Mirror, mirror on the wall, which is the world`s southernmost reef of all?

Two places more than 11,000 km apart vie for the status of being the southernmost coral reef in the world! Since the southern extent of the Aliwal Shoal reef off the east coast of South Africa is not accurately mapped, the reefs of the small island of Lord Howe between New Zealand and Australia could also be the southernmost. Both lie approximately on the 30th southern latitude, making them much more southerly than any other known coral reefs on our planet. It is still almost 2,000 km from Lord Howe to Australia's large barrier reef!

The east coast of South Africa

Let's start with the reefs of Aliwal Shoal about 50 km south of Durban on the east coast of South Africa. Unfortunately, this is not a reef for convenient off-shore diving or snorkelling, because it lies several kilometres off the coast. Even the boat trip there is a bit of an adventure, because getting a view of what might be the southernmost reef in the world isn’t supposed to come easy. To give you a clear idea of the extreme currents in this habitat, where the corals exist far south of the actual reef belt, here is a brief look at the beginning of our trip to the reef.

Very early in the morning we meet the skipper with his boat on a trailer on the hundred kilometre long sandy beach. The long swell from the Indian Ocean breaks into very powerful waves and everyone’s first thought is: how on earth do we get through that? And exactly that’s why we start off with a briefing that everyone has to follow closely: someone goes ahead and pulls the bow line of the boat in the direction of the waves. This unfortunate person will swallow a lot of water due to the depth of the water, that much is clear. The others push the boat from behind with all their might into the waves, so far that the engine can be lowered into the water. Then the bowman quickly climbs into the boat with the towline - assuming he can still draw breath - followed by everyone else, and everyone quickly claws their feet into the catching loops at the bottom of the boat. The skipper then rides up and down in the spray parallel to the beach until he thinks he’s found a wave he can ride without tipping the boat up. Now comes the real adventure, because now it's full throttle from 300 hp into the wave that is just breaking. The boat stands upright for a short time and then tips forward onto the water. Then it's done, and everyone can throw up in peace during the next thirty minutes of boating over the rough Indian Ocean.

Even the descent to the reef, which lies at a depth of about 30 m, is unorthodox. Normally all the divers one after the other drop backwards into the water at their own pace, leisurely paddle to the anchor rope at the surface and then dive down together. With the wave crests and the prevailing surface current, the only way to do it here is to get everyone into the water at once, dive down as quickly as possible and somehow reunite at a depth of 30 metres.

We lost our most inexperienced diver right away. The boat picked him up, but unfortunately he missed the dive. It's a pity, because this reef is really something. Once you have passed the murky and current-rich water of the first twenty metres, you are greeted by relatively clear water and patrolling sand tiger sharks. We saltwater aquarists say a quick "hello" to the sharks and marvel at the diversity of corals, which we would not have expected in the cold and deep water. The literature always says that reef-building corals tolerate around 20 °C as the coldest temperature. Here, in winter (June to August), the water temperatures drop well below twenty, usually to 16-17 °C! Nevertheless, we find the red Tubastraea, Dendronephthya soft corals, black Tubastraea micranthus, Alcyonacea (gorgonians), yellow crustose anemones and sponges aplenty. There were, however, no branched stony corals like acropores at all. One white coral species was completely unknown to us!

Pseudanthias flagfish stand in groups of hundreds in the current and snatch up plankton. If it weren't for the four-metre-long sand tiger sharks, you'd think you were in the Maldives!

We are marine aquarists with an eye for corals and fish suitable for aquariums, but most divers are here especially for these sand tiger sharks. To this end they happily undergo the thrills and spills of the boat ride. Unfortunately some divers follow the animals into the caves and drive them away. Shark expert Andy Cobb taught us in a lecture that we should just wait at the bottom. The sharks are curious and will come to us. Even though the dive time at a depth of 30 m is somewhat limited, it’s worth the wait! The animals swam calmly along us at a distance of 50 cm.

On the way back to the beach, we stopped briefly at a humpback whale, manta rays and a group of blacktip sharks in the open water before our boat headed for the beach at full throttle, eventually tipping over onto one side as we came to a stop, emptying half of our team onto the sand in the process.

