Several studies regarding the effects of excess nutrients and metals as possible causes of deformities found in diatom cells have been conducted in Europe, North America and Australia. This is the first study in South Africa which catalogued and analysed diatom deformities in detail. We assessed diatom deformities in response to a large water chemistry dataset, including pH, electrical conductivity, alkalinity, hardness, nutrients, heavy metals and radioactive elements. The freshwaters of the Karoo exhibited wide ranges in many of their environmental variables. Diatom deformities were categorised into four types (outline, raphe, striation and mixed/other), and each cell measured and photographed. Correlations and multivariate analyses between environmental variables and deformity type, as well as diatom species, were performed. A cumulative criterion unit (CCU) ratio, using South African aquatic ecosystem limits, was calculated for Al, Cd, Cu, Mn, Pb, Se and Zn to determine if the combined effect of these metals exerted any influence on the cause of deformities. No single stressor could be linked to the deformities. Instead, variables showing to be most probable to exert an influence are electrical conductivity, oxidised nitrogen, sulphate and lithium, with selenium and strontium having a lesser influence. The CCU application did not yield expected results. This could be due to the naturally highly mineralised water found in the Karoo.

The environmental risks from shale gas extraction through the unconventional method of 'fracking' are considerable and impact on water supplies below and above ground. Since 2010 the recovery of natural shale gas through fracking has been proposed in parts of the fragile semi-arid ecosystems that make up the Karoo biome in South Africa. These unique ecosystems are heavily reliant on underground water, intermittent and ephemeral springs, which are at great risk of contamination by fracking processes. Diatoms are present in all water bodies and reflect aspects of the environment in which they are located. As the possibility of fracking has not been removed, the aim of the project was to determine if diatoms could be used for rapid biomonitoring of underground and surface waters in the Karoo. Over a period of 24 months, water samples and diatom species were collected simultaneously from 65 sites. A total of 388 diatom taxa were identified from 290 samples with seasonal and substrate variation affecting species composition but not the environmental information. Species diversity information, on the other hand, often varied significantly between substrates within a single sample. Analysis using CCA established that the diatom composition was affected by lithium, oxidized nitrogen, electrical conductivity, and sulphate levels in the sampled water. We conclude that changes in diatom community composition in the Karoo do reflect the water chemistry and could be useful as bioindicators.& COPY; 2023 SAAB. Published by Elsevier B.V. All rights reserved.

This paper examines the efficacy of diatoms as bioindicators of water quality in the upper reaches of the Great Fish River following a period of reduced flow from drought conditions. Of the five sites, three were sampled three times in an 18 month period while the remaining two were sampled once. As a comparison, one headwater site within Mountain Zebra National Park, situated in the same district, was sampled. A total of 166 diatom taxa belonging to 29 genera were identified. Dominant taxa for the Great Fish River were identified as Amphora pediculus; Epithemia sorex; Nitzschia frustulum; Navicula veneta and Craticula buderi. These species, indicative of high nutrient concentrations and moderately saline to brackish conditions can tolerate low flow conditions. The Generic Diatom Index (GDI), the Specific Pollution sensitivity Index (SPI) the Biological Diatom Index (BDI) and the% Pollution Tolerant Valves (%PTV) - part of the UK Trophic Diatom Index (TDI) were used for interpretation of the results. The indices showed that this river is in poor condition. By comparison the headwater site in the Mountain Zebra National Park had Cocconeis placentula var. euglypta, Achnanthidium minutissimum and Cocconeis placentula var. lineata as dominant species and, using the same indices, the river was classified as in moderate to good condition with respect to water quality. When compared to a previous study (2010 - 2012), these sites showed a shift in dominant species indicating a change in water flow conditions and quality.

The plant species play very important role as they are not just planted to make the streets look beautiful but are a vital part of the ecosystem. They are a major source of the oxygen, help control, stabilise the climate and feed animals. The choice of planting alien trees instead of indigenous trees on the street was a big mistake. Therefore there is a need to pay attention on it now that there is high growth of urbanisation. This research has the primary objectives to investigate the plant species diversity, density, abundance and distribution in the Grahamstown streets and identify the key challenges faced by local forestry officials concerned with the provision of street trees. Streets were randomly sampled in the Grahamstown area. A total of 1467 plants were sighted in 17 streets comprising of only 15 indigenous species and 20 alien species. This means the 57% of trees were alien species and only 43% of the trees were indigenous. Significant differences in tree density and species richness were evident across suburbs (Grahamstown West), differences being more significantly different in the more affluent suburbs and poorly represented in the township (Grahamstown East area). Keywords: Plant species diversity, abundance and distribution

