November weather

Ocean research cruise blog of Jonathan Sharples

 

The remarkable weather continued yesterday as we continued a series of measurements and zooplankton nets next to the moorings. A couple of scientists were even spotted sunbathing between net hauls. The wind continued to drop, and the sea finally reached a glassy state by sunset. Pretty good for November in the Celtic Sea.

The winning picture of the salps in the process of releasing faecal material into the water is below: look at the streaks of back trailing from the curl of colonial salps in the lower left of the picture. Some of these salp groups are reaching lengths close to 2 metres.

chain of salps

salps cought pooing

 This morning just as the sun came up we carried out one vertical profile with the CTD just next to the wirewalker mooring. That will provide Jo Hopkins with vital data for her to calibrate the instruments on the mooring. We are now pulling up the wirewalker, and will then head off to collect the 2 gliders that neeed to come back with us. The glider “pilot” back at the Oceanography Centre has sent instructions to the gliders to meet as at a specific location, so the gliders will have dutifully reached that position this morning and will now be bobbing about on the surface waiting for us.

ctd at down

The weather is due to close in tomorrow, with 25-30 knots of wind expected from mid afternoon through to mid afternoon on Friday. But the longer term forecast is suggesting a return to these calm, sunny conditions. Feels strange for this time of year, but none of us are complaining.

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More jellies

Ocean research cruise blog of Jonathan Sharples

 

The children at Churchtown Primary School are I gather busy working on the questions we asked them about sinking salp poo. The zooplankton group on board are getting very excited about their results, and already planning the scientific papers that they want to write. We collected more of the zooplankton yesterday so that we can make better estimates of the rate at which they eat and the rate at which they release the faecal pellets. In an attempt to get an idea of what these delicate organisms look like in the ocean we attached a few waterproof cameras to the CTD, and lowered them into the sea surface to record pictures for half an hour or so. I set the challenge to get a picture of a jellyfish or salp in the process of releasing faecal pellets into the water. There was a clear winner (Clare Ostle, from the University of East Anglia), but she was working very early this morning and is currently in bed – so I’ll get the photo for tomorrow.

an interesting bucket of jellies

Meanwhile, to help the kids at Churchtown think about this problem, the picture below has some good examples of the salps (the long, tubular jellies, connected in spirals) and the tiny jellyfish. Another rally interesting organism in this photo can also be seen, just about. The photo looks like it has a fine sprinkling of sawdust in it. These are tiny colonies of a photosynthesising bacteria called trichodesmium. It’s special in the ocean because it is a nitrogen fixer – it is able to use nitrogen gas dissolved in seawater, rather than the form of inorganic nitrogen (nitrate) that most phytoplankton need. That means they can grow in areas where nitrate is in very low concentrations, such as the large areas of open ocean in the sub-tropics. Finding them here is odd, because there is enough nitrate around and so the trichodesmium should not have any advantage compared to other phytoplankton. I’ll find out a bit more about them for another blog entry.


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salps and tiny jellyfish

Salp soup

The weather deteriorated a bit after the first CTD cast. Wind reached about 40 knots, so we had to stop working as the motion of the ship was putting too much stress on some of the equipment hanging over the side. However, things have calmed down nicely for the afternoon. A group of 6 or so dolphins has been hanging around the ship, probably feeding on the fish that often congregate underneath us if we stay in one place for a while.

zooplankton net

Sari Giering (University of Aberdeen) has started her sampling of the zooplankton – the tiny animals that feed on the microbial plants (and on each other). There is general surprise that there is so much biological stuff in the water, given the time of year. The zooplankton net, which is hauled vertically upward through the water to catch any zooplankton on a mesh at the end of the net, has come back with all sorts of stuff. The latest haul had a large colonial salp – a gelatinous filer feeder about the size of your finger, but that lives in long connected ribbons of several dozen clones.
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bucket full of sulps