14 research outputs found
Recommended from our members
Short-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA: A case study of summer 2012
Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45âČN, 158°00âČW) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further extend the temporal resolution of these near-monthly time-series observations, an extensive field campaign was conducted during July-September 2012 at Station ALOHA with near-daily sampling of upper water-column biogeochemistry, phytoplankton abundance, and activity. The resulting data set provided biogeochemical measurements at high temporal resolution and documents two important events at Station ALOHA: (1) a prolonged period of low productivity when net community production in the mixed layer shifted to a net heterotrophic state and (2) detection of a distinct sea-surface salinity minimum feature which was prominent in the upper water column (0-50 m) for a period of approximately 30 days. The shipboard observations during July-September 2012 were supplemented with in situ measurements provided by Seagliders, profiling floats, and remote satellite observations that together revealed the extent of the low productivity and the sea-surface salinity minimum feature in the NPSG
Recommended from our members
Short-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA: A case study of summer 2012
Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45âČN, 158°00âČW) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further extend the temporal resolution of these near-monthly time-series observations, an extensive field campaign was conducted during July-September 2012 at Station ALOHA with near-daily sampling of upper water-column biogeochemistry, phytoplankton abundance, and activity. The resulting data set provided biogeochemical measurements at high temporal resolution and documents two important events at Station ALOHA: (1) a prolonged period of low productivity when net community production in the mixed layer shifted to a net heterotrophic state and (2) detection of a distinct sea-surface salinity minimum feature which was prominent in the upper water column (0-50 m) for a period of approximately 30 days. The shipboard observations during July-September 2012 were supplemented with in situ measurements provided by Seagliders, profiling floats, and remote satellite observations that together revealed the extent of the low productivity and the sea-surface salinity minimum feature in the NPSG
NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton
Nitrogen (N) is a limiting nutrient in vast regions of the worldâs oceans, yet the sources of N available to various phytoplankton groups remain poorly understood. In this study, we investigated inorganic carbon (C) fixation rates and nitrate (NO3â), ammonium (NH4+) and urea uptake rates at the single cell level in photosynthetic pico-eukaryotes (PPE) and the cyanobacteria Prochlorococcus and Synechococcus. To that end, we used dual 15N and 13C-labeled incubation assays coupled to flow cytometry cell sorting and nanoSIMS analysis on samples collected in the North Pacific Subtropical Gyre (NPSG) and in the California Current System (CCS). Based on these analyses, we found that photosynthetic growth rates (based on C fixation) of PPE were higher in the CCS than in the NSPG, while the opposite was observed for Prochlorococcus. Reduced forms of N (NH4+ and urea) accounted for the majority of N acquisition for all the groups studied. NO3â represented a reduced fraction of total N uptake in all groups but was higher in PPE (17.4â±â11.2% on average) than in Prochlorococcus and Synechococcus (4.5â±â6.5 and 2.9â±â2.1% on average, respectively). This may in part explain the contrasting biogeography of these picoplankton groups. Moreover, single cell analyses reveal that cell-to-cell heterogeneity within picoplankton groups was significantly greater for NO3â uptake than for C fixation and NH4+ uptake. We hypothesize that cellular heterogeneity in NO3â uptake within groups facilitates adaptation to the fluctuating availability of NO3â in the environment
Ediacara biota flourished in oligotrophic and bacterially dominated marine environments across Baltica
The environments and food sources that sustained Ediacara biota 575-541 million years ago remain unclear. Here, the authors perform lipid biomarker and isotopic analyses on biota fossil-containing Ediacaran strata from Baltica and propose the presence of a microbial loop bolstered by bacteria