Facilitation of molluscan assemblages in mangroves by the fucalean alga Hormosira banksii

Bishop, Melanie J.; Morgan, T. H.; Coleman, Melinda A.; Kelaher, Brendan P.; Hardstaff, Lyndle K.; Evenden, Robert W.

doi:10.3354/meps08247

Cited by 31 publications

(31 citation statements)

References 34 publications

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“…The H. banksii used for experimental manipulations was from the surrounding mangrove forest and was defaunated by hand prior to reintroduction to plots at appropriate experimental biomasses. To ensure that H. banksii was retained at the experimental density, but that epifauna could still colonize, we erected a galvanized mesh fence around each plot with a 50-mm gap at the base (see Bishop et al 2009). The fences were 200 mm high and were constructed of 5-mm galvanized mesh held in place by three plastic stakes 450 mm long.…”

Section: Direct Effects Of Pneumatophore Density and Hormosira Banksimentioning

confidence: 99%

“…In southeastern Australia, the dominant species of mangrove, Avicennia marina, produces pneumatophores (aerial roots) that facilitate many species of mollusks and crustaceans by providing structure, shelter, trapping detrital material, and supporting growth of epiphytic algae (Beck 1998, Skilleter and Warren 2000, Ross 2006). Among the species facilitated by A. marina is the fucalean macroalga, Hormosira banksii (King 1981, King andWheeler 1985), which is itself an important foundation species (e.g., Bishop et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Density‐dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves

Bishop¹,

Byers²,

Marcek³

et al. 2012

Ecology

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Co-occurring foundation species can determine biological community structure via facilitation cascades. We examined the density dependencies of facilitation cascades, including how the density of a basal foundation species influences the density of secondary foundation species, and how the density of secondary foundation species influences community structure. The system in which we assessed density dependencies was a temperate mangrove forest in which pneumatophores trap the fucoid alga Hormosira banksii and provide substrate for the oyster, Saccostrea glomerata. The alga and oyster in turn determine benthic community structure. In the field, algal biomass was positively correlated with pneumatophore density. Oysters, by contrast, were highly over-dispersed and correlated with the presence/absence of pneumatophores. Epifaunal abundance and species richness were positively correlated with algal and oyster abundance, but their effects were independent. The positive effect of pneumatophore density on epifauna was primarily an indirect effect of trapping more algae. Pneumatophores did not directly influence invertebrate communities. Experiments revealed that, at very low pneumatophore densities, algal retention was insufficient to facilitate epifauna above that found on pneumatophores alone. At higher densities, however, increasing the density of pneumatophores increased algal retention, and the density and diversity of associated invertebrates. Shading by the mangrove canopy reduced algal biomass but did not modify the density-dependent nature of the cascade. Our results extend facilitation theory by showing that the density of both basal and secondary foundation species can be critical in triggering facilitation cascades. Our study also reveals that, where foundation species co-occur, multiple, independent cascades may arise from a single basal facilitator. These findings enhance our understanding of the role of density-dependent facilitation cascades in community assembly.

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Section: Direct Effects Of Pneumatophore Density and Hormosira Banksimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Density‐dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves

Bishop¹,

Byers²,

Marcek³

et al. 2012

Ecology

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“…The relative contribution of foundation species to ecosystem function may stem from their morphological structure which has been measured using a composite of species‐specific trait‐based metrics such as size, number of branches or size of air bladders (Bishop et al . ; Bishop, Fraser & Gribben ; Wright et al . ) and mathematical relationships of species complexity (e.g.…”

