Comparison of primary production and pelagic community respiration rates in the coastal zone of the Gulf of Gdańsk

The organic matter production/respiration balance in the coastal water column was examined, both the primary production and community respiration being measured with the oxygen light-and-dark bottle method. Community respiration (CR) was always lower than the gross primary production (GPP) measured at a standard light intensity of 390 μE m−2 s−1, which amounted, on average, to 30% of GPP. During most of the in situ sampling period, the coastal system (6–7 m depth) was found to be autotrophic, with depth-integrated GPP ranging from 6.7 mmoles O2 m−2 d−1 in December to 214.2 mmoles O2 m−2 d−1 in August, and CR ranging correspondingly from 6.0 to 177.7 mmoles O2 m−2 d−1. However, on some occasions heterotrophic conditions were recorded: depth-integrated GPP