More on Anchor Ice

Anchor ice, as Rowan explained in her post, is really pretty and the ocean freezing in front of us. It is also a great disturbance that leads to the seafloor ecosystem being pretty different than many places. The depth of sea ice formation is anywhere from around 10m (30ft) to in pretty cold years, 20m (60ft). This year it is down to around 54 ft. The reason why this impacts the community is that as the ice forms, it grows on anything that it can and especially sponges.

Here you can see the sea ice forming on this sponge (Homaxinella balfourensis). This fast growing sponge will grow and cover the seafloor until it is removed by predators or anchor ice.

The sponge community here is very dynamic with sponges that live hundereds to maybe thousands of years. And others… particularly one Homaxinella balfourensis that grow quickly but are also grazed upon and removed. Above is an images of a field of Homax (as I call them) but covered in anchor ice that is slowly acting like a baloon to pull them up to the surface ice.

Here is a Homax colony that is not long for this world. It has been floated up to the surface by anchor ice, pulling a soft coral and some mud with it. All will be frozen into the ice and be no more.

In the deeper areas, the long lived sponges dwell. We have studied these in the past and know that they grow to the size of a baseball in ~10 years or so but they reach huge sizes and have age estimates in the centuries not decades.

This vibrant community of sponges and other invertebrates (like Lila talked about in her post) grow deeper than the anchor ice can get meaning they can live for a very long time without ice removing them. Unless an iceburg comes along. Then they are frozen toast.
As a parting shot – Here is Rowan peering at all the different bits of life that have been pulled off the seafloor and frozen into the ice above.
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