COLONIZATION PROCESS IN NEW CREATION MEDITERRANEAN COASTAL LAGOONS

The colonization process in new creation Mediterranean salt marsh lagoons is influenced by hydrological fluctuations characterised by flooding-confinement periods. This pattern has direct effects on water characteristics (such as nutrient concentration), but it also effects the connectivity structure between lagoons impacting main metacommunity dynamics. Unfortunately, these ecosystems have suffered transformations due to urbanization process that has contributed to its degradation. This is the case of La Pletera salt marshes, located in the NE of Catalonia, in where a recovery and restoration European LIFE project (LIFE13 NAT/ES/001001) that included the restoration of existing lagoons and the creation of new ones has been done. In this study, we analysed the structure of aquatic macrofauna community of these new created lagoons just after its creation and five years after its creation with the aim of assessing the colonization assembly process. Our results showed a fast colonization of the species with active dispersion since they dominated the communities right after lagoon creation (Diptera). In contrast, species with passive dispersion (Gastropoda and Amphipoda) that have a lower dispersive capacity were dominant at the last sampling survey, 5 years after creation. This could be explained by flooding periods that connect all wetland waterbodies favouring the arrival of both, active and passive dispersers. Moreover, we observed an increase in the abundance and biomass of taxa with lower dispersion capacity but without affecting the overall community richness values

Factors que determinen la distribució i migració del zooplàncton en un embassament eutròfic amb limitació d’oxigen

Curs 2019-2020Els fenòmens de migració de les espècies animals són resultat de canvis en el seu cicle vital o en el propi entorn en el que es desenvolupen. En el cas del zooplàncton de llacunes i embassaments d’aigua dolça, es tracta d’un desplaçament motivat majoritàriament per l’evasió dels depredadors, on les espècies es desplacen a zones de refugi durant el dia, com les parts profundes dels llacs o bé les zones amb vegetació, i durant la nit tornen a la superfície per alimentar-se, així doncs, que es troba determinat per el fotoperíode. Aquest desplaçament per buscar refugi es dona de manera vertical en la columna d’aigua, o bé de manera horitzontal quan aquesta massa d’aigua no és prou profunda. No obstant, en el següent estudi ens plantegem si l’anòxia en les parts profundes de les llacunes i embassaments, fa que el zooplàncton no trobi condicions favorables al fons i es desencadeni la migració horitzontal. El mostreig es va portar a terme en l’embassament de Sau, situat a la comarca d’Osona, Catalunya, el qual presenta característiques eutròfiques i limitació d’oxigen a l’hipolímnion durant els períodes estivals. Per mostrejar el zooplàncton i les variables ambientals associades, es va realitzar un mostreig al centre de l’embassament a diferents profunditats a migdia i també en la totalitat de la columna d’aigua tant a migdia com a mitja nit. Els resultats no van ser concloents per afirmar que a l’embassament de Sau hi hagi migració horitzontal del zooplàncton. Tot i això, l’estudi en paral·lel de les característiques fisicoquímiques de la columna d’aigua, així com de la distribució i composició de fitoplàncton i zooplàncton al llarg de la columna d’aigua ens han permès concloure que l’oxigen i la qualitat de l’aliment són els factors determinants de la distribució vertical del zooplàncton, així com ho són les competències interespecífiques.The migration phenomena of animal species are the result of changes in their life cycle or in the environment in which they develop. In the case of zooplankton of lakes and reservoirs, it is a displacement motivated mainly to avoid predators, where the species move to areas of refuge during the day, such as the deep parts of the lakes or areas with vegetation, and during the night returns to the surface to feed, so that, is determined by the photoperiod. This displacement to seek refuge occurs vertically in the water column, or horizontally when this body of water is not deep enough. However, in the following study, we consider whether anoxia in the deep parts of lakes and reservoirs causes that zooplankton do not find favourable conditions at the bottom and this triggers horizontal migration. The sampling was carried out in the Sau reservoir, located in the Osona region of Catalonia, which has eutrophic characteristics and limited oxygen in the hypolimnion during the summer periods. To sample zooplankton and associated environmental variables, sampling was performed in the middle of the reservoir at different depths at midday and on the entire water column at both midday and midnight. The results were inconclusive to state that there is horizontal migration of zooplankton in the Sau reservoir. However, the parallel study of the physicochemical characteristics of the water column, as well as the distribution and composition of phytoplankton and zooplankton along the water column have allowed us to conclude that oxygen and food quality are determining factors in the vertical distribution of zooplankton, as well as interspecific competencies