『Abstract
The chemical composition and vertical distribution of phosphorus
(P) in poorly oxygenated sediments in a continuum extending from
the open Baltic Sea towards an organic-rich inner bay were characterized
by sequential extraction to examine the potential for release
of sediment P. The chemical composition of P was related to chemical
and physical characteristics of the sediments and the chemistry
of pore water and near-bottom water to better understand the behaviour
of P. Sediment P increased towards the inner bay, and the concentration
of organic matter appeared to dictate its composition: the dominance
of apatite-P turned to dominance of organic P (OP). Sediment P
burial and, thus, release from sediment P reserves varied depending
on the chemical composition of P. Dissolved species at the sediment-water
interface suggested fluctuating redox conditions that affect P
binding at short time scale. Redox-sensitive, iron (Fe)-bound
P was usually relatively low because of poor oxygen (O2)
conditions, which emphasized the role of OP in P release. The
results indicate that, over the long term, the abundant organic
P reserve may support a significant continuing P release from
hypoxic sediments in the severely eutrophied Gulf of Finland (GoF)
because capture of P into Fe oxyhydroxides at the sediment surface
is restricted. The average long-term minimum annual rate of P
release from poorly oxygenated sediments below about 60 m depth
in the GoF was approximated on the basis of the vertical distribution
of sedimentary P forms and estimates of sedimentation rate.
Keywords: Baltic Sea; Fractionation; Organic matter; Phosphorus;
Sediment』
Introduction
Materials and methods
Research area and sediment types at the sampling sites
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 at the sediment-water interface
Burial and potential for release of sediment P along the west-to-east
transect
Conclusions
Acknowledgments
References