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Marine Ecology Progress Series

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MEPS 490:1-10 (2013)  -  DOI:

Water-flow mediated oxygen dynamics within massive Porites-algal turf interactions

Anya L. Brown1,2,*, Robert C. Carpenter1

1California State University, 15111 Nordhoff Street, Northridge, California 91330, USA
2Present address: University of Florida, Gainesville, Florida 32611, USA

ABSTRACT: Negative interactions between corals and algae have been implicated in preventing coral reef recovery. A recent hypothesis is that algae indirectly cause coral tissue mortality by fueling microbial growth, which drives hypoxic conditions at the interface between corals and algae. However, previous studies have largely ignored how water flow influences oxygen concentrations at the interface between corals and algae. This study quantified the effect of water flow on oxygen concentrations above the zone of interaction between massive Porites spp. and algal turf during the day and at night. Coral-algal interactions were exposed to 3 flow speeds (0, 7.7, 14.5 cm s-1), and diffusive boundary layer (DBL) thicknesses were measured in the light and dark. DBL thickness (<500 to 2500 µm) decreased with increasing water flow, but remained thicker above algal turf and the zone of interaction (~1000 µm) than over corals (370 µm) in the dark. Oxygen extremes above the zone of interaction were most similar to concentrations above algal turf in low flow (34 to 43% oxygen saturation). The influence of microbes on oxygen conditions was estimated by adding antibiotic (50 µg ampicillin ml-1) to algal turf-massive Porites interactions. The results showed no indication of microbially mediated hypoxic conditions. These results suggest that water flow likely limits the effectiveness of hypoxia or hyperoxia-mediated coral-algal competition under natural reef conditions.

KEY WORDS: Water flow · Oxygen concentrations · Coral-algal interactions · Microbially mediated interactions

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Cite this article as: Brown AL, Carpenter RC (2013) Water-flow mediated oxygen dynamics within massive Porites-algal turf interactions. Mar Ecol Prog Ser 490:1-10.

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