Recent human‐induced salinity changes in Ramsar‐listed Orielton Lagoon, south‐east Tasmania, Australia: a new approach for coastal lagoon conservation and management

Abstract

ABSTRACT1. Many coastal lagoons in eastern Australia have changed as a result of recent human activities. However, it is often difficult to determine the extent of change and the ecological implications. A palaeoecological approach allows a quantitative assessment of how an aquatic ecosystem changes and responds to human impacts beyond what is possible with historical data or monitoring programmes.2. Orielton Lagoon (south-east Tasmania, Australia) is a Ramsar-listed coastal wetland of international importance for conservation. This study was undertaken at the site to determine whether recent anthropogenic hydrological modifications to the lagoon had influenced its ecology, particularly salinity, and compromised its Ramsar status.3. A diatom-salinity transfer function was constructed from a training data set of 96 diatom taxa from 34 sampling sites in 19 lagoons along the east coast of Tasmania.4. The salinity of Orielton Lagoon has changed in response to a causeway constructed across its mouth, which has transformed the lagoon from an open marine environment to an enclosed, virtually stagnant, brackish water body.5. These changes have compromised the protected coastal wetland status of Orielton Lagoon. Environmental remediation attempts have since partially restored the natural hydrology of the lagoon and it is now returning towards the state it was in prior to causeway construction. 6. A palaeoecological approach using diatoms was found to be successful in reconstructing recent salinity changes and investigating human impacts on Orielton Lagoon over the last 50-55 years.

A diatom dataset and diatom-salinity inference model for southeast Australian estuaries and coastal lakes

“…The most common and widespread taxa (Table 4) are considered cosmopolitan species, characteristic of brackish, coastal and marine water bodies (Witkowski et al 2000) and have been identified in previous Australian coastal diatom studies (e.g. Fluin et al 2007;Haynes et al 2007;Saunders et al 2007;Taffs et al 2008). Table 3 for site codes and water chemistry information This study demonstrated that diatom assemblages in southeast Australian coastal lakes, lagoons and estuaries are primarily influenced by salinity.…”

“…Salinity has previously been found to be the overriding environmental variable influencing Australian diatom communities and diatom-salinity (or -conductivity) relationships have been described (e.g. Hodgson et al 1997;Blinn and Bailey 2001;Gell et al 2002;Philibert et al 2006;Saunders et al 2007;Tibby et al 2007;Taukulis and John 2009). With the exception of Hodgson et al (1997) and Saunders et al (2007), none of these studies were conducted in coastal ecosystems.…”

“…Hodgson et al 1997;Blinn and Bailey 2001;Gell et al 2002;Philibert et al 2006;Saunders et al 2007;Tibby et al 2007;Taukulis and John 2009). With the exception of Hodgson et al (1997) and Saunders et al (2007), none of these studies were conducted in coastal ecosystems. Other factors not measured, such as grain size, water depth and light availability, can influence the composition of diatom communities (Stoemer and Smol 1999).…”

“…Hodgson et al 1997;John 1983;Sonneman et al 2000) and datasets (i.e. Hodgson et al 1996;Saunders et al 2007;Taffs 2005), with additional reference to European coastal diatom taxonomic references (e.g. Witkowski et al 2000).…”

“…In Australia, diatom inference models for coastal lake and estuarine environments have so far been developed for relatively small geographic regions (e.g. Hodgson et al 1996;Saunders et al 2007Saunders et al , 2008Taffs et al 2008). Yet in some studies it is desirable to have diatom-based inference models that span a wider range of modern analogues, over a wider geographic area to better encompass the range of variability encountered in sub-fossil deposits.…”