Coastline Of South Africa Research Articles

Drivers of productivity on the Agulhas Bank and the importance for marine ecosystems

The Agulhas Bank, an area of broad continental shelf extending 250 km offshore of South Africa, sustains rich and productive fisheries. However, its primary production is driven by a complex mosaic of biophysical mechanisms, highly variable in time and space. The key drivers include a system of multiple costal upwellings, complex shelf currents and an interaction with the powerful Agulhas current. The patterns of spatial and temporal variability of primary production on the Agulhas Bank are critical for the spawning and survival of early life stages of many commercially important species exploited along the coastline of South Africa. In particular, the ‘chokka’ squid fishery is an important source of revenue for the Eastern Cape coastal region in South Africa, with low catch years causing socioeconomic hardship. After spawning on the Eastern Agulhas Bank, the squid paralarvae are thought to be transported west to the Central Agulhas Bank (CAB). This region is associated with a cool, productive, but rather intermittent, oceanic feature known as the ‘cold ridge’ (CR). If and when it occurs, this feature could provide a sufficient amount of concentrated (relative to the background values) food for the paralarvae to survive during its passive or near-passive stage. To date, a long-term analysis of CR variability and the mechanisms associated with this has not been conducted. Here, we used a high-resolution biogeochemical ocean model (NEMO-MEDUSA) to investigate the drivers of the productivity on the Agulhas Bank, specifically in the vicinity of the CR. Evidence of the CR is found from November to April and variability in its strength and spatial extent is comparable to that observed in remote sensing data. Interannual variability in productivity on the CAB is correlated to wind stress and zonal currents with the most productive events associated with anomalous easterly winds and enhanced westward flow on the Bank. These events coincide with the existence of an intense CR, important for overall productivity on the Bank, which may impact the recruitment of chokka squid and other fish species. From this simulation, we observe a season of low productivity in 2012 which may potentially relate to the infamous low catch in 2013 which caused economic hardship in the area.

How developed is the South African coast? Baseline extent of South Africa's coastal and estuarine infrastructure

Coastal ecosystems are increasingly being transformed from natural to artificial owing to increasing population growth, development pressures and impacts from climate change. With the threat from sea-level rise the increase in armouring of coastlines and other coastal defence structures is a particular concern. This study used Google Earth to define and map the extent of artificial structures along the coastline and within estuaries of South Africa. Infrastructure along the coastline was mostly concentrated around major cities with 85.71 km of armouring mapped along the entire coast and 51.74 km mapped within estuaries. Jetties were the dominant infrastructure type found within estuaries and armouring was the most dominant type along the coastline. Although large sections of the coast were found to be underdeveloped, hotspots around cities show that much of these areas are affected by infrastructure. In these areas in particular, haphazard and ad hoc development can have cumulative environmental impacts. As no extensive record of structures along the coastline of South Africa has been compiled, this study provides the first baseline inventory of the extent of infrastructure within the coastal environment of South Africa. This baseline can therefore be used to record and measure changes in infrastructure development of the coastal environment and guide future coastal development practises.

When cooling is worse than warming: investigations into the thermal tolerance of an endemic reef fish, Boopsoidea inornata

Recent investigations suggest that global warming is likely to alter temperature regimes along the southeastern coastline of South Africa through the increased frequency of upwelling events. Identifying thermal thresholds is fundamental in predicting the response of marine ectotherms to rapidly changing ocean temperatures. The aim of this study was to determine the thermal tolerance of the endemic sparid Boopsoidea inornata. To achieve this, 20 wild fish were captured from near Noordhoek in Gqeberha (Port Elizabeth). The fish were exposed to laboratory-simulated upwelling and heat-plume conditions until sublethal endpoints were identified to estimate the critical lower (CTmin) and critical upper (CTmax) thermal limits, respectively. During the simulated cooling or heating events, the opercular beat (OB) rates were recorded, their sublethal endpoints (loss of equilibrium) were identified, and their CTmin and CTmax were estimated. Breakpoint analyses of the OB rates identified the lower and upper thermal stress limits to occur at an average of 9 °C and 25 °C, respectively. The CTmin was estimated to be 7.8 °C and the CTmax 30 °C. When compared with in situ temperatures, these limits suggest that B. inornata is susceptible to small reductions in the minimum temperature. Given that the frequency and magnitude of upwelling events are expected to increase in response to global warming, this may have significant consequences for this and other sympatric, resident species.

