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Abstract:
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Phosphorus fractionation was employed
to find the bioavailability of phosphorus and its
seasonal variations in the Panangad region of
Cochin estuary, the largest estuarine system in
the southwest coast of India. Sequential extraction
of the surficial sediments using chelating agents
was taken as a tool for this. Phosphate in the
water column showed seasonal variations, with
high values during the monsoon months, suggesting
external runoff. Sediment texture was found to
be the main factor influencing the spatial distribution
of the geochemical parameters in the study
region. Similarly, total phosphorus also showed
granulometric dependence and it ranged between
319.54 and 2,938.83 μg/g. Calcium-bound fraction
was the main phosphorus pool in the estuary.
Significant spatial variations were observed for
all bioavailable fractions; iron-bound inorganic
phosphorus (5.04–474.24 μg/g), calcium-bound inorganic
phosphorus (11.16–826.09 μg/g), and acidsoluble
organic phosphorus (22.22–365.86 μg/g).
Among the non-bioavailable phosphorus, alkalisoluble
organic fraction was the major one (51.92–
1,002.45 μg/g). Residual organic phosphorus was
K. R. Renjith (B) · N. Chandramohanakumar · M. M. Joseph
Department of Chemical Oceanography, School
of Marine Sciences, Cochin University of Science
and Technology, Kochi 682016, Kerala, India
e-mail: renjithaqua@gmail.com
comparatively smaller fraction (3.25–14.64% of
total). The sandy and muddy stations showed
distinct fractional composition and the speciation
study could endorse the overall geochemical character.
There could be buffering of phosphorus,
suggested by the increase in the percentage
of bioavailable fractions during the lean premonsoon
period, counteracting the decreases in
the external loads. Principal component analysis
was employed to find the possible processes
influencing the speciation of phosphorus in the
study region |