Tuesday, January 16, 2018

Long live polar invertebrates

Friends, I love polar regions. I love the cold, dry air. I love the wind. I love the constant daylight and the constant darkness and the challenges of working at the end of the earth.

And I love the biodiversity.

Polar regions are renowned for the breadth of animals they possess. I'm not talking about polar bears and penguins (you know me better than that). I'm talking about the animals underwater, on the bottom of the sea. Polar benthic invertebrates have extremely high diversity - more than you would ever expect. You see, oceans in both the Arctic and Antarctic have low temperatures and low productivity, characteristics suggesting that very little would grow there. But exactly the opposite is true. The seafloor in both polar regions is covered by an incredibly diverse array of fauna. In fact, the colder areas are the ones with the highest diversity, to the point that a single trawl could supply an invertebrate zoology class.

Animals collected by divers in McMurdo Sound
How in the world could such an array of invertebrates live in such cold temperatures and with such little food? It's actually an important research question that I intend to pursue. I got one hint a few years ago, and you might remember it if you were following this blog during my Svalbard recruitment experiment. I put out plastic panels in Arctic fjords to see what would grow, and the site with the highest biodiversity of adults had the lowest number of recruits. I started thinking that the invertebrates in the cold fjords might have long life-spans - sure, they grow slowly, but if they all live a long time, then there will always be a lot of them around.

I'm anxious to test out my ideas in the Antarctic, because the biodiversity in McMurdo Sound is absolutely incredible. Some divers from the station collected animals for us, which are currently living in seawater tanks in the Station's main lab. There are sponges and soft corals and sea stars and scallops and slugs and anemones.

Because it's so cold and dark under the ice, the conditions are similar to the deep sea, and there are actually many taxa living at shallow depths in Antarctica that are usually only found in the deep sea. For example, the soft coral you see in the photo above is called Gersemia antarctica. It's closely related to another species, Gersemia fruticosa, that lives on the continental slope of the north Atlantic, far offshore and at much greater depth.

Sea stars from McMurdo Sound
Much of the seafloor in McMurdo Sound is covered by large sponges, and you'll see a couple examples in the photo above. The sponges are called "foundation species" because they form the base of a flourishing ecosystem. Their large physical structure provides shelter for other animals, and they also serve as an important food source, especially for sea stars. There has been several studies on McMurdo sponges since the 1970s, but I can't help but imagine what experiments I would like to do in the future. The high biodiversity of benthic invertebrates in polar regions makes for gorgeous and fascinating communities. Long live polar invertebrates!

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