Blue Lagoon, South Australia: A closed marine lake harbouring potential invaders of continental saline lakes?

Australia is a land of saline lakes, largely seasonal in the south and episodic elsewhere, populated almost exclusively by a fauna derived from freshwater ancestors (BAYLY & WILLIAMS 1966) and largely o f endemic crustaceans. Dominants include anostracans Parartemia spp., copepods Calamoecia spp., and ostracods Australocypris and related genera. A few species have colonised the saline lakes from terrestrial sources (e.g., the slater Haloniscus searlii; BAYLY & ELLIS 1969) and from the marine environment (e.g., the harpacticiod copepod Mesochra baylyi; BAYLY & WILLIAMS 1966). Although the salinity may be in the appropriate range, there are few invaders from the sea because the intermittent nature of most continental lakes means a survival mechanism for dry times is needed, and such are generally absent in marine species. At a few places on the long Australian coastline there are lakes that were once marine but are now transformed to intermittent continental waters, or still marine and maintaining contact via underground waters. Examples of the former occur in the Beachport-Robe area of South Australia (BAYLY 1970) and of the later on the west coast of Eyre Peninsula, South Australia (TIMMS 2009). These were and continue to be populated by marine species capable of living in waters isolated from the sea and hence are likely sites for marine invasion of continental saline lakes. I examined these cases with special reference to Blue Lagoon, via Penong, South Australia, a lake hitherto not mentioned in the literature.