August 26, 2006
Today we sampled at the deepest site of the whole cruise, a place called Georges Basin in the Gulf of Maine. This site was 360 meters deep and since it came shortly after a whole bunch of sites on Georges Bank that were among the most shallow places sampled (20-50 meters deep) it provided a very concrete illustration of the changing topography of the ocean floor. There were four other very deep sites to be sampled in the Gulf of Maine. These sites were fixed, meaning that they were sampled each time this cruise goes out, as opposed to all the other sites that were selected at random for each cruise. Right at the bottom of these five deep sites is where the very cold, dense water from the Labrador Current, flowing south from the Artic, tends to accumulate. These sites are of particular interest to scientists as they provide data that helps in understanding the flow pattern of this cold water current.
When one of the bongo tows came back to the surface today it had a stand of Sargassum seaweed caught up in the cable. This is a floating type of seaweed that occurs in great quantity in the Sargasso Sea out in the middle of the Atlantic Ocean. There have been pieces of it floating about throughout the cruise. However this particular piece of Sargassum was special because tangled up in it was a weird and wonderful creature. It was roughly circular, flat except for a reddish brown, spherical area in the center, and mostly made of a stiff gelatinous material. At about 20 cm in diameter it was by far and away the largest marine organism we had seen far. Karla immediately recognized it as a pteropod, or swimming mollusk. She had seen them alive in the ocean as they swim slowly and gracefully by flapping their gelatinous wings. Earlier she had pointed out another group of gelatinous creatures floating in the water just off the side of the ship. These ribbon-like waifs were siphonophores. Each one was not a single organism but a colony of specialized individuals strung together in a row.
One of the aspects of this cruise I really enjoy is examining the contents of the plankton nets once they have been washed out into the sieves. So I often took on the task of transferring the sieve contents to the glass jars so that I could get a closer look at the plankton. Almost every day there were new tiny, weird creatures that I have never seen before. The world of zooplankton is certainly interesting. It is sad though to watch them wiggle around as they struggle for life out of their ocean environment.