Tuesday, April 10, 2012

Brazil: Oceans of algae, buracas and more

Les Kaufman, New England Aquarium research scholar, is in northern Brazil to study the unique marine habitats of the Abrolhos Shelf with scientists from Conservation International and local universities. He and fellow researchers intend to learn more about the marine life of Abrolhos, its links with terrestrial communities, how both are likely to be affected by global climate change and what people can do to protect this special place and oceans worldwide. Read his previous entries from this expedition here and here.

We did it. We’ve succeeded in dodging the weather to complete the last three legs of Expedicio Abrolhos: Novas Fronteras. This entailed four days of ROV and drop camera exploration of the central southern and eastern Abrolhos shelf, three days remote and SCUBA work at buracas on the eastern shelf and several more days of sharing our discoveries with press and media journalists.

 A diver swims over a buraca covered with seaweed on Brazil's Abrolhos Bank. Depth: 35 meters. 
(Photo by Enrico Maronas / CI-Brazil)

As always, the sea has not failed to surprise, confuse, illuminate and reorient us. Moreover, it’s armed us to move ahead with better measures to conserve and benefit from all this new stuff...realizing that Brazilians have been depending upon these systems all along, even if only a handful of people knew it.


On previous expeditions, side-scan sonar had revealed that the area of hard sea bottom on the Abrolhos Shelf was twenty times larger than we’d once thought. The question is: What actually lives on this hard bottom? Is it all deep coral reef? Deep reefs with very high live coral coverage have been discovered elsewhere. We’d hoped it might be coral, as we are worried about the future of one brain coral in particular: Mussismilia brasiliensis, the major reef builder on the Abrolhos Bank which is found nowhere else in the ocean. If not reef-building corals, then what?

Journalist Herton Escobar romances the reef…mesophotically. Depth: 32 meters. (Photo by Enrico Maronas / CI-Brazil)

Well, what we found in these newly explored areas seems mostly to be ancient reef framework, overgrown by diverse living organisms and, like other reefs, densely inhabited by fishes. So these outer shelf mesophotic reefs are interesting, vibrant and important to many things people care about…but the corals are few and far between. That means that the Mussismilia reefs near shore are  are really important... every effort must be made to nurture and protect them. And these are the reefs most vulnerable to overfishing, deforestation, coastal pollution and over development.


Some of the biggest surprises on the expedition were all about algae. The rhodoliths we were anticipating.  What we were not ready for was the seaweed. Untold amounts of it. Brown, green and red fleshy algae carpeting rhodolith beds as far as the eye could sea — and as near as we could tell, accounting for thousands of square miles of shelf habitat.

Doctoral student Matheus Freitas expertly pilots the ROV over rhodolith beds covered by 1 meter-high fleshy algae (seaweed) — a vast fleshy algal pavement.  Depth: -2 meters. (Photo by Enrico Maronas / CI-Brazil)


The other big surprise had to do with the buracas. Some of these, especially in summer time, become filled up with algal fronds — and we’re talking a lot of seaweed to fill up an entire buraca. The seaweed ferments, releasing precious nutrients, and generating a build-up of gas. While we were positioned over one particular buraca, a large amount of material was jettisoned, and made its way all the way to the surface beside the boat, releasing an overwhelming stench. The implication of this is profound. Buracas could play an important role in nutrient cycling on the outer shelf. And not just that. Hovering over many buracas are enormous shoals of fish, mostly members of the grunt family, and of these, mostly two species: tomtate, and a form of white grunt (Haemulon plumieri) that is actually yellow. This fish, though very familiar, is quite possibly a valid but undescribed species unique to Brazil. It would not be the first.

Tomtate (Haemulon aurolineatum) mass over the mouth of a big buraca, cloaked by a layer of floating seaweed atop meters of fermenting algae underneath. Depth: 35 meters. (Photo by Enrico Maronas
/ CI-Brazil)

Some of the 60 members of the Abrolhos expedition team. (Photo credit: Luis Carlos JĂșnior / CI-Brazil)

The field portion of Expedicio Abrolhos: Novas Fronteras has concluded. It was an amazing journey of discovery, with kudos to Drs. Rodrigo Moura and Guilherme Dutra for pulling off a monumental effort that involved at least three vessels, more than 60 scientists and stretched over two months offshore, with many complicated legs, technical challenges and crew change-outs. We have made some fantastic finds. Our conceptions of the great ecological machine that is Abrolhos — what it is made of and how it works — has been expanded and transformed from the fuzzy early notions we carried with us out to sea, to a picture, now sharp and startling but still rife with mystery, of a huge new world.

– Les

Les is also working with Conservation International during this expedition. You can find his entries are cross posted on their blog.

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