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3. Diagram of non-barred estuary morphology showing plan (A) and crosssectional (B) perspective. Note the intertidal barrier that is submerged at high tide and emergent at low tide. In such systems insufficient sediment is available to permit mouth closure. The fluvial delta upstream marks the limit of progradation of coarsegrained riverine sediment.
Citations
... Despite having a common nursery function across the globe, estuaries vary widely in terms of their biogeography, typology, and physico-chemical characteristics (Harrison et al. 2000). Estuaries in the temporate regions of the Southern Hemisphere are typically shallower than those of the Northern Hemisphere, and many are seasonally isolated from the sea by the formation of a sandbar at their mouth during periods of low riverine inflow (Whitfield and Bate 2007;Wooldridge et al. 2018). ...
The temporarily open-closed (TOCE) Seekoei Estuary, on the warm temperate coast of South Africa, has been subject to various anthropogenic modifications such as impoundments, water abstraction, causeway construction, and artificial breaches that have impacted its estuarine functioning. To determine the impact of these combined factors on the fish community, the Seekoei Estuary was sampled twice per season over 2 years, which included a hypersaline phase. A total of 92,026 fishes, comprising 12 families and 25 species, were caught from five different habitat types using a 30 m × 1.7 m seine net (10-mm mesh aperture). The catches were dominated by the exclusively estuarine species Gilchristella aestuaria (81.0%) (Clupei-dae), followed by the estuarine and marine Atherina breviceps (11.4%) (Atherinidae) and the marine estuarine-dependent Rhabdosargus holubi (5.1%) (Sparidae). Fish catch-per-unit effort (CPUE) were similar among seasons and sites; however, species richness was highest (d = 1.24) at the site directly below an obstructing causeway hindering fish migration. Additionally , reoccurring hypersaline conditions due to low freshwater inflow and artificial breaching have resulted in frequent fish kills of mainly marine origin species, creating an anthropogenically mediated ecological trap. The current anthropogenic alterations require amelioration for the conservation of the fish and the ecological functioning of this estuary. Rehabilitation to restore functioning is important for estuaries globally, especially estuaries with low inflow.
... WQI is a mathematical equation used to transform large number of water quality data into a single number. Various modifications in WQI have also been incorporated in the recent years (Nives, 1999;Swamee et al., 2000;Harrison et al., 2000;Faisal et al., 2003;Ahmad et al., 2004;Shiow-Mey et al., 2004). This objective is achieved by determining the classes of all on grid basis (1' X 1') and were analysed by the Weighted Arithmetic Index Method (Brown et al., 1972) ...
Groundwater resources are mainly affcted by three major activities which include excessive use of fertilizers and
pesticides in agricultural land, untreated/partially treated water and through excessive pumping and improper management of
aquifers. Assessment of water quality for drinking purposes based on data is tough, because a number of parameters compromise
water quality. In recent times, there has been considerable advancement in assessment methods based on the principle of Water
Quality Index (WQI) using subtle modifiations as per site specifi requirements. Water Quality Index (WQI) reflcts the
composite inflence of diffrent water quality parameters considered for calculation. In the present study, 81 groundwater samples
were collected on grid pattern adhering to the standard protocol prescribed by the American Public Health Association (APHA).
Sixteen water quality parameters have been considered for calculation of water quality index viz. pH, Electrical Conductivity
(EC), Total Hardness (TH), Total Dissolved Solid (TDS), Sodium (Na+), Potassium (K+), Calcium (Ca2+), Magnesium (Mg2+),
Nitrates (NO3−), Bicarbonate (HCO3−), Chlorides (Cl−), Sulphates (SO42−), Fluorides (F−), Zinc (Zn), Copper (Cu) and Iron (Fe).
