
TY  - JOUR
A1  - O'Donohue, M. J. 
A1  - Glibert, P. M. 
A1  - Dennison, W. C. 
T1  - Utilization of nitrogen and carbon by phytoplankton in Moreton Bay, Australia
JF  - Marine and Freshwater Research
JO  - Mar. Freshwater Res.
Y1  - 2000
VL  - 51
IS  - 7
SP  - 703
EP  - 712
KW  - 
UR  - https://doi.org/10.1071/MF99096 
N2  - Water samples were collected within river mouths, at river plume sites and at well flushed ocean-influenced sites within Moreton Bay, a shallow subtropical embayment in south-eastern Queensland. Rates of inorganic nitrogen (NH+4 and NO-3) and carbon uptake were determined across temporal and spatial scales by use of 15N and 14C incorporation. Phytoplankton productivity, measured as CO2 uptake, was highest at the river mouths. Rates of NH+4 uptake exceeded rates of NO-3 uptake at all sites at all times. Relative preference indices demonstrated a consistent preference by phytoplankton for NH+4 uptake, and NH+4 uptake rates were higher at ocean-influenced sites than at river-mouth sites. Inorganic nutrient and chlorophyll a concentrations were highest at river mouths; however, the greatest NH+4 uptake occurred at the ocean-influenced sites, reflecting a greater dependence on &#8216;recycled&#8217; N than on &#8216;new&#8217; N. Biomass-independent NH+4 uptake increased with increasing water temperature; however, NO-3 uptake increased with decreasing water temperature, reflecting the lower temperature optimum for nitrate reductase. The range of NH+4 and NO-3 uptake rates was greater than ranges reported for other coastal waters, reflecting the strong temporal and spatial gradients within Moreton Bay. This trend of strong gradients in C and N dynamics from oligotrophic to river-influenced waters with seasonal flows is likely to exist in many tropical and subtropical coastal waters of Australia. 
ER  -

