Organophosphate pesticide residue impact on water quality and changes in macroinvertebrate community in an Afrotropical stream flowing through farmlands.

River Chanchaga has experienced significant agricultural practices around its catchment, which involved the indiscriminate use of pesticides. However, residents of the study area are not well aware of the negative impact of pesticides on water quality and macroinvertebrates. In this study, the first report on the influence of organophosphate pesticide contamination on the abundance of the macroinvertebrate community was provided. Sampling for the determination of organophosphate pesticide residues was carried out during the peak of the two seasons, while macroinvertebrates and physicochemical variables were observed for 6 months. We examined 11 organophosphate pesticide residues using gas chromatography coupled with mass spectrometry, 12 water quality variables, and 625 macroinvertebrate individuals. The concentration of recorded organophosphate pesticide residues ranged from 0.01 to 0.52 µg/L. From the Canonical Correspondence Analysis plot, malathion, chlorine, and paraffin show a positive correlation with Unima sp., Hydrocanthus sp., Chironomus sp., and Potadoma sp. At station 3, depth shows a positive correlation with Biomphalaria sp. and Zyxomma sp., indicating poor water quality as most of these macroinvertebrates are indicators of water pollution. Diuron and carbofuran show a negative correlation with Lestes sp. and Pseudocloeon sp., and these are pollution-sensitive macroinvertebrates. The total mean concentration of organophosphate pesticide residues was above international drinking water standards set by the World Health Organization except for paraffin, chlorpyrifos, and diuron. In conclusion, the observations recorded from this research are useful in managing pesticide applications around the river catchment.

Stream ecosystem puzzle: understanding how water column and sediment variables shape macroinvertebrate patterns in some Afrotropical streams.

Although the interaction of water column and sediment variables in streams is intricate, minimal studies have been conducted on how they influence macroinvertebrate community patterns. This study, therefore, aimed to evaluate the influence of water column and sediment variables on macroinvertebrate community patterns in selected Afrotropical streams. Spatiotemporal scales of water column and sediment variables were analysed following standard methods while macroinvertebrates were sampled using the kick sampling technique. Redundancy analysis (RDA) and variation partitioning were used to assess the relationship of macroinvertebrates with water column and sediment variables. Significant differences were observed between seasons amongst water column variables such as total dissolved solids (p=0.046), turbidity (p=0.027), dissolved oxygen (p=0.011), chemical oxygen demand (p=0.002), bank vegetation (p=0.013), velocity (p=0.04), phosphates (p=0.031), and sediment variables such as total organic matter (p=0.01), pH (p=0.024), electrical conductivity (p=0.014). This accounted for the shift in biotic communities across the two seasons. In the studied area and seasons, Baetidae, Chironomidae, and Thiaridae were the most abundant families of macroinvertebrates representing 21.5%, 17.8%, and 6.9% of the 5266 recorded individuals belonging to 68 families. The water column was the most important predictor of macroinvertebrate community patterns (57%) compared to sediments (35%). Therefore, the use of both water column and sediment variables in ecological studies and biomonitoring should be emphasised because the two compartments provide complementary information. This enables researchers to gain a more complete understanding of the ecological health of aquatic habitats, useful in the development of effective management strategies.

Development of a macroinvertebrate-based biotic index to assess water quality of rivers in Niger State, North Central Ecoregion of Nigeria.

The increasing pollution of lotic ecosystems in sub-Saharan Africa, particularly in Nigeria, poses a threat to water quality, public health and biodiversity. It is therefore essential to develop appropriate tools and methods for monitoring these rivers, particularly in heavily affected areas, where these water resources are vital to the surrounding communities that are heavily dependent on them. To fill this gap, we propose to develop a multimetric index based on macroinvertebrates for the assessment of ecological quality of rivers in Niger State (NSRBI). Eighty-eight metrics were evaluated through a step-by-step statistical process (namely, range test and stability, redundancy test and relationship with abiotic variables), in which metrics that did not meet the conditions were excluded. At the end of this process, only four metrics (%Hemiptera, Diptera richness, Pielou equitability and % of very large individuals (size > 40 mm)) fulfilling all criteria were included in the index. These metrics were then scored on a continuous scale and divided into four water quality classes: "very poor", "poor", "fair" and "good". Evaluation of the performance of the index on test sites showed a correspondence of 90% between index result and environmental-based classification. Therefore, the NSRBI could be a valuable tool for monitoring and assessing the ecological conditions of rivers in Niger State and the North Central Nigeria ecoregion predominantly in urban and agricultural landscapes.

