Macrosystem community change in lake phytoplankton and its implications for diversity and function

Area of Science:

• Ecology
• Environmental Science
• Aquatic Ecology

Background:

• Lake ecosystems face pressures from eutrophication, land-use, and climate change.
• Understanding phytoplankton community assembly is crucial for aquatic ecosystem health.
• Phylogenetic and trait-based approaches offer insights into community dynamics.

Purpose of the Study:

• To quantify spatio-temporal and scale-dependent impacts of environmental change on lake phytoplankton.
• To analyze species niche dynamics and community assembly processes.
• To account for species traits and phylogenetic constraints in ecological modeling.

Main Methods:

• Utilized lake phytoplankton community data from Finland (1977-2017).
• Applied hierarchical modeling of species communities (HMSC) to 853 lakes.
• Incorporated hierarchical spatial structure and a 'region of common profile' approach to assess compositional and trait changes over time.

Main Results:

• Observed emergence of novel, widespread community composition clusters with distinct trait profiles.
• Identified a strong phylogenetic signal in species' environmental responses.
• Found increased prevalence of smaller species and reduced taxonomic dispersion within current dominant community clusters.

Conclusions:

• Lake phytoplankton communities exhibit profound spatio-temporal structuring and functional differentiation.
• Nationwide reshuffling of communities has occurred, with lakes acting as interconnected metacommunity hubs.
• Spatio-temporal dynamics, rather than solely temporal environmental change, drive novel community assembly.