Chapter 9
Coastal Invasions: The South African
Context
Tamara B. Robinson , Koebraa Peters , and Ben Brooker
Abstract In total, 95 marine alien species are known from the South African coast,
of which 56 have spread from their points of introduction to become invasive. While
just over half of these alien species are restricted to harbours, 45 invasive species
have been recorded in natural habitats. The association between marine alien species
and harbours reflects the importance of shipping as a pathway for introducing novel
marine biota. In the South African context, 91% of introductions have been linked to
this mode of transport, with the majority originating from the North Atlantic Ocean.
The most invaded region is the Southern Benguela ecoregion along the west coast,
where 67 alien species have been detected, with the number declining towards the
east. The drivers of this spatial pattern are not yet fully understood, although an
interaction between vector strength and compatibility of climate between recipient
and donor harbours is likely to play a role. Three species, the Mediterranean Mussel
Mytilus galloprovincialis, the Chilean Mussel Semimytilus algosus and the Pacific
Barnacle Balanus glandula, have become abundant and widespread along the open
coast, and are dominant on wave-exposed rocky shores along the west coast. Here,
their sequential invasions have altered intertidal community structure, predominantly through their high abundance and resultant alteration of habitat complexity.
Furthermore, the potential threat posed by alien biota to the effectiveness of marine
protected areas (MPAs) is increasingly being recognised. Baseline surveys of
19 South African MPAs have revealed the presence of 22 alien species from eight
phyla. The highest number of alien species (9) has been noted in Langebaan Lagoon
(along the west coast), while Sixteen Mile Beach and Helderberg MPAs (along the
west and south coasts, respectively) remain the only MPAs free of alien species.
Dedicated research effort in the last two decades has undoubtedly provided valuable
T. B. Robinson (*) · K. Peters
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
e-mail: trobins@sun.ac.za
B. Brooker
Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
© The Author(s) 2020
B. W. van Wilgen et al. (eds.), Biological Invasions in South Africa, Invading
Nature - Springer Series in Invasion Ecology 14,
https://doi.org/10.1007/978-3-030-32394-3_9
229
Coastal Invasions: The South African
Context
Tamara B. Robinson , Koebraa Peters , and Ben Brooker
Abstract In total, 95 marine alien species are known from the South African coast,
of which 56 have spread from their points of introduction to become invasive. While
just over half of these alien species are restricted to harbours, 45 invasive species
have been recorded in natural habitats. The association between marine alien species
and harbours reflects the importance of shipping as a pathway for introducing novel
marine biota. In the South African context, 91% of introductions have been linked to
this mode of transport, with the majority originating from the North Atlantic Ocean.
The most invaded region is the Southern Benguela ecoregion along the west coast,
where 67 alien species have been detected, with the number declining towards the
east. The drivers of this spatial pattern are not yet fully understood, although an
interaction between vector strength and compatibility of climate between recipient
and donor harbours is likely to play a role. Three species, the Mediterranean Mussel
Mytilus galloprovincialis, the Chilean Mussel Semimytilus algosus and the Pacific
Barnacle Balanus glandula, have become abundant and widespread along the open
coast, and are dominant on wave-exposed rocky shores along the west coast. Here,
their sequential invasions have altered intertidal community structure, predominantly through their high abundance and resultant alteration of habitat complexity.
Furthermore, the potential threat posed by alien biota to the effectiveness of marine
protected areas (MPAs) is increasingly being recognised. Baseline surveys of
19 South African MPAs have revealed the presence of 22 alien species from eight
phyla. The highest number of alien species (9) has been noted in Langebaan Lagoon
(along the west coast), while Sixteen Mile Beach and Helderberg MPAs (along the
west and south coasts, respectively) remain the only MPAs free of alien species.
Dedicated research effort in the last two decades has undoubtedly provided valuable
T. B. Robinson (*) · K. Peters
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University,
Stellenbosch, South Africa
e-mail: trobins@sun.ac.za
B. Brooker
Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa
© The Author(s) 2020
B. W. van Wilgen et al. (eds.), Biological Invasions in South Africa, Invading
Nature - Springer Series in Invasion Ecology 14,
https://doi.org/10.1007/978-3-030-32394-3_9
229