Hello again

It has been 5 years. 

Back in 2019, I started a series of experiments at a station in the HAUSGARTEN. We call the station "Senke," but that's actually a misnomer. "Senke" is German for "depression." There is a depression in the seafloor, sure, but right next to the depression is a giant rocky reef. And I go to Senke for the reef. 

It's been my mission for the last several years to understand the assembly of hard-bottom communities in the Arctic deep sea. How are new stones colonized? Who arrives first? Where do the larvae come from? Ever since an 18-year experiment showed that Arctic communities take decades to form, I have wanted to dig into that process. 

One of my larval traps, successfully opened and even
covered with life!

If you want to understand hard-bottom communities, Senke is the ideal study site. It has bedrock and boulders and is covered in sponges like you wouldn't believe. I find it fascinating and incredibly beautiful. It is my personal version of paradise. 

In 2019, I left several things on the seafloor: cages to keep predators out, frames to mark specific stones, traps to catch larvae, and panels for newly-settled juveniles to grow on. Using these tools, I wanted to answer several questions: (1) What larvae settle on the reef? (2) How quickly do hard-bottom animals grow? (3) How much turnover is there in the community? (4) Does predation explain the low recruitment - is everything just getting eaten before it can grow? By revisiting the Senke site and finding my experiments again, I could answer all of those questions. It just took 5 years of waiting. 

Finding my stuff again is easier said than done. We left an acoustic homer beacon on the seafloor, but 5 years is a long time for a battery to last in frigid water. Thankfully, the waypoints that the ROV team had marked were accurate, and my experiments were right where I had left them. As we pulled up to the point on the map, I could already see one of my white cages gleaming in the dark water. 

One of my experimental cages covered in amphipods!

I was so excited to see my experiments again. Not only was my stuff still there, but it was all exactly where it was supposed to be and seems to have worked! The frames still surrounded their choice stones, so I got photos of the exact same rocks 5 years apart. The larval traps had all opened automatically, and when I looked through their contents in the lab, they even had stuff inside! Two of the cages were mysteriously out of place. I can't explain how it happened, but the cages were upright and sitting next to their stone, not on top of it. I'll have to exclude those two cages from my analysis because they clearly didn't keep predators away from their stones like they were supposed to. But overall not bad. 

The experiments were the most exciting part to me, but not for everyone. As the ROV made its way around the reef, it became clear that my experiments had actually become habitats. Tiny crustaceans called amphipods clung to the cages and traps. Another scientist on board, Saskia, hopped on the radio and gingerly, politely placed her request - was there any way we could collect the amphipods? 

I was doubtful we could pull it off, given that amphipods readily swim away when disturbed. I thought they would all pack up and leave town when a giant, loud, bright robot descended on their reef. We managed to suck up 7 individuals with the ROV's suction sampler (yes, it is literally an underwater vacuum). I hoped Saskia would be content. 

When the ROV returned to the ship, we had a huge surprise! Amphipods clung to my traps, just like they had done on the seafloor! I have no idea what possessed them to stay in place for a 1.8 km ride to the surface, but I'm grateful that they did. Saskia had ideally wanted 20 amphipods, but in the end, she got 31. 

It was an incredibly successful dive, and I'm so excited to finish my Senke experiments!