ABSTRACT

Gurung, D.P.; Chen, N.; Waguespack, Y.; Ruby, D.E.; Ishaque, A.B., and Chigbu, P., . Phosphorus speciation and bioavailability in the surface sediments of Maryland coastal bays.

Phosphorus (P) is an essential nutrient for phytoplankton growth and biochemical processes. In shallow coastal lagoons, there is strong coupling between water column and sediments in terms of P dynamics. To better understand dynamics and bioavailability of P in Maryland coastal bays (MCBs), surface sediment samples were collected at 13 sites of MCBs in May, August, October, and December in 2013 to assess the major reservoirs using a six-step sequential P extraction procedure. The objectives of this study were (1) to determine the spatial/temporal variations of P species in MCB sediment and to assess the relationship of P species at various locations with material sources and sediment types, and (2) to assess the bioavailability of sedimentary P in the study area. The average percentages of fractions of P of four months (representing four seasons) in surface sediments were Det-P (33.5 ± 4.36%) > total organic P (27.2 ± 3.43%) > Fe-P (13.0 ± 1.36%) > Al-P (12.2 ± 1.25%) > authigenic P (11.1 ± 2.86%) > L.Adsorp-P (3.0 ± 0.38%). On average, bioavailable P in surface sediments accounted for 55.4% of total P and thus represented a significant proportion of the sedimentary P pools in MCBs. Total P (TP) in the surface sediment ranged from 309.8 to 1345.4 μg/g with an average of 874.5 ± 343.3 μg/g. There was a strong positive relationship between TP and sediment grain size (mean phi) such that sites with the finest sediments (clay-silt) closest to the mouths of tributaries had significantly higher TP than sites with coarser grains.

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