Modeling Vertical Particle Flux in the Oceans
Although the oceans are by definition filled with water, particulate material plays many important roles in the biogeochemistry and ecology of the oceans. Most of the particulate organic material in the open ocean is ultimately derived from phytoplankton. These small, single cell organisms sink very slowly, but we know from measurements made in the deep ocean that this material can reach depths of 4000-5000 m within several days. This means that there must be some way for these particles to increase their sinking speed. The answer to this conundrum is aggregation, the process through which particles collide and stick together. Particles can be brought together through a variety of physical and biological processes. The most important physical processes for large particles involve motion through or with the water. In addition, animals such as small crustaceans can eat the particles, discarding as fecal pellets what they do not utilize. This makes the biological processes quite complex because not only are particles re-packaged, they are also transformed chemically.
These processes are important because aggregation affects the vertical flux of organic material from the surface to the deep ocean. This flux affects the distributions of nutrients and other elements that are essential for a healthy ecosystem. It's also one of the controlling factors in the ability of the oceans to store atmospheric carbon. In our lab we're trying to develop computer and mathematical models to understand all these processes and predict how they might change in a changing environment.
Salt Marsh Grasses
Salt marshes are crucial coastal environments and we are part of the Georgia Coastal Ecosystems Long Term Ecological Research Project (GCE-LTER). In the southeast US, the grass Spartina alterniflora is a major component of salt marsh ecosystems and it is critical to understand how it is affected by changes occurring in the environment. We are developing a model for Spartina growth and production. In doing this, it is important to consider both the above-ground parts of the plant (which are important sources of food and shelter, and affect the flow of water on and off the marsh) and below-ground parts (which help stabilize the sediments and act as storage for the plant during winter). To examine this, we have teamed up with other UGA and GCE-LTER scientists to measure the biomass and composition of the above and below-ground parts of the plant to see how they change throughout the year. This information will be used in developing our model.