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Background Wetlands are transition zones between aquatic and terrestrial environments of Opa Reservoir Obafemi Awolowo University, Ile-Ife, Nigeria, threatened by increase in agricultural practices and urbanization within the catchment area. A critical appraisal of the current ecological integrity of the wetlands using planktonic composition and community structure which are formidable to sustaining wetlands is essential, hence this study. Result A total of 104 plankton species comprises of 68 species of phytoplankton and 36 species of zooplankton were recorded from the wetlands. In each sampled location and during the sampling period, Bacillariophyta had the highest occurrence among the phytoplankton, while Rotifera recorded the highest occurrence among the zooplankton. Generally, Synedra ulna and copepod (cyclopoid) Nauplius, respectively, were the most common phytoplankton and zooplankton recorded during the period of study. Analyses also showed that the phytoplankton had a higher species occurrence and abundance (65.3% and 98.18%, respectively) than the zooplankton (34.6% and 1.82%, respectively). Diversity indices (Shannon–Wiener, Margalef, and Simpson) analyses of both plankton groups revealed that the wetlands were generally polluted. Conclusion The study concluded that the ability of the wetlands to support and maintain a balanced adaptive community of plankton with species composition and diversity is being eroded due to anthropogenic activities in the wetland areas. This could have some ecological and socioeconomic implications considering the fact that they are intrinsically a part of the adjoining reservoir which provides many ecosystem services.

The adoption of the Aichi Biodiversity Targets (ABTs) was supposed to increase conservation awareness in different countries and regions of the world. However, there seems to be a limited understanding of the importance of ecosystem services, offered by biological diversity. Thus, the continued decline in biodiversity, especially in developing countries. This study appraised the level of success of the first target of Nigeria's National Biodiversity Strategy and Action Plan (NBSAP), which is hinged on the first ABT. In a national survey, data were obtained from a total of 1,124 respondents (839 professionals and 285 non-professionals), using a structured questionnaire. Information on the respondents' knowledge of biodiversity conservation and the associated ecosystem services, were elicited. Most of the non-professionals had a low level of understanding of biodiversity concepts (4.9 ± 1.7 to 20.5 ± 3.4%), while there was a moderate level of understanding among the professionals (48.0 ± 8.6 to 88.8 ± 3.4%). Awareness of the NBSAP was low for both groups (43.8 ± 7.2% professionals and 12.1 ± 3.7% non-professionals). The study concludes that there is a need to step up campaigns on biodiversity conservation in Nigeria and promote visits to natural sites. Youth engagement through the employment of graduates of biology-related disciplines, to educate the public on biodiversity conservation and the action plan, could also be a strong determinant to the success of the NBSAP targets.

Rapid population growth and poor waste management practice are among the main drivers of plastic pollution in modern times, thus making Africa a hotspot for plastic pollution both now and in the future. This study is a review of plastic pollution reports from the African aquatic environment with regard to causes, current status, toxicological implications and implications for ecosystem services. A total of 59 plastic pollution studies from 1987 to September 2020 were reviewed. They comprised 15 from North Africa (NA) (Algeria, Egypt, Morocco and Tunisia), six from East Africa (EA) (Ethiopia, Kenya, Tanzania and Uganda), 13 from West Africa (WA) (Ghana, Guinea-Bissau, Mauritania and Nigeria), and 25 studies from Southern Africa (SA) (South Africa). This shows that plastic pollution studies in Africa, according to the sub-regions, are in the order: SA > NA > WA > EA. High human population in the basins of African large aquatic systems is identified as the greatest driver enhancing plastic surge in the aquatic environment. The occurrence of plastics was mostly reported in the estuarine/marine environment (42 studies) compared to the freshwater environment (only 17 studies). Plastics have also been reported in the three compartments of the aquatic environment: water column, benthic sediment and animals. Zooplankton, annelids, molluscs, insects, fishes and birds were reported as bioindicators of plastic ingestion in the inland and coastal waters of Africa. Polyethylene, polyethylene terephthalate (polyester) and polypropylene were the common plastic polymers observed in the African aquatic environment. In situ toxicological implications of the ingested plastic polymers were not reported in any of the studies. However, reports from laboratory-controlled experiments showed that these polymers are deleterious to aquatic animal health. More research efforts need to delineate the plastic pollution status of the East, West and North of Africa. Furthermore, such studies are required to identify the plastic polymers and in situ ecotoxicological impacts of plastics on both animal and human health.

