Lagrangian Drifters (Michael Stukel, FSU)

The FSU Plankton Ecology Lab is out in force on this cruise, with Dr. Stukel leading a team of three grad students (Natalie Yingling, Christian Fender, and Opeyemi Kehinde).  Our goal is to understand the interactions between marine organisms and global carbon and nitrogen cycles and our creed is that we can sleep when the cruise is over (or in the beanbags strewn across our workspace).

Central to our science is the use of “Lagrangian” arrays.  These arrays are basically gigantic underwater kites that we stick in the water to catch the currents.  The kite portion of the arrays are then attached to floats that communicate with us by satellite, telling us where the currents are going.  This allows us to follow plankton communities.  Really, we’re spending our time stalking patches of tuna larvae and the algae and zooplankton communities that they are living with.  This is necessary, because we want to watch the community evolve over time and the plankton communities do not work like forest communities.  They’re always on the move, so we have to be scientists on the move as well.


Let’s get back to our Lagrangian arrays. “Lagrangian” is a fancy word that means following a moving frame of reference, so a “Lagrangian experiment” is basically the equivalent of following say a storm around.  A Lagrangian study of a hurricane might involve staying inside the eye of the hurricane and continuing to make your measurements inside the eye as the storm moves, instead of just staying at one weather station and making measurements as the hurricane passes you.  Our Lagrangian arrays actually come in three flavors.  One type is just a simple kite and float that we use to mark patches of baby tunas.  The second is our sediment trap array, which allows us to catch sinking particles to understand the ocean’s role in sinking particles.  We’ll chat about that in another blog post.  The most fun Lagrangian array is our incubation array.  This array is used to conduct experiments in the ocean every day.  Basically, the way it works is every morning starting at 2am, we begin setting up experiments.  Those experiments allow us to measure everything from algae growth to zooplankton feeding or nutrient uptake.  To try to get the plankton to behave as naturally as possible after we set up our experiments (using water that might come from near the surface or from ~100 meters deep in the ocean) we clip our experimental bottles onto a line hanging beneath the kite (which we call a “drogue”).  We then lower the entire array (line + bottles + kite + satellite float) by hand into the ocean so that the plankton in the bottles are back at the depths that they came from and pull it back up 24 hours later.  This process, repeating almost every day helps form the rhythm of our lives at sea.  We’ve started doing so many experiments on this incubation array that our bags of bottles have gotten very heavy.  For this reason, part of our pre-cruise preparation involved standing on tall ladders and lifting 50 pound weights with ropes to get ourselves ready to recover this array.  This kind of immersive training is just one of the reasons that oceanographers are better than other kinds of scientists.

More to come from our group later…