The Cape coast is characterised by having enormous forests of kelp (Ecklonia maxima). These remarkable plants grip the substrate with a holdfast and grow rapidly to the sea surface, where they maintain their position by way of a gas-filled bladder that ensures that their fronds are maximally exposed to sunlight for photosynthesis.
Besides being a characteristic feature of our shores, these kelp forests are vitally important in the ecology of the area. They act as a baffle, reducing the strength of the high-energy currents and providing a protected zone in which certain species can survive. Beaches are generally devoid of primary production – ie plant material that can support other life, but here in the Cape kelp is regularly ripped away from its substrate and deposited on the beaches where it provides a rich nutrient source for a variety of animals.
One of the species that is dependant on this rich food source Talorchestia capensis, often called the beach-hopper or sand-flea although they are more closely related to prawns and crayfish than to fleas!
These creatures occur in their millions wherever there is ample washed-up kelp and wherever they are not disturbed. They are terrestrial crustaceans and cannot survive in water. They have a built-in tide-table which informs them when to travel down the beach to look for freshly washed-up kelp, and when to retreat up the beach to avoid the incoming tide.
When you are next on a healthy Cape beach, turn the kelp over and see the seething masses of these hopping creatures that are supported by the washed-up kelp. It is largely this enormous population of crustaceans, supported by the kelp, which supports our enormous population of birds seen along the beaches.