Browsing by Author "Malherbe, Hanlie"

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    Assessment of the alien marine intertidal invertebrates in the Kogelberg Biosphere Reserve, South Africa
    (Stellenbosch : Stellenbosch University, 2011-12) Malherbe, Hanlie; Samways, Michael J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: The privilege of utilising resources from the globe's marine ecosystems is threatened. Adequate regional and global conservation efforts are vital. Understanding species' distributions and the environmental variables influencing community structures are important for instigating optimum conservation plans. A major threat facing marine ecosystems is the introduction and proliferation of alien invasive species. The distribution and geographical expansion of marine alien invasive species, along with environmental variables driving their increase is also critical for drawing up conservation plans. In response to this point, this study addresses gaps in our knowledge regarding intertidal marine invertebrate species distributions particularly that of marine alien species in the Kogelberg Biosphere Reserve (KBR) and adjacent Betty's Bay Marine Protected Area (MPA) in the Western Cape of South Africa, a prime area for south-coast marine conservation. Species identifications were done in September 2010. Two marine alien invertebrate species were identified along the coastline. These were the invasive mytilid Mediterranean mussel Mytilus galloprovincialis and the bryozoan Watersipora subtorquata. A quantitative systematic survey of the intertidal region, consisting of seven rocky shore sites was then undertaken from October 2010 to December 2010. The abundance of all focal marine invertebrate species, within six selected habitat types was assessed. Environmental variables were also recorded. Statistical tests were done to investigate for significant interaction in mean abundance and mean species richness among intertidal zones and protection status (MPA and non-MPA), and among intertidal sampling units (SU‟s) and protection status. There was also investigated for significant difference in mean abundance and mean species richness across intertidal zones and habitat types where protection status was not taken into account, and to test for significant differences in mean abundance and mean species richness between the intertidal zones and habitat types. Correspondence analyses were used to illustrate relationships between species composition and the defined environmental variables. Tests were done to investigate for significant differences in mean abundance of the identified marine alien species between the MPA and non-MPA, study sites, SU's, and wave exposures. These results indicated that vertical and horizontal stress gradients along the shore mainly influence abundance and species richness. The significantly higher abundance of M. galloprovincialis outside the MPA is due to its preference for wave-exposed areas. The reason for the difference in the total abundance of W. subtorquata in the different habitats is not clear, although it appears that the higher abundance of this species in the MPA is because the sheltered nature of the MPA. M. galloprovincilais displaces indigenous species. W. subtorquata does not cause any significant harm along the coast of South Africa. This study indicates that the abundance of M. galloprovincialis and W. subtorquata in the MPA is relatively low. The MPA is therefore in good condition with regards to intertidal alien species. It is important that the MPA and adjacent KBR's coastline maintain its current pristine status.