Wednesday, July 8, 2015

I usually post about the results of our experiments as they are published. This time, I don't have to post, because it was covered by a reporter! You can read about some of our research on soil CO2 on Nature World News, where we show that the movement of CO2 into and out of soils is impacted by water source, as the result of both geochemistry and soil microorganisms.

Here are some photos that show you the equipment we used to make the measurements in a couple of the wet locations we studied:

The LI-COR machine in one of the permafrost seep patches

Me using the LI-COR in an area along the edge of Lake Fryxell
These results are published in the paper:  Ball, B.A. and R.A. Virginia. 2015. Impact of physical and biological drivers on diel cycles of soil CO2 flux over moisture gradients in a polar desert. Antarctic Science. doi:10.1017/S0954102015000255

Tuesday, June 2, 2015

The chemistry of penguin poop

In the past, I have posted about working in the penguin rookeries. Most people associate penguins with ice and water, but Adélie penguins nest on land. Their nests can change the soil, because where penguins nest, they poop! You can see that poop (called guano) in the photo below. It is sort of pink-colored because of the krill that the penguins eat.
Bird guano contains a lot of phosphorus and nitrogen, so it adds a lot of important nutrients to the soil. Guano also has a lot of carbon, which all living things need for energy. It is very easy to see that some of the soil will be different, because some areas of the rookery have a lot of guano (and are very pink), and other areas do not. It's like fertilizing part of your garden, but not the whole thing, which would mean plants would grow better only in the part that's fertilized.

However, guano isn't a perfect fertilizer that makes the soil "better". It has a lot of nutrients, but too much nutrients can become toxic for soil organisms. Also, guano is very acidic, which is also hard for soil organisms to live in. Plus, the guano can dry into a very hard layer over the soil, which you can see in this video. Ross had to work hard to get the soil sample!

video
(You will also notice that a penguin rookery is a very noisy place to work! It's also smelly!)

The impact that birds, such as penguins, have on soil is called the ornithogenic impact. "Ornitho" is a term that refers to birds. (Ornithology is the study of birds.) "Genic" means "produced by". So, ornithogenic soils are soils that are heavily influenced by birds. We studied the ornithogenic soils in penguin rookeries. A lot is known about ornithogenic soils in penguin rookeries along the Antarctic Peninsula, but less is known in the relatively colder and drier climate of the McMurdo Sound region. (Check out the map below.)

We worked in three different rookeries on Ross Island in McMurdo Sound. The rookery at Cape Royds has the smallest colony (about 2,000 mating pairs of Adélie penguins). The rookery at Cape Bird is mid-sized (about 35,000 mating pairs), and the rookery at Cape Crozier is the largest (about 120,000 mating pairs). That's a lot of penguins creating a lot of guano!! We wanted to know if the penguin influence on the soil changed with colony size.

At each rookery, we studied soil that was either heavily influenced by the penguins by sampling right in their main nesting area (the pink spots). We also looked at soil that received less guano by sampling in lines from the nesting area all the way to soils outside the rookery area. The red lines in the photo below show some of our transects, going from the very pink (high activity nesting) areas into the gray soil where penguins walk but don't nest. We also sampled where I was standing, outside of the colony with no penguin guano. This way, we could find out how much penguin activity is needed to see a big change in the soil.

So what did we find? Soils with a lot of penguin guano (in the pink-colored nesting areas) had more carbon, nitrogen, and phosphorus than areas with low or no penguin activity. That's exactly what we would expect, since guano contains those nutrients! We also measured more respiration from the organisms living in the soil with a lot of guano. So, these nesting areas are "hotspots" where the extra nutrients allow soil organisms to be more active.

Even though guano adds a lot of carbon in the soil that wouldn't be there without the penguins, the microscopic soil organisms are still carbon-limited, meaning they have more nitrogen and phosphorus at their disposal than carbon. They're always looking for more carbon! We thought that the large amounts of guano would give them all the carbon they need, but it didn't!

We also learned that the size of the colony did not make a big difference for soil nutrients. It was a matter of penguin activity within the rookery, not the size of the colony that changed the soil the most. In other words, it didn't matter whether there were 2,000 or 120,000 mating pairs. If there was a penguin nesting area with a lot of guano, there were more nutrients and soil respiration.

These results are published in the paper:  Ball, B.A., C.R. Tellez, and R.A. Virginia. 2015. Penguin activity influences soil biology, biogeochemistry, and soil respiration in rookeries on Ross Island, Antarctica. Polar Biology. doi: 10.1007/s00300-015-1699-7

Tuesday, May 5, 2015

What do we do with the samples we ship home?

While we were in Antarctica earlier this year, we were able to do some of the analyses we need to measure on the soil we collected. However, we don't have the time or equipment to do everything we need, so all of our samples were boxed up and shipped back to Arizona.

I flew home on an airplane in mid-January, but my samples stayed at Rothera until one of the U.S. research vessels came to pick them up. The samples traveled by boat to the U.S. research station, then eventually on to Chile. From there, they were carefully packaged and flown to California. From there, they were carried on a truck to my lab at Arizona State University. I received many boxes that looked like this!
The soil samples were packaged with a lot of cryogenic material so that they remained frozen throughout the whole trip. They were immediately put into a -20°C freezer in my lab. Here are the samples, finally home-sweet-home!
Now that the samples have arrived, we are able to finish our analyses on the soil. It will take a long time to get through everything we need to measure, but we've already made good headway! Most of these analyses are being done by one of my students, Connor. The first analysis he's conducting measures the mineral forms of nitrogen in the soil. "Mineral forms" of nitrogen include ammonium (NH4+), nitrate (NO3-) and nitrite (NO2-). We want to know how much mineral nitrogen is in the soil, because those are the nitrogen compounds that plants and animals are able to consume. Here are some photos of Connor working hard in the lab to extract soils for nitrogen:
Connor mixes a big jug of potassium chloride solution.
Connor weighing soil samples into flasks for the extraction.

