Estuary Form and Function: Implications for Palaeoecological Studies

Estuaries are, by almost any definition, variable places. Palaeoecological studies attempt to reconstruct past conditions. The validity of reconstructions is dependent on assumptions about the generality of conclusions, commonly based on a small number of samples from a limited spatial area. This Chapter summarises the main geomorphic, biogeochemical and biological processes in estuaries and provides a conceptual framework for understanding the temporal and spatial variability in factors that may affect palaeoecological evidence. We suggest that the ultimate preservation of paleo-indicators within an estuary is governed by the interaction between environmental drivers, estuarine stressors, and biogeochemical/ecological processes. We recognise that these interactions vary on temporal scales from diurnal tidal cycles to millennia, and spatially from a few square metres to whole system and latitudinal scales. We present a series of models that allow palaeoecologists to better understand the environmental context of samples collected from estuaries and make informed assessments of whether, and under what circumstances, the common assumptions may be considered valid.