Outer organic layer and internal repair mechanism protects pteropod Limacina helicina from ocean acidification

first_imgScarred shells of polar pteropod Limacina helicina collected from the Greenland Sea in June 2012 reveal a history of damage, most likely failed predation, in earlier life stages. Evidence of shell fracture and subsequent re-growth is commonly observed in specimens recovered from the sub-Arctic and further afield. However, at one site within sea-ice on the Greenland shelf, shells that had been subject to mechanical damage were also found to exhibit considerable dissolution. It was evident that shell dissolution was localised to areas where the organic, periostracal sheet that covers the outer shell had been damaged at some earlier stage during the animal’s life. Where the periostracum remained intact, the shell appeared pristine with no sign of dissolution. Specimens which appeared to be pristine following collection were incubated for four days. Scarring of shells that received periostracal damage during collection only became evident in specimens that were incubated in waters undersaturated with respect to aragonite, ΩAr≤1. While the waters from which the damaged specimens were collected at the Greenland Sea sea-ice margin were not Ω Ar ≤1, the water column did exhibit the lowest ΩAr values observed in the Greenland and Barents Seas, and was likely to have approached ΩAr≤1 during the winter months. We demonstrate that L. helicina shells are only susceptible to dissolution where both the periostracum has been breached and the aragonite beneath the breach is exposed to waters of ΩAr≤1. Exposure of multiple layers of aragonite in areas of deep dissolution indicate that, as with many molluscs, L. helicina is able to patch up dissolution damage to the shell by secreting additional aragonite internally and maintain their shell. We conclude that, unless breached, the periostracum provides an effective shield for pteropod shells against dissolution in waters ΩAr≤1, and when dissolution does occur the animal has an effective means of self-repair. We suggest that future studies of pteropod shell condition are undertaken on specimens from which the periostracum has not been removed in preparation.last_img read more

United Nations to inspect North Korean weapons ship

first_imgBy Dialogo July 19, 2013 NEW YORK CITY, U.S.A. – United Nations sanctions experts will go to Panama soon to investigate a North Korean ship that was intercepted carrying weapons, officials said on July 18. Numerous countries have said the discovery of the weapons on the Chong Chon Gang freighter probably is a breach of UN sanctions against North Korea. North Korean and Cuba officials said the shipment consists only of obsolete missiles and other weapons parts from the mid-20th century being sent to North Korea for repairs. The vessel set out from Cuba and was trying to enter the Panama Canal when it was stopped by a counter-narcotics patrol, which found the weapons concealed beneath several tons of sugar. North Korea faces several rounds of sanctions over its nuclear weapons program, which is monitored by a UN Security Council committee currently chaired by Luxembourg. “The United States commends the actions of Panama in bringing this swiftly to the committee,” Jeffrey Delaurentis, a deputy U.S. ambassador to the United Nations, told reporters. “Efforts are ongoing to determine the contents of the vessel.” [AFP (United States), 18/07/2013; La Prensa (Panama), 10/07/2013]last_img read more