Red Tree Coral

Photo by Bob Stone

Primnoa pacifica, the Red Tree Coral is a coral usually found at depths of over a few hundred meters in the North Pacific, however in the Alaskan fjords often grows much shallower, within a few tens of meters. How does it do this? We're not entirely sure, and call animals that do this, often in high and low latitude fjord systems, deep-water emergent species. It could be because fjords in high and low latitudes are cold like the deep-sea, the fjords often have a freshwater layer on top creating darkness below and often these systems are high in nutrients and have the fast currents that cold-water corals like.

The exact reasons are unknown, but it does present a unique opportunity to study these corals in a much more accessible place. Usually to work on deep-sea corals we have to get expensive equipment - submersibles or ROVs, which typically run at over $30,000 per day, so when you are lucky enough to get one, you don't get it for very many days! Cold-water corals that grow shallow can be sampled by SCUBA diving, and they can be sampled year around, just like you can with shallow water corals. To get a good idea of how corals reproduce you need samples from more than just one time of year - think of animals like birds, who lay their eggs in the spring. Well some corals can be the same, just reproducing once a year. If you took just one sample in the fall though, you would miss that entirely, so you need to have more than one "season", and preferably all seasons, to be able to really know what is going on.

In the deep-sea I am used to puzzles, we get samples here and there, from populations separated by many miles, yet because of the scarcity of samples I have to lump them all together to get a picture of what is going on. That works to a degree, but you're always missing something and there are always caveats with your data.

The Tracy Arm Primnoa pacifica represents my nirvana as a cold-water coral reproductive biologist - an area I can get samples, 5 times in a year, from 30 colonies, all in the same place, all at the same depth - that NEVER happens with deep-sea samples. So this is an exciting project for me - what will we find? Tune in to find out, though i'll only be joining the diving crew on this first expedition (to make sure we tag enough females and males), there will be 5 expeditions I'll be getting samples from over this next year. This first cruise leaves on Tuesday, after the long weekend.