2 December 2010 – Salps !

We began our research sampling yesterday after a bit of delay due to that large low pressure system that was passing by. Luckily, the center of it slid a bit north which meant the winds (and waves) on the southern side (where we were) weren't too bad.

We've completed two stations so far. At each station we lower an instrument called a CTD which measures the physical properties of water and how they vary with depth. Various parameters like salinity, temperature, density, dissolved oxygen, and fluorescence can give us an idea of how physically mixed-up parts of the water column are and whether there is a lot of primary productivity occurring (i.e. plants growing). The CTD also has a rosette of Niskin bottles along the outside which we use to collect water samples from various depths. These samples are processed to see what types of phytoplankton (ocean plants) are present.

The CTD rosette is lowered out of a door on the side of the ship with Marine Tech Chance Miller guiding it on its way.

After the CTD, we deploy a net to collect animals from the ocean. We have two types of nets on this cruise which work roughly the same way. We lower them into the water and let out wire. The nets fly downward in the water column and collect any animal that is big enough to be caught by the mesh and small enough not to be able to swim away from the net. When the nets reach the deepest point of their path, we start hauling back in on the wire and bring them back to the surface. Nets are an essential part of oceanography as they provide you with organisms that were in the water where the net flew. However some animals can be damaged by the net collection process so oftentimes we are doing short tows to try and bring the animals up on deck in good shape.

The IKMT (Isaacs-Kidd Midwater Trawl) net is deployed off the stern of the ship.

We end up filtering several hundred (or even a thousand) cubic meters of water with each tow. But because the zooplankton (the name for small animals in the ocean that generally move with the water) occur in patches or aggregations in the ocean, sometimes the net comes up empty and sometimes it comes up full. Our first net had a single adult Antarctic krill (Euphausia superba) but a hundred or so pteropods (pelagic snails) and chaetognaths (transparent arrow worms). Our second net had a lot of algae, more pteropods, and salps which is good as one of our primary research goals is to collect salps for ship-board experiments.

Our very first salp caught on the trip. Hopefully we'll catch a lot more!

But working on the ocean doesn't always go smoothly. We just had to cancel our CTD and net deployments at Station #3 due to the sea state being too large to deploy our gear safely. The safety of the deck crew and the equipment onboard is very important so we tend to err on the side of caution. We definitely can't replace most of the equipment on board if we were to lose it, and the people are even more valuable. Sometimes you just can't sample, so we're steaming towards our next station and hoping the conditions improve.

Working here in the late spring/early summer (the seasons are opposite of what's going on in the Northern Hemisphere) offers some neat experiences. We have a only a few hours of night and it never seems completely dark (more twilightish), but that means you sometimes have a sunset or sunrise where there's just a beautiful orange glow on the horizon for a few hours.

Last night we had a very nice sunset.

-Joe