African Journal of Aquatic Science

Effects of land-use change on the provisioning ecosystem service of wetlands: the case of a social-ecological systems perspective of Boyo Wetland in Ethiopia

2024-06-21T09:35:51+00:00

Wetlands are catchment life support systems with diverse ecological and socio-economic functions. They have played a significant role in the growth of African human civilisations and cultural development, and today contribute billions of US dollars’ worth of ecosystem services to the people of Ethiopia. Ethiopia exhibits both natural and man-made wetland types that cover up to 2% of its land surface. They are, however, under threat from excessive pressures that are both ecologically and socially driven. The objective of this study was to analyse the state of ecosystem services provision of the Ethiopian wetlands, with a novel application of Ostrom’s Socio-ecological Systems Framework (SESF), taking Boyo Wetland as a case study. Household surveys, focus group discussions and stakeholder analysis methods were applied to satisfy the data needs of SESF. Insufficient knowledge of actors on wetland ecosystem services, weak governance and limited self-organisation among actors are highlighted as the major reasons contributing to the unsustainable use of wetlands. When the use of Boyo Wetland’s ecosystem services was evaluated using the SESF, it was evident that unsustainable resource use practices are widespread. These findings could be used to inform national policy on wetlands and local strategies for the sustainable use of wetland resources by direct or indirect users at different levels.

Assessment of surface water quality in a highly anthropised semi-arid catchment (Case of Wadi El Hatab Basin, Tunisia, North Africa)

2024-06-21T10:37:53+00:00

Anthropogenic contamination of surface waters is a critical issue in urbanised catchments, especially in Mediterranean environments with scarce water resources and intermittent rivers. A combined hydro-geochemical and multivariate statistical methodology has been applied to evaluate the surface water quality of Wadi El Hatab catchment (Central Tunisia). More than half of the 28 samples collected in March 2021 exceeded WHO standards for sodium, chloride and sulphate contents. Most polluted sites are directly influenced by domestic and industrial effluents that contaminate the river for kilometers. Principal Component Analysis and Hierarchical Ascendant Classification distinguished four contamination sources: water-rock interaction, domestic wastewater, untreated industrial effluents mainly from paper mills and irrigation return. A Water Quality Index model indicated that 75% of the surface water was unsuitable for drinking purposes; while according to chemical indices such as saturation index, sodium absorption coefficient (SAR), magnesium ratio (MR) and percent sodium (%Na), 25 to 49% of samples were unsuitable for irrigation. Considering that water of Wadi El Hatab is used for vegetable irrigation, serious public health issues may arise. The investigation demonstrated that a single representative sampling campaign could be a useful way to identify contamination sources when interpreted with both statistical and geochemical tools.

Status and distribution of a novel redfin lineage, Pseudobarbus sp. ‘burchelli Tradouw’ from the Cape Fold Ecoregion of South Africa

2024-06-21T10:44:01+00:00

Freshwater fish are threatened globally and in addition, knowledge of their diversity is incomplete and species richness is underestimated. Within the ichthyofauna of the Cape Fold Ecoregion of South Africa, many undescribed lineages exist and for most of these, information is limited regarding their ecology, distribution and threats. The Tradouw redfin Pseudobarbus sp. ‘burchelli Tradouw’ is a novel and range-restricted lineage within the Breede River redfin Pseudobarbus burchelli. Annual monitoring conducted between 2012 and 2016 investigated spatial and temporal trends in the distribution and population dynamics of this taxon. Results indicated that it is highly fragmented within its distribution range, likely a result of the combined pressures of invasive fish and poor land use practices. Short-term monitoring results indicated that invasive fish are established in most of the catchment and that the relative abundance of redfins remained constant only in the limited section of river where alien fish were absent. Poor land use practices such as water over- abstraction and surface water pollution, are pervasive threats, but the extent to which these affect the redfins requires further investigation. The long-term survival of this taxon remains uncertain, and short-term and long-term conservation and management options are explored.

Development of new assessment approach: a macroinvertebrates-based biotic scoring system to assess the health of riverine ecosystems in the Sahel area in Burkina Faso (West Africa)

2024-06-21T10:50:32+00:00

To address ongoing threats from human pressures and climate changes, water managers and users require a visual tool that provides accurate information about the health of waterbodies for decision making. However, there is a lack of less sophisticated methods, such as biotic scoring, to assess the health of rivers in West Africa. To bridge this gap, we have developed a macroinvertebrate-based scoring system for monitoring the health of rivers in the Sahelian regions. We adopted a multi-habitat sampling approach to collect macroinvertebrates using hand nets, and these specimens were identified mostly to family taxonomic level using keys. We recorded more than 75 taxa of macroinvertebrates, each assigned relative sensitivity scores to human disturbances ranging from 1 (very tolerant) to 10 (highly sensitive). The Burkina Biotic Score System (BBIOSS) and the Average Score Per Taxa (ASPT) demonstrated a strong and significant correlation with environmental variables, including anthropogenic pressures types (r = 0.6; p < 0.01) making it a robust tool for monitoring rivers. Here, our findings revealed that all taxa scored are expected to be those reported in Western African freshwater. This study has produced an effective tool that can be used or adapted to monitor other riverine ecosystems in West Africa, potentially contributing to the preservation of water and biological resources.

