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The effects of physicochemical properties and attachment surface characteristics on biofilm formed in a cassava mill effluent of the polluted Oloshi River (Nigeria) was investigated. Concerning to physicochemical properties, the Total Dissolved Solids (TDS), Total Suspended Solids (TSS), and Dissolved Oxygen (DO) were significantly affected with higher values in the discharge point (DP) than in the downstream points (DS). Values for these properties in samples from upstream (US) sites were lower than in the DP, except for DO that was higher. Klebsiella spp., Corynebacterium spp., Moraxella spp., Acinetobacter spp., and Saccharomyces spp. were absent in the US, but were found from the DP though the DS. Regarding to the bioloads, DS I has presented the highest bacterial counts, followed by the DS II, while the lower counts were obtained in US. Again, in a general form, higher biofilm contents have been observed in DS I, followed by DS II, and lower in US. In all sampling sites, wood surfaces had the highest biofilm bacterial counts followed by the plastic surfaces before the glass and metallic surfaces. In that order, higher biofilm bacterial counts then water column counts were observed. The obtained results let us to infer that the availability of nutrients and the nature of attachment surfaces directly influence in the biofilm formation in such analyzed ecosystems.

Rivers are subjected to various kinds of natural and anthropogenic activities among which, indiscriminate and illegal sand mining is a major factor. The heavy metal content of a Nigerian river was studied between December 2017 and November 2018 in 6 stations in relation to suitability for human consumption using pollution indices. The indices used were Heavy Metal Pollution Index (HPI) and Contamination Index (Cd). Eight metals were evaluated using standard methods and compared with Nigerian Drinking Water Quality Standard. Some metals like iron, cadmium and lead exceeded limits; manganese, chromium and nickel exceeded limits in the dry season in some stations while copper and zinc were all within limits. The dry season values were significantly (P<0.05) higher than the wet season values. NPI showed all the stations exceeded the threshold (100) especially stations 1, 4 – 6 while Cd showed that stations 3 and 2 had low and medium contamination potential risks respectively and stations 1, 4 – 6 had high contamination potential risk. The indices effectively captured the effect of the anthropogenic activities (sand mining, swimming, washing, etc) in the river and showed that the water quality was not suitable for human consumption.

Certain anthropogenic activities have negative impacts on the aquatic ecosystems. Plankton are sensitive to their environment and are used to monitor anthropogenic impacts. A South-eastern Nigeria River was studied from December 2017 to November 2018 in 6 stations; to assess the plankton community, water quality and anthropogenic impacts. The river was subjected to intense sand mining activities among other activities. The plankton was sampled with filtration method while water was collected and analysed using standard methods. A total of 36 phytoplankton species and 27 zooplankton species were recorded with Chlorophyceae and Rotifers being the most abundant groups. The most abundant species - Melosira granulata (phytoplankton) and Daphnia pulex (zooplankton) are pollution indicators. Some of the physicochemical parameters showed that the river was perturbed by the anthropogenic activities in the watershed. However, the plankton assemblage and community structure gave an indication of a stable environment; though the zooplankton fauna showed some level of stress. The impacts of sand mining activities on water quality and plankton were more in the downstream stations (4–6) where sand mining was intense while perturbation from swimming children and related activities were observed in station 1 especially during the dry season. The presence of eutrophic indicators and tolerant species showed that the river was tending towards eutrophication. Sand mining activities contributed to the nutrient enrichment of the river. CCA showed the major water quality parameters that influenced the plankton community structure. There is need to regulate illegal sand mining activities in the river.

Abstract. Aquatic ecosystems and biota are often adversely affected by anthropogenic activities. Consequently, zooplanktons have been used to monitor anthropogenic impacts because of their sensitivity to their environment. Water quality and zooplankton community of the Eme River, Umuahia, was assessed between December 2017 and November 2018. The study was carried out in six stations in relation to human activities. Human activities in the watershed were dominated by sand mining. A quantitative filtration method was used for the zooplankton sample collection while standard sample collection and analytical methods were used for the water samples. The zooplankton species recorded were 27 while the most abundant zooplankton group was Rotifera. A known pollution indicator, Daphnia pulex, had the highest number of individuals. The effects of human activities in the watershed were reflected in the results of some of the physicochemical parameters of the river. The zooplankton assemblage and community structure also reflected the effects of human activities in the river. Combined effects of human activities and season contributed to the relatively low zooplankton abundance recorded particularly in some downstream stations. The impacts of sand mining on water quality and zooplankton were more remarkable in the downstream stations (4 6) where the activity was intense while a large number of children swimming and related activities during the dry season had some impacts in station 1. The dominance of indicator and tolerant species indicated that the river was undergoing eutrophication. Sand mining among other observed anthropogenic activities was a major contributor to the nutrient enrichment in the river. The major water quality parameters influencing the zooplankton community structure was revealed by canonical correspondence analysis.

Aquatic ecosystems respond differently to diverse anthropogenic activities in their watersheds. Phytoplankton is sensitive to their environment and is used to monitor anthropogenic impacts. A study was carried out in a South-eastern Nigerian River between December 2017 and November 2018 in 6 stations; to assess the phytoplankton community, water quality, and anthropogenic impacts. Sand mining was a major activity in the river among others. The phytoplankton was sampled with the filtration method while water was collected and analyzed using standard methods. A total of 36 phytoplankton species were recorded with Chlorophyceae being the most abundant group. The most abundant species - Melosira granulata is a pollution indicator. The water quality and phytoplankton structure showed that the water was tending towards eutrophication. This is attributed to the observed anthropogenic activities and cumulative impacts of all the activities in the watershed. The impact of sand mining activities was observed more in the downstream stations (4 – 6) while perturbation from swimming children and related activities was observed in station 1. The community structure reflected the impacts of the activities while CCA showed the major water quality parameters that influenced the phytoplankton community structure.