A new study investigating the ability of coral to record sea temperatures indicates that the Northwestern Atlantic has experienced unprecedented warming during the past 150 years.
The study, published in Proceedings of the National Academy of Sciences, analyzed the isotopic nitrogen content of the deep-sea gorgonian coral Primnoa resedaeformis which indicated increased nutrient absorption rates associated with warm-water environments.
Sediment cores have long been used as a record of temperature change, but their inherently low sedimentation rates limit their usefulness for detailed analysis of short intervals. Corals, on the other hand, have relatively large annual growth rates, making them ideal indicators of short-term changes in their environment.
Until now, the use of coral as a biogenic indicator has been limited by the inability of scientists to distinguish between nitrogen sources. This study is the first that has been able to effectively separate the different sources of nitrogen and get an accurate look at the ocean temperature levels recorded by coral for the past two millennia.
Corals are colonies of genetically identical polyps. Photo by Rhett A. Butler
Researchers collected living and fossil P. resedaeformis specimens via deep-sea trawling and robotics from the outer Northeast Channel, on the upper continental slope southwest of Nova Scotia, Canada. Using data obtained by isotopic analysis of the corals’ proteinaceous endoskeleton, they were able to construct an 1,800-year temperature history for the region.
Their results indicated that for most of the past 1,800 years, the Northwestern Atlantic region experienced relatively stable temperatures. However, ocean temperatures started to increase 150 years ago, with most of the change occurring after 1970.
The study concludes that the temperature change was, and continues to be, most likely induced by human activity and highlights the need for further investigation using innovative biogenic techniques.