Cellular abundances of bacterioplankton and eukaryotic picoplankton measured by flow cytometry in water samples collected on NOAA Ship Ronald H. Brown during the West Coast Ocean Acidification Cruise led by the Pacific Marine Environmental Laboratory (PMEL) in the northern California current ecosystem from 2016-05-24 to 2016-06-16 (NCEI Accession 0265154)

Changes in ocean conditions such as chemical and thermal shifts are habitat pressures on marine organisms. As the basis of the marine food web, microorganisms such as bacteria and phytoplankton are responsible for important biogeochemical processes, such as nutrient cycling, and the primary production. They are also part of the environment surrounding aquatic organisms such as marine mammals, and serve as a source of both beneficial and harmful microbes associated with larger organisms. Due to their small size and direct physiological interactions with seawater, these microorganisms can rapidly respond to environmental changes, resulting in shifts in community composition and in relative abundances of community members. Shifts at these trophic levels can cause a ripple effect in the structure and function of the ecosystem for coastal and offshore species. Most assessments of biological responses to ocean acidification (OA) have been performed by controlled conditions, and there have been few opportunities to evaluate real-world relationships between biology and OA. This project leverages the sampling and chemical analyses conducted during the northern leg of the 2016 West Coast Ocean Acidification Cruise led by the Pacific Marine Environmental Laboratory (PMEL) to document ocean chemistry in the California Current during a period of likely coastal upwelling and greater ocean acidification. During that cruise, water from the same water samples that were used for chemical measurements by PMEL were preserved & analyzed for cellular abundances of bacterioplankton and eukaryotic picoplankton.