I had to write a short article about Shark Spotters a while ago, for the quarterly magazine of the company I work for. It was fun to write within the constraints of quite a punitive word count, and to try and emphasise the aspects of the program that I think are poorly understood by the public. Here’s the article:
Shark Spotters developed into Cape Town’s primary shark safety strategy out of two similar, informal initiatives. At Muizenberg and Fish Hoek in 2004, surfers arranged with lifeguards, car guards and trek fishermen to warn them when sharks were sighted. Today, Shark Spotters is a NPO funded primarily by the City of Cape Town, Save Our Seas Foundation, and public donations. It operates year-round at four beaches and during summer at another four. These are beaches that have both many water users and relatively common shark sightings.
A team of 30 spotters equipped with binoculars, polarising sunglasses and all-weather gear watch from the mountainside, and when a shark is sighted they notify colleagues at the beach to sound a siren and raise the appropriate flag. The flags indicate the current or recent presence of a shark, that spotting conditions are poor, or that it is safe to swim.
The spotters, all drawn from local communities, are trained in safety, first aid and shark behaviour. A further 10 team members deploy and retrieve the shark exclusion net at Fish Hoek beach during summer. Unlike the gill nets protecting beaches in KwaZulu Natal, this net does not catch sharks. It provides a physical barrier between sharks and swimmers. It is designed to be retrieved at the end of the day, or, to prevent entanglement, when there are marine mammals nearby. The Fish Hoek shark exclusion net is unique worldwide as an environmentally friendly shark attack mitigation measure.
It is the combination of favourable topography and surface-swimming sharks that makes Shark Spotters’ work possible and effective. The land around many of Cape Town’s beaches slopes steeply towards the sea, providing raised vantage points from which to spot. The sharks which pose the primary danger to water users, because of their size and curious natures, are great white sharks. Fortunately these sharks spend much time swimming on the surface, and their distinctive swimming style is readily recognisable.
Shark Spotters also conducts research on sharks to improve safety measures and provide management and conservation recommendations. As a result, the movements of great white sharks in False Bay are well understood. Sharks visit the beaches year-round, but with a distinct seasonal pattern. During winter the sharks congregate at Seal Island to feed on juvenile seals. During summer, sharks head for the backline of Cape Town’s beaches – probably to feed on the fish species found in False Bay at this time, and to rest in the highly oxygenated water close to shore. This is when they pose the greatest risk to water users.
Why support Shark Spotters?
I love the fact that Shark Spotters combines care for people with concern for the environment. The program takes a scientific stance backed by research, and has attracted worldwide recognition. It also provides training and employment for 40 residents of some of Cape Town’s most impoverished communities. I sit on the non-executive committee as a representative of Cape Town’s scuba diving community, and it’s a privilege to work with fellow water users and ocean lovers, and hopefully to provide a benefit to the greater community through our small contribution.
(Of course, lately white shark movements in False Bay are slightly less well understood than they have been, probably thanks to a pair of orcas whose irregular visits to Seal Island and Millers Point to hunt white sharks and sevengills seem to clear out the neighbourhood a bit! Fear not, Shark Spotters’ research is aiming to understand these changes, too.)
The weekend forecast looks really spectacular… If you are a surfer. A nice six metre swell rolls in on a 15 second period, meaning the big wave surfers are busy waxing their boards as we speak.
I think that Friday, Saturday and Sunday should offer a few really good photo opportunities at Dungeons as well as Sunset Reef. The wind will be a factor so I will most likely launch on Friday and Sunday. Let me know if you want to hitch a ride.
After a successful Back a Buddy campaign, Shark Spotters launched their free shark safety smartphone app in the summer of 2016. The app has had excellent uptake by water users of all stripes, but I’d like to draw it to your attention in case you aren’t familiar with the ways in which it can make your beach life better and safer! Whether you’re a surfer, a diver, an ocean swimmer, a beach comber, or someone who looks forward to long summer days under an umbrella on the sand, the Shark Spotters app can make a difference to you.
The list of Shark Spotters beaches
Shark Spotters operate at eight beaches around the Cape Peninsula: four (Muizenberg, St James/Kalk Bay, Fish Hoek & Caves, Kogel Bay) year-round, and another four (Glencairn, Clovelly, Monwabisi and the Hoek, Noordhoek) from October to April, during the warmer months.
