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Major threats to South African estuaries include freshwater flow alterations, urbanisation, habitat transformation, deteriorating water quality, increased biological invasions and resource over-exploitation. Although South African estuary restoration is in its infancy, important lessons have been learnt through past efforts undertaken in some of the most impacted systems. This review presents case studies focused on hydrological and physical restoration actions, while recognizing the need to implement urgent remedial measures to restore the populations of targeted estuary-associated marine fish species. Common interventions designed to arrest declining estuary health include artificial management of estuary mouths and the use of artificial structures to restore tidal action and remediate erosion damage. Limited natural habitat restoration actions have been conducted on the subcontinent. Fortunately, estuaries are resilient ecosystems and can recover fairly rapidly if appropriate restoration interventions are successfully applied. Restoration needs to be co-ordinated through a national strategy which is currently not in place. It is particularly important to address the root cause of deterioration through active restoration and/or rehabilitation measures rather than only managing symptoms. The implementation of existing and future conservation legislation regarding the exploitation of natural resources within estuaries needs to be prioritised, so that over-exploited angling and subsistence fish species populations can recover. [ABSTRACT FROM AUTHOR]

Salt marshes protect estuary banks from erosion by acting as buffers between marine and terrestrial environments. Residents living near the Breede River estuary, Western Cape Province, South Africa, raised concerns about ongoing erosion evident at Groenpunt, the main salt marsh. This study aimed to determine how long erosion has been taking place, the rate and possible causes thereof. Aerial images and environmental data were assessed for the years 2002–2020. Erosion was first evident in 2003. By 2020, the marsh edge had been eroded into a series of micro-bays, incised horizontally up to 7 m, with a scarp height of 0.7 m, corresponding to a loss of 1 313 m2 of salt marsh and a bank retreat rate of 0.66 (SE 0.44) m year−1. Over the study period, there was a regular pattern of high-frequency gale-force winds (>8 on the Beaufort scale), with significantly more winds of this magnitude occurring in 2002 than in other years. The wind wave fetch adjacent to the marsh is up to 1 km in the direction of the predominant wind, and it is likely that the cumulative effects of constant wind-generated waves drove the erosion process. Estuary water and tidal levels over the period reflected normal seasonal fluctuation patterns. The bank supporting Groenpunt salt marsh is eroding at a rate that could possibly see it disappear within the next 60 years, reducing biodiversity and ecosystem services in the estuary. In the face of increasing climatic variability predicted in the future, similar salt marsh erosion is likely to become more prevalent. [ABSTRACT FROM AUTHOR]

The possible impacts of extreme events on the ecology of selected aquatic biota within the Mbhashe Estuary were investigated during a four year (2010–2013) spring sampling programme. During periods of low to average flow conditions the estuary is shallow, turbid and characterised by the presence of fluid mud and the build-up of mud and clay deposits. During these conditions, extremely high biomasses of intertidal microalgae and zooplankton are present. Fish and macroinvertebrate abundance and diversity are also highest during low-flow conditions. Flood events can reset, or partially disrupt, the sediment erosion/depositional cycle and decrease the biomass and diversity of plankton, fish and macroinvertebrate species. The Mbhashe Estuary's unique fluid mud habitat is therefore subjected to regular resetting, which potentially contributes to the fluid nature of the muds. A storm surge in 2011 resulted in the temporary dieback of an area of mangroves, as a result of the deposition of marine sediment. Although extreme events seem to play an important role in the deposition and erosion cycle of the estuary, an increased frequency of both types of extreme events may ultimately result in estuarine habitat loss, which will adversely affect the biota of the estuary. [ABSTRACT FROM AUTHOR]

This Reflections article highlights the growing pressures that southern African estuaries are experiencing in the Anthropocene, as identified by the research presented in this Special Medal Issue. Estuaries are exposed to multiple stressors, and their responses to climate change are becoming increasingly evident. As the health of estuaries deteriorates, so does their ability to deliver valuable ecosystem services. Although legislation in southern Africa exists to ensure freshwater inflow, maintain water quality, promote sustainable resource use and control development in estuary functional zones, implementation of these measures is lacking. In some cases, the legal instruments themselves are falling short, such as the general standards for wastewater discharge, which are insufficiently stringent to prevent estuary eutrophication. Research on estuaries has clearly identified how these pressures influence estuaries and where intervention is required. Issues requiring attention, such as those elucidated through the monitoring and management options related to the Lake St Lucia estuarine system, have also been highlighted. Looking to the future, there is a requirement for estuarine research, in order to support cooperative governance and the implementation of the Ecological Reserve and Estuary Management Plans. The time is also right for a National Estuary Restoration Programme. A socio-ecological systems framework for the future research, restoration and management of estuaries is presented and recommended as a way forward. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nutrient pollution in South African estuaries is described using a Driver-Pressure-State-Impact-Response framework. The root cause ('driver') of deteriorating water quality is rapid population growth that leads to increasing inputs from wastewater treatment works (WWTWs), stormwater run-off and agricultural return flow ('pressures'). Nationally, half of the country's estuaries are affected by nutrient pollution ('state'). This has elicited marked primary producer and secondary (hypoxia, fish kills, loss of ecosystem services) responses ('impact'). The Sundays and Swartkops Estuaries are eutrophic with phytoplankton blooms (>20 µg l−1) and bottom-water hypoxia. Similarly, the nationally important Knysna Estuary experiences eutrophic conditions associated with macroalgal blooms, whereas the Wildevoëlvlei and Zeekoe systems have transitioned to alternate stable states characterised by toxic cyanobacteria blooms, as a result of WWTW inputs and increased water residence times. The health of the St Lucia Estuary, a UNESCO World Heritage site, is under threat from agricultural inputs from the uMfolozi system. Nationally, better treatment and recycling of WWTW inputs is required to improve and restore estuary health. Owing to excessive WWTW effluent volumes, treatment to South Africa's uniform effluent standards no longer prevent eutrophication. Other urgent interventions needed are compliance monitoring, engineering solutions to reduce stormwater and wastewater input, and prudent application of agricultural fertilisers. [ABSTRACT FROM AUTHOR]

