『Abstract
Solid phase P speciation has been determined in sediments from
a transect across the central section of the continental shelf
and slope of the Great Barrier Reef (GBR) lagoon. This region
is characterized by a gradient of riverine aluminosilicate clay
and silt nearshore, seawards of which biogenic carbonate sediment
predominates. Phosphorus speciation results show large variations
along this transect. Organic P and authigenic (apatite) P are
the major chemical forms of phosphorus in the central GBR continental
shelf sediments. Post-depositional reorganization of P was also
observed, converting organic P and iron bound P (Fe-P) to authigenic
(apatite) P. Phosphorus burial rate was estimated from measurements
of total P concentration and excess 210Pb sediment
mass accumulation rates. Burial efficiency varies significantly
over the shelf. Inshore areas showed significant P remobilization
from sediments to the water column (up to 〜50％). The mid and the
outer shelf showed little evidence for remobilization (except
for coral reef platform sediments), with more of the sediment
P being in the less reactive authigenic apatite phases. An appreciable
fraction of this non-labile authigenic apatite phase was identified
as fish bone. P sources and sinks over the central part of the
GBR shelf were quantified using a mass balance approach. This
showed that Coral Sea shelf edge upwelling events are essential
to satisfy the large P nutrient demand of the whole GBR lagoon.
P inputs due to upwelling events were greater than those contributed
by local rivers over an average year.』
1. Introduction
2. Materials and methods
2.1. Main characteristics of the study area
2.2. Sample collection
2.3. Solid-phase analysis
3. Results and discussion
3.1. Chemical characteristics of surface sediment of the
GBR continental shelf
3.2. Total phosphorus (TP) in surface sediment of the GBR continental
shelf
3.3. Speciation of P in surface sediment of the GBR continental
shelf
3.3.1. Exchangeable or loosely sorbed P (Pex)
3.3.2. Iron oxides/oxyhydroxide-bound P (PFe)
3.3.3. Authigenic P (Pauth)
3.3.4. Detrital apatite and other inorganic P (Pdet)
3.3.5. Organic P (Porg)
3.4. Phosphorus speciation in river suspended particulate matter
(SPM)
3.5. Sediment P speciation depth profiles
3.6. Post-depositional transformation of phosphorus
3.7. Phosphorus burial, diffusive fluxes and burial efficiency
3.8. P budget over the central GBR shelf
3.8.1. A simple box model for the GBR continental shelf
3.8.2. Estimation of annual P fluxes over the shelf
3.8.2.1. Riverine inputs
3.8.2.2. Atmospheric P inputs
3.8.2.3. Sedimentation and remobilization of P
3.8.2.4. Primary productivity (PP) and P nutrient demand (ND)
3.8.3. Mass balance over the shelf
3.8.4. Uncertainties and assumptions
4. Conclusions
Acknowledgments
Appendix A. Supplementary data
References