The effect of different flow regimes on the growth and metabolic rates of the scleractinian coral Galaxea fascicularis

Abstract

To study the effect of water flow on coral growth, four series of ten coral nubbins of Galaxea fascicularis were exposed to four different flow regimes (0, 10, 20, and 25 cm s-1 , bidirectional flow) for 42 weeks. Buoyant weight, surface area, and polyp number were measured at regular intervals. Net photosynthesis and dark respiration were measured at the corresponding flow speeds, and daily amount of photosynthetic carbon left for coral growth was calculated. Finally, skeletal density and CN content, chlorophyll concentration and dry weight of coral tissue were determined for each coral. Specific growth rate (in day-1) decreased with time in each flow treatment. Absence of flow resulted in significantly lower growth rates. Average specific growth rate calculated over the entire experiment was not significantly different between 10 and 20 cm s-1 , while it was significantly higher at 25 cm s-1. From 10 to 25 cm s-1 , average net photosynthetic rate decreased and average dark respiration rate did not change significantly. Scope for growth based on phototrophic carbon decreased with increasing flow. Growth was not positively correlated with either photosynthesis or respiration, or scope for growth. It is suggested that higher flow rates reduce the chance of disturbance of coral growth by competing algae or cyanobacteria, allowing corals to grow more readily with the maximum specific growth rate possible under the given environmental conditions. Notably, other effects of increased flow, such as increased respiratory rates and increased (in)organic nutrient uptake, might have been equally responsible for the increased growth of the corals in 25 cm s-1 .

The CORALZOO project: a synopsis of four years of public aquarium science

“…Specific growth rates of this species were found to exhibit a decreasing trend in time (Schutter et al, 2010). Hence, small fragments will have the highest productivity.…”

Anemonefish oxygenate their anemone hosts at night

“…The flow-induced reduction or elimination of the diffusive boundary layer surrounding sedentary organisms notably enhances gas exchange (Patterson and Sebens, 1989;Patterson et al, 1991;Bruno and Edmunds, 1998;Sebens et al, 2003;Finelli et al, 2006;Schutter et al, 2010), nutrient uptake (Stambler et al, 1991;Atkinson and Bilger, 1992;Lesser et al, 1994;Thomas and Atkinson, 1997), prey capture (Helmuth and Sebens, 1993;Sebens, 1997;Sebens et al, 1998) and debris removal (Nugues and Roberts, 2003;Box and Mumby, 2007). Thus, anemonefish-enhanced water flow among sea anemone tentacles could provide several types of distinct benefits to the physiology and biology of the cnidarian host.…”

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“…current, is another factor known to affect multiple aspects of coral development [21,23,24]. However, the coverage patterns on mooring blocks in this study appear to be unrelated to the current velocity near the blocks.…”