"Our research pinpoints a mechanism for the formation of these thin layers of phytoplankton, which are analogous to watering holes in a savanna localized areas of concentrated resources that draw a wide range of organisms and thus play a disproportionate role in the ecological landscape," said Stocker, the Doherty Assistant Professor of Ocean Utilization at MIT.
Because motile phytoplankton have different morphologies and swimming abilities, one species may be able to swim through a layer of shear that will capture another. This means that each species could be trapped in a different level of shear, creating a sort of oceanic layered-cake effect, a boon for zooplankton or young fish that feed on specific species.
And when a toxic species of phytoplankton gets trapped in a thin layer, that layer can spawn a harmful algal bloom an explosion in the population of toxic phytoplankton that sickens or kills the larger animals that ingest the cells. Harmful algal blooms are a major source of social and economic concern, particularly near coastal areas, because they are becoming more frequent and cause billions of dollars in annual losses to fishing and recreational industries worldwide.
In a perspective piece accompanying the paper in Science, scientist Daniel Grnbaum of the University of Washington writes: "The authors demonstrate a sort of Peter Principle for algae migrating in shear: cells swim up until they reach their level of instability. At this critical shear level, cells can swim in, but they cannot swim out. The resulting aggregation, in what is arguably an unfavorable microenvironment, may have widespread consequences, as harmful blooms of toxic algae often take the form of thin layers."
Using video-microscopy, Durham and Stocker were able to
|Contact: Elizabeth Thomson|
Massachusetts Institute of Technology