By now you have been following along as we collect water samples, water chemistry data, phytoplankton samples and zooplankton samples from the waters to the west of Svalbard, and from the ice bands that we have encountered along the way. It has been a real privilege to be here in this environment, and to sample the ecosystem while surrounded by the incredible beauty and serenity of the scenes around us. And then, finally, yesterday we were able to connect all of these dots with some higher predators (all very exciting!).
…but before that, let’s back up and recap what we were doing here: The goal of this cruise was to link physics with oceanography and biology. You can think of this as a stepwise function, from the forces that influence the weather and the ocean, to the characteristics of that ocean water (and ice), to the phytoplankton that act as the first step in the marine food web, to the zooplankton (which rely on those phytoplankton for food), and finally the predators of zooplankton, including fish, seals and whales – all within the context of our changing climate.
My role (which was Hillary’s job in the first half of the cruise) was to survey for marine mammals in association with the ice and water conditions that my fellow science team members were collecting and measuring, and also to examine the zooplankton samples. Below you can see an example of the zooplankton from one of the tows, viewed under a microscope.
Most of the animals in the image are copepods: tiny crustaceans that are fed upon directly by some whales, and indirectly by other whales, seals and seabirds after they have first been consumed by fish. In the larger copepods you can clearly see a clear yellow tube running through the body. This is the oil sac, where copepods store a lot of lipid – and this is what makes them so energetically valuable for predators. Lipids (fats) have twice the energy content of the same amount of either carbohydrates or proteins, which makes them ideal for energy storage (this is why fats are the storage material of choice for animals preparing for energetically demanding activities such as reproduction or migration, all the way from birds to polar bears). In some of the copepods you can also see a greenish compartment, indicating that they have been grazing on phytoplankton (ah! The link between the two plankton groups finally appears!).
I will tell you that it has been a fairly quiet ocean from the marine mammal perspective. Hillary and I have been surveying during this entire trip, along with help from the bridge crew during night watches or when we were busy sampling. Until yesterday we had only spotted a few whales and some seals, despite hours of gazing at the sea (I will say, though, that my first bearded seal sighting made me very happy). But after we finished with the open ocean and ice band sampling, we had the opportunity to spend yesterday (May 21) in a fjord north of Longyearbyen.
There, at the edge of the ice below a glacier, we encountered a group of ~30 belugas. These animals were surfacing to breathe right at the ice edge, then swimming back under the ice, presumably to forage on Arctic cod and other fish species below. We spent about half an hour with them, watching and listening as they cruised back and forth, repeating their forays under the ice and returning to breathe. All you could hear was the sound of water breaking and whales breathing. This was a very fitting end to this cruise, and one that allowed us to come full circle and tie all of our links together.
-HK