A third of South Africa's freshwater flow no longer reaches the coast, yet few systems have shifted from being permanently open to temporarily closed. For the first time since 1969, the Gamtoos Estuary mouth closed in June 2018, because of extensive drought conditions and freshwater abstraction. Accordingly, physico-chemical gradients, microalgal biomass and species composition were sampled during low (closed mouth), normal (open mouth) and high (breaching event) flow conditions. The closed phase was characterised by polyhaline and homogenous salinity structures and a rapid shift towards eutrophic conditions, as evidenced by bottom water hypoxia (<2 mg l−1), elevated phytoplankton (>20 μg l−1) and microphytobenthos (>100 mg m−2) biomass, and proliferation of a harmful algal bloom (HAB) species (Prorocentrum cordatum, Dinophyceae). An artificial breaching event in September 2018 restored connectivity with the marine environment and within a month re-established the usual physico-chemical gradients that characterise the open phase. Although the current study demonstrates ecosystem recovery from stochastic events, it also highlights the potential impact (e.g. HABs, hypoxia) of shifting an estuary into a new stable state. This is a concern given that mouth closure events in South African estuaries are likely to increase in the future in response to global change pressures. [ABSTRACT FROM AUTHOR]

The large Temporarily Closed Seekoei Estuary has a long history of poor management. In 1969, a swimming pool complex was built in a position impinging on the mouth. The construction of a 500 m causeway across the lagoon connecting the residential townships of Paradise Beach and Aston Bay followed. Freshwater abstraction in the catchment has escalated, whereas increasing sedimentation, duration and frequency of mouth closure and hypersaline events contributed to the deteriorating health status of the estuary. Pedestrian and vehicle numbers crossing the causeway are high, particularly among Paradise Beach residents who need to access schools, medical services, work premises, business and shopping facilities. Causeway maintenance is ongoing, whereas winter storm surges deposit large volumes of sand and seawater in the estuary. The causeway becomes submerged, exacerbating threats to human safety. The mouth is then artificially breached, sometimes illegally. Although causeway removal was a key objective in the management plan, upgrading or construction of alternate roads was a first requirement. Other management objectives included guidelines for artificial mouth breaching and restoration of freshwater runoff. Without freshwater inflow the health of the estuary will continue to deteriorate; the system cannot be managed by only focussing on mouth management or other non-natural structures. [ABSTRACT FROM AUTHOR]

This Reflections article highlights the growing pressures that southern African estuaries are experiencing in the Anthropocene, as identified by the research presented in this Special Medal Issue. Estuaries are exposed to multiple stressors, and their responses to climate change are becoming increasingly evident. As the health of estuaries deteriorates, so does their ability to deliver valuable ecosystem services. Although legislation in southern Africa exists to ensure freshwater inflow, maintain water quality, promote sustainable resource use and control development in estuary functional zones, implementation of these measures is lacking. In some cases, the legal instruments themselves are falling short, such as the general standards for wastewater discharge, which are insufficiently stringent to prevent estuary eutrophication. Research on estuaries has clearly identified how these pressures influence estuaries and where intervention is required. Issues requiring attention, such as those elucidated through the monitoring and management options related to the Lake St Lucia estuarine system, have also been highlighted. Looking to the future, there is a requirement for estuarine research, in order to support cooperative governance and the implementation of the Ecological Reserve and Estuary Management Plans. The time is also right for a National Estuary Restoration Programme. A socio-ecological systems framework for the future research, restoration and management of estuaries is presented and recommended as a way forward. [ABSTRACT FROM AUTHOR]

The possible impacts of extreme events on the ecology of selected aquatic biota within the Mbhashe Estuary were investigated during a four year (2010–2013) spring sampling programme. During periods of low to average flow conditions the estuary is shallow, turbid and characterised by the presence of fluid mud and the build-up of mud and clay deposits. During these conditions, extremely high biomasses of intertidal microalgae and zooplankton are present. Fish and macroinvertebrate abundance and diversity are also highest during low-flow conditions. Flood events can reset, or partially disrupt, the sediment erosion/depositional cycle and decrease the biomass and diversity of plankton, fish and macroinvertebrate species. The Mbhashe Estuary's unique fluid mud habitat is therefore subjected to regular resetting, which potentially contributes to the fluid nature of the muds. A storm surge in 2011 resulted in the temporary dieback of an area of mangroves, as a result of the deposition of marine sediment. Although extreme events seem to play an important role in the deposition and erosion cycle of the estuary, an increased frequency of both types of extreme events may ultimately result in estuarine habitat loss, which will adversely affect the biota of the estuary. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nutrient pollution in South African estuaries is described using a Driver-Pressure-State-Impact-Response framework. The root cause ('driver') of deteriorating water quality is rapid population growth that leads to increasing inputs from wastewater treatment works (WWTWs), stormwater run-off and agricultural return flow ('pressures'). Nationally, half of the country's estuaries are affected by nutrient pollution ('state'). This has elicited marked primary producer and secondary (hypoxia, fish kills, loss of ecosystem services) responses ('impact'). The Sundays and Swartkops Estuaries are eutrophic with phytoplankton blooms (>20 µg l−1) and bottom-water hypoxia. Similarly, the nationally important Knysna Estuary experiences eutrophic conditions associated with macroalgal blooms, whereas the Wildevoëlvlei and Zeekoe systems have transitioned to alternate stable states characterised by toxic cyanobacteria blooms, as a result of WWTW inputs and increased water residence times. The health of the St Lucia Estuary, a UNESCO World Heritage site, is under threat from agricultural inputs from the uMfolozi system. Nationally, better treatment and recycling of WWTW inputs is required to improve and restore estuary health. Owing to excessive WWTW effluent volumes, treatment to South Africa's uniform effluent standards no longer prevent eutrophication. Other urgent interventions needed are compliance monitoring, engineering solutions to reduce stormwater and wastewater input, and prudent application of agricultural fertilisers. [ABSTRACT FROM AUTHOR]

