Tsitsikamma Rivers Project – quest to understand and conserve our rivers

by | Jul 8, 2012 | 2012 | 0 comments

Speaker:   Geoff McIlleron                    

The Tsitsikamma Rivers Project, launched in 2008, is a quest to understand and conserve the river systems of the Tsitsikamma mountains which are valuable natural assets of this area. 

In many parts of our country the river systems are in a parlous state, to the extent that some are dubbed the ‘sewers of South Africa’. Some rivers are already dead, others are endangered. Even in our area, rivers are polluted. For example the children of the primary school in Kurland Village are involved in a clean-up project, organised by the Nature’s Valley Trust, in which they regularly relieve their river of tons of rubbish. 

The Tsitsikamma Rivers project, a large research project, was – in a roundabout way – set in motion by a gentleman making application to establish a trout farm in the Salt River area, which in turn prompted Cape Nature to investigate the ecology of the river. The Trout Farm application was unsuccessful because of the findings of the research consultants who reported a remarkably rich diversity of aquatic insects in the river. 

The project of today’s presentation was initiated and coordinated by Nature’s Valley Trust and funded by Table Mountain Fund which is linked to World Wildlife Fund. The research teams were drawn from the Department of Water Affairs, Albany Museum and the Universities of Rhodes and Stellenbosch. SANParks and Table Mountain Fund played a constructive supportive role in formulating and supporting the project. 

The eleven rivers studied range from the Matjies in the west to the Groot Rivier which lies east of Storms River. These are short rivers, typically 15 km, rising in the Tsitsikamma Mountains. These fynbos covered sandstone mountains with their numerous gorges determine the nature of the rivers which are cold, fast-flowing, well oxygenated waters with little sediment. These rivers are acidic and of a red-brown colour, due to the presence of humic acid.  Despite the colour, the water is potable, and probably of the finest quality in the country. 

The first phase of this project was completed last year and involved the study of the aquatic insect population located in the 11 rivers running from West to, are: Matjies, Buffels, Salt, Groot (W), Bobbejaans, Bloukrans, Lottering, Elandsbos, Storms, Elands, Groot (E).  Importantly the degree of presence and diversity of the insect species in their various habitats is a reliable indicator to the health of a river and therefore its conservation worthiness. 

Future phases of the project will focus on how best to implement the stewardship of these beautiful waters. 

It was found that the upper reaches of two of the rivers were completely inaccessible by humans on foot, affording perfect protection of the ecosystem. Helicopters were used to gain access to these rivers. 

The research teams collected insects by a variety of sampling techniques which included special daytime flight traps, ultra violet light traps for night flying insects and hand nets for both larvae in the river and flying adults in the air. Samples of both larvae and flying insects were identified by scientists at Albany Museum and, in some instances referred to specialist organisations locally and overseas.  It was found that, while some insects are common to all of the rivers, many are specific to their own river systems. It was also found that the upper reaches of the rivers were markedly different in species composition from the lower reaches and usually contained a greater diversity of species. Thirty-four species and four genera new to science were identified within known families.  

The insects have many remarkable behavioural characteristics: the caddisfly larvae, for instance, protect themselves from predation within cases made with silken threads which bind together particles of sand, leaves and plant stems, each species having its own specialist design. As with hermit crabs in the sea, there is competition for good homes and one species will often take over suitable cases from another and certain of them add a distinctive canopy over its head.  Once airborne, the caddisflies become superb flyers, sometimes tinted blue or green by the light and some with golden-coloured wings. Often an abundant egg mass hangs from the abdomen of an adult female caddisfly’s abdomen, which it then disperses into the river by dipping its tail into the water. Forty-eight species of caddisflies were identified. 

Mayflies are quite a primitive insect life form – the nymphs (larvae) have external gills which serve as lungs; again there are a number of different species. 

The study of the dragonflies showed that they too had developed species exclusive to certain river habitat types. Blackfly larvae were seen to use silk ‘hooks’ on their tails which they used to anchor themselves to rocks while they filtered food particles from the flowing water. The species are specialised according to the different speed of the river flow, some even showing preference for the faster flow of waterfalls. Different species, which specialise on using different water flow rates are sometimes found very close to one other – as little two metres apart where there is variation in the rate of water flow. 

Species are sometimes found very close to one other – as little two metres apart where there is variation in the rate of water flow. 

Altogether over 70 000 insect samples were collected, all ßof them being scrutinised by zoologists in minute detail for identification, mostly under a microscope,. One of the species new to science was discovered by scientists from studying photographs taken on location.  

One enthusiastic researcher spotted a water snake (hitherto unknown in these waters) and dived in, but failed to catch it.  These snakes live under the water, coming up periodically for air. They are thought to be harmless to humans. 

For capturing high quality photographs a rig was constructed which triggered a photograph when a pair of infra-red beams was broken by an insect crossing the beams. Ultra-violet lamps were used to attract the night flying insects to the vicinity of the infra red beams. Geoff used a variety of photographic techniques to capture the adult insects in free flight. These included single photographs taken by high speed flash at 1/4000 second. These pictures did much to elucidate flight mechanics of the insects. He also used a strobe mode from which it was possible to work out the speed of their flight and to observe their flight patterns. Further techniques using continuous light in conjunction with flash revealed more information about flight behaviour. For example photographs depicting loop-the-loop and a predilection for flying upside down. 

The findings of the completed Phase One of the Tsitsikamma Rivers Project are significant: there is a clear distinction between the rivers with respect to their insect assemblages and a surprisingly high level of diversity for a comparatively small region was noted. Most of the ‘new’ and endemic species were to be found in the upper reaches of the rivers which are fortunately afforded the protection of the Tsitsikamma National Park . In three rivers there were no fish, which is an important factor contributing to the rich diversity of aquatic insect life.  Some of the ‘new’ species originate from the Jurassic Period – 140 to 200 million years ago: the time of dinosaurs and Gondwanaland. Unfortunately, it is a lengthy process to have the ‘new’ species formally recognised. 

The Project has underlined the fantastic richness of our insect life – even by international standards. Unfortunately, it is a lengthy process to have the ‘new’ species officially recognised. 

There is concern that damage to the ecosystems may be caused by pollution e.g. the addition of phosphorus and nitrogen from commercial agriculture and sewerage treatment plants.  A further threat is implied where there is excessive withdrawal of water from the rivers which may result in an increase of the water temperature and pH.  The well-being, indeed survival, of the insect life is dependent upon cool, acidic waters. 

It is planned that the Project should  continue with further research work and, most importantly by implementing stewardship measures. The next steps still need to be clarified in detail and followed by action. Our natural assets must be safeguarded: the future of our region depends upon it. The next steps need to be clarified, followed by action. 

All the players were deserving of recognition and praise for a project well executed. In addition to the central research scientists, the important contribution of the Department of Water Affairs in providing a generous number of researchers requires recognition. 

In conclusion a quote from America’s Barbara Kingsolver: ‘Water is life, it is the briny broth of our origins, the founding circulatory systems of the world, the precarious molecular edge on which we survive.’

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