Environmental pressures on Mekong fish: Insights from temporal functional diversity dynamics

Area of Science:

• Ecology
• Environmental Science
• Ichthyology

Background:

• The Mekong River faces significant environmental threats impacting its diverse fish communities.
• Understanding fish community responses to these changes is crucial for effective conservation and management.
• Functional diversity (FD) provides a trait-based approach to assess ecological community structure.

Purpose of the Study:

• To investigate the links between functional diversity dynamics and environmental changes in the Mekong River.
• To identify the key environmental drivers structuring fish communities across four distinct sites.
• To explore the influence of deterministic and stochastic processes on fish community assembly.

Main Methods:

• Utilized trait-based methods and fish monitoring data for 347 species.
• Assessed functional richness (FRic) and functional divergence (FDiv) using standardized effect sizes.
• Employed generalized additive models to identify environmental drivers and community assembly rules.

Main Results:

• Significant environmental changes and shifts in fish community structure were observed across all four sites post-dam construction.
• Deterministic processes, particularly environmental filtering, dominated fish community assembly at most sites, leading to declines in FRic and FDiv, except for the Viet Nam site (VCM).
• Water level was the primary environmental driver, with temperature and total nitrogen as secondary factors; seasonal patterns in FD varied by site.

Conclusions:

• Environmental filtering significantly influences fish community structure in the Mekong River, with dam impacts and other anthropogenic factors playing a role.
• Findings suggest distinct ecological processes (deterministic vs. stochastic) shape fish communities at different sites along the river.
• The study provides insights for developing targeted river management and conservation strategies in the Mekong Basin.