A third of South Africa's freshwater flow no longer reaches the coast, yet few systems have shifted from being permanently open to temporarily closed. For the first time since 1969, the Gamtoos Estuary mouth closed in June 2018, because of extensive drought conditions and freshwater abstraction. Accordingly, physico-chemical gradients, microalgal biomass and species composition were sampled during low (closed mouth), normal (open mouth) and high (breaching event) flow conditions. The closed phase was characterised by polyhaline and homogenous salinity structures and a rapid shift towards eutrophic conditions, as evidenced by bottom water hypoxia (<2 mg l−1), elevated phytoplankton (>20 μg l−1) and microphytobenthos (>100 mg m−2) biomass, and proliferation of a harmful algal bloom (HAB) species (Prorocentrum cordatum, Dinophyceae). An artificial breaching event in September 2018 restored connectivity with the marine environment and within a month re-established the usual physico-chemical gradients that characterise the open phase. Although the current study demonstrates ecosystem recovery from stochastic events, it also highlights the potential impact (e.g. HABs, hypoxia) of shifting an estuary into a new stable state. This is a concern given that mouth closure events in South African estuaries are likely to increase in the future in response to global change pressures. [ABSTRACT FROM AUTHOR]

The large Temporarily Closed Seekoei Estuary has a long history of poor management. In 1969, a swimming pool complex was built in a position impinging on the mouth. The construction of a 500 m causeway across the lagoon connecting the residential townships of Paradise Beach and Aston Bay followed. Freshwater abstraction in the catchment has escalated, whereas increasing sedimentation, duration and frequency of mouth closure and hypersaline events contributed to the deteriorating health status of the estuary. Pedestrian and vehicle numbers crossing the causeway are high, particularly among Paradise Beach residents who need to access schools, medical services, work premises, business and shopping facilities. Causeway maintenance is ongoing, whereas winter storm surges deposit large volumes of sand and seawater in the estuary. The causeway becomes submerged, exacerbating threats to human safety. The mouth is then artificially breached, sometimes illegally. Although causeway removal was a key objective in the management plan, upgrading or construction of alternate roads was a first requirement. Other management objectives included guidelines for artificial mouth breaching and restoration of freshwater runoff. Without freshwater inflow the health of the estuary will continue to deteriorate; the system cannot be managed by only focussing on mouth management or other non-natural structures. [ABSTRACT FROM AUTHOR]

The use of diatoms as bioindicators to detect human-induced change is a globally accepted monitoring tool. DNA metabarcoding is an effective complementary tool to standard microscopic methods for species identification, providing reliable and timeous diatom assessments in a range of aquatic ecosystems. This study evaluated the suitability of the DNA metabarcoding approach for diatom monitoring in the St Lucia Estuary, South Africa. Results obtained from the standard microscopic (morphological) and molecular methods were compared and indicated a low similarity in the vegetated (11%), unvegetated (12%) and epiphytic (12%) habitats at species level for the epipelic and epiphytic diatom communities. The difference between the methods was expected given the challenges pertaining to the incomplete molecular reference database, intragenomic variability, physiological differences (number of chloroplasts) and highly variable microphytobenthos biomass. While the molecular method was unable to identify the presence of all the dominant diatom species (routinely used as ecological indicators), the available molecular operational taxonomic units (MOTUs) provided an effective complementary tool to determine the relevant community diversity estimates required for the application of the South African estuarine health index (EHI). [ABSTRACT FROM AUTHOR]

The permanently eutrophic Sundays Estuary experiences recurrent harmful algal blooms (HABs) of Heterosigma akashiwo (Raphidophyceae). This study aimed to identify the environmental variables shaping phytoplankton community composition and succession patterns during a typical spring/summer harmful algal bloom (HAB) period. Monitoring of abiotic and phytoplankton variables was undertaken over the period of a month in 2016. Surface water salinity corresponding to mesohaline conditions (9 to 12) was a prerequisite for site selection. During the study, two HABs (>550 µg Chl a l−1) of H. akashiwo occurred, each lasting for approximately a week in duration. Analyses highlighted nutrient depletion (i.e. nitrate and phosphate concentrations) as the key constraint on bloom duration. When the density of H. akashiwo decreased, the community composition became more diverse with species belonging to Bacillariophyceae and Dinophyceae becoming more abundant; albeit to a lesser degree (<180 µg Chl a l−1). Dissolved oxygen shifted from super-saturated conditions (>14 mg l−1) during peak HAB conditions, to instances of bottom water oxygen depletion (2-4 mg l−1) during the decay phase. These findings highlight the potential severity of transforming a catchment from natural to one that is highly regulated by agricultural practices, while also emphasising the need for management intervention. [ABSTRACT FROM AUTHOR]

