title: The allometry of the smallest: superlinear scaling of microbial metabolic rates in the Atlantic Ocean.
abstract: Prokaryotic planktonic organisms are small in size but largely relevant in marine biogeochemical cycles. Due to their reduced size range (0.2 to 1 μm in diameter), the effects of cell size on their metabolism have been hardly considered and are usually not examined in field studies. Here, we show the results of size-fractionated experiments of marine microbial respiration rate along a latitudinal transect in the Atlantic Ocean. The scaling exponents obtained from the power relationship between respiration rate and size were significantly higher than one. This superlinearity was ubiquitous across the latitudinal transect but its value was not universal revealing a strong albeit heterogeneous effect of cell size on microbial metabolism. Our results suggest that the latitudinal differences observed are the combined result of changes in cell size and composition between functional groups within prokaryotes. Communities where the largest size fraction was dominated by prokaryotic cyanobacteria, especially Prochlorococcus, have lower allometric exponents. We hypothesize that these larger, more complex prokaryotes fall close to the evolutionary transition between prokaryotes and protists, in a range where surface area starts to constrain metabolism and, hence, are expected to follow a scaling closer to linearity.
authors.affiliation: Centro Oceanográfico de Gijón, Instituto Español de Oceanografía, Gijón, Spain.
authors.forename: Francisca C
authors.initials: FC
authors.lastname: García
authors.affiliation: Universidad de Vigo, Departamento de Ecología y Biología Animal, Carretera Colegio Universitario, Vigo, Spain.
authors.forename: Enma Elena
authors.initials: EE
authors.lastname: García-Martín
authors.affiliation: Departamento de Biología de Organismos y Sistemas, Universidad de Oviedo, Oviedo, Vigo, Spain.
authors.forename: Fernando González
authors.initials: FG
authors.lastname: Taboada
authors.affiliation: Centro Oceanográfico de Gijón, Instituto Español de Oceanografía, Gijón, Spain.
authors.forename: Sofía
authors.initials: S
authors.lastname: Sal
authors.affiliation: Universidad de Vigo, Departamento de Ecología y Biología Animal, Carretera Colegio Universitario, Vigo, Spain.|Estación de Ciencias Marinas de Toralla, Universidad de Vigo, Toralla Island, Vigo, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Serret
authors.affiliation: Centro Oceanográfico de Gijón, Instituto Español de Oceanografía, Gijón, Spain.
authors.forename: Ángel
authors.initials: Á
authors.lastname: López-Urrutia
mesh_terms: D001267:Atlantic Ocean; D001419:Bacteria / Q000145:classification / Q000166:cytology / Q000378:metabolism*; D010933:Plankton / Q000378:metabolism*; D048929:Prochlorococcus / Q000166:cytology / Q000378:metabolism*; D011387:Prokaryotic Cells / Q000378:metabolism; D012623:Seawater / Q000382:microbiology*