Autökologie der Kaltwassersteinkoralle Caryophyllia huinayensis aus der patagonischen Fjordregion.

In northern Chilean Patagonia the scleractinian cold-water coral Caryophyllia huinayensis (Cairns, Häussermann & Försterra 2005) occurs in depths from 16 m up to 265 m. Knowledge about ecological parameters and its response to environmental changes in the habitat are still rare. With global ocean warming and ongoing ocean acidification cold-water corals face possible harmful impacts. To predict the influence of these changes on C. huinayensis and other scleractinian cold-water corals growth rates, abundance, respiration rates and feeding strategies have to be known. Furthermore complex relationships within cold-water reefs need to be revealed. In order to quantify abundance frame based individual census have been carried out in two Chilean fjords. The frame based census showed that C. huinayensis can be abundant with up to 2211 ± 180 individuals per square meter and thrives on a temperature range of 9,5 to 16 °C. In the Comaufjord C. huinayensis is widespread along a natural pH gradient. Due to this natural horizontal pH gradient down to values of pH 7,4 the Comaufjord allows growth experiments in pH conditions that are predicted for the next century. For estimations of growth rates and the influence of changing water parameters on coral growth a cross transplantation experiment has been carried out. Individuals from pH 7.94 ± 0.03 and pH 7.76 ± 0.09 have been cross transplanted, respectively. With a growth rate of 3,39 ± 2,52 μmol CaCO3×cm-2×d-1 transplanted individuals under low pH conditions showed comparable growth rates with the control group under high pH conditions. Maximum growth of 3,2 mm in height and 2,1 mm in calice diameter indicate the ability of C. huinayensis for growing under pH conditions that have been suspected to be harmful for coral skeletons. Individual respiration rates have shown that oxygen consumption under conditions of pH 7,4 was increased by 250 % compared with the control group of pH 8,0. An increased energy demand under low pH conditions could indicate a physiological adaptation of C. huinayensis enabling this species to up-regulate internal pH in tissues where biologically induced calcification takes place. In vitro-feeding-experiments revealed a zooplankton uptake of two prey organisms per hour. Carbon uptake showed that the ingested food could not provide enough energy for important metabolic activities. Dissolved organic substances or other particulate matter might have an importance for nutrition of C. huinayensis. Also zooplankton-uptake might increase with higher in situ prey densities. The present study shows that the scleractinian cold-water coral C. huinayensis has the ability to cope with future acidified seawater. Deep-water coral biocenosis might face harmful impacts of a shoaling aragonite saturation horizon. Despite the potential of calcification under decreased seawater pH the dissolution of seawater-exposed aragonite structures will limit the future distribution of scleractinian cold-water corals in ocean depths