We are on the deck of the dive tender, securing the SVII and our dive gear in rough seas after our latest dive on iconic Pedras Secas, Fernando de Noronha. We are surrounded by the clear, azure blue sea of the exposed eastern side of this remote Brazilian archipelago in the southern Atlantic Ocean.
The mainland is a long 354km away. Sea birds dip and weave over the cresting swells in the fresh breeze. Waves crash in an explosive display of white on the dark volcanic rocky shore of the largest island in the chain, just to the west of us. I am here with the Head of Technology & Special Operations Christophe Bailhache and as we catch our breaths after the dive we comment on how it feels wild and remote here.
We are on a special survey mission to reveal the warm water reefs of Fernando de Noronha and Rocas Atoll, some 145km to the west. We will be producing virtual dives to the tens of millions of Brazilians and other people around the world who have access to the internet but will never get to see this amazing place first hand. And as with all our SVII surveys these virtual dives are also important empirical baseline records of reef health.
There are less than 10 oceanic island groups in the South Atlantic and the Fernando de Noronha Archipelago and Rocas Atoll represent more than 50% of the islands in this region in terms of total surface area. This makes them really important ecologically. The islands are home to the largest concentration of tropical seabirds in the Western Atlantic, and their reefs are full of reef fish, sharks and turtles. Rocas Atoll is a critical Atlantic green turtle nesting area. At the end of one of our dives on Fernando de Noronha we were joined by a school of playful spinner dolphins, commonly seen residents of the islands.
The two locations, listed as World Heritage sites by UNESCO in 2001, are well protected by Brazil. Development and tourism has been carefully controlled, fishing restricted to designated areas and access to Rocas Atoll further limited to researchers only.
Although the warm waters around Fernando de Noronha and Rocas Atoll support some coral growth, the reefs here are dominated by encrusting sponges, soft corals and coralline algae that coat the sea-carved jagged volcanic rocky reefs around the islands and the atoll.
After a successful week of image collection on the most representative reefs around Fernando de Noronha we sailed over to Rocas Atoll. The name “Rocas” refers to the series of volcanic “rocks” that are visible above the water along the eastern rim of the atoll. It’s as if the ocean has tossed them up onto the reef, where they have weathered and cemented to the algae encrusted reef. The sheltered lagoon is home to large numbers of lemon sharks and we encountered several nurse sharks in the main channel to the north – signs of a healthy ecosystem.
Rocas Atoll is pretty special. Not only is it the only atoll in the southern Atlantic Ocean but it’s also not your typical coral-formed atoll. There are three species of corals that grow on the atoll but together they cover less than 5% of the reef surface. Instead it is coralline algae that are the all important reef builders here.
Coralline algae, like corals, fix carbon from atmospheric carbon dioxide to create reef-building calcium carbonates. Scientists estimate that some five thousand years of coralline algae growth around the submerging crater rim of a mid-ocean volcano have formed Rocas Atoll.
And, as with corals, coralline algae’s ability to fix carbon as calcium carbonate and keep growing the atoll is being disrupted by ocean acidification. So, as with the surveys we are doing on coral reefs, our survey of Fernando de Noronha and Rocas Atoll will provide an all-important empirical baseline of species health and coverage, in this case coralline algae, that are critical to building and maintaining warm-water reef ecosystems.
After completing our surveys on Rocas Atoll, we weighed anchor and turned for Brazil, reflecting on the fact that however remote and protected reef ecosystems are, they are still vulnerable to bigger human-induced global impacts no matter where they are on our planet.
We look forward to revealing the underwater beauty of Fernando de Noronha and Rocas Atoll to Brazilians and the world soon.