A comparison of four methods for determining planktonic community production1

Abstract

Samples from two coastal experimental ecosystems were incubated in vitro and sampled over 24 h. Production rates were measured by the 14C method, the O2 and CO, light-dark bottle methods, and the I80 method. 0, production in the experimental enclosures (volume -1.3 x lo4 liters) was also measured directly.Photosynthetic and respiratory quotients were close to 1 .O. Gross production values determined by 0, light-dark experiments, CO2 light-dark experiments, and I80 were similar. 14C production ranged from 60 to 100% of gross production measured in CO, light-dark experiments, indicating that 14C uptake is not precisely fixed with respect to other measures of community metabolism. There was no evidence that 14C or any other method underestimated the rate of primary production in vitro by more than 40%. Productivities in vitro ranged from 35 to 100% of those in the mesocosm at similar light intensities.In samples from one of the ecosystems, the rate of respiration in the light (calculated from I80 data) was an order of magnitude greater than the rate in the dark. This difference may be ascribed to either photorespiration or light enhancement of mitochondrial respiration.Turnover of microplankton populations in the ocean occurs on time scales of hours to days. Measurements of community turnover rates must be carried out with in vitro incubations, presenting two problems. First, it can never be claimed that processes oc-I

Quantifying photosynthetic rates of microphytobenthos using the triple isotope composition of dissolved oxygen

“…6). (Bender et al 1987 O label in the seawater is so much greater than the biomass that recycling of labeled O 2 is very small and thus the results are insensitive to uncertainties in isotopic respiration factor. This technique has not been applied in O are large and thus are much easier to measure than the natural variations in TOI.…”

Primary productivity and its regulation in the Arabian Sea during 1995

“…A property that can be determined rapidly with considerable precision using C uptake is net daily community particulate primary productivity (Richardson, 1991;Williams, 1993a, b). Disadvantages of this property (as determined by C uptake) are that it is only one component of photosynthetic production because it does not measure dissolved organic productivity (Williams, 1995;Hansell and Carlson, 1998) and it refers not to a single autotrophic process of phytoplankton, but to the net sum of a variety of autotrophic and heterotrophic processes carried out by a community of phytoplankton, bacteria and protozoans (Williams, 1981;Bender et al, 1987;Williams and Lefevre, 1996;Bender et al, 1999;Robinson and Williams, 1999;Laws et al, 2000;Dickson et al, 2001). Advantages of using net daily community particulate primary productivity (as determined by C uptake) are that it has a widely accepted operational de"nition (Peterson, 1980;Williams, 1993b); it has a strong and causal correlation to a variety of biological, chemical and geochemical processes of interest to oceanographers and geoscientists outside the subdiscipline of phytoplankton physiology (Suess, 1980;Pace et al, 1987;Iverson, 1990;Wassman, 1990;Bertrand and Lallier-Verges, 1993); and it covaries with the process captured in the Odum (1971) de"nition (Laws, 1991;Laws et al, 2000).…”

Respiratory losses in the light in a marine diatom: Measurements by short‐term mass spectrometry

“…As a result there are few direct measurements of phytoplankton respiration during photosynthesis (e.g. Weis and Brown 1959;Bender et al 1987;Bate et al 1988). The most common approach in estimating the rate of respiration during photosynthesis is to determine 0, consumption in the dark immediately before or after a period of photosynthesis.…”