The late Pleistocene ostracod record of the crater lake sediments from Lago di Albano (Central Italy): Changes in trophic status, water level and climate

Four cores (ranging between ca. 9 and ca. 14 m in length) from Lago di Albano in Central Italy were studied for their ostracod content, as well as algal and bacterial pigments, CaCO3 and concentration of organic matter. Cores PALB 94 1E and PALB 94 1C from Site 1, located at the bottom of a steep slope at 70 m water depth, where oxygen concentration is below 6 mg l(-1), spans the Holocene and the late Pleistocene until 28 kyr B. P. (calibrated age). The other cores, PALB 94 6A and PALB 94 6B taken at a depth of 30 m, where oxygen is 7-11 mg l(-1), represent mainly Pleistocene deposits. Ostracod valves were found in the lowermost ca. 3 m of the sequence at Site 1, dated to ca. 28-24 kyr B. P., and throughout the sequence from Site 6 which represents the interval 23-17 kyr B. P. Candona neglecta is the dominant species in most of the levels at Site 1, whereas both C. neglecta and Cyclocypris sp. dominate during different biostratigraphic zones at Site 6. The influx of springs entering the lake at Site 1 was inferred on the basis of species of the genus Potamocypris and Ilyocypris bradyi present in the record. Wide fluctuations in species abundance and assemblages in both coring sites indicate lake-water level oscillations between 28 to 17 kyr B. P. In particular, a strong rise in water level of the order of 40 m occurred between 24 and 23 kyr B. P. Fluctuations in productivity, oxygen availability and water temperature at both sites were also reconstructed on the basis of the ostracod assemblages and the algal and bacterial pigment concentrations. The environmental reconstruction reached using ostracod remains and pigments was verified with other proxy records published elsewhere such as invertebrate remains, diatoms, magnetic properties, etc. A synthesis of climatic reconstructions for Central and Southern Italy for the late Full Glacial is attempted on the basis of previous studies on hydrology, lithostratigraphy and palynology. Sharp fluctuations in lake palaeoproductivity/palaeoclimate recorded by invertebrate and pigment remains at both sites from Lago di Albano might be related to similar events reported in North Atlantic Full-Glacial records from marine and ice cores.