Seedlings of woody canopy species in the xeric forms of subtropical thicket are rare. Here we argue that the low number of seedlings is a consequence of niche conservatism where thicket species have retained germination and seedling establishment requirements associated with their ancestral origins in the warm, wet forests of the early Cenozoic. We test this hypothesis by evaluating the germination success of 12 arid and valley thicket species – representing a range of growth forms and dispersal modes – using a factorial germination experiment that sought to simulate permanently moist and deeply-shaded conditions (i.e. a wet forest environment) and sparsely-shaded and intermittently dry conditions (i.e. open microsites during the rainy season) in contemporary thicket environments. Germination success was significantly higher under the more mesic soil-moisture conditions for all species except Pappea capensis and Jatropha capensis. These results suggest that germination of thicket species requires long periods of high soil moisture supporting the niche conservatism hypothesis.

A substantial portion of the Thicket Biome in the Eastern Cape has been transformed by overgrazing. An experimental rehabilitation study of degraded succulent thicket was initiated to determine whether increasing the patchiness on the landscape would result in an increase in soil resources. Five types of treatments were used for the rehabilitation trials, namely: piles of black rhinoceros (Diceros bicornis) dung placed so as to mimic rhino latrines; Portulacaria afra brushpiles; brushpiles of woody Thicket species; brushpiles of woody Thicket species over-sown with seed; and the control (area left unchanged). Measurement occurred before and three years after treatment and change was related to an untransformed reference site. All of the treatments did increase the litter in the patches, which resulted in an increase in soil organic content especially in the top 3cm of soil. All of the rehabilitation patches were successful in accumulating basic elements (pH and electrical conductivity results) as well as available phosphorus. The dung treatment had the greatest effect on the soil resources underneath and surrounding the patches. The dung treatment significantly increased the electrical conductivity as well as the available phosphorus and available organic nitrogen. The rehabilitation trial has shown that by increasing the patchiness of degraded areas in succulent thicket it is possible to initiate "islands of fertility".

The opencast extraction of limestone at the PPC Cement (Pty) Ltd Loerie quarry in the Eastern Cape, South Africa, has led to disturbance of the immediate environment. Large tracts of thicket have been removed during mining and exhausted quarry areas had to be revegetated. Revegetation commenced 16 years ago and as a result of progressive revegetation efforts since then, five seral stages were available for study. This presented an opportunity to describe the successional progression that occurs where thicket topsoil was used for revegetation. The quarry lies near the Gamtoos fault and both thicket and mountain fynbos is found in proximity to the mine. Before mining, the area was covered by thicket and quarry floors were revegetated by covering landscaped areas with thicket topsoil. The vegetation that developed in the quarry had a very low floristic relationship to fynbos. After 16 years, the vegetation also had a low similarity to thicket, even though the soils used for revegetation contained thicket propagules. The oldest seral stage (16 years) was a Rhus incisa-Panicum deustum thicket in which only 46% of the species were mature thicket species. In order to develop thicket more rapidly, active intervention will be required. This could take the form of planting of saplings of key thicket species. A trial planting of such saplings showed high survival success of most species. Long-term (50 year) monitoring will be required to determine whether this approach was successful.

A small artificial wetland was constructed through which intake water flowed before entering the initial pond of a solar saltworks. This trial wetland was designed for the removal of excessive nutrients from the water as the system is becoming hypertrophic. Spartina maritima (Curtis) Fernald was the dominant halophytic grass used in the wetland and Ulva rigida C. Agardh the dominant macroalga. The nutrient content of the inflow and outflow water of the wetland was monitored for eight months after construction. For seven out of nine analyses, the ammonium concentrations of water flowing out of the wetland were significantly reduced (by an average of 56%) when compared to those measured in water flowing into the wetland. Nitrate and phosphate concentrations for eight out of nine analyses also showed significant reductions (by 60% and 56% respectively). The success of this wetland indicates that it can be an effective management tool for nutrient reduction in solar saltworks.

Seedling recruitment of the Eastern Cape endemics Cyclopia longifolia J.R.T. Vogel and Cyclopia pubescens Eckl. & Zeyh. was analysed after fire. Cyclopia longifolia seedling recruitment after treatments of fire; cleared and smoked; and cleared only was comparatively low; recruitment of 2.8 (after 10 weeks) to 3.8 seedlings (after 13 months) per adult was recorded. Cyclopia longifolia was found to be a resprouter as well as seeder. A population of Cyclopia pubescens was exposed to a veld-fire, with a resultant recruitment of 61 seedlings (5 months after burn) to 227 seedlings (17 months after burn) per adult. The difference in recruitment success can be ascribed, in part, to environmental conditions that strongly influenced seed germination and seedling survival. Cyclopia longifolia preferentially allocates its resources to regeneration rather than reproduction.

