PARENT SESSION
Symposium 19: Spatial nonlinearities and cross scale interactions: Cascading effects in the Earth System
Organized by: DC Peters and BT Bestelmeyer
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 517 A, Level 5, Palais des congrès de Montréal

Nonlinear state changes in a coastal pelagic ecosystem.

Ohman, Mark^*,1, Lavaniegos, Bertha^{1, 2}, ¹ Scripps Institution of Oceanography, La Jolla, CA² CICESE, Ensenada, Mexico

ABSTRACT- Upper water column assemblages of planktonic organisms are affected markedly by physical processes in the upper ocean and atmosphere, which act upon multiple scales. They are also altered by density-dependent biotic interactions. The interaction of such processes can generate nonlinear dynamics that make efforts at ecosystem forecasting challenging. In the new California Current Ecosystem LTER site we recognize a number of physical processes influencing the dynamics of zooplankton, including interannual variations dominated by El Nino/La Nina, the interdecadal Pacific Decadal Oscillation, and a multi-decadal secular warming trend. Preliminary results suggest that major nodes or transition points in the system occur when at least two dominant time scales of forcing interact with one another in a consistent positive or negative manner. However, while transitions appear to be initiated by altered physical processes, the persistence of an altered state appears to be maintained by other factors. Future trajectories of this ecosystem will be influenced by the joint occurrence of all major sources of physical forcing acting in the same direction (i.e., the "triple positive" state) which has not previously been observed.

Key words: nonlinear, planktonic, ecosystem, transitions