Fish embryos are excellent models for studies aimed at understanding toxic mechanisms and indications of possible acute and chronic effects. For the past 3 yr, an Arabian killifish (Aphanius dispar) fish embryo test has been developed in the authors' laboratory as a routine ecotoxicological test that can be used to support risk assessment of potential contaminants in Arabian Gulf coastal waters. Tests were conducted with 3 reference toxicants (3,4-dichloroaniline [DCA], sodium dodecyl sulfate, and zinc sulfate [Zn]) and chlorine, a disinfectant used widely in industrial cooling systems around the Arabian Gulf region. The 50% effect concentration (EC50) for DCA was 0.47 mg/L and 1.89 mg/L for embryos exposed before 6 hpf and after 168 hpf, respectively. Sublethal effects were mainly observed at concentrations above 2.5 mg/L, the effects included severe pericardial edema and tail shortage. The sodium dodecyl sulfate ionic surfactant caused mortality at both early and late stages of embryo development; it caused coagulation, severe deformity, and hemolysis. Both the EC50 and the 50% lethal concentration (LC50) for sodium dodecyl sulfate were 9.37 mg/L. Salinity influenced the toxicity of Zn to killifish embryos: at 40 psu Zn was found not to be toxic, whereas at 20 psu toxicity had increased significantly (p < 0.05). Values of EC50 and LC50 were 2.5 mg/L and 4 mg/L, respectively. Concentrations above 15 mg/L in embryos were often accompanied by upper abdominal edema and inhibition of growth, especially evident in the tail. Chlorine caused mortality at a lower concentration; for example, at 0.05 mg/L 33% of embryos were found dead at the end of the experiment. The LC50 for chlorine was determined to be 0.08 mg/L. Examination of the existing literature showed similar results to the present study's findings. The results suggest a more comparable sensitivity of killifish embryos to that of other fish embryo test recommended species. The present study's findings support the ability of killifish to be an indicator organism for environmental risk assessments of Arabian Gulf waters. Benefits include sensitivity to a wide range of substances and conditions, animal alternative, ease of fish breeding, and clarity of the embryos.
Coral reefs are very important as they provide a foundation habitat for many aquatic species. Corals are marine invertebrates that exist as communities of polyps. Occasionally when corals experience physical stresses, the polyps expel their symbiotic zooxanthellae resulting in a white appearance. This is commonly described as “coral bleaching”. The Arabian Gulf is well known as one of the most extreme environments in which zooxanthellate coral reef communities occur. A combination of both extremely high and low temperatures as well as high salinities, combined with shallow profile of the coastal waters (high luminosity) imply high stress for coral physiology that may explain much of the coral bleaching and mortality events observed during the last decade. We initiated a series of laboratory experiments (microcosms: ecosystems under controlled conditions) to understand the impact of specific environmental parameters on Qatari coral health under controlled lab conditions. To draw a conclusion about optimum conditions and tolerance range for corals in Qatari waters, Porites sp. nubbins, collected from natural coral reefs North of Qatar, were cultured in pre-acclimatized laboratory aquaria. Orthogonal experiments were conducted to test the physiological response of corals under 3 stress stimuli: salinity, light intensity and temperature. Imaging-Pulse Amplitude Modulation Fluorometry (Imaging-PAM) and buoyant weight were utilized during experiment to measure photosynthetic performance and growth of the corals. Results revealed that elevated levels of temperature and salinity have a statistically significant effect on Symbiodinium photosynthetic activity; while light intensity did not. High level of salinity (50 psu) affected the corals’ photosynthetic efficiency. As a result, corals’ weight dropped down causing partial bleaching which was noticed at day 10 of the experiment with faded spots that covered the corals’ body and allowing other algae to overgrow. The decrease in photosynthetic activities of the in-hospite Symbiodinium under acute salinities and temperature levels were effectively observed through Imaging-PAM only after the 6th day of exposure. This suggests that in-hospite Symbiodinium of Porites sp. are affected only in relatively prolonged extreme conditions. A fast and comprehensive recovery of Porites sp. health could; therefore, be possible for short exposure to extreme temperature or salinity conditions. These results are very important to address the coral mortality and bleaching events occurring in Qatari coastal waters and may help establish guidelines for coral relocation efforts in Qatar marine environment or the identification of potential impacts of thermal pollution on coral reefs in Qatari waters due to industrial discharges from power or desalination plants.
