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Ecological restorations of reservoirs are implemented worldwide; however, minimal successes are reported and understood for warmer African lakes like Swakoppoort Dam, Namibia. The objectives of the study were (a) to establish the effectiveness of the two control measures in reducing cyanobacteria growths in comparison with untreated control areas and (b) to compare the results generated before and after control measures with the reference Von Bach Dam. During Phoslock® treatment, the average cyanobacteria cells and total phosphate (TP) were 90,521 cells/ml and 0.3 mg/L in the treated area and 55,338 cells/ml and 0.1 mg/L in the control area. During Solar Powered Circulation (SPC) treatment, the average cyanobacteria cells were on average 906,420 cells/ml in the treated areas and 121,891 cells/ml in the control area. The TP on average was 0.3 mg/L during SPC treatment, while during the combined treatment, the average cyanobacteria cells, TP, and total nitrogen (TN) were 18,387,226 cells/ml, 0.27 mg/L, and 2.41 mg/L before and 22,836,511 cells/ml, 0.42 mg/L, and 1.50 mg/L after treatment. This was higher compared to the reference site. PCA triplot indicates no grouping pattern, and the repeated-measures mixed model analyses indicate that treatment had no significant effect on cyanobacteria cells. It was evident that the two control measures were ineffective in reducing cyanobacterial cells. PRACTITIONER POINTS: Key findings of the article: Two phytoplankton control measures were found ineffective to reduce the cyanobacterial cell numbers. High cell numbers of cyanobacteria were recorded at the treatment areas compared to untreated control areas during both treatments. The combined effect of the two control measures was ineffective as more cyanobacterial cells were recorded during the treatment. During control measure treatment, the Swakoppoort Dam was hypertrophic, which could be due to a malfunctioned WWTP upstream. The inefficiency of the control measures could be due to small treatment area, higher nutrients, or treatment period. The implications of the results to water/wastewater practice: The selection of appropriate mitigation measures considering treatment area for dams with high nutrient situated in warmer arid environments. There is a need to understand the trophic relationships, climatic conditions, and the sources of the internal and external nutrients to manage water quality. Focus on point and non-point sources of nutrients as the root causes of the degradation of Swakoppoort Dam water.

Thyroid hormones play critical roles in body growth and development as well as reproduction. They also influence the activities of a wider variety of tissues and biological functions, such as osmoregulation, metabolism, and especially metamorphosis in organisms, such as frogs. These complex activities of thyroid hormones are prone to disruption by agricultural pesticides, often leading to modulation of growth and the reproductive system in particular. These substances include Glufosinate ammonium, Glyphosates, Imazapyr, Penoxsulam, and Diquat dibromide among other herbicides. In this study, the standardized Xenopus Metamorphosis Assay protocol was used to assess the potential thyroid-modulatory properties of the Glufosinate ammonium Basta formulation, at relevant environmental concentrations (0.05 mg/L, 0.15 mg/L, and 0.25 mg/L) for 21 days. The results showed that this formulation only reduced the hind-limb length among the morphological endpoints. Histological evaluation showed that the mean thyroid gland area and the mean thyroidal follicle epithelium height were significantly increased following 0.15 and 0.25 mg/L exposures. The present study confirmed that this Basta formulation interacts with the thyroid axis and therefore potentially pose health hazard to amphibian in particular and potentially metamorphic aquatic vertebrates. Furthermore, the result is a signal of inherent potential thyroid disrupting activities that must be further investigated and characterised in some of the aquatic herbicide formulations to safeguard the aquatic biodiversity.

Toxic phytoplankton in the aquatic ecosystems are dynamic, affecting water quality. It remains unclear as to how possible toxic phytoplankton assemblages vary vertically and temporally in Swakoppoort and Von Bach dams, located in a dry subtropical desert region in central Namibia. The following variables were analyzed: pH, Secchi depths, turbidity, water temperature, total phosphorus, orthophosphate, chlorophyll-a, phytoplankton cells, and water depths. Cyanobacteria dominated the phytoplankton community in the autumn, winter and spring (dry) and summer (wet) seasons, at all the depth ranges in both dams. Microcystis dominated the vertical and temporal dynamics, followed by Dolichospermum. In the dry seasons, higher cyanobacteria cell numbers were observed in comparison to the rainy season in both dams. Spring blooms of cyanobacteria were evident in the Von Bach Dam while autumn and spring cyanobacteria blooms were observed in the Swakoppoort Dam. In the Swakoppoort Dam, the preferable depth ranges for toxic cyanobacteria species were at 5 to 10 m while in the Von Bach Dam at 0 to 5 m range. The findings of the current study indicate that the traditional selective withdrawal of water in the two dams should be performed with vertical and temporal dynamics of possible toxic cyanobacteria accounted for to aid the abstraction of water with the lowest possible toxic phytoplankton numbers, which could lower the public health risk.

