Laje de Santos
As I left Brazil, after spending nearly a month in the field, I was informed of the passing of one of my friends in a diving accident in South Africa. He was a great man and he will be deeply missed, but his passing reminded me what a curiously unforgiving place the ocean can be. I find that the ocean’s wild beauty often belies its fierce nature. In reality our oceans are vast, their waters often relentlessly rough and turbulent.
Diving at Laje de Santos
Many parts of these great expanses of water are distinctly inhospitable, however, scattered within this liquid eternity are tiny oases of hope, life and refuge. Laje de Santos is precisely one of those places. This little barren rock juts out from a largely desolate seafloor like a proud sentinel in what I often found to be a stormy and chaotic Brazilian sea. As you approach you cannot shake the uncomfortable feeling that this rock is really out in the middle of nowhere. Once moored and looking down into its surrounding cold, green water, your apt to think, “what am I doing out here?”
Hairy carangid fish
But one giant leap into the chilly waters of the Atlantic reveals a very different reality. This rock is actually home to an incredible amount of life. While it is only approximately 300 meters or so long, Laje de Santos is an amazing refuge to at least 196 species of fish including some magically rare animals such as hairy carangid fish (Alectis ciliaris), Halichoeres sazimai, and an endemic species of tube dwelling Cerianthos anenome.
Sand Tiger Shark at Laje
Laje is also rich in elasmobranch fauna (particularly rays) and during my short time there I was fortunate enough to dive with a couple of friendly sand tiger sharks as well as many eagle rays, butterfly rays, thorny stingrays and of course the elusive giant manta ray! While all of these animals are relatively frequent visitors or inhabitants to this small island, Laje also provides sanctuary, on occasion, to animals passing through on ocean voyages such as Bryde’s whales, Mola mola, penguins and whale sharks. And yes, I did say penguins and whale sharks in the same sentence! Oddly enough these two animals have actually been seen on the same day at this location before (one of the most unbelievable things I have ever seen by the way!). (more…)
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The ongoing research of Rainer von Brandis into the impacts of hawksbill turtle foraging behaviour in the Seychelles has been revealing the startling importance of their role in maintaining balanced coral reef ecosystems. With another season’s field work drawing to a close, it’s a good opportunity to reflect on Rainer’s discoveries thus far.
Hawksbill turtles have been severely depleted by humans in recent centuries and their absence from modern reefs has almost certainly influenced ecosystem dynamics. Prior to their depletion, hawksbill turtles had substantial influence on their marine habitats through their many roles as consumers, prey, and competitors; as hosts for parasites and pathogens; as substrates for epibionts; as nutrient transporters; and as modifiers of the landscape.
At D’Arros Island, Rainer’s underwater observations indicate that the roles of foraging hawksbills as both consumers and modifiers of the landscape are fundamental to the sustained functioning of the platform reef ecosystem.
Hawksbill turtle extracting a sponge from the reef. Photo by Rainer von Brandis.
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Diving and Laje de Santos
They say good things come to those who are patient. I never really gave this saying too much thought until just recently…In the name of manta research I have spent six solid weeks (during the winter of 2009 and winter of 2010) diving a remote offshore rock called Laje de Santos in the south of Brazil looking for the elusive giant manta (Manta birostris). Until today, I have searched in vain. I was the one that actually chose this location for part of the worldwide study on this newly discovered species of ray, as this little spec of a rock is the largest documented aggregation site for this species in the southern Atlantic Ocean. But, to tell you the truth, despite my normal determined outlook when working in the field, I was really beginning to loose hope (and that’s pretty bad, since my current international research campaign is ironically named “Ray of Hope’).
Andrea in the field at Laje
But that’s the funny thing about marine field research and, I suppose, diving in general. It doesn’t matter what the ocean throws at you…countless hours of searching, dozens of dives in cold, green water, boat trip after boat trip on rough, windy seas…all of the excruciating effort and disappointment literally seems melt away the second the animal that you have been searching for appears. Your breath catches in your throat, time stands still and everything seems to make sense in the world. And this is why we divers torture ourselves by squeezing into unbearably uncomfortable wetsuits, why we swim around the sea covered in all kinds of tanks and hoses, and why we spend all of our money and time bobbing around in the middle of the ocean. It is precisely for this sensation and these encounters with special marine creatures. For the majority of us, the most precious encounters are with large, elusive megafauna like sharks, whales and dolphins. The object of my affection, of course, is the manta ray.
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The fact that Rainer has managed to demonstrate that these marine reptilians play a pivotal role in maintaining coral reef biodiversity makes their fragile status of Critically Endangered all the more alarming. Under serious threat of extinction, the removal of these wardens from the reef could have even more dramatic knock-on effects throughout the ecosystem than previously thought: no longer being preyed upon by turtles, sponges could then out compete corals and dominate the reefs, causing reef ecosystems to support a far lower biodiversity.
Hawksbill turtles are in trouble because they have been harvested for thousands of years mainly for the aesthetic qualities of their shells, which are used to make combs, jewellery boxes, spectacle frames and ornaments. However, somewhat misleadingly, such products are usually referred to as ‘tortoise shell’ despite being produced from the scutes, or shell plates, of the turtles, making the true source of the product less apparent to customers. The exploitation of hawksbill turtles stretches back far through history: after invading Egypt Julius Caesar prized tortoise shell so highly he brought it back to Rome amongst his chief spoils; ninth century Arabs traded in tortoises hell throughout the Indian Ocean; and by 1700 Japanese artisans were carving exquisite ornaments from tortoise shell (called bekko) that were traded in markets around the world. Japan subsequently became the primary buyer of hawksbill turtles, with in excess of 1.3 million dead individuals being imported between 1950 and 1992.
Hawksbill turtle forages on a reef in the Seychelles. Photo by Rainer von Brandis.
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Over the past four years Rainer von Brandis has familiarised himself with a population of the usually timid hawksbill turtle in the Amirante Islands, Seychelles. This has allowed him to observe the turtles behaving naturally in their aquatic environment, revealing just how important they are for the maintenance of biodiversity on coral reefs.
The remote nature of Rainer’s study site, combined with a sound conservation policy in the Seychelles, means it supports relatively healthy turtle numbers. Consequently it has been possible to monitor how the hawksbill turtles function within a coral reef ecosystem outside of the relentless over-exploitation that has left them classified as Critically Endangered by the IUCN. Gradually, Rainer has been able to determine their prey preferences, how much they eat, their habitat requirements and even social interactions.
Reef fish lurk for scraps as a hawksbill turtle dines on sponge. (Photo: Rainer von Brandis)
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