East Coast Of Southern Africa Research Articles

Bioaccumulation and trophic transfer of total mercury through the aquatic food webs of an African sub-tropical wetland system

Anthropogenic activities, including combustion of fossil fuels, coal, and gold mining, are significant sources of mercury (Hg) emissions into aquatic ecosystems. South Africa is a major contributor to global Hg emissions (46.4 tons Hg in 2018), with coal-fired power stations as the main source. Atmospheric transport of Hg emissions is the dominant cause of contamination, especially on the east coast of southern Africa where the Phongolo River Floodplain (PRF) is located. The PRF is the largest floodplain system in South Africa, with unique wetlands and high biodiversity, and provides essential ecosystem services to local communities who rely on fish as a protein source. We assessed the bioaccumulation of Hg in various biota, the trophic positions and food webs, as well as the biomagnification of Hg through the food webs in the PRF. Elevated Hg concentrations were found in sediments, macroinvertebrates and fish from the main rivers and associated floodplains in the PRF. Mercury biomagnification was observed through the food webs, with the apex predator tigerfish, Hydrocynus vittatus, having the highest Hg concentration. Our study shows that Hg in the PRF is bioavailable, accumulates in biota and biomagnifies in food webs.

Investigating the MIS2 Microlithic Assemblage of Umbeli Belli Rockshelter and Its Place Within the Chrono-cultural Sequence of the LSA Along the East Coast of Southern Africa

South Africa is arguably one of the most studied regions in Stone Age research. There are, however, considerable differences in research intensity with respect to different regions and time periods. While KwaZulu-Natal is an epicenter for Middle Stone Age (MSA) research, the Late Pleistocene LSA record is largely understudied in this region. Here we present a lithic assemblage from the site Umbeli Belli near Scottburgh dated to 17.8 ± 1.5ka BP. The lithic analysis of the GH 3 assemblages revealed both gradual and abrupt changes within this stratigraphic horizon, indicating relatively short-term changes in material cultural traditions. A comparison with other Robberg sites in the wider surroundings highlights the regional variability of the Robberg techno-complex and indicates potential directions for future research.

Movement behaviour of catface rockcod Mycteroperca (Epinephelus) andersoni (Epinephelidae) off the eastern seaboard of southern Africa

Movement behaviour of the endemic epinephelid Mycteroperca andersoni (formerly allocated to genus Epinephelus) along the east coast of southern Africa was investigated using both conventional dart tagging and passive acoustic telemetry. Results from both methods showed that this species is likely to be a temporary resident on shallow inshore reefs; fish showed high site fidelity and occupied relatively small home ranges for periods seldom exceeding 12 months, whereafter they appeared to undertake ranging-type movements. Adults >400 mm total length were more mobile than juveniles, and the distance moved increased with both fish size and time at liberty. Adults south of Durban, South Africa, moved farther in a northerly direction than those north of Durban, confirming that spawning likely takes place north of Durban. No direct evidence of a spawning migration was found, but anecdotal reports that they form spawning aggregations suggests that migrations for this purpose are likely to occur. The current species-specific linefish regulations and the recently expanded marine protected area network along the east coast of South Africa are believed to be adequate to ensure the future sustainable use of this species. However, improved enforcement of regulations is required, and identification of spawning aggregation sites should be a research priority.

Maputo Special Reserve and dung beetle conservation in the heterogeneous landscape of the Maputaland Centre of Endemism

