Echinoderms

City of Cape Town’s new protocol for cleaning tidal pools

Early in November I attended an information session at the Kalk Bay Community Centre, where the City of Cape Town announced that they will be trialling an environmentally friendly cleaning process on five of the 19 tidal pools on the 260 kilometres of Cape Town’s coastline managed by the City. This coast stretches from Silwerstroom on the West Coast to Kogel Bay on the eastern shores of False Bay.

The presentation was made by team members from the City’s Recreation and Parks department, which – among other things – is responsible for beaches, outdoor signage, ablutions, lifesaving, environmental education, and administration of Blue Flag status for the beaches and marinas that earn it. This department is also responsible for the tidal pools. (Incidentally the City’s assortment of safe seawater bathing facilities includes two of the largest tidal pools in the southern hemisphere, at Monwabisi and Strand.)

Until now, the City would use chlorine to clean the walls (top and sides) and steps in the tidal pools. The cleaning would be done after draining the pool completely. This year, a supply chain management issue meant that there was no cleaning of the tidal pools between July and November. During this time, regular swimmers (some of them members of the Sea-Change project) noticed that marine life flourished in the pools, and engaged with the City to try to find a way to keep the tidal pools safe but also to preserve the diversity of marine species that had been thriving in the pools during the cleaning hiatus. Safety, of course, is why they are cleaned: slippery, algae-covered steps are dangerous.

It was agreed that five of the pools – St James, Dalebrook, Wooley’s Pool, and the two pools at Kalk Bay station – would be subject to a trial of a new, environmentally friendly cleaning regimen. These pools are relatively close together in the north western corner of False Bay. The aim is still to ensure that the tops of the pool’s walls and steps are not slippery, and thus safe for bathers. But a second aim has been added by the City, which is to ensure the environmental integrity of the pools.

Under the new cleaning protocol, the following will be done:

the pools will be drained only when necessary, and only as far as is required to reach areas that are covered by water and in need of cleaning (for example, the steps at Dalebrook)
animals in harm’s way will be relocated
excess kelp and sea urchins will be removed from the pools
the tops of the walls and steps will be scraped to remove algae (the sides of the walls used to be scraped too, but this will no longer take place)
environmentally friendly chemicals will be used to remove the algal residue after scraping – no more chlorine and no more whitewashing!

All of the above means that the pools will be ready for use by the public immediately after cleaning, in contrast to the old protocol, which renders the pool unusable for a period after the cleaning crew has chlorined it.

I’ve asked the City for more information about the drainage procedure, and for more information about the earth-friendly chemicals that the cleaning contractor will use, but with no response so far. (If I get one I’ll obviously update this post.)

Buffels Bay tidal pool inside the Cape Point section of Table Mountain National Park

Many of the City of Cape Town’s tidal pools fall within the Table Mountain National Park Marine Protected Area, and it therefore makes perfect sense to aim to protect the animals living in them while maintaining public safety. Dr Maya Pfaff, another speaker at the information session, even suggested that some of the animals that may now thrive in the pools may actually help to keep the water clean. Mussels and feather duster worms filter the water and improve the clarity, algae take up nutrients, and limpets clean algae off the rocks.

Particularly over the festive season, the beaches and tidal pools around Cape Town are extremely busy. This is a wonderful opportunity for thousands of beach-goers to experience both safe swimming and a little bit more of what the ocean has to offer, instead of a sterile, salt-water pool devoid of healthy marine life. Bringing a snorkel and mask with you when next you go swimming will be well rewarded. To see some pictures of the amazing animals – from nudibranchs to a cuttlefish with eggs – in the St James tidal pool, check out Lisa’s instagram profile.

Do you swim regularly in any of the five pools in which the new cleaning regimen is being tested? What do you think about it? If you think that environmentally gentle cleaning of tidal pools is a good idea, what about letting the city know that you appreciate having tidal pools that are both safe and biodiverse. A short message on the City of Cape Town facebook page to say thank you and keep up the good work (and a request to extend it to the other tidal pools) is a good place to start!

You can read a news article about the new cleaning protocol here.

