『Abstract
The chemical composition and vertical distribution of sediment
phosphorus (P) in shallow coastal sediments of the northeastern
Baltic Sea (BS) were characterized by sequential extraction. Different
P forms were related to chemical and physical properties of the
sediments and the chemistry of pore water and near-bottom water.
Sediment P composition varied among the sampling sites located
in the Archipelago Sea (AS) and along the northern coast of the
Gulf of Finland (GoF): the organic rich sites were high in organic
P (OP), while apatite-P dominated in the area affected by sediment
transportation. Although the near-bottom water was oxic, the sediments
released P. Release of P was most pronounced at the site with
high sediment OP and reduced conditions in the sediment-water
interface, indicating that P had its origins in organic sources
as well as in reducible iron (Fe) oxyhydroxides. The results suggest
that even though these coastal areas are shallow enough to lack
salinity stratification typical for the brackish BS, they are
vulnerable to seasonal oxygen (O2) depletion
and P release because of their patchy bottom topography, which
restricts mixing of water. Furthermore, coastal basins accumulate
organic matter (OM) and OP, degradation of which further diminishes
O2 and creates the potential for P release
from the sediment. In these conditions, an abundance of labile
OP may cause marked efflux of P from sediment reserves in the
long-term.
Keywords: Baltic Sea; Coastal sea; Fractionation; Organic matter;
Phosphorus; Sediment』
Introduction
Materials and methods
Research area and sediment types in the research area
Sampling
Analytical methods
Water column and pore water samples
Sediment
P fractionation
Statistical analyses
Results
Water column and pore water
Sediments
P fractions
Total elements in extracts
Statistical analyses
Discussion
Sediment properties
Vertical and spatial distribution of P
Immobile P
Reactive P
Dissolved species in the sediment-water interface
Burial and release of sediment P in the shallow coastal sediments
Conclusions
Acknowledgments
References