Impact of recently upwelled water on productivity investigated using in situ and incubation‐based methods in Monterey Bay

• Published in: Journal of geophysical research. Oceans Vol. 122; no. 3; pp. 1901 - 1926
• Main Authors: Manning, Cara C., Stanley, Rachel H. R., Nicholson, David P., Smith, Jason M., Timothy Pennington, J., Fewings, Melanie R., Squibb, Michael E., Chavez, Francisco P.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-03-2017
• Subjects: Argon; Biogeochemistry; Carbon; Carbon cycle; Carbon dioxide; Communities; Cruises; dissolved gases; Estimates; Fluxes; Geophysics; Greenhouse gases; Incubation period; Isotopes; Marine; marine productivity; Methods; Mineral nutrients; Net Primary Productivity; Nitrification; Nitrogen; Nitrogen isotopes; Nutrient concentrations; Ocean circulation; Ocean-atmosphere interaction; Oceanography; Oceans; Organic carbon; Oxygen; Photosynthesis; Primary production; Productivity; Ratios; Sediment; Sediment traps; Sediments; Steady state; Tracers; Uptake; Uptakes; Upwelling; Water masses; Monterey Bay; INE, USA, California, Monterey Bay
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1002/2016JC012306

Photosynthetic conversion of
CO2 to organic carbon and the transport of this carbon from the surface to the deep ocean is an important regulator of atmospheric
CO2. To understand the controls on carbon fluxes in a productive region impacted by upwelling, we measured biological productivity via multiple methods during a cruise in Monterey Bay, California. We quantified net community production and gross primary production from measurements of
O2/Ar and
O2 triple isotopes (
17Δ), respectively. We simultaneously conducted incubations measuring the uptake of 14C,
15NO3−, and
15NH4+, and nitrification, and deployed sediment traps. At the start of the cruise (Phase 1) the carbon cycle was at steady state and the estimated net community production was 35(10) and 35(8) mmol C m−2 d−1 from
O2/Ar and 15N incubations, respectively, a remarkably good agreement. During Phase 1, net primary production was 96(27) mmol C m−2 d−1 from C uptake, and gross primary production was 209(17) mmol C m−2 d−1 from
17Δ. Later in the cruise (Phase 2), recently upwelled water with higher nutrient concentrations entered the study area, causing 14C and
15NO3− uptake to increase substantially. Continuous
O2/Ar measurements revealed submesoscale variability in water mass structure and likely productivity in Phase 2 that was not evident from the incubations. These data demonstrate that
O2/Ar and
15N incubation‐based NCP estimates can give equivalent results in an N‐limited, coastal system, when the nonsteady state
O2 fluxes are negligible or can be quantified.
Key Points:
We measured gross and net productivity using a combination of in situ gas tracer, incubation, and sediment trap methods in Monterey Bay
Net community production estimates from oxygen/argon ratios and nitrate incubations agreed very well when the system was at steady state
Following the arrival of recently upwelled water to the study area, incubation‐based carbon and nitrogen uptake increased