When Rivers Meet Oceans

Posted on 23 Mar 2018

When the author was in the drought-stricken Southern Cape recently, a question by a beach-goer could not escape his thoughts. “Why do they let perfectly fresh water just flow into the sea like that?”, she asked.  One can look at it from the point of view that we, as people, need the water.  Many misinformed ideas spring into people’s minds, like “What impact will walling up the river at its mouth have on the sea? It’s full enough as it is” or the “creatures in the ocean don’t need freshwater, anyway”.

The great reality of this question (as so many others in nature) is that the very delicate, yet vulnerable balance of life is kept intact by interconnected processes. While some may differ, almost every river mouth can be regarded as an ‘estuary’.

It’s fascinating how, when scientists give interesting words for something that can be described simply as a “lagoon” or “river mouth” (depending on the type of estuary), people tend to think it must be something important.  Then again – perhaps that’s why we do it.  Not to get too far from the point:  Estuaries are special places.  They are thought to produce more organic matter than any other habitat on earth (relevant to size) and they are often the homes of species of fish and other marine (or semi-marine) life that can be found nowhere else.

Above:  The Gwaing estuary near George

You see, it’s because estuaries are a type of ecotone – a transitional zone between different habitats (another interesting word to emphasise how important these places are).  An example of an ecotone species specific to only three (though, some say only two) estuaries in South Africa, is the beautiful Knysna Seahorse.  Found at Swartvlei (outside of Sedgefield in the Western Cape), in the Knysna lagoon (in much smaller numbers) and occasionally in the Keurbooms estuary just outside of Plettenberg Bay.

 

Above:  The Noetzie River making its way to the sea near Knysna

We’ll survive the drought we’re currently facing.  We survive wars, poverty and so many dreadful things as human beings – we are resilient and strong.  But we should never sacrifice something as special as our sensitive ecosystems, estuaries included, to satisfy short-term needs or greed.  Our environment contributes to our overall “sense of place” and therefore toward our well-being.

One can go into much more detail about estuaries, but that is not the intention of this article.  This is simply a message to those willing to read:  Ask questions.  Think about the future. Don’t take what you see for granted – it’s apparent potential to exploit may not be worth as much as its long-term value to maintain the balance of life.

Above: The Knysna Seahorse – only found in three estuaries in the country