Environmental Filtering Weakens with Trophic Level in Urban Coastal Ecosystems

Area of Science:

• Marine ecology
• Ecosystem network analysis
• Environmental DNA (eDNA) applications

Background:

• Urban coastal ecosystems face increasing pressures and variability.
• Understanding multitrophic biodiversity and ecosystem network responses is crucial but poorly resolved.

Purpose of the Study:

• To investigate spatiotemporal dynamics of marine organisms (metazoans, protists, prokaryotes) in Hong Kong's urban coastal waters.
• To determine how environmental factors and biotic interactions shape community composition and network stability across different habitats.
• To assess the effectiveness of an integrated eDNA-based framework for monitoring urban marine environments.

Main Methods:

• Environmental DNA (eDNA) metabarcoding, visual surveys, flow cytometry, and environmental measurements.
• Permutational multivariate analysis of variance (PERMANOVA) to analyze community composition.
• Co-occurrence network analysis and structural equation modeling to assess network complexity and drivers.

Main Results:

• Environmental control weakened with increasing trophic levels; prokaryotes and protists showed stronger seasonal/spatial influences than benthic fauna and fish.
• Oceanic habitats supported the most complex and stable multitrophic networks, driven by biotic interactions.
• Estuarine habitats were primarily driven by temperature, while transitional habitats lacked clear drivers, indicating a system in flux.

Conclusions:

• A gradient-dependent interplay of environmental filtering and biotic regulation shapes coastal ecosystem stability.
• Integrated eDNA frameworks are valuable for monitoring biodiversity and ecosystem change in urban marine environments.
• Findings provide insights for managing urban marine ecosystems under global change.