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SEA Currents Blog

SEA Currents: Robert C. Seamans

March 12, 2014

S251 Weblog 12 March 2014

Aleja Ortiz, B Watch, Graduate Student at Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution


Billy-Ray, our banded cookie cutter shark, found in the 2-meter net deployment.

Current Position
17° 43’ 00.00” S x 142° 39’ 16.80” W
Current Location
On our way to Tahiti from Hao
Course and Speed
sailing 275° at 3.5 knots
Sail Plan
Mainstays’l, course, tops’l, and raffee
32°C, sunny, hot, and beautiful

So last night, we finally deployed the 2-meter net! We have been deploying throughout the trip two different nets for collecting different types of plankton: the neuston net and the 1-meter net. The neuston net is towed at the surface for 30 minutes. The 1-meter net is towed at depth (typically around 150 m). Basically water and biota is funneled through the net and collected at the end of the net in a small bottle (think a Nalgene minus the top). We then sample the bottle (we call it the cod end) and investigate the collected water and biota for organisms and other interesting features. We usually do a one hundred count (we take about 1 ml of sample and count and identify the first 100 organisms we find using a microscope) on these deployments. We also measure biomass and record some water properties (like salinity, temperature, chlorophyll-a content). Anyways, the 2-meter net differs from the 1-meter net in the size of the net. In the 2-meter net, the net is 2-meters large in diameter. We also deploy it much deeper. So last night we deployed the net for about an hour focusing on collection at 500 meters depth where we expected lots of interesting organisms.

The net came up rather slowly because we deployed over 1200 m of wire. But once it finally came up, my job was to empty the cod end (the bottle collecting all the organisms at the end of the net) into a bucket so we could then analyze our catch. It was hard to unscrew at first but then I finally managed to unscrew the bottle and dump it into the bucket. As soon as I did that, however, I noticed this large black thing hanging out of the bottom of the net. I shook the net a bit and it fell into the bucket with a splash. I informed Jan (the chief scientist) that we might have caught a shark or a fish. It turned out that my initial guess of a shark was right! We actually caught a banded cookie-cutter shark that was nicknamed Billy Ray (not entirely sure where the name came from but it certainly stuck with the students).  Billy Ray was just over a foot long and was bioluminescent on his belly. Apparently, cookie cutter sharks are well known for their bioluminescence, it meant that he glowed a bit while swimming around. We also caught a host of other interesting if smaller creatures ranging from a large Polychaete (transparent 2 inch long worm) to several pretty shrimp and small fish.

At this point in the trip, we are trying new and different science deployments instead of just the hydrocast and neuston net (the mainstay of the rest of the trip). It means that the students get to experience different equipment and fauna. In two days, we will be sending down a styrocast, which I am sure someone will describe in detail. It makes for a nice change of pace. Today was also the deck practical, during which the students were tested on their knowledge about being on watch and day-to-day things. It was a fun class in that we got to write short answers and then walk around finding things that were purposefully wrong (aka the lifeboat was not attached to the deck). Students also got to demonstrate their knot tying expertise. All in all, students are slowly finishing up all their work and turning everything in, so I think finishing up the deck practical was one less thing to worry about.

Lots of love to my family in friends back in Boston and abroad. I hope everyone is enjoying my other blog that I write daily!

- Aleja




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