October 16, 2013
How Tiny Organisms Make A Big Impact On Clean Water
Nearly every body of water, from a puddle or a pond to a vast ocean, contains microscopic organisms that live attached to rocks, plants, and animals. These so-called sessile suspension feeders are critical to aquatic ecosystems and play an important role in cleaning up environmental contaminants by consuming bacteria. A study published by Cell Press on October 15 in the Biophysical Journal reveals that by actively changing the angle of their bodies relative to the surfaces, these feeders overcome the physical constraints presented by underwater surfaces, maximize their access to fresh, nutrient-rich water, and filter the surrounding water.
"Our findings will allow scientists to make better estimates about how much water each of these tiny organisms can filter and clean, which can help us to make better estimates about how quickly bodies of water can recover after contamination caused by oil spills and sewage leaks," says lead study author Rachel Pepper of the University of California, Berkeley.
To examine how the tiny organisms overcome these challenges, Pepper and her team used a combination of experiments and calculations. They observed that a protozoan called Vorticella convallaria actively changes its body orientation relative to the surface to which it is attached, in contrast to previous models, which assumed that sessile suspension feeders always feed at a perpendicular angle. The new model revealed that feeding at a parallel or other non-perpendicular angle substantially increases the amount of nutrients the organisms can extract from their surroundings by reducing both fluid resistance and the recirculation of nutrient-depleted water.
"We know very little about the processes microbes use to remove and recycle contaminants," Pepper says. "Our study shows that fluid flows at the scale of individual small organisms, when aggregated, can be important contributors to maintaining the quality of natural waters."
On the Net: