Efectes de la concentració de clorofil·la i la temperatura en la reproducció d’Eunicella singularis (Cnidaria: Octocorallia) : Effects of chlorophyll concentration and temperature on the reproduction of Eunicella singularis (Cnidaria: Octocorallia)

Abstract

Sexual reproduction is a fundamental biological process for the perpetuation and the genetic diversity of the most living species. In marine sessile invertebrates, such as corals and gorgonians, it allows the dispersal of individuals, the colonization of new areas and the genetic flux among populations. Its high energetic cost force organisms to find a trade-off between growth, survival and reproduction. The main determining factor of the energetic availability in marine sessile invertebrates are temperature, nutrients and light. In the western basin of the Mediterranean sea, there is a seasonality in the temperature and an upwelling phenomenon occurring between March and April. The upwelling causes an increase of the primary production (quantifiable through chlorophyll concentration in sea water) and enriches the whole food web. In 2017, an increase of the chlorophyll concentration was observed in the Cap de Creus (Girona) surrounding waters before the typical upwelling time. This has motivated the present study with the aim of find out the real change in the upwelling phenomenon and how it has affected in the reproductive cycle of Eunicella singularis (Esper, 1791) as a representative specie of benthic sessile invertebrates. An environmental characterization and E. singularis population sampling were needed to obtain all the required data. The results of 2017 had been compared with previous data from 2010 and 2011. The results shown that there was not an increase of the nutrients but an advancement in the upwelling timing. This change in the nutrient cycle has affected the sexual product of E. singularis, which has increased the number of oocytes and sperm sacs but not its diameter