Tiny organisms in oceans can save islands from rising sea levels: study
conditions. Based on climate models, the researchers then forecast the future range of these calcareous shell protozoa.
“Amphistegina are among those profiting from the rising temperatures as a result of climate change,” summarizes Prof. Langer. According to the models, the calcareous protozoa will spread 180 km (or 1.6 degrees of latitude) closer to the poles through the warming oceans by 2050. By 2100, average ocean temperatures will increase by about 2.5 degrees Celsius according to conservative estimates. Accordingly, Amphisteginid foraminifera will progress another almost 300 kilometers — about 2.5 degrees of latitude — closer to the poles.
Ocean acidification — survival of the fittest
“Our models are forecasting rates of spread of up to eight kilometers per year,” says doctoral student Anna Weinmann from the Steinmann-Institut at the University of Bonn. Corals can spread into new territories at similarly high rates. They do, however, have problems with the acidification of the oceans that accompanies the increasing carbon dioxide rate in the atmosphere. The skeletons of corals consist of aragonite and are thus much more sensitive to acids than the fora-minifera’s calcite shell. “Amphisteginids and other foraminifera are increasingly taking over calcium carbonate production from corals, thus occupying their ecological niche. This is a role reversal in process,” reports Prof. Langer.
Calcium carbonate producers are stabilizing the coastlines and reefs
The rapid range extension and proliferation of amphisteginid and other tropical foraminifera will characterize tropical ocean floors of the future. There also is abundant evidence from the past to support this hypothesis; especially since these calcite protozoa have been inhabiting the oceans for about 600 million years already. “The fossil record shows that whenever during the history of Earth the carbon dioxide content of the atmosphere was considerably higher and the oceans were clearly warmer, foraminifera were among the most frequently occurring carbonate producers in tropical oceans,” says the micropaleontologist. The capability to rapidly expand their biogeographic territory under changing climate conditions, and their prolific production of calcium carbonate, will make them key ecosystem engineers for the stabilization of reefs, beaches and islands. Island nations are already pointing to the rising ocean levels and increasing damage to their coasts today. Prof. Langer, “Amphisteginids and other foraminifera will rapidly spread in the decades to come and will contribute substantially to future tropical reef island resilience.”
— Read more in Martin R. Langer et al., “Climate-Driven Range Extension of Amphistegina (Protista, Foraminiferida): Models of Current and Predicted Future Ranges,” PLOS ONE 8, no. 2 (6 February 2013) (DOI: 10.1371/journal.pone.0054443)
