Plankton and cold-water Coral ecology in Comau Fjord, Chile (PACOC)

Largest baleen whale mass mortality during strong El Niño event is likely related to harmful toxic algal bloom

The joint project combines the plankton ecological and reef ecological expertise of marine science institutions in Germany and in Chile to investigate the role of zooplankton in sustaining the cold-water coral (CWC) Desmophyllum dianthus in Patagonian fjords of Chile. Little is known about CWC in diver-inaccessible deep waters. Calcification and growth of these scleractinians is believed to depend on seawater chemistry, particularly the saturation state of the mineral composing the skeleton, aragonite, which is related to the pH and other chemical constituents. The rising CO2 levels in the atmosphere are predicted to change seawater chemistry and lower the aragonite saturation state, with so far unknown consequences to the deep biota. Because many CWC live at or near aragonite saturation, already slight changes in saturation state may have dire consequences for the calcification and survival of these slow-growing corals – and for the biota they sustain. Because many of the coral-associated organisms are of commercial importance, such as the Patagonian Redfish Sebastes oculatus, the fate of D. dianthus will also have far-reaching effects on the ecology and economy of the country. Comau Fjord near the Golfo de Ancud offers a unique window into the future, where the stratified fjord allows to time-travel from aragonite-supersaturated waters near the surface to undersaturated waters at depth. Recent research has produced the paradox that in spite of aragonite-undersaturated waters, the corals at depth appear to thrive unscathed, and in high densities – suggesting some so far unknown mechanism sustaining their growth. Because coral calcification is energeticaly costly, we hypothesize that a high supply of zooplankton food is required to provide the necessary metabolic energy to the coral to maintain a high alkaline internal pH for calcification against acidified fjord waters. Although an abundance of zooplankton and krill is supported by the occurrence of blue whales in the area, quantitative data are so far lacking.

 The project will consist of two parts addressed by the German and Chilean party, respectively: (1) an observational and experimental study on the ecology of the corals and their up-regulation of internal pH, and (2) the ecology of the plankton in Comau Fjord, its distribution in space and time, vertical migrations and seasonality. The two-pronged approach, involving state-of-the-art oceanographic and ecophysiological equipment and methods (e.g. a remotely operated vehicle, ROV, and microsensors) will allow us to resolve the CWC paradox in Chilean waters and to address (1) how the natural variations in aragonite saturation state affect coral calcification and growth, (2) what sources and supplies of energies fuel calcification in undersaturated waters, and (3) how CWC may be affected by the possible nitrification of fjord waters with the spread of salmon aquaculture, and finally (4) if and how D. dianthus is able to cope with global CO2 and temperature rise. Research involving PIs from both countries, postdoctoral, doctoral and undergraduate students, technicians and engineers will have a strong capacity building component and strengthen institutional collaboration. Results will be published in ISI journals, disseminated to the public and contribute to the coastal and resource management process and designation of MPAs.

Desmophyllum dianthus. Photo taken by Ignacia Acevedo-Romo.

Home to rare corals, a Chilean fjord declines in spite of protection

The Comau, Reñihue and Reloncaví fjords, located in southern Chile’s Los Lagos region, are one-of-a-kind natural laboratories that host diverse species of crustaceans, sea anemones, sea cucumbers, polychaetes and corals. These bodies of water are narrow inlets left by glacial erosion that feed the ecosystem of the Patagonian Sea. Read more…