Restoration of Desmophyllum pertusum. How polyp groth and survival is affected by substrate and nutrition, a 3D-model analysis.

Abstract

Desmophyllum pertusum is a cold-water coral found all over the world, including Sweden. It has a large impact on the ecology in deeper water with a similar amount of biodiversity as tropical coral reefs. During the recent decades almost all the reefs within Swedish waters have been destroyed, mostly due to bottom trawling. So far, the establishment of MPAs and a national park has helped prevent further destruction, but it has been concluded that active restoration is also necessary for the species’ recovery, with microfragmentation emerging as a viable solution. The primary aim of this study was to observe if the growth speed of fragmented polyps were affected by either substrate they were attached to, or colony they originated from. The secondary aim was to observe if the growth speed and survival of split coral fragments were affected by nutrition availability. Growth was measured using photogrammetry where images were taken at the beginning and after 10.5 weeks of treatment and then rendered into 3D-models after. The mean and volumetric growth was calculated by comparing the models in CloudCompare and MeshLab and then analysed using RStudio. Mean growth for all whole coral fragments measured between ~0.97-0.442 mm and the volumetric growth varied between ~7.51-30.6 %. The mean growth for the split polyps varied between ~0.122-0.462 mm with most tissue-face up fragments generating a new head. While growth was observed in all the corals analysed, the size of growth from the model comparisons was unrealistic and yielded no significant results for any of the statistical tests. This study was limited by several factors including low-quality models, no calcein staining, and time limitations. In conclusion this thesis should be seen as a pilot study and if the above issues were to be solved in a future study more accurate results may be obtained.