The Digital Linguistics: The Birth of Linguistic Humans 66,000 Years Ago in South Africa with Laryngeal Descent

Modern humans are linguistic humans, who acquired the logical properties of phonemes and morae in speech sound to generate an infinite number of word signs and to compose grammatically modulated sentences with complex meanings. 5KA (thousand years ago) they invented characters, which could display individual knowledge and intelligence to be shared and passed on to the following generations. Civilization itself is the linguistic phenomenon where knowledge and thoughts are transferred to subsequent generations via written documents, and very rapid consecutive innovations take place. In the 21st century, we are at the third and final stage of logical linguistic evolution with the interactive search and electric transfer of information via computer networks. It is necessary to clarify the in-brain mechanism for linguistic processing and intelligence to take full advantage of the final stage. The author outlines on the general overview of Digital Linguistics (DL) and identifies the birth of linguistic humans at the time of the laryngeal descent, which provided vowel accented syllables containing logical properties of phonemes and morae, to 66KA on the southern coastline of South Africa at the beginning of Howiesons Poort industry.

Definition of baseline metal concentrations for assessing metal enrichment of sediment from the south-eastern Cape coastline of South Africa

Assessing metal contamination of sediment is complicated since metals are a ubiquitous, naturally occurring component of sediment, their concentrations in un-contaminated sediment can vary by orders of magnitude over relatively small spatial scales, and naturally occurring and anthropogenically introduced metals tend to accumulate in the same areas. To meaningfully interpret sediment metal data, factors affecting metal concentration variability in sediment must first be compensated for before naturally occurring and anthropogenically introduced concentrations can be differentiated. This can be accomplished through the procedure of geochemical normalisation. Baseline metal concentration models developed through this procedure can then be used to interpret metal concentrations measured in sediment from areas where anthropogenic metal inputs are suspected. In this study baseline metal concentrations in sediment from the coastal zone between the Kromme River estuary in St Francis Bay and the Nahoon River estuary in East London on the south-eastern Cape coastline of South Africa are defined, for the purpose of differentiating between natural and anthropogenically introduced metal concentrations in sediment from this region. Baseline concentration models were initially defined for three sub-regions of the coastline, and then for the region as a whole. Aluminium and iron were found to be suitable for normalising the concentrations of copper, cobalt, chromium, manganese, nickel, lead and zinc, but not concentrations of arsenic, cadmium and mercury. Baseline concentrations of arsenic, cadmium and mercury above which enrichment can be inferred were defined using cumulative probability and univariate plots. The manner in which the baseline models are used to interpret metal concentrations is demonstrated, using metal concentrations measured in sediment from the Port of East London. The baseline models are used to assess the suitability of sediment quality guidelines (SQGs) developed by the Department of Environmental Affairs and Tourism (DEAT) for assessing the quality of sediment from the coastal zone of South Africa. The Special Care Level Guideline for chromium is unsuitable for assessing the quality of sediment from the South-eastern Cape coastline since the guideline for this metal specifies a concentration that is below the baseline concentration in sediment from this region.

Modelling the accumulation and transport of floating marine micro-plastics around South Africa

Plastic pollution of South Africa's marine environment is widespread, yet limited research exists on the distribution, accumulation and transport of plastic debris around South Africa. In this paper, numerical modelling is used to provide a first approximation of the pathways and accumulation of marine micro-plastics around South Africa. To account for a range of plastic classes, particles with two different densities are considered. Low-density (LD) particles represent low- and high-density polyethylene while high-density (HD) particles are representative of Polyethylene terephthalate and Polyvinyl chloride. While the majority of micro-plastic particles that enter the ocean from the five major coastal urban-industrialised centers beach along the coastline of South Africa, a third is exported to the open ocean. LD and HD particles are primarily exported to the South Atlantic and South Indian Ocean, respectively. Particles that beach along South Africa's coastline tend to accumulate in close proximity to the coastal urban-industrialised centers.

