Effect of temperature on 'N' uptake of Chaetomorpha linum (Muller) and Padina tetrastomatica (Hauck)
Abstract
Macroalgal species (Chaetomorpha linum and Padina tetrastomatica) collected from the Kavaratti lagoon (lat. 10 deg. 33 min. 16 sec. N and long. 72 deg. 38 min. 34 sec E) were brought to the laboratory and cleaned with filtered seawater. 0.5 g of algal thallus was placed in the beakers with 50 ml of seawater to which ammonium, nitrate and urea were added separately at the concentrations of 2, 5 and 10 mu M in the form of NH4Cl, KNO3 and urea respectively. Measurements of uptake of N as a function of temperature were tested at 4 different temperatures (20, 25, 30 and 35 degrees C). The irradiance measured during the incubation period was 276 mu E m sup(-2) s sup(-1). The duration of each experiment was 1 h. The experiments were carried out in duplicates. At the end of the experiment the algae were retrieved, oven dried at 70 degrees C and weighed. Technicon II autoanalyser was used for ammonium, nitrate and urea measurement using methods described by Koroleff (1970), Wood et al. (1967) and Aminot and Keroule (1982) respectively. Uptake was calculated based on the depletion of added nutrient from the experimental medium. Under all the combinations of temperature and N species, the uptake rate of NH sub(4) sup(+) was greater than that of NO sub(-3) sup(-) and urea.
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