Dead or alive: sediment DNA archives as tools for tracking aquatic evolution and adaptation

Abstract

DNA can be preserved in marine and freshwater sediments both in bulk sediment and in intact, viable resting stages. Here, we assess the potential for combined use of ancient, environmental, DNA and timeseries of resurrected long-term dormant organisms, to reconstruct trophic interactions and evolutionary adaptation to changing environments. These new methods, coupled with independent evidence of biotic and abiotic forcing factors, can provide a holistic view of past ecosystems beyond that offered by standard palaeoecology, help us assess implications of ecological and molecular change for contemporary ecosystem functioning and services, and improve our ability to predict adaptation to environmental stress. U ndisturbed lake and marine sediments are natural archives of past changes in biota and their environment, and when dated, they offer the opportunity of reconstructing past changes in e.g. both primary and secondary production and community composition 1,2. Analysing organismal remains in freshwater and marine sediment cores provides a long-term perspective of ecological change and has a long history in both pure science and applied contexts 3 (Table 1). In the more traditional approaches to the palaeoecology of aquatic systems, microfossil analysis is accompanied by a number of geochemical proxies including lipid biomarkers, pigments and isotope composition (Table 1). The interpretation of these archives, i.e. the science of palaeoecology, is dependent on understanding contemporary ecological controls as well as the sedimentation environment and its context. The remains of a diverse range of

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