Qua Iboe Estuary Research Articles

Quantitative and Qualitative Assessment of Hydrocarbon-Degrading Bacteria and Fungi in Qua Iboe Estuary, Nigeria

Quantitative and Qualitative Assessment of Hydrocarbon-Degrading Bacteria and Fungi in Qua Iboe Estuary, Nigeria

Microalgae biodiversity and biomass status in Qua Iboe Estuary mangrove swamp, Nigeria

Microalgae composition, abundance, diversity and biomass of the Qua Iboe Estuary mangrove swamp were studied. The results revealed the rich assemblage of the brackish ecosystem. Six major taxanomic classes were encountered. These were the Bacillariophyceae, Cyanophyceae, Chlorophyceae, Chrysophyceae, Euglenophyceae and Phaeophyceae. Their composition, abundance and diversity exhibits strong seasonal variation. Variations between pelagic and sedimentary habitats were also noticed. The diatoms (Bacillariophyceae) dominated the habitats. Actinoptychus undalatus, Navicula radiosa and Amphora ovalis co-dominated the pelagic water column; while the epipellic (intertidal) and benthic (subtidal) sediments were co-dominated by A. ovalis and Actinoptychus undulatus. Analyses of the Shannon’s index of general diversity (H1), McArthur-Terborgh species equitability index (E) and Simpson’s index of dominance (D) of the microalgae communities revealed that A. ovalis with a mean H 1 -value of 0.25, E-value of 0.08 and D-value of 0.05 was the most prevalent genus in the mangrove ecosystem despite its uneven distribution. The densities of the microalgae communities corresponded with their biomass statuses and were seriously impacted by oil spillage. This forms the basis of concern because the estuary is associated with a high probability of major oil pollution with serious consequences for ecological stability and fisheries.

Productivity and Distribution of Epipellic Microalgae Along Salinity Gradients in Mangrove Swamp of the Qua Iboe Estuary (NIGERIA)

Based on spatial variation in tidal mud salinity, direct gradient analysis procedures were adopted to relate the productivity and distribution of epipellic microalgae along salinity gradients in mangrove swamp of the Qua Iboe Estuary. Variations in mud salinities were due to distance from the coast, tidal incursions and freshwater input. The dilution effect of fresh water input from rainfall, urban runoff and associated freshwater creeks was most severe during the rainy season month of July, with much lower salinity levels recorded, in comparison to higher salinity values, recorded for same sampling locations during the drier month of December. In the dry season, all the microalgae species but Closterium (a genus of soft, green algae) and Oscillatoria (a cyanobacterium) species encountered in the tidal mud flats showed statistically significant negative correlations with salinity, while most microalgae species excluding Oscillatoria and Closterium species were positively correlated with the same factor during the wet season. Four Ecological Groups of microalgae, were established in the dry season month of December as against two Ecological Groups in the wet season month of July. However no microalgae species was found to occur on the highest values of mud salinity and there were overlapping range of occurrences and ecological optima for most species along the gradients.

Microbial Population Dynamics as a Function of Sediment Salinity Gradients in the Qua Iboe Estuary Mangrove Swamp (Nigeria)

In this investigation the extent to which sediment salinity gradients can be used to predict the sensitivity of microbial populations in mangrove ecosystem was investigated. The microbial groups monitored were heterotrophic bacteria, coliform bacteria, actinomycetes, fungi and yeasts. Pearson's Product-Moment Correlation (r) analyses were done on Log10-transformed estimates of population densities. The values obtained from the intertidal (epipellic) and subtidal (benthic) sediments were less than the critical value of 0.707 (n=8, p=0.05). This indicates that salinity was less closely related to the microbial population densities. A positive but insignificant relationship was found for fungi (r=0.03) in intertidal sediment. The total heterotrophic bacteria (r=-0.69), coliforms (r=-0.54), actinomycetes (r=-0.43) and yeasts (r=-0.56) were negatively affected by salinity in epipellic sediment. But in the benthic sediment, total heterotrophic bacteria (r=0.55) and unexpectedly, the fungi (r=0.58) and actinomycetes (r=0.29) exhibited positive but insignificant correlations while coliform and yeast counts in the benthic sediments were negatively influenced by salinity. However the coefficient of determinations (R2) revealed that total heterotrophic bacteria (48.06%) and yeasts (31.18%) were more extensively distributed in the intertidal sediments than coliforms. (29.38%,actinomycetes (18.68%) and fungi (0.09%). In contrast, the fungi (33.48%) demonstrated a wider distribution in benthic sediment. This may be ascribed to their existence, mostly as dormant, but culturable spores in the anoxic bottom sediment. The weak relationship exhibited by coliforms further confirms their usefulness as indicator of faecal contamination in estuarine ecosystem.

Negative effects of oil spillage on beach microalgae in Nigeria

In a concerted effort to apply epipsammic microalgae indices as a biological indicator of crude oil pollution and natural remediation in a tropical estuarine environment, the direct effect of a recent oil spill on the abundance of microalgae in the coastal shore of the Qua Iboe Estuary was investigated. A significant negative effect of contamination on the salinity, acidity and nutritive salts (CO32−, Cl−, and SO42−) levels of the sandy beach soil was observed. The Biological Index of Pollution (BIP) of the beach soil was raised from the previous slightly polluted level (18%) to 75, 88, 45 and 41% after contamination, at sampling distances of 5.5, 9.5, 11.5 and 15 m from the barrier used for pollution control. These corresponded with increases in the density of microalgae with distance from the barrier. This implies that the effect of oil pollution was more severe on microalgal cells that are close to the barrier. The overall effect was a distance-influenced reduction in the regeneration capabilities of the epipsammic microalgae. Some microalgal species, particularly the cyanobacterial species of Aphanizomenon flos-aquae, Lyngbya majusculata,and a centric diatom Actinoptychus undulatus may have been exposed to contamination levels exceeding normal homeostasis and compensation. They lost their existence in the sandy beach, and their absence is recommended for use as an indicator of the short term effect of oil pollution in coastal sandy beaches in a tropical estuarine environment.

Epipellic Algae Profile of the Mixohaline Mangrove Swamp of Qua Iboe River Estuary (Nigeria)

The epipellic algae of Qua Iboe Estuary was studied in late summer (between January and February) of 1999. Physicochemical analysis of the tidal mud flats of the Estuary revealed a mixohaline habitat characterized by its high acidity (pH 4.72±0.02) and rich nutritive salts content. The results of the phytoplankton studies revealed variation in the density of the microalgae within the microalgal Orders. The epipellic algae community was predominated by pinnate diatoms. The mean densities of the phytoplanktons ranged from 102.75 organism/ha, 34.25 organism/ha, 21.25 organism/ha to 1.00 organism/ha of Pennales, Centrales, Zygnematales and Blue-Green algae, respectively. Their densities, however, decreased with increase in sampling distance from the low tide level. At the species level, Actinoptychus undulatus and Tabellaria sp. predominate the microalgae community. The occurrence of the freshwater diatom, A. undulatus, in an otherwise “harsh” salty epipellic habitat confirms the adaptive potential of some freshwater phytoplankton to marine ecosystem. Other phytoplankter present in the epipellic habitat of the estuary were Amphora ovalis, Campylodis cibrosus, Cymbella lanceolata, Navicular radiosa, N. rhynocephala, Pleurosignma sp., Pinnularia viridis, Stephanodiscus sp., Closterium sp., Oscillatoria nigroviridis and Nodularia spumigena.