It’s Saturday morning and all that’s on my mind are the weather reports that are going around Cape Town. Every dive shop in the area is telling the tale of the Doctor, upwelling, water temperature and visibility. The stuff that matters to our kind of people.
It’s time to head out for a dive because conditions look amazing. We will be having some flat Atlantic waters with 10 degree temperature. Yes – 10 degrees. And, yes, we are more excited for this dive than we are for the finale of ‘The Walking Dead’!
So, why do we do it? What makes us so excited to go exploring in this harsh environment? With waters constantly below 18 degrees and a constant green colouration, some would say that we’re suckers for punishment. But that’s because they haven’t experienced what this awesome biome has to offer.
Various different factors play a part in what make Cape Town’s diving so special – each of which deserve a fair amount of exploration. However, in this post we will discuss specifically why temperate waters, such as those found in Cape Town, are of such advantage to divers!
While most of the world has its seasons due to the earth’s spin axis being tilted with respect to its orbital plane, the tropics experience a much more constant climate. This climate is a warm one – caused by the angle at which the sun’s rays make contact with this surface area. Thus, these waters are constantly warm and usually have very little distinction between summer, winter, autumn and spring.
Temperate waters, on the other hand, are found further away from the equator and closer to the poles. These waters are much cooler due to the reduced concentration of sun rays that manage to reach and penetrate the surface of the ocean.
Temperate Water and Nutrients
Temperate waters, such as those found in the Cape Peninsula and False Bay, have much better productivity than waters found in tropical areas such as Sodwana or Mozambique. The crystal clear (but nutrient poor) tropical waters may offer calm conditions – however their carrying capacity is nothing compared to the temperate waters found down the coast.
So, why are tropical areas known for offering great visibility? This question is easily answered by considering the nutrients mentioned in the above paragraph with the aid of the following experiment: if you were to take two clear containers and fill one with temperate and the other with tropical water, and then hold them up towards the sun, you will notice that tropical water has much fewer particles floating around in it. While this makes for amazing visibility, it limits the amount of underwater life that these reefs can support. This is because these small particles are nutrients, which are essential for life.
When diving the Cape waters you will find that, no matter what time of the year you go for a dive, the water will always have a tinge of green in it. This is in fact not a bad thing, because the tinge is caused by plankton. The reason behind temperate waters having such a high productivity is thanks to these microscopic organisms that give the water its green colour.
Whales, Dolphins, Seals and Sharks
All of these animals are found in temperate waters because of one main reason: plankton. Smaller fish, such as Galjoen & Hottentot, are plentiful in False Bay due to the fact that these fish predate on smaller sessile and benthic invertebrates. These invertebrates thrive on the plankton – and in return the populations of the smaller fish that feed on them also grow to large numbers.
All of this plankton business is obviously essential for animals higher up on the food chain. Dolphins, seals and some sharks are attracted by the large amounts of smaller fish, while whales are attracted to the plankton itself. Sharks such as the Great White are attracted to False Bay and the Cape Peninsula largely because of the seal colonies which provide an excellent food source. In this way, the ‘green tinge’ in the water is actually an indication of a complex food chain – one which allows this vast variety of life below the surface!
So – if one looks at this massive carrying capacity, containing everything from the bottom of the food chain all the way up to apex predators such as Great Whites, you can’t help but appreciate what a special place False Bay and the Cape Peninsula is. So do yourself a favour, grab a good wet suit and go exploring – there’s an incredibly high chance that some species which has never been discovered will be right there in front of you! Go diving in colder water!