GEOGRAPHIC VARIATIONS IN BODY SIZE FOR THE NORTHERN ATLANTIC PELAGIC BIOME

Body size is often considered the most important quantitative trait of an individual organism. This is because it can be directly correlated with multiple life-history traits, both physiological (e.g., metabolic rate) and fitness-related (e.g., generation time, fecundity). With body size encapsulating such a significant quantity of biological information, measurements of body size provide a simple metric for assessing the dynamics of ecological networks and the phenotypic response of communities to rapid ongoing global change.

This study undertakes a broad scale assessment of foraminifera body size in the oceanic pelagic biome, focusing on 26 sites in the Northern Atlantic. We generate new high resolution measurements of biovolume for ~55,000 planktonic foraminifera and, using existing plankton tow data, establish both geographic and bathymetric species associations. Correlating these data with physical, chemical and biological environmental variables, we identify the drivers of within species and cross-species body size variation.

To assess the generality of our findings, our results for planktonic foraminifera are considered in light of a new global scale compilation of body size distributions for the pelagic biota. This dataset is comprised of clades that form the majority of pelagic biodiversity and biomass; includes autotrophs, heterotrophs and mixotrophs as well as both unicellular and multicellular groups; and covers 17 orders of magnitude in body mass. Assessed together, these results provide new insights into the biotic and abiotic controls on body size at the macro-scale.