Ecological Processes Shaping Marine Microbial Assemblages Diverge Between Equatorial and Temperate Time-Series.

Area of Science:

• Marine microbial ecology
• Oceanography
• Molecular ecology

Background:

• Marine microbial communities are shaped by deterministic and stochastic processes.
• Understanding latitudinal variations in these processes is limited due to observatory location biases.
• Long-term data from diverse latitudes are crucial for global microbial dynamics assessment.

Purpose of the Study:

• To compare coastal microbial communities from tropical and temperate marine time-series stations.
• To investigate latitudinal differences in taxonomic composition, temporal variability, and ecological assembly.
• To assess the influence of environmental and biotic factors on microbial community structure across latitudes.

Main Methods:

• Utilized standardized molecular protocols for 16S and 18S rRNA gene sequencing.
• Analyzed two size-fractions (0.22-3 μm and >3 μm) over 41 months.
• Compared data from a tropical site (Equatorial Atlantic, 6°S) and a temperate site (Mediterranean Sea, 41°N).

Main Results:

• Temperate communities displayed strong seasonal turnover, higher beta-diversity, and greater environmental coupling (temperature, daylength).
• Tropical communities were compositionally stable, dominated by biotic factors and stochastic processes (contingency, drift).
• These patterns held across domains and size-fractions, with stronger selection in prokaryotes and smaller fractions.

Conclusions:

• Latitudinal gradients significantly influence marine microbial community assembly processes.
• Tropical microbial communities are more resilient to environmental variability due to stochastic dominance.
• Integrating underrepresented latitudes into global monitoring is vital, especially with climate change impacts.