Knowledge regarding the potential impacts of crude oil on endocrine signalling in freshwater aquatic vertebrates is limited. In this study, the expression of selected genes as biomarkers for altered endocrine signalling were studied in African clawed frog, Xenopus laevis tadpoles, and juvenile Mozambique tilapia, Oreochromis mossambicus exposed to weathered bunker and un-weathered refinery crude oil water accommodated fractions (WAFs). In addition, the expression of the aforementioned genes was quantified in X. laevis tadpoles exposed to surface water collected from the proximity of an underground oil bunker. The (anti)estrogenicity and (anti)androgenicity of crude oil, crude oil WAFs and surface water were furthermore evaluated using recombinant yeast. Thyroid hormone receptor beta expression was significantly downregulated in X. laevis in response to both oil WAF types, whereas, a further thyroid linked gene, type 2 deiodinase was upregulated in O. mossambicus exposed to a high concentration of bunker oil WAF. In addition, both WAFs altered the expression of the adipogenesis-linked peroxisome proliferator-activated receptor gamma in X. laevis. The crude oil and WAFs exhibited anti-estrogenic and anti-androgenic activity in vitro. However, O. mossambicus androgen receptor 2 was the only gene, representing the reproductive system, significantly affected by WAF exposure. Estrogenicity, anti-estrogenicity and anti-androgenicity were detected in surface water samples; however, no significant changes were observed in the expression of any of the genes evaluated in X. laevis exposed to surface water. The responses varied among the two model organisms used, as well as among the two types of crude oil. Nonetheless, our data provide evidence that crude oil pollution may lead to adverse health effects in freshwater fish and amphibians due to altered endocrine signalling. This article is protected by copyright. All rights reserved

The emergence of widespread morphological malformations in the reproductive system of wildlife is generating increasing concerns. This concern is because the observed malformities may be linked to pollution by pesticides and other chemicals. The amphibian declines, for example, have been linked to pesticide pollution among other factors. Using an extended Xenopus Metamorphosis Assay protocol, until the tadpoles metamorphosized, the exposure impacts of three glyphosate formulations, namely, Roundup, Kilo Max and Enviro Glyphosate, were assessed on the reproductive system of Xenopus laevis, vis-a-vis the body mass, sex ratios and morphological malformations as endpoints. The exposure concentrations ranged between 0.2–0.6 mg/L, 0.9–28 mg/L and 90–280 mg/L for Roundup, Enviro Glyphosate, and Kilo Max, respectively. Both Kilo Max and Enviro Glyphosate formulations significantly reduced the body mass of the metamorphs compared to the control. In sex ratios, only Kilo Max altered the percentage sex ratio of the treated frogs at a ratio of 68:32 (F:M) compared to 50:50 ratio in the control. In reproductive malformations, the three formulations showed abnormality index range of 22.3–49%, 17.5–37.5% and 20–30% for the Kilo Max, Enviro Glyphosate and Roundup formulations, respectively, compared to 7.5% in the control. Observed reproductive malformations include mixed sex, translucence, aplasia, segmented hypertrophy and segmented aplasia and translucence. This result indicates that some of the glyphosate formulations have the capacity to cause widespread reproductive malformations in a way that could reduce the reproductive fitness of the amphibian. Care must therefore be taken to reduce the application rate of these formulations, particularly in aquatic environments.

Ample evidence around the world exists suggesting a link between exposure to glyphosate, toxicity and perturbed physiological functions in non-target organisms. Although glyphosate formulations are widely used for weed and alien plant management, their ecotoxicological information remain scanty. Using the 96-hour Frog Embryo Teratogenesis Assay-Xenopus protocol, embryotoxicity and teratogenicity of three glyphosate-based formulations were assessed. Embryos of Xenopus laevis were exposed to Roundup, Kilo Max and Enviro Glyphosate at concentration of 0.3-1.3, 130-280 and 320-560 mg acid equivalent (a.e.)/L respectively. The results showed Roundup to be more toxic than the other formulations with a 96-hour LC50 of 1.05 mg a.e/L. compared with 207 mg a.e./L, and 466 mg a.e./L for Kilo Max and Enviro Glyphosate respectively. Although, both Roundup and Kilo Max formulations show inhibition on growth of the embryo-larva (P ˂ .05), the minimum concentration inhibiting growth ratios of the three formulations was >0.30 baseline, indicating no significant growth inhibiting effect in the formulations. For teratogenicity, Roundup and Enviro Glyphosate formulations exhibited increasing teratogenic traces, with the teratogenic index at 1.7 and 1.6 respectively. Kilo Max formulation shows low teratogenicity with the teratogenic index at 1.4. Characteristic malformation induced by these formulations included generalized edema, cardiac and abdominal edema, improper gut formation and axial malformations. This study confirms that these formulations could be a potential physiological and ecological health disruptor, particularly concerning teratogenicity and growth disruption. Further studies to characterize the contributions of their surfactants will be invaluable.