Seabird breeding populantions decrease along the arid coastline of South Africa’s Northern Cape province

Numbers of eight seabird species that have bred in coastal areas of South Africa’s arid Northern Cape province have all shown substantial decreases since initial estimates of their abundance were made in the latter part of the twentieth century. Likely drivers of these decreases include reduced availability of food and the loss of suitable breeding habitat, including in the Orange River Estuary and at coastal pans and islands, which has resulted from a variety of human alterations, uses and disturbances. The decreases have contributed to a worsening conservation status of several of the seabirds, some of which are endemic to southern Africa. The more adaptable species appear to have partially offset habitat loss by moving to alternative breeding sites. However, substitute habitat is limited and the more numerous species suffered relatively large decreases. In order to conserve remnant populations it will be necessary to prevent further loss of breeding habitat, restore some former habitats and provide suitable, alternative habitat.

Changes in recreational shore anglers’ attitudes towards, and awareness of, linefish management along the KwaZulu-Natal coast, South Africa

Management of recreational fisheries cannot be based on biological and stock assessment data alone but needs to include appropriate social aspects (including knowledge, attitudes and behaviour) of anglers within the fishery. The primary purpose of this study was to evaluate and complement existing recreational fisheries research, through the analysis of demographic and psychographic angler attributes collected from two independent, shore-based snapshot monitoring surveys conducted on the KwaZulu-Natal (KZN) coastline of South Africa, in 1994–1996 and 2009–2010. Results show significant changes between the two survey events in the demographics of anglers (including ethnic composition, age distribution, years of fishing experience and employment status) participating in the KZN shore-based linefishery. Traditional management regulations (minimum size limits, daily bag limits and closed seasons), though appearing to have support, have had limited effectiveness, based on the increased levels of admitted non-compliance and poor knowledge of regulations for target species. Anglers in both surveys believed that catches had declined over the years, with overfishing being the most common reason given. The results are discussed in the context of changing management practices in the KZN recreational shore-based linefishery. The implications of changes in fisheries management policies and responsibilities along the KZN coast are highlighted.

Resource partitioning among South African delphinids

In order to better understand trophic relationships among four species of coastal delphinids, we compared isotopic composition of skin to attempt to assess potential inter- and intra-specific resource partitioning. Skin samples were collected from Indo-Pacific bottlenose dolphins (Tursiops aduncus) (n=132), long-beaked common dolphins (Delphinus capensis) (n=78), humpback dolphins (Sousa chinensis) (n=27), and striped dolphins (Stenella coeruleoalba) (n=3) along the coastline of South Africa. While the latter species tends to be found offshore, the other species have overlapping distributions and feed on similar prey, carbon (δ13C) and nitrogen (δ15N) isotope analyses revealed resource partitioning with differences in diet and habitat use. Striped dolphin δ13C values (−16.97±0.25‰, SD) were consistent with evidence that they typically forage offshore, while δ13C values of humpback dolphins reflected their use of inshore habitats (−15.16±0.65‰). Common and bottlenose dolphins had δ13C (−15.48±0.66‰ and −15.76±0.71‰ respectively) values that fell between these two extremes. Mean values for δ15N ranged from 11.92±0.20‰ for striped dolphins to 15.19±0.73‰ for humpback dolphins, suggesting either that these species were feeding at different trophic levels or that they were feeding in different trophic systems. Common and bottlenose dolphins had δ15N values of 13.49±0.50‰ and 14.40±0.74‰ respectively. Male bottlenose dolphins were significantly more enriched in δ15N compared to females suggesting dietary differences. No sex related differences were found in other species. Isotopic niche width determinations using corrected standard elliptical area (SEAc) were calculated. Humpback and bottlenose dolphins had the largest SEAc reflecting a broader trophic niche, while striped dolphins had the smallest SEAc reflecting a more specialized niche. Overall, these sympatric species appear to reduce potential competitive pressure through a combination of differing prey selection and habitat utilization.

