The Leschanault Inlet estuary: Physical features and habitats for benthic fauna

The Leschenault Inlet estuary has a distinctive pattern of bathymetry, water salinity and sediment types. The estuary is a flat, elongate central basin, flanked to east and west by shallow, shore-parallel platforms. The central basin grades into a shallow-water flat in the north, and adjoins deltas in the south. The estuary is underlain by mud in the central basin and northern flat, sand and muddy-sand on the eastern platform, mud, muddy-sand, sandy-mud and sand on the western platform, and predominantly sand under the deltas. The estuarine waters undergo seasonal changes in salinity as a result of restricted oceanic exchange, freshwater inflow during winter and evaporation in summer. Various salinity fields were identified in this study, based on the mean and range of salinity values occurring within the annual hydrological cycle. Hypersaline to mesosaline waters occur to the north, and increasingly more hyposaline to mesosaline waters occur to the south. Each of the large-scale geomorphic units in the estuary can further be subdivided on the basis of water salinity, bathymetry, substrate and presence of macrophytes. Based on these physical features, nineteen small-scale habitats units were proposed for Leschenault Inlet. These smaller scale habitat units provide a framework within which to study the distribution and ecology of benthic fauna.