Marine Bacterioplankton Seasonal Succession Dynamics Carina Bunse, Jarone Pinhassi  Trends in Microbiology  Volume 25, Issue 6, Pages 494-505 (June 2017) DOI: 10.1016/j.tim.2016.12.013 Copyright © 2017 The Authors Terms and Conditions

Figure 1 World Map of Key Oceanographic Features and Selected Microbial Sampling Stations. Oceanographic features shown are ocean gyres (arrows) and eastern boundary upwelling zones (green). Also shown are long-term sampling stations for microbial oceanography (yellow filled circles). Polar regions (66°–90° north and south), temperate regions (33°–66° north and south), and tropical regions (33° north to 33° south). Abbreviations: BATS, Bermuda Atlantic time-series study; EQ, equator; HOT, Hawaiian Ocean time-series; LMO, Linnaeus Microbial Observatory; MOLA, Microbial Observatory of the Laboratoire Arago; SPOT, San Pedro Ocean time-series. Trends in Microbiology 2017 25, 494-505DOI: (10.1016/j.tim.2016.12.013) Copyright © 2017 The Authors Terms and Conditions

Figure 2 Schematic Overview of Environmental Factors Influencing Seasonal Succession of Marine Bacterioplankton in Polar, Temperate, and Tropical Regions. In polar regions, darkness and ice cover limit phytoplankton primary production in winter. In spring, phytoplankton and bacteria colonize the sea-ice, seeding the water column when ice cover breaks to form pronounced spring blooms. In temperate regions, late autumn/winter overturn of water column, together with land runoff, increases nutrient concentrations in surface waters, inducing spring phytoplankton blooms when light increases. During temperate summers, water column becomes stratified, leading to successional changes in bacterial community composition. Water column destabilization in early autumn induces new phytoplankton bloom, with repercussions for the bacterial community. In tropical regions, water masses in offshore areas are mixed by wind, eddies, or ocean currents, whereas coastal areas are often influenced by upwelling of nutrient-rich deep-water masses. During summer, water masses are stratified in shallow depths, and temperatures are high in surface waters. During autumn, summer conditions transition to winter conditions; however, this time of the year is seldom in focus for microbial studies and is depicted by ‘?’. Overall, the phytoplankton production of DOM triggers growth of bacterioplankton, and seasonal changes in organic matter concentrations and composition, together with changes in inorganic nutrient concentrations, are the key drivers of bacterioplankton succession. In all regions occasional insertions of nutrients during stratified periods (i.e., summer) can induce short-term blooms of phytoplankton and bacteria. Trends in Microbiology 2017 25, 494-505DOI: (10.1016/j.tim.2016.12.013) Copyright © 2017 The Authors Terms and Conditions

Figure 3 Seasonal Succession of Marine Bacterioplankton. (A) Changes in relative abundances of bacterial populations (OTUs) in the temperate Baltic Sea during 2011; redrawn from Lindh et al. [28]. Chlorophyll a (Chla) concentrations are indicated as a green-filled area. OTU_002 (LMO11_000002, Synechococcus), OTU_004 (LMO11_000004, Flavobacteriaceae), OTU_006 (LMO11_000006, Actinobacteria; hgcI clade), OTU_008 (LMO11_000008, Actinobacteria; CL500-29 marine group), OTU_101 (LMO11_000101, Proteobacteria; EGEAN-169 marine group). Note differences in timing, duration, and amplitude of changes in abundances over time. (B) Schematic visualization of the influence of environmental factors on bacterial population dynamics. The effects of environmental factors are indicated by several ‘disturbances’ (these could be, e.g., nutrient input or change in stratification) that each affects the abundance of particular bacterial populations in different ways over time, ultimately defining patterns of seasonal succession. The term ‘populations’ here, and elsewhere, is used to denote fairly narrow biological entities, such as species, ecotypes, or strains. The dotted sections of abundance curves indicate the length of population responses to disturbances. Disturbance 1 leads to a short but strong increase of the ‘grey’ population while the ‘yellow’ population remains rare. The ‘red’ and ‘blue’ populations are abundant and can substitute for each other as dominants through time. While disturbance 1 barely impacts on the ‘red’ and ‘blue’ populations, the ‘blue’ population increases after disturbance 2–potentially fuelled by the preceding increasing abundances and a competitive advantage over the ‘red’ ecotype. During disturbance 3, on the other hand, the ‘red’ population has a competitive advantage and increases in abundance while the ‘blue’ population decreases. The ‘yellow’ population remains stably rare irrespective of the disturbances. Trends in Microbiology 2017 25, 494-505DOI: (10.1016/j.tim.2016.12.013) Copyright © 2017 The Authors Terms and Conditions