Fish and macroinvertebrate assemblages reveal extensive degradation of the world's rivers.

Rivers suffer from multiple stressors acting simultaneously on their biota, but the consequences are poorly quantified at the global scale. We evaluated the biological condition of rivers globally, including the largest proportion of countries from the Global South published to date. We gathered macroinvertebrate- and fish-based assessments from 72,275 and 37,676 sites, respectively, from 64 study regions across six continents and 45 nations. Because assessments were based on differing methods, different systems were consolidated into a 3-class system: Good, Impaired, or Severely Impaired, following common guidelines. The proportion of sites in each class by study area was calculated and each region was assigned a Köppen-Geiger climate type, Human Footprint score (addressing landscape alterations), Human Development Index (HDI) score (addressing social welfare), % rivers with good ambient water quality, % protected freshwater key biodiversity areas; and % of forest area net change rate. We found that 50% of macroinvertebrate sites and 42% of fish sites were in Good condition, whereas 21% and 29% were Severely Impaired, respectively. The poorest biological conditions occurred in Arid and Equatorial climates and the best conditions occurred in Snow climates. Severely Impaired conditions were associated (Pearson correlation coefficient) with higher HDI scores, poorer physico-chemical water quality, and lower proportions of protected freshwater areas. Good biological conditions were associated with good water quality and increased forested areas. It is essential to implement statutory bioassessment programs in Asian, African, and South American countries, and continue them in Oceania, Europe, and North America. There is a need to invest in assessments based on fish, as there is less information globally and fish were strong indicators of degradation. Our study highlights a need to increase the extent and number of protected river catchments, preserve and restore natural forested areas in the catchments, treat wastewater discharges, and improve river connectivity.

Animal manure as a biostimulant in bioremediation of oil-contaminated soil: the role of earthworms.

Human dire need for environmental sustainability have triggered researchers to seek for organic substrates as an alternative to synthetic fertilizers in order to enhance bioremediation. Presently, nitrogen-rich organic substrate not only proffered the solution but also have proven useful in enhancing the rate of bioremediation. Animal manure is a nitrogen-rich organic substrate which has been found very effective for stimulating plant growth. Some of the animal manure used by researchers are poultry droppings, cow dung, goat manure, and pig manure. In all the papers reviewed, it was gathered that animal manure enhances bioremediation by providing nutrients favoring microbial growth and activities responsible hydrocarbon degradation. However, of the four commonly used animal manure, poultry droppings was severally reported to be a better biostimulant. Also, animal manure when sun-dried and pulverized yielded better results. It was observed that animal manure serves as substrates for earthworms which further accelerates the potential of the earthworms to remediate the soil. Also, the pollution of soil by crude oil causes a surge in its carbon content which may slow down microbial growth and activities. Thorough review of literatures, however, indicates that animal manure is capable of providing appropriate nutrient concentrations to offset such imbalance. Studies continue to lay credence to the efficacy of animal manure in enhancing microbial growth and activities responsible for the biodegradation of hydrocarbons contained in crude oil. Furthermore, the co-application of animal manure with other bioremediation strategies, such as phytoremediation and vermiremediation, should be combined for effective bioremediation of oil-contaminated environment.

Development of lake macroinvertebrate-based multimetric index for monitoring ecological health in North Central Nigeria.

