Phosphorus Availability and Speciation in the Intertidal Sediments of Sundarbans Mangrove Ecosystem of India and Bangladesh

Abstract

AbstractThe intertidal sediments of Sundarbans mangrove ecosystem from the Indian and Bangladesh side were studied for the sedimentary phosphorus cycling and phosphorus bioavailability. A total of seven sediment cores were collected from the Sundarbans mangroves which were subjected to sequential extraction procedure to study the different sedimentary pools of phosphorus, namely, loosely sorbed P, Fe-bound P, authigenic P, detrital P and organic P. The total sedimentary P in the cores varied between 8.36 and 11.20 μmol/g for the Indian Sundarbans and from 8.80 to 11.40 μmol/g for the Bangladesh Sundarbans. The average percentage of respective P fractions in the three cores collected from Indian Sundarbans followed the order: authigenic P (39.96%) > detrital P (30.58%) > organic P (22.44%) > sorbed P (4.86%) > Fe-bound P (1.96%), and in the four cores from Bangladesh, it followed the sequence: detrital P (33.43%) > authigenic P ~ organic P (31.49%) > Fe-bound P (12.43%) > sorbed P (3.58%). Diagenetic redistribution of P was attributed to be the dominant factor responsible for the conversion of organic and Fe-bound P to authigenic P. A considerable fraction of the total sedimentary P was constituted by the bioavailable P which accounted for <33.70% and <41.07% in Indian and Bangladesh Sundarbans, respectively. The results are suggestive of the internal loading of P being an important but a limiting factor which governs the biological productivity in the Sundarbans mangrove ecosystem.KeywordsPhosphorusSequential extractionMangrovesBioavailabilityProductivity Sundarbans