Out of Their Depth? Isolated Deep Populations of the Cosmopolitan Coral Desmophyllum dianthus may be Highly Vulnerable to Environmental Change

• Published in: PLoS ONE
• Main Authors: Miller, KJ, Rowden, AA, Williams, A, Haussermann, V
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library Science 2011
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); Antarctic; New Zealand; Pacific; Southern Ocean; Antarc*
• Online Access: https://doi.org/10.1371/journal.pone.0019004; http://www.ncbi.nlm.nih.gov/pubmed/21611159; http://ecite.utas.edu.au/76061

Deep sea scleractinian corals will be particularly vulnerable to the effects of climate change, facing loss of up to 70% of theirhabitat as the Aragonite Saturation Horizon (below which corals are unable to form calcium carbonate skeletons) rises.Persistence of deep sea scleractinian corals will therefore rely on the ability of larvae to disperse to, and colonise, suitableshallow-water habitat. We used DNA sequence data of the internal transcribed spacer (ITS), the mitochondrial ribosomalsubunit (16S) and mitochondrial control region (MtC) to determine levels of gene flow both within and among populationsof the deep sea coral Desmophyllum dianthus in SE Australia, New Zealand and Chile to assess the ability of corals todisperse into different regions and habitats. We found significant genetic subdivision among the three widely separatedgeographic regions consistent with isolation and limited contemporary gene flow. Furthermore, corals from different depthstrata (shallow ,600 m, mid 10001500 m, deep .1500 m) even on the same or nearby seamounts were stronglydifferentiated, indicating limited vertical larval dispersal. Genetic differentiation with depth is consistent with thestratification of the Subantarctic Mode Water, Antarctic Intermediate Water, the Circumpolar Deep and North Pacific DeepWaters in the Southern Ocean, and we propose that coral larvae will be retained within, and rarely migrate among, thesewater masses. The apparent absence of vertical larval dispersal suggests deep populations of D. dianthus are unlikely tocolonise shallow water as the aragonite saturation horizon rises and deep waters become uninhabitable. Similarly,assumptions that deep populations will act as refuges for shallow populations that are impacted by activities such as fishingor mining are also unlikely to hold true. Clearly future environmental management strategies must consider both regionaland depth-related isolation of deep-sea coral populations.