Harbor News

Rusty-Colored Algae Floats Again in Buzzards Bay

This summer marked the fourth summer since 2005 that Baywatcher volunteers reported cloudy streaks of rust-colored water in Buzzards Bay – the sign of abnormal amounts of Cochlodinium polykrikoides, a dinoflagellate, which is a type of phytoplankton or single-celled algae. Dinoflagellates, such as Cochlodinium, naturally occur in Buzzards Bay and are likely present all the time, but usually occur in significantly less densities.

Whenever there is a population explosion, or “bloom,” of these microalgae, cell densities may exceed millions of cells per liter of water. Characteristic of all dinoflagellates, Cochlodinium cells have two flagella, or thin, whip-like outgrowths used for swimming, and armored plates of tissue. However, Cochlodinium cells also contain reddish pigments that give the water a rust-colored hue when high densities of this organism accumulate at the surface.

Although a Cochlodinium bloom looks rusty-red, it is not the type of algae that is injurious to humans, such as the red tide alga, Alexandrium, which contains a toxin that attacks the nervous system in marine animals and humans. Cochlodinium does not contain any toxins; however, if a Cocholodinium bloom becomes large enough, especially in a semi-enclosed system such as a bay or harbor, it can kill fish, as the overabundance of algae consume all of the oxygen in the water. Large concentrations of Cochlodinium may also affect the growth, survival and development of some shellfish, such as oysters, but much remains unknown about these effects, and thus, is the focus of ongoing research.

Algae blooms tend to occur when environmental conditions such as temperatures, nutrients, and turbulence change, triggering the rapid growth of algal cells. For example, when a long dry spell is followed by heavy rains, nutrients such as nitrogen and phosphorus contained in farm fertilizers, animal wastes and sewage-treatment-plant discharges are flushed into the bay. This addition of excess nutrients to the bay fuels the production of algal blooms similar to how fertilizer promotes the growth of your lawn or garden.

“These blooms appear to be increasing in frequency, which is an indication that significant changes are occurring in Buzzards Bay,” said Coalition Director of Monitoring Programs Tony Williams.

According to Dave Whittaker, Senior Marine Fisheries Biologist at the Massachusetts Division of Marine Fisheries, this “rusty tide” has occurred in Buzzards Bay long before 2005, but blooms were more sporadic.

“In the last three or four years, blooms have been much more regular and pronounced with a much greater spatial distribution,” Whittaker explained. “We actually had a bloom as late as three weeks ago in Clarks Cove in New Bedford following that last extremely heavy rain event. With the size of these blooms, thank goodness Cochlodinium is not harmful to humans.”

This year Baywatchers first began reporting observations of rusty-colored water at the end of July in Fiddlers Cove, which was about three weeks earlier than last year’s initial report. Baywatchers then reported seeing blooms two weeks later in August in Wings Cove, the Wareham River, West Falmouth Harbor, and Snug Harbor.

Tracking trends, such as recording the occurrence of these “rusty tide” events, is critical to understanding the changing health of the bay and how human activities impact the bay ecosystem. As the Coalition’s 2007 State of the Bay Report reveals, the overall health of the bay is declining and algae blooms are just one sign of troubled waters. The Coalition will continue to monitor the bay’s health and collect long-term data to provide the information necessary to make informed, science-based decisions about the restoration and protection of Buzzards Bay.

The Coalition needs your help in monitoring the health of Buzzards Bay. If you observe an algae bloom in Buzzards Bay, immediately contact Tony Williams, Coalition Director of Monitoring Programs at 508-999-6363 ext. 203 or e-mail at williams@savebuzzardsbay.org, with the location and a description of the bloom.