Comparative reproductive assessment of the native and replanted pink sea fan Eunicella verrucosa

Sammanfattning

Sea fans are known to play a large role in ecosystem engineering and in keeping marine environments biologically versatile. The pink sea fan Eunicella verrucosa is found in the northeast Atlantic and the western Mediterranean Sea. It is a common octocoral, which many other species rely on at one point in their lifecycle, either for shelter or food. However, mechanical damage, such as bottom trawling with large fishing nets, can cause damage to these corals, with bycatch fragments brought to the surface in nets often being discarded, despite their viability. A common conservation effort to support the recovery of impaired coral colonies is the replantation of fragments, as it offers an inexpensive and accessible way to support decreasing coverage. This method could, however, limit genetic diversity within the population, making their sexual reproductive ability crucial for surviving changing environmental conditions. This study examined replanted and naturally growing Eunicella verrucosa individuals for reproductive differences by examining oocyte size and polyp fecundity. Histological and microscopical analysis of both groups was conducted on samples from the eastern Atlantic. It was found that the oocyte size distributions differed a lot between the groups. Additionally, the fecundity analysis showed differing numbers of previtellogenic and vitellogenic oocytes in replanted, compared to natural corals, as well as a change in total fecundity. These results show that the reproduction and spawning pattern is altered in the replanted coral fragments. It is, however, not possible to say if these changes stem from the replantation process or from the change in environment the corals experienced. Future research observing colonies at several time points might be able to uncover the reproductive changes and adaptations the corals go through during transplantation.