Cross River System Research Articles

Assessing Ecosystem Health: A Comparative Study Using Water Quality Index Analysis across Ten Lotic System in the Cross River System

This review synthesizes findings from 10 scientific publications utilizing the weighted arithmetic Water Quality Index (WQI) to assess the status of diverse water bodies (Ikpa River, Lower Enyong Creek, Nwaniba River, Imo River, Etim Ekpo River, Lower Qua Iboe River, Ibeno Estuary, Cross River, Ikot Ebak River and Oboroenyin River) all within the Cross River System. The Analysis reveals that 6 out of 10 sampled water bodies are moderately polluted, while the remaining 4 exhibit slight pollution levels. These findings underscore significant concerns regarding water quality degradation, predominantly attributed to industrial effluents, agricultural runoff and urban contaminants. The WQI proves effective in consolidating multiple water quality parameters into a comprehensive index, facilitating a holistic assessment of pollution levels and guiding management strategies. Moving forward, concerted efforts are imperative to enhance monitoring efforts, implement stringent regulatory measures, and adopt sustainable practices to safeguard freshwater resources globally. This review underscores the urgency of integrated approaches to mitigate pollution and ensure resilience of aquatic ecosystems and public health.

Geochemical Characterization of the Sources and Distribution of Fatty Acids in Recent Sediment Cores from Cross River System, South-South, Nigeria

Geochemical Characterization of the Sources and Distribution of Fatty Acids in Recent Sediment Cores from Cross River System, South-South, Nigeria

Biodiversity of Fishery Resources of the Cross River System: Implication for Conservation and Management

This study aimed to assessing the biodiversity of fishery resources of the Cross River System with implication for conservation and management Sampling was carried out once a month for twelve months January to December with fish gears such as cast net drift net gill net local traps and hook and line Twenty six genera of fish were identified belonging to families consists of individuals collected from all the stations The most dominant families were Clupeidae and Cichlidae with respective relative abundance of and while the family Osteoglossidae was the least contributing only to the fish taxa For seasonal distribution Mugilidae Clariidae Cichlidae Gobiidae and Sciaenidae were abundant in both wet and dry seasons while Clupeidae Bathyclupeidae Carangidae and Sphyraenidae were low in wet season but high in dry season There was no significant seasonal difference p gt in fish biodiversity and abundance Like other water bodies in the Niger Delta the Cross River system was found to possess desired potential for fisheries exploitation considering its high fish species diversity composition and abundance Although pollution level was not measured in this study the continuous discharge of wastes effluents into the aquatic ecosystem may pose deleterious effect on the biodiversity and abundance of the resident biota Therefore to ensure sustainable biodiversity conservation and management of fishery resources there is need for stringent regulation and prevention of untreated wastes effluents discharged from households farms and industries into the aquatic environment

Polycyclic aromatic hydrocarbons in three commercially available fish species from the Bonny and Cross River estuaries in the Niger Delta, Nigeria.

The concentrations and compositional patterns of the USEPA 16 polycyclic aromatic hydrocarbons were investigated in three commercially available fish species, Chrysichthys nigrodigitatus, Cynoglossus senegalensis and Polydactylus quadratifilis, from the Bonny and Cross River systems in the eastern Niger Delta of Nigeria. The objective of the study was to provide useful information on the levels and sources of polycyclic aromatic hydrocarbons (PAHs) and the associated risks with their consumption. The 16 PAHs in the fish samples were extracted by ultrasonication with hexane/dichloromethane, and the concentrations of PAHs in the extracts were quantified by gas chromatography-mass spectrometry. The measured concentrations of the Ʃ16 PAHs in Chrysichthys nigrodigitatus, Polydactylus quadratifilis and Cynoglossus senegalensis ranged from 106 to 491, from 43.1 to 1734 and from 96.4 to 937μgkg(-1) in the Bonny River system and from 20.0 to 975, from 24.7 to 506 and from 24.9 to 387μgkg(-1) in the Cross River system, respectively. The compositional patterns of the PAHs showed that the three- and four-ringed PAHs were the major contributors to the PAH burden in these fish species. The diagnostic ratios indicate that the PAHs in these fish samples originated mainly from combustion processes. The health risk assessment, as determined from the benzo[a]pyrene potency equivalent factor, margin of exposure and incremental lifetime cancer risk, indicates that PAHs in the majority of these fish species can induce potential carcinogenic effects.

