
TY  - JOUR
A1  - Horrocks, JL 
A1  - Stewart, GR 
A1  - Dennison, WC 
T1  - Tissue nutrient content of <I>Gracilaria</I> spp. (Rhodophyta) and water quality along an estuarine gradient
JF  - Marine and Freshwater Research
JO  - Mar. Freshwater Res.
Y1  - 1995
VL  - 46
IS  - 6
SP  - 975
EP  - 983
KW  - 
UR  - https://doi.org/10.1071/MF9950975 
N2  - Tissue nutrient content of Gracilaria spp. (Rhodophyta) was tested as a bioindicator of water column nutrient availability in the Logan River and southern Moreton Bay, south-eastem Queensland. Macroalgae were incubated for one to two weeks within flow-through incubation chambers suspended in the water column. Tissue nutrient content of Gracilaria spp, and water column nutrients were measured at five sites over a five-month period. Tissue nitrogen content (%N) was correlated with dissolved inorganic nitrogen (DIN) at a site 15 km upstream from the Logan River mouth (r&#178; = 0.81), at the Logan River mouth (r&#178; = 0.50), and at a Moreton Bay site 8 km from the Logan River mouth (r&#178; = 0.71). Time-course analyses of water column nutrients and plant tissue content showed more significant correlations with nitrogen (N) than with phosphorus (P). Plant tissue nitrogen-to-phosphorus (N:P) molar ratios ranged between 19 and 23 whereas water column N:P ratios were between 2 and 6, suggesting low nitrogen availability relative to plant requirements and possible N limitation.      In the laboratory, Gracilaria verrucosa was subjected to treatments of N, P or N + P nutrient additions. Deepening of the thallus colouration was observed after additions of N. Chlorophyll and phycoerythrin concentrations increased in treatments with N addition; however, owing to wide variability between phycoerythrin replicates, only chlorophyll increases were significant. The amino acid citrulline also increased with the addition of N and accounted for up to 16% of the total tissue N. Macroalgae may be more useful than traditional water quality sampling for integrating biologically available pulses of nutrients, especially for a limiting nutrient such as N in coastal marine ecosystems. 
ER  -

