The interplay between aquatic optics, phytoplankton photophysiology and ecology

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The first objective of the research proposed is to understand how light interacts with particles in the ocean to lead to the light observed by satellites. The colour of this light in turn tells us about the constituents of the ocean and lakes. A particularly important process, backscattering, is when particles return light that is incident on them backwards toward the light source. Here we are interested at the light coming from the Sun and emitted back towards the sky. This proposal aims specifically at understanding more precisely which particles are responsible for the majority of this backscattering in the ocean and specifically how phytoplankton change their efficiency at backscattering throughout the day. We hope to then use the information from that light as it is measured by satellites to learn about the particles in the ocean. In addition, When sunlight impinges on phytoplankton in the ocean, a part of this light is reemitted as red light, the fluorescence of chlorophyll, and can be measured by satellites. Because the efficiency with which phytoplankton emit this light depends on their health, measuring the light using satellite could provide information about the health of phytoplankton across the whole ocean. In this proposal we also aims specifically at understanding how we can use satellite that measure many time a day this fluorescence to infer the health of the phytoplankton. The second objective of this proposal is to understand how lakes are affected by humans. To do this we use a large dataset that has been collected in the NSERC Canadian Lake Pulse Network in more than 650 lakes and relate the species present in the phytoplankton to the human impacts on the lakes to examine this key component of lakes is changing. In addition we use scenarios to examine how lakes may change in the future with climate change.**