Effects of Invasive Seaweed Depend on Underlying Physical Habitat Structure

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Photo 1. A Green heron, Butorides virescens, forages on a mudflat covered with macroalgae. The dominant alga, Agarophyton vermiculophyllum, is visible as tufts of red-brown thalli and intermixed with Ulva spp., including Ulva lactuca. Photograph credit: Alice Besterman. Photo 2. Agarophyton vermiculophyllum forms mats up to 5 cm in depth above mudflat sediments, and generally between 2 and 3 cm deep. Here, a mat of Agarophyton has accumulated at the edge of a salt marsh, with some stems of Spartina alterniflora visible. The eastern mud snail, Tritia obsoleta (formerly Ilyanassa obsoleta), uses Agarophyton as refuge and substrate for egg-capsule deposition. Photograph credit: Alice Besterman. Photo 3. We used spotting scopes to observe shorebirds foraging across expansive mudflats exposed at low tide in the Virginia Coast Reserve LTER. We identified birds to the lowest taxonomic level, as well as the substrate they were used for foraging (bare mud, macroalgal mats, shallow water, oyster reefs, etc.). In this photograph, oyster (Crassostrea virginica) reef patches are visible in the foreground of the mudflat. Photograph credit: Alice Besterman. Photo 4. Hundreds of shorebirds including Limnodromus griseus (Short-billed dowitcher), Pluvialis squatarola (Black-bellied plover), and Calidris alpina (Dunlin) forage on a bare, topographically smooth mudflat in the Virginia Coast Reserve. Photograph credit: Alice Besterman. These photographs illustrate the article “Mudflat geomorphology determines invasive macroalgal effect on invertebrate prey and shorebird predators” by Alice F. Besterman and Michael L. Pace published in Ecology. https://doi.org/10.1002/ecy.3540.

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