I’m currently sitting in the Dallas airport waiting for a flight to Santiago, Chile, enroute to Palmer Station for the 2015 spring season. Since there is no airfield at Palmer we’ll go in and out by boat (the ARSV Laurence M. Gould). Hopefully we’ll be at the station by October 28 and able to start doing some science not too long after that. There are a couple of reasons why I’m excited about the upcoming season. First, as I discuss in this post, conditions are highly unusual this year, with the extent of sea ice reaching a level not seen at Palmer Station for many years. The reason for this seems to be the persistent warm El Niño conditions in the tropical Pacific Ocean, now complemented by a near zero to negative Southern Annual Mode (negative SAM values are correlated to high sea ice conditions). This increase in sea ice is a counter intuitive but very real effect of global climate change; increased heat in one area of the globe alters global wind patterns and decreases the flow of heat to other areas of the globe. It hasn’t actually been very cold at Palmer Station (the high today was a balmy 24 °F at the time of writing) and how long the sea ice lasts will be depend very much on what happens to winds in the region.
Coming in an era defined by decreasing sea ice along the West Antarctic Peninsula the presence of heavy ice cover could have some interesting ecological impacts. There is a strong likelihood that it will be good for the Adélie penguins, but my primary interest is a little lower down in the food web. I’ll be studying interactions between phytoplankton, the basal food source for the WAP ecosystem, and bacteria at the onset of the spring bloom, hoping to identify cooperative interactions through patterns in bacterial gene expression. Toxic compounds produced by phytoplankton, for example, may be cleaned up by bacterial partners, allowing photosynthesis to proceed more efficiently (ultimately meaning more food for the whole food web). Observing the expression of genes coding for the bacterial enzymes that carry out these processes would be strong evidence for this kind of synergy, which leads me to the second reason I’m excited about the upcoming season.
This year I’m joined by Colleen Hansel and Jamie Collins from the Woods Hole Oceanographic Institute. Colleen and Jamie are chemical oceanographers and experts in identifying specific compounds produced by phytoplankton. Colleen has pioneered a technique to measure superoxide, a damaging free radical, directly in the water column. This is not a trivial undertaking as the half-life of superoxide is only seconds, making traditional oceanographic sampling techniques (such as a Niskin bottle) impossible to employ. Instead we will focus on sampling water in the first few meters of the water column, just above the maximum zone of primary production. Superoxide is produced during photosynthesis, when energetic electrons glob onto free oxygen. The extra electron makes oxygen highly reactive (hence superoxide; it’s a superoxidant) and physiologically damaging. Bacteria have some interesting molecular tools to deal with superoxide however, so perhaps they’ve evolved the ability to perform this service for phytoplankton in exchange for fixed carbon. Coupling observations of gene expression with measures of superoxide and other reactive chemical species is much more powerful, and will tell a much more complete story, than either does alone.
It’s impossible to anticipate how the ice will impact our science plan until we’re at the station and get a feel for how logistics will work this season. Typically sampling at Palmer Station is done by zodiac, which requires reasonably ice-free conditions. The zodiacs can push around a small amount of brash ice but lack the mass (and shrouded propeller) to deal with large quantities. The ice is solid enough this year that we may be allowed to use this ice as a sampling platform – something I’ve got plenty of experience with from previous trips to the Arctic and Antarctic. This is a little out of the norm for Palmer Station however, so we’ll have to see how negotiations proceed.
In our worst-case scenario the ice conditions deteriorate to the point that we can’t sample from it, but not so much that we can push a zodiac through it. The normal sampling procedure in this case is to use a plumbed seawater intake to sample from below the ice (with the added benefit that you can sample from the comfort of the lab), however, this won’t work given the short half-life of superoxide. In this eventuality I think we can salvage the project by focusing on ice algae in place of phytoplankton. Ice algae are essentially phytoplankton which have given up their free-living lifestyle and formed colonies on the underside of the sea ice. These dense mats are a very important food source for juvenile krill, but are understudied in the region given the inconsistent nature of sea ice along the WAP. If we can access some decent ice floes from shore I think we can make a good study of the superoxide gradient, and bacterial response, toward the ice algal colonies. Previous work has shown that ice algae can be under significant oxidative stress so they may have good reason to solicit a little help from bacteria.