The Pathology of Nematode Infection in Parachanna obscura (Pisces: Channidae Gunther, 1886) of the Cross River System, Nigeria

The Pathology of Nematode Infection in Parachanna obscura (Pisces: Channidae Gunther, 1886) of the Cross River System, Nigeria

POPULATION DYNAMICS OF Chrysichthys nigrodigitatus (Lac�pede, 1803) IN LOWER CROSS RIVER, NIGERIA

Silver catfish Chrysichthys nigrodigitatus (Lacepede, 1803) constitutes the main fishery offering diversified livelihood to the artisanal communities in southeast Nigeria and has been heavily fished over time without attempts at conservation. This study was conducted to estimate the current population parameters needed for its rational exploitation. Estimates of growth and mortality of catfish in the Lower Cross River, Nigeria, were obtained from length-frequency data of 6637 individuals collected on monthly basis from November 2011 to October 2012. The estimated von Bertalanffy growth function (VBGF) parameters were: asymptotic length L∞ = 120.23 cm total length, growth coefficient K = 1.50 year-1 and age at zero length, t0 = 0.0 years. The amplitude of growth oscillations C = 0.75, winter point WP = 0.50 or 1 July and growth performance index, φ = 4.336. The rates for natural, fishing and total mortalities were: M =1.58, F = 2.55 and Z = 4.31 per year, respectively. This study reveals growth overfishing and threat of extinction of C. nigrodigitatus in the Lower Cross River system characterized by heavy fishing pressure on the length group 34.5 - 94.5 cm TL, reduced life span from 5 to 2 years, change from a slow growth pattern typical of siluroids to a fast one with current exploitation rate, Ecur (F /Z) = 0.62, about 15.8% higher than the allowable maximum exploitation rate, Emax = 0.522. In order to restore ecosystem health, a community-based multisectoral stakeholder consortium invested with limited equity and access for exploiting the fishery in tandem with its bio-ecological dynamics should be encouraged. Other policy instruments such as periodic prohibition of fishing, controlled pricing and public education are recommended for the sustainability and conservation of the fisheries.

Phthalates and Other Plastic Additives in Surface Sediments of the Cross River System, S.E. Niger Delta, Nigeria: Environmental Implication

Quantitative determination of phthalates and other plastic additives was carried out using GC-MS in order to understand the distribution and fate of these compounds in surface sediments of the Cross River System. Results show the concentration ranges (mean±standard deviation) of the three phthalates as: di(ethylhexyl)phthalate (DEHP; 1.97– 86.76 [24.06 ± 29.88 mg/kg dry weight dw]); di(n-butyl)phthalate (DnBP; 0.16 – 17.41 [3.25 ± 5.03 mg/kg dw]); di(isobutyl)phthalate (DiBP; 1.14 – 29.64 [9.82 ± 10.23 mg/kg dw]). However, examination of n-hexane procedural blank (used also in the study for clean-up protocol) GC trace revealed the presence of certain amounts of DEHP and tris-2,6-di(t-butyl)phenylphosphite (PhP) which interfere with the targeted analytes. Therefore, extract/blank (E/B) ratios were calculated and were in the range 1.05 – 12.54, indicating that the concentrations of DEHP and PhP previously assigned to the sediments were partly derived from laboratory artifacts. Differences in grain size distribution, partitioning behavior, volatility and solubility in the aqueous phase as well as localized influx may account for the observed spatial variation of phthalates and other plastic additives in the river system. The primary sources of these phthalates and tris-2,6-di(t-butyl)phenylphosphate (PhP’) were considered to be the result of direct discharge of untreated effluent/solid waste and emission arising from burning of refuse containing plastic materials, respectively. The occurrence of certain anti-oxidant degradation products in sediments (not in the blank) such as 2,6-di(t-butyl)-4-hydroxybenzaldehyde (HBA) and 2,6-di(t-butyl)quinine (Qn) and PhP’ (a compound proposed here as a possible marker for plastic combustion for the region/air basin), suggests that phthalates contamination had occurred before sample contact with laboratory artifacts.

Biomarkers in surface sediments from the Cross River and estuary system, SE Nigeria: Assessment of organic matter sources of natural and anthropogenic origins

