
%0 Journal Article
%A Campbell, Stuart J. 
%T Uptake of ammonium by four species of macroalgae in Port Phillip Bay, Victoria, Australia
%J Marine and Freshwater Research
%D 1999/07/21
%V 50
%N 6
%P 515-522
%K 
%R https://doi.org/10.1071/MF98058
%U https://www.publish.csiro.au/paper/MF98058 
%X The uptake rates of ammonium were determined for three species of native macroalgae and an exotic macroalga from Port Phillip Bay. All species exhibited rate-saturated mechanisms of uptake described by Michaelis&#8211;Menten uptake kinetics. At the highest concentration examined (28.6 &#181;mol NH4-N) Hincksia sordida had a higher rate of uptake (435 &#181;mol NH4 -N g dry wt&#8211;1 h&#8211;1) than Ulva sp. (108 &#181;mol NH4-N g dry wt&#8211;1 h&#8211;1) or Polysiphonia decipiens (53 &#181;mol NH4 -N g dry wt&#8211;1 h&#8211;1). Maximum surge uptake rate was highest for H. sordida and lowest for P. decipiens (802 and 57 &#181;mol NH4 -N g dry wt&#8211;1 h&#8211;1 respectively). The introduced phaeophyte Undaria pinnatifida had an intermediate capacity for ammonium uptake which was dependent on blade maturity. Differences in the ratio of maximum uptake rate to half-saturation rate between surge and assimilation uptake phases suggest a propensity for some species to take up ammonium at low concentrations. The relationships between nutrient uptake and growth among species would afford mature U. pinnatifida, H. sordida and Ulva sp. a competitive advantage for ammonium uptake in winter during high N availability, whereas P. decipiens would be able to exploit low N concentrations in spring and summer. 
