This is Jim Fiorendino, your host for On the Ocean.
Phytoplankton are microscopic photosynthetic organisms present in all the world’s oceans. They are an abundant and diverse group known to produce organic compounds that may be an important part of cloud formation processes. Waves breaking and bubbles bursting at the surface of the ocean transfer organic material from the ocean to the atmosphere in droplets of water. Dr. Daniel Thornton of the Texas A&M University Department of Oceanography is currently researching how phytoplankton biology influences the chemical composition and production of organic material in the ocean. Certain processes, such as cell death, may be particularly important, as they result in the release of large amounts of organic material into the surrounding water.
Growing phytoplankton within a Marine Aerosol Reference Tank or MART (Figure 1) allows Dr. Thornton to study phytoplankton growth under varying conditions as well as the production of organic material by phytoplankton. The MART is sealed; inside, cultures of phytoplankton are grown in 63 liters of water, with a headspace of atmosphere roughly twice the volume of the water in the MART. Currently, Dr. Thornton is studying the diatom Thalassiosira weisflogii, chosen because it is a cosmopolitan species that grows well in a laboratory setting.
Air and water samples are taken from the tank and analyzed using various instruments to determine the size and chemical composition of both aerosols and organic matter. One of these instruments, known as a cloud condensation counter, determines what proportion of aerosols can form clouds at specific temperatures and relative humidity. Several other analyses are performed as the phytoplankton grow and die, allowing any changes in organic matter and aerosols to be documented. In the future, Dr. Thornton plans to grow additional species from other major groups of phytoplankton to gain a more complete understanding of how the marine phytoplankton community contributes to organic matter production and, consequently, cloud formation. Images of organic material within a MART are shown in figures 2 and 3.
This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.
Contributing Professor – Dr. Daniel Thornton