eDNA Metabarcoding Reveals Diel Connectivity Dynamics of Fish Communities in Xincun Lagoon, Hainan

Area of Science:

• Marine Ecology
• Ichthyology
• Environmental DNA (eDNA) applications

Background:

• Coastal lagoons are critical transitional ecosystems supporting biodiversity and ecosystem functions.
• Understanding diurnal fish community connectivity in lagoons and their connection to adjacent waters is limited.
• Lagoon-sea connectivity is essential for regional biodiversity and ecosystem services.

Purpose of the Study:

• To investigate the spatiotemporal dynamics of fish communities in Xincun Lagoon, China, on a diurnal timescale.
• To examine the spatial functional differentiation of fish communities along a lagoon-inlet-offshore gradient.
• To assess the potential role of the tidal inlet as a corridor for fish movement between lagoon and open waters.

Main Methods:

• Established six sampling stations along an environmental gradient from lagoon interior to open sea.
• Conducted repeated diurnal sampling at six time points using environmental DNA (eDNA) metabarcoding.
• Analyzed fish community composition, spatiotemporal dynamics, and diversity fluctuations.

Main Results:

• Identified clear spatial functional differentiation of fish communities across the environmental gradient.
• The tidal inlet showed the highest rate of community temporal change and diversity fluctuation, peaking in the evening.
• Mangrove creek areas served as biodiversity hotspots with stable community structures, while the inlet facilitated diurnal fish movement.

Conclusions:

• Environmental DNA (eDNA) metabarcoding effectively captured fine-scale diel variations in fish community composition and distribution.
• The tidal inlet likely functions as a crucial corridor linking lagoon and offshore fish habitats.
• Findings provide a valuable reference for using eDNA technology to study fine-scale ecological connectivity in coastal systems.