Friday, March 4, 2011

Indonesia Expedition: Journey to the center of the Earth

Joint post by Dr. Randi Rotjan and Dr. Chrissy Huffard:

We have just crossed the equator, marking that we're here; we've arrived: we've made it to the center of the earth. At least in Indonesia, this also means the center of tropical biodiversity, and the coral and fish abundance are pretty stellar as well. It makes transects both challenging and rewarding, as I keep encountering species that I've only read about in books, but we're getting the work done and being productive.

(Acropora thicket with planktivorous chromis and anthias) Photo: R. Rotjan)

(Turbinaria, Acropora, and Tubastrea corals in Raja Ampat) Photo: R. Rotjan)

So, what makes Raja Ampat the marine biodiversity capital of the world? There are three common hypotheses about biodiversity patterns in the Indo-Pacific, with Raja Ampat as the epicenter—the Center of Origin (species evolved here and disperse from here), the Center of Overlap (where animals with wide-ranging distributions overlap in part) and the Center of Accumulation (ocean currents are such that larvae from all over converge here). In reality, all three hypotheses are probably in play.

(Soft corals are an important part of the benthos in the IndoPacific. Photo: R. Rotjan)

(Amphiprion ocellaris clownfish, Photo: R. Rotjan)

In collaboration with scientists at the University of Papua and University of California Los Angeles (UCLA), Conservation International (CI) has shown, based on genetic evidence, that many species have evolved here and then dispersed elsewhere. For example, the nearby Cendrawasih Bay has experienced varying degrees of isolation from other waters over time, as sea level rise changes, and as Yeben island has moved slowly across the entrance with tectonic activity. This bay now has endemic fishes and genotypes found nowhere else on earth. The dynamic currents around Raja Ampat have created barriers between this area and nearby Halmahera, further isolating some populations. Such isolation has allowed mutations to take hold in a population, causing speciation, or the process by which new species evolve.

(Plectorhinchus chaetodonoides, "many-spotted sweetlips". Photo: R. Rotjan)

(Spotted garden eels, Heteroconger hassi. Photo: R. Rotjan)

While we're not out to discover any new species this trip, who knows? Here, it's certainly possible. In the meantime, we're running transects and continuing to look for new seamounts.

Surprisingly enough, the center of the Earth is a very busy place indeed!

More soon,

Randi and Crissy

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