『Abstract
Present study examined phosphorus dynamics through delineation
of source as well as availability of phosphorus and its fractionation
within the intertidal sediments of Pichavaram mangrove ecosystem.
Twelve sediment samples and two cores were collected from the
mangrove forest along with estuarine area (Vellar-Coleroon) during
January 2005. Sediments were analyzed for total phosphorus and
its fractionation using operationally defined chemical sequential
extraction scheme (SEDEX). Dissolved phosphorus (in water) and
total phosphorus (in sediments) concentrations were high in the
Vellar region of Pichavaram mangrove area due to pollution load
from nearby villages and agricultural fields. However, the spatial
variation in dissolved phosphorus were insignificant (at significance
level = 0.05). The results for the phosphorous fractionation (post-tsunami)
were compared with earlier studies (pre-tsunami). It was observed
that all phosphorus fractions (except adsorbed-phosphorus) showed
a highly significant (at significance level = 0.05) increase in
concentration after the tsunami event. There was significant decrease
in the adsorbed phosphorus concentration as a result of tsunami.
The changes were more pronounced for organic phosphorus which
increased by almost twofold following the event. These variations
were attributed to change in salinity, increase in dissolved oxygen
as well as the retreat of tsunami water carrying the waste load.
The vertical distribution of phosphorus through core sediments
showed that mixing after tsunami had altered the different phosphorus
fraction and its availability. Overall, the study indicated that
the fluvial weathering along with litter degradation and anthropogenic
sources controlled the biogeochemistry of phosphorus in this mangrove
ecosystem. Observed changes in the concentrations are a result
of altered physico-chemical characteristics caused by tsunami.
Keywords: Tsunami; Phosphorus; Biogeochemistry; SEDEX-fractionation;
Pichavaram』
Introduction
Study area
Materials and methods
Sample collection and preservation
Analysis of phosphorus
Sequential extraction
Statistical analysis and data interpretation
Results
Discussion
Depth variation in P fractionation
Conclusion
Acknowledgments
References