I have so far been unable to identify this species of mollusc, photographed in early June near the research site. There are not many sea slugs that have an external shell. They were about 2 cms long and I saw a number of them. Anyone with any ideas as to the species?
The SILMAR Project marked its first year recently. EcoDive volunteers enjoyed a visit to the Marine Center where we discussed our progress and new developments, and then celebrated with a special cake!
"The physics and chemistry of adding an acid to the ocean are so well understood, so inexorable, that there cannot be an iota of doubt—gigatons of acid are lowering the pH of the world ocean, humans are totally responsible, and the more carbon dioxide we emit, the worse it's going to get," writes Richard A. Kerr in a recent issue of the journal Science.
Kerr points out that as the ocean has absorbed increasing amounts of carbon dioxide, its surface waters have acidified, so that ocean pH is lower now than it has been for 20 million years.
In a companion piece, Scott Doney of the Woods Hole Oceanographic Institution writes that the rate of change in ocean pH is "unprecedented, a factor of 30 to 100 times faster than temporal changes in the recent geological past, and the perturbations will last many centuries to millennia." Ocean acidification will likely reduce shell and skeleton growth in many marine species including corals and molluscs; some studies suggest that should levels of atmospheric CO2 pass a threshold of about 550 parts per million (ppm), coral reefs would begin to erode rather than grow because of acidification and surface ocean warming. Prior to the Industrial Revolution, atmospheric CO2 levels were approximately 285 ppm; they are presently close to 390 ppm.
However, continues Doney, some marine species may benefit from higher CO2 levels. For example, in laboratory experiments some species of phytoplankton, seagrasses and seaweeds exhibited higher levels of photosynthesis in water with elevated CO2. "A deeper understanding of human impacts on ocean biogeochemistry is essential if the scientific community is to provide appropriate and timely information to the public and decision makers on pressing environmental questions," he concludes.
Source: Doney, S.C. 2010. The growing human footprint on coastal and open-ocean biogeochemistry. Science 328: 1512-17; Kerr, R.A. 2010. Ocean acidification unprecedented, unsettling. Science 328: 1500-01
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