Background: Maputo Special Reserve (MSR) in Mozambique lays within the Maputaland Centre of Endemism (MCE) and protects the biota of a habitat mosaic dominated by coastal dune forest and inland sand forest patches of different sizes surrounded by natural grassland. Objectives: To determine the importance of woody versus grassland vegetation for supporting endemic east coast versus widespread savanna dung beetles in the MCE in the face of increased accessibility and exploitation of woody vegetation in southern Mozambique, especially by charcoal burners.Method: We used general linear mixed models, additive partitioning of diversity and ordination to analyse species abundance and occurrence across a mosaic of three major habitats in the MSR (grassland, sand and dune forest).Results: High compositional heterogeneity was found between habitat types and study sites so that beta diversity was mostly higher than alpha diversity. Three distinct scarabaeine dung beetle assemblages defined from ordination were largely centred on the three habitat types. Out of a total of 61 species, greater numbers were associated with grassland (38) than sand (17) and dune forest (6) although abundance was greater in both dune forest and grassland than in sand forest. Biogeographical classification indicated that >40% of the species are endemic to the east coast of southern Africa with the remainder centred in adjacent savanna. Endemic east coast species were well represented in both forest (15) and grassland (11). Savanna species were better represented in grassland (27) than forest (8). Proportions of grassland species and their abundance declined across increasing patch sizes of sand forest becoming lowest in dune forest.Conclusions: Conservation of endemic, east coast dung beetle species requires the preservation of both natural grassland and sizeable patches of forest in an undisturbed habitat mosaic. As the east coastal system is relatively small in extent with the MCE widely transformed in South Africa, the MSR is an important contributor to regional conservation of endemic species.

The Provenance of Terrigenous Components in Marine Sediments Along the East Coast of Southern Africa

AbstractTerrestrial signals in marine sediment archives are often used for paleoclimatic reconstructions. It is therefore important to know the origin of the different terrestrial sedimentary components. The proximity to a river mouth is often the key location to determine the source. Especially in regions with strong ocean currents, such an assumption might, however, lead to considerable misinterpretations. To investigate the source of various terrigenous sediment fractions in southeastern Africa, a region with strong sediment redistribution, we have performed an extensive comparison between terrestrial material (pollen, plant lipids, detrital modes, and heavy minerals as well as bulk inorganic geochemical composition) from potential source regions and the same components in the adjacent coastal and continental shelf sediments. Onshore the proxy‐indicators reflect small‐scale diversity in sampling locations and associated environments (riverbank sediments, flood deposits, suspension loads, and soils). Nevertheless, the overall trends reflect significant environmental gradients along a SW to NE transect. We note a general comparability of the studied parameters between the continental and marine sediments regardless of their specific differences in transport and depositional characteristics. We propose that the influence of the Agulhas Current affects sediment deposition and distribution only seaward of the midshelf and that pockets of sediment remain preserved in the lee of coastal protrusions where they are protected from erosion. This study provides the essential prerequisite to allow the attribution of temporal variations of compositional changes in marine sediment cores to environmental changes in southeastern Africa.

Age and growth of narrow-barred Spanish mackerel Scomberomorus commerson in the coastal waters of southern Mozambique and KwaZulu-Natal, South Africa

The narrow-barred Spanish mackerel Scomberomorus commerson is one of the most important linefish species caught in KwaZulu-Natal and southern Mozambique waters, forming the basis of important commercial, artisanal and recreational fisheries. A total of 439 S. commerson were sampled along the east coast of southern Africa (KwaZulu-Natal, South Africa, and southern Mozambique) between April 2011 and March 2012. Retrospective length-at-age data observed from whole otoliths were used to compare and describe sex-specific growth. Growth rates obtained from otolith-derived data were compared with those estimated from 29 tag-recaptured fish. Overall, ages ranged from 0.48 to 14.6 years for females and 0.4 to 13.57 years for males. Otolith readings yielded an average percent error of 11.21%, lower than recorded in a previous study from the region. Marginal zone analysis provided strong evidence that one translucent and one opaque growth zone were laid down annually. Schnute growth-function parameters indicated significant differences in growth between sexes. Females approached their mean asymptotic length at a faster rate, and grew to a greater mean length-at-age, relative to males. Growth in both sexes was rapid, achieving 67.46 cm FL (females) and 65.4 cm FL (males) in their first year of life. Growth rates obtained from tag-recaptured S. commerson indicated slower growth for smaller/younger fish up until 70 cm FL after which growth was very similar to that observed from otolith-derived data. The results of this study provide accurate, validated life-history parameters for king mackerel that are important for the assessment of stock status in the region.

