Restoration of effluent-affected intertidal rocky shores: what have we learnt and where to from here?

As coastal population growth increases globally, effective waste management practices are required to protect coastal biodiversity. Water authorities are under increasing pressure to reduce the impact of sewage effluent... [ view full abstract ]

As coastal population growth increases globally, effective waste management practices are required to protect coastal biodiversity. Water authorities are under increasing pressure to reduce the impact of sewage effluent discharged into the coastal environment and restore disturbed ecosystems. Fucoid (brown) algae often dominate intertidal rocky shores providing habitat and modifying ecosystem resources for other species, but are susceptible to discharge of sewage effluent. The losses of fucoid habitats have led to significantly altered assemblages on effluent-affected shores. Effluent remediation efforts that focus on restoration of fucoid algae should result in effective restoration of rocky intertidal ecosystems. But what are the barriers to restoration of fucoid algae on effluent-affected shores? Focusing on the Australasian intertidal fucoid, Hormosira banksii, we present a conceptual model to guide research efforts that may inform coastal managers and water authorities. We present data that support a model of alternative community states between H. banksii dominated canopy on rocky substrata vs. C. officinalis turf that switch in response to sewage-effluent disposal. Moreover we present experimental results that show recovery of Hormosira banksii populations is susceptible to a) persistent unfavourable water quality, b) lack of a conspecific canopy at effluent-affected sites and c) competitive exclusion by coralline turfs. Finally we present research priority areas leading forward to maximise the potential for successful restoration of remediated rocky shores.