Currently, the shallow basins with Zostera marina L. meadows are considered as absorbers of atmospheric carbon dioxide, capable of restraining an increase in its concentration. Due to its high primary productivity, eelgrass releases a large amount of oxygen into the environment. To establish the peculiarities of production activity in shallow-water basins, covered with Z. marina meadows, we conducted monitoring of hydrological and production indicators with different measurement intervals on the example of the Voevoda Bay (the Amur Bay, the Sea of Japan). Observations were carried out for eight and a half months (22.09.2012–07.06.2013). Measurements of temperature, salinity, chlorophyll fluorescence, and turbidity were carried out in Z. marina meadows at a depth of 4 m every three hours by a Water Quality Monitor hydrological station. Dissolved oxygen content was determined every hour by an optical oxygen sensor ARO-USB. Two types of oxygen concentration variability were established: 1) seasonal variability, mostly resulting from seasonal variations in the environment; 2) daily variability during the freeze-up period, mostly determined by the intensity of photosynthetically active radiation penetration into sub-ice water. In the autumn season, low oxygen concentrations, up to hypoxic level, were recorded. In the winter and spring seasons, the oxygen content was, as a rule, at 100–130 % of saturation. High daily variability was observed during the freeze-up period, with no snow coverage. In February, the range of daily fluctuations of oxygen concentration reached 730 μmol·kg−1, with 3-fold supersaturation regarding atmospheric O2. As established, the maximum rate of oxygen production, relative to 1 g of Z. marina wet weight, is 6.5 mg O2·h−1·g−1. High daily dynamics of oxygen in seawater is analyzed in relation to eelgrass physiological peculiarities (air lacunae play an important role in oxygen dynamics in the environment), as well as to short-period tides.
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Development of A New Method for Measuring the Oxygen Content of the Oxide Superconductor YBa2Cu3Oy with a Dissolved Oxygen Sensor