This article presents a historical overview of estuarine microphytobenthos (MPB) research in South Africa published over the period 1950 to the present, highlighting major milestones, challenges and estuarine management problems, as well as future research needs within the South African context. The studies that were covered comprise peer-reviewed books and journal articles on relevant research conducted in any estuarine environment during the period reviewed. There was a general increase in MPB research outputs over the decades, from only two publications in the 1950s, to over 20 outputs between 2010 and the present. Whereas the MPB studies in South Africa cover a broad spectrum of themes, the research priorities in these works have changed from taxonomically biased studies to those of ecologically based research. Research in the 1950s and 1960s was exclusively taxonomic in nature, with the first ecological investigation incorporating MPB being produced in the 1970s. By the 1980s, ecological studies dominated the research outputs and this trend has persisted to the present. The 1990s and 2000s saw the rise of research into the role of fresh water as a driver of MPB dynamics, whereas the period 2010 to the present saw an increase in more diverse ecological themes, ranging from an autecological investigation to food-web studies and the assessment of multiple drivers of MPB dynamics. However, the majority of studies have focused on either diatoms or estimates of overall MPB biomass. Moreover, there is a regional underrepresentation that runs broadly along biogeographic lines, with the bulk of the work having been conducted in the warm-temperate and subtropical zones of South Africa. Challenges and future research needs for the region are outlined, as is the need to expand MPB research to include other aspects of the biology and ecology of this flora. [ABSTRACT FROM AUTHOR]

This study investigated whether the current lateral boundary for estuaries in South Africa, i.e. the estuarine functional zone (EFZ), includes all estuarine habitats. The EFZ covers 173 930 ha in 304 estuaries/outlets nationally. Field surveys and analysis of available aerial images showed that 82 (12 956.70 ha) of these estuaries (26%) had estuarine habitats occurring outside of this boundary. As a result of mapping scale, the National Vegetation Map does not represent habitats that are associated with small estuaries (approximately 50% of South Africa's estuaries). For estuaries in the Western and Eastern Cape provinces, most habitats have been lost due to urban development, whereas in subtropical areas (northern Eastern Cape and KwaZulu-Natal), cultivation has removed estuarine habitat. Although delineation of boundaries can be complicated by landcover changes, the estuarine lateral boundary in Cape estuaries could be identified based on sediment characteristics (moisture content, organic content, electrical conductivity), groundwater characteristics (salinity, conductivity and depth) and plant species. The delineation of the EFZ needs to be consistent, inclusive of all estuarine physical and biological processes, and cost-effective to identify so that it can protect estuarine habitats. [ABSTRACT FROM AUTHOR]

Low river inflow conditions during 2009/2010 resulted in the mouth of the Great Brak Estuary remaining closed for almost two years. The low water level in Wolwedans Dam resulted in no annual environmental flow releases being made, causing mouth closure. The response of primary producers to this prolonged period of mouth closure was investigated in 2010/2011. Urban and agricultural development in the river catchment and along the estuary banks had increased the nutrient inputs into the estuary. Mouth closure, combined with elevated nutrient concentrations, increased the growth of both macroalgae and microalgae, but little change was observed in the submerged macrophytes. Macroalgal mats covered large areas of open-water surface, smothering the salt marsh and causing a decrease in its cover. These results have important implications for the management of temporarily open/closed estuaries, as increased development, freshwater abstraction and reduced river flow will result in prolonged periods of closure and reduced tidal exchange, which is likely to lead to eutrophication. [ABSTRACT FROM AUTHOR]

The effect of a prolonged closed-mouth state on the condition of mangrove habitats was studied in May 2010 at St Lucia Estuary, KwaZulu-Natal. The mouth had been closed to the sea since 2002 as a result of artificial mouth closure and drought, which had resulted in non-tidal, dry and hypersaline aquatic conditions. Sediment characteristics, mangrove population structure, and snail and crab abundance, were measured at four sites of differing salinity and water level to determine if there was a relationship between environmental characteristics and biotic response. A site fringing the main channel had the lowest elevation and the highest density of mangrove seedlings and saplings at the water's edge, whereas a dry site at the highest elevation had the lowest density of mangroves with mostly tall adult trees and few saplings. At these two sites the salinity (>34.5) was significantly higher and the surface sediment water content (<30%) was significantly lower than at other sites. Highest tree density was found at a freshwater seepage site, where all size classes were represented, while the permanently flooded site between the Mfolozi River and St Lucia Estuary had the tallest trees but no seedlings or saplings. At the freshwater seepage and permanently flooded sites, porewater and sediment salinity (<10) were significantly lower, while sediment moisture (>55.5%) was significantly higher, than at the fringing and dry sites. Low sediment moisture was unfavourable for mangrove growth and recruitment. Long-term monitoring is needed to document the response of the mangroves to closed-mouth, non-tidal conditions. [ABSTRACT FROM AUTHOR]

