Late Holocene evolution of the coastal and estuarine lakes of the Snowy River Floodplain (SE Australia): salinity regimes, nutrient dynamics and anthropogenic impacts.

Coastal lake and estuarine systems across south eastern Australia act as both sedimentary and biological amplifiers, and are more sensitive to cumulative catchment-driven hydrological change than previously recognised (see Tibby et al., this volume). Deciphering natural responses to climate change and geomorphology, and ensuing historical responses to catchment clearance and regulation reveals whether these systems now lie within pre-disturbance variability, and the extent to which anthropogenic change is unidirectional. A multi-proxy palaeoecological assessment of the terminal coastal and estuarine lakes of the Snowy River floodplain will be presented. The Snowy River is one of Australia’s hallmark river systems. Its catchment has been substantially modified since the mid 1800s. The ecological and water quality impacts of a major inter-basin transfer of up to 99% of its flow since the mid 1960s are poorly understood. Incorporating a diatom-water quality inference model, stable isotope and fossil pigment reconstruction, this study has examined (a) notions of variability in the progressive evolution of the system (b) how the records compare to that of a relatively un-impacted (control) system nearby (c) the influence of natural perturbations on the ecology of these lakes (with respect to salinity and nutrient status), as well as (d) the nature and timing of anthropogenic disturbance. Explained as a combination of land clearance, drainage practices, and more recently, substantial flow diversion in the Snowy River, recent water quality changes are as pronounced as any experienced through the Holocene. However, they have occurred at a rate faster than those brought on by past climatic or geomorphic change.International Union for Quaternary Researc