Heavy metal pollution is one of the threats to aquatic ecosystems globally and it portends a great danger to the sustenance of aquatic biodiversity in Afro-tropics, in particular. Bottom sediment samples were collected from three small African rivers, namely: Obudu river, Opa river, and Esinmirin river from Sep 2004 to July 2005. The samples were air-dried in the laboratory, digested and subsequently extracted for Ni, Fe, Zn, Cu, Pb, Cr, As, Co, Mn, and Cd using the atomic absorption spectrophotometry. Most of these metals recorded their highest values in the Esinmirin river and the lowest values in the Obudu river. However, the Kruskal–Wallis test revealed that only two metals (i.e., Cu and Pb) showed a significant difference (p

Plastic pollution has enormous impacts on freshwater and marine ecosystem health, and it is one of the topmost environmental concerns of the current geological period (i.e. the Anthropocene). Thus, the goal of our study was to provide baseline information and bridge the information gap on the occurrence of microplastics (MPs) in African freshwater systems, using two tributaries of the Gulf of Guinea (Ogun and Osun Rivers) in Nigeria as a case study and three freshwater insect species of different feeding guilds as bioindicators. A total of 29 individuals of the insect species were chemically digested and subsequently analysed for MP presence under a digital microscope and a micro-Fourier-transform infrared (μFTIR) spectroscope. Collector-gatherers (Chironomus sp. and Siphlonurus sp.) recorded the highest MP load per gram wet weight, while the predatory Lestes viridis recorded the lowest. The highest diversity of polymers was recorded in Chironomus sp. of Ogun River, i.e. styrene ethylene butylene styrene, acrylonitrile butadiene styrene (ABS), chlorinated polyethylene, polypropylene (PP), and polyester, while two polymers each were recorded in Siphlonurus sp. (i.e. polyester and ABS) and L. viridis (i.e. polyester and PP) of Osun River. We conclude that collector-gatherers like Chironomus sp. and Siphlonurus sp. could be best employed as MP bioindicators in freshwater systems. However, their suitability as MP bioindicators should be further investigated in different freshwater ecosystems worldwide.

Background Headwater streams and small rivers within a catchment basin contribute greatly to the overall physico-chemical and biological quality of downstream larger freshwater systems; hence, there is a need to continually assess the water quality of such smaller systems. In this study, the three major tributaries (Obudu, Opa, and Esinmirin rivers) of a tropical reservoir were assessed for their water quality using some selected water and sediment parameters, as well as their macroinvertebrate faunae. Results All the measured water parameters were found to be within the recommended standards for freshwater life in the three rivers, except for PO43− and dissolved oxygen in Opa River which was possibly due to anthropogenic factors. The bottom sediment of the rivers was predominantly sandy and generally low in chemical characteristics. A total of 17 species of macroinvertebrates were recorded in this study: 14 species in Obudu River, 12 species in Esinmirin River, and 11 species in Opa River. Diversity (Margalef and Shannon-Wiener) and Pielou’s evenness indices were all low and indicative of an impaired freshwater system, with the lowest indices recorded in the Esinmirin River. Some macrobenthic environmental indicators of poor water quality (e.g., Tubifex sp., Tipula sp., Chironomus sp., Bulinus globosus, and Eristalis sp.) were exclusively recorded in the Esinmirin and/or Obudu River. Conclusion The study concludes that the reservoir’s headwaters were moderately polluted and had a tendency to become severely polluted by anthropogenic activities along the rivers. Measures should be put in place to reduce environmental impact on the quality of the headwaters and by implication, the reservoir.

Despite the increasing awareness of sacred groves as potential biodiversity hotspots, freshwater systems that drain such environments are not being duly explored for their biodiversity values. In a...

