Abstract
Biocides, such as formaldehyde (HCHO), sodium hypochlorite (NaOCl) and glutaraldehyde (C5H8O2) that are commonly used in thermal, desalination and power plants and industries were tested on the commercially important mullet fish, Liza klunzingeri to determine the environmental contamination in the stressed ecosystem of Kuwait Bay sites. Multi-factor Probit analysis toxicity tests (96 h) on L. klunzingeri showed the lowest observed effective concentration (LOEC) and median lethal concentration (LC50) with NaOCl (0.019 and 0.027 μg L-1) followed by HCHO (0.058 and 0.157 μg L-1) and C5H8O2 (0.056 and 0.072 μg L-1). Site-wise analysis in the absence of feed showed high biocides toxicity in L. klunzingeri reared in seawater from Site I when compared to Sites II-III. Experiments were conducted (2-9 months) by rearing fish separately in seawater collected from three Kuwait Bay sites to test the bio-accumulated toxicity levels at LOEC of biocides fed fish using Feed Conversion Ratio (FCR) calculation. The lowest FCR was observed in fish fed with biocides in the sequence of NaOCl (0.40-1.1) followed by C5H8O2 (0.91-1.2) and HCHO (0.92-1.3) as well as with fish reared in seawater from Site I followed by Site II and Site III. High FCR was recorded in control (1.2-1.6) without the addition of biocides. These results exemplify the use of L. klunzingeri as an indicator species and may characterize a better quantification of biocides bioaccumulation using FCR calculation in mullet fish.
Highlights
Environmental concern over the use of biocides stems from its use in desalination, power and thermal plants, cooling water disinfectant and antifouling paints
Unregulated discharges mainly from the thermal, power and desalination plants as well as from sewages caused deleterious effects to organisms in Kuwait marine environment[4]. Biocides such as glutaraldehyde (C5H8O2), formaldehyde (HCHO) and sodium hypochlorite (NaOCl) used mainly in the thermal and desalination plants as biocide, disinfectant, in medical application, oil and as solvents in various industries were discharged in the aquatic environment without any safety precautions[5,6,7,8,9,10]
Experiments were conducted to determine the accumulated biocide levels using feed conversion ratio (FCR). Biocides such as glutaraldehyde (C5H8O2), formaldehyde (HCHO) and sodium hypochlorite (NaOCl) were used in thermal, power and desalination plants (Sites I-III) in the Kuwait Bay respectively. These biocides added to the stressed ecosystem Kuwait Bay sites which was primarily affected as a result of untreated effluent discharges, fluctuating seawater variables, upwelling of water current, inorganic pollutants, influence of anthropogenic activities and harmful algal blooms
Summary
Environmental concern over the use of biocides stems from its use in desalination, power and thermal plants, cooling water disinfectant and antifouling paints. Biocides such as glutaraldehyde (C5H8O2), formaldehyde (HCHO) and sodium hypochlorite (NaOCl) were used in thermal, power and desalination plants (Sites I-III) in the Kuwait Bay respectively.
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