Oxygen Exchange and Primary Production of Zostera japonica Ascherson et Graebner 1907 Community in the Golubinyi Bay (Sea of Japan)

The net primary production per daylight period (Pn, dl) and dark respiration per day (Rd) of the eelgrass Zostera japonica community were measured in situ by the continuous-flow-system method in the Golubinyi Bay (Sea of Japan) in May-June 2008-2012; the obtained values were Pn = 3.37 g ?(2)/(m(2) dl) and Rd = 7.21 g ?(2)/(m(2) d). The photosynthesis rate of Z. japonica depended on the intensity of photosynthetically active radiation (PAR) and salinity. The gross primary production (Pg) of the Z. japonica community was 6.98g ?(2)/(m(2) d) or 2.62 g C/(m(2) d) at the salinity of 34-17 parts per thousand. With reduction of water salinity to 8-1 parts per thousand, the Pg of the Z. japonica community decreased to 2.17 g O-2/(m(2) d) or 0.81 g C/(m(2) d), because of a lower rate of photosynthesis in plants. The primary production of Z. japonica was 6.10 g O-2/(m(2) d) or 87.4% of the gross production of the community. The ratio of gross production to dark respiration (Pg/R) was approximately 1.0, indicating the balance of autotrophic and heterotrophic processes in the community.