The use of organisms like macroinvertebrates in developing bioassessment tools, such as multimetric indices (MMIs), is gaining global recognition in monitoring the health status of lakes. The transition from traditional methods of physico-chemical parameters is due to the financial and time costs involved in their analysis while failing to provide accurate early warning signals on ecosystem conditions. Currently, there is scanty information on the use of MMIs in the conservation and management of lakes in Nigeria. This study aimed at developing a macroinvertebrate-based MMI to assess the ecological status of lakes in North Central Nigeria. The study was conducted on Tagwai and Old Gawu Lakes, from April to October 2022. Sampling sites were clustered based on organic pollution and categorized into reference (four) and impaired (four) sites. Out of 54 macroinvertebrate-based candidate metrics, only five were selected after discriminatory, stability, and redundancy tests (performed using R software). The final metrics were abundance of Ephemeroptera + Trichoptera; abundance of Coleoptera + Ephemeroptera; Gastropoda richness; Shannon Wiener index; and percentages of shredders + predators + scrapers, hereafter referred to as North Central Nigeria-Lakes Multimetric Index (NCN-LMMI). The NCN-LMMI values ranged as follows: 21-25, 16-20, 11-15, and 5-10 corresponding to categories I, II, III, and IV for water quality, as indications of good, fair, poor, and very poor ecological status of the lake, respectively. The developed NCN-LMMI will be a useful tool for aquatic resource managers and environmentalists to assess the ecological condition of lakes, mainly the North Central Nigeria municipal lakes.

Mouthpart deformities in Chironomidae (Diptera) as bioindicators of heavy metals pollution in Shiroro Lake, Niger State, Nigeria.

In this study, mouthpart deformities in Chironomid larvae (Diptera) were investigated in relation to sediment contamination in the Shiroro Lake in Nigeria. Metals and chironomids were sampled monthly at three stations (A-C) between August 2013 and January 2014. Across the stations, zinc ranged (3.9-75mg/g), manganese (1.29-1.65mg/g), lead (0.00-0.10mg/g), iron (101-168mg/g) and copper (0.13-0.17mg/g). The metal ions did not differ significantly (P > 0.05) between the sampling stations. However, zinc and iron ions were significantly different between the sampling seasons (P < 0.05). Thirteen chironomid species were recorded, with Chironomus sp., Polypedilum sp. and Ablabesmyia sp. dominating the assemblage structure. Mouthpart deformities were significantly higher at Station A compared with Station C, and seasonally significantly higher during dry season compared with wet season. Elevated incidences of deformity were recorded in Chironomus spp larvae as compared to other genera therefore for further studies in this region assessments should be based solely on Chironomus species and ignoring the rest. Strategies need to be developed to reduce the contaminations and the biological effects.

Anthropogenic impact on water chemistry and benthic macroinvertebrate associated changes in a southern Nigeria stream.

The Ogba River in southern Nigeria is an important water resource for its riparian communities. This study evaluates impact of anthropogenic influences on the Ogba River using water chemistry and macroinvertebrate data sets obtained over a period of 6 months between January and June 2012. Four stations, stations 1-4, characterised by various human activities were chosen along the river. Organic wastes from domestic and industrial sources were the major point sources of pollutants. Station 2 where the municipal wastewater drains into the river had elevated values of flow velocity, BOD5, sulphate, phosphate, nitrate and sodium. Based on the canonical correspondence analysis (CCA), 5-day biochemical oxygen demand (BOD5), sulphate, nitrate and phosphate were the main factors that help to shape the macroinvertebrate assemblage structure of the Ogba River. Macroinvertebrates clustered strongly by stations than by seasons indicating that water quality differences between the stations were responsible for the observed differences in the biotic assemblage. The preponderance of naidid oligochaetes, baetid nymphs and certain tolerant dipteran taxa including chironomids and ceratopogonids at all four stations was an indication that the entire water body was stressed. The odonates were the single most abundant taxa; their dominance could be attributed to the vegetative nature of the stream, favouring odonate colonisation. Overall, the responses of macroinvertebrates to stress were reflected by the different assemblage structures recorded at the four study stations. Substrate and microhabitat obliteration and poor water quality appeared to be the factors responsible for the observed assemblage structure in the Ogba River.

Agricultural-Derived organochlorine pesticide residues impact on macroinvertebrate community in an Afrotropical Stream.