Spartina alterniflora Loisel., widely recognised as an aggressive invader of estuaries and salt marshes around the world, was discovered growing in the temporarily open/closed Great Brak Estuary on the southern Cape coast of South Africa in 2004. This is the first record of this invasive plant in Africa as well as its first occurrence in an estuary that closes to the sea. Plant traits and sediment characteristics were measured in 2009 and 2011 and found to be comparable to those reported elsewhere. Prior to the 2011 sampling, S. alterniflora stands had been flooded for almost eight months. As a result, sediment redox potential (−268 + 4 mV) was significantly lower in 2011. Sediments were mostly clay in 2009 (71 ± 0.01%) compared to a predominance of sand in 2011 (40 ± 0.02%). These differences were related to the artificial breaching of the estuary one month prior to sampling in March 2011. The grass currently occupies 1.1 ha in the salt marsh, sandflat and mudflat habitats of the estuary where its cover is expanding at a rate of 0.162 ha y−1. Individual stands numbered about 12 in 2006, but have increased to 24 in 2011. These stands are expanding laterally at 0.9 m y−1 although the long period of inundation during 2010 reduced this to 0.6 m y−1. Expansion is due to vegetative spread as an analysis of the sediment seed bank showed no S. alterniflora seeds and very few salt marsh seeds (1 132 seeds m−2). If left unchecked, S. alterniflora has the potential to replace 42.9 ha or 41% of the total estuary habitat in the Great Brak Estuary, but also has the potential to invade other estuaries in South Africa, especially those with extensive intertidal habitat and containing S. maritima (19 estuaries in total). This study illustrates the adaptive potential of this invasive marsh plant and indicates the possibility of invasion in seasonally closed estuaries in other locations around the world. [ABSTRACT FROM AUTHOR]

This study investigated the use of δ15N levels in Phragmites australis reeds as an indicator of nutrient input into the small temporarily open/closed East Kleinemonde Estuary, Eastern Cape, South Africa. Nutrient (NH4 and SRP) concentrations decreased from the bank towards the main estuary channel, suggesting that nutrients introduced into the estuary in groundwater and surface runoff were taken up by the fringe of reeds. The roots, rhizomes, stems and leaves of Phragmites at the site with the greatest Phragmites biomass and density had significantly higher δ15N (∼20‰) than the leaves at a site with no groundwater input, consistent with nutrient enrichment by septic tank wastewater and stormwater runoff. This study suggests that the δ15N level in reeds can be used to detect enrichment in small estuaries threatened by changing land use and deteriorating water quality. [ABSTRACT FROM AUTHOR]

Power is an important component of general health, fitness, and athletic performance. Traditional overload techniques require considerable time, intensity, and volume of training. Whole-body vibration (WBV) is a potentially less time-consuming method for increasing power performance than traditional training. However, the exact protocols that can maximize power output have not yet been identified. Eleven healthy men, aged 32.3 +/- 4.1 years, and 9 healthy women, aged 29.1 +/- 3.5 years, performed countermovement jumps (CMJs) of maximal volition to assess peak power pre and post (immediately and at 1, 5, and 10 minutes) randomized WBV stimuli set at different frequency (30, 35, 40, and 50 Hz), displacement (2-4 vs. 4-6 mm), and duration (30, 45, and 60 seconds) combinations. Repeated-measures analysis of variance on peak power normalized to initial power (nPP) revealed no significant effects attributable to duration of stimulus. However, high frequencies were more effective when combined with high displacements, and low frequencies were more effective in conjunction with low displacements (p < 0.05). Additionally, the greatest improvements in nPP occurred at 1 minute posttreatment, with significant improvements lasting through 5 minutes posttreatment (p < 0.05). Optimal acute effects can be attained using as little as 30 seconds of WBV, and they are highest from 1 to 5 minutes posttreatment. Additionally, high frequencies were most effective when applied in conjunction with high displacements, whereas low frequencies were most effective when applied in conjunction with low displacements. [ABSTRACT FROM AUTHOR]

Background: There have been many studies of the effect of high-dose supplementation of vitamin B(6) on children and adults with autism, with all but one reporting benefits. Objective: The aim of this study was to investigate the biochemical basis for vitamin B(6) therapy by measuring the level of total vitamin B(6) in the plasma of unsupplemented children with autism spectrum disorder compared to unsupplemented control subjects. Participants: Children with autism spectrum disorders (n = 35, age 3-9 years) and unrelated typical children (n = 11, age 6-9 years), all from Arizona, were studied. (This includes the data from 24 children with autism from our previous study.) Methodology: A microbiologic assay was used to measure the level of total vitamin B6 (including phosphorylated and unphosphorylated forms), in a blinded fashion. Results: Children with autism had a 75% higher level of total vitamin B(6) than the controls (medians of 56 versus 32 ng/mL, respectively, p = 0.00002). Most of the autistic children (77%) had levels that were more than 2 standard deviations above the median value of the controls. The autistic girls (n = 5) also had elevated levels (mean of 54.6 ng/mL, median of 60 ng/mL). Discussion: These results are consistent with previous studies that found that: (1) pyridoxal kinase had a very low activity in children with autism and (2) pyridoxal 5 phosphate (PLP) levels are unusually low in children with autism. Thus, it appears that the low conversion of pyridoxal and pyridoxine to PLP results in low levels of PLP, which is the active cofactor for 113 known enymatic reactions, including the formation of many key neurotransmitters. Conclusions: Total vitamin B(6) is abnormally high in autism, consistent with previous reports of an impaired pyridoxal kinase for the conversion of pyridoxine and pyridoxal to PLP. This may explain the many published studies of benefits of high-dose vitamin B(6) supplementation in some children and adults with autism. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Determine the effect of a moderate dose multivitamin/mineral supplement on children with autistic spectrum disorder. DESIGN: Randomized, double-blind, placebo-controlled 3-month study. SUBJECTS: Twenty (20) children with autistic spectrum disorder, ages 3-8 years. RESULTS: A Global Impressions parental questionnaire found that the supplement group reported statistically significant improvements in sleep and gastrointestinal problems compared to the placebo group. An evaluation of vitamin B(6) levels prior to the study found that the autistic children had substantially elevated levels of B6 compared to a control group of typical children (75% higher, p < 0.0000001). Vitamin C levels were measured at the end of the study, and the placebo group had levels that were significantly below average for typical children, whereas the supplement group had near-average levels. DISCUSSION: The finding of high vitamin B(6) levels is consistent with recent reports of low levels of pyridoxal-5-phosphate and low activity of pyridoxal kinase (i.e., pyridoxal is only poorly converted to pyridoxal-5-phosphate, the enzymatically active form). This may explain the functional need for high-dose vitamin B(6) supplementation in many children and adults with autism. [ABSTRACT FROM AUTHOR]

