It was a new moon accompanied by a spring low tide the day I joined Knysna Basin Project’s ShoreSearch volunteers on a survey of the Knysna Estuary. The sky was punctuated with clouds and seagulls as we skirted the exposed western bank. In the shallow water nearby, a lone heron stood regal and motionless. Several sacred ibises stood feeding in the thick eel grass beds a little further away. The scene that unfolded before us was beautiful beyond words - one designed by nature to feed the soul.
The wonder of this iconic body of water, however, lies not in its aesthetic character alone, but in the mind-boggling diversity of life which it supports. It boasts such an astonishing web of life that it is rated as environmentally the most important estuary in South Africa.
The Estuary’s gently shelving intertidal shore has an intricate diversity of plant and substratum habitats, all of which provide food and shelter to all sorts of weird and wonderful creatures. Just how many different creatures and the numbers in which they occur is what the dedicated ‘citizen scientists’ of the ShoreSearch project (one of the Knysna Basin Project’s current research programmes).
ShoreSearch kicked off in 2013 with the aim of recording and monitoring the diversity of species found in the Knysna Estuary’s intertidal zone. One of the project’s key objectives is to engage members of the public by encouraging them to participate as volunteers. This opportunity serves as an ideal learning platform for those interested in the natural world.
Led by project leader Frances Smith and her assistant, Peter Smith, we set off on that particularly beautiful morning armed with containers, quadrats, clipboards and curious minds.
Once we reached our survey area, one of 15 different sites chosen throughout the Estuary for this comprehensive study, Frances first released back into the environment all the species she had collected two days earlier for microscopic study.
The surveys are relatively simple and take about 2 hours to complete. The first task is to do a little walkabout noting everything that can be seen in order to build an overall picture of the area. Secondly, a transect line is placed across each habitat zone (e.g., rock, sand, eelgrass) from the low to the high water mark and then everything that is seen on either side is recorded. They then place quarter meter square quadrats in each different habitat zone and count everything found in it, looking both above and just beneath the surface. Some are taken back to the lab to confirm identification (and then released back to their homes).
On this occasion, my eyes were immediately drawn to the sporadic spurts of water coming from holes in the shale beds. I went on to discover that these holes are the life-long home of piddocks, a unique bivalve mollusc which has a set of ridges or ‘teeth’ which are used to grind away at soft rock to create tubular burrows. The piddock – which is rare in South africa - stays in the burrow it bores with only its siphon exposed to take in water that it filters for food.
Another eye-catching creature, of which there were hundreds washed up all along the shoreline, was the shaggy sea hare, an otherworldly looking sea slug quite vivid in colour, which feeds on algae.
It is not immediately obvious to the untrained eye that the shoreline is simply teeming with life, both above the exposed surface and below. Some species are so small that you can easily miss them, or they may be merely lurking just beneath the muddy surface. Guided by the trained eyes of Peter and Frances, the shoreline life is revealed and it is something quite extraordinary to experience the wonders of the world at our feet.
Countless species of fauna and flora were recorded during this survey! These included ribbon worm, isopods, whelks, mud prawn, corrugated venus mollusc, crown crab, false limpets, true limpets, striped barnacle, spiny chiton, cape urchin, plum anemone, polychaete worms, crumb-of-bread sponge, ghost crab, eelgrass, arrow grass, sea lettuce, sea lavender…and the list goes on and on. It was a fascinating and rewarding experience to be a participant in the survey.
After about three years of ShoreSearch surveys, researchers and scientists involved in Knysna Basin Project hope to ascertain just what is living or washed up on the intertidal shores of the Knysna Estuary. How does it compare to previous studies and how has the system changed over the years? This data will help researchers and conservation organisations in their endeavours to protect and maintain the integrity of this celebrated natural asset.