Phytoplankton size diversity and ecosystem function relationships across oceanic regions.

Area of Science:

• Marine ecology
• Biogeochemistry
• Trait-based ecology

Background:

• Trait diversity is crucial for ecosystem functions and services.
• Mechanisms linking trait diversity to ecosystem functions at large scales remain unclear.

Purpose of the Study:

• Investigate the relationship between phytoplankton size composition, primary production, and export production across latitudinal gradients.
• Understand the mechanisms driving these relationships using a functional biogeography approach.

Main Methods:

• Utilized in situ phytoplankton size distribution data.
• Employed a trait-based model within a functional biogeography framework.
• Analyzed data along a broad latitudinal gradient.

Main Results:

• Observed an increase in average phytoplankton size, size diversity, primary production, and export production from low to high latitudes.
• Identified spatio-temporal environmental heterogeneity and a size-based trade-off (nutrient affinity vs. predation avoidance) as key drivers.
• Found that size diversity alone does not directly dictate primary production and export.

Conclusions:

• Environmentally mediated trade-offs are critical mechanisms shaping biodiversity-ecosystem function relationships at large spatial scales.
• Phytoplankton size structure plays a significant role in regulating marine ecosystem functions.
• The interplay between environmental conditions and cellular traits influences large-scale biogeochemical cycles.