Groundwater levels in the slacks of the Alexandria dune field were monitored over a 14 d spring-to-neap tidal cycle. During this period water level at the seaward end of the slacks rose and fell in relation to the spring-to-neap tidal heights. The levels at the back of the slack fluctuated much less than in the front. This resulted in a change in the slope of the water table between spring and neap tides. During neap tide, the difference in water table height was 133 mm between the seaward and landward ends of the slack (a distance of 110 m), while just after spring tide the difference was only 54 mm. This means that groundwater is discharged in a pulsing fashion from the aquifer into the surf-zone. releasing nutrient-rich water at a rate of 0.157 m(3) d(-1).m(-1) (spring tide) and 0.328 m(-3).d(-1).m(-1) (neap tide). The daily tidal cycle influences the groundwater mainly around spring tide and mostly at the seaward side of the slack. The influence extends for a distance of 325 m from the mean shoreline. A 20% change in flow was calculated between low and high spring tides and only 6% change between low and high neap tides. Groundwater provides 2.6 g N.d(-1) at spring tide and 5.6 g N.d(-1) at neap tide for every running metre of beach on average. This gives rise to a pulsing of nitrogen availability with twice as much nitrogen entering the surf-zone at neap tide compared to that at spring tide. This nitrogen is an important source of this element to the surf diatom Anaulus australis Drebes et Schulz.

A survey of the southern African coastline from the Kunene River in the north-west to Kosi Bay in the northeast showed that five coastal features are associated with diatom accumulations that turn surf-zone water brown. Accumulations are only found on sandy beaches with wide surf-zones; medium to high energy surf conditions; well-developed rip currents and adjacent to coastal dunes with nutrient-rich aquifers. These physical features are common to beaches where surf diatom accumulations have been reported. The absence of one of these features was concomitant with the absence of concentrations of surf diatoms turning the water brown. An exhaustive list of South African beaches where surf diatom accumulations have been recorded is provided.

Surf diatoms regularly cause brown water discoloration at suitable beaches in the southern hemisphere as well as a few beaches of North and Central America. Species involved are taxonomically and morphologically unrelated. Different localities usually have one or two species dominant in the brown water, but up to five species have been found to be co-dominant. There is no global pattern of species distribution other than that the phenomenon is more common in the southern hemisphere. Anaulus australis Drebes et Schulz is restricted to the southern hemisphere; Asterionella socialis Lewin et Norris is endemic to the northern hemisphere while Aulacodiscus africanus Cottam appears to be a tropical species. The remainder of the surf accumulating diatoms (Attheya armatus (West) Crawford, Aulacodiscus kittonii Arnott, and Asterionellopsis glacialis (Castracane) Round) occur in both hemispheres. Records from the tropics show that the original biogeographic limits previously set at between 29 degrees S and 42 degrees S are too narrow. Most surf diatoms are confined to surf-zones, never being recorded elsewhere (A. armatus, A. australis, A. kittonii and A. socialis) but at least one is a cosmopolitan species (A. glacialis). Accumulations form at fixed localities of the coastline and are semi-permanent features of the sandy beaches where they are found. The coastal features at the beaches where they have been recorded are similar.

Several South African beaches have high nutrient loads, both as point sources and as seepage from freshwater aquifers that are located just behind beach foredunes. While point sources may have nitrogen loads up to 100 times higher than that of nonpolluted sea water, the seepage water appears to contribute more: to the increased nutrient loading of the surf-zone. Anaulus australis Drebes et Schulz accumulates to high cell concentrations in several of the surf-zones of South Africa. The accumulations colour the water brown if the conditions are suitable. All sandy beaches longer than 5 km, including the highly polluted False Bay beaches, south-western coast of South Africa, were investigated in this study. Nutrient inputs and phytoplankton standing stocks were measured at each site. A correlation between several environmental variables and phytoplankton biomass showed that the higher the total inorganic nitrogen input from groundwater, the higher the biomass. Eutrophication, while not causing accumulations of A. australis, can be considered to change the natural dynamics of this surf diatom resulting in elevated standing biomass. At sandy beaches where human impacts are minimal, large coastal aquifers can provide nitrogen to maintain a biomass level proportional to the magnitude of the nutrient supply. While surf energy is the major driving force controlling the presence or absence of surf diatoms, nutrients may well control their standing stocks.