MOCNESS: Not just sampling Krill

MOCNESS MOVIE Movie Credit: Peter Wiebe

Hello, Kaylyn here just to update you on our MOCNESS tows. The MOCNESS stands for Multiple Opening/Closing Net and Environmental Sensing System. The MOCNESS has 9 nets with a 335 µm mesh size that can sample different regions of the water column because when one net closes the next opens. We use the MOCNESS to sample the water column to identify what animals cause the acoustic scattering we are seeing on our instruments.

Spraying down the MOCNESS making sure all animals reach the codends. (From right to left Wu Jung, Nick, and Kaylyn in the back) photo credit: Nick Nidzieko

Although this cruise's main emphasis is krill, the MOCNESS samples most of the water column, so we get to see more than just krill. Some common animals that we have seen are copepods. Copepods are a type zooplankton that are food for many animals such as krill, fish, and whales. We have generally seen two genera Calanus, and Centropages. This cruise we have also seen Fish Larva which was to be expected because we timed this cruise with the Herring spawning event. Another animal is an Amphipod which is a planktonic crustacean that birds and fish feed on.

A jar packed full of copepods (Calanus finmarchicus) as well as amphipods, and a couple of fish larva. photo credit: Kaylyn Becker

We have also seen Jellies, particularly Ctenophores, Jellyfish, and salps. These animals are translucent filter feeders and feed on phytoplankton and zooplankton.

A sampling jar with a large Ctenophore and several copepods probably Calanus finmarchicus photo credit: Kaylyn Becker

Normally we don't get a sample of benthic animals (animals that live on the bottom of the seafloor) because we don't sendthe MOCNESS all the way to the seafloor. This cruise however we accidentally brought the nets a little too close to the bottom and ended up with an octopus in our nets. We have loosely identified him as a North Atlanic Octopus Bathypolypus articulus, and have dubbed him Phil Jr because Phil found him in the net.

Phil and the Octopus dubbed "Phil Jr" photo credit: Gareth Lawson photo credit Kelly Kleister

One of our other interesting finds was Pteropods. Pteropods look like grains of sand to the naked eye but are beautiful under a microscope. Their name means "winged foot" because they look like they have wings and are flying through the water. They are basically snails that live in the water column. Gareth was particularly excited about the Pteropods because next year he will be studying how Ocean Acidification affects these animals in the Atlantic and Pacific Oceans. Due to increasing anthropogenic CO2 emissions, the ocean's pH is decreasing. Pteropods shells may dissolve in an acidic environment so they are particularly sensitive to this changing chemistry of the ocean.

Photo from : http://www.arcodiv.org