MEPS 180:23-36 (1999)  -  doi:10.3354/meps180023

ABSTRACT: The rates of plankton community production and respiration were determined from in vitro changes in dissolved inorganic carbon and dissolved oxygen and the incorporation of NaH¹⁴CO₃ at a coastal site in East Antarctica between 16 December 1993 and 12 February 1994. The breakout of seasonal fast ice was associated with a succession of dominant phytoplankton from Cryptomonas to Phaeocystis to a diatom assemblage. Gross production reached 33 mmol C m^-3 d^-1 and ¹⁴C incorporation peaked at 24 mmol C m^-3 d^-1 on 23 January 1994, at the time of the chlorophyll a maximum (22 mg chl a m^-3). Dark community respiration reached its maximum (13 mmol C m^-3 d^-1 ) 4 d later. Photosynthetic rates calculated from ¹⁴C incorporation were significantly lower (17 to 59%) than rates of gross production. The derivation of plankton processes from changes in both dissolved oxygen and dissolved inorganic carbon allowed the direct measurement of photosynthetic and respiratory quotients. A linear regression of all data gave a photosynthetic quotient of 1.33 ± 0.23 and a respiratory quotient of 0.88 ± 0.14. Concurrent determinations of bacterial, heterotrophic dinoflagellate, nanoflagellate and ciliate respiration could account for 15 to 58% of measured dark community respiration. This study has improved the sparse data set of plankton respiration measurements, confirmed that heterotrophic respiration is a significant process in the carbon flux of coastal Antarctic waters and achieved a first apportionment of community respiration to the major microbial groups in this region.

KEY WORDS: Photosynthesis · Respiration · Plankton · Antarctic