Cold-water corals in Chilean Patagonia
Calcifying cnidarians or hard corals are by far the most important structure-building marine organisms on earth. They create entire ecosystems and provide habitat and substrate for thousands of species throughout all taxa. Today we know that more than half of the coral reefs and structures are located in deep and cold waters. While most of these cold-water coral reefs are located in depths where research is complicated, at a few places in the world deep-water emergence brings cold-water coral communities close to the surface.
The channels and fjords of Chilean Patagonia are one of these places. Here hard corals that were hitherto known from the continental slope down to 2500 m can be found on hard substrata as shallow as 7 m and form an important part of the hard bottom biocenoses.
The fjords of the Northern Patagonian Zone are characterized by the presence of three scleractinian corals, Tethocyathus endesa, Caryophyllia huinayensis and the pseudo-colonial bank-building cosmopolitan coral Desmophyllum dianthus (see Figs. 1 to 4).
Figs. 1 to 4: Characteristic coral bank in the Comau Fjord and close-up images of Desmophyllum dianthus, Caryophyllia huinayensis and Tethocyathus endesa (clock-wise).
In some channels of the Central Patagonian Zone, the hydrocoral Errina antarctica can reach densities that have reef-like characteristics (see Fig. 5). These coral-made habitats are unique in the world and of outstanding importance for the regional biodiversity.
In May 2012 during our regular diver-based monitoring of Comau Fjord (where the Huinay Scientific Field Station is located) we discovered that all specimens of Desmophyllum dianthus had died at one of the long term study sites (see Fig. 6). The area of the mortality has a minimum horizontal extension of 8.4 km.
Fig. 5: Colonies of E. antarctica in the Copihue Channel.
Fig. 6: Healthy coral bank of Desmophyllum dianthus (A) and dead individuals in the Comau Fjord (B-D). Arrows indicate living species of Caryophyllia huinayensis between dead Desmophyllum dianthus individuals.
During a diver-based expedition to the Central Patagonian Zone in 2006 we documented an extraordinary density of Errina antarctica in a narrow channel in the Madre de Dios archipelago with reef-like structures and an exceptionally diverse associated benthic fauna. An expedition in 2013 revealed that the described coral population had been wiped out completely (see Figs. 7 – 8).
Figs. 7 and 8: Coral bank of Errina antarctica in 2006 and discovered field of coral rubble in the Copihue Channel in 2013.