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

Authors: Peter N. Reinthal, Andrew Cohen, David L. Dettman, Lisa Brooke McDonough

Year: 2008 (xl)

Abstract

Climate change is one of the most important issues confronting the long term survival of desert fishes throughout the world. Rarely do we see climate change addressed in the long-term planning or conservation of desert fishes. Two major approaches to analyzing climate change are models to predict future climate and using chemical and biological indicators to reconstruct past climate change. In contrast to aquatic invertebrate and algal fossils and terrestrial pollen, fish fossils have rarely been used in paleolimnological studies as indicators of limnologic or climate change, or faunal composition. Here we present first results of fish fossil analyses from Lake Malawi drill cores, covering the last 135ka. We have quantified fish fossil composition and abundance and measured stable carbon isotopic ratios in scales and organic fraction of bone and teeth. Fossils buccal teeth, pharyngeal teeth and mill, vertebrae and scales are found. These are identified from the fish families Cichlidae and Cyprinidae (Engraulicypris sardella) and demonstrate variation in abundance throughout the core. We report stable carbon isotopic ratios from numerous fish fossils throughout the core which show a range of Æ’Á”13C from -8.59 to -27.51, similar to that found in the contemporary pelagic fish fauna. These fish fossil records from Lake Malawi provide a new methodology and framework for interpreting pelagic versus inshore fish faunas that would correspond to lake level fluctuations and the evolution of the Lake Malawi fish.