Multi-proxy palaeosol evidence for late Quaternary (MIS 4) environmental and climate shifts on the coasts of South Africa

Palaeosols are common along the coastline of southern South Africa as stacked aeolian dune deposits but have rarely been studied. We selected two late Quaternary palaeosols exposed in a marine cliff-face at Koeberg and coastal barrier dune at Goukamma, South Africa in order to improve our understanding of their pedogenesis and palaeoclimate dynamics. Palaeosol-based proxies explored include: elemental geochemistry by X-ray fluorescence spectrophotometry, δ13C and δ18O isotopes, micromorphology and clay mineralogy by x-ray diffraction. Selected physico-chemical soil properties were analyzed by routine laboratory procedures. The palaeosols comprise predominantly loamy sand to sandy clay loam textures, have a high pH (>6.5), and very low electrical conductivity (<0.89 mS cm−1). SiO2 and CaO are the most abundant of all the elements in the cambic and calcic horizons respectively. The low levels of Al in the parent materials most likely invalidated the applicability of chemical weathering indices (CIA) to assess weathering intensity. In the case of chemical index of weathering (CIW), the age and sedimentary settings of the palaeosols overruled the possibility for K metasomatism and illitization by metamorphism. The indices WI-1 and W1-2 developed by Darmody et al. (2005) appear more consistent with depth. The palaeo MAT computed from palaeosol carbonate oxygen isotope is 14 and 11 °C for Koeberg and Goukamma respectively, while the maximum MAP obtained from the cambic horizon (Bw) of the Goukamma coastal barrier is 653 mm y−1. The layering seen in the thin section of the calcic layer at Goukamma indicates deposition, possibly by sedimentary differentiation across a palaeo-slope. Clastic calcite and muscovite mica are the dominant minerals in these palaeosols indicating impeded chemical weathering. Similar to many other parts of the world, the coastlines of South Africa has experienced environmental and climate oscillations in the Quaternary. We conclude that along the southern South Africa coasts, a palaeosol based approach to palaeoenvironmental and palaeoclimate reconstruction in combination with other proxies such as pollen and marine based isotopes can provide insights into the environmental oscillations of the late Quaternary.

Late Quaternary palaeoenvironments of the southern Cape coastline of South Africa: a multi-proxy record from Rietvlei, Still Bay

Late Quaternary palaeoenvironments of the southern Cape coastline of South Africa: a multi-proxy record from Rietvlei, Still Bay

Aspects of population dynamics and feeding by piscivorous birds in the intermittently open Riet River estuary, Eastern Cape, South Africa

Aspects of the population dynamics and feeding activity of piscivorous birds in the small (c. 5 ha) intermittently open Riet River estuary, on the south-eastern coastline of South Africa, were investigated monthly from August 2005 to July 2006. A total of 188 birds of 13 species were recorded, of which six were wading piscivores, four aerial divers and three were pursuit swimmers. The Reed Cormorant (Phalacrocorax africanus) was the numerically dominant species, with a mean of 8.25 (SD ± 7.90) individuals per count. Mean numbers of the Pied Kingfisher (Ceryle rudis) and Giant Kingfisher (Megaceryle maximus) were 3.42 (SD ± 1.20) and 1.17 (SD ± 0.60) individuals per count, respectively. The remaining 10 species revealed mean values <0.5 individuals per count. Breaching events were associated with a change in feeding groups from waders to pursuit feeders, and a decrease in total bird numbers, most likely due to loss of potential littoral zone foraging habitat for waders resulting from reduced water levels. The highest bird numbers were recorded in winter reflecting the migration of large numbers of Reed Cormorant into the system. Monthly food consumption by all piscivorous birds showed large temporal variability, ranging from 26.35 to 140.58 kg per month.

