Time course nutrient uptake study of some intertidal rocky shore macroalgae and the limiting effect due to synergistic interaction

Abstract

The time course nutrient uptake study of some intertidal rocky shore macroalgae showed a marked variation in the uptake of nutrients. In the present study, <em>Caulerpa sertularioides, Padina tetrastomatica, Sargassum cinctum, </em>and<em>Gracilaria corticata </em>which are slow growingassimilated ammonium, whereas the fast growing <em>Chaetomorpha antennina, Ulva flexuosa, </em>and <em>Ulva lactuca</em> assimilated nitrate. Nitrate in the medium was assimilated quickly by these three species. It was below the detection level after five hours. The study showed that the characteristic of nutrient uptake varies between different macroalgae. The slow growing perennial macroalgae preferred ammonium and fast growing annuals preferred nitrate.The preference of different form of nitrogen is inferred to be mainly due to low energetic cost and opportunistic uptake. The combination of nutrient-N and phosphate in the medium showed a synergistic interactive effect in some of the algae wherein the uptake of nutrient was slowed comparatively. This synergistic interactive effect was significant (<em>P </em>< 0.05) and these were observed in <em>Caulerpa sertularioides</em>, <em>Chaetomorpha antennina,</em>and <em>Ulva lactuca</em>.