The app allows one to set a home beach – you can see from the image above that mine is Fish Hoek – and when you start the app, you’ll get information for your home beach immediately. Tapping on the home beach block at the top of the screen (where it says “Tap for more”) brings one to a series of screens that you can navigate through by swiping the bottom block on the screen.
Information on recent sightings at my home beach
Weather and sea conditions
Information on marine life activity
Information on beach facilities
Beach conditions video
Shark sightings history
The information provided is extensive. You can see information on the last three shark sightings at your home beach, the weather and sea conditions (temperature, wind direction, tides, moon phase, swell), and information on what marine life is in the area. This latter information is not a nice to have so you can look out for dolphins from shore, but an important indicator of the likelihood of a shark being in the area. Dolphins, rays and schools of fish can draw white sharks, while sunfish (and even seals) may be mistaken for a shark when viewed from a distance by an untrained observer.
There’s also information on what facilities are available at the beach, and a short video for each beach, usually taken each morning, showing the prevailing conditions.
All this information is available for all the Shark Spotters beaches, not just your home beach, and you can view a different beach by selecting it from the list that appears under your home beach on the home screen.
Digging into the app, you can find a detailed list of all the recorded shark sightings, and in the settings you can turn notifications of sightings on or off according to your preference. I have them switched on, because I like to be reminded of a world outside the office.
Shark Spotters app menu options
The further menu options, shown above, give you access to a large amount of data about the Shark Spotters program, the exclusion net at Fish Hoek beach, how the flag system works, great white sharks, and more. Most of the menu options also provide links to more detailed information online, if you want to know more.
False Bay has been magical all week with exceptional visibility. The weekend looks a little iffy. The first real winter swell arrives tonight: the forecast says around 8 metres at 16 seconds. It thunders through tomorrow, meaning that Dungeons will be cooking… For the brave and top-class surfers. It tapers off during the weekend but Saturday’s wind is forecast to be around 50 km/h. Sunday’s wind is a lot less, however still more than our size boat is suitable for. Sadly a dry weekend for us.
Autumn is a good time for False Bay diving! False Bay is currently pleasant, not too cold and the weekend does look decent after the latest weather updates. My plan is shore dives on Saturday, when it will be a little more windy, and boat diving on Sunday. Let me know if you’d like to get in the water.
Spring low tide at Muizenberg
Shark Spotters binocular fundraiser
Don’t forget to donate to the Shark Spotters crowd funding campaign to raise funds for new high powered binoculars for the spotters. Shark Spotters does fantastic work – read more about it here and here. You should also make sure you download their very cool shark safety and beach information app – available for both Android and iOS.
Capetonians are familiar with the tea-coloured water that runs in our mountain streams. Most people know that the brown colour comes from tannins, leached naturally from the indigenous fynbos vegetation. Perhaps less well known is the reason for the brown water that is sometimes seen in the surf zone along Muizenberg beach, stretching all the way to Strandfontein, Monwabisi and beyond.
Tea-coloured water at Muizenberg
The most frequent explanations that are offered on social media are, of course, pollution, “raw sewage”, and the like. This is not the reason for the brown water, and it does not necessarily impact the water’s safety or healthfulness for humans to swim in.
Like False Bay’s famous colour fronts, the reason for the brown waves at Muizenberg beach turns out to have much to do with the topography of False Bay, particularly of the kilometres-long beach at its head (Muizenberg-Strandfontein-Macassar-Monwabisi), and something called a diatom.
View of Muizenberg showing patches of brown water
Diatoms
Diatoms are a type of phytoplankton (plant plankton or microalgae). They are single celled, usually symmetrically shaped organisms that multiply by dividing in half at a constant rate. Their cell walls are made of silica, SiO2. Chicken keepers and gardeners may be familiar with diatomaceous earth – this is made up of the fossilised shells of ancient diatoms.
Diatoms are what are called primary producers or autotrophs, meaning that they generate organic material from carbon dioxide and other inorganic nutrients (for example nitrates and phosphates), through the process of photosynthesis, which uses light as an energy source. Primary producers sit at the base of the food chain and all life relies on them, directly or indirectly. Everything else produces organic material from other organic material (such as diatoms).
I am telling you all about diatoms because the brown water at Muizenberg contains an accumulation of a diatom that you can call Anaulus australis Drebes et Schultz the first time you mention it, but usually just Anaulus australis, or Anaulus for short. There are several members of the genus Anaulus, but usually just one tends to be dominant at each beach where these accumulations occur, and Anaulus australis is the main species found along the South African coast.
