Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem (original) (raw)
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Modified habitats influence an invasive species via direct and indirect effects.
Addition of man-made structures alters abiotic and biotic characteristics of natural habitats, which can influence abundances of biota directly and/or indirectly, by altering the ecology of competitors or predators. Marine epibiota in modified habitats were used to test hypotheses to distinguish between direct and indirect processes. In Sydney Harbour, kelps on pier-pilings supported greater covers of bryozoans, particularly of the non-indigenous species Membranipora membranacea, than found on natural reefs. Pilings influenced these patterns and processes directly due to the provision of shade and indirectly by altering abundances of sea-urchins which, in turn, affected covers of bryozoans. Indirect effects were more important than direct effects. This indicates that artificial structures affect organisms living on secondary substrata in complex ways, altering the biodiversity and indirectly affecting abundances of epibiota. Understanding how these components of habitats affect ecological processes is necessary to allow sensible prediction of the effects of modifying habitats on the ecology of organisms.
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By changing ecosystem processes and altering the physical landscape, invasive ecosystem engineers can have substantial impacts on ecosystem functions and human economies and may facilitate other non‐native species. Eradication programs in terrestrial and aquatic systems aim to reverse the impacts of invasive species and return the system to its pre‐invasion conditions. Despite an extensive focus on the impacts of both native and non‐native ecosystem engineers, the consequences of removing invasive ecosystem engineers, particularly in coastal ecosystems, are largely unknown. In this study, we quantified changes in a benthic community following the eradication of the invasive ecosystem engineer, hybrid cordgrass Spartina, in San Francisco Bay, California. We used field experimental manipulations to test for persistent effects of both aboveground and belowground structural modifications of the invasive plant on the benthic community. We found significant effects of the invasive plant m...
Impacts of Invasive Plants on Community and Ecosystem Properties
Invasive indigenous (IN) or nonindigenous (NI) plant species can alter various properties of plant communities, including species diversity, primary productivity, interactions between species, stability, and rates or pathways of successional recovery of a community following disturbance (Ramakrishnan and Vitousek 1989; Versfeld and van Wilgen 1986; Vitousek 1990; Vitousek and Walker 1989; Walker and Vitousek 1991). They can also alter the actual disturbance regime (Breytenbach 1986; Hughes et al. 1991; Vitousek 1990). Studies of ecosystem processes are usually not focused on a particular organism but on the linkages between organisms and their environment. Examination of the flow of energy, water, or nutrients through an ecosystem can provide a sensitive measure of the degree to which invasive plants alter indigenous ecosystems. Successful management of communities and ecosystems containing invasive species involves (1) assessing whether the invaders have significantly altered the e...