Exploring the sources, sinks and uptake of carbon and nitrogen in the coastal ocean

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The ocean plays an important role in the economy and culture of Canada. Rising atmospheric temperatures, changing weather patterns, and alterations in human activities are fueling changes on land that directly impact the chemistry and productivity of ocean ecosystems. Photosynthetic microorganisms called phytoplankton form the base of the ocean food web and are critical to the sequestration of carbon dioxide from the atmosphere. Shifts in the concentration and composition of elements like carbon and nitrogen, key components of all life on earth, can promote or inhibit phytoplankton growth and thus ocean productivity. Variations in the types of phytoplankton, their abundance and how fast they grow can also have substantial ramifications for aquatic food webs, biogeochemical fluxes, and climate feedbacks. Therefore, research that will lead to a deeper understanding of current processes and enhanced predictive capabilities of future productivity is paramount. By coupling in situ ecosystem observations with explicit experimentation the proposed research program will uncover linkages between key environmental change variables, elemental cycles and ocean productivity. This program will investigate the impacts of climate change, variations in microbial physiology and direct human influence (via changes in industry and land-use) on phytoplankton and bacterial growth by identifying the factors and thresholds that impact their ability to use different carbon and nitrogen sources. Specifically, it will assess the physiological capabilities of existent and emergent microorganisms, characterize the composition of land-based chemical inputs, identify regions most at risk to changes in water chemistry, and determine incremental improvements that will achieve the best long-term ecological and economic benefits. This will enable a fundamental understanding critical to predicting future changes in marine ecosystems and connect upstream changes to their down-stream consequences. The results will be of interest to climate and ecosystem modelers, industries, and management and governmental agencies. The contribution to the modeling community will be carbon and nitrogen utilization, fixation and regeneration rate measurements required for accurate ecosystem models capable of predicting environmental change effects on ocean productivity and global elemental cycles. This research will contribute economically through its connection to the expanding aquaculture industry. Knowing where not to establish an aquaculture facility will help growers be more productive over the long term. This work will also serve to inform management decisions by identifying and prioritizing critical natural and anthropogenic chemical inputs that need to be reduced or mediated in the future to maintain and improve ecosystem health and productivity.