This study evaluated the impact of pesticide application through agricultural activities in Chanchaga River, Nigeria, using macroinvertebrate data sets obtained for six months (September 2021-February 2022). Four (4) stations, characterized by various agricultural activities, were sampled along the river. Analysis of the water samples for organochlorine pesticide residues (OCP) using Gas Chromatography-Mass Spectrometry (GC/MS) at the peak of the two seasons revealed a high concentration of eleven isomers of organochlorine, which ranged from 0.01 to 0.81 µg/L, and a mean concentration that was above international drinking water standards set by the World Health Organization, the Federal Environmental Protection Agency, and the European Union. The mean concentration of detected OCP was recorded as DDT (0.72 µg/L), Dieldrin (0.59 µg/L), Paraquat (0.54 µg/L), Aldrin (0.49 µg/L), Metribuzin (0.48 µg/L), Butachlor (0.47 µg/L), Alachlor (0.28 µg/L), Atrazine (0.23 µg/L), Phenol (0.10 µg/L), Endrin (0.09 µg/L), and Benzene (0.08 µg/L). Atrazine, alachlor, metribuzin, aldrin, phenol, and endrin showed significant differences across the two seasons (p < 0.05), while dieldrin, butachlor, paraquat, benzene, and DDT showed no significant differences across the two seasons (p > 0.05). A total of 622 macroinvertebrate individuals from 19 species in 18 families from 8 orders were collected. More individuals were collected during the dry season (58.17 %) and the wet season (41.83 %). Canonical Correspondence Analysis (CCA) ordination revealed a strong relationship between species abundance and some organochlorine pesticide residues such as DDT, endrin, metribuzin, atrazine, benzene, and dieldrin. The response of macroinvertebrates to OCP indicates that Chanchaga River is a disturbed river, and the indicator organisms (Lestes sp., Coenagrion sp., Zyxomma sp., Appasus sp., Chironomus sp., Lymnaea natalensis, and Caridina nililotica) can also be used for further biomonitoring.

A review of the application of the macroinvertebrate-based multimetric indices (MMIs) for water quality monitoring in lakes.

The increasing stress on lake ecosystems is affecting their functioning such as providing goods and services to inhabiting organisms and riparian communities. Monitoring of water quality is important for sustainable management and restoration of lake ecosystems. However, the costs associated with traditional approaches have become prohibitive, while not giving reliable early warning signals on resource conditions. Thus, the current shift in the use of bioindicators and multimetric indices (MMIs) in the monitoring of water quality is currently gaining global recognition with more emphasis on its application in lotic ecosystems. Therefore, this paper provides an elaborated insight into the application of macroinvertebrate-based MMIs in lentic ecosystems and the successes achieved so far. The various metrics and indices, the development strategies, application challenges, the use of macroinvertebrates as bioindicators, and the future projection of enhancing MMI usage in lentic environment monitoring, particularly in developing countries, are extensively covered. The use of MMI as a rapid lake biomonitoring tool needs to be adopted for sustainable applications in lake ecosystem management and as an integrated approach to monitoring human-induced stress especially in developing countries where there is a paucity of information.

Spatiotemporal variation of macroinvertebrates in relation to canopy cover and other environmental factors in Eriora River, Niger Delta, Nigeria.

Canopy cover is well known to influence the distribution of macroinvertebrates in temperate streams. Very little is known about how this factor influences stream communities in Afrotropical streams. The effects and possible interactions of environmental factors and canopy cover on macroinvertebrate community structure (abundance, richness, and diversity) were examined in four stations in Eriora River, southern Nigeria bimonthly from May to November 2010. The river supported diverse macroinvertebrates in which the upstream sampling stations with dense canopy cover were dominated by Decapoda, Ephemeroptera, Odonata, Gastropoda, Trichoptera, and Coleoptera while Diptera and Coleoptera were the benthic organisms found predominant at downstream stations with less canopy cover. Some caddisfly species such as Agapetus agilis, Trichosetodes species and the stonefly Neoperla species were present upstream and were found to be potential bioindicators for a clean ecosystem. The blood worm Chironomus species and Tabanus sp. were abundant at the downstream of the river and are considered potential bioindicators for an organically degrading ecosystem. Some environmental factors varied temporally with significantly higher macroinvertebrate abundance and richness in May. We found out that canopy cover and environmental factors affected macroinvertebrates abundance, diversity, and richness and that the individual taxon had varying responses to these factors. These results help identify the mechanisms underlying the effects of canopy cover and other environmental factors on Afrotropical stream invertebrate communities.