Section: Introductionmentioning

confidence: 99%

Invasive seaweeds transform habitat structure and increase biodiversity of associated species

et al. 2017

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Summary The visual landscape of marine and terrestrial systems is changing as a result of anthropogenic factors. Often these shifts involve introduced species that are morphologically dissimilar to native species, creating a unique biogenic structure and habitat for associated species within the landscape. While community‐level changes as a result of introduced species have been documented in both terrestrial and marine systems, it is still unclear how long‐term shifts in species composition will affect habitat complexity or its potential to influence the biodiversity of species that occur at the base of the food web. We analysed quadrat photos collected at several subtidal sites in the Gulf of Maine over a 30+ year period, and collected individual seaweed species to determine their complexity and the biodiversity of meso‐invertebrates associated with each species. By coupling the relationship of 30+ years of shifts in seaweed assemblages, morphological structure of the seaweed assemblage, and their meso‐invertebrates, we determined introduced seaweeds have increased by up to 90%, corresponding to a rise in two‐dimensional (2D) structure, and a decline in canopy height of subtidal rocky habitats. The highly complex two‐dimensional habitat provided by introduced filamentous red seaweeds supports two to three times more meso‐invertebrate individuals and species that form the base of the food web than simpler forms of morphological habitat. Synthesis. The present study demonstrates a long‐term shift in foundation species towards a dominance of invasive seaweeds that directly reduce canopy height and increase the 2D biogenic structure of the habitat. These introduced seaweeds harbour greater biodiversity of species found at the base of the food web than seaweeds with simpler forms such as the native kelp species. Such shifts in habitat structure will propagate to food webs by influencing the structure of lower trophic‐level meso‐invertebrates and indirectly upper trophic‐level species that feed on these invertebrates and use the seaweed structure as refuge.

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“…The structure provided the pneumatophores traps free-living and reproductively capable H. banksii that washes into the mangrove forest following detachment from rocky shores (Plate 1, Appendix A; McKenzie and Bellgrove 2008). The alga, which is characterized by a distinctive thallus of branched chains of vesicles, in turn, supports dense and diverse communities of epifaunal mollusks (Plate 1, Appendix A; Bishop et al 2009Bishop et al , 2012. Experiments independently manipulating the density of pneumatophores and the biomass of algae in a crossed design have shown that this indirect effect of pneumatophores on epifauna, arising via the cascade, overwhelms their direct effects (Bishop et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…H. banksii vesicle diameter and length vary by as much as 20 mm, and thallus length by tens of centimeters (Womersley 1987, Ralph et al 1998, Macinnis-Ng et al 2005. The morphology of the alga directly influences epifaunal colonization (Bishop et al 2009), but it is unclear whether it also influences algal retention by pneumatophores.…”

Section: Introductionmentioning

confidence: 99%

Morphological traits and density of foundation species modulate a facilitation cascade in Australian mangroves

Bishop

Fraser

Gribben

2013

Ecology

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Facilitation cascades are critical to the maintenance of biodiversity in a variety of habitats. Through a series of two experiments, we examined how the morphological traits and density of interacting foundation species influence the establishment and persistence of a facilitation cascade in temperate Australian mangrove forests. In this system, mangrove pneumatophores trap the free-living alga, Hormosira banksii, which, in turn, supports dense and diverse assemblages of epifaunal mollusks. The first experiment, which manipulated pneumatophore height and density, revealed that these two traits each had additive negative effects on the establishment, but additive positive effects on the persistence of the cascade. High densities of tall pneumatophores initially served as a physical barrier to algal colonization of pneumatophore plots, but over the longer-term enhanced the retention of algae. The increased algal biomass, in turn, facilitating epifaunal colonization. The second experiment demonstrated that the retention of algae by pneumatophores was influenced more by algal thallus length than vesicle diameter, and this effect occurred independent of pneumatophore height. Our study has extended facilitation theory by showing that the morphological traits and density of basal and intermediary facilitators influence both the establishment and persistence of facilitation cascades. Hence, attempts to use foundation species as a tool for restoration will require an understanding not only of the interactions among these, but also of the key traits that modify interrelationships.

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Facilitation of molluscan assemblages in mangroves by the fucalean alga Hormosira banksii

Cited by 31 publications

References 34 publications

Density‐dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves

Density‐dependent facilitation cascades determine epifaunal community structure in temperate Australian mangroves

Invasive seaweeds transform habitat structure and increase biodiversity of associated species

Morphological traits and density of foundation species modulate a facilitation cascade in Australian mangroves

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