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Project Summary: Since 1988, the Hawaii Ocean Time-series (HOT) program has provided information on time variability in biogeochemical and physical processes in one of Earth's largest ecosystems, the North Pacific Subtropical Gyre (NPSG). The program is built around interdisciplinary shipboard sampling and data collection at near monthly intervals (10 cruises/year) at the open ocean site Station ALOHA (22.75N, 158W). The multi-investigator program is based at the University of Hawaii (UH), with key long-term partners at Oregon State University (OSU), Montana State University (MSU), Scripps Institution of Oceanography (S10), and more recently (since 2004) Woods Hole Oceanographic Institution (WHOI). Measurements conducted by HOT continue to transform our view of linkages between ocean biogeochemistry, plankton ecology, and physical processes in the NPSG. Foremost among the program objectives are to quantify time-varying (seasonal to decadal) changes in reservoirs and fluxes of carbon (C) and associated bioelements; and identify processes controlling air-sea C exchange, rates of C transformation through the planktonic food web, and fluxes of C into the ocean's interior. This subcontract will support regular program analyses of dissolved organic carbon and total dissolved nitrogen in seawater samples collected on near monthly HOT cruises. In addition, the subcontract includes funds for analyses of several years of samples previously collected by HOT to establish a new analytical baseline for these inventories of carbon and nitrogen.
University of California Santa Barbara Project Work: Under this subcontract, Dr. Craig Carlson at the University of California Santa Barbara (UCSB) will oversee the post cruise analyses of dissolved organic carbon and total dissolved nitrogen from seawater samples collected on Hawaii Ocean Time-series (HOT) cruises to Station ALOHA. The HOT program routinely collects seawater samples for these analyses, and Dr. Carlson's laboratory is internationally recognized for these analyses. The subcontract includes analyses of approximately —1200 seawater samples collected between 2010 and 2014 for dissolved organic carbon, and —480 samples for analyses of total dissolved nitrogen from the surface 200m. The contract covers all necessary analytical standardization for these measurements, quality control of resulting data, partial support for analysts and Dr. Carlson, and required consumables for post cruise analyses. All materials and support required for at sea collection and shipping of samples to UCSB will be covered by the HOT program. Analyses of the backlog seawater samples will occur over the initial —1.5 year period of the subcontract (January 2015-July 2016). Additional support included in this subcontract includes necessary support for analyses of samples routinely collected on the near-monthly HOT program cruises between January 2015 and July 2018. This would include —30 samples per cruise for DOC analyses and 12 samples per cruise for total dissolved nitrogen analyses. These analyses will occur over the remaining period of the contract (through July 31, 2018).
In keeping with the HOT program data dissemination requirements, Dr. Carlson will provide quality controlled measurements to the University of Hawaii in a timely manner for subsequent dissemination to the public via the HOT program website and the NSF funded BCO-DMO data repository. In addition, Dr. Carlson will be included in regular HOT program communications regarding project science.