Life in the intertidal zone along the Overberg Coast
Coastal intertidal zones provide a varied habitat of extremes: amazing animals and plants that have adapted and evolved to combat the pounding waves, desiccation at low tide, changes in salinity and temperature in the estuaries and rock pools. The intertidal region is an important model system for the study of ecology. The region contains a high diversity of species, and the zonation created by the tides causes species ranges to be compressed into very narrow bands. This makes it relatively simple to study species across their entire cross-shore range, something that can be extremely difficult in terrestrial habitats.
Where life began
Rocky shorelines frequently contain tidal pools of varying sizes, and they may have provided some unique conditions that would have made biogenesis possible, (the chemistry that created this primordial soup 4 billion years ago). When gazing into a rock pool, spotting the many different organisms in this ecosystem, it’s worth pondering life’s origins born of this environment of extremes.
A hint at our own aquatic past is suggested in a correlation between the human menstrual cycle and the lunar cycle. Many aquatic species follow the same lunar cycles influence on the tides for reproduction.
Stone-age man’s footprint
When Neanderthal man was still ruling supreme in Europe, modern people were living in caves along the Overberg coast 85/100 thousand years ago. Evidence of this has been found in Klipgat cave in the Walker Bay Nature Reserve, (in De Kelders), one of the most important cultural assets in the Western Cape. One can visit this cave and see how the Khoisan’s way of life set the blueprint for our first steps out of Africa.
Everywhere along the Gansbaai coastline there are heaps of shell’s and other debris that result from early people visiting the shore and collecting shellfish. These refuse dumps of ancient beachcombers give us an invaluable insight into tens of thousands of years of history, a priceless and fragile heritage resource. Shell middens are protected by legislation in South Africa, and no private excavation is allowed.
The Khoisan were the first to discover the healing qualities in the various parts of fynbos plants. Much of this knowledge was embraced by the early European settlers in the Cape; some of this knowledge is still used today by traditional healers and in modern medicine. Wild plants are protected by law in SA, and may not be picked, dug up or destroyed.
An important part of the coastal experience is discovering the benefits of the abundant plant life. Seaweed is mostly edible (but not always palatable), full of protein, calcium, minerals, vitamins and trace elements. It’s an aquatic pharmacy, an untapped sustainable resource. The list of other everyday products derived from seaweed is astonishing: toothpaste, dental moulds, welding rods, audio speakers, gravies and beer are but a few.
Whales and dolphins
Undoubtedly the best place to spot whales from land in SA is De Kelders, near Gansbaai. From June each year large numbers of Southern Right whales, Eubalaena australis, arrive in Walker Bay to give birth and mate. This bay seems to have the perfect conditions for these gentle giants. Dozens can be seen close up from vantage points along the cliff path of De Kelders. Humpback whales, Megaptera novaeangliae, also pay a visit here on their long migration path, and stay to recoup before continuing north. Bryde’s whales, Balaenoptera brydei, can be seen blowing off shore right throughout the year along with sometimes hundreds of dolphins torpedoing across the bay.
The amazing life of limpets
When it comes to limpets southern Africa is the world’s foremost biodiversity and biomass hotspot, with some areas having densities of 2,600 individuals per square meter. Limpets at first glance are static, even boring creatures, but a closer look reveals an evolutionary masterpiece. Cape false-limpet uses chemical weapons as defence; Giant limpets use brute force in territorial battles; Ducks foot limpet develops and tends gardens of algae; Goat’s eye limpets slam their shells down like a guillotine, dismembering ferocious predators, Kelp limpet’s parachute from the canopy when kelp breaks loose in storms before being cast ashore. The Limpets’ shell shape and amazing adhesion has allowed them to become the dominant species on rocky shores exposed to heavy wave action.
Shipwrecks and Ghost ships
Over 140 shipwrecks lie off the infamous coast between Cape Infanta and Danger Point, which is near Gansbaai. H.M.S. Birkenhead’s tale of bravery and honour – coining the phrase “women and children first”- is but one of several tragic stories born of this treacherous coast. Many yarns of lost treasure and ghost ships spun in local communities over the decades have led to several successful salvage operations off the Southern Cape coast, retrieving some of the largest treasure caches ever found. The Flying Dutchman, who according to legend is destined to sail these seas until the end of time, was first seen off Danger Point in 1823.