Biogeochemical Zones Within a Macrotidal,Dry-Tropical Fluvial-Marine Transition Area: A Dry-Season Perspective |
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| Authors: | L C Radke P W Ford I T Webster I Atkinson G Douglas K Oubelkheir J Li B Robson B Brooke |
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| Institution: | (1) Marine and Coastal Environment Group, Geoscience Australia, Canberra, ACT, 2601, Australia;(2) CSIRO Land & Water, Canberra, ACT, 2601, Australia;(3) CSIRO Land & Water, Private Bag No. 5, Wembley, WA, 6913, Australia |
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| Abstract: | The Fitzroy River delivers large amounts of nutrients and fine sediments to Keppel Bay (contiguous with the Great Barrier
Reef Lagoon) during intermittent flow events. This study explores sources, forms and transformations of nutrients in Keppel
Bay, and develops a functional process zonation that integrates seabed geochemistry and water column nutrient characteristics
which are controlled by suspended sediment. The water column and seabed properties were investigated over two dry seasons,
with supplementary core incubations taken to measure carbon decomposition rates and nutrient fluxes. Keppel Bay can be divided
into three zones, the: zone of maximum resuspension (ZMR); coastal transitional zone (CTZ); and blue water zone (BWZ). Mineralisation
of predominantly terrestrial organic matter occurs in the ZMR where nutrient uptake by phytoplankton is light limited. The
CTZ and BWZ had higher light penetration and phytoplankton growth was likely limited by N and P, respectively. The identified
zones conform to the bathymetry and hydrodynamic characteristics of the bay, allowing for the development of an integrated
conceptual model accounting for the benthic and pelagic biogeochemical processes. Recognition of these different zones shows
that considerable variation in benthic and water column properties is possible within a small system with the bathymetric
and hydrodynamic characteristics of the fluidized bed reactor. |
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