Stream biodiversity and monitoring in North Central, Nigeria: the use of macroinvertebrate indicator species as surrogates.

Indicator species (IS) have been employed in modern aquatic research for monitoring of environmental changes and evaluating the efficiency of environmental management procedures. In this study, we evaluated the possibility of developing surrogate indicator groups as tools for the conservation and management of the biodiversity of Northern Nigeria streams by surveying 15 streams in Niger state for benthic macroinvertebrates and environmental variables as data sets, over a period of 24 months (2016 and 2017). Samples were collected in two locations of reference and impacted sites for each of the streams surveyed. The statistically significant (P < 0.05; based on 1000 permutations) indicator species for each of the status classes (reference versus impacted) was identified using the indicator species analysis/indicator value (Indval) method. Canonical correspondence analysis (CCA) was used to evaluate the IS-environment relationships. Indicator value found fifteen species for the reference streams including Ephemeropteran (Bugilliesia sp., Tricorythus sp., Thraulus sp., Crassabwa sp.) and the Tricopteran (Leptonema sp.). Opposite, the Indval found seven (7) indicator species for the impacted streams, which included the Dipteran (Pentaneura sp., Tabanus sp.). Multivariate analysis revealed that species assemblage had wide dispersal patterns in relation to the sites for both status classes. CCA revealed that the reference and impacted indicator species responded to entirely different environmental factors, indicating their preference to particular environmental variables along the ecological gradients. While the indicator species of reference sites were associated with environmental predictors of good water quality such as high DO, increased flow, low conductivity, and low BOD, the indicator species of impacted sites were strongly related to environmental predictors of anthropogenic pollution, including low DO, high BOD, and increased nutrients concentrations. This study has provided a reference point and effective tool to monitor environmental changes, community, and ecosystem dynamics across the Northern Nigeria streams.

Effects of effluent discharges from a cement factory on the ecology of macroinvertebrates in an Afrotropical river.

Cement factory waste water impacts on the ecology of macroinvertebrate assemblages of the Oinyi River, North Central area of Nigeria, were evaluated bi-monthly for 1 year as part of a study to understand the effects of pollution processes in the lotic system that may initiate the development of policy and improved regulation. Three sampling stations, each 100 m long, were selected along 11-km stretch of the river. Station 1, located upstream of the discharge point from the cement factory plant; station 2, immediately downstream of the effluent discharge point; and station 3, 4 km downstream, were sampled. The waste water from the cement effluent factory impacted negatively on the water chemistry by elevating the levels of some heavy metals (Mn, Zn, Cu, and Ni), and other physicochemical parameters such as turbidity, chemical oxygen demand (COD), conductivity, and total suspended solid. A total of 81 macroinvertebrate taxa combined were recorded from the river. The community structure, diversity, and abundance depicted distinct variation between the effluent-impacted site, and the upstream station as the most sensitive macroinvertebrate taxa such as Neoperla and Cheumatopsyche species was completely missing from the effluent-impacted site. The preponderance of some dipteran taxa (Tanypus sp., Eristalis tenax, Simulum sp., Empis sp., and Atherix sp.) and drastic reduction in the Ephemeroptera-Plecoptera-Trichoptera (EPT) organisms in the impacted station is an indication that the chemical components of the cement effluent waste water were lethal to some aquatic forms. Extrapolations from canonical correspondence analysis (CCA) results revealed that turbidity, conductivity, BOD, orthophosphate-phosphorus, and heavy metals were strongly associated with the impacted station. Generally, the community structure of station 1 was more diverse with more sensitive taxa, different from those of stations 2 and 3, which were prone to intense human activities. The need for careful consideration of the water quality and indicator organisms is important for restoration of this river.

Identifying and classifying macroinvertebrate indicator signature traits and ecological preferences along urban pollution gradient in the Niger Delta.

