Cambridge (MA) – A tiny seawater laboratory smaller than a stick of gum is showing how amazingly complex and mobile the underwater world of microscopic sea-life can be. In fact, it’s helping MIT rewrite the book on understanding changes in global climate as these carbon munching microbes affect the macro world by transferring energy rapidly through the food chain.
One of the goals of the study was to find out how these tiny sea creatures find food in an open, oceanic environment and, once found, what they do with it. Previous thoughts were along the lines of passive organisms. Basically, as food sources came traipsing along by ocean currents, the organisms moved only slightly to take advantage. One of the first things the researchers noticed when conducting this study was the exact opposite is true.
Their tiny laboratory consists of a transparent, box-shaped contraption. It’s 45 mm long, 3 mm wide and only 5 microns deep, and looks kind of like a microscope slide. When the team injected a food source into the habitat with a syringe-like pump, within 30 seconds the bacteria congregated around the food source. Similar results were given for protozoa and phytoplankton when nutrients or prey were injected. These results indicate a far greater and active mobility than was previously thought, resulting in a rapid transfer of carbon energy from the smallest levels in the ocean to much higher organisms.
According to Roman Stocker, Civil and Environmental Engineering (CEE) professor at MIT, the organisms’ behavior is advantageous. He said, “While relying on different swimming strategies, all three organisms exhibited behaviors which permitted efficient and rapid exploitation of resource patches.” This demonstrates that isolated patches of food in the ocean are not randomly absorbed by whatever happens to be nearby, but is purposefully consumed as the organisms move about, almost attacking whatever is within their scopes.
Fellow researcher Justin R. Seymore, postdoctoral CEE fellow, said, “Rather than simply floating in the ocean and passively taking up the chemicals required for growth, many microbes exhibit sophisticated behaviors as they forage in an environment where patches of nutrients and resources are few and far between.” This foraging ability is changing our understanding of how trapped carbon resources in the ocean rapidly find their way back through the system.
These tiny bacteria, protozoa and single-celled phytoplankton have now proven that their survival in the ocean isn’t left to chance. According to MIT’s press release, “This new laboratory tool creates a microhabitat where tiny sea creatures live, swim, assimilate chemicals and eat each other. It provides the first methodological, sub-millimeter scale examination of a food web that includes single-celled phytoplankton, bacteria and protozoan predators in action.”
In short, it’s a powerful first look at what “may lead to better predictions of marine microbes’ global-scale influence on climate,” according to the press release.
This research is the first of its kind to study carbon flux, the migration from energy and carbon from lower to higher levels in the marine food web/chain. The work was carried out at MIT’s Department of Civil and Environmental Engineering and is being reported in the January print issue of American Naturalist. The work was funded in part by the National Science Foundation.