Introduction Osun River dissecting the Osun-Osogbo Sacred Grove, though inscribed on the World Heritage List, has been rarely assessed for biodiversity values or ecotoxicology. In this study, we investigated the concentrations of Cu and Zn in the benthic sediments and two dominant gastropod species (Melanoides tuberculata and Lanistes varicus) of the Osun River. Benthic sediment and gastropod samples were collected on quarterly basis from June 2015 to March 2016 along the longitudinal stretch of the river. Dry samples were digested and analysed for Cu and Zn using the atomic absorption spectrophotometry. Results With the exception of September sampling period, the two metals recorded higher values in the animals than in the sediments. Cu (1.23 ± 0.81 μg/g) was much lower (p

Agriculture and other anthropogenic activities on riparian corridors pose a great ecotoxicological risk to freshwater ecosystem and human health. Using the atomic absorption spectroscopy, concentrations of heavy metals (Cd, Cu, Fe, Zn, Pb and As) in the water column and benthic sediments of a degraded tropical stream (Opa Stream, Ile-Ife, Nigeria), were assessed with a view to determining the stream's health status. Three metals (Cu, Pb, and As) showed significant positive correlations between concentrations in the water column and the benthic sediments. All but one heavy metal (i.e. Zn) had reached disturbing concentrations in the stream's water column and exceeded their recommended limits in surface freshwaters. The geo-accumulation index (Igeo) and contamination factor (CF) indicated that the stream was moderately contaminated with Cd (0

Bed sediment samples of the two headwaters of a tropical reservoir in Southwestern Nigeria were analysed for some metal concentrations using ICP-OES for a period of one year. Sediment samples were collected bi-monthly from both the lower and upper reaches of the streams from May 2013 to March 2014. Sediment samples were microwave-digested and analysed using ICP-OES. Concentrations of metals were higher in the lower reach than in the upper reach, and wet season concentrations were higher than in the dry season with the exception of Fe and Mn. The annual mean metal concentrations were as follows: Fe (121.72 ± 6.82 µg/g); Mn (9.34 ± 2.57 µg/g); Na (6.20 ± 2.29 µg/g); K (0.65 ± 0.57 µg/g); Mg (8.07 ± 1.36 µg/g); Ca (13.92 ± 2.85 µg/g); Ba (0.17 ± 0.17 µg/g); Al (106.54 ± 5.55 µg/g); and Se (0.6 ± 0.19 µg/g). These values were lower in comparison with the baseline concentrations of elements on the earth’s crust. Contamination assessment of all the metals investigated in this study showed that metals in...

Our current understanding of environmental micro(nano)plastic (MNP) pollution is driven by field and lab-based studies performed predominantly by and in wealthier countries. However, mismanaged waste and its consequences affect low- and middle-income countries over-proportionately. Evidence suggests that studies on MNP pollution in Africa are critically limited by the scientific infrastructure available, restricting research activities to opportunities for external collaboration with established research laboratories in the Global North. The development of Pan-African research networks and analytical nodes, is required to support intra-African research exchange and training, and drive evidence-based policy relevant to an African context. This can facilitate more inclusive conversations around the harmonization and standardization of methods currently mainly available to the Global North.

Background and Research Lack of information on the distribution of threatened aquatic species impedes their conservation, thus predisposing them to extinction risk before being reported. Hence, this study reports in Nigeria, for the first time, the occurrence and habitat specificity of the larva of Pentaphlebia stahli (Zygoptera: Pentaphlebiidae) a vulnerable damselfly. Methods Samples of P. stahli were collected in July and December 2020 from a rural stream situated at the Ekor Waterfalls in the Cross River State of Nigeria and very close to the Nigeria–Cameroon border. Some water quality parameters were also measured in each sampling period. Results A total of 27 larvae of P. stahli and 1 teneral adult emerging from its exuvia were recorded in the two sampling periods. The habitat was a forested stream characterized by rapids, falls, and dark rock substrata. Water flows at a fast rate of 1 m in 3 or 4 seconds, thus characterizing a rifle and headwater stream. Dissolved oxygen concentration was between 8.05 and 8.09 mg/L, while dissolved oxygen saturation was ∼98%. Biological oxygen demand was between 1.04 and 1.08 mg/L, while pH ranged from 7.28 and 7.56. Conclusion The stream could be described as having high ecological integrity as evidenced in its optimum range of values for the investigated water parameters and the presence of a threatened species. Implications for Conservation Based on habitat specificity, P. stahli is considered an umbrella species required for conserving other co-occurring species in the tropical stream and its riparian forest.

