Estudi experimental sobre els efectes nocius de l'esposició de larves d'eriçó a la dinoflagel·lada tòxica Ostreopsis cf. ovata

Trabajo final presentado por Marc Mascaró Triay para el Máster en Oceanografía y Gestión del Medio Marino de la Universitat de Barcelona (UB), realizado bajo la dirección de la Dra. Magda Vila Reig y de la Dra. Elisa Berdalet Andrés del Institut de Ciències del Mar (ICM-CSIC).-- 40 pages, 23 figures, 4 tables, 2 annexesBlooms of the benthic dinoflagellate Ostreopsis cf ovata seems to be increasing in frequency, intensity and geographic distribution (from tropical to temperate latitudes). This dinoflagellate produces the potent palytoxin (PLTX), which causes human diseases and, economical and environmental burden. When PLTX affects marine organisms of commercial relevance that additionally play key ecological roles, this creates cascading effects on the entire ecosystem. The aim of this study is to evaluate the impact of Ostreopsis cf. ovata blooms on the fertilisation and early development stages of the sea urchin Paracentrotus lividus (Lamarck, 1816). This marine species is considered to be one of the key ecological herbivores that regulate the structure and dynamics of the Mediterranean algal communities. Eggs and sperm of P. lividus were experimentally exposed to different concentrations of O. ovata (40, 400, and 4000 cells ml-1) in two eco-toxicological assays. Furthermore, two assays were made with four O. ovata concentrations (4, 40, 400 and 4000 cells ml-1) either in exponential and stationary phases to test the mortality on competent P. lividus larvae. Our hypothesis was that the presence of O. ovata impairs fertilisation as well as embryonic and larval development of the sea urchin, and could even cause mortality in these two development stages. Reduced fertilisation, development failures, and elevated embryo and larval mortality were observed after exposure to O. ovata. The effective fertilisation decreased (31,4% ± 2,5) when gametes were exposed to high concentrations (stationary 4000 cells ml-1). The highest percentage of larval mortality occurred on highest concentrations (stationary 4000 cells ml-1), reaching 74,8% ± 6,1 at 100 hours. We show that Ostreopsis blooms may negatively impact larval fitness and therefore, compromise recruitment success of sea urchin populations, possibly with broader ecological implicationsPeer Reviewe