The Bowman Lab

After a tough couple of weeks things are starting to look up.  I’ve got the flow cytometer up and running, and Colleen’s instrument received a complete makeover (thanks to the über instrument tech at Palmer) and is producing good data.  The big question is whether I can gain enough proficiency over the next two days to keep it going after Colleen leaves on Sunday.

The operational instrument status comes just in time; yesterday we went back to the sea ice station that we established on Tuesday to do some science.  In addition to collecting some pretty novel data it was a good chance to practice the measurements we’ll be making all season for the Palmer LTER.  It felt good to get out but hopefully for most of the season it will be a little warmer, however.  That it would be cold in early spring in Antarctica is kind of a no-brainer, but that didn’t keep it from surprising me yesterday.  And the downside to doing fieldwork cold is that it takes longer, so you end up getting colder, and things take even longer…

Jamie, Nicole, and I get escorted off the ice by a lone adélie  penguin. The adélie seemed pretty interested in what we were up to at the ice station and followed us the whole way back. Thanks to Rebecca Shoop, the Palmer Station manager, for the photo.

In addition to making all the core LTER measurements (see the end for descriptions); chlorophyll a, nutrients (inorganic nitrogen and phosphorous), primary production, bacterial production, dissolved organic carbon, particulate organic carbon, bacterial abundance, photosynthetically active radiation, and UV, we took multiple RNA and DNA samples (my main focus for this trip), large amounts of water for lipidomics (Jamie’s project) and samples to measure hydrogen peroxide.  This last measurement was a consolation prize since we couldn’t measure superoxide – the two species have some similarities – and it gives us some indication of what to expect now that Colleen’s instrument is up and running.

So what did we find?  It’s early in the season, and there isn’t that much happening yet below the ice.  Everything is driven by light, and it’s pretty dark under there.  But things are starting to happen, and all the action is near the ice.  We measured only two depths in the water column (and that still took us over three hours), just below the ice and 2 meters further down.  Even over that short distance there was a big difference in what’s going on.  The concentration of hydrogen peroxide – a byproduct of photosynthesis – was much higher near the ice, and there were about four times as many bacteria just beneath the ice than 2 meters below it.

Hopefully, if the weather’s good we’ll get a chance to go back out on Monday.  If the ice holds together for just a couple more weeks we’ll be able to document the transition from an ice-covered to an ice-free state, and get the data to test some hypotheses about how bacteria and phytoplankton respond to this transition.  In the meantime yesterday’s bitterly cold wind has given way to calm conditions and outside the snow is falling.  The woodstove in the Palmer Station galley is putting out a nice glow and the stress of fieldwork is dissipating for a moment…

As promised here’s a quick description of the core LTER measurements:

Chlorophyll a: The principal (but certainly not only) photosynthetic pigment in phytoplankton.  Oceanographers having been measuring the concentration of chlorophyll a in the water for a long time as a measure of phytoplankton biomass, and as an estimate of how much primary production is happening.

Primary production: The amount of carbon dioxide that is being taken up by phytoplankton and converted into organic carbon.  The whole food web depends on primary production, and much of our work is focused on what aspects of the ecosystem control the amount that happens.

Bacterial production: Sort of the inverse of primary production, this is the amount of organic carbon taken up by bacteria.  We can’t measure this directly so we estimate it from the uptake of certain carbon compounds that we can track.

Dissolved organic carbon: One of the most mysterious types of carbon out there (see this article for some indication why).  This is organic carbon in pieces small enough for bacteria to take them up.

Particulate organic carbon: Phytoplankton die, they become particulate organic carbon.  It’s sad.

Bacterial abundance: The number of bacteria in the water, measured on our now operational flow cytometer.

Nutrients: Nutrients in the ocean are operationally divided into macro and micro categories, depending on their biologically relevant concentrations.  We measure nitrogen and phosphorous, the principal macronutrients.

Photosynthetically active radiation (PAR): In addition to nutrients phytoplankton need light to grow.  PAR is the part of the electromagnetic spectrum that can actually be used in photosynthesis.  Too little PAR (like under thick, snow covered ice) and you get very little photosynthesis.  Too much PAR (like at the surface of the ocean during the Antarctic summer) also produces very little photosynthesis!

We’re off to a rough start this season!  Two of our instruments are down, including our flow cytometer – annoying, but we can deal with it – and Colleen’s instrument for measuring superoxide.  That’s a real problem.  Colleen is only with us for five more days.  When she leaves the instrument stays, but we will no longer have a skilled operator!  Measuring superoxide is not trivial and I was supposed to spend a good chunk of this week learning how to do it.  That’s going to be tricky with no instrument.  Fortunately the instrument tech at Palmer this season is handy with a soldering iron and seems to have some ideas.  We’ll see how that plays out tomorrow.

The one piece of good news this week is that the big storm last Sunday didn’t do much damage to the land-fast sea ice near Palmer Station.  At least for now we can do a little science on the ice.  This afternoon Jamie Collins, Nicole Couto, and I went out with the SAR team to establish a sea ice sample site near the station.  Hopefully we can get a couple weeks of sampling at this site before the sea ice deteriorates.