Connor filtering an extracted solution to remove the soil particles.

Friday, March 27, 2015

How water tracks influence soil biology: the results

You might remember the field work we were conducting a couple years ago on water tracks. (You can read more about them in my posts from October 2012.) Water tracks are a type of groundwater where water from melting ice trickles down through the soil and moves along the permafrost, kind of like slow-moving underground streams.
Water tracks are a common feature in the McMurdo Dry Valleys, but we actually don't know much about how they change the soil they're flowing through. The water they bring would of course be important for the soil organisms living in an otherwise very dry desert. But they also bring a lot of salt, which can mess with the osmotic balance of the organisms, making it hard for them to survive. (Just like how animals living in freshwater have a hard time surviving in the ocean.) We wanted to know what the net impact is of these water tracks on soil biology. Is life better for them in a water track, or does it harm them?

In December 2012, I collected soil samples from inside and outside of three different water tracks. Those soil samples were shipped back to Arizona State University, and we measured a lot of important chemical properties of the soil.We measured the pH, salinity, and nutrient levels. We also measured the "texture" of the soil, which refers to the size of the soil particles. In other words, is it very sandy soil or is it made of finer particles? We also measured the amount of bacteria and fungi in the soil, and how much CO2 is being respired from the soil.

Overall, we learned that water tracks can have a big influence on soil, changing the water availability (obviously), salinity, amount of carbon, and texture. Those changes in the soil relate to changes in the microbial biomass and the amount of CO2 respired from the soil. In the graphs to the left, you can see that position "A", which is outside of the water track, is drier and less salty. It also has a higher pH than the other positions inside the track.

Also, Position "A" outside the track respires more CO2 and has more bacteria living in the soil.

However, this is just for one of the water tracks. As it turns out, each water track was different, so we can't assume that they'll all change the soil in the same way. They might hinder the soil microbes, or they might promote them. That means that, if the climate gets warmer in the Dry Valleys and more water tracks appear, we can't predict exactly what will happen. Some water tracks will stimulate biology, and some will hinder it.

The citation for the paper publishing these results is:
Ball, B.A. and J. Levy. 2015. The role of water tracks in altering biotic and abiotic soil properties and processes in a polar desert in Antarctica. Journal of Geophysical Research: Biogeosciences.  120: 270-279.

Monday, January 19, 2015

Now that I'm home... some videos!

I made it back to Phoenix, Arizona last week according to schedule. It was a long journey, taking about 25 hours total. When I got home, I came down with a cold! (This is funny, since I was going from a cold place to a much warmer place. Night-time temperatures in Phoenix are warmer than day-time temperatures at Rothera!)

Now that I'm back home and have fast internet, I want to share some video clips with you that I wasn't able to upload from Rothera Station.

First, some wildlife! There were a lot of elephant seals around Rothera. Most of them are juvenile males, and they spent a lot of time bickering with each other (practicing for when they're adults that will want to rule a beach). When they weren't scuffling with each other, they were lying around looking lazy! Here's a video of some of their behavior. Be sure your sound is on so that you can hear them.
video

And some tinier wildlife! This is a video Uffe took when he found a crowd of springtails in a puddle. They're doing what's called "rafting". They hold onto each other in a bundle and float on water. We were often surprised by how many springtails we found at the sites!
video

A lot of our sampling sites were on nearby islands, and we took a boat to visit those sampling sites. Here's what it's like to be on a boat in Marguerite Bay, Antarctica:
video


Saturday, January 10, 2015

Back in Punta Arenas, Chile

After almost two months at Rothera Station, we have begun the journey back home. We flew from Rothera back to Punta Arenas, Chile.

While we are here, we are returning the cold-weather clothing to the U.S. Antarctic Program headquarters. We are also enjoying meals made out of fresh food, especially fruit and vegetables!

Soon, we will continue our journey home, and I will spend about 24 hours flying back to the U.S.

Tuesday, January 6, 2015

Wrapping up the Field Season

We've been spending a lot of time on the microscopes looking at our samples. We are interested in the invertebrates living in the soil. At Rothera, we've only been able to look at the larger invertebrates, such as Springtails and mites. The smaller invertebrates (the nematodes and rotifers) require higher power microscopes, so we will look at those from our labs at home.

Here's some of what we've seen:
Collembola, also known as Springtails
We've found a LOT of springtails. Many of the samples from the islands near Rothera have thousands of springtails in them! Here's what we saw in the field:
Springtails "rafting" in a puddle of water

There are also a lot of mites in the samples, but they are not nearly as numerous as the springtails.
Oribatid mites
Other than microscope work, for the past few days, Uffe and I have been packing up to leave. We are scheduled to leave Rothera in two days! We have carefully packed up our samples and science gear to be shipped home. The lab has been cleared out and cleaned up, and we've put away all of our field gear. The end of our season is near! On Thursday, we will hopefully be boarding the Dash 7 to return to Punta Arenas and begin our journey home.