of course, also includes feral cats.
Shark Bay is a huge and ragged bite into the profile of the west coast of Australia. It has now become a World Heritage Area, which brings more money and more tourism. Much of the former, and nearly all of the latter, is directed to the beach resort of Monkey Mia where ‘swimming with dolphins’ is on offer. When I flew over the Bay and its clear waters in a light plane, I saw an undulating submarine prairie of sea grass, dark emerald green, broken into banks like meadows. A tenth of the world’s dugongs – 250 kilograms of peaceable herbivorous sea mammal – graze in leisurely fashion upon this luscious expanse, many living to seventy years or more. Juicy fishes doubtless account for the name of the Bay, since they attract fourteen species of sharks, including species like the tiger shark that command respect. From the air I saw how Shark Bay is divided into two large lobes by a median peninsula; the aboriginal name for the Bay is ‘cartharrgudu’ (‘two bays’). The top of the peninsula is now the Francois Peron National Park and a serious attempt is being made to clear this sandy area of feral goats and predators for the benefit of the native fauna and flora. Dirk Hartog Island provides an outer barrier to the Bay, which protects the coast from storms cutting across the Indian Ocean. I never knew before visiting Western Australia that this island was the first landfall for any European. The Dutchman, Dirk Hartog, landed here on 25 October 1616, beating Captain Cook to it by 152 years, and leaving a pewter plate nailed to a post as evidence. That plate is still preserved in the Rijksmuseum, Amsterdam. William Dampier, ‘the buccaneer explorer’, spent a week there in 1699 and gave the Bay the name we use today. The aboriginal fishermen were plying their trade at the time, but there is little evidence of them now. I conclude that it is not only small and shy marsupials that failed to survive.
My quest is for something altogether more recherché than shark or dugong. At the tip of the eastern bay the edge of the sea provides a prospect of life two billion years ago … I am travelling incredibly far back in time. The journey to the old telegraph station at Hamelin Pool takes me through undulating, intensely green scrub interspersed with a few mallee trees, interrupted only occasionally by flat-bottomed depressions carrying scrappy salt-scrub and patches of white gypsum – the aboriginal inhabitants called these clay-pans birridas. I missed the flowering season, and now all the bushes seem to bear black nuts. Next come low dunes made up of startlingly white tiny shells. I crunch my way across the dunes, and beyond lies a very shallow arm of the sea. This is where the stromatolites grow. I am approaching the famous site where living analogues still flourish of the most ancient organic structures on earth. They ought to have disappeared long before the first velvet worm or horseshoe crab, but here they linger on, a marvel of anachronism.
Back at the highway must be the only road-sign in the world that points to ‘STROMATOLITES’, and no geologist or palaeontologist could fail to follow its bidding. Here they are growing by the shore while the sea beyond shines an almost improbable ultramarine. Is this luminous vision the time warp I sought? Some part of me expects the stromatolites to be green, but they prove to be darkish umber brown. I confess I am momentarily disappointed. They comprise flat-topped cushions and low pillars, or even giant mushrooms expanding upwards like plush stools, with sandy gullies between them. They are regularly disposed along a seaboard more than a hundred yards wide; seawards they disappear beneath the barely lapping waters. It is a scene of perfect calm. A little walkway has been built over the strand so that visitors can get close without damaging the organic structures. I touch one of the hummocks. It is actually quite hard (why did I expect it to be soft?) and slimy or tacky to the touch when moist, but almost crispy when dry. In the bright Australian sun it is even a little warm. Now that I get closer I can see other kinds of surfaces along the shore, particularly sloping stretches of dimpled microbial mats, a fruity brown colour, running down to the glittering sea. They make stretches of the shoreline resemble wrinkled skin. Stromatolites growing at the water’s edge look less like cushions and more like knobbly cauliflower heads. The inevitable flies are buzzing about my head, and some antipodean swallows chirrup cheerfully about the platform. I hope they are after my flies.
