US EPA

831329 

Journal Article 

Nitrogen uptake responses of Gracilaria vermiculophylla (Ohmi) Papenfuss under combined and single addition of nitrate and ammonium 

Abreu, MH; Pereira, R; Buschmann, AH; Sousa-Pinto, I; Yarish, C 

2011 

Yes 

Journal of Experimental Marine Biology and Ecology
ISSN: 0022-0981 

407 

2 

190-199 

English 

10.1016/j.jembe.2011.06.034 

WOS:000295707900008 

http://linkinghub.elsevier.com/retrieve/pii/S0022098111003066
Exit
 

The ammonium (NH(4)(+)) and nitrate (NO(3)(-)) uptake responses of tetrasporophyte cultures from a Portuguese population of Gracilaria vermiculophylla were studied. Thalli were incubated at 5 nitrogen (N) levels, including single (50 mu M of NH(4)(+) or NO(3)(-)) and combined addition of each of the N sources. For the combined additions, the experimental conditions attempted to simulate 2 environments with high N availability (450 mu M NO(3)(-) + 150 mu M NH(4)(+); 250 mu M NO(3)(-) + 50 mu M NH(4)(+)) and the mean N concentrations occurring at the estuarine environment of this population (30 mu M NO(3)(-) + 5 mu M NH(4)(+)). The uptake kinetics of NH(4)(+) and NO(3)(-) were determined during a 4 h time-course experiment with N deprived algae. The experiment was continued up to 48 h, with media exchanges every 4 h. The uptake rates and efficiency of the two N sources were calculated for each time interval. For the first 4 h, G. vermiculophylla exhibited non-saturated uptake for both N sources even for the highest concentrations used. The uptake rates and efficiency calculated for that period (V(0-4 h)), respectively, increased and decreased with increasing substrate concentration. NO(3)(-) uptake rates were superior, ranging from 1.06 +/- 0.1 to 9.65 +/- 1.2 mu M g(dw)(-1) h(-1), with efficiencies of 19% to 53%. NH(4)(+) uptake rates were lower (0.32 +/- 0.0 to 5.75 +/- 0.08 mu M g(dw)(-1) h(-1)) but G. vermiculophylla removed 63% of the initial 150 mu M and 100% at all other conditions. Uptake performance of both N sources decreased throughout the duration of the experiment and with N tissue accumulation. Both N sources were taken up during dark periods though with better results for NH(4)(+). Gracilaria vermiculophylla was unable to take up NO(3)(-) at the highest concentration but compensated with a constant 27% NH(4)(+) uptake through light and dark periods. N tissue accumulation was maximal at the highest N concentration (3.9 +/- 0.25% dw) and superior under NH(4)(+) (3.57 +/- 0.2% dw) vs NO3 (3.06 +/- 0.1% dw) enrichment. The successful proliferation of G. vermiculophylla in estuarine environments and its potential utilization as the biofilter component of Integrated Multi-Trophic Aquaculture (IMTA) are discussed. (C) 2011 Elsevier B.V. All rights reserved. 

Ammonium; Ecophysiology; Gracilaria vermiculophylla; Nitrate; Nitrogen; Seaweeds