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Marine Seasonal Succession Dynamics
As bacterial populations have unique metabolisms and resource preferences, the use of high-resolution time-series analysis of bacterial compositions allows for the identification of patterns in seasonal bacterial succession. Differences in bacterial community compositions give rise to particular permutations of interspecies bacterial interactions with photosynthetic phytoplankton, protist grazers, and phages thereby impacting seasonality dynamics. Statistical methods used to verify patterns in population dynamics and composition are demonstrated to be replicable over some years, and environmental factors served as predictors of these temporal patterns. Most research activity for bacterioplankton currently occurs in the temperate waters of the northern hemisphere from 30°N to the Arctic Circle at 66°N.

Seasonal Succession in Temperate Regions
As seasonal successions of phytoplankton populations follow a consistent recurring pattern, bacterial dynamics and phytoplankton succession can be correlated. In general, seasonal changes in bacterial composition follow changes in temperature and chlorophyll a, while nutrient availability limits bacterioplankton growth rates. During water column mixing in late autumn/winter, nutrients brought to the surface kicks start a distinct diatom spring bloom followed by dinoflagellates. After the spring bloom, bacterial production and growth become elevated due to the release of Dissolved organic matter (DOM) from phytoplankton decay. In this early succession stage, members of the class Flavobacteria (Bacteroidetes) are typically the dominant components of the bacterial community. Genome analysis and meta-transcriptomics have uncovered the presence of bacteria containing multiple hydrolytic enzymes facilitating the degradation and assimilation of DOM. During spring blooms, some members of the Roseobacter clade (Alphaproteobacteria) and some Gammaproteobacteria are usually associated with DOM degradation. As temperatures increase and the nutrients from the spring bloom gets depleted, smaller phytoplankton and cyanobacteria grow in the now oligotrophic waters.

As waters become stratified in summer, Roseobacter, SAR86 (Gammaproteobacteria), and SAR11 (Alphaproteobacteria) clades of bacteria increase in abundance. The frequently observed autumn diatom/dinoflagellate blooms are correlated with supplementary nutrient inputs and high-frequency sampling in the Baltic Sea found that in autumn, Actinobacteria generally increase followed by different autumn-specific Flavobacteria, SAR11, and Planctomycetes.

In the Mediterranean Sea, deep winter mixing allows members of the SAR11 clade to achieve increased diversity as the oligotrophic populations that once dominated during the summer stratification die off slowly. Among archaea in the Mediterranean Sea, Thaumarchaeota Marine Group I (MGI) and Euryarchaeota Marine Group II (MGII.B) populations became dominant in winter. While in the Baltic Sea, winter mixing brings Epsilon-proteobacteria and archaea populations to the surface from their deep habitat.