Phytoplankton Morpho-Functional Trait Variability along Coastal Environmental Gradients

Area of Science:

• Marine ecology
• Phytoplankton community dynamics
• Global change impacts on aquatic ecosystems

Background:

• Phytoplankton traits influence ecosystem function and are sensitive to environmental changes.
• Global change drivers like warming and altered water quality impact marine communities.
• Understanding trait-environment relationships is crucial for assessing aquatic ecosystem health.

Purpose of the Study:

• To investigate the relationship between phytoplankton traits and environmental factors (global change, water quality, nutrient availability).
• To assess how temperature, salinity, stratification, water transparency, and nutrient loading affect phytoplankton traits in the Baltic Sea.
• To evaluate the utility of trait-based approaches for monitoring and assessing environmental status.

Main Methods:

• Utilized a trait-based approach combined with generalized additive mixed modeling (GAMM).
• Analyzed summertime monitoring data from the coastal northern Baltic Sea.
• Examined relationships between phytoplankton traits (e.g., nitrogen-fixing, buoyancy, motility, harmfulness) and environmental variables.

Main Results:

• Water temperature was a key driver, positively influencing nitrogen-fixing, buoyant, non-motile, autotrophic phytoplankton, and harmful cyanobacteria.
• Water transparency showed a negative correlation with most studied traits, particularly harmfulness, while benefiting non-harmful and large phytoplankton.
• Nutrient loading source type and total phosphorus (TP) did not show clear relationships with phytoplankton traits, including nitrogen-fixing species.

Conclusions:

• Phytoplankton community structure is significantly influenced by temperature and water transparency, reflecting global and catchment changes.
• Trait-based assessments, considering both absolute biomass and proportional share, are essential for a comprehensive understanding of community shifts.
• The findings support the integration of trait-based metrics into environmental status assessments for effective aquatic ecosystem management.