Title:

Microbial Respiration Measured in the Gulf of Maine During a 21-Day Expedition

Marine microbes compose ~98% of all biomass in the global ocean and are good indicators of environmental changes. Marine microbes are at the base of the entire marine food web. Thus, marine microbes control energy flux in the global ocean and affect the trophic levels above them. The microbial carbon pump (MCP) utilizes dissolved carbon present in the water column from other biogeochemical processes to produce refractory dissolved organic carbon (RDOC). RDOC persists in the water column on a timescale of hundreds to thousands of years. The ocean is a voluminous carbon sink for anthropogenic carbon. The influence on energy flux and carbon sequestration from marine microbes make them an area of scientific research. The focus of this study was microbial respiration in the Gulf of Maine measured over a 21-day research expedition. Samples were collected at various stations in the Gulf of Maine on the East Coast Ocean Acidification cruise (ECOA-3). INT reduction assay procedure was used for each sample. Two depths were collected at each station, the surface and the chlorophyll maximum depth. For each depth sample, two size classes of microbes were analyzed: 0.2-0.8µm and >0.8µm. There were four samples at each station collected in total. Temperature, depth, and microbe size were analyzed. There was no correlation found between respiration and temperature. At the majority of stations, for a given station, greater respiration occurred at the chlorophyll max. depth and in the >0.8 µm size class. Further research could include the influence of other environmental factors on respiration such as pH, available sunlight, and nutrient input.

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