Paleoecología de la laguna costera de la albufera de València durante el holoceno medio y en época histórica

The Albufera de València coastal lagoon is one of the largest oligohaline lagoons in the Iberian Peninsula. Highly polluted and threatened by plans for urban development, it has been protected as a Natural Park since 1986 to preserve its environment and surroundings, mostly consisting of ricefields and a forested coastal sand bar. Restoration plans focus on recovering the water quality and submerged macrophyte cover that occupied most of the lagoon in the 1950’s. Until recent studies, little was known about the wetland’s palaeoenvironmental history. To improve this knowledge, we analysed the Holocene evolution of the lagoon based on sedimentology, geochemistry and microfossils (foraminifera, diatoms, ostracods and pollen remains) from four cores. Two were collected in the sand bar, and two from the central lagoon. In combination with previous work, our new data show that the lagoon remained brackish for most of its history since 8700 cal BP, with the frequent presence of accompanying freshwater taxa from 7000 to 3400 cal BP. Notwithstanding chronological uncertainties, some episodes of decline in the abundance of microfossils seem to match aridity events Bond 5 (8.2 ky BP) and Minorca 7 (7.5-7.2 ky BP), the latter marking the switch from a dominance of arboreal vegetation to grasses. The most important change in the water body consisted of a sharp change at the beginning of the 19th century from a brackish to an oligohaline lagoon, driven by anthropogenic hydrological control associated with the expansion of ricefields. Later on, by the 1960-1970’s, the growing population impacts of agricultural, wastewater and industrial effluents launched a major eutrophication process that would eventually sharply reduce the benthic vegetation and invertebrate communities and promote the phytoplankton dominance of the ecosystem in a turbid state. Although our multiproxy study has increased understanding of the lagoon’s history, somewhat supported by documentary evidence, further palaeoecological research in different parts of the wetland would help define the causes of heterogeneous timing of changes in this large, shallow, complex system. Notwithstanding the need for further research, there is a clear priority for managers and the society to work on restoration efforts to drive the Albufera wetland towards one of the previous, less impacted, states of this worn-out and neglected ecosystem.