Mass mortality of Errina antarctica in the Madre de Dios Archipelago
In some channels of the Central Patagonian Zone, the hydrocoral Errina antarctica can reach densities that have reef-like character. These coral-made habitats are unique in the world and of outstanding importance for the regional biodiversity.
Fig. 1: Errina antarctica in Canal Copihue, photo taken in 2006.
In 2006, a benthic inventory expedition to the Central Patagonian Province revealed anextraordinary dense population of Errina antarctica in the Copihue Channel close to Guarello Island in the Madre de Dios Archipelago (50ºS) (see Fig. 1). The hydrocorals covered the substratum in reef-like formations from 15 m down to the bottom of the channel at 40 m and along its entire length (Häussermann & Försterra, 2007a). During an expedition in 2013 we discovered that all elder specimens of E. antarctica had disappeared from this site. The troughs on the bottom of the channel were filled with coral rubble and we discovered only few smaller colonies. Artisanal fishermen divers from the area reported that in 2009 or 2010 they saw the corals already covered with dark filamentous overgrowth, which may refer to epibiontic hydrozoans and which could indicate that by this time the corals were already dead. The grade of erosion of the remaining corral rubble indicated that the corals had been dying at least 2 years earlier (see Fig. 2).
Fig. 2: Canal Copihue as seen in 2013 with E. antarctica rubble.
Fig. 3: Location of Canal Copihue in the Madre de Dios Archipelago.
South of the Golfo de Penas the hydrocoral Errina antarctica is an abundant habitat forming calcifying coral. This calcifying stylasterid species can form fan- or bush-like colonies of up to 40 cm diameter both on vertical as well on horizontal rock substratum. In the Copihue Channel, Madre de Dios Archipelago (see Fig. 3), E. antarctica reached densities that resemble reef-like structures, again, like D. dianthus does in the northern part, creating important habitats for a multitude of organisms.
After the scleractinians, Stylasterinae (Cnidaria, Hydrozoa) are the next large group of calcified cnidariansin species number. Of the approximately 250 species described worldwide, most live between 200 and 500 m depth. Nevertheless, comparably few publications deals with stylasterids. The stylasterid coral Errina spp. have been identified as key structural species in Antarctica, the South West Atlantic, New Zealand’s fjord’s, and in southern Chile’s Patagonian fjord’s.
The hydrocoral Errina antarctica is distributed around Southern South America and along the Scotia Arc, Antarctica. It is known to be fragile, slow growing and easily damaged by divers or fishing gear. No information is available on temperature or salinity tolerances.
A possible explanation for the Canal Copihue mass mortality could be a temperature anomaly. Although rising temperatures seem to have rather positive effects on scleractinian corals in colder waters, there are no data on the temperature sensibility of hydrocorals.
In March 2016, divers returned to Canal Copihue to install environmental monitoring equipment to try to learn more about E. antarctica and try to solve the mystery of why the individuals in Canal Copihue died. In the center of the canal, Errina rubble still lays in large quantities (see Fig. 4), however when we moved to the ends of the canal, where it widens and opens up into larger bodies of water, some smaller E. antarctica can be found (see Fig. 5 – 6)
Fig. 4: The center of Canal Copihue in 2016, still with abundant Errina antarctica rubble.
Fig. 5: Near the outer limits of Canal Cophihue, smaller Errina antarctica can be found. Photo taken in March 2016.
Fig. 6: A small recruit of Errina antarcica found in Canal Copihue in 2016. Knife is for scale.
and water temperature and various depths. We also installed recruitment plates to take a closer look at what might colonize a fresh surface in Canal Copihue. Finally, we installed what we call “fixed-frames” which is a 40cm by 40cm square marked out so that over time we can continue returning and photographing the exact same spot.
Divers will return to these sites in July 2016 to collect data and the site will remain an active and be monitored for at least another 2 years after.
Check out our expedition blogs for more details about these trips!