Characterization of Microbial Communities that Catalyze Carbon and Nitrogen Cycling in Permeable Shelf Sediments

In a project sponsored by the National Science Foundation, the Kostka laboratory is investigating the concept that coastal marine sands act as giant filters, filtering out dead plant or animal bodies, and releasing inorganic nutrients to be used as food for plants. Our research closely couples chemistry and microbiology to determine what controls nutrient release from the sandy seafloor at two contrasting sites near St. George Island, Florida. One site represents conditions found in Apalachicola Bay, while the other is more typical of conditions found in the northeastern Gulf of Mexico.

We have determined how fast organic matter is processed by microbial activities in the giant filter using radiotracers, stable isotope tracers, and flux chambers. Using the latest genetic methods, we have documented “who’s there” or which microbe groups are present to degrade organic matter in the sands. By combining our estimates of microbial activity along with genetic identification of microbe groups, we will find out how the giant filter works in the Bay vs. the Gulf.

As a fellow of the Hansewissenschafts Kolleg (HWK; Delmenhorst, Germany) and a visiting scientist at the Max Planck Institute for Marine Microbiology (Bremen, Germany), Dr. Kostka is currently participating in an international project to investigate the microbially-mediated mechanisms of nitrogen removal from permeable shelf sediments of the North Sea. Shallow intertidal environments from the North Sea are being compared to subtidal environments in the Gulf of Mexico, thereby strengthening the project funded by the U.S. National Science Foundation (described above).