Experimental evidence for positive effects of invasive seaweed on native invertebrates via habitat-formation in a seagrass bed.

By M. Thomsen. 2010

87 citations recorded by the source corpus.

Relatively few studies have aimed to test if invasive species have positive effects on native species, for example via formation of habitat or by amelioration of environmental stress-conditions. The red macroalga Gracilaria vermiculophylla, from the West Pacific, is invading estuarine mudflat and seagrass habitats along East Pacific and East and West Atlantic coastlines. I tested if low (55-110 g WW m -2 ) and high (220-440 g WW m -2 ) densities of G. vermiculophylla have positive or negative effects on the macroinvertebrates (> 2 mm) that inhabit Zostera marina seagrass beds. The experiment was conducted over 34 days at both 0.5 and 2 m depth at Snaptun Harbor, Denmark. I found positive effects of Gracilaria on most invertebrates, with statistically significant results for “all invertebrates”, “gastropods”, and “bivalves”, and a near-significant result for “crustaceans”. Both quantitative and qualitative habitat-resource models may explain these positive effects; i.e. “more habitats” exist in the presence of Gracilaria and/or the “habitat differs” between Gracilaria and Zostera vegetation. Future studies should test these two general explanatory models and quantify (a) if density thresholds exists were effects shift from positive to negative, (b) specific mechanism whereby positive effects occur, (c) if Gracilaria provide a novel or substitute drift algal habitat, and (d) the largerscale ecosystem implications of this invasion.

Subfields: Ecology, Oceanography

View Paper: https://www.semanticscholar.org/paper/578643d30785e66fcf3d8195309296e0789bfba1

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In Oceanography

Citations in the corpus

Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem (2013, background): “australis have been demonstrated (Thomsen et al. 2012), so it is not surprising we found a similar relationship between C. taxifolia biomass and the number of B. australis recovered from cages. Being detritivores, B. australis may be exploiting enhanced detrital input of C. taxifolia into sediments.”
Impacts of an abundant introduced ecosystem engineer within mudflats of the southeastern US coast (2012, unknown): “4, 5, 6; see also Nyberg et al. 2009; Thomsen 2010; Thomsen et al. 2010).”
A framework to study the context-dependent impacts of marine invasions (2011, background): “…and Micheli, 2010), to most invasions (e.g., effects associated with the sex of the invader, although not all organisms have separate sexes, Walton et al., 2002), and to all invasions (e.g., the abundance, range and size of the invader, Parker et al., 1999; Griffen and Byers, 2009; Thomsen, 2010).”
Impacts of marine invaders on biodiversity depend on trophic position and functional similarity (2014, background): “M 0.30 1.0 Thomsen (2010) MP29–Gracilaria vermiculophylla– Shallow –0.276 High density only 1b Richness P–”