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.

Significance: Unicellular organisms form endless variability of complex skeletons that serve as archives of Earth’s history and play a crucial role in global geochemical cycles. A longstanding question is how single cells control morphogenesis and mineralization of skeletal structures. Although already addressed by Sir D’Arcy W. Thompson, this problem is still unsolved. Shell emerges from a controlled cascade of interactions at different levels of cellular organization. To gain insight into its morphogenesis, we apply live fluorescent imaging to observe cytoskeleton structures during shell formation in foraminifera. Our live experiments on calcifying foraminiferal chambers show that dynamic F-actin structures are involved in shaping and controlling mineralization.

Global change causes widespread decline of coral reefs. In order to counter the anticipated disappearance of coral reefs by the end of this century, many initiatives are emerging, including creation of marine protected areas (MPAs), reef restoration projects, and assisted evolution initiatives. Such efforts, although critically important, are locally constrained. We propose to build a “Noah's Ark” biological repository for corals that taps into the network of the world’s public aquaria and coral reef scientists. Public aquaria will serve not only as a reservoir for the purpose of conservation, restoration, and research of reef-building corals but also as a laboratory for the implementation of operations for the selection of stress-resilient and resistant genotypes. The proposed project will provide a global dimension to coral reef education and protection as a result of the involvement of a network of public and private aquaria.