Jamie measures ice thickness. Right about 70 cm in this case; nice thick ice that will hopefully stick around for a while.

Being able to do some science on the sea ice at Palmer Station is actually a pretty big deal and an unexpected bonus for this season.  In some ways this is a very logical place to study ice.  Palmer Station is the United States’ premier polar marine research station, and you can find dozens of papers describing the ecological importance of sea ice in this region.  It’s been years however, since anyone was able to routinely access sea ice from the station.  Considering the amount of ecological research that takes place here this actually seems a little silly; the single most important feature is virtually ignored for practical reasons.  Working on ephemeral, dynamic sea ice requires a set of skills, equipment, and intrepidness that simply doesn’t exist in this day and age within the US Antarctic Program.

The bottom piece of an ice core collected today. It’s early in the season and there isn’t much happening yet. If you squint though you can see the faintest green in the ice, a hint of the algal bloom to come.

Our very small adventure today (on relatively thick, static ice) is reason to hope that that might eventually change.  There isn’t a lot of institutional knowledge about sea ice at Palmer Station, but Station staff and management are open minded and seem eager to learn.  As a further indication the Cold Regions Research and Engineering Lab recently provided new recommendations for sea ice operations at McMurdo Station, a major step toward a rational, data-based policy for traveling and working on ice (which I’ll link it I can find, too tired to search now… must fix flow cytometer…).

Hopefully we can get some good science done on the sea ice this season.  In the Arctic large, under ice phytoplankton blooms are a major source of new carbon to the ecosystem.  In the Antarctic blooms of algae at the ice-water interface are an essential food source for juvenile krill – adult krill being the major food source for virtually everything else down here.  Getting some indication of when, where, and how often these events occur along the West Antarctic Peninsula will tell us a lot about how these ecosystems function, and what will happen to them as the ice season and range continues to decline.

And in case you ever have to track a penguin, this is what penguin tracks look like.

We arrived at Palmer Station last Thursday morning after a particularly long trip down from Punta Arenas. Depending on the weather the trip across the Drake Passage and down the Peninsula to Anvers Island typically takes about four days. This time however, the Laurence M. Gould had science to do and a NOAA field camp to put in at Cape Shirreff on Livingston Island. This was a particularly welcome event as it gave us an opportunity to get off the boat and get a little exercise unloading 5 months of supplies for the NOAA science team.

Since arriving at Palmer Station the activity has been nonstop. In addition to lab orientations and water safety training there is the seemingly never-ending job of setting up our lab and getting instruments up and running. Yesterday evening following the weekly station meeting we did manage to go for a short ski on the glacier out behind the station. I’m glad we did because today the weather took a real turn for the worse; winds are gusting to 55 knots and strengthening. This is a real concern for us because wind strength and direction are the primary determinant of the presence and condition of sea ice in this area. As I wrote in my previous post we are hoping for sea ice to be either very solid, so we can sample from it or clear out completely, so we can get the zodiacs in the water. We’ll have to wait until the storm passes to see what conditions are like but very likely it will be neither!

A derelict steel-hulled sailing vessel beached outside of Punta Arenas (taken in 2013 on my last trip to Antarctica). Before the Panama Canal opened Punta Arenas, located on the Strait of Magellan, was an important stopping point for ships sailing between the Atlantic and Pacific. Today the city is best known as the jumping off point for cruise ships (and research vessels) heading to Antarctica, and as an access point to Chile’s Torres del Paine.

A moderate swell breaking on the side of the Gould as we leave Tierra del Fuego behind. Overall it was an extremely mild crossing of the Drake Passage, which didn’t prevent me from getting sick (as per SOP).

As we crossed the Antarctic Polar Front the weather got noticeably colder. Here, sea spray freezes on one of the Gould’s spotlights.

A welcome diversion was the NOAA field camp put-in at Cape Shireff. This included such antics as raising (sans crane) a four-wheeler from a bobbing zodiac onto a six-foot high snow berm. Don’t ask me how it was done; I was there and I’m still not sure. In this photo you can see the Laurence M. Gould in the background and a zodiac bringing in another load of supplies.

The Gould picks its way towards the pack ice. I’ve only been on two ships in sea ice and the experiences couldn’t have been more different. Back in 2009 I sailed in the Arctic onboard Oden, a powerful Swedish icebreaker. We smashed ice a meter thick and more day and “night” (it was summer) for six weeks straight. The Gould is a different sort of animal. It isn’t a true icebreaker and, if winds and currents conspired against it, could become trapped in rafting ice. Moving the Gould into even thin ice is a a delicate process.

Science in action! There were two science parties conducting research on the way down. One is studying the distribution of krill in the Drake Passage. The other is studying the response of deep water corals to ocean warming. Here graduate student Caitlin Cleaver from the University of Maine washes corals freshly collected from 700 meters deep. The corals were transported live to Palmer Station for further experiments.

Yesterday morning the Laurence M. Gould raised its gangplank and departed Palmer Station.

