The Lake Cowan Salt Lake

Salt lakes can be so salty that salt precipitates in particles on the surface - or so fresh that tadpoles are able to survive in them - and this can be in the same lake (though not at the same time).
With underlying clay and gypsum layers registering high salt levels small rainfall events produce shallow and highly saline water on the lake's surface.
This water evaporates or drains away into the sediments of the lake 'bottom' quite quickly, and is of little help in establishing or supporting life.

Big rainfalls produce substantial inflows, giving the salt lake a depth of up to a metre of basically fresh water.
This is 'sweet' enough and long lasting enough for many types of invertebrate fauna to hatch out and go through their life cycles before the lake dries up or becomes too salty to support life.
It is under these circumstances that whole food chains develop around the lakes, supporting teeming flocks of waders and waterbirds.

Life on and around salt lakes is not only tough going for fauna - flora too, has to be highly adapted to survive these arduous conditions.
Plants that grow in salty environments have developed different ways of dealing with the salt and the harsh conditions.

Samphires have salts in their cells to regulate their osmotic balances.
When it is very hot and dry they 'shut down'- often turning purple or red. Under these circumstances they do not produce any new growth.
Often peripheral vegetation dies off and the plant will look like a stick with just a couple of tiny 'branches' alive.
Yet when rain comes, the plant will turn green and will quickly produce new growth and flower spikes as if to celebrate its survival.

The various species of Frankenia have developed remarkably long root systems and appear able to exude salt from their leaves, which are very small and hard (to reduce moisture loss).
Most salt bushes (Atriplex sp) have silvery grey and slightly hairy leaves to reduce moisture loss - and do not live as close to the salty water as the Samphires or Frankenias.



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Last updated: Friday, 04.06.2010 12:15 PM