Greetings from the nightwatch

The night watch has been very busy this leg of the cruise. We have been successfully sampling with the VPR (video plankton recorder) and the MOCNESS – a big plankton type of plankton sampling gear with 9 stacked nets we have nick-named the MOCNESS monster. We have covered a wide variety of habitats and seen interesting things at each one.

gammarids, larval fish and veliger larvae

Nantucket shoals: clockwise from top left, gammarids, larval fish and veliger larvae.

Our first stop was Nantucket Shoals, SW of the island of Nantucket, MA. This is a very shallow area with most depths under 50m. On the first night we saw large numbers of baby fish. We were also excited to see thousands of veliger larvae, better known as baby snails, each only 3mm in size. The second day had us in the middle of a swarm of gammarid amphipods. These are the same type animals as beach fleas you can see at the beach. In the water they stay on the bottom during the day then swarm up towards the surface at night to feed. Almost every fish you might like eat including cod, flounders, haddock, and stripers love to eat these gammarids. It is no wonder the Shoals are considered a great place to go fishing!

salps

Salpa aspera 13: A section of a chain of salps. There can be over 100 individuals in the chain which can be up to a meter long.

Next we steamed offshore and have been sampling in very deep water ranging from 1500 to over 4000m bottom depth. The animal we are seeing the most out here is called a salp. This is a hollow, jellylike animal with bands of muscles that contact to propel it though the water. They are found all along the east coast in large numbers during the summer. This animal is called a diel migrator. This means they live down deep in the water during the day and come up to the surface feed on phytoplankton (small plants) at sunset. At dawn they once again travel over 1500m back down to the depths to avoid being eaten. That is some pretty impressive traveling for an animal that is only 2-5cm long. The salp we are seeing this year is called Salpa aspera. It can be found alone or in large chains of individuals.

a single salp

Salpa aspera 16: A solitary Salpa aspera about 3cm long.

An interesting animal that feeds on the salps is called a phoronima. This “bug” eats the salp then uses the jelly to make its house. The phoronid lives in the barrel like house using its legs to dog paddle, moving both it and the house through the water. You may wonder why the phoronima looks familiar . . . this is the animal that inspired the creatures in the movie Alien.

phoronoid

Phoronid3: a phoronima in its house.

We will continue to enjoy beautiful sunsets to start our watch and head to our bunks to sleep as soon as the sun rises.

sunset at sea

Another beautiful sunset enjoyed from the deck of the Henry B Bigelow.

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