Daily Invader

Chesapeake Bay Algae and Diatoms

Knotted Wrack (Ascophyllum nodosum)


Knotted Wrack (Ascophyllum nodosum) is an example of natural dispersal and a human-mediated introduction.



Knotted Wrack is seaweed (algae) that attaches to rocks and other hard shoreline habitats or just floats around in the surf. It grows on both coasts of the North Atlantic and is common on rocky shores from Portugal to the White Sea in Europe, on the coasts of Iceland and Greenland, and from Baffin Island to Delaware. Floating plants have been collected in the eastern Atlantic off the coast of Ghana just south of the equator and in the Chesapeake Bay region. Seaweed collected along the coastline was likely carried in from the North in currents and is probably largely a result of natural dispersal. But because Knotted Wrack is widely used as a packing material for baitworms shipped from the Maritime provinces of Canada and New England, it probably also arrived through discarded bait. The seaweed is commonly dumped on the shore or water by fisherman and is the most probable mechanism for introduction to upper Chesapeake Bay. Complete Record


Red algae (Bonnemaisonia hamifera)


Red algae (Bonnemaisonia hamifera) was discovered in Chesapeake Bay in 1968.


This species of red algae was discovered in Chesapeake Bay in 1968. It has been found in many parts of the world and has a very complex life cycle with several life stages. It is believed to be from Japan because Japan is the only place where all of the stages of the life cycle have been found. The stages of this species look very different from each other and at one time were thought to be difference species. In Europe and North America it is able to propagate vegetatively (asexually), which contributes to its spread. In Chesapeake Bay, however, this alga is rare and has no reported impacts, but it could impact sea grass beds as it has done in New England. Complete Record


Dead-Man's Fingers (Codium fragile ssp. fragile)


Dead-Man's Fingers (Codium fragile ssp. fragile) is a widely introduced seaweed from Japan.




Dead Man's Fingers is an algae named for its spongy finger-like branches. The subspecies Codium fragile ssp. Fragile is believed to be native to Japan but has been widely introduced through a variety of means including hull fouling and discarded packing material. It is found in much of Europe, the Azores, Australia, New Zealand, and the United States. A patch of Dead Man’s Fingers was first discovered in Assateague Channel, VA in 1976 but may have been established there one or two years earlier. In 1995 it washed up on beach on Poquoson Neck, VA on the western side of the lower Bay and was found at Cape Henry, VA in 1999. But so far hasn’t been reported on the Eastern Shore. It is now common in the Atlantic coastal bays and in Hog Island Bay, VA near the entrance of Chesapeake Bay. This is a marine seaweed and is restricted it to the mouth of the Bay due to salinity requirements. So far, no impacts have been reported but that could change if densities increased in bays along the Atlantic shore. Complete Record


Diatom Coscinodiscus wailesii


The diatom Coscinodiscus wailesii likely arrived in Atlantic water in ballast tanks.




Coscinodiscus wailesii is a diatom, a type of algae, which is native throughout the Pacific Ocean. The earliest records of this species in the Atlantic Ocean are for Chesapeake Bay in 1961. It was likely transported in ballast water through the Panama Canal, since this species has been seen in ballast water samples. Since then, it has been found in the lower Chesapeake Bay and along the continental shelf between Cape Charles VA and Cape May NJ. Within Chesapeake Bay this species doesn’t appear to be abundant enough to be problematic but, in the adjacent Atlantic waters between Cape Charles VA and Cape Henlopen DE, blooms of this species were reported in April 1978 that caused problems with commercial fishing nets and crab pots. The algae blooms coated fishing nets with slime making them difficult the handle. Another possible impact of the blooms is the depletion of oxygen and nutrients as a result of high densities, as was seen in the Seto Inland Sea, Japan in the early 1990s. Complete Record


Blue-green alga Cylindrospermopsis raciborskii


Blue-green alga Cylindrospermopsis raciborskii produces a deadly toxin.


