PAOC Colloquium – Yoav Lehahn (Haifa)

“A Lagrangian bird’s eye view on plankton dynamics”
Plankton are ubiquitous drifting organisms that play a critical role in ocean biogeochemical cycles and ecosystem structure and functioning. Since the 1980s the study of plankton have greatly bene-fited from satellites imaging, which provide a synoptic view on the planktonic ecosystem and the oceanic flow in which it is embedded. In recent years, thanks to dramatic technological advance-ments, limitations of satellite data may be overcome by the utilization of drones, providing a very high spatial (centimeters) and temporal (seconds) resolution bird’s eye view on the on the sea sur-face.
Because planktonic systems are embedded within a dynamical landscape with overlapping time-scales, a major challenge when using remote sensing data – from satellites and drones – to study their dynamics is to untangle the footprint of biological processes (such as primary production, graz-ing and mortality) from that of physical processes (such as advection, stirring and mixing). In recent years, much progress has been made in addressing this challenge through Lagrangian analysis meth-ods that describe the changes in water properties along particle trajectories.
Here I will discuss some ways by which application of Lagrangian concepts to the analysis and inter-pretation of remote sensing data contributes to our understanding of plankton dynamics. After demonstrating some of the principles on satellite imaging of phytoplankton blooms, I will discuss new avenues for Lagrangian analysis of data from drones, focusing on its implications for the study of jellyfish. I will describe the methodology and show recent results from an ongoing research aimed at studying the dynamics of jellyfish swarms and their interaction with the oceanic flow, fo-cusing on the highly oligotrophic waters of the southeastern Mediterranean as a case study.

About this series:
The PAOC Colloquium is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars take place on Monday from 12-1pm. Contact paoc-colloquium-comm@mit.edu for more information and Zoom password.