The German ice-breaking research vessel “Polarstern” (photo) travels thousands of miles between the Northern and Southern hemispheres in search of biological samples. In addition to the members of its crew and staff of scientists, this ship has some additional on-board passengers: namely, organisms that can adapt to extreme water temperatures and could potentially invade the new waters where this ice breaker takes them. By analyzing the DNA present in this vessel's ballast water, a team of scientists has obtained the first molecular evidence of the persistence of DNA belonging to a tiny sea snail that is capable of tolerating adverse conditions. The new work has been published in the November 2015 issue of the Journal of Molluscan Studies. The article is titled “Environmental DNA Evidence of Transfer of North Sea Molluscs Across Tropical Waters Through Ballast Water.” Maritime transport is considered one of the most important ways that native species are moved between marine regions. The trip can be especially successful if these species latch on to the vessel's anchors or chains, or even if they travel in the ship's ballast water tanks. Each year, between 2.2 and 12 billion tons of water are transported around the oceans of the world in these ballast water tanks which also serve as a means of transport for about 7,000 species per day. In a European report that analyzed 15 samples of ballast water, live specimens of more than one thousand species were discovered in ship tanks that arrived to European ports. These taxa, however, must face very harsh conditions upon arrival: darkness, temperature changes, salinity, murky waters, turbulence, and a lack of oxygen. Not all of the species will survive, and the ones that do become potential invasive species.
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