African Journal of Aquatic Science <p>The <em>African Journal of Aquatic Science</em> is an international journal devoted to the study of the aquatic sciences, covering all African waters. The Journal publishes peer-reviewed original scientific papers and short articles in all the aquatic science fields including limnology, hydrobiology, estuarine and coastal marine science. Amongst the topics covered in this Journal are ecology, conservation, bio-monitoring, management, water quality, ecotoxicology, biological interactions, physical properties and human impacts on aquatic systems. Supported by the Southern African Society of Aquatic Scientists, the <em>African Journal of Aquatic Science</em> serves as an indispensable reference source for those interested in understanding the dynamics affecting the valuable aquatic resources of Africa.</p><p class="MsoNormal">Subscriber access to this journal is available online <a href="" target="_blank">here</a></p> en-US Copyright for articles published in this journal is retained by the journal. (Publishing Manager) (Editorial Office) Fri, 28 May 2021 08:35:37 +0000 OJS 60 Quality assessment of surface water using the Nile Chemical Pollution Index (NCPI) and microbiological pollution of the Rosetta Branch (Nile River, Egypt) <p>The Rosetta Branch (Nile River, Egypt) is one of the main sources of freshwater for drinking, agricultural, and industrial activities in the Nile Delta. However, this water supply is compromised because it receives heavy loads of domestic, agricultural and industrial waste from several sources. Water samples were collected seasonally from ten sites along the Rosetta Branch during 2014–2015. The current study aimed to assess the water quality of Rosetta Branch using the Nile Chemical Pollution Index (NCPI), and a microbiological analysis, where the physical and chemical parameters of water branch were measured. Complete depletion of dissolved oxygen was recorded at the discharge points of El-Rahawy and Sobal drains, whereas COD, BOD and nutrient salts, recorded highest levels compared with the reference site of Nile River. The abundance of the major ions was in the following order: HCO<sub>3 </sub>− &gt; Cl<sup>−</sup> &gt; Na<sup>+</sup> &gt; SO4<sub>2</sub>− &gt; Ca<sup>2+</sup> &gt; Mg<sup>2+</sup> &gt; K<sup>+</sup>. NCPI values ranged from 15 to 45 with an average of 31, where, a sudden increase was recorded at sites affected by<br>human activity (Sites 3 and 6) to be grossly polluted, and then the water quality improved slightly farther downstream. Microbial analyses indicated that the total bacterial counts and the total diazotrophs were present in high population densities (up to 105 CFU ml−1). Significant differences in counts were recorded among seasons, whereas no spatial changes were recorded. The total and faecal coliforms populations exceeded the permissible limits cited by World Health Organization (WHO) for drinking water. An intensive water-quality monitoring program is recommended for the Rosetta Branch, and the treatment of wastewater prior to discharge to mitigate health problems outbreaks or any aquatic ecosystem disorders.</p> <p><strong>Keywords</strong>: bacteriological analysis, Nile River pollution, water quality </p> Amal A. Othman, Afify D.G. Al-Afify, Amaal M. Abdel-Satar, Mohamed F. Ramadan Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Development of a Water Quality Assessment Index for the Chania River, Kenya <p>Human-related activities are known to have deleterious effects on the water quality of aquatic ecosystems, but there is limited&nbsp; information on the impact of these on rivers in tropical regions, such as the Chania River in Kenya. The Chania River is an important source of water for humans and animals and provides habitat for a variety of flora and fauna. This study used a Water Quality Index (WQI) to assess the suitability of the water for human use based on selected physico-chemical parameters (nitrates, Total Dissolved solids (TDS), potassium, sulphates, chlorides, copper, manganese, pH and phosphates). Sample collection was done between October 2018 and February 2019 over the dry and the wet seasons. Generally, the WQI indicated that water quality was fair to good in the dry season (19.67 to 30.10) but fair to poor in the wet season (23.17 to 89.15). It is recommended that the riparian zone of the Chania River be protected from anthropogenic disturbances in the County Kiambu.