African Journal of Aquatic Science

A bibliometric study on diatom DNA metabarcording for water quality monitoring: a global perspective

Tue, 23 Jan 2024 00:00:00 +0000

Aquatic biota have been used for decades in water quality assessment since they reflect the changing physico-chemical conditions of waterbodies. Among the aquatic organisms used in biological assessment are diatoms. Initially, morphological studies of diatoms were preferred in monitoring but today the new technique of diatom DNA metabarcoding is gaining preference. This study aimed at (1) summarising the thematic study areas on diatom DNA metabarcoding for water quality monitoring, (2) identification of past and future trends of research on diatom DNA metabarcoding for water quality monitoring, and (3) determination of regional and institutional trends in studies involving diatom DNA metabarcoding for water quality monitoring. We obtained data from the Web of Science (WoS) using research queries like “Diatoms DNA metabarcoding for water quality monitoring”, “Diatoms DNA metabarcoding for water quality biomonitoring”, and “Diatoms DNA sequencing for water quality monitoring”. We identified 127 articles that had published on diatoms DNA metabarcoding in water quality monitoring between the years 2003 and 2022. Our study revealed that the developed nations, led by France, followed by Germany and USA, dominated the research areas involving the use of diatoms DNA metabarcoding in water quality monitoring. Additionally, our present study showed that DNA metabarcoding was related to biodiversity assessment, rbcL, species identification and taxonomy, a finding which is in line with previous studies conducted recently that have revealed that DNA-based approaches, for example the use of rbcL genes, are more effective in the determination of diatom community structures compared to morphological methods. Although DNA metabarcoding is rapidly gaining popularity in water biomonitoring, there are biases when explaining the differences between morphological and molecular based diatom indices, among them the incompleteness of the reference library such as R-syst::diatom database. To address this disparity, there is need to use environmental sequences from high- throughput sequencing (HTS) runs which can subsequently be related to morphological observations, followed by integration of the same into the reference libraries after setting up several guidelines and quality criteria. Consequently, the findings of this study present insights that will contribute globally to the development of water quality monitoring frameworks using diatoms.

South African coastal outlets and estuaries: what defines an estuary versus an outlet?

Alan K. Whitfield — Tue, 23 Jan 2024 00:00:00 +0000

This review examines the transition of coastal micro-outlets to micro-estuaries, to fully functional and species rich estuaries of various types. The definitions of the different types of microsystems are reviewed and it is apparent that an estuary is not simply a coastal water body where river and seawater meet. A range of other conditions, especially regular marine-estuarine connectivity and the persistence of a relatively large waterbody, are required for a flourishing estuarine biota to become established. In contrast to many global countries, the South African coastline has a continuum of coastal microsystems that cover the full spectrum of micro-outlets of various sizes, through micro-estuaries in the process of becoming estuarine systems, to a range of fully functional estuaries such as temporarily open/closed and predominantly open estuaries, to large estuarine lakes and bays. The impact of sea-level rise and fall on the exposure or inundation of coastal waterfalls is also examined, thus providing additional insights into the transformation of a freshwater outlet into a functional estuary. Furthermore, the creation of artificial concrete canal outlets in some of the major coastal cities is documented, with some estuaries being lost in the process.

Water quality monitoring and measuring physicochemical parameters using wireless sensor networks

N. Satyanarayana Murthy, S.F. Ahamed — Tue, 23 Jan 2024 00:00:00 +0000

In a world grappling with the dire consequences of poor sanitation and inadequate water conditions, there is an urgent need for a comprehensive solution. The staggering statistics of over 400 million affected cases and 15–25 million lives lost worldwide underscore the gravity of the situation. This paper addresses this critical issue by introducing a novel approach to water quality monitoring that leverages wireless sensor networks. Traditional monitoring techniques have proven inefficient in combating the proactive contamination of water sources. These methods often involve the cumbersome grouping of various points within the distribution network, resulting in delayed outcomes, labour-intensive processes and a lack of real-time data. To overcome these limitations, this study presents a paradigm shift by employing wireless sensor networks as a viable alternative. Our proposed system boosts capability to measure a range of physicochemical parameters linked to water quality, including reductions in potential, conductivity, pH level, temperature and flow rate. By scrutinising these parameters, our sensors effectively detect water contaminants, enabling a proactive response to potential threats. To achieve this, we have meticulously designed and implemented sensors equipped with signal conditioning circuits. These sensors are seamlessly integrated into a network, with each node connected to a microcontroller responsible for data analysis and processing. This integration ensures real-time monitoring, the rapid detection of water quality deviations and swift response mechanisms.

Analysis of freshwater diatom deformities in the Karoo, South Africa

M. Holmes, E.E. Campbell, M. de Wit, J.C. Taylor — Tue, 23 Jan 2024 00:00:00 +0000

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.

Effect of abattoir activities on the quality of water and surrounding soil of the Anwai River in Asaba, Nigeria

O.T. Fatunsin, I.G. Enenya, P. Ebomese — Tue, 23 Jan 2024 00:00:00 +0000

The Anwai River is the most important river in Asaba, Nigeria, because of its many uses, and these include abattoir activities. The aim of this study was to assess the surface water and surrounding soil of the Anwai River for the effects of abattoir activities during the wet and dry seasons of 2020. The quality of soil and water samples was analysed using standard procedures as set by the American Public Health Association. Results of water analyses showed that pH, total dissolved solids and total suspended solids varied from 6.45 to 6.67, 13.50 mg L⁻¹ to 24.42 mg L⁻¹, and 2.19 ± 0.04 mg L⁻¹ to 10.79 mg L⁻¹, respectively. Soil pH, total organic content, Pd and Cr had a range of 5.83 to 7.65 pH units, 0.15 to 2.74%, 1.88 ± 0.03 to 22.8 ± 0.28 mg kg⁻¹, and 0.86 ± 0.03 to 4.87 ± 0.04 mg kg⁻¹, respectively. There were significant differences between Upstream, Midstream (by the abattoir) and Downstream samples; however, there were no significant differences between dry and wet season results for most of the parameters. Midstream values for the water quality index were 104.89 and 119.34 in the dry and wet seasons, respectively, which showed that the Midstream water samples were poor. The findings of this study showed that the abattoir activities were negatively impacting river water and soil quality.

Validation of the generic name Prescottiella gen. nov. (Desmidiales, Zygnematophyceae): a rare African desmid

Sanet Janse van Vuuren, Anatoliy Levanets — Tue, 23 Jan 2024 00:00:00 +0000

Prescottiella sudanensis is a rare, asymmetrical desmid currently known from only a few countries in equatorial Africa. During the present study, P. sudanensis cells were found in water samples from Vogel Pan located in the far north-eastern side of Namibia, thereby expanding the known geographical distribution of the species. The location of the sampling site, which is situated in a direct line halfway between the Makgadikgadi pans and Okavango Delta towards the east (Botswana) and the Etosha pans towards the west (Namibia), suggests that migrating birds are likely vectors spreading desmids from one waterbody to another. In this paper a morphological description (including dimensions) and micrographs of P. sudanensis are presented, and the known geographical distribution of the species is discussed in relation to migration routes of birds. As the genus and species names are invalid according to ICN Art. 40.1, the names are also validated in this paper.