Jamie and Colleen take a break from lab setup for a hike on the glacier behind Palmer Station (seen in the background).

Today started calm with grey skies, conditions deteriorated with astonishing speed after lunch. Within just a few minutes winds went from a study 20 knots to gusting to 55 knots (63 mph).

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.

Electron configuration of superoxide. The extra electron is one more than oxygen can handle, and makes the molecule highly reactive. Image from https://commons.wikimedia.org/wiki/File:Superoxide.png.

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.

In 2 and a half months, and unless there’s another government shutdown, I’m heading down to Palmer Station to collect a key set of samples for one of my projects.  The idea is to time this sampling effort with the spring diatom bloom.  This bloom is a critical pulse of fixed carbon into the ecosystem after the dark (sub)polar winter, and is followed by a series of blooms by lesser phytoplankton players – cryptophytes, dinoflagellates, and Phaeocystis.  The problem with this plan is that it is pretty much impossible to guess when the spring bloom will happen.  Ecologically speaking it happens as soon as the ice retreats (or rather, as the ice is retreating), but this can vary by many weeks from one season to the next.  The problem is compounded by the sampling strategy at Palmer Station.  Scientists at the station rely on zodiacs for sampling; those ubiquitous inflatable craft that, while surprisingly durable, are pretty useless in even very light ice conditions.

So one thing we would very much like to know is what the ice conditions will be like in mid October when we arrive on station.  A good place to start a discussion of likely ice conditions is, surprisingly, the tropical Pacific.  The tropical Pacific is a mess right now.  There’s a tremendous amount of heat in the surface ocean and cyclones have been pinging around the South Pacific for the last few weeks like a bunch of bumper cars.  This is the result of a strong El Nino taking shape, possibly the strongest we’ve seen in over a decade.

From www.weatherunderground.org. Sea surface temperature anomaly on August 4, 2015. Warm areas indicate sea surface temperatures that are warmer than normal. Notice the large amount of heat in the Pacific, particularly along the equator extending out from Ecuador. This is the result of suppressed upwelling and will probably, among other things, lead to a very poor anchovy catch in Peru this year… Note:  When I published this post I thought I had dropped this image in as a static image, instead it posted as a link.  The (static) image shown is from a few days after this post was published.

The El Nino Southern Oscillation (ENSO) is a tropical phenomenon with global consequences.  One of these is reduced sea ice extent along the West Antarctic Peninsula (WAP).  During an El Nino the polar jet (the analogous to the northern hemisphere’s jet stream) is weakened and there is less transport of heat from the subtropical Pacific to the WAP.  During La Niña the opposite happens; the jet strengthens, driving warm, wet storms south across the Southern Ocean to the WAP.  The strong winds break up the ice and the heavy snow and rain has a pretty bad effect on Adélie penguin chicks, occasionally causing total breeding failures.

ENSO’s not the only pattern of climate variability with an impact on Antarctic sea ice, however.  The Southern Annual Mode (SAM), also called the Antarctic Oscillation (AAO), has a major impact on sea ice extent.  Unlike ENSO, which is the result of complex dynamics between the atmosphere and the ocean, SAM is primarily an atmospheric phenomenon linked to the magnitude of the north/south pressure gradient across the Southern Ocean.  This differential controls the strength of westerly winds that help deliver subtropical heat to the West Antarctic.  SAM has two phases; positive and negative, and can hold one phase for weeks or months, then suddenly shift.  During its negative phase SAM is correlated with reduced westerly winds and increased sea ice along the WAP (and happy penguins).

Right now SAM is in a positive phase, and has been for some time.  But we’ve also got an uber El Nino.  So what does that mean?  I asked Sharon Stammerjohn, a physical oceanographer with the Palmer LTER project, what happens in these situation.  Sharon and several colleagues wrote a paper in 2008 exploring the impact of SAM and ENSO on Antarctic sea ice extent.  It’s pretty clear what happens if a La Niña lines up with a positive SAM (low ice year), or an El Nino coincides with a negative SAM (high ice year).  But what about a positive SAM and a strong El Nino?  In that case it can, apparently, go either way.  Either the strong subtropical storm effect will overcome the weakened polar jet or it won’t.  To get a sense of which is winning so far this year we can take a look at the the NSIDC’s current map of Antarctic sea ice extent.

Taken from http://nsidc.org/data/seaice_index/. Antarctic sea ice extent for July 2015. Right now it’s shaping up to be a big ice year for the West Antarctic Peninsula.

Ouch, take a look at the northern tip of the WAP.  The pink line is, as the figure indicates, the median sea ice edge.  Clearly El Nino is winning; most of Antarctica is normalish, but the WAP region has some extraordinary ice cover right now.  Sea ice has been more or less on the decline there for the last couple of decades, it will be very interesting to see what kind of impact this has on the ice-dependent WAP ecosystem.  Of course sea ice that far north is pretty fickle; the SAM could switch modes, or the westerlies could increase, and the sea ice could breakup and move out before spring.  Otherwise it looks like we might be sampling from the Palmer dock…