Harmful algae are not harmful to everyone

Thomsen, Mads S.; Bettignies, Thibaut de; Wernberg, Thomas; Holmer, Marianne; Debeuf, Bastien

doi:10.1016/j.hal.2012.01.005

Cited by 27 publications

(19 citation statements)

References 47 publications

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“…Positive relationships between macrophyte density and the number of B. australis have been demonstrated (Th omsen 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.…”

Section: Sublethal and Lethal Effects Of C Taxifolia Density On Indisupporting

confidence: 81%

Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem

Gribben

Byers

Wright

et al. 2012

Oikos

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Habitat‐forming invasive species have complex impacts on native communities. Positive above ground and negative below ground impacts are reported, suggesting that habitat‐forming invasive species may affect community components differently. Furthermore, such effects may vary depending on the density of the invader. We determined the responses of community components to different densities of the invasive green alga Caulerpa taxifolia in southeastern Australia. Initially we investigated differences in soft‐sediment faunal communities (above and below ground) across a biomass gradient at two invaded sites. Caulerpa taxifolia biomass was positively associated with the composition and abundance of the epifaunal community, but negatively correlated with the abundance of infauna. To examine the response of common community members in more detail, we caged two species of mollusk (the infaunal bivalve, Anadara trapezia and the epifaunal gastropod, Batillaria australis) across the same biomass gradient to determine lethal and sublethal effects of C. taxifolia biomass on individuals. Survivorship of A. trapezia was low when C. taxifolia was above 300 g m−2. Negative sublethal effects were also density‐dependent with A. trapezia tissue weight being lowest above this same C. taxifolia biomass. The proportion of B. australis surviving was unaffected by C. taxifolia biomass. However, the total number of live B. australis recovered in cages increased as C. taxifolia biomass increased, providing further evidence of positive density dependent effects (in line with the survey data) of C. taxifolia on epifauna. Finally, we removed C. taxifolia from plots of differing C. taxifolia biomass and followed community change for 5 months. Community change following C. taxifolia removal was also density dependent as recovery 5 months post‐removal depended on the initial biomass of C. taxifolia, suggesting a lag in the recovery of communities due to residual environmental effects post‐removal (i.e. hysteresis). We have shown that the effects of a habitat‐forming invasive species are biomass dependent and also affect community components differently, suggesting that, globally, the impact of these types of invaders may be context dependent.

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Section: Sublethal and Lethal Effects Of C Taxifolia Density On Indisupporting

confidence: 81%

Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem

Gribben

Byers

Wright

et al. 2012

Oikos

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“…3). We have also shown that even at extremely high B. australis densities, all three snail species co-occur (Thomsen et al 2012). Furthermore, given that only few organisms are found attached to N. pauperatus (Fig.…”

Section: Discussionsupporting

confidence: 57%

“…We also suggest that this process extends beyond the facilitated sessile organisms, as these sessile organisms themselves are 'secondary habitat-formers/modifiers' that, like the 'primary habitat-formers/modifiers' (the shell-forming invader), provide living space, predation refugium, and food resources to mobile invertebrate 'end-users', including polychaetes, crustaceans, and small gastropods (Thomsen et al 2010a). This 'habitat cascades' process (Thomsen et al 2010a) is particularly important for B. australis with attached G. comosa, because this seaweed can grow into large fronds that dominate the habitat structures on unvegetated sand-flats and thereby facilitate communities of mobile invertebrates (Thomsen et al 2010a;Thomsen et al 2012). Finally, we suggest that invasion ecologists should investigate the prevalence and context whereby large-scale community-wide facilitation occurs (is this process rare in nature or has research been biased?)…”

Section: Discussionmentioning

confidence: 99%

Large-scale facilitation of a sessile community by an invasive habitat-forming snail

2013

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We provide an example of extensive facilitation of a sessile community throughout an invaded estuary by the invasive snail Batillaria australis. We show that B. australis greatly increases a limiting resource (attachment space) to a community of sessile organisms and estimate that a large part of the invaded estuary now contain ca. 50 times more sessile individuals associated with the invader than all native snails combined. We argue that native snails are unlikely to have been dramatically reduced by the invader, and we therefore suggest that the shell-attached sessile community, as a functional group, has benefitted significantly from this invasion. These results expand the current understanding of how invaded marine systems respond to habitat-forming invaders.

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“…Most of these studies, however, were not evaluated in an explicit habitatcascade context. Furthermore, we found that facilitation was strongly density-dependent, as shown for secondary habitat formers associated with trees (Ellwood and Foster 2004), seagrass (Thomsen 2010;Thomsen et al 2012), mangroves (Bishop et al 2012) and sessile invertebrates (Byers et al 2012;Thomsen et al 2013). Interestingly, density effects were stronger for Notheia than its host, which otherwise has been shown to be a direct driver of diversity patterns (Lilley and Schiel 2006;Schiel 2006;Bellgrove et al 2010), even though biomass was one order of magnitude larger for the latter.…”

Section: Distribution Of Clientsmentioning

confidence: 63%

A host-specific habitat former controls biodiversity across ecological transitions in a rocky intertidal facilitation cascade

Thomsen

Metcalfe

South

et al. 2016

Mar. Freshwater Res.

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Few studies have quantified facilitation cascades from rocky intertidal systems, across ecological transition zones, or where the secondary facilitator is an obligate epiphyte. Here, we address these research gaps. We first quantified distributions of the seaweed host Hormosira banksii and its obligate epiphyte Notheia anomala at different tidal elevations in summer and winter at Kaikoura, New Zealand. This analysis showed that the host and the epiphyte were, in both seasons, most abundant at ‘high’ and ‘low’ tidal elevations respectively, probably driven by contrasting responses to competitors and desiccation. We subsequently quantified richness and abundances of mobile invertebrates associated with Hormosira and various levels of epiphytic Notheia. Hormosira fronds were collected from different elevations, seasons, diurnal cycles, with different neighbouring algae and following an epiphyte-removal experiment. All tests showed positive density-dependent effects of Notheia-epiphytism on richness and abundances of invertebrates, with strongest facilitation occurring at the transition from intertidal to subtidal habitats. Our results support a growing number of facilitation cascade studies from different ecosystems and habitats, and suggest that habitat formation–driven facilitation cascades may be particularly common in marine benthic systems where epibiosis can be a dominant life form.

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Harmful algae are not harmful to everyone

Cited by 27 publications

References 47 publications

Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem

Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem

Large-scale facilitation of a sessile community by an invasive habitat-forming snail

A host-specific habitat former controls biodiversity across ecological transitions in a rocky intertidal facilitation cascade

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