Contracting range suitability for the southern African seagrass Zostera capensis

Dr Nikki Phair1, Professor Sophie von der Heyden1

1Stellenbosch University, Stellenbosch, South Africa


Coastal systems are under threat worldwide from climate and anthropogenic pressures. Seagrasses are a poorly studied yet vital component of these systems, serving as spawning grounds and nurseries for ecologically and commercially important species. This study aimed to assess the vulnerability of Zostera capensis to projected environmental conditions in South Africa. Currently, the species has a geographic range limited at its poleward reaches by the termination of the continental shelf. To assess the current and potential future distribution of suitable habitat for this species, an ensemble modelling approach was implemented through Biomod2 using sea surface temperature of the warmest and coldest months. Zostera capensis is projected to lose significant areas near current equatorward range limits in response to projected conditions, placing the species at increased risk of poleward contraction into a diminishing range of only a few estuaries. An area along the south-eastern coast could thus serve as a focus for targeted conservation management. Overall, our study concurs with projections made for other seagrasses globally and also raises concerns about future declines in extent and quality of seagrass habitat, particularly the negative effects on coastal biodiversity, commercially important populations with seagrass-dependant juvenile stages and trophic transfers to adjacent marine ecosystems. We recommend that marine spatial and biodiversity management planning be guided by assessing the on-going status of this species through monitoring, while also targeting its protection in southerly sites to optimize future resilience.


Nikki Phair recently completed her PhD at Stellenbosch University, where she used a genomic approach to assess the vulnerability and resilience of the southern African seagrass, Zostera capensis. She has a keen interest in conservation genomics, global change and biodiversity of coastal systems in general.

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