Researchers in the CSM Marine Biology Department’s Physiology and Biochemistry Team have published a new technique to investigate why coral calcification is sensitive to environmental changes. The work, published in the Journal of Experimental Biology, uses a fluorescent dye to assess changes in the leakiness of coral tissues to compounds in the surrounding seawater. These changes in ‘tissue permeability’ could be particularly important to coral health under conditions of altered seawater chemistry, such as ocean acidification.
Ions and molecules in seawater are transported to the coral’s site of calcification either actively by cellular mechanisms or, in certain cases, passively via a pathway in between the cells. This latter pathway, termed the paracellular pathway, has received little investigation in corals due to the technical hurdles involved in analysing it. Working with living corals in flowing seawater mounted on a state-of-the-art confocal microscope, the Physiology and Biochemistry Team used the dye calcein to track rates of exchange between the site of calcification and the surrounding seawater. The research revealed that the paracellular pathway of corals exposed to simulated ocean acidification became more “leaky”, potentially increasing coral vulnerability to this environmental stressor. By contrast, the paracellular pathway of corals exposed to temperature variation became more restricted or showed little change.
Importantly, the research paves the way for further work by the team on how easily different compounds pass from seawater to the site of calcification under the coral tissues. This area of research has fascinated coral biologists and paleogeochemists for decades, who want to know how well coral skeleton composition can act as a long-term indicator for seawater environmental conditions.