A.G. Grottoli R.P. Moyer 2011 <p><span>Tropical small mountainous rivers deliver a poorly quantified, but potentially significant, amount of carbon to the world’s oceans. However, few historical records of land–ocean carbon transfer exist for any region on Earth. Corals have the potential to provide such records, because they draw on dissolved inorganic carbon (DIC) for calcification. In temperate systems, the stable- (δ</span>¹³<span>C) and radiocarbon (Δ</span>¹⁴<span>C) isotopes of coastal DIC are influenced by the δ</span>¹³<span>C and Δ</span>¹⁴<span>C of the DIC transported from adjacent rivers. A similar pattern should exist in tropical coastal DIC and hence coral skeletons. Here, δ</span>¹³<span>C and Δ</span>¹⁴<span>C measurements were made in a 56-year-old&nbsp;</span><i>Montastraea faveolata</i><span>&nbsp;coral growing ~1&nbsp;km from the mouth of the Rio Fajardo in eastern Puerto Rico. Additionally, the δ</span>¹³<span>C and Δ</span>¹⁴<span>C values of the DIC of the Rio Fajardo and its adjacent coastal waters were measured during two wet and dry seasons. Three major findings were observed: (1) synchronous depletions of both δ</span>¹³<span>C and Δ</span>¹⁴<span>C in the coral skeleton are annually coherent with the timing of peak river discharge, (2) riverine DIC was always more depleted in δ</span>¹³<span>C and Δ</span>¹⁴<span>C than seawater DIC, and (3) the correlation of δ</span>¹³<span>C and Δ</span>¹⁴<span>C was the same in both coral skeleton and the DIC of the river and coastal waters. These results indicate that coral skeletal δ</span>¹³<span>C and Δ</span>¹⁴<span>C are recording the delivery of riverine DIC to the coastal ocean. Thus, coral records could be used to develop proxies of historical land–ocean carbon flux for many tropical regions. Such information could be invaluable for understanding the role of tropical land–ocean carbon flux in the context of land-use change and global climate change.</span></p> application/pdf 10.1007/s00338-011-0758-y en Springer Coral skeletal carbon isotopes (δ¹³C and Δ¹⁴C) record the delivery of terrestrial carbon to the coastal waters of Puerto Rico article