, boaters and others who are winding up their summer with recreational activities in the Three Bays. Once the rust tide dies and settles to the bottom, it will join the other brownish masses of algae and it will begin rotting on the shores, and “add to the brown muck that covers much of the bottom of the bays and coves and can result in low oxygen and fish kills,” Counsell reminded. This decaying algae also releases nitrogen back into the water which further worsens the nutrient crisis in North, West and Cotuit Bays.

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Three Bays Preservation Inc. is dedicated to restoring and protecting West, North and Cotuit Bays, and the coves, ponds, rivers and streams that form our watershed and ecosystems. Since 1996, Three Bays Preservation Inc. has continued stewardship efforts through applied science, educational programs, and ecosystem-based management practices. To learn more, visit Three Bays Preservation online at