Abstract
Extensive and expanding oxygen minimum zones (OMZs) exist at variable depths in coastal and open ocean waters. As oxygen levels decline, nutrients and energy are increasingly diverted away from higher trophic levels into microbial community metabolism, resulting in fixed nitrogen loss and production of climate active trace gases including nitrous oxide and methane. While ocean deoxygenation has been reported on a global scale, our understanding of OMZ biology and geochemistry is limited by a lack of time-resolved data sets. Here, we present a historical dataset of oxygen concentrations spanning fifty years and nine years of monthly geochemical time series observations in Saanich Inlet, a seasonally anoxic fjord on the coast of Vancouver Island, British Columbia, Canada that undergoes recurring changes in water column oxygenation status. This compendium provides a unique geochemical framework for evaluating long-term trends in biogeochemical cycling in OMZ waters.
Highlights
Background & SummaryMarine oxygen minimum zones (OMZs) are widespread, naturally occurring water column features that arise from respiration of organic matter in subsurface waters with restricted circulation
Oceanographic surveys in OMZ waters rely on a standard suite of measurements including temperature, salinity, density and conductivity
Measurements of N2O and CH4 can be used to monitor potential climatological impacts of OMZ expansion[9,10,11,12,13,21]. These measurements define geochemical gradients in OMZ water columns that shape the conditions for coupled biogeochemical cycling
Summary
Marine oxygen minimum zones (OMZs) are widespread, naturally occurring water column features that arise from respiration of organic matter in subsurface waters with restricted circulation. We present a compendium of time-series observations encompassing historical O2 measurements[25,33] (Fig. 1a) and more recent monthly monitoring efforts in Saanich Inlet from 2006 through 2014, representing over 100 independent sampling expeditions (Fig. 1b) This compendium contains physical (temperature, salinity, NO3−, NO2−, NH4+, and H2S), dissolved density, irradiance, gas (O2, CO2, N2, and fluorescence), chemical N2O, CH4), and biological (PO43 − , SiO2, (cell counts) parameter data (Fig. 1b,c) useful in comparing to other oceanographic time-series from the Northwest. Tara Oceans[34,35,36] and Bermuda Atlantic Time-series[37] and in the development of biogeochemical models This geochemical compendium is paired with a cognate compendium of multi-omic sequence information (DNA, RNA, protein) focused on microbial diversity, abundance and function.[38] Combined, these compendiums provide a community-driven framework for observing and predicting microbial community repsonses to changing levels of oxygen deficiency extensible to open ocean OMZs
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