The guideline envisaged in Bureau of Indian Standard has been followed to assess the suitability of groundwater for drinking
purposes and for the calculation of Water Quality Index (WQI). Correlation study among various physicochemical properties
also reflcts signifiant associational relationships. The spatial and seasonal variation for the parameters studied in pre- and postmonsoon season has been discussed in detail in the paper. In regards to bacteriological contamination, 20 nos. of groundwater
samples were analysed for presence of total and fecal coliforms. Sample nos. 09, 10, 11, 20 represent very poor category while
Sample nos. 08, 15 represent poor category with presence of organic matter and bacteria. Thus 30% of the samples fall in the
vulnerable category. The study reveals that ~90 % of the study area lies in the ‘Excellent’ category with regards to availability
of groundwater for drinking purposes as per the Water Quality Index (WQI) classifiation. Thus, this study is helpful for proper
planning and management of available water resource for meeting drinking needs.
Keywords: Water Quality Index (WQI), Groundwater, Water Resource.
... Using data from an extensive fish survey of South African estuaries (Harrison et al. 2000), records from 191 estuaries were assessed. Nine non-native and/or translocated species were recorded, which comprised 6.5% of the total number of fish taxa recorded (138 species). ...
... In terms of numbers, non-native and/or translocated species comprised an average of 1.1% (range = 0.04-3.7%) of the total number of the fishes in five colonised cool temperate estuaries, 0.6% (range = 0.09-2.2%) of the total number of the fishes in eight colonised warm temperate estuaries, and 1.2% (range = 0.08-3.6%) of the total number of fishes in three colonised subtropical estuaries. Based on the 191 South African estuaries sampled, 257 779 fishes were captured, of which only 110 (0.04%) belonged to introduced or translocated species and were recorded in only 16 estuaries (Harrison et al. 2000). More recent updates on non-native and/or translocated fish show incidence and biomass to have increased, whereas relative abundance has remained more or less the same at very low levels (Van Niekerk et al. 2019a), perhaps an artefact of the numerical dominance of indigenous small Atherinidae and Clupeidae. ...
We review the possible impacts of non-native biota on the indigenous fishes of South African estuaries, including macrophytes, algae, pathogens, invertebrates, and fishes. Freshwater macrophytes are one of the primary non-native groups in the oligohaline reaches of some predominantly open estuaries, lake and river mouth type estuaries, as well as the entire area of certain low salinity, temporarily closed estuaries. Anoxia and hypoxia in the water column below Salvinia molesta and Pontederia crassipes floating mats have caused fish kills in certain temporarily closed estuaries. Mass mortalities of fish in estuaries have arisen from harmful algal blooms (HABs) and a catchment-derived pathogenic water mould, Aphanomyces invadans. Non-native invertebrate species in local estuaries are derived from freshwater, estuarine and marine sources. The freshwater gastropod Tarebia granifera has invaded many subtropical estuaries and may be negatively impacting their food webs, with estuarine zoobenthivorous fishes not appearing to consume this mollusc. The marine polychaete Ficopomatus enigmaticus has invaded many South African estuaries and, in some of them, changed the zoobenthic food web by encrusting on hard surfaces and filtering particulate matter from the water column. This species also does not appear to be eaten by zoobenthivorous fishes within these systems. No non-native marine or estuarine fish species have been recorded in South African estuaries but non-native freshwater fish species now occur in 25% of estuaries in the region. Degraded estuaries in particular are more vulnerable to colonisation by non-native and translocated fish species than unimpacted systems. During the 1990s, a fish survey of 191 estuaries revealed that only 0.04% of the catch comprised non-native or translocated species but this percentage has increased in many estuaries in recent decades. Non-native and translocated freshwater fish species have successfully colonised the oligohaline and mesohaline reaches of many systems and there may be an impact due to predation on the eggs and larvae of resident estuarine taxa and the recruitment success of catadromous and some estuarine-associated fish species. However, most non-native fishes have a limited tolerance for the salinity regimes found in the lower and middle reaches of many South African estuaries, with an even larger threat to the indigenous estuarine ichthyofauna coming from non-native plant, invertebrate and pathogen invaders. Based on this review, and other similar global studies, there is a developing paradigm that non-native invasions by fishes and other organisms into South African and global estuaries are driven primarily from freshwater taxa and not estuarine or marine species.
