Phosphorus metabolism in coral reef communities : exchange between the water column and bottom biotopes

• Published in: Hydrobiologia 1992-09, Vol.242 (2), p.105-114
• Main Author: SOROKIN, Y. I
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Marine; Sea water ecosystems; Synecology
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/BF00018066

Exchange of phosphate between components of the reef bottom and the water column were studied on reefs around Heron Island (Great Barrier Reef), both in aquaria and in in situ enclosures, using radioactive phosphorus ( super(32)P) as a tracer. Living corals, dead corals, coral rubble overgrown with periphyton, and soft sediments of coral sand were used in experiments. In all of these components of bottom reef biotopes, two opposite flows of inorganic phosphate were recorded and measured, i.e. the rate of PO sub(4)-P uptake from water (A sub(c)), and its release (A sub(e)). At ambient PO sub(4)-P concentrations in water of 0.1-0.3 mu mol/l, both flows varied in living corals, in coral rubble, and in coral sand. Under the latter concentration range (which is typical for coral reef areas), the reciprocal PO sub(4)-P flows almost balanced each other, so that net uptake (A sub(t)) was very low. Often it approached zero or was positive, showing that a net PO sub(4)-P release had taken place. The uptake flow (A sub(c)) in living coral was much more dependent on the PO sub(4)-P content in overlying water than was the release flow (A sub(c)). The data obtained are used to discuss problems of phosphorus balance and dynamics in coral reef ecosystems.