</p> <p><strong>Keywords</strong>: human activities, impacts, riparian zone, Thika town, Water Quality Index </p> G.K. Robert, C.N. Onyari, J.G. Mbaka Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Risk assessment of polycyclic aromatic hydrocarbons in the sediments of the Ekulu River in Enugu State in Nigeria <p>The human health and ecological risks resulting from exposure to polycyclic aromatic hydrocarbons (PAHs) in the Ekulu River sediments were estimated in this study. The Ekulu River receives pollutants potentially containing polycyclic aromatic hydrocarbons (PAHs) from runoff from automotive workshops and abandoned coal mines. The study found that mine drainage, in particular, could be responsible for the relatively high concentration of benzo[a]pyrene (1.266 mg kg<sup>−1</sup>) in parts of river where sand is harvested on a commercial basis. Sources of the PAHs at The Gate and Damija were petrogenic. The consensus-based quality guideline for freshwater sediments using threshold effect concentration and probable effect concentration was the basis employed for evaluating the ecological risks, which were highest at The Gate, because of the presence of fluorene and phenanthrene. Toxicity equivalency (TEQ) at Damija and The Gate did not indicate health risks; however, those at Waterfall were high (1.39 mg kg<sup>−1</sup>), indicating potential health risks. The hazard and risk indices indicate insignificant human health risks.</p> <p><strong>Keywords</strong>: ecological risks, exposure risk, hazard index, human health, hydrocarbons, toxicity equivalence </p> Uzochukwu C. Ugochukwu, Onyechi H. Onuora, Leonard Kurumeh, Uchenna I. Mbakwe, Obiageli J. Okolo, Amaka L. Onuorah Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Soil organic carbon storage in a tropical freshwater wetland: the influence of vegetation type <p>The impact of different vegetation communities on soil organic carbon (SOC) in a tropical freshwater wetland in Uganda was investigated. SOC content, density and storage potential were determined under three different dominant vegetation communities: <em>Cyperus papyrus L., Typha latifolia L.</em> and Phragmites mauritianus Kunth. SOC content (123.7 ± 2.6 SE g C kg−1 dry soil) in C. papyrus was significantly higher (p &lt; 0.05) than in both <em>T. latifolia</em> and <em>P. mauritianus</em>, whereas SOC density (kg C m−2) insignificantly varied (p &gt; 0.05) among the three vegetation communities (C. papyrus = 7.2 ± 0.1, <em>T. latifolia</em> = 6.7 ± 0.1 and <em>P. mauritianus</em> = 6.2 ± 0.1). Similarly, for the entire sampled soil depth (0–50 cm), SOC storage potential was significantly higher (p &lt; 0.05) in <em>C. papyrus</em> (36 118.08 ± 552.52 t C km<sup>−2</sup>), and was in the order of decreasing magnitude: <em>C. papyrus &gt; T. latifolia &gt; P. mauritianus.</em> Plant biomass density, and soil physico-chemical characteristics, bulk density, salinity, pH and temperature were significantly correlated (p &lt; 0.05) with SOC. In conclusion, where climate change mitigation is considered as a wetland ecosystem service, restoration priorities for degraded/lost tropical freshwater wetlands need to consider <em>C. papyrus</em> plants. In addition, comparing SOC storage by ecosystems, Uganda’s wetlands contain three times more<br>SOC than is contained in the country’s forests.</p> <p><strong>Keywords:</strong> carbon sequestration, climate change, <em>C. papyrus, P. mauritianus, T. latifolia,</em> Uganda </p> David Were, Frank Kansiime, Tadesse Fetahi, Thomas Hein Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Diversity of macrophytes in relation to environmental conditions in wetlands along the lower part of the Gilgel Abay River catchment in Ethiopia <p>The environmental conditions in wetlands affect the diversity, composition, and distribution of their macrophyte communities. This study investigated the diversity of macrophytes as related to environmental conditions in wetlands of the lower part of Gilgel Abay River catchment in Ethiopia. The study was conducted between September 2017 and March 2018, during wet and dry seasons using a quantitative quadrat method. Six wetlands, two surrounded by agriculture, two in an urban setting, and two reference sites, were selected, and