The north side of north

The past few days, we have sampled at the northern HAUSGARTEN stations. Honestly, it feels a bit weird to say "the northern stations" because, well, we're in the Arctic. Every station is a northern station in a way. But further north we went, to nearly 80 N. 

Johanna deploying our larval net while I 
manage the line. 

The ice at the northern stations is different from East Greenland. It's thinner, more delicate, ridden with holes and so, so blue. From the ship, you can watch the ice floes crack and break under the strain of the hull. They act like soft cotton compared to Polarstern's sturdy steel. As we drive between stations, the ice floes make the ship's motion bumpy, like so many pot holes on an uneven country road. If East Greenland ice is a deep January freeze, the northern HAUSGARTEN stations are a slushy day in late March. 

The ice edge is one of the most productive ecosystems on Earth, at least for a short time. Each spring, as the ice begins to melt, it releases specialized algae that live within the matrix of the ice. These sea ice algae begin multiplying and spark a bloom. Meanwhile, a lens of cold, fresh melted ice water covers the surface of the ocean, stabilizing the water column. Sometimes, nutrient-rich water from below the ice wells up to the surface. These conditions are perfect for phytoplankton, and an intense bloom ensues in the 24-hour sunlight. 

Copepods emerge from the depths where they overwinter to feast on the ice edge bloom. But what about larvae? Many species, even deep-sea species, send their larvae to the surface, because that's where the food is. If a larva can feed on phytoplankton in surface waters, it requires less energy investment from its mother, and mom can subsequently produce more offspring. I was really excited to see how many larvae we caught at the ice edge. 

A mitraria larva of Galathowenia oculata, photographed at 
50x magnification using a compound microscope.

Believe it or not, we actually had some new species of larvae in our northern samples - species we had not seen at stations further south. There was an ambiguous green embryo and a fast-swimming orange ribbon worm. We'll have to sequence their DNA to figure out who they are.

Probably my favorite species that we collected at the northern stations is Galathowenia oculata, a tiny worm that lives in the muddy seafloor. Galathowenia larvae are spiky. Their small bodies hold dozens of iridescent blue spikes that can either lay flat or be fanned out into an ominous ball. For many larvae, defensive anatomy is a must. They're so tiny and are such weak swimmers that they will never escape a predator's mouth. Their best chance at survival is to avoid getting chomped in the first place - by poking their predators in the face. 

We are closing in on 250 larval samples, and I'm grateful for the beautiful animals we found at the northern stations!