Respiration and its measurement in surface marine waters

This chapter reviews the current state of knowledge of the process and measurement of microplankton respiration in marine surface waters. The principal approaches are outlined and their potentials and limitations discussed. A global database, containing 1662 observations has been compiled and analyzed for the spatial and temporal distribution of surface water respiration. The database is tiny compared to that of photosynthesis and biased with respect to season, latitude, community structure, and depth. Measurements and models show that the major portions of respiration lies in that attributable to bacteria (12–59%) and to algae (8–70%). The mean of the volumetric rates of respiration in the upper 10 m of the open ocean is 3.3±0.15 mmol O2 m−3 d−1 and that of depth-integrated open-ocean respiration 116±8.5 mmol O2 m−2 d−1. A global estimate of 13.5 Pmol O2 a−1 is derived from the mean depth-integrated rate, which significantly exceeds contemporary estimates of ocean plankton production (2.3–4.3 Pmol O2 a−1). This difference is at variance with the results of mass-balance calculations, which suggest a small difference (ca. 0.18) between oceanic production and respiration. The reasons for this are discussed.