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According to the US Commission on Ocean Policy the number of non-native species in US oceans has increased during the past two centuries and the rate is not tapering, and the effects are costing the US economy about $137 billion a year. They are commonly introduced by ballast water and hull fouling.

It gets easier for invasive species to go from place to place because they tag along. This week on Cape Cod and in Boston Harbor, a form of red seaweed that has never been detected this far north. This leafy algae, probably from Japan, is known to take over and smother the habitat of native organisms, but it is too early to tell whether it is causing damage in New England. The red seaweed can replace other algae that snails and other invertebrates rely on for food during the winter.

Researchers say there are usually one or two new invasive species each time they have done the study. The most aggressive genus, like Didemnum, are a group of sea squirts that cover the sea floor like a mat replacing the organisms that fish and shellfish eat. These colonies are able to morph into various shapes such as long rope or beard-like colonies hanging from docks, ship hulls and lines to the mat type with appendages that cover and drape rough sea-beds of pebbles, rocks etc. Didemnum are colonies of creamy yellow thick sponge-like masses that cover sea floors, and even their own colonies with flexible, irregular, long, flat, leaf, frond cylindrical branches forming gelatinous blankets.

Drinking water plants are experiencing clogged intake pipes and native organisms have been replaced by the notorious invasion of the zebra mussels in fresh waters.

Unlike invasive plants, there are about 1,600 species of sea squirts commonly known as sea grapes because of their tough outer skin are invertebrates that attach to pilings, oyster shells and stones near the shore of the Chesapeake Bay. Surprisingly, Sea squirts are able to squirt a stream as far as two feet, when removed from the water. This common sea grape releases both eggs and sperm into the water and after several days sucking tadpole-like larvae attach themselves to objects and in several more days they develop gill slits, organism’s digestive, circulatory and reproductive organs including a nerve cord, brain, equilibrium and lens eye.

How scary is this? ... An adult sea squirt can reproduce itself from only a fragment of a tiny blood vessel in less than a week.

The USGS and NOAA are requesting help from fishermen. If they encounter the sea squirt in their catch or on their gear and can report the position, depth of the catch, habitat or sediment type, this would be very useful. If they have a digital photo of the sea squirt, please send it along with any information to pvalentine@usgs.gov.

sea_squirts.jpg.b647042fdf051c46f4ae2ccd

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