Selection, drift and community interactions shape microbial biogeographic patterns in the Pacific Ocean

Area of Science:

• Microbial ecology
• Oceanography
• Biogeography

Background:

• Microbial communities are crucial for ocean biogeochemical processes.
• Understanding microbial community assembly is vital for predicting ocean ecosystem functions.
• Existing data on microbial biogeography is limited, especially in large ocean basins.

Purpose of the Study:

• To determine the relative importance of ecological mechanisms (selection, dispersal, drift) in shaping microbial communities across the Pacific Ocean.
• To investigate the influence of temperature on these assembly mechanisms.
• To assess the role of species interactions in microbial community structure.

Main Methods:

• Analysis of microbial community composition along a 12,400 km transect in the Pacific Ocean.
• Quantification of selection, dispersal, and drift using ecological modeling.
• Assessment of temperature's impact on the significance of assembly mechanisms.
• Utilizing co-occurrence-based metrics to analyze species interactions and community structure.

Main Results:

• Homogeneous selection is a primary driver (50-60%) for prokaryotic communities in the epipelagic zone, while drift is more significant for particle-associated communities in the mesopelagic.
• Temperature significantly influences the balance between homogeneous selection and dispersal limitation, with their relative importance inverting with temperature differences.
• For larger eukaryotes (>8 µm), homogeneous selection dominates in the epipelagic, whereas drift is predominant at other depths.
• Interaction-adjusted community metrics better explained variations in community composition compared to traditional distance measures.

Conclusions:

• Ecological mechanisms like selection, dispersal, and drift, along with temperature, play critical roles in structuring microbial communities in the Pacific Ocean.
• Species interactions are essential for accurately assessing microbial community assembly and biogeographic patterns.
• These findings enhance our understanding of microbial community dynamics in the largest ocean and their adaptation to global biogeochemical processes.