Subtidal habitats have not yet been accounted for in habitat maps of South African estuaries. In this study, a novel method for mapping subtidal estuarine habitats, using a remotely operated underwater vehicle (ROV) piloted from a boat, was developed and tested in the Knysna Estuary. Video footage was recorded along 48 transects across the width of the estuary, and then reviewed to identify, classify and map habitats. Using the method developed in this study, 21 hours of footage was recorded over 15 days of sampling, and about 30 hours of post-processing was carried out to map an area exceeding 850 ha. This study has produced the first baseline dataset of subtidal habitats for a South African estuary. Additionally, the study revealed the previously unknown distribution of the invasive red seaweed Asparagopsis taxiformis, and the underestimation in previous studies of the estuary of area cover of eelgrass Zostera capensis by 130 ha. [ABSTRACT FROM AUTHOR]

Globally, the ability of estuaries to sustain functionality and productivity is deteriorating rapidly under ever-increasing anthropogenic pressures. We present a systematic approach to identify, characterise and rank global pressures affecting estuaries. Six main pressure categories are reviewed: freshwater flow modification; pollution; exploitation of fish and invertebrates; land-use and development; manipulation of inlets; and biological invasions (plants and fish). Patterns in pressure effects are evaluated across biogeographic regions and estuary types. Activities contributing to these pressures are identified to prioritise management interventions and assessments of the trajectories of change and data availability are estimated, with associated confidence ratings on these. Approximately 15% of national estuarine area is under severe flow modification pressure. Land-use and development result in severe pressures on 40% of the area. Approximately 15% of inlets are artificially manipulated, which affects 60% of estuarine area. Pollution places 34% of the area under severe pressure and 78% of the area is severely impacted by overfishing. Invasive terrestrial vegetation has infested a third of South African estuaries, and aquatic invasive plant species occur in at least 8% of estuaries. Alien or extralimital (translocated) fish cause severe pressure in 35% of the estuaries. Management responses to mitigate these impacts are recommended for systems under severe pressure and future research directions are identified. [ABSTRACT FROM AUTHOR]

Research in South African temporarily open/closed estuaries that includes studies on the hydrodynamics, sediment dynamics, macronutrients, microalgae, macrophytes, zoobenthos, hyperbenthos, zooplankton, ichthyoplankton, fishes and birds is used as a basis to review the ecology and management of this estuary type on the subcontinent. Particular attention is given to the responses of the different ecosystem components to the opening and closing of the estuary mouth and how this is driven by riverine and marine events, as well as anthropogenic influences. In addition, the wider implications of these research findings for the management of temporarily open/closed estuaries in terms of freshwater supply are explored, together with the role of government legislation in maintaining the ecological integrity of these important wetland systems. [ABSTRACT FROM AUTHOR]

The occurrence of harmful algal blooms (HABs) is increasing in frequency and intensity in South African estuaries because of eutrophication. This study used DNA metabarcoding to identify the benthic diatom community structure in the eutrophic Sundays Estuary. The recurrent HAB phytoplankton species Heterosigma akashiwo was recorded at bloom concentrations (∼100 µg Chl a l−1) in the brackish, vertically stratified middle reaches of the estuary. In contrast, microphytobenthos biomass increased towards the upper reaches in response to elevated availability of total oxidised nitrogen (NOx) and increased sediment stability. A total of 76 diatom species were identified using the molecular technique. Seven known nutrient-tolerant diatom species indicate a preference for either ammonium or NOx enrichment. Benthic diatom community diversity (H′ < 1) and evenness (J′ < 0.25) were low in the brackish middle reaches of the estuary, where the HABs decreased available light. Heterosigma akashiwo has been found in previous studies to suppress the growth of co-occurring taxa. Future research efforts should focus on verifying this relationship over seasonal timescales given the dominance of H. akashiwo in spring/summer. As the persistently nutrient-enriched state and stable flow conditions of the Sundays Estuary is the key driver of change, management efforts should be geared towards re-establishing the estuary's natural flow variations and to measures that can mitigate nutrient pollution. [ABSTRACT FROM AUTHOR]

The Knysna Estuary is South Africa's most important estuary in terms of conservation, containing an estimated 42% of all estuarine biodiversity. Despite formal protection the estuary is open access and vulnerable to resource exploitation, development, pollution and freshwater inflow alterations. Through a review of current research and available data, the current study evaluated the ecological status of the Knysna Estuary, identified major pressures and proposed future management and conservation actions. Notable impacts included deteriorating water quality, development and resource use pressures. Nuisance macroalgal blooms in response to eutrophication have increased, displacing important seagrass habitats and affecting biota, including an increase in alien species. This review found that the ecological health of the Knysna Estuary is deteriorating, which suggests limited success from current conservation and management actions. Monitoring data to effectively assess system change over time were notably absent. Suggested remediation actions include halting non-compliant discharges from the Knysna Waste Water Treatment Works and the development of goal-orientated monitoring programmes to enable proactive conservation. Successful conservation depends on cross-sectorial management of the estuary and surrounds, and support is required from multiple institutions to achieve this. [ABSTRACT FROM AUTHOR]

