A Snippet of Science at Cinder Cones Seep

Yesterday, we were excitingly able to put a new dive hole into Cinder Cones Seep. Cinder Cones is quite a special place, as it was the first site in Antarctica to show active methane seepage in 2011 and has been studied over the years since by the Cold Dark Benthos group. Given this, we have a number of observations and discoveries at this site that I would love to share with you, each more interesting than the last! In this post I will give you a few (non-exhaustive) examples of what has been found there over the years. This post will be largely microbial, but there is fascinating science being done up the entire food web.

One of the major questions at the site was whether anaerobic methanotrophs would show up at the site, as these microbes are largely responsible for filtering methane out of the seafloor across the rest of the globe. The initial response from 2012 to 2016 was indeed largely microbial, and the anaerobic methanotrophs we know to filter methane in other environments were observed.

Figure in Andrew's original Cinder Cones Paper titled: "Riddles in the cold: Antarctic endemism and microbial succession impact methane cycling in the Southern Ocean." In this paper he describes the microbial response to methane seepage at Cinder Cones and finds that anaerobic methanotrophs coupled to sulfate reducing bacteria are present. This process produces a lot of sulfide as a byproduct, leading to these white mats full of sulfide oxidizing bacteria on the seabed.

In 2022 and 2023, upon return to cinder cones the lab discovered that microbial mats were much sparser, replaced by an incredibly dense bed of anemones in their place. However, even though the microbial mats were absent, we continued to observe both methane seepage and methane use by the microbes in the seafloor.

Cinder cones a few days ago. The white dots on the seafloor are all anemones, blanketing the locations where the white microbial mats used to be!

Through experiments on the sediment, we found that the microbes responsible for filtering methane here likely shifted from those that couple with sulfate reducers to the archaeon Methanoperedens nitroreducens, and the bacterium Methylomirabilis oxyfera. One of the important parts of this finding is that the division time of these two microbes is much faster, and they can therefore respond to a new methane seep in a shorter time frame. This year we continue to explore these dynamics through observation, collection, and experimentation. I look forward to sharing more throughout the season and can be certain of one thing: things are never what you expect down here.

The Antarctic diver's door into the abyss

At the beginning of each season, the whole McMurdo village join forces to make the first 4x4 ft diving holes in the sea ice. From the Carpenter to the sea ice safety team, we all drive over the frozen Ross Sea early in the morning to what will be our main study site: Cinder Cones.

After an hour drive in the Pisten Bully, we are greeted at the Cinder Cones site by a giant 20ft+ drill ready to pierce through the frozen sea surface. Two meters into the sea ice and a few minutes later, access to water is achieved!

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A dance already practiced over the years starts quickly after, with the modified Pisten Bully taking the snow away from the dive hole, followed by the Carpenter's vehicle with the Fish Hut. Once the Fish Hut is in place, a heater is quickly turned on, and the team starts shoveling snow around it to secure its place for the season. And just like that, the Antarctic diver's door into the Ross Sea is open!

A different site - Pearse's Casing

Many of the dive sites we visit have been visited for a long time. This particular one is called "Pearse's Casing" after amazing invertebrate biologist John Pearse, who spent early years working here. He and his partner Vicki were a powerhouse of science and knowledge for a generation of scientist (or 2!) and were also among the most lovely people. The casing is nothing to write home about, it collapsed a few years ago, but the site remains very pretty and always makes me think of John and Vicki.

The spot is much lighter than the other research site and the ice runs deep down the slope. This is an area that has lots of anchor ice that will pull the sponges out of the seafloor - often down to more than 40ft or 15 or so meters.

We are very early in the season, so the ice is incredibly blue. As the season progresses into spring the algae will start grow and turn the light more of a greenish color. Only our lights really make the colors pop on the crazy life forms.

Here is an example of some of that colorful life. This is a Perknaster seastar eating a sponge. This species is a predator of sponges (among other things). They are also much more slimy than the other species that are common in the sound.

The diversity is pretty amazing at this site as well. This hydroid always reminds me of hair as it is incredibly fine and stark white in contrast to many of the other species present.

And then there is the green sponge! Not many species end up with such a luxurious green color. This one also looks very plain until we shine light on the subjects.

While the photos may make it seem light, and it is compared to the other sites, most of our dives are spent in near darkness with only the shadows of our dive buddies keeping us company in the crystal clear water of winters end.