Urbanisation of riverine landscape is an increasing threat to the functionality of river ecosystems. In this study, we identify and classify macroinvertebrates indicator signature traits and ecological preferences.We hypothesised that urban pollution would differentially influence the distribution of macroinvertebrate traits and ecological preferences along a gradient of water quality deterioration. Hence, we identified and classified potential biological indicators traits and ecological preferences that were deemed tolerant of or sensitive to urban pollution gradient in the Niger Delta region of Nigeria. Physico-chemical variables (water temperature, depth, flow velocity, dissolved oxygen, biochemical oxygen demand, electrical conductivity (EC), nitrate, phosphate), and macroinvertebrates were collected from 2008 to 2012 seasonally during the wet and dry seasons once in a month in 11 stations in eight river systems. The results based on RLQ, fourth-corner and Kruskal-Wallis analyses indicate that traits/ecological preferences such as tegumental/cutaneous respiration, cased/tubed body armouring, a preference for silty water, bivoltinism, burrowing and a high tolerance for oxygen depletion, were statistically significantly associated with the heavily impacted stations. These traits were positively correlated with physico-chemical variables such as EC, nitrate and phosphate indicative of urban pollution. On the other hand, traits/ecological preferences such as permanent attachment, crawling, swimming, univoltinism and a moderate sensitivity to oxygen depletion were associated with the least impacted stations and were negatively correlated with physico-chemical variables indicative of urban pollution. Overall, the observed differential responses of traits and ecological preferences to urban pollution along a gradient of water quality impairment suggest that traits and ecological preferences can serve as useful biological indicators and thus supports the growing evidence of the utility of the trait-based approach.

The Biological Assessment and Rehabilitation of the World's Rivers: An Overview.

The biological assessment of rivers i.e., their assessment through use of aquatic assemblages, integrates the effects of multiple-stressors on these systems over time and is essential to evaluate ecosystem condition and establish recovery measures. It has been undertaken in many countries since the 1990s, but not globally. And where national or multi-national monitoring networks have gathered large amounts of data, the poor water body classifications have not necessarily resulted in the rehabilitation of rivers. Thus, here we aimed to identify major gaps in the biological assessment and rehabilitation of rivers worldwide by focusing on the best examples in Asia, Europe, Oceania, and North, Central, and South America. Our study showed that it is not possible so far to draw a world map of the ecological quality of rivers. Biological assessment of rivers and streams is only implemented officially nation-wide and regularly in the European Union, Japan, Republic of Korea, South Africa, and the USA. In Australia, Canada, China, New Zealand, and Singapore it has been implemented officially at the state/province level (in some cases using common protocols) or in major catchments or even only once at the national level to define reference conditions (Australia). In other cases, biological monitoring is driven by a specific problem, impact assessments, water licenses, or the need to rehabilitate a river or a river section (as in Brazil, South Korea, China, Canada, Japan, Australia). In some countries monitoring programs have only been explored by research teams mostly at the catchment or local level (e.g., Brazil, Mexico, Chile, China, India, Malaysia, Thailand, Vietnam) or implemented by citizen science groups (e.g., Southern Africa, Gambia, East Africa, Australia, Brazil, Canada). The existing large-extent assessments show a striking loss of biodiversity in the last 2-3 decades in Japanese and New Zealand rivers (e.g., 42% and 70% of fish species threatened or endangered, respectively). A poor condition (below Good condition) exists in 25% of South Korean rivers, half of the European water bodies, and 44% of USA rivers, while in Australia 30% of the reaches sampled were significantly impaired in 2006. Regarding river rehabilitation, the greatest implementation has occurred in North America, Australia, Northern Europe, Japan, Singapore, and the Republic of Korea. Most rehabilitation measures have been related to improving water quality and river connectivity for fish or the improvement of riparian vegetation. The limited extent of most rehabilitation measures (i.e., not considering the entire catchment) often constrains the improvement of biological condition. Yet, many rehabilitation projects also lack pre-and/or post-monitoring of ecological condition, which prevents assessing the success and shortcomings of the recovery measures. Economic constraints are the most cited limitation for implementing monitoring programs and rehabilitation actions, followed by technical limitations, limited knowledge of the fauna and flora and their life-history traits (especially in Africa, South America and Mexico), and poor awareness by decision-makers. On the other hand, citizen involvement is recognized as key to the success and sustainability of rehabilitation projects. Thus, establishing rehabilitation needs, defining clear goals, tracking progress towards achieving them, and involving local populations and stakeholders are key recommendations for rehabilitation projects (Table 1). Large-extent and long-term monitoring programs are also essential to provide a realistic overview of the condition of rivers worldwide. Soon, the use of DNA biological samples and eDNA to investigate aquatic diversity could contribute to reducing costs and thus increase monitoring efforts and a more complete assessment of biodiversity. Finally, we propose developing transcontinental teams to elaborate and improve technical guidelines for implementing biological monitoring programs and river rehabilitation and establishing common financial and technical frameworks for managing international catchments. We also recommend providing such expert teams through the United Nations Environment Program to aid the extension of biomonitoring, bioassessment, and river rehabilitation knowledge globally.

