Print PageFoundation species can provide habitat that modify abiotic and biotic processes that contribute to ecosystem function. While many studies have focused on the processes and consequences of a focal foundation species, understanding the ecological equivalence of co-occurring foundation species is important to identify key species responsible for ecosystem function. Here, we investigated the relative contributions of salt marsh co-occurring foundation species on abiotic (temperature) and biotic responses of native and non-native species. In a series of experimental field studies, we manipulated foundation species to measure invertebrate recruitment, persistence, and predation. A laboratory experiment measured foundation species effects on herbivore growth.
Results/Conclusions
Overall, macroalgae provided habitat, food and cooler temperatures for dominant herbivores. Reduced sediment surface temperatures indicate that macroalgae alleviate environmental stress and provide a substrate that enhance species abundance in a manner that surpassed that of the primary foundation species (Spartina alterniflora). By relieving abiotic conditions, macralgae likely facilitated an expansion of littorinid snails realized niche that may surpass their fundamental niche. In all cases, facilitation by macroalgal species enables other species to persist across a broader range of physical conditions than would be possible in their absence. In addition to their different positive effects on temperature, the two intermediate algae foundation species act in different ways to enhance the abundance of the native and non-native littorinid snails. Fucus vesiculosus algae enhanced recruitment and growth of snails while the algal species, Ascophyllum nodosum provides refuge against predation and ameliorate thermal extremes. Therefore, the algal F. vesiculosus is important for early life-history stages, while A. nodosum algae is important later on as a refuge from consumers and high temperature.
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