... A significant effort was made to ensure all rivers and streams with outlets to the sea were identified and to address systems omitted from historical lists (>400 outlets were evaluated). Datasets consulted included the CSIR NRIO list (1981) and those of Harrison et al. (2000), van Niekerk and Turpie (2012), Whitfield and Baliwe (2013), Bate et al. (2017), Dalu et al. (2018) and Human et al. (2018). Micro-system types, previously omitted from formal classification schemes, were also identified through the literature and using satellite imagery (GoogleEarth TM ) and aerial photographs (1930s to 2000s). ...
... Existing national and bioregional datasets were then scrutinised to establish what information was available on the physical features and processes of estuaries (e.g. size, mean annual runoff, mouth state) and biotic components (plants, invertebrates, fish and birds) to assist with classification (Harrison et al. (2000); van Niekerk and van Niekerk et al. 2015;van Niekerk et al. 2019d). ...
... Whitfield (1992) typed South Africa's estuaries into five types based on their physiographic (tidal prism, size), hydrographic (mouth state and mixing process) and salinity characteristics (Table 1). A geomorphological system used by Harrison et al. (2000) recognised six main types based on mouth condition (open or closed), size and the presence of a sand bar at the mouth (or inlet Does it support estuarine functionality and/or biota? Figure 1: Flow diagram of estuary classification process (van Niekerk and Turpie 2012) proposed a typing based on estuary size, mouth state, salinity structure and catchment type. This resulted in 46 ecosystem types, which included three estuary size classes (large >100 ha, medium 10-100 ha and small <10 ha). ...
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 biogeographicalzonation 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.
... The aMatikulu/Nyoni Estuary covers a surface area of 900 km 2 (Begg, 1978;Whitfield, 2000) with a mean depth of 1 m. The lower reaches of the aMatikulu/Nyoni Estuary are disturbed by agricultural activities but the fauna is generally in a good condition (Harrison et al., 2000). This estuarine system forms part of the aMatikulu Nature Reserve, managed by Ezemvelo KwaZulu-Natal Wildlife (EKZNW). ...
... A wide variety of anthropogenic factors have exerted pressures in the uMvoti (Begg, 1978;DWAF, 2004;MacKay et al., 2000;Turpie et al., 2002) Thukela ( O'Brien and Venter, 2012;O'Brien et al., 2018;Stryftombolas, 2008) and aMatikulu/Nyoni estuaries (Harrison et al., 2000). The anthropogenic impacts that are acting on these three estuaries, although exerting different intensities, include agriculture, industries, water abstraction, exotic plants, waste water treatment works, urban areas, informal settlements and recreational activities. ...
Effective environmental management and restoration of impacted estuaries in South Africa necessitates a holistic understanding of the contribution of various stressor-related impacts throughout the catchment. Ecological risk assessment for aquatic ecosystems is an important tool for water resource management. In this study, we describe results of a preliminary assessment that was conducted to evaluate the relative risks of multiple anthropogenic stressors currently acting within the catchments of uMvoti, Thukela and aMatikulu/Nyoni estuaries using Bayesian Network Relative Risk Model (BN-RRM) framework. Four socio-ecological endpoints selected for the present study included biodiversity habitat, safe environment, fisheries and productivity. We constructed a conceptual model which depicted potential and effect pathways from the source, to the stressor, to the habitat and to the endpoint. We also developed five scenarios (including historical and future scenarios) to predict the potential risk distributions in different proposed scenarios. Results revealed that productivity was the endpoint at the lower risk in all the estuaries and all scenarios except for scenario 5. Results also showed that scenario 3 which is a scenario before major resource development had the lowest risk scores for all the endpoints. Scenario 4 (year 2025 if no laws and management measures are implemented) had the highest risk scores for all the endpoints. Overall endpoints generally displayed low to medium risk throughout all scenarios (except scenario 3) and different flows. All endpoints generally displayed zero risk in scenario 3. All endpoints were at a highest risk in the uMvoti Estuary followed by aMatikulu/Nyoni and then Thukela Estuary. Results highlighted that in the uMvoti and Thukela estuaries, people were at a higher risk when compared with the ecological components of these systems as social endpoints displayed higher risk scores than the ecological endpoints, however the opposite was observed in the aMatikulu/Nyoni Estuary. This study provided the foundation for evaluating the risks of multiple stressors in the catchments of these estuaries to a variety of endpoints. Management options and research should focus on collecting necessary data and information to refine the developed RRM. By establishing such framework, we believe that stakeholders within the catchments of these systems together with government organisations will be able to make more informed and risk-based management decisions pertaining restoration and rehabilitation options for these three estuaries.
... For the purpose of the current study, these systems are broadly classified as 'microsystems', which are further subdivided into micro-estuaries and micro-outlets, depending on their characteristic physico-chemical conditions. Whitfield and Elliott (2011) provided a synthesis of global estuary types, whereas Harrison et al. (2000) classified South African estuaries, primarily based on differences in their geomorphology and hydrodynamics. However, micro-estuaries and micro-outlets are not included in any list of estuarine system types and, as such, the current study represents a foundation for additions to the list of currently known coastal systems. ...
Micro-estuaries and micro-outlets are very small coastal systems that share some biotic and abiotic characteristics with larger temporarily closed estuaries, but differ in that the former have small localized catchments and limited connectivity with the marine environment. This multidisciplinary study reviews the first comprehensive investigation into the ecological structure of a subset of southern African micro-estuaries and micro-outlets, elucidating the biotic and abiotic components that characterize these systems. Furthermore, the microsystems (which have an open water area of less than 5 ha and a depth of less than 1 m) are compared with larger estuarine systems in the region, with the former representing one end of a continuum ranging from micro-outlets to large estuarine lakes and bays. In terms of the abiotic regime, the micro-outlets were dominated by oligohaline or freshwater conditions, while the micro-estuaries were mostly mesohaline. Relatively few freshwater-associated microalgae, zooplankton, macrozoobenthos and fish taxa were present in the micro-outlets, while a richer combination of freshwater and estuary-associated taxa dominated the micro-estuaries. Due to their small size and limited periods of abiotic stability, microsystems only serve as intermediate nursery areas for 0+ juveniles of estuary-associated marine fish which, after less than a year, migrate to nearby larger estuarine systems in order to complete their juvenile life stages. When compared to temporarily closed estuaries, predominantly open estuaries, estuarine lakes and estuarine bays, microsystems are depauperate in terms of typical estuarine and marine biota. However, further research is recommended on microsystems in southern Africa and globally, in order to define in greater detail their physico-chemical and biological characteristics.
... There are sugar cane plantations upstream of the aMatikulu River. In the lower reaches, the estuary is disturbed by agricultural activities but the fauna generally remains in good condition (Harrison et al., 2000). The aMatikulu Estuary has a good ichthyofauna, water quality and aesthetics (Harrison et al., 2000). ...
... In the lower reaches, the estuary is disturbed by agricultural activities but the fauna generally remains in good condition (Harrison et al., 2000). The aMatikulu Estuary has a good ichthyofauna, water quality and aesthetics (Harrison et al., 2000). This system is described as a system that shares a common mouth and should be conserved as an item (Heydorn, 1986). ...
... In the current study some physico-chemical parameters between the three estuaries were highly variable. Although the three estuaries studied occur in the same geographical area and are geomorphologically similar (Harrison et al., 2000), the variability in water quality conditions can be attributed to different levels of human pressure on these systems. Lower temperatures recorded during low flow were associated with the winter season of South Africa where there is low rainfall and cold weather conditions. ...
