Fish fossils as paleo-indicators of ichthyofauna composition and climatic change in Lake Malawi, Africa

Numerous biological and chemical paleorecords have been used to infer paleoclimate, lake level fluctuation and faunal composition from the drill cores obtained from Lake Malawi, Africa. However, fish fossils have never been used to examine changes in African Great Lake vertebrate aquatic communities nor as indicators of changing paleolimnological conditions. Here we present results of analyses of a Lake Malawi core dating back ~144ka that describe and quantify the composition and abundance of fish fossils and report on stable carbon isotopic data (δ¹³C) from fish scale, bone and tooth fossils. We compared the fossil δ¹³C values to δ¹³C values from extant fish communities to determine whether carbon isotope ratios can be used as indicators of inshore versus offshore pelagic fish assemblages. Fossil buccal teeth, pharyngeal teeth and mills, vertebra and scales from the fish families Cichlidae and Cyprinidae occur in variable abundance throughout the core. Carbon isotopic ratios from numerous fish fossils throughout the core range between -7.2 and -27.5%, similar to those found in contemporary Lake Malawi benthic and pelagic fish faunas. These results are the first paleo-record of fish fossils from a Lake Malawi sediment core and the first reported δ¹³C values from Lake Malawi fish fossils. This approach provides a new methodology and framework for interpreting pelagic versus inshore fish faunas, lake level fluctuations and the evolution of the Lake Malawi fish assemblages.