Phosphorus fractions in the surface sediments of three mangrove systems of southwest coast of India

Abstract

The phosphorus fractions in three tropical mangrove systems of Cochin region were analysed by sequential extraction method. Iron-bound phosphorus was the major fraction in the first two stations, while station 3 was exclusively dominated by calcium-bound phosphorus. Compared to other stations, about tenfold increase in total phosphorus content was observed at station 3. This station is a congregation of communally breeding birds, and there is accumulation of bird guano. Mineralogical analysis showed the presence of monetite, a thermodynamically metastable calcium phosphate mineral, in this unique system. The excreta and carcass of the birds in this sanctuary seems to be the reason for the formation of monetite, which is favoured by periodic fluctuations in redox potential. The high mass percentages of calcium and phosphorus by XRF and SEM-EDS analysis confirm the existence of calcium phosphate mineral at station 3. First two stations did not show any noticeable difference in phosphorus fractions and inorganic fractions constituted to about 65% of total phosphorus. But at station 3, inorganic fractions were about 92%. Low C:P ratios and low organic phosphorus content indicated active mineralisation of phosphorus at station 3. Bioavailable fractions of phosphorus at stations 1 and 2 were about 75%, whereas 98% of the total phosphorus was bioavailable at station 3. Since the bulk of the total phosphorus is bioavailable, these mangrove sediments have the potential to act as source of phosphorus to the overlying waters.

Comparison of the Mangrove Soil With Different Levels of Disturbance in Tropical Agua Brava Lagoon, Mexican Pacific

“…It was found that P is retained more in the HD mangrove forest soil with a higher concentration of Ca in this site; as the P when combined with Ca is the main mechanism of P retention (Joseph et al, 2011). The content of potential bioavailable P was only 10-20% of the total P in the soil which has also been found for the mangrove soil of the Hun River and Taizi River (Lin et al, 2009).…”

The role of periphyton in phosphorus retention in shallow lakes with different trophic status, China

“…Generally, organic-bound phosphorus accounts for 6-19% of the TP in coastal sediments (Joseph et al, 2011). In this study, OP was the smallest fraction of all forms of phosphorus, making up about 20% of TP.…”

Speciation of Phosphorus from Suspended Sediment Studied by Bulk and Micro-XANES

“…This is in general agreement with results from sequential chemical P fractionations which indicated more Ca-associated P within BB sediments and more Fe and/or redox associated P with TA sediments (Section 3.1; Figure 3). Previous studies have used synchrotron XRF coupled with operationally defined chemical P fractionation results to establish the dominant elements governing sediment composition [40][41][42][43][44]. The intensity was calibrated relative to the scattered X-ray (to an intensity of 10000 at 7000 eV), so that the comparison of elemental intensities is possible.…”