Ecosystem engineering by seagrasses interacts with grazing to shape an intertidal landscape

Area of Science:

• Ecology
• Marine Biology
• Ecosystem Dynamics

Background:

• Ecosystem engineering and consumer-resource interactions shape ecosystem spatial patterns.
• The interactive effects of these mechanisms on spatial complexity remain understudied.

Purpose of the Study:

• Investigate the mechanisms creating a hummock-hollow mosaic on a Zostera noltii-dominated intertidal mudflat.
• Understand the interplay between seagrass ecosystem engineering and waterfowl grazing in driving landscape complexity.

Main Methods:

• Field measurements to observe environmental conditions and species interactions.
• Experimental manipulations to test causal relationships.
• Spatially explicit modeling to simulate landscape dynamics.

Main Results:

• Seagrass (Zostera noltii) localized sediment accretion contributed to hummock formation.
• Waterfowl grazing (brent geese, widgeon) selectively targeted vegetated hollows in autumn.
• Grazing disrupted seagrass growth and sediment accretion in hollows, maintaining patchiness.
• Hummocks, with year-round seagrass cover, were less susceptible to grazing due to waterfowl feeding strategies.

Conclusions:

• The interaction between seagrass ecosystem engineering and waterfowl grazing significantly increases spatial complexity.
• This study provides an example of how foundation species and consumers can co-create heterogeneous landscapes.