First Talk on Science Results
I've given several talks to friends and colleagues about my experiences in Antarctica, but I gave my first talk on the scientific results at the Astrobiology Science Conference in League City, Texas, yesterday. It was well received and I got some good questions. Here are my slides:
My talk followed two on the Endurance robot that was exploring Lake Bonney down the valley from us at Lake Joyce. I claimed that Ian and Dale were highly sophisticated observers that beat out any robots.
It's important to say where you were.
And to describe the regional context.
Lake level rise is one of the big stories. The yearly data until the 80's are from surveys by NIWA, whereas the lower graphs show the depth of the salty layers in three different years, including our data. Both show that lake levels are sometimes stable for years and often rise rapidly.
I started with the shallow mats and worked my way deeper. Chla is the concentration of chlorophyll a. AFDW is the ash free dry weight which is an approximation of the biomass. Both are per unit area of mat and extend from the top surface to the bottom of the active part of the mat. That thickness increases with depth, so the AFDW increases with depth. However, Chla is low except for in this shallowest sample.
Deeper mats have more structure, more biomass, and less chlorophyll.
They are not photosynthetically very active, though, because we could not detect any O2 production in them. Photosynthesis produces O2 (at least this type of photosynthesis).
These two images show a mat that is falling apart (left) and part of the same mat showing that the bacteria aren't even capable of doing much photosynthesis. The point where 3 ridges come together in the green image is also in the upper part of the tan image. It's rotated a bit, though.
This is one of Dale's beautiful photographs (and no it isn't a painting!) I showed it mostly because I love it, but you can also see little pink lines on some of the ridges. Those are some of the "happier" bacteria that can do a bit of photosynthesis.
Most of the peaks, though, are coated in rock flour, which is bits of rock ground up by the glaciers. The peaks have flopped over. They are not very active microbially except in the pinker areas.
Again, the bacteria aren't capable of much photosynthesis.
The calcified structures are much taller than the mats at shallower depths, but they aren't happy.
This is a sample we brought to the surface. The tan color is due to rock flour and a lack of chlorophyll.
This is the first sample I dissected. All the calcite pieces on the right came out of the structure on the left. It is the calcite that held the column up. However, it did slump after sampling because the calcite pieces shifted relative to each other during sampling. I froze some samples like this, and we'll do some x-ray computed tomography (a 3d imaging technique) to see how all the calcite pieces fit together inside the structures.
In some samples, there are thin rods of calcite in photosynthetically active peaks. You can see the darker calcite rod in the largest peak in the right image. The image on the left shows the concentration of chlorophyll, and the tallest peak is the same one visible in the right image. We are going to try to see if there is evidence that photosynthesis helps the minerals form.
We have a number of interpretations. The first is that the tall, deep structures need that calcite to be tall, and that they weren't always this shape.
The second interpretation is that the tall structures don't get enough light to recover. If they are going to start growing again, the ice on the lake has to become clearer.
The next interpretation waffles. We know that the shape of the mat changes with depth, but the deeper mats have more biomass. Thus, we do not yet know if the difference in shape is due to differences in depth or differences in biomass. I can make up good, logical arguments for either interpretation. I also don't know how we are going to sort this out yet. We need to develop some hypotheses about what would be different for these two models, things that we can look for in the field.
We do know that most of the mats grew when conditions were more favorable. If you compare this year's mats with those that Dale saw in 1997, they look in bad bad shape.
The end...
By the way, we just got our samples from Antarctica two weeks ago. They took a long ride back on the ship. Tyler is hard at work describing the calcite!
My talk followed two on the Endurance robot that was exploring Lake Bonney down the valley from us at Lake Joyce. I claimed that Ian and Dale were highly sophisticated observers that beat out any robots.
It's important to say where you were.
And to describe the regional context.
Lake level rise is one of the big stories. The yearly data until the 80's are from surveys by NIWA, whereas the lower graphs show the depth of the salty layers in three different years, including our data. Both show that lake levels are sometimes stable for years and often rise rapidly.
I started with the shallow mats and worked my way deeper. Chla is the concentration of chlorophyll a. AFDW is the ash free dry weight which is an approximation of the biomass. Both are per unit area of mat and extend from the top surface to the bottom of the active part of the mat. That thickness increases with depth, so the AFDW increases with depth. However, Chla is low except for in this shallowest sample.
Deeper mats have more structure, more biomass, and less chlorophyll.
They are not photosynthetically very active, though, because we could not detect any O2 production in them. Photosynthesis produces O2 (at least this type of photosynthesis).
These two images show a mat that is falling apart (left) and part of the same mat showing that the bacteria aren't even capable of doing much photosynthesis. The point where 3 ridges come together in the green image is also in the upper part of the tan image. It's rotated a bit, though.
This is one of Dale's beautiful photographs (and no it isn't a painting!) I showed it mostly because I love it, but you can also see little pink lines on some of the ridges. Those are some of the "happier" bacteria that can do a bit of photosynthesis.
Most of the peaks, though, are coated in rock flour, which is bits of rock ground up by the glaciers. The peaks have flopped over. They are not very active microbially except in the pinker areas.
Again, the bacteria aren't capable of much photosynthesis.
The calcified structures are much taller than the mats at shallower depths, but they aren't happy.
This is a sample we brought to the surface. The tan color is due to rock flour and a lack of chlorophyll.
This is the first sample I dissected. All the calcite pieces on the right came out of the structure on the left. It is the calcite that held the column up. However, it did slump after sampling because the calcite pieces shifted relative to each other during sampling. I froze some samples like this, and we'll do some x-ray computed tomography (a 3d imaging technique) to see how all the calcite pieces fit together inside the structures.
In some samples, there are thin rods of calcite in photosynthetically active peaks. You can see the darker calcite rod in the largest peak in the right image. The image on the left shows the concentration of chlorophyll, and the tallest peak is the same one visible in the right image. We are going to try to see if there is evidence that photosynthesis helps the minerals form.
We have a number of interpretations. The first is that the tall, deep structures need that calcite to be tall, and that they weren't always this shape.
The second interpretation is that the tall structures don't get enough light to recover. If they are going to start growing again, the ice on the lake has to become clearer.
The next interpretation waffles. We know that the shape of the mat changes with depth, but the deeper mats have more biomass. Thus, we do not yet know if the difference in shape is due to differences in depth or differences in biomass. I can make up good, logical arguments for either interpretation. I also don't know how we are going to sort this out yet. We need to develop some hypotheses about what would be different for these two models, things that we can look for in the field.
We do know that most of the mats grew when conditions were more favorable. If you compare this year's mats with those that Dale saw in 1997, they look in bad bad shape.
The end...
By the way, we just got our samples from Antarctica two weeks ago. They took a long ride back on the ship. Tyler is hard at work describing the calcite!
