Deep net tows

Science happens every day on the boat. From hourly recordings of ocean water temperature and salinity, current direction and magnitude and much much more, to daily deployments that consist of hydrocasts or neuston tows, we’re continuously gathering data on the biological, physical, and chemical nature of the waters we’re passing through. At it’s always quite a bit of fun, but, towards the end of the trip, the stakes were raised when we began deep net tows, a stack of three nets on our hydrowire, each trailing behind out boat at a different depth up to 200m.

I was on dawn watch right after we pulled up our first deep net tow, and the salty smell of sea life covered the deck, pouring down through the galley hatch into the salon to my sleepy nose At first, I was very puzzled, and a little alarmed. Such a strong smell of brine was foreign to below decks. For a second I thought that something might be wrong, but then I remembered that deep net tows had started that evening.

On the science deck, i was greeted with a pile of nets–the massive circular 2 meter net, the smaller though still circular and awkward 1 meter net, and the familiar neuston net, which we had been towing throughout the trip. And buckets full of cool organisms.

A Watch, having dawn watch, were responsible for processing all of the things collected in the nets. Six hours of lab work later, we’d sorted our tons of shrimp, fish larvae, salps, ctenophores, and an eel like thing amongst a whole lot of biomass.

Luckily enough, the next night, the deep net tows continued. I was in that evening watch and was the Junior Lab Officer for that time, meaning I got to run the deployment. Which was cool because deep net tows are crazy and new but also a bit intimidating because, well, I’d never even seen one done before.

After getting the low down from our assistant scientist, we and and my two watchmates in lab started setting up. We retrieved the three nets and got out all the gear we use to trail them through the water–the clamps to attach them to the hydrowire, and something that looks like a little torpedo with blades that spin around to measure how much water the nets pass through, and a mini CTD. We also prepped the hydrowire and set up the signs informing our shipmates that the science deck is off limits.

Doing deep net tows requires a lot of communication between science and the deck–to make sure we are going the right speed and to make sure people are watching out for the nets. We let out so much wire that the stack ends up trailing behind or off to the side of the stern of the boat. And the actual deployment involves bursts of activity and periods of wait time. The first net is put into the water with a weight below it to drag it below the ocean surface. We quickly let out the wire and the net falls away from the boat. After we’ve let out enough wire, we lasso it back to us to clamp on the next net. Rinse and repeat until all three are trailing in the water.

After our first net went into the water, the chief scientist and the first assistant scientist ducked under the lines blocking off the science deck and motioned me to follow them.

“What are we not supposed to be on the science deck?” I asked, still unclipping my harness from the rail, which I had attached myself to while wrestling the 2 meter net over the side of the boat.

“Yeah.” the Chief Scientist said, “See the wire angle there? It’s a lot more dramatic, a lot closer to the boat. We don’t want to be too near it.”

I looked at the wire, which normally streams straight off to the side of the boat and down into the water. This time though, it ran at head hight along the deck, the net pulling it backwards to the stern of the boat. He was right. I didn’t want to be anywhere near there.

But we couldn’t have asked for a better night to do a deep net tow. It was one of those few entirely clear nights, where the stars are so numerous, the sky so thickly dark that you can’t help but realize how small you are, just a speck on the ocean on a speck of a planet.

When we finally brought them in, the nets emerged ghostly from the water. We upended the contents of the jar at the end of each net into their own pristine bucket. And the real bun began, a 20 minute session of oohing and aahing over the critters he had plucked from the deep. Salps. Ctenophores. Hyperiid Amphipods still inside of salps. Lobster larva the size of our scientist’s palm and clear as glass. A lot of fish larva, and one large fish with a huge mouth.

In the complete dark, swirling the buckets causes the bioluminescence to light up, creating great swirls of blue in the seawater. The next watch was going to process of of these treasures, but for that moment they rested in the buckets, spinning and glowing blue. And the smell of them, the brine of things which had never reached the air, cloaked the ship.

Later, after turnover, and and a few watch mates lingered on deck, gazing up at the stars still brilliant. More so than ever aware of the strangeness of the sea. It felt incredible and strange to be right there, on theĀ Seamans on the dark ocean. Who was I to haul on a line and to label myctophids?? And how did I get here? And was I really that brave to dream myself into this trip?

And if felt correct. Wholly and completely. Because of course I was there. LIke where else could I be but on deck covered in zooplankton and in a spot on the globe where the beauty of the stars is only matched by the glowing orbs that swirl in the water all around us?

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