Cylindrospermopsis raciborskii is a long thin alga with a very long name. This blue-green alga produces a toxin, cylindrospermopsin, which can kill fish and cattle, and produce skin reactions, liver damage, and death in humans. The alga has been found in the freshwater and brackish areas of Chesapeake Bay, but the toxin hasn’t been detected. If it were found it would likely result in the closure of some freshwater Chesapeake Bay tributaries to recreational uses during algal blooms, similar to the closures resulting from the blooms of native algal species that produce cyanobacteria. This introduced alga was first discovered in Indonesia in 1913 but has a very wide distribution in tropical areas around the world. It was first seen in the US in a lake in Kansas in 1955 and has since been found in many lakes in the Midwest and Southeast. It was first seen in tidal fresh waters of Chesapeake Bay in 2000. There are many vectors for transport including ballast water, ornamental aquatic plants, trailered boats, fishing gear, and dispersal of spores by migratory birds. Complete Record 


The red alga Gracilaria vermiculophylla

The red alga Gracilaria vermiculophylla is cultivated for agar in Asia.

Gracilaria vermiculophylla is a red alga native to northwest Pacific, including the coasts of Japan, Korea, China, and Vietnam, that is widely cultured as a source of agar. Agar is a gelatinous substance derived from the cell walls of red algae used as a laxative, a vegetarian gelatin substitute, a thickener for soups, jellies, ice cream and other desserts, and as a clarifying agent in brewing. It has also been used as a culture medium for microbiological work. G. vermiculophylla was first seen in 1998 from Hog Island Bay on the Atlantic Coast of Virginia. Since then it was been reported at in Chesapeake Bay in the York River and several other locations, but the extent of its distribution and abundance is still being studied. There are several means for its introduction including Pacific oyster imports, ballast water or hull fouling. Complete Record


Diatom Odontella sinensis

Diatom Odontella sinensis arrived to the Chesapeake in ballast water.

Diatoms look like jewels under the microscope but are a type of algae, and one of the most common types of phytoplankton (microscopic floating aquatic plants and algae). Diatoms have cell walls made of silica (silicon dioxide as in sand or quartz), which makes them hard and shimmery, but they also contain chloroplasts for photosynthesis like plants. The species Odontella sinensis is from Asia (China, India, etc.). It was discovered near the mouth Chesapeake Bay during a survey in 1961, and along the Atlantic Coast between Cape Henry VA and Cape May NJ in surveys conducted between 1971 and 1981. Because these diatoms are phytoplankton, these were likely transported in ballast water. Currently, they are a small part of the Bay’s phytoplankton community and no problems have been associated with them. Complete Record


Brown alga Striaria attenuata


Brown alga Striaria attenuate spread by hull fouling and natural dispersal.




The brown alga Striaria attenuata is native to the European coast from northern Spain to Norway, including the western Mediterranean. It was discovered in New York in the 1800s (1848-1881) and in Massachusetts in the 1930s. By 1937 it was known to occur from Staten Island to southern Massachusetts. It is likely that its spread along the coast occurred prior to the 1930s because this small and threadlike species is easy to miss. Algae often grow on the bottom of boats and hull fouling was likely responsible for its spread, as well as ballast water discharge and natural dispersal from the introduction site. By 1968 it had made its way to Burton's Bay VA and later to Chincoteague Inlet, Ocean City, MD, and on Smith Island, Northampton County, VA just outside the mouth of Chesapeake Bay. By the mid 1980s it was reported from Newfoundland south to North Carolina. So far there have been no economic or ecological impacts reported for this species and it remains rare in much of its introduced range. Complete Record 


Diatom Thalassiosira punctigera


Thalassiosira punctigera is a blue diatom from the Pacific. 



Thalassiosira punctigera is a beautiful blue diatom that is widely distributed through the Pacific Ocean (East and West, North and South). This diatom was first described in 1886 in the Northwest Pacific. Though we can’t say for sure where in the Pacific region this diatom may have originated, we consider it native to the Pacific Ocean. It has been introduced to several locations outside the Pacific. It was collected off Brazil and Argentina in between 1949-1981 and in the eastern Caribbean in 1955-56. It was first collected in the English channel in 1978 and is now abundant in estuarine waters along the North Sea. It was seen in Narragansett Bay in 1970 in the Gulf of Maine in the 1990s. Collections in the Chesapeake Bay were taken in the York River in the late 1980s. Ballast water is the most likely means of introduction outside the Pacific but natural dispersal may be possible in some areas. Complete Record 


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