Shrimp news from False Bay

The University of Cape Town has announced that a further three new species of shrimp, all spotted close to shore near Millers Point in False Bay, have been described and named. All three belong to the same genus (Heteromysis), and look similar, with pale bodies marked by red spots and stripes. One of these new (to science) species lives inside octopus dens, and another lives inside the shell of certain types of hermit crab. These three shrimps join the stargazer shrimp that was discovered by and named for Guido Zsilavecz, citizen scientist and author of several books on False Bay’s marine wildlife.

Two of the new species were discovered by local film maker Craig Foster, founder of the Sea-Change project about which we read last week. These types of discoveries are very exciting and should be a great inspiration and encouragement to divers and other water users. Time in the water is rewarded. If you can’t identify something, send an email with its photo to SURG. It is possible to make significant contributions to science while holding down an entirely non-scientific day job!

Read all about the new shrimps here.

Peet’s Vulcan Rock video

Urchins, brittle stars, corals at Vulcan Rock

Peet made this amazing video while diving Vulcan Rock with us. There is a huge cave with several entrances at the bottom of the reef, and he went inside to check it out.

[youtube=”http://www.youtube.com/watch?v=QPLmfoJnhqU&w=540″]

Dive sites: Vulcan Rock

Vulcan Rock is a dive site just outside Hout Bay. We dived it on a day when the south easter had been blowing for a while, so the visibility was quite good. The dive site is essentially a huge stack of granite boulders, with Vulcan Rock as the highest point. The rocks are covered with sea urchins, rock lobster, corals, sea cucumbers, brittle stars, and a bit of red seaweed.

Esther and I stayed within the range of Open Water divers, not going deeper than 18 metres, but it is possible to go as deep as 30 metres at this site if you go for a bit of a swim. This is definitely a site to visit when the surface conditions are good and the swell is low (not that Hout Bay diving is ever great – or particularly safe – in a big swell).

I had the little Sony camera with me and took some happy snaps. Underneath all the granite is an enormous cave, with several entrances. Peet, who joined us on this dive, made a video of the cave that I will share with you later this week.

Dive date: 19 April 2015

Air temperature: 23 degrees

Water temperature: 10 degrees

Maximum depth: 15.6 metres

Visibility: 12 metres

Dive duration: 39 minutes

Dive sites (Southern Mozambique): Checkers

There are a lot of reefs around Ponta do Ouro and Ponta Malongane, and it was great to dive two new ones (Checkers and Steve’s Ledge) on our visit there in June-July. I did this dive with Christo and Laurine. Esther and Tony were feeling a bit under the weather with mild colds, so they sat out the first dive of the day on the Thursday of our trip. Checkers is a short boat ride from the launch site at Ponta.

The first thing I noticed at Checkers was the abundance of plate coral, which is beautiful but requires divers’ buoyancy to be impeccable to avoid crunching it. (It is surprisingly strong, though – on two separate Sodwana trips, owing to poor buoyancy control and body awareness, I have witnessed divers reclining on huge plate corals like overdressed burlesque dancers in giant martini glasses, and the plate corals survived without breaking. The divers almost didn’t, though! Grr!) There are plate (or table) corals of all sizes, some of them growing across gaps in the reef. This provides excellent habitat for marine life.

The reef has more interesting topography than a place like Doodles, even though it is relatively close to Doodles with no other reef in between. It slopes quite dramatically in some places. Christo suggested swimming back and forth across it in both directions so as to be able to have maximum opportunity to see into all the crevices and under the overhangs. The reef is relatively small and round rather than long, meaning that it’s probably not ideal to dive in a strong current, because doubling back will be tricky.

The porcupinefish swims between Laurine and CvS

There are sand channels running through the reef in places, and as we swam over one of these we were passed by a beautiful porcupinefish with sad eyes, making his way somewhere. He swam right between us without batting an eyelid. I spent quite a lot of time trying to photograph this juvenile batfish, but he was far too busy demarcating his personal space among clouds of other fish under an overhang to turn sideways to the camera.

This is a great dive site for spotting hidden, interesting animals. There is enough life in the form of schooling fish over the reef to keep divers who don’t like sticking their heads under overhangs busy too! Photographic opportunities abound (despite the evidence I have presented here), but it isn’t possible to get to everything in an ethical manner (i.e. without lying on the reef like a plonker) because of the delicate structure of the coral.