Up on the shore are some dead stromatolites, left behind by the sea maybe a thousand years ago. By now they have decayed into iron-stained ruins, but where they have broken open they show the internal structure of the cushion-shaped columns. It is clear to me that the columns are layered internally parallel to their top surfaces, rather like filo pastry. They seem to be built up layer by layer – a little like those giant stack pancakes an unwary visitor gets offered in New York for breakfast. The columns were evidently living things, self-made towers. A little museum on the site of the old telegraph office nearby provides more explanation. I peer closely at a stromatolite kept in a glass tank; its enveloping seawater must be refreshed every month. I see that when water covers the column its surface is slightly fuzzy – no doubt, it is still alive. A lack of crisp definition is somehow a proof of metabolism in action, life blurring the edges. Little bubbles fizz upwards off the top in a steady stream, none bigger than a lentil: they are bubbles of oxygen. So the column is evidently more than a brownish crust, it is something altogether more potent and dynamic, and it is breathing out oxygen, the element that babies and bilbies and bunnies all need to stay alive. Everyone has had nightmares about suffocation, when fighting for breath becomes fighting for life, so we all know in our bones how quickly we would perish without oxygen. The exhibition reminds me of the demonstration of nature in action at my very first school, when us kids looked at water-weed in a full glass beaker, and saw the same little bubbles of oxygen rising to the surface. This was the first time I heard the word ‘photosynthesis’.
The survival of the stromatolites on the beach is another measure of their toughness. On the foreshore I see two broad grooves carving their way through the stromatolite grove. These are the persistent traces of a former industry. In the late nineteenth and early twentieth century, camel trains brought bales of wool here to Flagpole Landing. These were then carted off the foreshore to lighters that sailed 190 kilometres to a boat waiting in deep anchorage off Dirk Hartog Island. Then the wool was transported to Fremantle and finally to the United Kingdom for manufacturing. We are fortunate that these activities did not destroy the mounds completely. But it is also a measure of the slow rate of biological activity hereabouts that the old tracks are still visible after a century.
Sea conditions in this part of Shark Bay are quite particular. The shallow seawater evaporates fast under the relentless sun. It is the basis of a salt industry at Useless Loop nearby. The very clear water has an elevated salinity and is very poor in nutrients. Hamelin Pool is backed up behind a sand bar known as Fauré Island, lying about forty-seven kilometres out to sea, so it is almost a lagoon. Only specially adapted or tolerant organisms can survive under these conditions. One of those animals is a little clam called Fragum hamelini, which, as the name implies, is special to this locality. It is so abundant that its snow-white shells, none bigger than a walnut, make up the dunes that line the Bay. After some decades the shells harden into a shelly rock – it would be an exaggeration to call it a limestone. An old quarry above the shore records the employment into which this curious white stone has been pressed. Cut into blocks the size of large bricks it made a serviceable, if hardly robust building stone. Some of the older edifices made of it still stand. The stone was used to build the walls of the Pearler Inn in the town of Denham, eighty kilometres distant. This pub looks as if it were constructed from a mass of white peas. In order to survive the testing conditions in the Bay, Fragum has incorporated photosynthesising algae into its tissues: sunlight is the ultimate source of its food, just as it is for the stromatolites. But Fragum is an evolutionary newcomer, whereas the stromatolites are very, very ancient.
Stromatolites are mounds slowly built up by microscopic organisms, layer by layer. The mounds are not composed of a single organism: they are a whole ecology. The tacky or slimy skin that caps the stromatolites is the living part. This very thin layer is composed mostly of cyanobacteria, organisms that are often called ‘blue greens’ (or, formerly and incorrectly, blue-green algae) on account of their characteristic hue beneath the microscope. This may well explain why I expected the stromatolites to be green. The conditions in Hamelin Pool suit their growth. There are many organisms in nature that like to graze on ‘blue greens’. Think of those finely scalloped trails wandering over moist rocks
