Leave something for a few thousand years and it's not going to be quite the same as you left, assuming it's still there (and you're still alive). That is, unless you're a lake hidden away on North Stradbroke Island, in which case not even the passage of 7500 years is enough to bother you.
Over this period, the creatively-named Blue Lake has experience barely any changes in its make-up or depth and as of today, is the only one of its kind in Australia, according to the University of Adelaide's Cameron Barr. Speaking to the ABC, Barr said the lake is essentially a "refuge for freshwater", given the unprecedented levels of stability.
While the researchers were surprised by the properties of the lake, they can provide some explanation. An aquifer constantly refreshes the lake, negating the effects of evaporation (which would make it more saline over time) and its contents feed out into a swamp. Apparently, this cycle has helped maintain Blue Lake and Barr believes there's no reason it won't continue to do so.
7500 years, you say? That's a fairly astounding level of equilibrium given how even the smallest changes in climate can have massive effects on an ecosystem.
Here's a link to Blue Lake if you'd like to check it out on Google Maps.