Dive date: 2 July 2015

Air temperature: 21 degrees

Water temperature: 23 degrees

Maximum depth: 16.8 metres

Visibility: 12-15 metres

Dive duration: 57 minutes

Article(s): Phenomena & The Verge on a sea star wasting virus

Our wedding starfish at Long Beach… see, he is lying in a heart shape!

The starfish in this picture may or may not still be alive (my guess is not), but it looks very much like a starfish in the early stages of Sea Star Wasting Syndrome (SSWS), minus a few legs. (It isn’t sick – I photographed it at Long Beach a few years ago – and it is actually an invasive species on South Africa’s coast.) Sea stars on the Pacific coast of North America began sickening – suppurating and disintegrating – in mid-2013, and scientists have been scrambling to find the cause. Initially it was not clear what was causing the sea stars to die in such grisly ways: pollution, warming oceans, large storms and other possibilities were considered. The clue that told scientists that the cause was “microscopic and biological” (in the words of National Geographic Phenomena blogger Ed Yong, who covers the subject with admirable clarity) was that starfish in aquaria, who were bathed in water pumped from the ocean and filtered, were also dying.

Yong’s post explains how scientists isolated the virus (a process involving blending, filtering, and genetic sequencing), and what scientists are hoping to learn from the work they have done on this subject. Potential parallels between SSWS and viruses that periodically flare up in human populations (Ebola being a recent example) are interesting.

At The Verge, Elizabeth Lopatto writes in more detail about SSWS, its discovery, and consequences. She points out that sea stars are a “keystone species”, and that

Keystone species help maintain an ecosystem by eating quickly-reproducing prey species like urchins and mussels — keeping populations low. Without the sea stars, the urchin population explodes; bad news for the kelp forests and everything in them. Giant kelp can grow to 150 feet underwater at a speed of two feet a day, but their weaknesses are their holdfasts, which are sort of like tree roots. The holdfasts are home to brittle stars, prawns and snails, among other creatures. Urchins like to eat the kelp holdfasts. Without them, the rest of the kelp drifts off in the tides. In this way, urchins can devour forests, which, higher up, are also home to fish, including several types of commercially-important rockfish, according to the National Oceanic and Atmospheric Administration.

Lopatto’s article is an excellent read – find it here.

(As an aside, the ocean is full – full to the gills – of viruses. This was revealed to me by the Palumbis in The Extreme Life of the Sea.)

Bookshelf: Shorelines, Strandlopers and Shell Middens

Shorelines, Strandlopers and Shell Middens – John Parkington

I’m currently delving into some subjects I know nothing about, stone age archaeology being one. I harboured a childhood dream of excavating ancient Egyptian artefacts, but that came to nought and I ended up a mathematician – manipulating things I can’t even see or touch. Ah well.

Strandlopers are the people who lived as hunter gatherers along the Southern African coastline, related to the San. A shell midden is basically an ancient dustbin, and the strandlopers would have generated these when they stopped at a location for any length of time. They are typically densely packed collections of shells that are all of a certain size (large enough to be worth harvesting and eating) and from a limited set of edible species. In this way they are distinguishable from random heaps of shells. A midden of considerable size would have been built up in a relatively short time owing to the sheer number of molluscs it is necessary to consume in order to have something approaching a decent diet! Shell middens exist around South Africa’s coast, including a couple in False Bay which I plan to hunt down. It is believed that the consumption of shellfish – which are extremely nutritious – by early humans contributed to increased brain size and the development of more complex civilisations.

John Parkington, the author of this book, is a lecturer in archaeology at the University of Cape Town. His writing style is clear and expository, and enabled me to follow along with little to no background knowledge on the subject. The book is extensively illustrated with photographs, including of Parkington’s collaborators at the university. I appreciated the fact that each person’s full name was provided.

If you’re interested in knowing more about the early history of humans along South Africa’s coast, I’d recommend starting with the series Shoreline, which provided an excellent introduction to the subject. The Sea-Change project also explores our ancestors’ interactions with the marine world.

You can find this book here, or perhaps at Kalk Bay Books.