Distribution of macrophyte species and habitats in South African estuaries

Adams, Janine B.; Veldkornet, D.A.; Tabot, Pascal Tabi

doi:10.1016/j.sajb.2016.08.001

Cited by 52 publications

(28 citation statements)

References 32 publications

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“…The uMhlathuze River to the west was canalised and diverted into the sanctuary and a new marine outlet created by dredging through the coastal berm 5 km south of the natural outlet (Weerts and Cyrus 2002). The new intertidal habitat and delta of the sanctuary was rapidly colonised by the white mangrove Avicennia marina and currently constitutes the largest mangrove habitat in South Africa (Bedin 2001;Adams et al 2016). Invertebrate estuarine communities have become species rich from increased marine exposure, but have lost endemic species, such as the burrowing ocypodid crab, Paratylodiplax blephariskios (MacKay and Cyrus 1998).…”

Section: Estuarine Lakesmentioning

confidence: 99%

An Estuary Ecosystem Classification that encompasses biogeography and a high diversity of types in support of protection and management

Niekerk

Adams

James

et al. 2020

African Journal of Aquatic Science

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For nearly three decades, the Whitfield (1992) characterisation scheme served as a reference framework to type South African estuaries. We outline a revised ecosystem classification scheme that incorporates biogeographical zonation and introduces new types. Coastal outlets were re-categorised as estuaries or micro-systems. For functional estuaries, the Estuarine Lakes, Estuarine Bays and Predominantly Open Estuary types were largely retained. New types are Estuarine Lagoons and Arid Predominantly Closed Estuaries. The numerically dominant, temporarily open/closed category was subdivided into Small and Large Temporarily Closed Estuaries, with a total habitat area of 15 ha, serving as threshold separating these two subdivisions. River mouths were renamed Fluvially Dominated Estuaries and divided into large and small size categories to reflect dissimilar catchment influences. Micro-systems were separated into micro-estuaries, micro-outlets, and waterfalls. South Africa's 290 estuaries were classified into 22 estuarine ecosystem categories arising from nine estuary types occurring across four biogeographical zones. In addition, 202 micro-systems were classified into nine ecosystem types, of which only the micro-estuaries (42) share possible functionality with estuaries. Estuaries subjected to functional shifts were also identified. The classification system provides a framework that integrates biogeography and the range of biophysical parameters evident in South Africa, and can be used for red listing of ecosystem types and determining estuarine sensitivity to pressures.

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Section: Estuarine Lakesmentioning

confidence: 99%

An Estuary Ecosystem Classification that encompasses biogeography and a high diversity of types in support of protection and management

Niekerk

Adams

James

et al. 2020

African Journal of Aquatic Science

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“…Habitat suitability for Z. capensis in the LGM In order to understand the influence of historical environmental conditions on the contemporary patterns of genomic variability, the suitable habitat for Z. capensis was hindcast to the Last Glacial Maximum (LGM; 21kya). Zostera capensis occurrence data was obtained from Adams et al (2016) and environmental data downloaded from MARSPEC at 5 arcminute resolution for both the present-day (Sbrocco et al 2018) and the LGM (CNRM-CM33 model;Braconnot et al 2007;Sbrocco 2014). Following Chefaoui et al (2017), only Sea Surface Temperature (SST) of the coldest month (Biogeo14) and warmest month (Biogeo15) were utilised to avoid using strongly correlated variables for Species Distribution Modelling (SDM; Guisan & Thuiller 2005;Braunisch et al 2013;Chefaoui et al 2017) and precipitation variables were excluded to decrease model uncertainty (Varela et al 2015).…”

Section: Genome-wide Variation and Differentiationmentioning

confidence: 99%

Shared genomic outliers across two divergent population clusters of a highly threatened seagrass

Phair

Toonen

Knapp

et al. 2019

Preprint

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The seagrass, Zostera capensis, occurs across a broad stretch of coastline and wide environmental gradients in estuaries and sheltered bays in southern and eastern Africa. Throughout its distribution, habitats are highly threatened and poorly protected, increasing the urgency of assessing the genomic variability of this keystone species. A pooled genomic approach was employed to obtain SNP data and examine neutral genomic variation and to identify potential outlier loci to assess differentiation across 12 populations across the ~9600km distribution of Z. capensis. Results indicate high clonality and low genomic diversity within meadows, which combined with poor protection throughout its range, increases the vulnerability of this seagrass to further declines or local extinction. Shared variation at outlier loci potentially indicates local adaptation to temperature and precipitation gradients, with Isolation-by-Environment significantly contributing towards shaping spatial variation in Z. capensis. Our results indicate the presence of two population clusters, broadly corresponding to populations on the west and east coasts, with the two lineages shaped only by frequency differences of outlier loci. Notably, ensemble modelling of suitable seagrass habitat provides evidence that the clusters are linked to historical climate refugia around the Last Glacial Maxi-mum. Our work suggests a complex evolutionary history of Z. capensis in southern and eastern Africa that will require more effective protection in order to safeguard this important ecosystem engineer into the future.

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“…Geomorphic constraints on propagule dispersal and availability of suitable habitat are significant controls on the distribution of mangrove, particularly between estuaries where estuary entrance closure and associated small tidal prism reduce the available habitat for mangrove establishment and growth (Roy et al 2001). Known regionally as intermittently closed or open lakes and lagoons, or ICOLLs, intermittent entrance closure of estuaries has been associated with restricted mangrove distribution in Australia, Brazil and South Africa (Haines et al 2006;Adams et al 2016;Saintilan et al 2016). In addition to reduced habitat availability in the absence of notable tides, dispersal of propagules through intermittent estuary entrances may be limited, periodic flushing of salts which is essential for mangrove survival is diminished, and/or soils become anoxic when water levels are elevated following catchment rainfall.…”

Section: Australiamentioning

confidence: 99%

Moving from Generalisations to Specificity about Mangrove –Saltmarsh Dynamics

Rogers

Krauss

2018

Wetlands

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Spatial and temporal variability in factors influencing mangrove establishment and survival affects the distribution of mangrove, particularly near their latitudinal limit, where mangrove expansion into saltmarsh is conspicuous. In this paper the spatial variability in mangrove distribution and variability in factors influencing mangrove establishment and survival during the Quaternary period are reviewed, focussing on research at latitudinal limits in Australia and mainland USA. Despite similarities in the response of mangrove to some drivers, the expression of these drivers is both spatially and temporally variable, demonstrating the need for analyses of mangrove-saltmarsh dynamics to move beyond generalisations and incorporate regional and local-scale specificity. We propose i) that precursory recognition that 'correlation does not mean causation' is inadequate and assumptions, caveats, and limitations should be clearly articulated in correlative studies; ii) experimental design in manipulative experiments must also articulate the spatial and temporal scale to which the analysis is relevant; and iii) analyses that draw from a range of methods will provide greater confidence. Integrated research programs that transect spatial and temporal scales and incorporate a range of techniques are essential to improve projections. Mangrove-saltmarsh distribution research should move beyond simple models that assume equilibrium between realised and fundamental niches.

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Distribution of macrophyte species and habitats in South African estuaries

Cited by 52 publications

References 32 publications

An Estuary Ecosystem Classification that encompasses biogeography and a high diversity of types in support of protection and management

An Estuary Ecosystem Classification that encompasses biogeography and a high diversity of types in support of protection and management

Shared genomic outliers across two divergent population clusters of a highly threatened seagrass

Moving from Generalisations to Specificity about Mangrove –Saltmarsh Dynamics

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