categorised from most to least impaired. Twenty-seven macrophyte species were recorded from the six wetlands. Macrophyte diversity and density were significantly higher at the least impaired sites. The densities of <em>Floscopa glomerata, Ceratophylum muricatum, Hygrophila asteracanthoides, Hydrocotyle ranunculoides </em>and<em> Echinochloa species</em> were positively associated with ammonium and biological oxygen demand, whereas those of S<em>alix subserrata, Persicaria attenuata, P. strigosa, P. glabra, Cyperus papyrus, C. fischerianus, C. macrostachyos, Ipomoea aquatica </em>and<em> Ludwigia abyssinica</em> were positively associated with depth and salinity, and negatively correlated with nitrate, phosphate, total dissolved solids and electrical conductivity. Generally, the results of macrophyte diversity, composition, and density indicate poor ecological conditions of the wetlands, particularly those adjacent to agricultural and urban areas.</p> <p><strong>Keywords</strong>: anthropogenic disturbance, biodiversity, density, macrophyte diversity index, physio-chemical conditions </p> Habtamu Getnet, Seyoum Mengistou, Bikila Warkineh Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Effects of fragmented mangroves on macrozoobenthos: a case study of mangrove clearance for powerline right-of-way at Oproama Creek, Niger Delta, Nigeria <p>Mangroves are vulnerable to varying magnitudes of degrading impact by human activities. Despite the many benefits of mangrove ecosystems, mangroves in the Niger Delta region are often cleared for electric powerline and oil pipeline rights-of-way, recreation, road construction, housing and farming. The study assessed the impacts of mangrove clearance on physico-chemical parameters of interstitial water and macrozoobenthic primary community structure in Oproama Creek, Nigeria, from February to July 2016. Three stations were selected for the study: two stations in more natural and undisturbed mangroves and one station at a mangrove clearing (for a national grid powerline right-of-way). Species richness and diversity were slightly higher at the undisturbed mangrove sites<br>than the cleared site. Removal of mangrove canopy shade alters microclimate temperature regime and other temperature-dependent parameters, imposing thermal stress on stenothermal taxa and ancillary stressors that compositely affected primary community structure indices. Deliberate loss of mangroves through clearing waterfront vegetation as a driver for improved visual monitoring and enhanced security in the Oproama Community in the Niger Delta is reported for the first time. The wider implications of mangrove clearance and fragmentation on ecosystem-based goods and services are discussed. Limiting mangrove spatial loss owing to&nbsp; construction of an electric tower cutline within coastal landscape is strongly recommended.</p> <p><strong>Keywords</strong>: carbon sequestration, conductivity dynamics, ecosystem services, sediment heating, water quality </p> N. Zabbey, I.G. Ekpenyong, G.N. Nwipie, I.C. Davies, K. Sam Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Species composition and distribution of mayflies (Ephemeroptera) in relation to land use systems along the Thika River, Kenya <p>Mayflies (order Ephemeroptera) are widely distributed and commonly used in biological assessment of water quality because of their sensitivity. Their application as bio-indicators in tropical streams and rivers, however, is hampered by lack of adequate information about their status in many such ecosystems. The current study investigated their species composition, distribution and abundance in relation to land use and water quality characteristics of the Thika River, Kenya. The Thika River emanates from the Aberdare Ridges and flows through forest, agricultural and urban catchments. Sampling was carried out at three sites representing forest, agricultural and urban land use systems. Dissolved oxygen, conductivity, total dissolved solids, temperature and transparency were measured in situ at each sampling station. Macroinvertebrates were sampled using a modified Hess sampler and the Ephemeropterans were later identified and sorted in the laboratory. Thirteen Ephemeroptera genera belonging to six families were obtained. Mean larvae abundance was 1 238 ind. m<sup>−2</sup>. Acanthiops (70.4%) and Afronurus (13.3%) dominated the community at all sites. The current study revealed that decreasing Ephemeroptera taxa abundance along the river channel indicates decreasing water quality.