Assessment of water quality and associated human health risk of a tropical freshwater body in Edo State, Nigeria

2024-06-21T11:03:27+00:00

The quality of freshwater sources is a key factor in sustainable development. This study investigated the water quality suitability of Ossiomo River for human consumption and the implications for public health. Water samples were collected and analysed from October 2021 to March 2022. Results indicated that the water physico-chemical parameters from sampled locations were within their respective National Environmental Standards and Regulation Enforcement Agency (NESRA) permissible limits except for pH (< 6.5), dissolved oxygen (< 6.0mg L⁻¹ ), cadmium (> 0.005m /L⁻¹ ), manganese (> 0.05mg L⁻¹ ) and total hydrocarbon content (>10mg L⁻¹ ). Comprehensive pollution index (0.4–1.0) and water quality index (251.57–765.37) values indicate that the water body was slightly polluted and unsuitable for human consumption (WQI > 50). Health risk assessment showed that children and adults were predisposed to non- carcinogenic risk (HIoral > 1) and carcinogenic risk (ICR: 1.21E-02 and 2.84E-03) from heavy metals through oral exposure. Natural run-off and anthropogenic activities were identified sources of heavy metals and hydrocarbons within the catchment. The study has provided data for water resource quality monitoring and raised concerns as to the need for immediate action to safeguard the public health of communities surrounding the Ossiomo River, through the provision of alternative sources of potable water.

Appraisement of groundwater quality status within Enugu, Nigeria, using physicochemical evaluation and water quality indices

2024-06-21T11:34:11+00:00

Enugu state is notorious for potable water scarcity which forces residents to depend on polluted water sources. In this study, an appraisement of the quality status of groundwater from some areas within Enugu was conducted. Physicochemical characteristics of groundwater sampled from 15 boreholes that supply domestic water to Aninri, Awgu, Ezeagu, Udi and Oji River Areas of Enugu, Nigeria, were determined. A total of 45 water samples were obtained across both rainy and dry seasons. Standard methods were used to determine the physicochemical parameters and trace metals. The physicochemical results showed values within the WHO safe limits, except sulphate (1670 ± 21.5 mg L−1) in Mpu water samples, and high chloride levels in Ndeaboh and Mpu (18088 ± 29.4 and 1095 ± 23.9 mg L−1 for dry and rainy seasons, respectively). The pH values were predominantly slightly acidic, ranging from 5 to 8.2. Groundwater within Ukaete, Ndeaboh, Oduma and Amankpunato had very high levels of electrical conductivity (2897.80 ± 173.38, 31000 ± 45.9, 1672 ± 9.3 and 1222 ± 8.1) in the dry season, respectively; and 1665.06 ± 326.6, 5410 ± 2.4, 4860 ± 9.4, 1872 ± 19.3 in the rainy season, respectively. The higher chloride values observed, possibly due to a geogenic origin, could also be responsible for the higher values of the electrical conductivity. There were traces of copper and lead in the samples during the dry season; however, lead was not detected in most borehole water samples during the wet season. Fe was the only metal that recorded values above the WHO standard. Traces of copper in the samples may have resulted from corrosion in the copper pipelines, reservoirs or other metallic fittings used in the construction of the boreholes. The water quality index (WQI) of the borehole water examined was above 100 in all except Ogugu Awgu samples, indicating that borehole water was generally not potable and therefore unsuitable for domestic application or drinking. The observed results revealed that the groundwaters from the study area were contaminated with chloride and lead, causing the water parameters to be above standard limits. Lead at any concentration is deemed toxic according to USEPA. There is a need to treat borehole water supplies in the area before its application for domestic use.

Zooplankton composition following an artificial mouth breaching event in Lake St Lucia, South Africa

2024-06-21T11:49:04+00:00

Lake St Lucia is one of the most important estuarine systems in South Africa, but the long history of anthropogenic intervention has threatened its integrity. With the exception of sporadic overtopping events and periodic marine connectivity via the uMfolozi River, the St Lucia Estuary remained closed off from the Indian Ocean since 2007. Due to the build-up of sediment and prolonged mouth closure, the beach berm was artificially breached in January 2021, fully reconnecting St Lucia to the Indian Ocean for the first time in 13 years. This study aimed to determine the effect of this breaching event on St Lucia’s zooplankton community by analysing samples from March, May and August 2021, at five representative sites throughout the lake system. The mouth remained open for only five months, and the system was still largely oligo- to meso-haline due to high freshwater input. The patterns in the zooplankton were related more to the prevailing environmental conditions than to the breaching event itself. The composition of zooplankton in the system did change; however, the presence of marine taxa was not far-reaching nor long-lasting, most likely due to the limited tidal intrusion, strong outflow and predominant salinity regime.

Reproductive biologies of Psammogobius knysnaensis and Caffrogobius gilchristi in a warm-temperate South African estuary

2024-06-21T11:57:29+00:00

Reproductive biologies (spawning period, length at maturity and fecundity) of the Knysna sand goby Psammogobius knysnaensis and the Prison goby Caffrogobius gilchristi were investigated between September 2018 and August 2019 in the warm-temperate Sundays Estuary, South Africa. The two species reproduced during the same period (spring and summer) with peak reproduction occurring in January. P. knysnaensis egg production was higher than C. gilchristi and was not affected by fish size. Although C. gilchristi egg production increased with fish size, this was not significant. P. knysnaensis reached LM50 at smaller sizes than C. gilchristi. Reproductive periods were likely coupled with prey availability, as phytoplankton and zooplankton abundances are highest in warm-temperate estuaries during this period. The ability of these gobies to reproduce at small sizes (< 40 mm TL), which is an adaptive trait of many r-selected species, underpins their high abundance in South African estuaries asthey are well adapted to stochastic environments.