Herein, lipid biomarker analysis is applied to surface sediments from the southeastern Niger Delta region for the quantitative determination of aliphatic lipids, steroids and triterpenoids in order to differentiate between natural (autochthonous vs. allochthonous) and anthropogenic organic matter (OM) inputs to this deltaic environment. This ecosystem, composed of the Cross, Great Kwa and Calabar Rivers, is receiving new attention due to increased human and industrial development activities and the potential effects of these activities impacting its environmental health. While the presence of low molecular weight n-alkanes (<C22) and the fossil biomarkers pristane and phytane in all samples, are indicative of a minor petroleum related input, the total extractable organic component of the surface sediments of these rivers remains predominantly of a natural origin as characterized by the variety and predominance of lipid classes that are mainly derived from the epicuticular waxes of vascular plants and include n-alkanes, n-alkanols, n-alkan-2-ones, n-alkanoic acids, steroids and triterpenoids. In addition, recent OM inputs from microorganisms are indicated by the presence of lower molecular weight n-alkanoic acids (Cmax=16), while the major triterpenoids of the sediments, taraxerol and friedelin, and the major sterol, sitosterol, indicate recent OM inputs from vascular plants. Plankton-derived sterols, such as fucosterol and dinosterol, are also found in sediments from the Cross and Great Kwa Rivers and likely originate from autochthonous primary productivity. Furthermore, the coprosterols coprostanol and 24-ethylcoprostanol are present in most samples and indicate measurable anthropogenic contributions from domestic untreated sewage inputs and agricultural run-off, respectively. Of the three rivers studied, the Cross River system was excessively influenced by human and industrial development activities, including drivers such as urbanization and population center growth, land-use change to support agricultural production and animal husbandry, and petroleum exploration and production. These influences were found to be regionally specific as controlled by point sources of pollution based on the relative distributions measured and on the fact that the molecular characteristics of sedimentary OM were not distributed smoothly along a gradient.

Food and feeding habits of Ophiocephalus obscura (African snakehead) in the Cross River estuary, Cross River State, Nigeria

Studies conducted on the food and feeding habits of Ophiocephalus obscura in the Cross River estuary, Cross River State, Nigeria, between February and April, 2009 revealed that the species feed mostly on food from animal origin, although diatoms and other plant materials were also identified. A total of 149 plant materials (15.95%) and 77 diatoms (8.24%) were consumed by the species. Food from animal origin consumed by the species included polychaete worm 110 (11.77%), shrimps 84 (8.99%), shrimp parts 33 (3.55%), juvenile fish 33 (3.33%), fish bones 44 (4.71%), fish scales 40 (4.28%), bivalves 61 (6.53%), insect larvae 2 (0.21%), adult insects 2 (0.21%), daphnia 62 (6.63%) and water snails 2 (0.21%). The condition factor calculated for the species varied during the study period with a mean value of 2.09 in February, 1.05 in March and 0.76 in April. Based on the food items isolated from the gut of the O. obscura, the species could be considered as a voracious carnivore in the Cross River system, while the variations in the condition factor of the species in the river system may indicate a period of high yield or otherwise of the species in the river system. Key words: Food, feeding habits, Ophiocephalus obscura, Cross River estuary.

Dynamics of the limnological features and diversity of zooplankton populations of the Cross River System SE Nigeria

Physico-chemical factors and zooplankton diversity were investigated over a two year period in three regions along the 200 km length of Cross River. The objective of the study was to quantify the relative importance of local environmental conditions and diversity of the principal zooplankton species within sampling sites. Mean conductivity, TDS and chlorides were highest upriver with values 289 ± 198 µs·cm–1, 322.9 ± 101 mg·L–1, and 105.8 ± 77.3 mg·L–1 and lowest downriver with 123.5 ± 78.9 mg·L–1, 45.8 ± 23.7 mg·L–1 and 109 ± 89 µs·cm–1 respectively. Values of wet season water conductivity (406 ± 178 µs·cm–1), TDS (420.4 ± 267 mg·L–1), alkalinity (289.9 ± 34.7), total hardness (205.8 ± 37 mg·L–1), BOD (1.7 ± 0.2), chlorides (205.8 ± 37) and ammonium ions (0.2 ± 0.1 mg·L–1) were significantly higher than dry season values of 156 ± 78.5 µs·cm–1, 0.2 ± 0.1, 123.8 ± 15, 101.4 ± 87.9, 0.2 ± 0.1, 78.1 ± 34.8 and 0.1 ± 0.1 mg·L–1 respectively. Out of twenty seven (27) zooplankton species identified Cladocerans (Ceriodaphnia, Evadne, Alona sp.) and Decapods (Lucifer, Penaeid nauphlius, and Hermit crab larva) were the most diverse taxonomic group, while Tintinnopsis was the only Ciliate. Rainfall value was positively correlated with hydrological characteristics (size of river, flow velocity, water level, and transparency), which in turn determined values of physico-chemical properties and explained the observed seasonal and spatial changes in zooplankton diversity. Though water quality parameters were within the limits set by the World Health Organization (WHO) and European Economic Community (EEC) for good water, the changes in hydrological features of Cross River could be suspected to provide highly unstable aquatic habitat that could subsequently affect the stability of zooplankton and other aquatic organisms.

