A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems

Area of Science:

• Marine ecology
• Ecosystem dynamics
• Food web analysis

Background:

• Trophic cascades are crucial ecosystem processes, but regulating factors remain unclear.
• Trophic interactions (TIs) may exhibit scale-dependence and interact across spatial scales.
• Understanding these scale-dependencies is key to deciphering trophic cascade regulation.

Purpose of the Study:

• To investigate the role of spatial scale in trophic cascades.
• To identify and analyze cross-scale interactions (CSIs) within food webs.
• To explore how scale-dependent TIs influence ecosystem structure and function.

Main Methods:

• Analysis of food-web data from 139 stations across 32 bays in the Baltic Sea.
• Identification of a four-level trophic cascade involving piscivores, mesopredators, grazers, and algae.
• Statistical examination of relationships between trophic levels at bay and station scales.

Main Results:

• A four-level trophic cascade was observed, linking piscivores to algae across bay and station scales.
• Piscivore biomass at the bay scale influenced the grazer-algae relationship at the station scale.
• Evidence of cross-scale interactions (CSIs) affecting food web dynamics and vegetation health.

Conclusions:

• Trophic cascades are influenced by TIs operating at multiple spatial scales.
• Cross-scale interactions (CSIs) are significant in structuring ecological communities.
• Incorporating scale-dependence and CSIs enhances understanding of trophic cascade mechanisms.