Carbon accumulation and storage in a temperate coastal lagoon under the influence of recent climate change (Northwestern Adriatic Sea)

Pialassa Baiona is a shallow temperate coastal lagoon influenced by a variety of factors, including regional climate change and local anthropogenic disturbances. To better understand how these factors influenced modern organic carbon (OC) sources and accumulation rates, we measured OC as well as stable carbon isotopes (δ13C) in 210Pb-dated sediments within a vegetated saltmarsh habitat and a human impacted habitat. Relative Sea Level (RSL) at the nearby tide gauge station data and four different Sea Surface Temperature (SST) data sets were analyzed starting from 1900 to assess the potential effect of sea ingression and warming on the coastal lagoon sedimentary processes. The source contribution calculated from the MixSIAR Bayesian model revealed a mixed composition of sedimentary OC, dominated by an increase in marine-derived OC after the 1950s, matching with a decrease from autochthonous saltmarsh vegetation (Juncus spp.) in the saltmarsh habitat, and from riverine/estuarine-derived OC in the impacted habitat. RSL rise in the area (8.7±0.5 mm yr−1 in the period 1900-2014) has been mainly driven by the land subsidence, especially during the central decades of the last century, enhancing the sea ingression into the lagoon. RSL rise influenced changes in sedimentary OC sources and accumulation at different level within the two habitats from the 1950s onward; conversely, no direct effect of SST was detected.