Fish Species Used as Biomarker for Heavy Metal and Hydrocarbon Contamination for Cross River, Nigeria

Enhanced concentrations of Fe, Zn, Mn, Pb, Cu, Cd and total hydrocarbons (THC) determined in fish samples from the Cross River system, Nigeria have been associated with clinical defects (nausea, headache, hepatitis, body rashes) observed in coastal residents who are the major consumers of the fish species. Fish samples were collected from ten locations with varying degrees of exposure to human activities. Heavy metal concentrations in fish followed the sequence: Fe>Zn>Mn>Pb>Cu>Cd with the highest concentration of 243 μg/g (Fe) wet weight occurring in Tympanotonus sp. Fe levels were significantly (P E. fimbriata > P. elongatus > Portonus sp. > C. nigrodigitatus > Tympanotonus sp. Generally, the demersal species showed a marked potential for tolerating high levels of heavy metals while the pelagic species showed preference for the accumulation of hydrocarbons. The degree of contamination depended on pollutant type, fish species, sampling location, trophic level and their mode of feeding. The persistent accumulation and tolerable potential of Tympanotonus, Portonus and P. elongatus suggest that they might be effectively utilized as self-integrating indicators for time-series monitoring of the rate of recovery of the impacted ecosystem by heavy metals. Possible sources of pollutant include leachates from municipal dumps, used crankcase oils from fluvial discharges (mechanic workshops) and occasional oil spills.

A seminal study of the dynamics of a mudskipper (Periophthalmus papilio) population in the Cross River, Nigeria

A seminal study was conducted in which the population dynamics (growth, mortality and recruitment) of the mudskipper (Periophthalmus papilio) in the Cross River, Nigeria, was elucidated for the first time using length frequency data and the ELEFAN software. The allometric relationship was: Weight=0.012(Length)2.940, n=415, r2=0.939, P <0.0005. The seasonalized Von Bertalanffy growth parameters were L∞=19.39 cm, K=0.51 y−1, C=0.3, and WP=0.4. The instantaneous total mortality coefficient Z was 2.208 y−1 while the instantaneous natural mortality coefficient was 1.341 y−1. The instantaneous fishing mortality coefficient of 0.867 y−1 yielded the expectedly low exploitation rate E of 0.393. Our estimate shows that the species could reach an average maximum life span of about 6 years in the Cross River system. These results are used in quantitative elucidation of the state of exploitation of the population and will serve as input for the proper and scientific management of the fish resource.

Growth, biomass, mortality, production and potential yield of the West African clam, Egeria radiata (Lamarck) (Lamellibranchia, Donacidae) in the Cross River system, Nigeria

An important fishery for the West African hemi-estuarine clam, Egeria radiata exists in the lower reaches of the Cross River (CR) system. The stock is heavily exploited but its productivity and potential yield have not been studied. This paper discusses the distribution and ecology of, and presents data on growth, abundance, mortality, biological production and potential yield of the CR stock of E. radiata based principally on length structured relative age. Growth was exponential and conformed to the von Bertalanffy's growth model (VBGM), with the parameters L∞ = 9.3 cm, K = 0.36 and To = −0.10 year. The instantaneous total mortality coefficient (Z) by the catch curve method was 0.82 yr−1; natural mortality coefficient (M) was estimated at 0.32 yr−1. Total mean biomass computed from data obtained in two month's grab sample surveys in the area of occurrence of E. radiata was 1923 kg ha−1 for total (i.e. flesh + shell) and 628 kg ha−1 for flesh (i.e. shell-free) production units. The production-to-mean-biomass (or P/B ratio, R′) were 0.31 and 0.52 for total and shell-free production units respectively. The maximum sustainable yield (Ymax) was estimated at 398.4 kg ha−1 for total and 112.2 kg ha−1 for shell-free production units. With an exploitation ratio (E) of 0.61 and an estimated present catch rate of 1970 tonnes(t) yr−1 total weight (or about 82% of Ymax) the Egeria stock of the CR is currently being fished above the level of its optimum yield. Much of the fishing pressure is on the very young clams, thus lowering the age at first capture (Tc) to 1 year. This is an unhealthy situation for a species with limited area of distribution and low (< 1.0) P/B ratio; it can lead to rapid extinction of the stock if for some reason there is a substantial reduction in annual recruitment. It is recommended that in order to conserve this valuable resource and keep it at a level of sustained optimum yield, there should be a regulation prohibiting the landing of young clams (< 6.0 cm shell length). Furthermore the fishermen should learn to cultivate the animal by transplanting the young clams to new beds upstream to give them time to grow larger before harvesting. This type of management has been practised in Ghana for a long time and has helped to conserve the Egeria stock of the Volta River. The need for a continuous monitoring of the effluents from the Nigerian Newsprint Manufacturing Company's factory located at the bank of the CR in the centre of the clam industry is stressed; such monitoring would ensure that dangerous toxic chemicals are not discharged into the river to damage the Egeria industry.