An aeolian sediment reconstruction of regional wind intensity and links to larger scale climate variability since the last deglaciation from the east coast of southern Africa

Few long-term environmental records are available for southern Africa where shifts in atmospheric circulation and changes in sea surface temperatures interact to influence regional climate dynamics. We present downcore grain size and inorganic geochemistry data covering the last ~23,000years from a peatland on the east coast of South Africa and examine links between shifts in regional wind activity and palaeoclimatic variability. Our record documents substantial variations in aeolian flux associated with changes in regional climate and wind patterns that reflect larger scale atmospheric circulation patterns. Substantially higher fluxes observed during the Last Glacial Maximum (LGM) are linked to widespread aridification and an expansion in local source areas brought about by a clear shift to dry and cool conditions. Variations in grain size distribution reveal that the aeolian record from Mfabeni comprises two dominant end-members; locally-derived coarse-grained material and a more fine-grained dust component. Marked changes in composition and modal grain size suggest that hydrological shifts in the region during the LGM were accompanied by an increase in storm frequency and wind strength that we link to a northward displacement in the westerly wind belt and a strengthening in wind intensity. Coupling between a rapid increase in sea surface temperature (SST) and an approximate three-fold decrease in aeolian activity after 15kcalyrBP suggests that changes in SST and its effect on the position and intensity of the westerlies in the Southern Ocean was the dominant climatic driver in the region during deglaciation. Substantially lower aeolian activities through the early Holocene indicate a warming in regional climate and the establishment of more humid conditions under the influence of enhanced tropical easterly flow. Our record also documents more subtle changes in climate over the mid to late Holocene and provides support for an arid phase in southern African climate 6–4kcalyrBP, as well as an increase in climate variability associated with a strengthening in El Niño–Southern Oscillation (ENSO) activity ~2kcalyrBP. The study contributes to current knowledge of atmospheric circulation patterns in the Southern Hemisphere and provides new insight into links between aeolian activity, regional wind patterns and climatic variability over glacial-interglacial timescales for a region where existing palaeoclimate records are scarce.

Camera-trap data elucidate habitat requirements and conservation threats to an endangered forest specialist, the Spotted Ground Thrush (Zoothera guttata)

The spotted ground thrush (Zoothera guttata; SGT) is a globally endangered forest specialist whose distribution is poorly understood in the critically endangered Indian Ocean Coastal Belt Forest (IOCBF) biome on the east coast of southern Africa. More than 70% of the IOCBF has been lost to development, resulting in fragmented forest remnants within a mosaic of different land uses. We conducted camera-trap surveys with 5796 trap-days in 82 forest patches of various sizes across a gradient of land-use types in the IOCBF during the winter seasons of 2014–2016 to establish occupancy (Ψ) of SGT. We used occupancy modelling and incorporated forest microhabitat characteristics and surrounding land-use classifications to compare sites and determine SGT distribution across the habitat mosaic. The top model estimated an average Ψ=0.39±0.09, and detection probability (P)=0.11±0.03. At the landscape scale, larger, less isolated patches had a higher Ψ of SGT while P decreased with proximity to cultivated land. At the microhabitat scale, a high percentage of bare ground influenced Ψ positively but P negatively, as did short grass cover. However, short herbaceous cover and high stem density of large (11–15m) trees influenced P positively. These results detail the influence of landscape-scale factors including forest fragmentation and conversion to agriculture in conjunction with forest microhabitat-scale characteristics, on patch selection and distribution of a cryptic, ground-dwelling species that is both threatened and under-studied. Given its endangered status and dependence on larger and more mature forest patches, SGT may be an effective flagship species for the conservation of threatened IOCBF patches.

