Isotopes and Human Signatures

It is striking that reefs close to villages in the Outer Islands are less “healthy” – have less coral cover, smaller fish and reduced biodiversity – than more remote reefs. In particular, some reefs are becoming dominated by a single “weedy” coral species. The community has asked the science team to help them understand the various factors driving these differences, which likely include fishing pressures, physical damage to the reef, and possibly nutrient-rich runoff from the villages.

We are beginning to use stable isotope analysis to help us understand how runoff from human activity might be impacting the reefs. A pilot study of carbon and nitrogen isotopes in sea cucumber samples has shown evidence of a greater “human signature” on reef sites close to villages than on remote reefs, and we are in the process of scaling up this work in collaboration with Branwen Willams at Claremont McKenna College and Kelton McMahon at University of Rhode Island.