</p> <p><strong>Keywords:</strong> abundance, Acanthiops, Afronurus, macroinvertebrates, water quality </p> C. Maina, B.M. Mwangi, J.J. Jumbe Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Settlement of the invasive mussel <i>Mytilus galloprovincialis</i> in a warm temperate estuarine embayment in South Africa <p><em>Mytilus galloprovincialis</em>, a globally successful marine alien invasive species, occupies all artificial hard substrata in the embayment of the Knysna estuary, South Africa. The current study compared temporal and spatial settlement patterns of <em>M. galloprovincialis</em> within this environment. Settlement was monitored monthly from November 2015 to June 2017 at three locations within the embayment using plastic scouring pads. Each month the pads were deployed for seven days over a spring tide. Numbers of settlers differed significantly among sites and time. Peak settlement occurred in summer (December) and early autumn (February or March), but number of settlers varied between years possibly owing to differences in larval supply and/or environmental factors. During peak settlement, most <em>M. galloprovincialis</em> collected on the pads were primary settlers (&lt;0.5 mm long). Settlement was greatest at the site closest to the entrance of the embayment (Thesen Island Wharf) and lowest at the site farthest away from the entrance of the embayment (Railway Bridge). Variation in settlement among sites and years could be a response to hydrographical conditions and/or environmental conditions and detailed studies on the planktonic phase are now required.</p> <p><strong>Keywords</strong>: invasive species, Knysna Estuary, Mollusca, Mytilidae, primary settlers, secondary settlers </p> J. Radloff, A.N. Hodgson, L. Claassens Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Diet of the mullets <i>Planiliza macrolepis</i> and <i>Moolgarda cunnesius</i> in the Mfolozi-Msunduzi Estuary, KwaZulu-Natal, South Africa <p>The mullet species, <em>Planiliza macrolepis</em> and <em>Moolgarda cunnesius</em>, were collected seasonally from Mfolozi-Msunduzi Estuary on the east coast of South Africa in order to determine their diet. The gut contents of 178 fish with standard length (SL) ranging between 100 and 220 mm revealed strong evidence that in the Mfolozi-Msunduzi these fish rely heavily on benthic floc as a primary food source. Plant debris and small benthic organisms, including Assiminea, copepods, nematodes and ostracods also formed part of their diet. Some of these food items (e.g. <em>Assiminea sp</em>. nematodes) were only consumed by <em>P. macrolepis</em>. Differences in the occurrence of food items consumed by these two closely related species may be explained by their feeding ground preferences. Results suggest that <em>P.&nbsp; macrolepis</em> forages in substrata mostly dominated by fine-to-medium sand grain sizes (&lt;50 to 450 µm), whereas <em>M. cunnesius</em> prefers substrata dominated by fine sand to muddy grain sizes (50 to 250 µm). Based on these findings, it is concluded that differences in substrate preference by these two mullet species is an important strategy by which they circumvent any possible interspecific competition for food resources within the system.</p> <p><strong>Keywords</strong>: benthic floc, food, organic content, sand grain size</p> W. Qwabe, D.P. Cyrus Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Identifying multiple geographically restricted phylogeographic lineages of Moggel (Cyprinidae: <i>Labeo umbratus</i>) in South Africa <p><em>Labeo umbratus</em> (Smith, 1841) is a widespread species with populations distributed across isolated southern African river systems. Given that cryptic lineages have been detected in freshwater fishes with a similar distribution, a phylogeographic study of <em>L. umbratus</em> was conducted, considering populations sampled from nine currently isolated river systems between 2008 and 2013. Analyses of mitochondrial DNA (cyt b) and nuclear DNA (S7) sequence data demonstrated that two unique lineages occur in the west-flowing Orange River and south-flowing drainages, respectively. The southern lineage was further divided into three sublineages: one restricted to the Gouritz River, the second largely confined to the Gamtoos River and the last distributed across catchments to the east (the Sundays, Bushmans, Great Fish, Keiskamma, Buffalo and Nahoon rivers). The Great Escarpment and deep incisions along the south coast were identified as potentially influencing the geographic genetic structure of this species. For conservation purposes and pending future taxonomic assessment, the two major lineages were identified as Evolutionarily Significant Units, and Management Units were identified within the southern lineage.