Distinct phases of relative sea level changes in the central Adriatic during the last 1500 years — influence of climatic variations?

We present a new sea-level reconstruction for the past 1500 years based on biological indicators from the Central Adriatic islands. Biogenic littoral rims built by the coralline rhodophyte Lithophyllum byssoides were found on the particularly exposed sites on the rocky coasts of the islands of Vis, Ravnik and Biševo in Croatia. The presence of thick and well-developed Lithophyllum rims, considered to be precise (± 10 cm) sea-level indicators, points directly to the rising sea-level environment. Biogenic rims were mapped, measured and sampled for 14C dating.The obtained results point to four phases of sea-level changes. The sea-level was near stable from around 550 till 770 cal AD, in the Dark Ages Cold Period (DACP), then during the Medieval Climate Anomaly (MCA) (770 till 1330 cal AD) the sea-level increased at a rate of 0.71 mm/yr. During the Little Ice Age (LIA) (1330 till 1640 cal AD) it was near stable again. Later, the sea-level started to rise at a much higher rate particularly during the Current Warm Period (CWP). These data were compared with local predictions derived from a glacio-hydro-isostatic models associated with the Last Glacial cycle. If the isostatic–eustatic component is separated, this area seems to have almost stable tectonic conditions during the past 1500 years.Our results show that the large algal rims most likely grew during near-stable sea-level conditions that occurred during two relatively colder periods in the past 1500 years. They also reveal that well-developed (up to 1.8 m wide) upper levels of algal rims were formed during ~ 300 years of stabilisation throughout the LIA.

► Biogenic littoral rims built by Lithophyllum byssoides exist in the Adriatic Sea.
► Large algal rims up to 1.8 m wide grew during near-stable sea-level conditions.
► Near stable sea-level conditions occurred during two colder periods (DACP and LIA).
► Existing algal rims reflect palaeoenvironmental conditions.
► They could be related to geomorphological and archaeological sea-level indicators.