Sedimentary Phosphorus Deposits in a Southern Caribbean Gulf During the Last Millennium

Abstract

Phosphorus (P) is an essential nutrient for the biological productivity of terrestrial and aquatic ecosystems and enters coastal ecosystems mainly through fluvial input. The contribution of P can be natural and anthropogenic, transported as particulate and dissolved load. This study sought to evaluate the spatial and temporal distribution of sedimentary P deposits in the Gulf of Urabá during the last millennium. For this, three sediment cores between 2.0 and 2.7 m long were divided into 5 cm thick lithological units. The content for total P (TP) and inorganic P (IP) in these units was determined by spectrophotometry after calcination and analytical fractionation during solid-liquid extractions with HCl. Organic P (OP) was calculated as the difference between TP and IP. The TP varied between 0.28 and 10.59 mg P g-1, and was composed mainly of OP with proportions between 14.40 – 99.7% of the TP. The highest level of sedimentary P was found at the León River Mouth followed by the Prodelta and the Atrato Delta Front. The OP displayed a long-term trend from the Medieval Warm Period (MWP) towards the Current Warm Period (CWP). The downcore P content integrated the contribution of chemical weathering, erosion, detritus, and anthropic input, such as mining, crop fertilization and domestic wastewater.

Keywords: Total phosphorus, organic phosphorus, inorganic phosphorus, sediment, paleoclimate