The Arctic picoeukaryote <i>Micromonas pusilla</i> benefits synergistically from warming and ocean acidification

Abstract

Abstract. In the Arctic Ocean, climate change effects such as warming and ocean acidification (OA) are manifesting faster than in other regions. Yet, we are lacking a mechanistic understanding of the interactive effects of these drivers on Arctic primary producers. In the current study, one of the most abundant species of the Arctic Ocean, the prasinophyte Micromonas pusilla, was exposed to a range of different pCO2 levels at two temperatures representing realistic current and future scenarios for nutrient-replete conditions. We observed that warming and OA synergistically increased growth rates at intermediate to high pCO2 levels. Furthermore, elevated temperatures shifted the pCO2 optimum of biomass production to higher levels. Based on changes in cellular composition and photophysiology, we hypothesise that the observed synergies can be explained by beneficial effects of warming on carbon fixation in combination with facilitated carbon acquisition under OA. Our findings help to understand the higher abundances of picoeukaryotes such as M. pusilla under OA, as has been observed in many mesocosm studies.

Cell explosions: single cell death triggers an avoidance response in local populations of the ecologically prominent phytoplankton genusMicromonas

“…Diffusion from an initial Gaussian distribution, where the detection threshold of the cells will dictate the detected radius of the spreading patch (insert). tic waters to Norweigian fjords, the coast Plymouth and even the Caribbean [25][26][27][28][29][30][31]. This globally dominant organism was the first reported case or viral destruction of a marine phytoplankton [32], and has established itself as a model system for host-virus dynamics since the discovery of its own dedicated lytic virus named the "Micromonas pusilla virus" (MPV) [33][34][35][36].…”

A phosphate starvation response gene (psr1-like) is present and expressed in Micromonas pusilla and other marine algae

“…Here, we use a combined metabolomic and comparative genomic approach to 100 investigate the impact of P-deficiency on the physiology of Micromonas pusilla 101 CCMP1545. Many metabolites are produced by metabolic pathways under genetic 102 regulatory control (e.g., de Carvalho & Fernandes, 2010; Markou & Nerantzis, 2013); 103 thus, our approach complements recent physiological, transcriptional, and proteomic 104 work (Hoppe et al, 2018;Guo et al, 2018) and provides mechanistic insight into the 105 physiological response to P-deficiency and its underlying genetic regulation. We used a 106 targeted metabolomics approach to analyze the suite of intracellular and extracellular 107 molecules produced by M. pusilla.…”

“…are 66 members of the "green" lineage (Chlorophyta), a monophyletic group including land 67 plants, and are important marine primary producers (Li,1994). Recent culture 68 experiments with Micromonas pusilla (Hoppe et al, 2018) The Chlorophyta share common ancestry with land plants, stemming from a 81 single endosymbiotic event, in contrast to more distantly related phytoplankton groups 82 such as diatoms and haptophytes, which are hypothesized to have undergone multiple 83 endosymbioses (Falkowski et al, 2004;Lewis & McCourt, 2004). Consequently, their 84 physiological response to nutritional stressors, like P-deficiency, may share more traits 85 with land plants than with other algal taxa.…”

Capacity of the common Arctic picoeukaryote Micromonas to adapt to a warming ocean

“…Micromonas is a common and often dominant member of phytoplankton communities in the Arctic (Not et al 2005;Lovejoy et al 2007;Balzano et al 2012;Simon et al 2017). Field data and short-term acclimation experiments indicate that both warming and ocean acidification may increase the growth rate and ecological role of Micromonas in the Arctic (Lovejoy et al 2007;Li et al 2009;Hoppe et al 2018). There is evidence that phytoplankton may have the capacity to evolve, altering their responses to changing conditions (e.g., Schaum et al 2016;Walworth et al 2016).…”