Brugia Malayi - Clark Science Center - Smith College

Effect of Habitat Structure Formed by Macroalgal Foundation Species on
Associated Fauna in Rocky Intertidal and Marsh-Cordgrass Ecosystems
Emily Peake
Habitat structure can have a profound impact on functions of an ecosystem. A study which looked at the two algal foundation
species in the marsh-cordgrass ecosystem found that the two work synergistically in how they provide a habitat for epifaunal
species in that ecosystem. 1 However, little is known about the difference in structural habitat provided by the macroalgae in the
rocky intertidal (Fucus versiculosus and Ascophyllum nodosum) and salt marsh areas (Fucus versiculosus ecad and Ascophyllum nodosum
ecad). Our summer research focused on two primary questions: 1) What is the difference in the structural habitat provided by
macroalgae in rocky intertidal areas and the morphologically distinct ecads of the salt marsh areas? 2) How does the difference in
the structural habitat affect snails (Littorina spp.) and crabs (Carcinas maenas)?
The primary methods used to quantify differences between rocky intertidal and marsh-cordgrass macroalgae included an
analysis of photographs oriented both vertically and horizontally to the algae mats at low tide. These photographs enabled us
to quantify the complexity of both species in each ecosystem by measuring surface convolution and the frequency and size of
interstitial spaces within the growing algae. Another method used was a series of predation trials; during which forty wire-mesh
cages containing algae, snails and crabs were deployed in the low salt marsh zone over a period of one week. This experiment
tested the ability of each algae to provide a refuge for snails from crab predation. A second experiment conducted during the
summer was a snail growth experiment, in which snails were placed in individual mesocosm containers in an environmental
chamber for up to five weeks. This experiment examined the preferred food sources for two snail species. We also conducted
species surveys at all sites in order to estimate the size and density of snails and crabs and the average biomass of algae in the
different areas. All experiments and fieldwork were conducted at the Wells Nation Estuarine Research Reserve in Wells, Maine (43
20’12.80” N, 70 32’28.43” W), at nearby Kennebunk Middle Beach in Kennebunk, Maine (43 23’04.31’’ N, 70 32’38.36” W) and
at Perkin’s Cove in Ogunquit, Maine (43 14’50.03” N, 70 36’25.68” W). Preliminary results showed ecads of the marsh-cordgrass
area being more complex in terms of interstitial space and surface convolution analyses than algae growing in the rocky intertidal
zones. (Supported by the Agnes Shedd Andreae 1932 Research Internship Fund)
Advisors: Joanne Benkley and Jennifer Dijkstra, PhD National Oceanic and
Atmospheric Administration (NOAA), National Estuarine Research Reserve,
Wells, ME
References:
1
Dijkstra, J.A. et al. 2011. Species-specific mediation of temperature and community interactions by multiple foundation species. Oikos 121: 646-654.
2012
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