This study investigated seasonal dynamics of benthic nutrient fluxes using in situ benthic chambers deployed over a 24–hour period at the sediment water interface for four distinct regions of the Knysna Estuary. The sediment in the Upper Estuary, Lagoon and Bay acted as a source of NH4 with a rate of 100–300 µmol m−2 day−1 N, and soluble reactive phosphorus (SRP) with a rate of 15 µmol m−2 day−1 P, whereas that of Ashmead channel exceeded these rates by far. The sediment acted as a sink for NO3− with fluxes of between −200 and 100 µmol m−2 h−1. Benthic nutrient fluxes in the estuary were positively related with sediment organic content and silt. Nutrient fluxes in the Ashmead channel were significantly greater than the other regions because of the anoxic sediment, reduced flushing and a legacy of pollutant and organic matter retention. This condition can only be improved by removing wastewater input and dredging. Such drastic interventions are necessary to improve the health of South Africa's top ranked estuary in terms of biodiversity importance. [ABSTRACT FROM AUTHOR]

Sea-level rise is a significant threat to salt marshes. However, these habitats can respond by increasing their relative elevation, or by migrating into adjacent areas. Here we provide the first report on surface elevation change for salt marsh at the Knysna Estuary, South Africa, and predict the responses of these habitats to sea-level rise using the Sea-Level Affecting Marshes Model (SLAMM). Recent (2018) surface elevation measurements at lower intertidal salt marsh sites were compared with those from 2009–2011. The long-term (1960–2017) relative sea-level rise (RSLR) was estimated as 2.19 mm y−1 and only two of the seven sites assessed are keeping pace with this RSLR. The SLAMM, which was applied to a focus area near Thesen's Island, predicted up to 40% loss of upper intertidal salt marsh by 2100, because development in the adjacent area prevents habitat migration. Currently, salt marsh habitats cover a total of 667 ha, and artificial structures are present along 20.7 km of the perimeter. Protecting areas for salt marsh migration should be a conservation priority, because this estuary supports the third largest area of intertidal salt marsh in the country. Monitoring the responses of coastal wetlands should be prioritised so that natural capital contributes towards future resilience. [ABSTRACT FROM AUTHOR]

The Knysna Estuary is South Africa's most important estuary in terms of conservation, containing an estimated 42% of all estuarine biodiversity. Despite formal protection the estuary is open access and vulnerable to resource exploitation, development, pollution and freshwater inflow alterations. Through a review of current research and available data, the current study evaluated the ecological status of the Knysna Estuary, identified major pressures and proposed future management and conservation actions. Notable impacts included deteriorating water quality, development and resource use pressures. Nuisance macroalgal blooms in response to eutrophication have increased, displacing important seagrass habitats and affecting biota, including an increase in alien species. This review found that the ecological health of the Knysna Estuary is deteriorating, which suggests limited success from current conservation and management actions. Monitoring data to effectively assess system change over time were notably absent. Suggested remediation actions include halting non-compliant discharges from the Knysna Waste Water Treatment Works and the development of goal-orientated monitoring programmes to enable proactive conservation. Successful conservation depends on cross-sectorial management of the estuary and surrounds, and support is required from multiple institutions to achieve this. [ABSTRACT FROM AUTHOR]

This study investigated seasonal dynamics of benthic nutrient fluxes using in situ benthic chambers deployed over a 24–hour period at the sediment water interface for four distinct regions of the Knysna Estuary. The sediment in the Upper Estuary, Lagoon and Bay acted as a source of NH4 with a rate of 100–300 µmol m−2 day−1 N, and soluble reactive phosphorus (SRP) with a rate of 15 µmol m−2 day−1 P, whereas that of Ashmead channel exceeded these rates by far. The sediment acted as a sink for NO3− with fluxes of between −200 and 100 µmol m−2 h−1. Benthic nutrient fluxes in the estuary were positively related with sediment organic content and silt. Nutrient fluxes in the Ashmead channel were significantly greater than the other regions because of the anoxic sediment, reduced flushing and a legacy of pollutant and organic matter retention. This condition can only be improved by removing wastewater input and dredging. Such drastic interventions are necessary to improve the health of South Africa's top ranked estuary in terms of biodiversity importance. [ABSTRACT FROM AUTHOR]

Sea-level rise is a significant threat to salt marshes. However, these habitats can respond by increasing their relative elevation, or by migrating into adjacent areas. Here we provide the first report on surface elevation change for salt marsh at the Knysna Estuary, South Africa, and predict the responses of these habitats to sea-level rise using the Sea-Level Affecting Marshes Model (SLAMM). Recent (2018) surface elevation measurements at lower intertidal salt marsh sites were compared with those from 2009–2011. The long-term (1960–2017) relative sea-level rise (RSLR) was estimated as 2.19 mm y−1 and only two of the seven sites assessed are keeping pace with this RSLR. The SLAMM, which was applied to a focus area near Thesen's Island, predicted up to 40% loss of upper intertidal salt marsh by 2100, because development in the adjacent area prevents habitat migration. Currently, salt marsh habitats cover a total of 667 ha, and artificial structures are present along 20.7 km of the perimeter. Protecting areas for salt marsh migration should be a conservation priority, because this estuary supports the third largest area of intertidal salt marsh in the country. Monitoring the responses of coastal wetlands should be prioritised so that natural capital contributes towards future resilience. [ABSTRACT FROM AUTHOR]