The assemblage of benthic macroinvertebrates in relation to some selected environmental variables of the two headwater streams of Aiba Reservoir was studied from May 2013 to March 2014. This was with a view to assessing the health status and water quality of the streams, and comparing their taxa richness with similar studies on the reservoir and its out-flowing stream. A total of 23 taxa were recorded in the study. and showed indirect relationships (P

The physicochemical water condition and zooplankton fauna of the two main inflows of Aiba Reservoir were assessed over an annual hydrological cycle (May 2013–March 2014). The concentrations of total solids (TS) and total suspended solids (TSS) in the two streams were unusually higher in the dry season for typical inland waters of Nigeria and showed a decrease from the upper reaches towards the lower reaches (reservoir’s inlet). Dissolved oxygen, NO3-, and PO43- recorded their highest concentrations at the reservoir’s inlet. A total of 37 species of zooplankton were recorded in the study, comprising 5 species of Protozoa, 14 species of Rotifera, 10 species of Copepoda, 4 species of Ostracoda, and 4 species of Insecta. Aiba stream recorded higher number of zooplankton species and abundance than Onikan stream. While number of zooplankton species and abundance showed an increase from the upper reaches to the lower reaches of both streams, species diversity and equitability generally showed a decrease. Correlation and regression analysis suggests that the concentration of TS and TSS played a major role in determining the zooplankton community structure of the streams. PO43- concentrations as well as the community structures of zooplankton faunas of the two streams were indicative of a polluted freshwater system with unstable habitat structure.

Freshwater environments are the route through which inland plastics are transported to the ocean, explaining why the number of freshwater microplastic (MP) studies has recently been increasing. Despite the lack of recycling and the presence of severe plastic pollution in many African countries, MPs have been scarcely reported in African freshwaters and the current study gives the first empirical account for West Africa. The study investigates MP pollution in an important West African river system (Osun River system, Nigeria) and gives an insight into microplastic contamination in a main European river (Rhine River), using gastropods which are potential consumers of MPs, from both systems. From the Osun River system, the most common gastropods (Lanistes varicus and Melanoides tuberculata) were analysed for MP contamination. Two MP types (fibre and film) were recorded in L. varicus, whereas only fibre was recorded in M. tuberculata. Micro-Fourier-transform infrared spectroscopy (μFTIR) revealed that the MP films in the African gastropods were made of polyethylene and strongly resembled black polyethylene bags that covered the Osun River banks. From the Rhine River, the gastropod Theodoxus fluviatilis was analysed and nylon as well as polypropylene fibres were found. In both systems (Osun River and Rhine River), fibre was the dominant MP type. In conclusion, the study shows that MP contamination in Nigeria, a West African country with a lack of recycling and poor waste management practice, is reflected in two different local gastropod species. Furthermore, the comparison with a European gastropod species shows that fibres are the dominant MP type in gastropods from both freshwater systems. In both systems, MPs ingested by the gastropods could be transferred to higher trophic levels following predation. We therefore recommend that more empirical studies should be carried out along different feeding guilds of African freshwater invertebrates and fish. When MPs are transferred to fish, MPs may reach humans through fish consumption.

Zooplankton in Lake Tiga was identified and its community structure assessed between March 2009 and March 2011. A total of 54 species of zooplankton was recorded, comprising two species of Protozoa, 26 species of Rotifera, eight species of Copepoda, 11 species of Cladocera, four species of Ostracoda and three species of insect larvae. Species occurrence and abundance were both higher in the dry season than in the rainy season. Occurrence showed an increasing trend from the upper basin towards the lower basin (dam site) in the surface waters and a decreasing trend from the surface down to the bottom of the lake. Zooplankton abundance showed no definite pattern in its surface horizontal variation but showed a decreasing trend from the surface down to the bottom of the lake. In terms of species diversity, Rotifera had the highest number of zooplankton species, followed by Cladocera, Copepoda, Ostracoda, insect larvae and Protozoa. In terms of abundance, Rotifera again had the highest abundance value, followe...

The physico-chemical water quality of Lake Tiga was monitored over a two-year period (March 2009- March 2011) in order to bridge the information gap on its limnology and assess its physico-chemical condition. Turbidity, Dissolved Oxygen (DO) saturation and organic matter were significantly higher (p

Odonate fauna of Iloyin Forest was studied from October to December 2009 to have an overview of the species composition and distribution with the threat of deforestation in the area. Adult species were collected once a week using a sweep net throughout the period of the study from three study sites (denoted as I, II and III) with varying levels of anthropogenic disturbance. A total of 76 species belonging to eight families were recorded in the forest. The two most abundant families in the forest were the Libellulidae (Anisoptera) and Coenagrionidae (Zygoptera). Palpolpeura portia , P. lucia and Congothemis dubia were the dominant species of Libellulidae, while Pseudagrion kersteni was the dominant coenagrionid. Some species of Odonata usually associated with shaded forests were encountered in two of the study sites. The highest diversity and evenness indices were recorded at Site I, followed by Site II and the least recorded at Site III. Although shade-loving species recorded in the study area was an indication of its richness in forest Odonata, some may have however become locally endangered or extinct as a result of deforestation. A check in the rate of deforestation could preserve the few forest (endangered) species and restore the locally extinct ones that changed habitats. Key Words: Biodiversity, Conservation, Disturbance, Forest, Freshwater, Odonata

