Olascoaga, M. J., U. Miami - RSMAS - AMP, Miami, USA, jolascoaga@rsmas.miami.edu
Beron-Vera, F. J., U. Miami - RSMAS , Miami, USA, fberon@rsmas.miami.edu
Brand, L. E., U. Miami - RSMAS , Miami, USA, lbrand@rsmas.miami.edu
Kocak, H. ., U. Miami - Departments of Computer Science and Mathematics, Miami, USA, hk@cs.miami.edu

AN APPLICATION OF LAGRANGIAN COHERENT STRUCTURES TO HARMFUL ALGAL BLOOMS

The largest and most frequent harmful algal blooms (HABs) caused by the toxic dinoflagellate Karenia brevis tend to occur along the southern portion of the West Florida Shelf (WFS). A necessary condition for achieving a high population density is that stretching and folding of fluid elements do not act to significantly reduce the population during the growth phase. It is argued that the presence of a cross-shelf transport barrier may provide favorable conditions for the development of HABs on the WFS by inhibiting expatriate losses and allowing for a greater nutrient buildup on the shoreside of the barrier. The barrier is characterized as a Lagrangian coherent structure (LCS), which is a material line that separates fluid domains with different advection properties. Because the early stages of HABs are usually not detected, there is limited understanding of the environmental conditions that lead to their development. We employ simulated LCSs to trace the early location of a HAB before it was transported to an area where it could be detected by satellite imagery. Then a population dynamics model is used to infer the factors that may have led to its development. Two nearshore nutrient sources are identified, one associated with a coastal upwelling event and the other produced by river runoff. These results show that the use of simulated LCSs and a population dynamics model can enhance our understanding of the early stages of HAB development.

Oral presentation

Presentation is given by student: No
Session #:120
Date: 03-03-2008
Time: 16:00