Mid-Holocene and historical palaeoecology of the Albufera de València coastal lagoon

Abstract

Mid-Holocene and historical palaeoecology of the Albufera de València coastal lagoonThe 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 19 th 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.

Vegetation and peat accumulation steer Holocene tidal–fluvial basin filling and overbank sedimentation along the Old Rhine River, The Netherlands

“…Diploneis sp and Navicula digitoradiata are also associated with (vegetated) intertidal environments (Vos & De Wolf, 1988, 1993; Sawai et al ., 2002). The anomalous peak in Fragilaria species ( F. construens, F. lapponica, F. nitzschioides, F. schulzii , classified as brackish–fresh, fresh, brackish–fresh and marine–brackish, respectively) at the onset of peat formation could point to stagnating (light) brackish shallowing waters (De Wolf, 1986b; Denys, 1989), but are also indicative of a relative increase of Phragmites habitat as opposed to mud habitat (Marco‐Barba et al ., 2019). The latter interpretation is more likely given its occurrence in Phragmites peat and the presence of other diatom assemblages indicating brackish inter to supratidal conditions.…”

Mediterranean Coastal Lagoons Review: Sites to Visit before Disappearance

“…The sediment of these lagoons, although quite recent, has served as an object of study to understand the changes that have taken place in the last thousands of years, as well as a record of the contamination received from the basin. Among these studies are those of the Albufera of Valencia [57], in which salinity changes in the lagoon are observed, the presence of contaminating metals such as in Bages [58] and Ghar El Melh [59], and the relationship between the conditions of the benthos and hypoxia in the water of the Berre lagoon [60].…”

Mid- to Late-Holocene coastal morphological evolution, vegetation history and land-use changes of the Porto Gulf UNESCO World Heritage site and its surroundings (NW Corsica Island, Western Mediterranean)

“…The coastal wetlands of the Mediterranean are of particular interest when reconstructing short- to long-term human-environment interactions, mainly at a local scale, as is attested by the abundant literature treating this topic over the last decade (Brisset et al, 2018; Di Rita and Magri, 2012; Fontana et al, 2017; Marco-Barba et al, 2019; Melis et al, 2017; Pascucci et al, 2018; Poher et al, 2017; Revelles et al, 2019). The general calm conditions accompanying sediment vertical accretion allow the acquisition of continuous sedimentary series, making coastal wetlands suitable places to reconstruct Early- to Late-Holocene environmental changes, using a series of sedimentological, geochemical and palaeoecological proxies (Brisset et al, 2018; Giaime et al, 2022; López-Belzunce et al, 2020; Marco-Barba et al, 2013; Sabatier et al, 2010).…”