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Under Pressure

At risk of jinxing myself (and perhaps dating myself with an A-Team reference), “I love it when a plan comes together!”

For years I’ve been trying to understand the nuts and bolts of copepod dormancy. Calanus finmarchicus and some other copepods are very abundant planktonic animals that are an important source of food for fishes, whales and seabirds. These copepods are able to survive unfavorable periods, lasting several months, by migrating into deep water, slowing down their metabolism and entering a dormant state. Understanding this dormancy is important to being about to predict how copepod populations – and therefore food availability for their predators – will change from year to year and over longer time scales.

A tricky part of studying Calanus dormancy is that investigators haven’t been able to reliably re-create it in the lab….and people have tried lots of things….light, temperature, food availability and even exposure to chemicals that might be released by predators. I’ve been curious if these efforts have been stymied from the beginning because they have been conducted in land-based labs. The copepods are normally hundreds of feet below sea level when they enter dormancy. My guess is that they can sense the pressure around them through changes in their buoyancy and that going into dormancy at the surface wouldn’t “feel right” to them.

I’ve teamed up with Dr. Scott Wankel in WHOI’s Marine Chemistry and Geochemistry Department to see whether incubating Calanus at elevated pressure might push the copepods into dormancy. I have an opportunity to collect Calanus on an NES-LTER cruise later this month and plan to test out this hypothesis. Scott recently finished constructing several chambers that can be pressurized using a nitrogen tank.

Over the next couple weeks, I’ll be finalizing all the details for my participation on the cruise, and then I’ll just have to hope to catch some Calanus!