Friday, 12 October 2007

Breathe easy

We had a road reference but the map we were using wasn't very detailed. The general reference was Yalgorup National Park, Lake Clifton south of Mandurah. Lake Clifton is very long and narrow so that wasn't much help.

So I thought that if we went to the general vicinity there would be signs to the significant thrombolites that are in the lake, but it turned out not to be the case. The actual sign, when we found it, was quite small and the road we were directed on to (Mount John Road) wound around in a suburban-type area, and there were no more signs to indicate whether we were in fact on the right track. Then the road changed to a dirt track through melaleucas and we were suddenly at the car park. They don't exactly encourage eco-tourists at Mandurah.

Lake Clifton is a coastal freshwater lake and apparently has the largest living thrombolite reef in the southern hemisphere. The rock-like formations, up to 1.3 m high, stretch in a wide band up to six kilometres along the bed of the lake. They are formed by microbes at a rate of about 1 mm a year, and differ from the famous stromatolites in Shark Bay in that they have a clotted internal organisation (think of 'thrombosis'). The stromatolites have a laminated or layered organisation.

Thrombolites, Lake Clifton

The organisms are responsible for the life on earth as we know it really, because for millions of years they were the only known form of life, existing in the shallow seas. Oxygen in the atmosphere increased from 1% to 21% because the micro-organisms precipitate calcium carbonate from water as they photosynthesise and in the process leak oxygen into the air. At Lake Clifton the thrombolites are still living because of upwellings of fresh groundwater high in calcium carbonate.

Boardwalk, Lake Clifton

The side-trip in to Lake Clifton to see the thrombolites was worth the time and trouble. There is a very informative information board in the carpark, and there is a boardwalk so the fragile formations can be viewed easily without doing any damage. We visited in September and the water level was high but we could still see them easily. Apparently a visit in late summer when the water level has dropped would be fantastic – I have seen wonderful photos of the exposed mounds. So…take a deep breath and thank the millions of organisms that contributed to Earth's oxygen supply.

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