</p> <p><strong>Keywords</strong>: conservation, cyt b, ESUs, freshwater, genetic diversity, Great Escarpment, MUs, S7 intron I </p> M. Ramoejane, O.L.F. Weyl, E.R. Swartz, G. Gouws Copyright (c) Fri, 28 May 2021 00:00:00 +0000 First record of <i>Chlamydomonas proboscigera</i> in the southern hemisphere <p><em>Chlamydomonas proboscigera</em> is a unicellular, ellipsoidal-to-spherical chlorophyte distinguished by a flattened papilla, a large spherical pyrenoid and a disc-shaped stigma located anterior in a cup-shaped chloroplast. The species is common in eutrophic water, but also occurs in terrestrial environments, such as soils. Previously, <em>Chlamydomonas proboscigera</em> was only described from certain parts of Europe, Asia and northern Africa (Algeria). The findings of <em>C. proboscigera</em> in South Africa during 2019, represent the first reported record of this species in the southern hemisphere and sub-Saharan Africa.</p> <p><strong>Keywords</strong>: Africa, algae, <em>Chlamydomonas iyengarii, Chlamydomonas subglobosa, Chlamydomonas sphaeroides, Chlorophyta, eutrophic</em></p> M. Laubscher, S. Janse van Vuuren, A. Levanets, S. Barnard Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Zooplankton composition of temporary pools within the lower Nata River channel, Botswana, during dry season <p>The Nata River is a seasonal system situated in the semi-arid north-eastern Botswana, where rainfall is unpredictable and drought is&nbsp; ommon. The annual flow of approximately 279 million cubic meters is regionally significant and it forms an important resource for people and biota in the region. Information on the biological diversity of the Nata River is scarce and, to our knowledge, no data is available on its invertebrate fauna. The aim of the study was to provide the first record of the aquatic microinvertebrates of the lower Nata River and examine likely influences of water quality parameters on its species diversity. Physical water quality parameters were<br>measured and zooplankton sampled along the lowermost reaches of the Nata River in August 2012. Salinity, TDS and electrical conductivity ranged widely between sites. Remarkable differences were evident in the zooplankton species composition between the four study sites, evidently related to prevailing levels of salinity.</p> <p><strong>Keywords</strong>: Calanoida, Cladocera, diversity, ephemeral river, physical parameters, Rotifera, water quality </p> D.T. West, L.L. van As Copyright (c) Fri, 28 May 2021 00:00:00 +0000 Can bait improve the efficiency of underwater video monitoring of fish in headwater streams? A case study from the Rondegat River, South Africa <p>The use of action cameras for underwater video sampling provides a non-harmful alternative for monitoring endangered and threatened fish populations in clear headwater streams. Here, we examine the use of baited remote underwater video systems (BRUVS) for the monitoring of vulnerable species in the clear headwater streams of the Cederberg Wilderness Area, South Africa. We tested whether baits (bread and Marmite™) increased the number of individuals recorded in comparison to un-baited BRUVS. Overall, baiting cameras increased the number of individuals recorded, with bread outperforming Marmite™. Numbers recorded varied notably among species and sites. We conclude that BRUVS are a useful monitoring tool, but caution that monitoring programmes should first<br>determine the effectiveness of a range of baits to attract each species expected at the study sites.</p> <p><strong>Keywords:</strong> action cameras, Baited Underwater Video Systems, BRUVS, freshwater fish, MaxN, monitoring </p> S.Z. Bajaba, S . Hugo, A.J. van Wyk, S.M. Marr, N.G. Vine, O.L.F. Weyl Copyright (c) Fri, 28 May 2021 00:00:00 +0000