Conservation of natural wilderness values in the Port Davey marine and estuarine protected area, south‐western Tasmania

Abstract

Abstract Port Davey and associated Bathurst Harbour in south‐western Tasmania represent one of the world's most anomalous estuarine systems owing to an unusual combination of environmental factors. These include: (i) large uninhabited catchment protected as a National Park; (ii) ria geomorphology but with fjord characteristics that include a shallow entrance and deep 12‐km long channel connecting an almost land‐locked harbour to the sea; (iii) high rainfall and riverine input that generate strongly‐stratified estuarine conditions, with a low‐salinity surface layer and marine bottom water; (iv) a deeply tannin‐stained surface layer that blocks light penetration to depth; (v) very low levels of nutrients and low aquatic productivity; (vi) weak tidal influences; (vii) marine bottom water with stable temperature throughout the year; (viii) numerous endemic species; (ix) strongly depth‐stratified benthic assemblages exhibiting high compositional variability over small spatial scales; (x) deepsea species present at anomalously shallow depths; (xi) no conspicuous introduced taxa; (xii) a predominance of fragile sessile invertebrates, including slow‐growing fenestrate bryozoans; and (xiii) sponge spicule‐ and bryozoan‐based sediments that are more characteristic of deep sea and polar environments than those inshore. Although this region has historically been protected by its isolation, seven major anthropogenic stressors now threaten its natural integrity: boating, fishing, dive tourism, nutrient enrichment, introduced species, onshore development, and global climate change. These threats are not randomly distributed but disproportionately affect particular habitat types. For management of environmental risk, the Port Davey–Bathurst Harbour region is subdivided into six biophysical zones, each with different ecological characteristics, values, and types and levels of potential threat. In response to the various threats, the Tasmanian Government has enacted an adaptive management regime that includes a multi‐zoned marine protected area and the largest ‘no‐take’ estuarine protected area in Australia. Copyright © 2009 John Wiley & Sons, Ltd.