Ecosystem engineering by seagrasses interacts with grazing to shape an intertidal landscape.
Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model indicated that the mosaic resulted from localized sediment accretion by seagrass followed by selective waterfowl grazing. Hollows were bare in winter, but were rapidly colonized by seagrass during the growth season. Colonized hollows were heavily grazed by brent geese and widgeon in autumn, converting these patches to a bare state again and disrupting sediment accretion by seagrass. In contrast, hummocks were covered by seagrass throughout the year and were rarely grazed, most likely because the waterfowl were not able to employ their preferred but water requiring feeding strategy ('dabbling') here. Our study exemplifies that interactions between ecosystem engineering by a foundation species (seagrass) and consumption (waterfowl grazing) can increase spatial complexity at the landscape level.
Community and Conservation Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands. T.van.der.Heide@rug.nl
Tjisse
T
van der Heide
Johan S
JS
Eklöf
Egbert H
EH
van Nes
Els M
EM
van der Zee
Serena
S
Donadi
Ellen J
EJ
Weerman
Han
H
Olff
Britas Klemens
BK
Eriksson
D000818:Animals; D018533:Biomass; D003198:Computer Simulation; D003247:Conservation of Natural Resources; D004463:Ecology; D017753:Ecosystem; D004738:Engineering / Q000379:methods; D005777:Geese / Q000502:physiology*; D019015:Geologic Sediments; D015233:Models, Statistical; D008962:Models, Theoretical; D009792:Oceans and Seas; D012621:Seasons; D013997:Time Factors; D035962:Zosteraceae / Q000502:physiology*