Jan 12, 2012

Ocean windmills, turbulence avoidance and zooplankton.

A recent paper by  University of New Hampshire professor James Pringle What is the windage of zooplankton? Turbulence avoidance and the wind-driven transport of plankton reveals how strategies used by migrating zooplankton to get where they're going can have unexpected consequences when the wind blows or stops blowing.  Something that would-be deepwater windpower extractors need to keep in mind

As Bay Blog readers know,  Maine's East and West Coastal Currents are migratory thruways for the zoooplankton phase larvae of lobsters, sea scallops and many other marine animals These currents rise in the Bay of Fundy, passing Maine, New Hampshire and Massachusetts and interfacing with other currents deeper in the Gulf of Maine. See currents here (flash video)

 Dr Pringle has discovered that migrating zooplankton avoid turbulent waters while travelling. When they encounter it, they  descend and try going under the turbulence, even if their phytoplankton prey is  more abundant in the turbulent water.

But these peace-seeking plankton can run into a problem. When they leave the surface currents they have been migrating on, and are no longer near the surface, they leave the migratory thruway they were in.   If they go too deep while trying to go under the turbulence, they may come into contact with and settle upon the seafloor ecosystem at that location. Or they may be washed outward to settle on the archipelagoes of seamounts of the Gulf of Maine - while their siblings continue down the Maine Coastal Current.

It is not  unreasonable to hypothesize that the sea surface turbulence and water column turbulence and destratification stimulated by operating deepwater ocean windmills  will be just what zooplankton avoid. and finding it impossible to go under the

What is the windage of zooplankton? Turbulence avoidance and the wind-driven transport of planktonBy James M. Pringle, UNH
ABSTRACT
Observations of turbulence avoidance in zooplankton are compared to estimates of the wind-driven turbulence in the upper ocean. Turbulence avoidance is found to prevent the transport of zooplankton in the surface Ekman layer at realistic wind speeds.Plankton that avoid turbulence by moving deeper are no longer transported by the wind-driven Ekman currents near the surface because they are no longer near the surface. Turbulence avoidance is shown to lead to near-shore retention in wind-driven upwelling systems, and to a reduction of the delivery of zooplankton to Georges Bank from the deeper waters of the Gulf of Maine."
End of abstract



No comments: