Nuisance Algae + HAB

Nuisance Algae and Harmful Algal Blooms of Buzzards Bay

Related Pages:   Nuisance Codium off Wareham   Sub page: Red Tide and PSP

There are a number of nuisance algae found in Buzzards Bay. Some of these species have become problematic because of increased eutrophication of coastal waters from excessive nitrogen from the land from fertilizer use and wastewater disposal. Some species were introduced from other areas. Some single-celled species (phytoplankton) may become so concentrated in the water they color it. These latter harmful algal blooms can be caused by a combination of factors relating to rainfall, temperature, and abundance of phytoplankton grazers.

Filamentous algae

In our region there are several genera of similar looking filamentous uniserate (strand of single cells) marine algae. These include species of the green alga Cladophora and Ulothrix, and several species of brown algae, most notably Pilayella and Ectocarpus.

The specimen in the panel to the right was delivered to us in April 2008 from Westport. This fine slimy feeling brown filamentous algae was purportedly densely covering floats and pilings in Westport Harbor. Although the specimen lacked reproductive structures, which would have helped in its positive identification, based on color, cell form, size, and branching, we identified it as Pilayella littoralis. Early spring 2008 was wetter than normal which would have added more nitrogen to Wareham’s waters from land sources. This species is known to thrive under eutrophic conditions. Pilayella is also referred to as “mung” by some locals, and you may find this Cape Cod newspaper article of interest: Cape Cod newspaper article.

Pilayella and other algae in the subtidal. 15 cm container full of Pilayella. Microscopic view Pilayella.
The filamentous brown algae Pilayella littoralis. Photo credit: Dr. Joe Costa.


Drift Algae

Drift algae is a generic term for unattached algae that can accumulate and grown on the bottom of protected embayments. Cladophora is one of the more common species, especially in eutrophic embayments where it has the appearance of balls of green steel wool.


Codium Floating on the Water
A fragment of Codium floating on the water.

Codium fragile spp. tomentosoides is an invasive nuisance algae from the Asian Pacific. It was first reported on the East Coast on Long Island in 1957, and first observed in Buzzards Bay in 1961 (Carlton and Scanlon, 1985; Pederson et al. 2003). Throughout the 1960s to the present, Codium has continued to spread up and down the US coastline and into Canada, and is even a nuisance species in faraway places like the Baltic Sea and Australia (Global Invasive species database). Scientists believe it is primarily transported from site to site on the hulls of ships.

Codium is a robust alga with a sponge-like texture, often growing in two-foot across bush-like shapes. While this alga can crowd out and shade other plants and algae, one of the most serious problems with Codium is that it is a killer of shellfish. It does this by the simple act of growing on shells, and causing them to be smothered (in the case of oysters it is nicknamed the oyster thief), or causing the shellfish to be pulled up from the bottom and washed ashore. In Buzzards Bay, this is a common occurrence for whelks, slipper shells (Crepidula), and bay scallops. The accumulation of dead shellfish in Codium wrack is one of the main reasons why this beach wrack smells stronger, and attracts more flies, than the native eelgrass beach wrack.

Read our article on a Codium population explosion off Wareham.