Limnetica 34

In 2007, a rice field was transformed into a zone that simulates the different habitats which were typical before the environmental crisis that the current Albufera de València Natural Park experienced in the 70’s, in order to increase the species and habitat richness. One of these recreated habitats was a spring – a pond fed by groundwater. The spring was spontaneously covered with charophytes shortly after being flooded, and a community dominated by Chara hispida and Nitella hyalina remained, which were responsible for the maintenance of the clear-water state the spring exhibited. However, in recent years, there has been a sharp reduction in charophyte coverage and biomass. The values of some variables, which could have influenced this reduction, changed substantially over time. One of these variables was water salinity, which almost tripled in less than four years. In this study, the effects of increased salinity on the growth of charophytes and on the germination of fructifications (oospores and gyrogonites) were analysed to unravel whether a change in this variable could explain at least a part of the observed reduction of charophyte stands. Laboratory experiments were performed by applying two treatments, based on the use of water with different salinity levels, to the charophyte cultures (water collected from the spring in 2009, “Lower salinity”, and in 2013, “Higher salinity”). The increase in salinity caused both a decrease in the elongation of the charophyte’s main shoots and a reduction in weight in the higher salinity treatment. The decrease in growth was more pronounced in the more stenohaline species, N. hyalina. The stoichiometric composition of charophytes was also affected, depending on the salinity conditions and the species. At the end of the experiment, the means of percentage of carbon, nitrogen and phosphorus were significantly lower under the “Higher salinity” treatment only for N. hyalina. Although there were no statistically significant differences in fructification germination with the salinity treatments, qualitative differences in germling size were observed. Without rejecting other factors that might have negatively affected, in a synergistic manner or individually, the development of the charophytes in the spring, it seemed that the increase in salinity was one of the involved factors.