I know I’ve been talking a lot about octopuses lately, given the research I’m currently supporting, but for this update, I’d like to focus a moment on the reefs that they live in here on Mo’orea. Visitors to the Vancouver Aquarium get a chance to glimpse just a few of the impressive invertebrates that can be found in the waters in our backyard. Many of these invertebrates are record holders in the world’s oceans. For example, the Aquarium is home to the largest octopus species that we currently know about (the giant Pacific octopus), the largest chiton species (the gumboot chiton), and the largest sea star species (the sunflower sea star). Luckily, we are not home to the world’s deadliest sea star: the crown of thorns (Acanthaster planci), which can get very close in size to the sunflower sea star, which is typically around one meter (or 3.3 feet) long.
The crown of thorns sea star (see image above) is found in the Indo-Pacific region (which consists of the tropical waters of the Indian Ocean, the western & central Pacific Ocean, and the seas connecting the two in and around Indonesia). This sea star is a “normal” resident of the Indo-Pacific much of the time, but from time to time there is a population outbreak. These outbreaks decimate entire reefs in a relatively short period of time. This is something that French Polynesia, including the island of Mo’orea, has experienced first hand.
The research station where the octopus team is staying in Mo’orea is CRIOBE, or Centre de Recherches Insulaires et Observatoire de l’Environnement. A major mission of CRIOBE is to observe the reef ecosystems in the South Pacific, which they’ve been doing for around thirty years.
Yannick Chancerelle, Operations Manager of CRIOBE, talked to us this week about some of the major concerns regarding the coral reefs of the area. He showed us what the healthy reefs looked like here in 2005, when reef coverage was close to 50 per cent, indicating a healthy reef system (see below):
Then he showed the image of what the reef looked like in 2009 after an outbreak of the crown of thorns. The living coral cover dropped to about one per cent (see photo below):
In 2009, CRIOBE and many others were concerned about how the reef would recover, but they thought recovery was possible, as they saw that the physical structure of the reefs was still in place. It would just take a long time. As for what caused this outbreak (and others like it), no one yet knows, despite a number of research studies.
But then, a second disaster struck. And it looked like this (click on this link). On February 3-4, 2010, Oli hit the island of Mo’orea. On February 7, CRIOBE was able to take note of damage that had occurred to the reefs, and found that that the one per cent of coral that was remaining after the crown of thorns had been almost completely destroyed. Coral cover was less than one per cent and was decimated:
That reef skeleton that would have allowed the reefs to recover after the crown of thorns outbreak had been destroyed. The waves and boulders tossed around by the cyclone reduced the structure of the dead colonies.
This habitat, important for the many animals that rely on coral colonies for food, shelter and nesting, is now completely altered. It is hard to know now what might happen. Will algae take over the area where the coral once was (leading to the disappearance of the reef)? Or perhaps the reef will be able to build again, as it has done for millions of years?
Today, CRIOBE researchers tell me the reef is getting better, ever so slowly (as is normal for corals). This is something our team has seen, as the photo below comes from one of our dives:
Some areas are now seeing around five per cent coverage, showing that things are improving. But this also really shows us that now is the time to keep watching, observing and doing what we can to learn more about what’s happening in our oceans so that we can better protect the reef and the animals that live there.
Guest blog post by Keely Langford, an interpretive delivery specialist at the Vancouver Aquarium. Keely is accompanying a team of researchers, led by Dr. Jennifer Mather of University of Lethbridge, to the South Pacific this summer. This team of researchers is studying how the day octopus (Octopus cyanea) chooses its food. Keely is sharing a series of blog post updates throughout this trip. Her first and second posts in these series are also available to read.