title: The Role of Ocean Currents in the Temperature Selection of Plankton: Insights from an Individual-Based Model.
abstract: Biogeography studies that correlate the observed distribution of organisms to environmental variables are typically based on local conditions. However, in cases with substantial translocation, like planktonic organisms carried by ocean currents, selection may happen upstream and local environmental factors may not be representative of those that shaped the local population. Here we use an individual-based model of microbes in the global surface ocean to explore this effect for temperature. We simulate up to 25 million individual cells belonging to up to 50 species with different temperature optima. Microbes are moved around the globe based on a hydrodynamic model, and grow and die based on local temperature. We quantify the role of currents using the "advective temperature differential" metric, which is the optimum temperature of the most abundant species from the model with advection minus that from the model without advection. This differential depends on the location and can be up to 4°C. Poleward-flowing currents, like the Gulf Stream, generally experience cooling and the differential is positive. We apply our results to three global datasets. For observations of optimum growth temperature of phytoplankton, accounting for the effect of currents leads to a slightly better agreement with observations, but there is large variability and the improvement is not statistically significant. For observed Prochlorococcus ecotype ratios and metagenome nucleotide divergence, accounting for advection improves the correlation significantly, especially in areas with relatively strong poleward or equatorward currents.
authors.affiliation: Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts, United States of America.
authors.forename: Ferdi L
authors.initials: FL
authors.lastname: Hellweger
authors.affiliation: Grantham Institute & Department of Physics, Imperial College London, London, United Kingdom.|ARC Centre of Excellence for Climate System Science, Climate Change Research Centre, University of New South Wales, Sydney, Australia.
authors.forename: Erik
authors.initials: E
authors.lastname: van Sebille
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Calfee
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Chandler
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Erik R
authors.initials: ER
authors.lastname: Zinser
authors.affiliation: Bigelow Laboratory for Ocean Sciences, East Boothbay, Maine, United States of America.
authors.forename: Brandon K
authors.initials: BK
authors.lastname: Swan
authors.affiliation: Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts, United States of America.
authors.forename: Neil D
authors.initials: ND
authors.lastname: Fredrick
mesh_terms: D066264:Datasets as Topic; D017753:Ecosystem; D057446:Hydrodynamics; D015233:Models, Statistical; D010933:Plankton / Q000502:physiology*; D048929:Prochlorococcus / Q000502:physiology*; D012623:Seawater; D013696:Temperature; D014872:Water Movements