Conservation genetics of the cold-water coral Lophelia pertusa (Scleractinia)

Abstract

The cold-water coral Lophelia pertusa is the most important reef-building coral species in the NE Atlantic Ocean. The reef framework creates a complex structural habitat that sustains high species diversity in the deep-sea. During the last decades, powered by improvements in deep-sea research equipment, it has become clear that threats imposed by anthropogenic activities have caused considerable destruction of these cold-water coral ecosystems.

To assist cold-water coral management and conservation, this thesis aim to improve the understanding of L. pertusa biology, focusing on genetic population structure, larval development and restoration.

First, we investigated the fine-scale genetic structure within and among reefs in the NE Skagerrak using microsatellite markers. Clonal reproduction was common resulting in an aggregated distribution of genotypes within reefs. There was a significant genetic differentiation among reef localities at spatial scales of tens of km (paper I). On the scale of the NE Atlantic genetic structure could be explained in terms of holocene range expansion (paper II). Finally, we compared the whole mitochondrial genomes of two geographically separated individuals (Norway and Italy, respectively) and found virtually no sequence differences (paper III). This result corroborates previous findings of low diversity in Anthozoa mitochondrial DNA, but is also in line with the hypothesis of long-range gene flow and a Mediterranean origin of L. pertusa populations on the Scandinavian continental margin.

The larval stage is the only dispersal phase of corals and therefore tightly associated with connectivity among reefs. Using laboratory crossings and larval rearing we show for the first time that L. pertusa produce pelagic larvae that can live in the watercolumn for several weeks (paper IV).

Bottom trawling has caused extensive destruction of cold-water coral habitats worldwide. In Sweden only one of six reefs is still alive, but the risk that this reef also will be lost is imminent. We tested the possibility to restore a damaged reef by using transplants of L. pertusa from a healthy reef (paper V). More than three years after the deployment with transplanted coral the survival of fragments was 76%, and the mean size of fragments increased with 39 %, demonstrating the potential for active restoration of cold-water coral habitats.