Identifying the drivers of the pelagic ecosystem of an oligotrophic bight (KwaZulu–Natal, South Africa) using stable isotopes (δ13C, δ15N) and C : N ratio analysis

The international literature highlights the importance of understanding the role and fate of terrestrial organic matter (OM) in the marine system, yet little is known about this on the oligotrophic east coast of South Africa. Within the Bight, three important processes make OM biologically available: (1) a topographically induced upwelling cell (north), (2) a Cyclonic Eddy (south), and (3) riverine input. We hypothesise that: (i) these OM sources differ substantially in their isotope ratios, and (ii) zooplankton at the inshore region has an isotope signature linked to localised fluvial fluxes. Particulate OM samples were collected at five locations along the Bight and in three main estuaries during austral summer and winter seasons in 2010 and subjected to isotopic and mixing model analysis. Riverine input played an important role in this ecosystem inshore during the wet season. Only marine OM played a role as a biological driver offshore and at all sites during the dry season. Although there were indications that the upwelling cell did occur, it was not confirmed as active in either season. The current study provides valuable insights into the Bight's biological functioning and principle insights into the fate of terrestrial organic carbon on the east coast of southern Africa.

Extending periodic eddy covariance latent heat fluxes through tree sap-flow measurements to estimate long-term total evaporation in a peat swamp forest

Abstract. A combination of measurement and modelling was used to find a pragmatic solution to estimate the annual total evaporation from the rare and indigenous Nkazana Peat Swamp Forest (PSF) on the east coast of Southern Africa to improve the water balance estimates within the area. Actual total evaporation (ETa) was measured during three window periods (between 7 and 9 days each) using an eddy covariance (EC) system on a telescopic mast above the forest canopy. Sap flows of an understory tree and an emergent tree were measured using a low-maintenance heat pulse velocity system for an entire hydrological year (October 2009 to September 2010). An empirical model was derived, describing the relationship between ETa from the Nkazana PSF and sap-flow measurements. These overlapped during two of the window periods (R2 = 0.92 and 0.90), providing hourly estimates of ETa from the Nkazana PSF for a year, totalling 1125 mm (while rainfall was 650 mm). In building the empirical model, it was found that to include the understory tree sap flow provided no benefit to the model performance. In addition, the relationship between the emergent tree sap flow with ETa between the two field campaigns was consistent and could be represented by a single empirical model (R2 = 0.90; RMSE = 0.08 mm h−1). During the window periods of EC measurement, no single meteorological variable was found to describe the Nkazana PSF ETa satisfactorily. However, in terms of evaporation models, the hourly FAO Penman–Monteith reference evaporation (ETo) best described ETa during the August 2009 (R2 = 0.75), November 2009 (R2 = 0.85) and March 2010 (R2 = 0.76) field campaigns, compared to the Priestley–Taylor potential evaporation (ETp) model (R2 = 0.54, 0.74 and 0.62 during the respective field campaigns). From the extended record of ETa (derived in this study from sap flow) and ETo, a monthly crop factor (Kc) was derived for the Nkazana PSF, providing a method of estimating long-term swamp forest water-use from meteorological data. The monthly Kc indicated two distinct periods. From February to May, it was between 1.2 and 1.4 compared with June to January, when the crop factor was 0.8 to 1.0. The derived monthly Kc values were verified as accurate (to one significant digit) using historical data measured at the same site, also using EC, from a previous study. The measurements provided insights into the microclimate within a subtropical peat swamp forest and the contrasting sap flow of emergent and understory trees. They showed that expensive, high-maintenance equipment can be used during manageable window periods in conjunction with low-maintenance systems, dedicated to individual trees, to derive a model to estimate long-term ETa over remote heterogeneous forests. In addition, the contrast in annual ETa and rainfall emphasised the reliance of the Nkazana PSF on groundwater.

