Tuesday, February 5, 2008

Shark encounter, and following a river of trash in the sea.

Our noon position: Latitude 33 45.655 N, Longitude 160 21.999 W

Yesterday was a very exciting day aboard the ORV Alguita. Last week, some students wanted to know – as someone always does - if the Alguita had ever been attacked by Sharks… The answer is still no, before anyone gets alarmed. But last night was our closest encounter! We’ll get to that in a bit.

First, we want to share with you what was a pretty horrible discovery, a visible river of trash floating in the ocean. Unlike anything any of us, besides the Captain, had ever seen… Langmu

ir’s Windrow – a trail of trash. Have you ever noticed, looking out over a calm sea or a lake, when the wind has been blowing steadily from the same direction, that some long bands form at the surface? You may see bits of foam or debris that mark these strips, sometimes stretching as far as a mile or more. Well yesterday, we found one of these, filled with – you guessed it – plastic trash. The morning had started off pretty slow. We’re in what’s known as the horse latitudes, an area traditionally avoided by mariners due to sluggish winds. So after another elaborate breakfast session, (Captain’s on a role – omelettes with fried potatoes, toast and butter, and fried plantains) we looked to busy ourselves with some cleaning and chores – here’s Anna and Jeff lowering the Genoa sail. Then we all sprawled on deck to look for debris.

Charles and Marcus, shown here, stood at the bow ready to net any floating debris, an activity usually resulting in a few synthetic strays here and there – bottle caps, large shards, bits of fishing line, etc. Soon however, they were pulling up large pieces every other minute.

We’d happened on a Langmuir windrow, a series of circular counter currents that meet, sweeping mixed layer sub surface materials to the top, into a sort of oceanic river, visible as a slick on the ocean surface. In a perfect world, this would consist mainly of nutrients – plankton, spawn, etc. – attracting seabirds and other marine creatures to feed. This, as you may have guessed, was a waste windrow – a visible line of floating trash.

According to Charles, this was the second most dramatic windrow he’d ever seen, and the widest yet. Many of the larger pieces showed clear signs of “fouling” – covered with growth, and often gnawed to pieces. Both plastic baskets contained fish, as well as the monofilament drift net with a dozen new banana floats, along with lots of pelagic crabs. A five foot piece of 3” diameter tubing that looked like PVC tubing, but was white on the outside, black on the inside and floated, (PVC sinks in seawater) once removed, housed a triggerfish that came flopping out onto Jeff.

Herb, stuck manning the helm throughout our bustling debris removal, did a masterful job navigating us towards trash while conflicting directions were shouted at him rapid fire.

Here’s the Captain with our day’s haul, an impressive collection. By his accounts, this debris had been at sea for some time, and based on its growth, had resided at deeper levels. The bottle that was floating on the surface not in a windrow was heavily encrusted with barnacles, but the crates and float parts in the windrow had hairy growths characteristic of deeper debris. Future studies may look at ways to determine the depth at which debris has been residing.

Shark encounter!

The area would, we thought, make for a perfect night dive – thick with jellies and salps, prime night for a bioluminescence ( also link to bioluminescence lesson here) no thoughts of the fins we noticed trailing us earlier in the day…..

After anchoring and waiting for nightfall, we slipped into the cold waters and watched a rich scene of underwater life – waters thick with unusual creatures – Jeff pulled up a bizarre, conical shaped Pyrosoma atlanticum-tightly packed colonial thaliaceans embedded in a tough, rigid tube, a lantern fish, and a leaping shrimp. And Joel mentioned spotting a large fish.

Which turned out to be a Mako Shark. The last thing any of us expected to see...and clearly interested in checking us out! Joel actually kicked it away, as Anna, Herb and Marcus made a beeline for the boat.

Mako Sharks are known to be stealth hunters, and are particularly inquisitive, curious creatures. They are acutely aware of what they face –preferring to attack unsuspecting targets. Joel and the Mako did a face off – and when he darted a bit too close, Joel nudged him away with his flipper.

Safely back on board, we all marveled at the unexpected surprise of seeing a shark out here in this so called “oceanic desert”. We continue to comment on how truly rich with life this area is.

We’re all now reflecting on the magnitude of what we’ve seen today. Though the windrow discovery generated some high excitement it also elicited a dose of disgust, and brought up some questions about how far throughout the water column debris is dispersed.

Tomorrow we’re back on our course, heading North to find wind, so that we can continue then heading east. Though we’re expecting a quieter day of travel, one never knows what the gyre will bring…

Aloha and cheers from the Captain and Crew of ORV Alguita!

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