Globally, estuaries are among the most productive ecosystems with many threatened by anthropogenic activities. Zooplankton is a bioindicator of ecosystem integrity. The spatial and temporal composition of zooplankton communities were quantified and compared within and between three estuaries (uMvoti, Thukela and aMatikulu/Nyoni estuaries) with different levels of human pressure in KwaZulu-Natal, South Africa. Additional effects of some physico-chemical variables and seasonal flow patterns to zooplankton community structuring were analyzed. The aMatikulu/Nyoni Estuary was selected as a reference site due to its good ecological state. Sampling dates represented high flow (March and April) and low flow (August and September) from 2014 to 2016. Following aMatikulu/Nyoni, highest abundance was recorded in Thukela and then uMvoti Estuary with copepod Pseudodiaptomus hessei and Acartia natalensis dominating the three estuaries. Highest abundance was recorded during low flow in the uMvoti and Thukela estuaries. Redundancy analysis revealed higher salinity and oxygen as environmental determinants of zooplankton community structure in the aMatikulu/Nyoni while turbidity and pH were the determinants of zooplankton community structures in uMvoti and Thukela estuaries. Elevated concentrations of DIN in the Thukela Estuary during high flow identifies the Thukela River as an important source of nitrogen to this estuary. Our findings suggest that these estuaries be managed to ensure sufficient freshwater supply which controls primary production. Although the three estuaries were from the same biogeographical region with a similar river dominated function, high variability in their zooplankton communities could be explained by differing water quality due to differing human pressure in their catchments. © 2019 European Regional Centre for Ecohydrology of the Polish Academy of Sciences
... Early toxic effects of pollution may be evident at cellular or tissue level before significant changes can be observed in fish behaviour or external appearance [6] . Biological communities can integrate the effect of changes in chemical, physical and biological factors of environment and hence, are good indicators of ecosystem health [7] . Physiological state of an organism is a key factor in determining species sustainability, survival and availability because this factor is susceptible to the effects of pollutants at all stages of an organism life cycle [8] . ...
The unregulated discharge of untreated municipal sewage water to the natural water bodies is a major threat to the aquatic ecosystems. In the present study, the fingerlings of Labeo rohita were exposed to treated sewage water and 1/10 th of LC50 and 1/20 th of LC50 of untreated sewage water (UT) obtained from sewage water treatment plant, Ludhiana, India. After determining 96 hr LC50 value of UT, fingerlings were divided into four groups: control, treated, 1/10 th of LC50 and 1/20 th of LC50 UT and exposed for the period of two months. The oxidative stress parameters viz. proteins, lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) were examined in the liver of fingerlings. Results of this study revealed a significant decrease (p≤0.05) in the levels of proteins and the activity of SOD and GPx in 1/10 th LC50 and 1/20 th LC50 UT groups, however, the activity of LPO, CAT, GR and GST was found to increase significantly (p≤0.05) in 1/10 th LC50 and 1/20 th LC50 UT groups in comparison to control and treated group. Hence, the study concluded that untreated sewage water has a potential to alter the activity of antioxidant enzymes in liver, however, clean and treated water can restore the activity of these enzymes in fish.
... Whitfield and Elliott (2011) gave a detailed synthesis on present-day classification of the various estuaries and coastal systems found across the world, while Harrison et al. (2000) classified South African estuaries primarily based on differences in their geomorphology. ...
South Africa has more than 200 Temporarily Open/Closed Estuaries (TOCEs) along its approximately 3000 km coastline. In addition, there are approximately 200 micro-estuaries and micro-outlets on the subcontinent, many of which share some of the characteristics with TOCEs but differ in that they are supplied by localised coastal stream catchments with a more limited supply of freshwater and less connectivity to the marine environment. Between 2015 and 2016, this study endeavoured to investigate the physico-chemical properties, microalgal dynamics as well as the seasonal species abundance and composition of aquatic invertebrates and fishes in four micro-estuaries and four micro-outlets along the warm-temperate section of the Eastern Cape coast.