Ori stream (one of the tributaries of River Oba, Iwo, Osun State, Nigeria) was studied from October to December 2013 with the aim of providing baseline information on its water quality, phytoplankton primary productivity and invertebrate faunal composition. Plankton samples were collected by towing plankton net over a 2 metres horizontal distance, while benthic macroinvertebrate samples were collected by kick-sampling technique. Hydrological and some physico-chemical variables were determined in-situ , and water samples collected for further physico-chemical analyses in the laboratory. A total of 17 phytoplankton species, seven species of zooplankton and eight species of benthic macroinvertebrates were recorded. The upper reach of the stream was the most polluted with the presence of biological indicators of poor water quality, while the lower reach recorded some biological indicators of good water quality. Although the upper reach recorded the highest gross primary productivity, the highest net primary productivity was recorded at the stream’s lower reach. Water quality typically decreased from the upper reach of the stream towards the middle reach but later picked up at the lower reach before discharging into River Oba. The physico-chemical and biotic nature of the different reaches were a reflection of human activities in and around the stream. Keywords : Benthic macroinvertebrates, conservation, headwater stream, plankton; primary productivity, water quality.

This study investigated the relationships between zooplankton fauna and physico-chemical water parameters of Tiga Lake, Kano, Nigeria from March 2009 to March 2011. Water transparency, pH, Cl - , SO 4 2- and dissolved oxygen (DO) showed significant positive correlations (p

A five day survey was carried out to assess the odonate fauna associated with the riverine sections of two forests (Kribi Forest and Campo Ma’am National Park) of southern Cameroon. The primary objective of the study was to determine the species composition and community structure of the odonate fauna occurring in the forests. The goal is to infer the health status of the two forests. Three study sites were selected, one in each of the main water bodies in the forests (Rivers Kienke and Linde in Kribi forest, and River Bitande in Campo Ma’am National Park). All the specimens collected were identified to the lowest taxonomic level. A total of one hundred and ninety four (194) individuals of Odonata were collected in the forests comprising 10 families, 24 species of Anisoptera and 30 species of Zygoptera. Anthropogenic activities were less prevalent at Campo Ma’am National Park, an area in which all the 10 families were incidentally recorded. The community structure of the southern forest revealed that only River Bitande with Shannon-Wiener diversity index (H`) of 3.80 was having a stable environmental condition. Others were close to stable condition (River Kienke H` 2.99 and River Linde H` 2.95) with mild disturbance caused by human activity. Simpson index range (0.94 – 0.98) at the three study sites revealed that the vegetation was matured and stable. The distribution of dragonflies and damselflies revealed a stable environment (Evenness 0.90 – 0.95). Kribi Forest appears to be more impacted by anthropogenic activities as fewer (six) families were recorded there. The relative distribution of the species in the two forest ecosystems seemed to have some relationship with human interference therein. Key Words : Damselfly, Dragonfly, Diversity, Forest, River

The hydrology and water quality of Aiba stream were investigated from November 2012 to April 2013 on monthly basis. This was with a view to assessing the status of the stream sequel to its last study which indicated a poor physico-chemical water quality. Four sampling stations were established for the study along the longitudinal axis of the stream, covering both the upper and lower reaches. Hydrological input from the upstream reservoir was observed to be considerably low during the dry season, a situation which further exacerbated the water quality as indicated by very low dissolved oxygen concentration, high BOD5, high conductivity value and high ionic concentrations. High nutrient (PO 4 3- and NO 3 - ) level recorded in this study indicated a eutrophic freshwater system. Generally, the physico-chemical nature of the water in the dry season indicated that the stream fell short of the standards required for freshwater life. Urgent steps need to be taken to mitigate the impacts of natural and man-induced stresses on the stream in order to safeguard the ecosystem and the surrounding terrestrial ecosystems. Keywords : channel width, discharge, flow velocity, hydrological characteristics, lotic system, spatio-temporal, stress, water quality