We just had a couple of great lectures. Before dinner we heard Cindy Hagley from Minnesota Sea Grant. I learned a lot about limnology (like what it is!) and Lake Superior. It is awesome to hear the lecture while watching the Lake right here on the deck. As I type we are traveling north along the North Shore of Superior. We can’t make out distinctive trees from this distance; but, you get a clear view of the overall tree coverage on the hills. The water surface is like glass. If you were sitting inside the Lake Guardian, you wouldn’t even know the boat was moving. Just a constant, low thrum and a vibration. Cindy knows so much and is able to pull all of the content together and have it make sense.
We broke for dinner. Wow. I’m going to gain 5 pounds on this trip. Smoked salmon, pork loin steaks in gravy, fresh grilled vegetables. Donna makes an unbelievable chocolate cake. Butter cream frosting with dark hershey chocolate. My mouth is still watering.
Dr. Marty talked to us again about diporeia and the food web after dinner. Cindy gave us color posters of the lake food web that matched his lecture and that are perfect to teach students with. We will be working in the biology lab tonight counting diporeia from our earlier sampling and from tonight’s transects.
We have finished transect 2 and are moving to transect 3. We will be on-station at midnight and will sample until 4 or 5 am. We are heading toward shallow water and will have to move slowly because of the risk of fishing nets. It is hard to imagine how quickly you can get from very deep to very shallow water on Superior. We are at 180 meters right now.
The transects are the way the scientists organize data collection systematically. We have anywhere from 8 to 4 stations on each transect. The transect is a straight line created by plotting points with longitude and latitude coordinates. They are chosen based on bathymetry (not topography, since it is under water). We are moving from offshore to inshore, so from deep to shallow water. The transect keep the data organized–we label samples based on where the sample was collected and can match the samples to time of day, date, depth, temperature, longitude/latitude, and even who the personnel were that collected and analyzed the data.
We are using electronic sensors to measure depth, water temperature, dissolved oxygen, and fluorescence (which is a way to measure the abundance of algae at a particular level). At our different stations on each transect, we collect water samples based on the location of water layers. The thermocline is where the temperature layers. This signals a location where plankton and potentially fish may be more abundant. At these stations, we also collect algae with a vertical towed net and bottom grabs to get samples to look for diporeia. The scientists are monitoring these amphipods because they are a critical component of the lake food web. The other great lakes have serious problems with diporeia, but so far Lake Superior is doing well. Later this week, we have another set of scientists coming on board to move us further up the food web by looking at the fish populations. More later.