November 8, 2013
The National Science Foundation has awarded University of Maine researchers $574,617 to study the effects of ocean acidification on the marine ecosystem of the Aleutian Islands.
UMaine professor Bob Steneck and postdoctoral research associate Doug Rasher, both based at the Darling Marine Center in Walpole, Maine, will work with Jim Estes of the University of California, Santa Cruz to determine whether ocean acidification, ocean warming and food web changes are reshaping species’ interactions in nature and threatening Clathromorphum nereostratum, a slow-growing coralline alga in the subarctic North Pacific Ocean.
During C. nereostratum’s 2,000-year lifetime it accretes massive bioherms, or mound-like reef structures, that form the foundation of the archipelago benthos upon which kelp forests grow. Preliminary research suggests the calcium carbonate skeleton of the coralline alga is weakening due to increased ocean acidification. With the recent ecological extinction of sea otters, the number of sea urchins has increased and, in places, they have grazed the kelp forest, leaving behind barren ancient coralline reefs.
During past cycles of sea otter/urchin/kelp booms and busts when ocean acidity was steady, C. nereostratum fared better. Now in a weakened state, it’s falling prey to urchins, crumbling away through bioerosion.
The three-year study will include a 2104 summer-long research expedition to the western portion of the Aleutians, from Adak Island to Attu Island. Researchers will survey kelp forests and urchin barrens, measure ocean acidity and collect samples of the ancient coralline bioherms.
Subsequent laboratory-based research will include urchin feeding experiments at past and present levels of ocean temperature and acidity to confirm processes driving patterns observed in the field. Additional studies will focus on the bands of calcium carbonate (similar to tree rings) in the coralline samples.