Mayfly (Insecta: Ephemeroptera) community structure as an indicator of the ecological status of a stream in the Niger Delta area of Nigeria.

Ephemeroptera is an important group of insects used in the bioassessment and monitoring of freshwater bodies worldwide because of their relative abundance in a wide variety of substrates and their increasing chances of detecting pollution impacts. In this study, their faunistic composition and spatiotemporal variations in density and diversity in River Orogodo (Southern Nigeria) was investigated at five ecologically distinct stations over a 12-month period. The mayfly nymph community responses to environmental variables were evaluated by means of biological measures and multivariate analysis (redundancy analysis [RDA]). Thirteen morphologically distinct taxa belonging to six families were identified. The dominant taxa were Afrobaetodes pusillus (23.1%), Baetis sp. (13.7%), and Caenis cibaria (11.4%). The density of Ephemeroptera differed significantly (p < 0.05) both in space and time. Diversity was influenced by substrate heterogeneity which in turn was influenced by catchment processes such as flooding and anthropogenic activities especially abattoir effluent. Based on the RDA ordination and relative abundance data, Baetis sp. dominated at impacted stations while a more equitable distribution of species were observed in less disturbed sites. Water velocity, canopy cover, nature of bottom sediments, and the amount of dissolved oxygen also accounted for the variations in Ephemeroptera densities at the different stations. Shannon diversity, taxa richness, and evenness were lowest in station 3 (the abattoir discharge site).

Developing and applying a macroinvertebrate-based multimetric index for urban rivers in the Niger Delta, Nigeria.

Urban pollution of riverine ecosystem is a serious concern in the Niger Delta region of Nigeria. No biomonitoring tool exists for the routine monitoring of effects of urban pollution on riverine systems within the region. Therefore, the aim of this study was to develop and apply a macroinvertebrate-based multimetric index for assessing water quality condition of impacted urban river systems in the Niger Delta region of Nigeria. Macroinvertebrate and physicochemical samples were collected from 11 stations in eight river systems. Based on the physicochemical variables, the stations were categorized into three impact categories namely least impacted stations (LIS), moderately impacted stations (MIS) and heavily impacted stations (HIS). Seventy-seven (77) candidate metrics were tested and only five: Hemiptera abundance, %Coleoptera + Hemiptera, %Chironomidae + Oligochaeta, Evenness index and Logarithm of relative abundance of very large body size (>40-80 mm) were retained and integrated into the final Niger Delta urban multimetric index (MINDU). The validation dataset showed a correspondence of 83.3% between the index result and the physicochemically-based classification for the LIS and a 75% correspondence for the MIS. A performance of 22.2% was recorded for the HIS. The newly developed MINDU proved useful as a biomonitoring tool in the Niger Delta region of Nigeria and can thus be used by environmental managers and government officials for routine monitoring of rivers and streams subjected to urban pollution.

The influence of sawmill wood wastes on the distribution and population of macroinvertebrates at Benin River, Niger Delta area, Nigeria.

