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August 2014
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The Decline of Seagrass Meadows

Zostera! Eelgrass, Zostera marina, is a flowering, marine vascular plant that remains submerged all the time. This is quite a feat for vascular flowering plants, and only a few dozen species world wide are capable of growing completely submerged in a marine environment. Eelgrass creates and extremely important habitat, its upright structures and complex root system create a 3-D living space for many different types of animals. It is (or was) the dominant habitat forming SAV (submerged aquatic vegetation) throughout much of the coastal waters in the northeastern United States. Unfortunately, for various reasons, eelgrass meadows have seen drastic declines, and in many locations eelgrass only exists in a mosaic of small patches. This is extremely bad news as many of the important, and formerly important, commercial and recreational fisheries of the northeast US are dependent on Zostera at some part of their life cycle as a nursery and foraging ground. Some of the species are finfish like tautog, bluefish, fluke, winter flounder, porgies, while others are shellfish such as blue mussels, hard clams, oysters, bay scallops, and blue crabs. Many of the aforementioned species support or once supported vibrant fisheries. Many of those fisheries have collapsed, also for various reasons. However, is it possible there is a link between the crash of the fisheries, the decline of Zostera and the failure for recovery on both ends?

Bay Scallop on Eelgrass

Argopecten on Zostera! Bay Scallops, Argopecten irradians , have developed a very close relationship with eelgrass, Zostera marina. As larvae, they are passively transported, and tend to settle in eelgrass meadows when the current is dampened by the 3D structure of the seagrass. This same 3D structure provides post-set juvenile scallops a spatial refuge from predation. Even as larger juveniles and adults, scallops are capable of, and have been shown to, actively select eelgrass habitats.

Other species also use eelgrass

grass shrimp A number of other species utilize eelgrass as a habitat. Included are grass shrimp, like the Palaemonetes pugio, other decapods such as blue crabs, bivalves such as hard clams, gastropods (snails), and numerous fish species, including winter flounder, tautog and cod.

Shark Skin Technology

Recently, CBS covered a story of researchers investigating the pattern on shark skin, and how it is able to resist fouling organisms that are common on other long lived, large marine vertebrates such as whales and turtles.  This has major implications for the boating industry, and come companies have already begun to capitalize on the unique structure of shark skin to use as coatings for boats.  This isn’t necessarily news, as shark skin coating has been investigated as an anti-fouling mechanism for the NAVY for some time.  The idea behind that research is that a) fouling organisms settle on ship hulls and grow, increasing drag forces of the hull in the water, b) this increased drag reduces the ships efficiency and adds considerable cost to powering the vessel, and c) the pre-existing anti-fouling methods are either cost and time prohibitive (hauling the ship out on dry dock) or extremely harmful to the environment (such as using copper or tin based bottom paints).  The adverse affects of the bottom paints used were extremely harmful to the environment, leading to accumulation in the sediments of ports and bioaccumulation through the food chain.  The adverse affects led to the ban of tributyl-tin , TBT, bottom paint in the US and many countries abroad.  Additionally, some states are beginning to ban copper based paints as well.

In comes the shark skin, whose scales and denticles (tiny “skin teeth” ) are arranged in a diamond shaped pattern. The pattern of sharks skin is already effective at reducing drag forces.  So by merely mimicking the pattern, drag should be reduced along a ships hull.    Add to that the lack of spores being able to settle onto this skin pattern, and you have a bottom coating that is much more efficient for boats and more safe for the environment.

But now, researchers are interesting in a different kind of biofouling – bacteria and the medical industry.  Some research, according to the CBS article, indicates that Sharklet patterned plastic had significantly reduced numbers of bacteria on it when compared against a smooth plastic sheet.  This has major implications for the health industry, as some bacteria are difficult to kill, and many places like hospitals and doctor’s offices, as well as schools and public offices, are bacterial breeding grounds (although I guess technically anywhere is a bacterial breeding ground of some sort).  This material may be important for use combating  infections, by coating commonly touched places with the shark skin patterned material.

Interesting stuff.

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