Research

Microbes That Regenerate Nutrients in Coastal Marine Sands
Joel Kostka

Microbes Microbes are the “hidden heroes” of coastal marine ecosystems because they break down or degrade dead plant and animal bodies, thereby releasing nutrients to be reused by plants. When microbes on the sea bottom regenerate nutrients to be used as food for phytoplankton, scientists call this “benthic-pelagic coupling.” In the past, it was thought that because muddy sediments on the bottom of the ocean contain a lot of organic matter, these parts of the seafloor were the most important to benthic-pelagic coupling. However, recently, scientists have found evidence that sandy sediments are just as important or perhaps more important than mud. Therefore, we are studying the microbiology of marine sands for their role in replenishing nutrients for phytoplankton. In a NSF project with Dr. Markus Huettel, 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 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.

Dr. Kostka's research is featured in FSU's award-winning magazine, Research In Review,
in the article "The Living Sands of St. George"