Analaus are pillow-shaped diatoms. If you wanted to see what an individual Anaulus diatom looked like, you’d use a microscope, but when enough of them are in one place, they can be seen to change the colour of the water. There’s a picture of them under a microscope at the bottom of this webpage (they also occur in Brazil). They occur at beaches with particular topograhical characteristics, which explains why you haven’t seen them at Camps Bay, Kogel Bay, or Scarborough.
At hospitable beaches, the diatoms are always there, spending much of the time lying dormant in the sand behind the surf zone. A proportion of the diatom population is able to survive for relatively long periods (estimated to be more than two months) like this, in the dark on the seabed, not photosynthesising or dividing, until the correct meteorological conditions arise for an accumulation. But first – what sorts of beaches are hospitable to Anaulus?
a nutrient source close to the surf zone (often an unconfined aquifer overlaid by a dune field)
Muizenberg and Strandfontein beach tick all these boxes. The beach stretches from Surfers Corner all the way across the top of False Bay to Monwabisi, a distance of over 20 kilometres. It is a high energy beach, meaning that it is exposed to large waves and strong winds, and is not protected by any offshore features such as sandbars or headlands that might reduce the force of the waves. Rip currents do occur at the beach, and both these and the exceptionally wide surf zone – wider during south easterly winds in summer – can be observed from the mountainside on Boyes Drive. (A rip current is like a hidden river flowing out to sea from the beach. The Sydney Morning Herald has an excellent visual explainer of rip currents here.)
The head of False Bay where Muizenberg is situated is incredibly nutrient-rich, much of it thanks to urbanisation. The canalised Zandvlei estuary – the only vaguely functional one on False Bay’s coast – is situated a short distance down the beach, and supplies nitrates, phosphates and other nutrients to the surf zone. Many of these nutrients are technically pollutants, added to the river further upstream. The Cape Flats Waste Water Treatment plant at Strandfontein also discharges 200 million litres of treated water per day (under normal, non-drought circumstances) via a canal onto Strandfontein beach. This is essentially an artificial estuary for Zeekoevlei. This waste water has spent some time working its way through the settlement ponds at Strandfontein, but is nevertheless rich in ammonia and other nutrients, and Anaulus accumulations are a very common sight in the surf around this discharge point. The dunes that run along Baden Powell drive overlay a high water table, and groundwater seepage – specially during times of heavy rainfall – may also leach nutrients out of the ground and into the surf zone.
Meteorological conditions
The meteorological conditions required for an Anaulus accumulation involve strong wind and a large swell. These act together to create rough sea conditions, which stir up the dormant diatoms from the ocean floor. The diatoms adhere to air bubbles in the surf zone, staying suspended in the water column, which is when you would notice the water turning brown. Exposed to light, they awaken from their dormant state and start to photosynthesise, take up nutrients, divide and multiply. The presence of rip currents creates an onshore-offshore flow all along the beach. This forms a semi-closed ecosystem, and the diatoms are essentially trapped in gyres in the waves. Longshore currents that run parallel to the beach transport Anaulus cells out of the surf zone at one end, and bring fresh (sea)water in at the other end of the beach.
It may seem surprising that anything manages to accumulate in the waves of a beach, but the surf zone is actually quite retentive, meaning that things that end up there often tend to stay there. (Incidentally, this is why it’s a terrible idea to discharge the byproduct of reverse osmosis seawater desalination – a super-salty brine – into the surf zone. It must be discharged offshore so that it can disperse and mix with the surrounding water.)
Diatoms in the surf zone at Muizenberg
You’ll notice that, contrary to what you may have seen when large amounts of plankton are under discussion, I’ve been using the word “accumulation” instead of “bloom” to talk about Anaulus. This is deliberate, because of the constant presence and constant rate of division of the diatoms. When the water goes brown, it doesn’t mean that Anaulus is suddenly multiplying faster than usual. It means that it’s all been gathered together in patches, is exposed to light and therefore photosynthesising (at its usual steady rate), and is thus more visible than it was when it was lying on the ocean floor.
Anaulus at Muizenberg in November 2017
The human factor
You may also be thinking that everything I’ve said about the nutrients that Anaulus requires to survive and thrive points to the fact that humans – and pollution – are ultimately responsible for these brown-water plankton accumulations at Muizenberg. Well yes, in a way. But accumulations of Anaulus australis and related species have been observed and documented for well over 100 years at suitable beaches around the world, and are a natural phenomenon.
