Coralline red algae as high-resolution climate recorders

While we have achieved a good understanding of century-scale climate change in mid- and high-latitude terrestrial areas (mainly through the analysis of tree-ring records), such data are incomplete in many extratropical marine regions, due to a lack of appropriate climate archives. Halfar et al. have investigated the potential of long-lived marine algae as recorders of past climates. Coralline red algae, which live in many coastal regions worldwide, produce a skeleton made up of calcium carbonate. Individual calcified plants exhibit annual growth bands, very similar to tree rings, and can live continuously for several centuries in temperate and subarctic oceans.

By monitoring coralline red algae of the genus Clathromorphum for a one-year period in the gulf of Maine, United States, Halfar et al. were subsequently able to relate geochemical information contained in the calcified algal growth bands to locally measured ocean temperatures, thus highlighting the suitability of coralline red algae as extratropical climate archives. By applying the results of the monitoring experiment to a 30-year coralline-algal oxygen isotope record, they demonstrated that the algae archived past water temperatures.

In addition, the specimen contained a record of past variations of the Labrador ocean current and related climate oscillations in the northwestern Atlantic—a key region in Earth's oceans where poorly understood climate and oceanographic changes have recently had a dramatic impact on ecosystems and fishery yields.-Geological Society of America