MEPS 182:305-310 (1999)  -  doi:10.3354/meps182305

Short-term nutrient pulses as tools to assess responses of coral reef macroalgae to enhanced nutrient availability

Britta Schaffelke*

Australian Institute of Marine Science, PMB 3, Townsville, MC 4810, Australia
Cooperative Research Centre: Reef Research, James Cook University, Townsville 4811, Australia

ABSTRACT: Inshore coral reefs of the Great Barrier Reef, Australia, are subjected to episodic nutrient inputs, mainly by rain and riverine run-off during the summer wet season. Increased nutrient availability, potentially caused by human activity, is assumed to enhance the production of primary producers. To simulate increased nutrient inputs, 6 species of coral reef macroalgae were treated with short-term (24 h) nutrient pulses of 10 µM ammonium and/or 1 µM phosphate. Sargassum baccularia, an inshore perennial algae, had a ~50% higher net photosynthetic rate and ~40% higher tissue nutrients after nutrient addition. The net photosynthetic rates of the inshore, ephemeral species Chnoospora implexa, Hydroclathrus clathratus, and Padina tenuis increased by ~30 to 50% and the tissue nutrient levels by 10 to 20% after a single nutrient pulse. Two perennial species, Chlorodesmis fastigiata and Turbinaria ornata, which occur inshore as well as on reefs further offshore, did not respond to nutrient addition with higher production, however, accumulated 15 to 20% more tissue nutrients than untreated thalli. The different responses to nutrient pulses of macroalgal species with different life cycles and distributional ranges provide important information for the prediction of the response of whole inshore reef communities.

KEY WORDS: Nutrient pulse · Coral reef macroalgae · Photosynthesis · Tissue nutrients

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