The effect of different flow regimes on the growth and metabolic rates of the scleractinian coral Galaxea fascicularis |
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Authors: | M Schutter J Crocker A Paijmans M Janse R Osinga A J Verreth R H Wijffels |
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Institution: | (1) Aquaculture and Fisheries Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands;(2) Bioprocess Engineering, Wageningen University, P.O. Box 8129, 6700 eV Wageningen, The Netherlands;(3) Burgers Zoo, Antoon van Hooffplein 1, 6816 SH Arnhem, The Netherlands; |
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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. |
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