South Africa has approximately 200 micro-estuaries and micro-outlets along its more than 3 000 km of coastline. Many of these microsystems (i.e. micro-outlets and micro-estuaries) share some characteristics with temporarily open/closed estuaries, but differ in that they are supplied by localised catchments with limited supply of freshwater and less connectivity to the marine environment. Between 2015 and 2016 we investigated whether micro-outlets and micro-estuaries can be differentiated from each other and other estuaries based on physico-chemical properties, microalgal dynamics, as well as species diversity and composition of invertebrate communities. The micro-outlets were dominated by oligohaline or freshwater conditions, whereas micro-estuaries were mostly mesohaline. Microalgal biomass in both system types was influenced by temperature, nutrient concentration and light availability. The micro-estuaries had a higher microalgal biomass than the micro-outlets. Chironomidae and Ephemeroptera numerically dominated benthic macroinvertebrate micro-outlet communities, whereas Amphipoda and Mysida were most dominant in micro-estuaries. Calanoid copepods dominated zooplankton assemblages in micro-estuaries and macroinvertebrate larvae in micro-outlets. In addition, the zooplankton densities were significantly higher (p < 0.05) in micro-estuaries compared with micro-outlets. Study results confirm that there are major differences between the biota in the two microsystem types, accordingly making biotic assemblages, together with physico-chemical parameters, a viable tool for differentiating between micro-estuaries and micro-outlets. [ABSTRACT FROM AUTHOR]

Mangrove macrobenthos species are used as ecological indicators as they are sensitive to changes in sediment properties. In this study, the population density of the common mangrove whelk Cerithidea decollata was assessed during different environmental conditions in the St Lucia Estuary, South Africa. Previously, this species was found to persist through both hypersaline and freshwater-dominated conditions. The natural variability in C. decollata populations could provide information on the potential for this widespread species to be used as an ecological indicator in mangroves. We found that snail population density as well as sediment conductivity, moisture content and organic content differed between three mangrove sites that were monitored between 2010 and 2015. The relationship between snail population density and physicochemical characteristics of the sediment was therefore investigated using a mixed-effects model, and sediment conductivity was found to be the best predictor of C. decollata abundance. The resistance of this species to environmental variability could inform on resilience to ecological shifts, which is important when measuring responses associated with climate change. [ABSTRACT FROM AUTHOR]

Mangroves occur in South African estuaries at their poleward distribution limits, extending into temperate habitats. In 1963, William Macnae published the first comprehensive assessment of mangrove swamps in South Africa and made firsthand observations of these mangrove ecosystems. This article reassesses South African mangrove habitats, highlighting changes since Macnae’s assessment, through a literature review of research done in the past 50 years and using the results of a dedicated mangrove survey spanning 2012-2017. Until now, changes have been recorded mostly for mangrove vegetation, including a change in mangrove cover and a poleward shift of mangrove species. While some mangrove-associated fauna have disappeared from most sites (e.g. the gastropod Terebralia palustris), others, such as fiddler crabs, have spread farther south. The effects of decreasing diversity with an increase in latitude were not observed along the South African coast. Instead, habitat quality and estuarine mouth state seem to exert greater influence on species diversity in the mangroves, and a poleward shift in species distribution is now evident not just for the mangrove flora but for the fauna as well. South African mangrove research needs to include a continuous monitoring plan, especially if we are to contribute to global knowledge on blue carbon, the effects of sea-level rise, and the resilience of the mangrove ecosystem. [ABSTRACT FROM AUTHOR]

Unlabelled: Wear and osteolysis continue to be major reasons for revision surgery in THA. Ceramic-on-ceramic bearings eliminate polyethylene wear debris. The newest generation of these bearings incorporate nanosized, yttria-stabilized tetragonal zirconia particles producing an alumina matrix composite. We asked whether this new material would perform as well as a conventional bearing in terms of functional hip scores, radiographic migration and osteolysis, complications and survival. As part of a US FDA investigational device exemption study (G000075), we conducted an initial prospective safety study of 21 alumina matrix composite femoral heads articulating on alumina liners followed by a prospective, randomized study with 44 more of these articulations and 45 zirconia femoral heads on polyethylene liners. The minimum followup for all patients was 26 months (mean, 73 months; range, 26-108 months). Harris hip scores and radiographic findings were similar in the two groups as was survivorship (trial 95% versus control 93%). There were three reoperations in the trial group and three in the control group. A fractured head retrieval showed a 33% monoclinic transformation with an increase in surface roughness from 3 to 5 nm at the main wear zone. While our numbers were insufficient to compare device-related complications, the trial device performed as well as the control device in terms of reoperation, and clinical and radiographic outcome. The alumina matrix composite femoral head on an alumina liner provided high survivorship.Level Of Evidence: Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

Unlabelled: Tapered titanium porous plasma-sprayed components have performed well in primary THA. To confirm the literature at longer followup we retrospectively reviewed all 1639 patients who underwent 2000 THAs in which a specific porous femoral component was used. One hundred fourteen patients (134 hips) were lost to followup leaving a cohort of 1525 patients (1866 THAs). The component is a tapered titanium plasma spray-coated design that remained relatively unchanged since its first implantation except for circumferential proximal porous coating added in 1986 and an offset option added in 1999. Minimum followup was 24 months (average, 119 months; range, 24 to 275 months). To date there have been 39 femoral revisions for an implant survival of 98%. Using the Kaplan-Meier method, cumulative survival with any stem revision as the end point was 98.6% at 5 years, 98.4% at 10 years, 97.1% at 15 years, and 95.5% at 20 years. Using aseptic revision for failure of ingrowth as the endpoint, stem survival was 99.1%. Kaplan-Meier cumulative survival with aseptic revision for failure of ingrowth as the endpoint was 99.4% at 5 years, 99.3% at 10, 15 and 20 years. Harris hip pain and total scores improved. This titanium, porous plasma spray-coated femoral component continues to demonstrate high long-term survival with a low rate of component revision for any reason or aseptic failure of ingrowth. Level Of Evidence: Level IV, therapeutic study (case series). See the Guidelines for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]