Aquatic Carbon Cycle
Carbon is the central element of life. The aquatic carbon pool is a major reservoir of reactive carbon in the biosphere (comparable to the carbon dioxide in the atmosphere and the carbon within terrestrial biomass), and microorganisms play a dominant role in both its production and consumption. Studies in the Biddanda Lab are therefore focused on understanding the role microorganisms play in mediating the journey of carbon in the aquatic environment, and occur at the interface between microbiology and biogeochemistry.
Ongoing research at Dr. Bopi Biddanda’s laboratory of Aquatic Microbial Ecology and Carbon Biogeochemistry, extends over two of the Great Lakes: Lake Michigan and Lake Huron. These studies focus on examining pelagic carbon metabolism in Lake Michigan and adjoining Muskegon Lake, and on exploring submerged sinkhole ecosystems in Lake Huron. Collectively, it is anticipated that these two system level process studies will provide a working picture of the cycling of carbon in key sub-ecosystems of the Laurentian Great Lakes.
Lakes are intimately connected to the terrestrial ecosystem through their air and watersheds. Because carbon is a central element of life, tracing its flow in aquatic ecosystems can give us insights into how these systems function. Consequently, our studies focus on understanding the carbon balance in these natural waters. Simultaneous measurement of both production and respiration processes made by measuring changes in dissolved oxygen in light and dark enclosures indicate that these coastal ecosystems receive substantial inputs of carbon and nutrients from river loading that may explain enhanced production of microbes and fishes in these receiving basins. In Lake Michigan and its adjacent water bodies, we are studying the carbon cycle. Some of the key findings so far are: 1. In coastal drowned river mouth lakes excessive phytoplankton production is stimulated by availability of the nutrients such as phosphorus and/or nitrogen, 2. River plumes and episodic sediment resuspension events enhance coastal metabolism stimulating both carbon and nutrient cycling, and 3. Late-winter production pulses can result in the transport of high productive waters to offshore and central Lake Michigan as features that are visible from satellites.
One question of great interest is how the lake ecosystem will respond over the short term to episodic events such as storms, and over the long term to ongoing climate change. Future studies that continuously monitor carbon traffic using moored instrument arrays equipped with sensors will help in figuring out whether these water bodies serve as net sinks or sources of carbon dioxide to the atmosphere.
Picture of water sample collected from a bloom of phytoplankton in western Lake Erie (August 2003). How do you study natural processes occurring in lakes and oceans without disturbing any of the system components? This is the challenge.
Conceptual changes in the distribution of organisms and nutrients across a productivity gradient:
In low-productivity systems, nutrients are primarily organic and dissolved (small prokaryoteic autotrophs and osmotrophic heterotrophs dominate), and autotrophic-hetrotrophic coupling (A-H coupling) is strong, - that is, prokaryotic hetrotrophic respiration is equal to or greater than primary production, with little organic matter remaining for export to the sediments. In eutrophic systems, nutrients are primarily inorganic and particulate (larger eukaryotic autotrophs and phagotrophic metazoans dominate), and A-H coupling is weak, - that is, high export production.
Page last modified August 23, 2013