Phosphorus Speciation and Bioavailability in the Surface Sediments of Maryland Coastal Bays

Gurung, D.P.; Chen, N.; Waguespack, Y.; Ruby, D.E.; Ishaque, A.B., and Chigbu, P., 2020. Phosphorus speciation and bioavailability in the surface sediments of Maryland coastal bays. Journal of Coastal Research, 36(6), 1266–1277. Coconut Creek (Florida), ISSN 0749-0208.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.