Profile photo of James

by James

Shark attacks in South Africa

November 4, 2015 in Uncategorized

Do shark attacks make South Africa the most dangerous place in the world to surf? 

South Africa is home to many species of shark including the tiger shark (Galeocerdo cuvier) and the hammerhead shark (Sphyrnidae) but is most notably home to a large number of the great white shark (Carcharodon carcharias) population. South Africa is also home to some of the best surfing locations in the world including Jeffrey’s bay, where an annual surfing competition is held. So why are shark attacks so common in South Africa?

The great white shark is responsible for the majority of shark attacks in South Africa, accounting for 5 of the 6 shark attacks recorded in South Africa this year alone ( Although there have been no fatalities recorded so far this year the great white shark is reportedly responsible for 13 fatalities between 1998 and 2012 (international Shark Attack File Florida Museum of Natural History, University of Florida). Although the great white shark is reportedly responsible for most shark attacks in South Africa the tiger shark and the bull shark (Carcharhinus leucas) are also responsible for many attacks.

There are many attacks each year from sharks in South Africa, these attacks are generally due to mistaken Identity as the underside of a surfboard appears like the belly of a seal or a turtle, the main source of food for great whites and other sharks. Sharks are an ambush predator and there are 3 main types of unprovoked attack. The first, and most common, type of attack is the hit and run attack. The hit and run attack occurs more frequently as it is mainly due to mistaken identity from the shark and often results in the shark swimming away after the initial attack as it has realized it is not its usual prey. The sneak attack often occurs in the surf zone where the shark can easily misidentify human surfers as prey. The second type of shark attack is the sneak attack, this often occurs due to mistaken identity as the shark attacks its mistaken prey from underneath, often leaving fatal wounds on the victim. The third type of shark attack is the bump and bite attack. This is where the shark will bump the victim before biting, the result from these kind of attacks are often fatal. Bump and bite attacks are the only type of unprovoked shark attack that is not believed to be a result of mistaken identity. ( “ISAF Statistics on Attacking Species of Shark”)

Due to the shape of surfers from beneath the water and the numerous seal colonies located around South Africa there is no surprise that so many attacks on surfers occur. As sharks have no limbs with hands or feet to explore what an unidentified animal is, they rely on their bite to give them a sense of what animal is in front of them. The shark will often swim away if the animal is not recognized, such as a human, as they use their mouth to sense things. Many surfers are therefore subject to attacks by sharks as they are often mistaken for seals and the shark will often swim away straight away when it realizes the human is not a seal. ( Grabianowski, Ed. “HowStuffWorks “How Shark Attacks Work) ( “What To Expect On Your Great White Shark Diving Tour”. 


A diagram illustrating the shark attacks that have occurred between 1913 and 2011.


Mick Fanning being attacked by a suspected great white shark during the surfing championships in June 2015


An example of a recent shark attack was during the world surfing championships in Jeffreys Bay in South Africa on June 19th 2015, where competetor Mick Fanning was attackad by a suspected great white shark 2 minutes in to the final of the competition, the first time a shark attack has been recorded on live tv. Fanning sustained no injuries but the attack provides a perfect example of the dangers of surfing on the South African coast. With surfing beaches located across the whole south coast of South Africa there is a huge area for potential unprovoked shark attacks to occur making it hard for every beach in South Africa to be monitored for shark activity.

The most dangerous beach in South Africa is port St John’s where every shark attack since January 2007 has resulted in a death unlike the average shark attack mortality for South Africa standing at 1 in 5. This makes port St Johns a beach that needs to be monitored hea
vily in order to prevent further fatalities from shark attacks. ( Shark attacks can be prevented by having several “spotters” at beaches well known for shark attacks like port St Johns that can alert swimmers if a shark is spotted in the area and an alarm can be sounded to make sure everyone in the water knows of the sharks presence in the area. Another effective method of monitoring shark activity is by tagging captured sharks and monitoring where they travel to, this can also help establish migration patterns amongst shark populations as well as helping to keep people safe in the water around the coast of South Africa.

Overall, although South Africa doesn’t have the highest number of shark attacks recorded in the world it is amongst the top for fatalities recorded making it one of the most dangerous places to surf as well as carry out other water sporting activities around the coast of South Africa. 

Profile photo of Tomas

by Tomas

Symbiotic Relations Between Coral and Zooxanthallae and the Bleaching Effect

October 22, 2015 in Uncategorized

Coral and Zooxanthallae

Coral (in the class Antrozoa) is a vital part of many aquatic ecosystems, with it’s ability to form large calcium carbonate structures over time which act as a habitat for many different organisms, it plays an important role in it’s ecosystem. A coral reef will consist of many small polyps which surround themselves in a calcium carbonate skeleton in order to protect themselves from predators which will visit the reef. The polyps typically emerge overnight to feed.

Coral polyps feed by catching zooplankton and other microscopic organisms with their tentacles and directing them towards their mouth parts where the zooplankton will be digested in the stomach. They can occasionally also eat slightly larger prey by incapacitating or killing it with their nematocysts before it enters the mouth part. This however is only able to provide around 50% of each coral polyp’s daily requirements the rest it must source from elsewhere.

To ensure their full daily requirements are met coral polyps form a symbiotic relationship with called a group of single celled protozoa called zooxanthallae. The polyp provides the zooxanthallae with a suitable habitat within its soft tissues where it is protected from harsh abiotic factors and filter feeding organisms that would eat the zooxanthallae and the coral itself benefits from oxygen and nutrients expelled by the zooxanthallae.

What is Bleaching?

Bleaching a the process by which coral polyps remove the zooxanthallae when abiotic factors around the polyps are no longer capable of maintaining the populations of zooxanthalae causing the populations to decrease. In response to this the coral polyps expel the zooxanthallae from their soft tissues and into the water column. This is known as bleaching because the individual coral polyps appear white in colour after this as pigments present in their soft tissues where specific to the zooxanthallae and therefore left with the zooxanthallae. The loss of zooxanthallae is detrimental to the health of the coral as it now lacks the means to produce enough nutrients to sustain itself; after a relatively short period of time if the environmental stresses which lead to the expulsion of zooxanthallae do not cease the coral will die.

Why Does Bleaching Occur?

The reason why coral undergoes bleaching when subjected to environmental stresses is not yet discovered, however it was suggested to be a defence mechanism by R. Buddemeier and D. Fautin in 1993 who hypothesised that when coral undergoes bleaching it will enter a state of reduced activity and wait for a new species of zooxanthallae to arrive which is better adapted to live in the new conditions. When the new species of zooxanthallae is found it will be introduced to the soft tissue of the individual polyps and they will continue to function as usual, the benfit of this system to the coral is in future it will be more resistant if conditions were to change further.


Zooxanthallae visible on coral polyps