By Magda Cardozo, PhD student of Max Planck Institute for Marine Microbiology, Bremen |
In the open ocean, microbes are the most active and abundant organism, and control processes that are crucial for sustaining life on earth. We can study microorganisms from samples taken from a wide range of equipment and sources, from the sea surface to the sea floor. We can explore these tiny forms of life in the water, but for that we need to collect large volumes of water, so our gear is rather large and heavy. For example, we use auto-samplers that sample water all year long, or a “CTD” (conductivity, temperature and density), which is basically a metal rosette with several large bottles that can collect water from different depths at each research location or station. On this cruise, my research is focused on bacteria in the water column. We filter water from different regions of the Fram Strait, including those, which are covered by ice. This year I am using an in-situ pumping system that can filter large volumes of water without the constraint of time, which is crucial for molecular studies.
The procedure is rather simple. Before we begin, we receive an announcement from the chief scientist, with the research stations for the next 24 – 48 hrs scheduled. On a research cruise such as this one, we work in shifts to insure sampling whenever it is possible throughout the day. After we reach a station we stop the ship and deploy the pump at the scheduled time, which for our research group is often during the night. The pump is attached to a special wire and a CTD and then lowered into the ocean, and we wait for a couple of hours while the pump is in action. During that time my colleagues gather to wait for the CTD to collect the water sampled from different depths in the water column. It is a very special moment at this time of the year, as the sun continues to shine in the Arctic region throughout the full 24 hrs of a day, which makes the task a lot easier and very special. We might have a coffee or a hot cocoa while we wait for the gear to come back on deck. Collecting water is one of the most reoccurring events during our cruise, scientist from different fields of science wait to answer their questions from those same litters of sea water. Back on deck I have to be fast, I open the pump and take the hand sized filters out, which are designed to catch microorganisms of different sizes. We then cut the filters into sections for subsequent tests, and quickly freeze them in liquid nitrogen so all the bacteria and associated DNA remains intact for as long as possible. The filters will be further analysed back in Germany to answer questions of microbial community structure, functioning and activity in the Arctic Ocean. The Arctic is changing quickly, and we are facing changes that will affect the marine ecosystem, from the smallest to the largest members of the food-web. These samples might provide us with answers on how climate change is affecting the Arctic ecosystem.