Review of Mothocya Costa, in Hope, 1851 (Crustacea: Isopoda: Cymothoidae) from southern Africa, with the description of a new species

Three species of Mothocya are reported from the east coast of southern Africa: Mothocya plagulophora (Haller, 1880) from Maputo, Mozambique, from the gills of Hemiramphus far (Forsskål, 1775); Mothocya renardi (Bleeker, 1857) from diverse localities in South Africa and Mozambique, from the hosts Strongylura leiura (Bleeker, 1850) and Tylosurus choram (Rüppell, 1837); and Mothocya affinis sp. nov. from Sodwana Bay, South Africa, from the gills of Hyporamphus affinis (Günther, 1866). Mothocya affinis sp. nov. is characterised by relatively small size (maximum 16 mm); large, wide coxae on pereonite 7 that overlap the pleon; uropods that do not extend past the pleotelson posterior margin; produced anterolateral margins on pereonite 1; and a twisted pleon and pleotelson. Mothocya katoi Nunomura, 1992 and Mothocya toyamaensis Nunomura, 1993 are both transferred to the genus Ceratothoa, with M. katoi being placed into junior synonymy with Ceratothoa guttata (Richardson, 1910). Irona ogcocephalus Avdeev & Avdeev, 1974 and I. callionymus Avdeev & Avdeev, 1974 are both transferred to Elthusa, and Irona trillesi Rokicki, 1986 is synonymised with Mothocya longicopa Bruce, 1986. A key to the south-western Indian Ocean species of Mothocya is given, and a table summarising recent and new nomenclatural acts in the genus is provided.

A model study of regional air‐sea interaction in the austral summer precipitation over southern Africa

AbstractThe importance of air‐sea interactions in the simulation of southern Africa precipitation is brought out using a fully coupled regional model and by forcing the atmospheric component of the coupled model with the coupled model‐simulated sea surface temperature (SST). The coupled model has the Advanced Research Weather Research and Forecasting model as the atmospheric component and the Regional Ocean Modeling System as the oceanic component. The spatial and temporal distribution of the coupled model‐simulated SST shows good agreement with observations. The coupled model shows a bias of about 0.25°C near the east coast of southern Africa. Comparison of the precipitation between the coupled and uncoupled model shows that the air‐sea interactions play an important role in the simulation of the precipitation during the peak precipitation season January to March, when the precipitation is mostly due to tropical processes. It is found that the two‐way specification of SST to the atmospheric model results in significant larger (smaller) precipitation depending on the spatial distribution of SST, due to the increase (decrease) of moisture from the surrounding oceans into the landmass. The results also show that the air‐sea interactions are not so important during the initial phases of the precipitation from October to December.

Residency patterns and migration dynamics of adult bull sharks (Carcharhinus leucas) on the east coast of southern Africa.

Bull sharks (Carcharhinus leucas) are globally distributed top predators that play an important ecological role within coastal marine communities. However, little is known about the spatial and temporal scales of their habitat use and associated ecological role. In this study, we employed passive acoustic telemetry to investigate the residency patterns and migration dynamics of 18 adult bull sharks (195–283 cm total length) tagged in southern Mozambique for a period of between 10 and 22 months. The majority of sharks (n = 16) exhibited temporally and spatially variable residency patterns interspersed with migration events. Ten individuals undertook coastal migrations that ranged between 433 and 709 km (mean = 533 km) with eight of these sharks returning to the study site. During migration, individuals exhibited rates of movement between 2 and 59 km.d−1 (mean = 17.58 km.d−1) and were recorded travelling annual distances of between 450 and 3760 km (mean = 1163 km). Migration towards lower latitudes primarily took place in austral spring and winter and there was a significant negative correlation between residency and mean monthly sea temperature at the study site. This suggested that seasonal change is the primary driver behind migration events but further investigation is required to assess how foraging and reproductive activity may influence residency patterns and migration. Results from this study highlight the need for further understanding of bull shark migration dynamics and suggest that effective conservation strategies for this vulnerable species necessitate the incorporation of congruent trans-boundary policies over large spatial scales.