East of Australia

Let's go to the other side of the globe. In the Pacific in the middle of nowhere lies the small island of Lord Howe, known aquaristically for the now extremely popular coral Micromussa lordhowensis, which used to belong to the genus Acanthastrea. As this island has a short airstrip, we can fly there directly from Sydney or Brisbane. There are even five hotels to choose from and a very good dive centre, "Pro Dive Lord Howe". Ornithologists literally make a pilgrimage to Lord Howe, as the rocky elevation in the north of the island, the 875 m high Mount Gower, is besieged by over 30,000 seabirds at times. Sir Richard Attenborough once filmed the crash-like landings of the gannets in the wooded ridge - simply sensational. For us non-birdwatchers, it is simply beautiful to experience seabirds on the island that have no fear of humans.

Besides ornithologists looking for birds and wingsuit fans (great videos on YouTube!), we can also, with a bit of luck, find seawater aquarists on the tiny Lord Howe Island. Their destination is a rock about 30 km away: Ball's Pyramid rises out of the water from great depths as a single rock 560 m high.

On this rock two decades ago scientists discovered the tree lobster Dryococelus australis , an insect called the "Lord Howe Island stick Insect", which was thought to be extinct. The population of this endemic animal was wiped out by rats that arrived on the island in a supply ship in 1918. In 1960, this invertebrate species was declared extinct. However, after two dead tree lobsters were discovered in 1969, the rock was examined more closely, and from 2003 Stephen Fellenberg succeeded in artificially reproducing this species with two captured pairs in order to release them into the wild. In 2008, 450 animals were counted, in 2012 there were already 9,000. This shows how important the breeding of endangered species can be for the protection of species, and the breeding efforts of marine aquarists should also be seen under this aspect.

Endemic marine angelfish

But aquarists are drawn there for a completely different reason: this is the only place, apart from - very occasionally - some other reefs in the Tasman Sea, where the marine angelfish Chaetodontoplus ballinae lives, whose species epithet has nothing to do with the island of Bali, because it refers to the rock Ball's Pyramid.

When I visited the island, we made three attempts to get to the Ball's Pyramid across the open sea and had to abort all three because the waves were too high. Very frustrating, but the island also offers really nice alternatives with its reefs and the mix with the underwater fauna of South Australia. The endemic butterfly fish Amphichaetodon howensis  , from a genus comprising only two species, can be seen fairly often. The abundance of a species is actually something that is not something people like to talk about. What good is it if we fly to Hawaii, for example, to finally experience a dragon moray (Enchelycore pardalis)  in its natural habitat as opposed to in an aquarium, but then discover once we’re there that the last dragon moray was sighted five years ago! At Lord Howe, almost all the marine life is concentrated on a relatively small reef system. This increases our chances of actually seeing the species that live there!

Dorado for ornamental algae lovers

For many Pacific coral reef fish like Chaetodon mertensii  , Lord Howe forms the southern limit of distribution. And even if we missed Chaetodontoplus ballinae at Ball's Pyramid, the sight of Chaetodontoplus conspicillatus compensates. Experiencing the rare anemonefish Amphiprion mccullochi  is not an everyday occurrence, but almost certain to happen here. Are you a fan of ornamental algae in the aquarium? At Lord Howe Island you will find algae like you have certainly never seen before! In the shallow water, within snorkelling distance of the beach, grow the most beautiful underwater gardens, which are so green that a planted freshwater aquarium looks like a desert in comparison.

At the popular Neds Beach in the north-east of the island, fish feedings are sometimes held in the shallows of the sandy beach in the late afternoon for the few tourists who have strayed to Lord Howe. The spectacle is well worth seeing, as mackerel and other high sea creatures share the pieces of fish with seabirds. Underwater, it looks funny when the birds' webbed feet paddle among the mackerel darting around. It gets really interesting, however, when the tourists have left and calm returns. A few fish pieces have sunk between the rocks, and then it's just a matter of waiting until the first sharks arrive. Their sense of smell inevitably leads them to every single piece of fish, which is then fought over intensively. But since sharks never indulge in the feeding frenzy they are rumoured to indulge in, the fighting is simply food envy, and you are absolutely safe as a snorkeller. You can even experience the sharks tugging at the fish remains as they swim towards the camera. So if you are fed up with algae and reef, you can move on to the shark programme.

One thing, however, remained unclear to me until today: one species of fish showed frequent gill cover deformities. If we were anywhere near a former nuclear test site, I would guess that it was late nuclear damage. But Mururoa or Tuamoto are about 6,000 km away. Something is affecting this species that doesn’t affect all the other fish species that live here.

© 02.10.2022

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Heiko Blessin
Dipl.-Biologe

Tauchen, Fotografie, Aquaristik, Haie, Motorrad

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