September 16, 2008
Today we completed GAK12 and GAK13. GAK12 is over the Continental Slope and GAK13 over the very deep water of the open ocean 150 miles offshore. I can now say that I have been on a ship in the North Pacific with no land in sight. This completes the GAK line for the day time sampling. Everyone is very pleased especially since last spring the weather was so rough that they had to end at GAK9. Everything went pretty smoothly this trip. On two occasions the computer connection to the CTD came apart and had to be repaired. Last spring the cable got wrapped around the propeller. They had to travel slowly to a sheltered cove where they sent down scuba divers to set things straight. Fortunately no equipment was lost and the damage was minor.
Russ is conducting an experiment with 100 female copepods of the genus Psuedocalanus, a cold water species. He puts each individual in a separate small flask with fresh seawater in a refrigerator adjusted to the current seawater temperature. In 24 hours and again at 48 hours, he will count how many of the 100 females have produced eggs. Pseudocalanus typically lays her eggs in the late afternoon or early evening, so it is important to set up the experiments before dark. Pseudocalanus holds on to its eggs in a sac until they hatch. Egg production is a good indication as to how nutritious the food source is and how productive the copepod population is. For example at the first station GAK1 (Gulf of Alaska), 34 females had eggs. Russ does this experiment at four of the 13 stations we visit on this line (GAK1, 4, 9 and 13) and for one of the stations in Prince William Sound. During the spring cruise, Russ repeats these experiments and does growth rate experiments as well. He measures how fast juvenile copepods increase in size and weight over five days. Both of these types of studies are rarely done at sea. Not many people can handle looking through a microscope for long periods of time while the ship is under way.
Russ explained the costs involved in conducting a survey such as this one. The zooplankton net costs about $2000 including the mesh, covering, lead weight, flow meter and buckets. The CTD with its 12 Niskin bottles costs $50,000. The multi-net costs about $50,000 partly because it is made in Germany and the Euro is stronger than the dollar. Russ's microscope costs $15,000 and the medical quality camera $7000. Russ must use some of his grant money to pay for the Tiglax and her crew. That cost is $6300 per day. Russ explained that not just any ship or crew will work. The crew must be experienced in handling scientific equipment. Deck hands John Faris and Andy Velsko know how to operate the winch, cast off and retrieve equipment without damaging it. They are impressive especially when considering the rough seas we've been having. The ship must have a lab, winch, freezers and plenty of storage space for all the water samples.
This evening Ken, Allison, Jeannette with the help of the deck hands will launch the multi-net at GAK5-1. Tomorrow we'll get some samples for Katherine's light experiments (see below) at GAK1i and GAK4 before going to Prince William Sound. The seas should be much calmer there and there will probably be more birds.
At a few of the stations, Katherine conducts light experiments. She measures the amount of light hitting the surface of the water and then lowers the CTD until only 10% of the light is detected. Now she's able to use a Secchi Chart to calculate the depth at which 50%, 30%, 12%, 5% and 1% of this light is able to penetrate the water. Then the CTD with its Niskin bottles are sent to these depths and water is collected. The chlorophyll collected from these samples will be measured to correlate to the amount of sunlight available with the abundance of phytoplankton.
Katherine also conducted some light experiments using the radioisotope C13. She let water samples incubate in the sun for 4-6 hours with some C13. Each bottle lets different amounts of light in to mimic the different depths in the ocean. For example, one bottle was clear, letting in 100% of the light while another had tape covering all but 30%. As the bottles incubated, the phytoplankton continued to produce organic molecules such as chlorophyll and to incorporate C13 into these molecules. At the end of the incubation period, Katherine filtered the water. She will be able to place these filters into a counter that detects the amount of C13 present. This gives Katherine an estimate as to how fast the C13 was incorporated by the phytoplankton.
Today was a good bird day. While chatting with Captain Billy Pepper on the bridge, we spotted a plump bird unable to take off and fly. The captain explained that it was an immature puffin that had eaten too much! I joined Brad at his bird station and we saw some new birds including Cassin's Auklets, a Long-tailed Jaeger, and an Aleutian Tern. However, the most interesting birds were a few lost migrants. A pair of yellow Warblers, a sparrow and a Lapland larkspur landed on the Tiglax for some much needed rest. We also were lucky enough to see two Sei whales and some Dall Porpoises.
This evening I interviewed Russ while he checked his female copepods for eggs. Russ is Canadian, originally from the Toronto area. He has always been interested in studying the ocean, ever since he was a child. He's very happy with where he is at now in his career. He loves learning new things and satisfying his curiosity. He especially loves sea time as he is able to do hands-on work in the lab. Normally on campus he is too busy with paper work, e-mails and teaching to conduct his own experiments. He has a technician who runs his lab and three graduate students. He works 60-80 hours per week, but makes a point of taking Saturday and Sunday off to spend with his family.
I asked Russ about his favorite zooplankton. There are two groups that he would very much like to study in more detail, hopefully even raise in the lab. The first is a group that the Europeans call the Appendicularians and the North Americans call the Larvaceans. They are a type of tunicate, an animal with a primitive backbone and they have a novel life cycle. They build large mucus feeding structures and have very delicate parts. They may be more important to the ecosystem than their numbers would imply because they grow very rapidly especially in the tropics. There are 70 known species. In comparison, there are 2000 copepod species.
The second group is the pteropods, the pelagic snails. There are about 100 species and two different types, those with and those without shells. Those with shells are herbivores and difficult to raise in a lab because they need a large aquarium in order to deploy their mucus nets. However, they are easy to identify because each species has a unique shell. The naked pteropods swim faster and have evolved into predators. They prey on the shelled pteropods and so are easy to raise in the lab. Each species has a different feeding apparatus. Preseved samples are difficult to identify because they roll up into a ball when they die.