The micro-outlets were dominated by oligohaline or freshwater conditions, while the micro-estuaries were mostly mesohaline. Microalgal biomass in these systems was influenced by temperature, nutrient conditions and light availability. Chironomidae and Ephemeroptera dominated benthic macro-invertebrate communities in the micro-outlets, while Amphipoda and Mysida were most dominant in micro-estuaries. Copepoda and Amphipoda dominated the zooplankton assemblages in both system types. Nekton communities in micro-outlets were dominated by juvenile Myxus capensis and tadpoles (mostly Xenopus laevis), while Oreochromis mossambicus, Gilchristella aestuaria, M. capensis and Mugil cephalus were the four most common species in the micro-estuaries.
Seasonal variations in physico-chemical parameters and community composition of both the nekton and invertebrates were recorded during this study. Micro-estuaries and micro-outlets exhibited relatively lower diversity and abundances of biota than TOCEs. Furthermore, the micro-estuaries have a low estuarine function when compared to TOCEs, while the micro-outlets have very limited estuarine characteristics and were dominated by freshwater biota. The micro-systems are smaller in size and contain lower proportions of estuary-associated taxa when compared to larger estuarine systems such as TOCEs and permanently open estuaries. The results of this study confirm that there are distinctions between the biota of the two micro-system types, thus making biotic assemblages, together with physico-chemical parameters, a viable tool for differentiating between micro-estuaries and micro-outlets.
This study represents the first investigation into the ecological functioning of micro-estuaries and micro-outlets. As a whole, micro-systems serve as nursery areas for freshwater-associated invertebrate taxa. Due to their limited periods of stability, micro-estuaries serve as intermediate nursery areas for 0+ juveniles of estuary-associated marine fish which, after less than a year, then migrate to larger estuarine systems located nearby. The small catchment size and short period of stability in these systems heightens their level of sensitivity to water flow alterations through dams, direct water abstraction, afforestation and watercourse diversion, while their lower buffering capacity makes them more susceptible to pollution and nutrient inputs from intensive agricultural activities and urban expansion.
... There are approximately 370 outlets to the sea along the South African coastline (Harrison et al. 2000), approximately 300 of which can be regarded as functional estuaries (Van Niekerk and Turpie 2012). Only 71 of these estuaries currently enjoy any form of formal protectedarea status (Van Niekerk and Turpie 2012), of which many are only partially protected (Whitfield 1998;Van Niekerk and Turpie 2012). ...
The Palmiet Estuary is a small, rural estuary in the Western Cape that only closes briefly during dry summers. The system was previously surveyed during 1979 to 1980 and we repeated the survey in April 2015 (mouth closed) and September 2015 (mouth open). Salinity, temperature, pH and oxygen saturation were measured, and invertebrate and fish faunas surveyed. Physico-chemical characteristics have undergone little directional change, apart from an apparent increase in pH, possibly as a result of changes in land use and application of fertilisers and pesticides in the catchment. Invertebrate species richness increased from 31 to 40 species, despite lower sampling effort in 2015. Most changes were among rare species, or were readily explained by changes in mouth condition and water chemistry. We also confirmed a substantial range extension of the tropical crab, Varuna litterata, rediscovered the locally endemic amphipod, Quadrivisio aviceps, and reported several new distribution records. Gastropods had virtually disappeared from the system, whereas the previously unreported bivalve, Brachidontes virgilae, had become abundant. Overall, fish diversity dropped from 19 to 11 species, but this can largely be ascribed to differ- ences in sampling frequency, season and mouth state. Comparisons of samples from like months showed the fish assemblage to have remained fairly stable, despite changes in inflowing water chemistry and infection of fish by the pathogenic water mould, Aphanomyces invadans. Bird abundance and diversity increased substantially. No alien invertebrate or fish species were recorded. Accordingly, in marked contrast to other smaller estuaries in the region, the Palmiet Estuary has remains in relatively good condition.
