Sedimentary phosphorus in the Persian Gulf and the Gulf of Oman: Geochemical fractionation, seasonal variations, potential bioavailability, and ecological risk

Abstract

Phosphorus is a vital macronutrient that regulates marine biogeochemical cycles and ecosystem production. This is the first thorough investigation of phosphorus geochemistry in surface sediments of the Persian Gulf (PG) and the Gulf of Oman (GO), quantifying its fractions, potential ecological risks and potential bioavailability. Five forms of phosphorus were quantified using a sequential extraction technique. TP ranged from 636.0 to 1341.3 μg/g and 599.6–1354.1 μg/g in the summer and winter, respectively. Calcium-bound phosphorus (Ca-P) and detrital phosphorus (De-P) were the dominant forms of TP in surface sediments, with following descending order to other forms: O-P > Fe-P > Ad-P. Inorganic phosphorus (P) comprised over 83 % of the TP in the study area's sediments, indicating a low contribution from organic phosphorus. A mean of 29.1 % and 25.3 % of TP was found to be bioavailable phosphorus during the summer and winter sampling periods, respectively. Phosphorus pollution index exceeded one at most stations in both seasons, indicating sediment phosphorus pollution. Effective management of phosphorus inputs and maintenance of phosphorus balance are recommended to prevent eutrophication and HABs in the PG and GO.