Direct toxic assessment of treated fertilizer effluents to Oreochromis niloticus, Clarias gariepinus and catfish hybrid (Heterobranchus bidorsalis x Clarias gariepinus )

Acute static bioassay was employed to assess the toxicity of various ranges of effluent from the National Fertilizer Company of Nigeria (NAFCON) plant to three fish species: Oreochromis niloticus, Clarias gariepinus and hybrid (Heterobranchus bidorsalis x C. gariepinus ) from the coastal estuaries of the Niger Delta area, Nigeria. The lethal concentration values at 24, 48 and 72 h were 72.05, 30.81 and 15.26% for O. niloticus and 26.18, 10.32 and 19.84% for the hybrid, respectively. No mortality was recorded for C. gariepinus. The median lethal time for O. niloticus at 70% and hybrid at 50% of the different samples was 18.14 and 6.02hrs, respectively. Ammonia appeared to be the major toxic component. The safe concentrations of the effluents ranged between 1.53% and 77.21% for O. niloticus, and 3.15 and 5.50 % for the hybrid. Although the ranges of treated effluents discharged from the plant met set standards and can be classified as non-toxic, yet they caused mortalities to exposed species. This underscores the merit of direct toxicity assessment of effluents over the traditional physicochemical method which does not adequately protect the environment.Key words: Toxicity assessment, fertilizer effluents, Oreochromis niloticus, Clarias gariepinus, catfish hybrid

Survey of heavy metals in the catfish Synodontis clarias

Elevated levels of heavy metals in the catfish Synodontis clarias can be a good indication of pollution of an aquatic ecosystem due to anthropogenic influence. The concentrations of Zn, Cd, Pb, Mn and Ni were determined in Synodontis clarias caught along a section of Taylor Creek and its associated tributaries. Samples were collected bimonthly between July 1999 and June 2000 in five stations. The metals: Zn, Cd, Ni, Pb and Mn were recorded in appreciable quantities, signifying their bioavailability. The levels of Zn, Cd, Ni, Pb and Mn may have obvious health implications on the rural communities that depend on fish species as fish supplement in view of its rich protein content and its bio-economic value. Generally, the sources of the metals in the catfish appear to be point and diffuse which include rural and agricultural runoff sources in the catchments area. However, the presence of an oil industry activity (Etelebou oil field and flow station) in one of its tributaries appears to be the major point source of the metal pollutants

Effect of Size on the Acute Toxicity of Crude Oil to the Mangrove Oyster, Carasostrea gasar

The acute toxic effects of a Nigerian crude oil (Egbogoro Liner II) to the mangrove oyster Carasostrea gasar were studied in bioassays. Tests were conducted over a 96-hr period after acclimatization of individuals in the laboratory, initially with a population comprising a broad size categories (11 - 60 mm) in range finding tests. The tests were semi-static bioassays in which the exposure media were replaced every 24 hours, at which the oysters were also examined for mortality. Subsequent experimentation was designed to compare the toxicities of oil to small (10 - 30 mm) and large (41 - 60 mm) oysters. LC50 values were obtained by graphical interpolation. Significant differences in effects at each time interval between small and large oysters were determined using the Man-Whitney tests on percentage mortality values. Relative toxicity tests showed consistently lower mortalities for small oysters at 24-hr, 48-hr and 96-hr periods, with Mann-Withney tests showing significant differences (

Haematological changes associated with crude oil ingestion in experimental rabbits

Blood cell profile among experimental rabbits associated with crude oil ingestion were evaluated and was significantly (P<0.05) altered. Erythrocytes decreased linearly (P<0.05) indicating an anemic condition. The decrease also affected dependable factors such as packed cell volume (PVC) and haemoglobin (Hb). Leukocyctes, the main defense cells of the animal decreased linearly (P<0.05) further indicating susceptibility of the animal to stress and infection. Granulolytic leukocytes, which include neutrophils and eosinophils increased linearly (P<0.05). This increase is a physiological response to stress. Lymphocytes, antibody forming leukocytes decreased linearly, indicating a response to stress and susceptibility of the animal to infection. Crude oil fraction present in the diet has serious consequences on hematological parameters in animals

Sublethal Effects of Ammoniacal Fertilizer Effluents on three Commercial Fish Species from Niger Delta Area, Nigeria

Sublethal effects of various concentrations of fertilizer effluents on the tail beat frequency per minute (TBF min.-1) and opercular beat frequency per minute. (OBF min-1) of Orechromis niloticus, Clarias gariepinus and hybrid (Heterobranchus bidorsalis (female) x C. gariepinus (male)) were examined in a static 96hr. bioassay under laboratory conditions. Effluent concentration, ammmonia (ionised and un-ionised), urea and pH significantly affected TBF and OBF of the three species. Ammonia particularly, the un-ionised form exacted the most significant effect on TBF and OBF. OBF appears be a more sensitive indicator of stress than TBF and may therefore be more suitable for detecting sublethal physiological effects of pollutants. This study further revealed that the fertilizer effluents have variable compositions whose values may far exceed the allowable limits and hence may pose great danger to the aquatic environment. Aquatic pollution is significant to fisheries and aquaculture industries. Studies have been conducted on the toxic effects of effluents (waste waters) on various commercial fish species (Wai-Ogosu 1987, Ojuola and Onuoha, 1987). Some of such studies were done with increasing interest in finding physiologic correlate of activity that can be monitored under field conditions (Thorpe, 1987). Investigations into the relationship of such parameters as heart rate, tail beat frequency and respiration rate with activity have been attempted (Ross et al. 1981). Changes in opercular rhythm have been documented as sensitive indicator of physiological stress in fish subjected to sublethal levels of pollutants (Davis, 1973). However, none of the above dealt with the toxicity of ammoniacal fertilizer effluents on tilapia and Clarias species which are common estuarine and pond – reared fish in Africa. This study investigates the sublethal effects of wastewater from a fertilizer company in the Niger Delta area of Nigeria on the tail beat frequency (TBF) and opercular beat frequency (OBF) of fingerlings of three commercial fish species – Oreochromis niloticus, Clarias gariepinus and hybrid (Heterobranchus bidorsalis (female) x C. gariepinus (male)). The information obtained from this study would be helpful in predicting the effect of effluent in the field

Full Length Research Paper - Direct toxic assessment of treated fertilizer effluents to Oreochromis niloticus, Clarias gariepinus and catfish hybrid (Heterobranchus bidorsalis ♂ x Clarias gariepinus ♀)

Acute static bioassay was employed to assess the toxicity of various ranges of effluent from the National Fertilizer Company of Nigeria (NAFCON) plant to three fish species: Oreochromis niloticus , Clarias gariepinus and hybrid (Heterobranchus bidorsalis ♀ x C. gariepinus ♂) from the coastal estuaries of the Niger Delta area, Nigeria. The lethal concentration values at 24, 48 and 72 h were 72.05, 30.81 and 15.26% for O. niloticus and 26.18, 10.32 and 19.84% for the hybrid, respectively. No mortality was recorded for C. gariepinus. The median lethal time for O. niloticus at 70% and hybrid at 50% of the different samples was 18.14 and 6.02%, respectively. Ammonia appeared to be the major toxic component. The safe concentrations of the effluents ranged between 1.53% and 77.21% for O. niloticus, and 3.15 and 5.50 % for the hybrid. Although the ranges of treated effluents discharged from the plant met set standards and can be classified as non-toxic, yet they caused mortalities to exposed species. This underscores the merit of direct toxicity assessment of effluents over the traditional physicochemical method which does not adequately protect the environment