Both respiration and photosynthesis determine the scaling of plankton metabolism in the oligotrophic ocean

Despite its importance to ocean–climate interactions, the metabolic state of the oligotrophic ocean has remained controversial for 415 years. Positions in the debate are that it is either hetero- or autotrophic, which suggests either substantial unaccounted for organic matter inputs, or that all available photosynthesis (P) estimations (including 14C) are biased. Here we show the existence of systematic differences in the metabolic state of the North (heterotrophic) and South (autotrophic) Atlantic oligotrophic gyres, resulting from differences in both P and respiration (R). The oligotrophic ocean is neither auto- nor heterotrophic, but functionally diverse. Our results show that the scaling of plankton metabolism by generalized P:R relationships that has sustained the debate is biased, and indicate that the variability of R, and not only of P, needs to be considered in regional estimations of the ocean’s metabolic state.

Effect Of Temperature On The Respiration Rate Of Meiofauna

The effect of temperature on respiration rate has been established, using Cartesian divers, for the meiofaunal sabellid polychaeteManayunkia aestuarina, the free-living nematodeSphaerolaimus hirsutus and the harpacticoid copepodTachidius discipes from a mudflat in the Lynher estuary, Cornwall, U.K. Over the temperature range normally experienced in the field, i.e. 5–20° C the size-compensated respiration rate (R c) was related to the temperature (T) in °C by the equation Log10 R c=-0.635+0.0339T forManayunkia, Log10 R c=0.180+0.0069T forSphaerolaimus and Log10 R c=-0.428+0.0337T forTachidius, being equivalent toQ 10 values of 2.19, 1.17 and 2.17 respectively. In order to derive the temperature response forManayunkia a relationship was first established between respiration rate and body size: Log10 R=0.05+0.75 Log10 V whereR=respiration in nl·O2·ind-1·h-1 andV=body volume in nl. TheQ 10 values are compared with values for other species derived from the literature. From these limited data a dichotomy emerges: species with aQ 10≏2 which apparently feed on diatoms and bacteria, the abundance of which are subject to large short term variability, and species withQ 10≏1 apparently dependent on more stable food sources.

Respiration Of The Meiobenthic Harpacticoid Copepod Tachidius-Discipes Giesbrecht From An Estuarine Mudflat

The relationships between respiration (R) and body volume (V) for all developmental stages of the harpacticoid copepod Tachidius discipes Giesbrecht have been investigated. The relationships for laboratory-reared animals and animals from the field are significantly different. They are: logR = −0.07 + 1.10 logV for laboratory-reared animals and log R = −0.10 + 0.82 logV for field animals. The effect of temperature on the respiration rate of adult males, over the temperature range 5–20°C, was described by a Q10 of 2.09 ± 0.24. The respiration rate of an adult T. discipes is very similar to that of a similar sized nematode from the same field site and is compared with published data for other harpacticoids.