Background: The use of fish embryos for toxicity testing (FET) is under consideration as an alternative to traditional acute fish toxicity tests. For the past two years, a marine fish embryo test (mFET) has been under development in our laboratory as a routine ecotoxicological test for risk assessment of potential contaminants around the Qatari coastal area. Objective: The objectives of this study were to: a) develop and use a flow-through system to optimize the mFET test conditions to maintain stable concentration of volatile compounds; b) correlate the flow-through mFET to the conventional acute fish test; c) investigate changes in sensitivity of Arabian Killifish embryos to toxicity of chlorine-produced oxidants under flow-through conditions compared to the previous static mFET. Methods: The flow-through system was carried out using custom designed glass chambers. Peristaltic pumps were used to ensure constant flow conditions. To investigate the effect of the flow-through mFET on toxicity of chlorine, fertilized eggs were exposed to aqueous concentrations of calcium hypochlorite for up to 240 hours. The investigated endpoints included; coagulated eggs, somite development, heartbeat, tail detachment, hatchability and post-hatch mortality. Results: The present investigation demonstrated that the custom designed flow-through system enhanced the FET conditions compared to the static FET. The flow-through system stabilized chlorine concentration and provided a larger volume which allowed an increase in the number of test embryos and sufficient test media for chemical analysis. Conclusions: Our data showed that the flow-through system improved the mFET assay for conditions like control survivability and for the main goal of bringing the sensitivity of the embryos into alignment with published data on the effects of chlorine-produced oxidants. This dataset, in conjunction with our previous work on static test conditions provides a wider range of applicability for the assay. In order to further support the mFET as an alternative to acute fish testing, the flow-through FET is currently being extended to other potential compounds of interest.
Background: The coral ecosystem in Qatar is very important as it provides a foundation habitat for many aquatic species. An extensive two-year field study was conducted to evaluate the effectiveness of pulse amplitude modulation (PAM) fluorometry in monitoring the health of sensitive ecosystems such as coral reefs along the coast of Qatar. The study demonstrated that PAM fluorometry can provide reliable and objective information on coral health in advance of visual signs of stress. The scope has now been expanded to include laboratory-based research. Objectives: The objectives of this research are: a) to establish a viable laboratory-based Qatari coral (Acropora sp.) culture system and b) to utilize laboratory-based imaging-PAM fluorometry to compile baseline data, and gain an understanding of environmental parameters that affect the health of the Qatari coral. Methods: Laboratory studies were initiated in December 2011; Acropora samples were collected from mother colonies in Umm Al-Arshan (north of Qatar); the 'nubbins' were cultured in pre-acclimatized laboratory aquaria. Imaging-PAM fluorometer was used to measure photosynthetic processes that were correlated to laboratory culture conditions. A wide range of water quality parameters have been measured, including: temperature, salinity, ammonia, nitrate, nitrite, phosphate, calcium and pH. Results: This research showed that it is possible to successfully culture Acropora coral; the initial colonies have grown to the point that several subsequent colonies have been produced to initiate laboratory assay development. The results of the imaging-PAM also show good correlation with the data obtained using the instrument used in the field. Conclusion: This study demonstrated for the first time the successful culture of Qatari Acropora in a laboratory setting in Qatar. The imaging-PAM fluorometer was also used to obtain detailed visual images of photosynthesis processes. Future studies include Acroproa eco-toxicological experiments to study contaminants that could affect the health of the corals around the Qatari coastal area.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.