Innovative methods in small-scale bio-physical oceanography

Plankton--which are the base of the oceanic food-web on which our fisheries depend and remove carbon dioxide from the atmosphere and sequester it in the ocean--live on small scales. Turbulent mixing--which is key to the transport of nutrients and oxygen, as well as greenhouse gases, throughout the ocean and has been directly implicated in the feeding and survival of plankton--happens on small-scales. In addition to being able to alter whole ecosystems (to the benefit or detriment of our fisheries) through shifts in food availability and timing, certain plankton can have immediate impacts on our oceans: harmful algal blooms (HABs) can render waters toxic. Predicting the future ocean hinges on an understanding of small-scale bio-physical processes. Ocean science is driven by observation. Currently theory about small-scale bio-physical processes, particularly plankton-turbulence interactions, remains untested because observational capabilities are lacking. Plankton have been predicted to seek out levels of turbulence that help them find food and mates. Their swimming may be mixing the ocean. However, there is little in situ observational evidence for these ideas because it is difficult to make the measurements on the necessary spatial scales. The proposed research program will marry two innovative techniques, high-frequency broadband acoustics (with can spectrally identify and discriminate between scattering from different types of plankton) and the Video Plankton Recorder / Microstructure profiler (a unique instrument able to observe zooplankton and oceanic microstructure simultaneously in situ). The projects will quantify acoustic scattering from HAB plankton, developing the science and ability to use acoustics as an early warning about the presence of HABs, and evaluate the role of turbulence in the formation of key oceanic feeding habitats (such as the Gully Marine Protected Area and the Roseway Basin Critical Habitat for the endangered North Atlantic Right whale) and in the feeding success of marine zooplankton. Making these observations is critical to gaining a mechanistic understanding of how ecosystems function, which is key to accurately predicting the future ocean.