Yes, we are providing more nutrients to the False Bay diatom population than they would otherwise have received without human settlement in the greater Cape Town area, but these accumulations would likely occur regardless. They are certainly more intense now than they would have been in the past, but estuaries are nutrient-rich locations even when not surrounded by a large city. Furthermore, the water table is high on the Cape Flats, which would supply nutrients to the surf zone regardless of whether humans lived nearby.
Anaulus is in fact performing a vital and useful function by mopping up the excess nutrients that the city discharges in the ocean. The mass of diatoms – primary producers – also provides a food source to bivalves such as mussels, and other invertebrates. We can be grateful that the excess nutrients that urbanisation directs towards the ocean at the head of False Bay leads only to accumulations of harmless diatoms, rather than to frequent occurrences of harmful algal blooms that can kill marine life and exacerbate respiratory problems in humans.
Muizenberg during a diatom aggregation
Sources
Most of the original scientific study on surf zone diatoms in South Africa was done by a group of researchers (primarily M Talbot, Eileen Campbell and Guy Bate) from the University of Port Elizabeth, working at the Sundays River Beach in the Eastern Cape. I did quite a bit of reading to research this post, but you can start with this paper for a description of the topographical characteristics of beaches where surf zone diatoms accumulate. The first few chapters of this Masters thesis also provide a good overall survey of what is known about surf zone diatoms.
Putting knowledge into practice
Not every instance of brown, foamy water at the beach will be an Anaulus accumulation. On the west coast of South Africa, for example, there are no beaches where Anaulus occurs, but you may see brownish foam that is the result of heavy wave action frothing up organic matter in the surf (nothing sinister – there is a lot of organic material in the ocean). A clue to help you distinguish diatom accumulations from other brown-water phenomena – apart from running through the checklist of required beach characteristics above – is that an Anaulus accumulation doesn’t stretch much beyond the back of the surf zone. If the brown water stretches beyond the furthest row of waves, it’s probably something else. (And this seems like an apposite time to remind you that sewage looks whitish-grey, not brown, when it’s pumped out into the ocean.)
The number of beaches worldwide where surf zone diatom accumulations occur is so small – less than 100 – that Odebrecht et al could enumerate them in a 2013 paper. I hope this helps to convince you that the brown water at Muizenberg beach (and beyond) is something special and interesting, not to be feared. Go surfing!
Life’s a Beach: Your Round-The-Coast Guide To South African Beaches – Ann Gadd
Compliments of the season. If you’re contemplating which beach to head to for tomorrow’s traditional Boxing Day beach outing, a venerable South African institution, I have just the book for you. The product of a mammoth investment of time (which couldn’t have been all bad) and distance travelled, Life’s a Beach is a handy guide to (possibly, probably, almost) every single beach along South Africa’s coastline.
Life’s a Beach
Each pair of facing pages covers a stretch of coast, and beaches are rated for surfing, alongside information about swimming, kiteboarding, wake boarding, kayaking and canoeing, diving, fishing and hiking. The scuba diving information for the sites around the Cape Peninsula, with which I am familiar, is reasonable, but of necessity very abbreviated owing to the book’s format and primary focus. It goes without saying that you should seek out some local knowledge before diving in an area you haven’t visited before.
Unique experiences and best kept secrets (no longer – haha!) are highlighted, as well as the presence of braai and picnic facilities. Tips on where to go for sundowners are also included. Child friendly activities are mentioned where applicable, too.
Access tips, as well as warnings about rips, pollution, sharks (thank you Shark Spotters!) and whether a beach has Blue Flag status round off the comprehensive information that is provided in a handily concise manner. This book will be extremely useful when you’re visiting an unfamiliar stretch of South Africa’s coastline, and particularly invaluable when it’s a little known and less popular beach.
Get a copy of the book here, or here if you’re outside South Africa.
I wondered when I’d need a picture of a glass of champagne next to some dive gear; this post feels like as good a time as any to use it. I feel obligated to explain that the champagne was being consumed on our pool deck during the course of a late afternoon fool around in and next to the pool with some of my friends. The dive gear was still lying there from a class Tony had led that morning. The juxtaposition was too much to resist.
Don’t drink and dive
That said, it’s time to think about Christmas, Hanukkah, and time off with the family. Some may even celebrate Festivus. I salute you. Regardless, it’s a good time to give gifts to the people you care about. Some suggestions follow below.