The search for indigenous dune stabilizers: Germination requirements of selected South African species

The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the demand of stabilization of drift sand will increase. The non-invasive alien grass species Ammophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized and indigenous sand-binding species would be preferred. The ger- mination requirements of the native Arctotheca populifolia, Ipomoea pes-caprae, Myrica cordifolia and Scaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments broke the dormancy of I. pes-caprae, M. cordifolia and S. plumieri, whereas the seeds of A. populifolia were not dormant. Seeds of I. pes-caprae and M. cordifolia had induced an innate dormancy, respectively, whereas the type of dor- mancy in seeds of S. plumieri dormancy processes remained unknown.

Dilution studies on three marine outfalls in South Africa

Field dilution studies were conducted on three “deep” water marine outfalls located along the South African coast to establish the comparibility of actual achievable initial dilutions against the theoretical predicted values and, where appropriate, to make recommendations regarding the applicability of the different prediction techniques in the design of future outfalls. The physical processes along the 3000 km long coastline of South Africa are diverse, ranging from dynamic sub-tropical waters on the east coast to cold, stratified stagnant conditions on the west coast. Fourteen existing offshore marine outfalls serve medium to large industries and various local authorities (domestic effluent). For this investigation three outfalls were selected to represent the range of outfall types as well as the diversity of the physical conditions of the South African coastline. The predicted dilutions, using various approaches, compared well with the measured dilutions. It was found that the application of more “simple” prediction techniques (using average current velocities and ambient densities) may be more practical, ensuring a conservative approach, in pre-feasibility studies, compared to the more detailed prediction models, which uses accurate field data (stratification and current profiles), when extensive field data is not readily available.

Dilution studies on three marine outfalls in South Africa

Field dilution studies were conducted on three “deep” water marine outfalls located along the South African coast to establish the comparibility of actual achievable initial dilutions against the theoretical predicted values and, where appropriate, to make recommendations regarding the applicability of the different prediction techniques in the design of future outfalls.The physical processes along the 3000 km long coastline of South Africa are diverse, ranging from dynamic sub-tropical waters on the east coast to cold, stratified stagnant conditions on the west coast. Fourteen existing offshore marine outfalls serve medium to large industries and various local authorities (domestic effluent). For this investigation three outfalls were selected to represent the range of outfall types as well as the diversity of the physical conditions of the South African coastline.The predicted dilutions, using various approaches, compared well with the measured dilutions. It was found that the application of more “simple” prediction techniques (using average current velocities and ambient densities) may be more practical, ensuring a conservative approach, in pre-feasibility studies, compared to the more detailed prediction models, which uses accurate field data (stratification and current profiles), when extensive field data is not readily available.

Braidplain deposition of the Upper Triassic Molteno Formation in the main Karoo (Gondwana) Basin, South Africa

ABSTRACT The Upper Triassic (Carnian?) Molteno Formation in the main Karoo (Gondwana) Basin, South Africa forms a northerly thinning, intracratonic clastic wedge comprising sandstones, shales and coals occurring within thick (up to 140 m) laterally persistent fining‐upward sequences. These sequences were deposited by braided streams draining an alluvial plain which may have been built on to the distal slopes of alluvial fan complexes of glacial outwash type. Geometric relations between sequences indicate three phases of tectonic activity. The lowermost fining‐upward sequence in the south accumulated against a rising mountain front; cessation of movement and an eastward shift in the main locus of tectonism and sedimentation was followed by renewed uplift and basinwide progradation of the second fining‐upward sequence adjacent to a fault‐block granite terrain located close to the present south‐east coastline of South Africa. This is believed to be the granite at the eastern end of the Falkland Island Plateau, an interpretation consistent with its position on most continental reconstructions and the fracture zone marking its northern scarp face. Faulting is attributed to the first phase of extension prior to continental breakup. The sourceward recession and lack of gross fining‐upward trends shown by the uppermost fining‐upward sequences is accounted for by limited back‐faulting of the still active basin margin. Cessation of activity and further basin margin recession occurred with deposition of the overlying floodplain deposits (Elliot Formation) which were distal equivalents of the braided alluvial plain.