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Marine alien and invasive species in South Africa Prof. Charles Griffiths Centre for Invasion Biology, Zoology Department, University of Cape Town [email protected] Balanus glandula ( white zone) and Mytilus galloprovincialis ( black zone) in Table Bay No species : Terrestrial Marine FW Total Mammal 13 - - 13 Bird 7 - 1 8 Reptile 1 - - 1 Fish - - 17 17 Ascidian - 9 - 9 Insect 394 3 3 400 Myriopod 9 - - 9 Arachnid 40 - 1 41 Crustacean 8 23 5 36 Annelid 39 9 - 48 Mollusc 32 12 8 52 Cnidarian - 13 1 14 other 7 11 4 Total 550 80 40 670 Overall Alien and Invasive Animals in SA Marine aliens: - The vectors of introduction Dry ballast Ship boring Ship fouling Ballast water Aquaculture Changing importance of vectors over time: Aquaculture Ship fouling Ballast water Ship boring Dry ballast 1700 1800 1900 2000 Recognition dates and arrival dates: (Mead et al. 2011a & b) (a) (b) Earliest DOC: pushed back 100 years Date of recognition as alien (left) dark = confirmed, light = cryptogenic -First paper listing aliens only 1992, rate of recognition since 2000 very rapid (>6 species per year since 2000 !) Backdating to earliest museum records (right panel) shows steady introduction rate since 1840, with recent acceleration, due to combination of local taxonomic work, higher introduction rate and recent directed searching (circled) Difficulties of identification of aliens: - Why have we been so slow to recognize these introductions? • Most likely sites of introduction (harbours, aquaculture facilities etc.) seldom surveyed. • Aliens misidentified as local species. • Aliens mistakenly considered to be “cosmopolitan” when in fact have been widely introduced. • Introduced species re-described as new ‘indigenous’ species. • Lack of taxonomic expertise in introduced taxa. Current composition of introduced marine biota (87 confirmed, 40 cryptogenic) Alien species Protoctista Dinoflagellata Porifera Cnidaria Polychaeta Cirripedia Copepoda Isopoda Amphipoda Decapoda Pycnogonida Insecta Gastropoda Bivalvia Brachiopoda Bryozoa Echinodermata Ascidiacea Pisces Rhodophyta Chlorophyta Angiospermae 5 10 Number of species Cryptogenic species 15 20 Distribution of introductions around coast – -mostly protected sites invaded - few species are widespread or abundant on open coast 14 Saldanha CapeTown Alexander Bay South Africa Durban 27 38 Richards Bay 12 Knysna 23 24 14 26 East London Port Elizabeth Where do the introductions come from? - All over, but most from Europe/N Atlantic North Atlantic North Pacific Europe Japan Caribbean Indo-Pacific Chile Australia Tristan da Cuhna Example of complexity of impacts: Mediterranean mussel, Mytilus galloprovincialis Region of origin: Europe Date of introduction: 1979 SA distribution: entire west coast, spreading along the south coast to East London 2004 W Namibia 1993 1986 L 1982 SB 1979 CT 1989 South Africa K 1995 D EL PE 2004 1990 Farm introduction 1979 Biomass Impact 1. Up-shore movement of centre of gravity of mussel beds High Mid Low Mytilus galloprovincialis 1988 Biomass Aulacomya ater High Mid Low Marcus Island (Hockey & Van Erkom Shurink 1992) Impact 2. Large increase in intertidal mussel biomass (especially on W. Coast) Species W Coast S Coast KZN Total wet t (%) Mytilus galloprovincialis 47 457 2 863 0 50 335 (44.2) Aulacomya ater 10 609 535 0 11 144 (9.8) 6 542 697 0 7 239 (6.4) - 31 787 13 400 45 187 (39.6) Choromytilus meridionalis Perna perna (Modified from Van Erkom Schurink & Griffiths 1990) Table Bay 1979 Table Bay 2004 Impact 3. Elevated biodiversity and faunal density in invaded areas ( esp. midshore zone) Species richness Infaunal density.m2 Before After Before After 1. (highest) Not invaded 3 2 4 000 5 000 2. Peak Mytilus zone 6 17 4 500 9 000 3. Mytilus invaded 1 13 < 1 000 6 000 4. Mytilus invaded 10 20 100 000* 17 000 5. Indigenous mussels displaced by Mytilus 24 8 90 000* 6 000 Intertidal zone (high to low) * Massive settlement of small gastropod Marcus Island (Robinson et al. 2007) Impact 4. Competition for primary rock space Two possible outcomes: 1. Co-exist with smaller Scutellastra granularis, as can live on mussel shells B=25 G=16 Frequency 0 % M. galloprovincialis B=36 G=23 Frequency Size class 50 % M. galloprovincialis B=33 G=21 Frequency Size class 100 % M. galloprovincialis Size class (Griffiths et al .1992) alternative outcome: 2. Displace larger Scutellastra argenvillei, as these cannot attain sexual maturity living on mussel shells (Steffani & Branch 2003) % Contribution to diet Impact 5. Increased food resources for Oystercatchers Mussels Other Limpets Oystercatcher density 1979 1979 1988 1990 (Hockey & Van Erkom Shurink 1992 and Hockey unpublished) Impact 6. Commercial culture & recreational harvesting 3000 tpa Mytilus cultured in Saldanha Bay, large intertidal stocks available for subsistence use Note: West coast rocky intertidal now totally alien dominated by 3 major species! Upper shore covered by Balanus glandula Midshore by Mytilus galloprovincialis Lowshore by Semimytilus algosus Acknowledgements: Thanks to NRF-DST Centre of Excellence for Invasion Biology for financial support