The impact of sawmill wood wastes on the distribution of benthic macroinvertebrates at the Sapele section of Benin River, Niger Delta, Nigeria, was investigated from March 2005 to August 2005. A total of 434 individuals were collected by kick-sampling method, representing 21 taxa of benthic macroinvertebrates. Three stations, 1, 2, and 3, were selected from upstream of the site, receiving wood wastes discharge, the impacted site and its down stream, respectively. Among the water quality variables, conductivity, dissolved oxygen, biochemical oxigen demand (BOD(5)), nitrate-nitrogen, phosphate-phosphorus, transparency, and alkalinity were significantly different (P<0.05) among the stations. Orthogonal comparison by Duncan's multiple range test showed that station 2 (the impacted site) was the cause of the difference. More sensitive species such as Ephemeroptera or Plecoptera were completely absent from station 2, the impacted site. Species abundance was similar in station 1 and 3, indicating that the wood wastes must have adversely affected the distribution of these macroinvertebrates, especially the intolerant species. The wood waste discharge not only altered the water chemistry, but also stimulated the abundance of less-sensitive macroinvertebrate species.

Impact of rubber effluent discharges on the water quality and macroinvertebrate community assemblages in a forest stream in the Niger Delta.

The ecological impact of rubber effluent on macroinvertebrate communities of the Adofi River, Niger Delta area of Nigeria were evaluated for a 6 month-period as part of a study to understand pollution processes in the river that may lead to improved regulation and policy development. Three sampling stations, each 25 m long were selected along 7 km stretch of the stream. Station 1, located upstream of the outfall from the rubber processing plant, station 2, immediately downstream of the effluent discharge point and station 3, 3 km downstream were sampled monthly. The rubber effluent impacted negatively on the sediment and water chemistry by elevating the levels of some heavy metals (Ni, Pb, and Zn), chemical parameters as biochemical oxygen demand (BOD5), chemical oxygen demand (COD), conductivity and the amount of nutrients at the discharged site. A combined total of 87 macroinvertebrate taxa were recorded from the three stations of the river. The abundance and community structure showed variation between the effluent impacted site and the reference sites as most sensitive macroinvertebrate taxa were completely missing from the effluent impacted site. The preponderance of oligochaetes and some dipteran taxa associated with low dissolved oxygen levels in the impacted site bears credence to the fact that the chemical components of the rubber effluent waste water were lethal to some aquatic forms. Based on canonical correspondence analysis results, conductivity, BOD, phosphate and nitrate were strongly associated with the impacted station. At station 3, a community similar to the upstream reference station was found. Results illustrate the need for careful consideration of the water quality and indicator organisms in restoration. Mitigation procedures suggested for the rubber effluent included, for example, the decolourization of the highly coloured effluent and biodegradation prior to discharge, were recommended.

Relevance of Nematode Parasitic Burden in Channid Fishes of Orogodo River, Southern Nigeria to Organic Pollution.

Aims: To ascertain the gastrointestinal nematode burden on the channids, Parachanna obscura and Parachanna africana (Steindachner, 1879) (Family: Channidae) in the down reaches of Orogodo River at Evboesi and Ekwuoma-Abavo, southern Nigeria and its relationship to the levels of organic pollution. Study Design: A total of 220 channid fish were collected from two stations of the river experiencing different degree of organic pollution and dissected for gastrointestinal nematode parasites Place and Duration of Study: The study lasted for a period of six months (Jan to Jun 2010) with collections of fishes done monthly at two sampling stations of Orogodo River in southern Nigeria. Methodology: A total of 220 channid fishes were examined. Their stomachs and intestines were cut open and the contents were emptied into Petri dishes containing water and were examined for nematode parasites. These were quickly stained with Giemsa stain and viewed under a light microscope. Results: A total of 100 (45.5%) were infected with gastrointestinal nematode parasites. The prevalence of infection reveals that Parachanna obscura recorded 62.5% while Parachanna africana had 66.7% in fishes collected from station 1 and 20.1% and 28.6% respectively from fishes collected at station 2. The nematode parasites recovered were Cucullamus sp., Camallanus sp. and Procamallanus laevionchus. The overall parasitic burden reveals that the prevalence infection was statistically significant (p< 0.05) in the species examined. The distribution of infrapopulations of the parasites varied significantly with size class and weight of the fish peaking in most cases in larger size classes. The chemical parameters of the river water at station 1 showed the water to be stressed with high BOD and nutrients levels when compared with station 2. This may explain the high parasitic burden recorded in the channids at station 1. Conclusion: The intensity of the parasites in the host fish agree with previous hypotheses suggesting that environmental pollution does affect parasite population.