Evidence for temperature limitation of nitrogen mineralisation in the Drakensberg Alpine Centre

We made use of pot experiments and soil mineralisation assays to test the effect of temperature on the soil nitrogen (N) economy of the Drakensberg Alpine Centre (‘mountain site’). The approach was enhanced by the inclusion of a contrasting warm, subtropical environment on the east coast of southern Africa (‘coast site’) which presented an opportunity to test plant growth in mountain soil outside of the mountain site's natural climatic envelope. This study was further augmented by two greenhouse experiments that helped isolate the factors responsible for the growth responses in the experiments above. Plant morphology, plant nutrients and soil nutrients were used as the basis for comparing treatment effects. The primary pot experiment showed that plant growth was uniform in the mountain site regardless of whether the test species was grown in intrinsically N-rich mountain soil or intrinsically N-poor coast soil. However, we noted significant growth differences at the coast site using the aforementioned soil nutrient regimes. In terms of the soil mineralisation assay, coast soil, derived from intrinsically N-poor sandstone, predictably mineralised little soil inorganic N at the mean spring temperature of 19°C. However against expectations, the intrinsically N-rich mountain soil mineralised <1% of its total soil N budget into inorganic N at 12°C, most probably because the microbes responsible for the conversion of organic soil N to inorganic soil N were severely inhibited at this mean spring temperature. However, the potential to mineralise far more N in mountain soil was apparent when using an elevated experimental temperature of 30°C, with 369% more soil N being available under the latter regime. Our results suggest that the cooler temperatures associated with high elevations in the mountain site constrain the activity of soil microbes in mountain soil, resulting in a functionally N-poor soil economy particularly deficient in inorganic N. This also explains the similar growth responses regardless of the soil being intrinsically N-rich or N-poor. We speculate whether or not more soil inorganic N may become available under a regime of warming due to accelerated N mineralisation, to the detriment of plant taxa adapted to low soil N availability.

Long-term decreases in persistent organic pollutants in South African coastal waters detected from beached polyethylene pellets

Polyethylene pellets provide a convenient means to monitor Persistent Organic Pollutants (POPs) in marine systems. Pellets collected between 1984 and 2008 at three South African beaches were analysed for PCB, HCH and DDT. Concentrations of all three POPs decreased over the last two decades, although this signal was less clear for PCBs, and further monitoring is needed to assess trends in this family of compounds. DDT concentrations at two sites were higher than previous records for southern Africa, but there is no evidence of a link to the ongoing use of DDT for malaria control. HCHs concentrations were lower than in pellets from the east coast of southern Africa, suggesting that this pesticide was mainly used in the eastern part of the region. Our study demonstrates the potential for International Pellet Watch to track temporal as well as geographical patterns in the abundance of POPs in marine environments.

Desenvolvimento de modelo agrometeorológico espectral para estimativa de rendimento do milho na Província de Manica-Moçambique

Moçambique é um país localizado ao longo da costa Leste da África Austral, com a economia baseada essencialmente na agricultura. A cultura do milho (Zea mays L.) é a mais importante, cultivada em regime de sequeiro, com rendimentos dependentes das condições meteorológicas. Este trabalho teve como objetivo o ajuste de um modelo agrometeorológico espectral, para estimativa de rendimentos do milho, na província de Manica. A área de estudo envolveu os distritos de Gondola, Manica, Mossurize e Sussundenga, responsáveis por mais de 80% da produção de milho na província de Manica, nos anos de 2000 a 2009. ETr e ETm e ISNA foram as variáveis agrometeorológicas testadas no ajuste, obtidas a partir de estimativas de elementos meteorológicos do modelo do ECMWF. As variáveis espectrais foram os índices EVI e NDVI, provenientes do produto MOD13Q1, e o índice LSWI, calculado utilizando-se as bandas de refletância contidas neste produto. O modelo agrometeorológico espectral, ajustado por meio de regressão linear múltipla, teve como variáveis independentes os índices meteorológicos e espectrais e, como variável dependente, o rendimento médio ou o rendimento relativo. O modelo regional, que incluiu os distritos de Gondola, Manica e Sussundenga, e considerou o rendimento relativo, foi o mais recomendado para estimativa de rendimentos do milho, na região, com r² = 0,762 e RMSE de 9,46%.

