How are cold-water corals responding to the changing environmental conditions produced by climate change? When it comes to this question, to date, experiments have exclusively focused on mature cold-water corals. Experts from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) recently explored the effects on corals at various younger developmental stages. What they found: Young and mature animals respond very differently to negative environmental influences. This aspect, they argue, urgently needs to be reflected in future research, forecasts and protective measures. The study was just released in the journal Science of the Total Environment.
Unlike their tropical cousins, cold-water corals live in cool waters, primarily with temperatures in the single digits Celsius. Here – for example, in the depths of Norwegian and Chilean fjords – they play an important part in the marine ecosystem, offering many fish species a place to hide and breed. AWI researchers recently spent several months investigating how three different life stages of the cold-water coral Caryphyllia huinayensis are responding to climate-change-induced environmental influences. In this regard, ocean acidification, warming waters, and reduced food availability were taken into account. The six-month-long experiment in a controlled aquarium setting allowed the experts to test the effects of various combinations of negative influences. In contrast, past studies have chiefly focused on mature cold-water corals and the influence of respective individual environmental parameters.
“We found that the different life stages react differently to changed environmental conditions,” explains AWI expert Kristina Beck, first author of the study. “Under simulated future environmental conditions, we observed higher mortality among the mature corals, and slowed growth among the young corals. Taken together, these two effects threaten the future of entire populations: Higher mortality means that fewer corals live long enough to reproduce. And due to slowed growth, the young corals only reproduce much later.”
“In addition, we found that cold-water corals are above all negatively impacted by reduced food availability, and that the living corals in our experiment were largely unaffected by ocean acidification,” says Beck. The duration for which the corals are subjected to negative environmental influences also affects their health. “For a few months, they can compensate for the changing influences; in the first three months of our experiment, we surmise that they drew on their available energy reserves,” says the AWI expert. “Accordingly, several points are important for future experiments. First, the duration needs to be long enough to yield robust findings. Second, they need to include all life stages and various combinations of environmental influences, so that reliable projections can be made for entire populations of cold-water corals.”
Original publication
Kristina K. Beck, Jan Nierste, Gertraud M. Schmidt-Grieb, Esther Lüdtke, Christoph Naab, Christoph Held, Gernot Nehrke, Grit Steinhoefel, Jürgen Laudien, Claudio Richter, Marlene Wall, “Ontogenetic differences in the response of cold-water coral Caryophyllia huinayensis to ocean acidification, warming and food availability”, Science of the Total Environment, 2023, https://doi.org/10.1016/j.scitotenv.2023.165565