First, here are the obligatory links to previous years’ editions of this guide: 2010, 2011, 2012, 2013, 2014, 2015. Unfortunately, 2016 was an annus horribilis best left undiscussed. As usual, this year’s guide owes much to previous versions. There’s nothing new under the sun.
Donations
For the person who has everything, or because you’re feeling grateful, consider a donation on behalf of your friend or loved one:
As usual our Wild Card was an absolute blessing this year. It has been used for multiple park visits and also gets us a discount on our toll fee on Chapmans Peak Drive‘s frequent user program. The full card is a bit pricey, but there’s a great alternative called My Green Card, that costs R145 and gives twelve entries to any of the paid sections of Table Mountain National Park (so, Cape Point, Boulders, Silvermine, Oudekraal, and a few braai areas). Read the fine print carefully though – if you use it up quickly, you have to wait for the 12 months to pass before you can purchase another one. But I think you can also share the 12 clips with friends, whereas a regular Wild Card is tied to your identity. You will have to go to the SANParks office in Tokai to get a My Green Card.
SanParks is introducing differential pricing for Table Mountain National Park, with significantly lower prices for locals, starting next November, so some mathematics will be required this time next year to determine whether a Wild Card is still worth the expense.
Something to read
Everything you need to know about finding a book related to the ocean can be discovered in our list of most recommended books, and our guide to finding the book you need (on this blog, at least!). There are a couple of children’s books there, too.
A magazine subscription is also a fairly reasonably-priced gift idea. I can’t tell you which of the dive magazines are worth reading these days – our current subscriptions are Maritime Review (which is free, so that’s perhaps cheating) and CAR magazine…
Something beautiful
Clip Clop designs and prints beautiful tide charts for Cape Town and Durban and moon phase charts for the year. You can order online or usually find them at Exclusive Books or Noordhoek Farm Village (just browse the shops there, one of them has the tide charts right at the door).
You could also print and frame a photo, or create a photo book. Most camera stores can assist with a range of printing media.
Dive gear and water-related stuff
Some excellent water-related gifts I’ve received over the years include:
A reusable metal water bottle (glass is a bad idea for the boat)
A mini dry bag to keep phones and keys safe
A beanie for cold days on the boat or a cap for the sun, or a buff for hair management or neck protection (the Aquarium sometimes sells turtle ones to fundraise for their turtle rehab)
Be safe, be kind, be lekker. Thank you for your friendship and for the dives!
False Bay has been on and off this week. The swell is not wicked but it’s there and noticeable. The weekend does not look terrible, but we will leave the choice of diving or not up to you… We are heading north in search of warmer water. We are back in town next week Friday and will be ready to dive.
A recurring but seemingly never-resolved question that intrigues shark researchers and management entities is that of whether there exists a reliable, non-lethal shark repellent.
Such a shark repellent would solve all manner of management problems: organisations like Shark Spotters exist partly to navigate that tense, thin line between sharks killing people and people killing sharks.
Furthermore, there would be a significant financial payoff associated with a successful patent of such a product. (I do not mean to suggest that this is the primary motivation for doing this kind of research, but untested, untestable products like this cannot possibly be marketed with anything else in mind.)
Life-size model of a white shark
There are several ideas that have been either proposed, tested, or marketed. The SharkShield has been tested (not just by us), with mixed results. A shark repellent wetsuit has certainly been well publicised (there’s even a TED Talk), but, like medicines for pregnant women, I can’t see how it can be properly, ethically tested in order to state with some degree of certainty, in a statistical sense, that it works. The test described here has N=2, and there wasn’t a human in the suit.
I digress. Outside Online has an interesting article this month about the efforts by Eric Stroud, a pharmaceutical consultant, who – after much experimentation – settled on several compounds found in decaying shark flesh, which seem to work well as a repellent of about 30 species of mostly coastal sharks. The compound can also be synthesised, although the real thing, from a dead shark, apparently works better. Stroud’s financial backers travelled to Mossel Bay to visit Oceans Research, a multi-disciplinary research organisation with several shark scientists on its staff, to test the chemical on great white sharks. The article provides an overview of the history of shark repellent technology, and brings us up to date with this new chemical alternative. It’s early days…
Read the full article here. And remember, kids, that while the only thing that will keep you completely safe from a shark is not going into the sea at all, there are a bunch of simple, sensible things you can do to reduce your chances of meeting a man in a grey suit. Do them!