First record of the echiuran Anelassorhynchus porcellus Fisher, 1948 from the east coast of southern Africa (Echiura: Echiuridae)

The Pacific echiuran species Anelassorhynchus porcellus (Fisher, 1948) was collected from the intertidal rocky shores at Perriers Rock and Isipingo Beach on the KwaZulu-Natal coast. This is the first known record of this species from South African waters. Anelassorhynchus porcellus, originally described by Fisher (1948) from several specimens collected in tidal pools south of Honolulu Harbour, Hawaii was later recorded and described by Edmonds (1960) from specimens collected from Heron Island, Queensland. The discovery of this species from the east coast of southern Africa considerably extends its geographical range. After closer examination of additional specimens of Anelassorhynchus gangae Biseswar, 1984 collected from the Kwazulu-Natal coast it is proposed that this species be recognized as a junior synonym of A. porcellus. Anelassorhynchus porcellus is redescribed and some of the taxonomic characters are reviewed.

First Record of the EchiuranAnelassorhynchus porcellusFisher, 1948 from the East Coast of Southern Africa (Echiura: Echiuridae)

The Pacific echiuran species Anelassorhynchus porcellus (Fisher, 1948) was collected from the intertidal rocky shores at Perriers Rock and Isipingo Beach on the KwaZulu-Natal coast. This is the first known record of this species from South African waters. Anelassorhynchus porcellus, originally described by Fisher (1948) from several specimens collected in tidal pools south of Honolulu Harbour, Hawaii was later recorded and described by Edmonds (1960) from specimens collected from Heron Island, Queensland. The discovery of this species from the east coast of southern Africa considerably extends its geographical range. After closer examination of additional specimens of Anelassorhynchus gangae Biseswar, 1984 collected from the Kwazulu-Natal coast it is proposed that this species be recognized as a junior synonym of A. porcellus. Anelassorhynchus porcellus is redescribed and some of the taxonomic characters are reviewed.

Shoreline recovery from storms on the east coast of Southern Africa

Abstract. Episodic extreme waves due to sea storms can cause severe coastal erosion. The recovery times of such events are important for the analysis of risk and coastal vulnerability. The recovery period of a storm damaged coastline represents a time when the coastline is most vulnerable and nearby infrastructure is at the greatest risk. We propose that identification of the beach recovery period can be used as a coastal management tool when determining beach usage. As a case study, we analyse 37 yr of beach profile data on the east coast of South Africa. Considering beach length and cross-sectional area, we establish a global recovery period and rate and identify the physical characteristics of the coastlines that either accelerate or retard recovery. The beaches in the case study were found to take an average of two years to recover at a rate of approximately 90 m3 m−1 yr−1. Beach profiles with vegetated dunes recovered faster than urbanized beaches. Perpendicular beach structures have both positive and negative effects on beach recovery. Coastlines with rock outcrops in the surf zone tend to recover slowly and long-term sediment loss was identified in cases where storm damaged beaches have not recovered to pre-erosion levels.

First records of the echiurans Anelassorhynchus inanensis (Ikeda, 1904) and Ochetostoma pellucidum (Fischer, 1895) from the east coast of southern Africa (Echiuroinea: Echiuridae)

Two species of echiurans (Echiura), Anelassorhynchus inanensis (Ikeda, 1904) and Ochetostoma pellucidum (Fischer, 1895), were collected from intertidal rocky shores at Perriers Rock on the KwaZulu-Natal north coast. This is the first known record of these two species from South African waters and considerably extends their geographical ranges. A. inanensis, originally described by Ikeda (1904) from Naha, Japan, was later recorded and redescribed by Wesenberg- Lund (1939) from a single specimen from South Annam while Haldar & DattaGupta (1991) assigned two specimens from Kavaratti Island, on the southwest coast of India, to the species. O. pellucidum is based on several specimens collected from Whydah, West Africa. According to Stephen & Edmonds (1972) no illustrations of this species have been given while the description given by Wesenberg-Lund (1954) is based on a single badly-preserved specimen from French Guinea. Both species are redescribed and compared with other closely related forms.