World Aquaculture September 2018

56 SEP TEMBER 2018 • WORLD AQUACULTURE • WWW.WA S.ORG Heavy Metals in Fish and Plant Tissues Samples of fish and plant tissues were tested for heavy metal concentrations on the first and last days of the experiment. The standards for heavy metals in fish and plant tissues, based on Codex Alimentarius food standards, were available only for Cd and Pb in leafy vegetables and Hg in fish. The difference in heavy metal concentrations between the first and last day indicated that fish accumulated As in their tissues, but lettuce did not (Fig. 5). Cadmium did not accumulate in fish tissues in treated or control systems but accumulated in lettuce in both control and treatment systems, and lettuce in treatment systems was contaminated with Cd above the MCL (Fig. 6). Mercury accumulated only in fish tissues in the metal- treated system, but concentrations remained within the safe range (Fig. 7). Lead did not accumulate in fish in the control system but accumulated to greater levels in the treatment systems. However, Pb did not accumulate in plant tissues in treatment or control systems (Fig. 8). Antibiotic Resistance Bacteria counts were conducted from the water samples of the treated and control systems to identify any correlations between heavy metals and bacterial resistance to ampicillin and tetracycline. Samples were collected weekly over the last five weeks of the experiment. Bacterial resistance to both antibiotics showed a general increase over time in systems treated with heavy metals (Figs. 9 and 10), but these increases were not significant compared to control. In general, there was greater resistance to ampicillin than to tetracycline. Conclusions and Future Work The low levels of metals added to the treatment systems did not reduce the quality of the fish or plants. No exceedances of MCLs were revealed in the food products for the metals tested (As, Hg and Pb), except for Cd in lettuce. The microbial results indicated a slight trend of resistance development to ampicillin and tetracycline over time, but these results were not statistically signficant. These initial experiments will guide future work that may shed more light on heavy metal accumulations in aquaponics and the development of antibiotic resistance. Future work will include extending experiment time with several cycles of plant and fish growth, spiking with higher levels of heavy metals that are equal to concentrations found in water sources in developing countries, testing bacterial resistance to different antibiotics and preparing a mass balance model to identify the partitioning and exact accumulation of heavy metals within the aquaponics system. Acknowledgments I am grateful to my professors, Dr. Kevin Fitzsimmons and Dr. Jean McLain, who have provided support in my academic life. Many thanks to the University of Arizona for the financial support, Dr. McLain’s laboratory team for guiding the microbial analyses, and The Arizona Laboratory for Emerging Contaminants (ALEC) team for analysing the study samples. Very special gratitude goes out to King AbdulAziz City for Science and Technology for providing the funding for my study at the University of Arizona. Notes Hany M. Almotairy, Kevin Fitzsimmons, and Jean E. McLain Department of Soil, Water, and Environmental Science, University of Arizona. P.O. Box 210038. Tucson, Arizona 85721-0038. Corresponding author e-mail: halmotairy@email.arizona.edu . References Ali, H., K. Ezzat and A.S. Muhammad. 2013. Phytoremediation of heavy metals concepts and applications. Chemosphere 91:869-881. Armitage, P.D., M.J. Bowes and H.M. Vincent. 2007. Long-term changes in macroinvertebrate communities of a heavy metal polluted stream: The River Nent (Cumbria. UK) after 28 years. River Research 23:997-1015. Baker-Austin, C., M.S. Wright, R. Stepanauskas and J.V. McArthur. 2006. Co-selection of antibiotic and metal resistance. Trends Microbiology 14:176-182. Bax, R. and D. Grif n. 2012. Introduction to antibiotic resistance. Pages 1-12 In : A.R.M. Coates. Antibiotic Resistance. Springer Heidelberg, NewYork, NYUSA. Burridge, L., J.S. Weis, F. Cabello, J. Pizarro and K. Bostick. 2010. Chemical use in salmon aquaculture: a review of current practices and possible environmental effects. Aquaculture 306:7-23. Burzynski, M. and G. Klobus. 2004. Changes of photosynthetic FIGURE 9. Bacterial-resistance to ampicillin (Amp.). X axis represents the last five weeks of the experiment, after heavy metals were added to systems. Y axis represents the ratio of bacterial counts of the average of Control system replicates (blue) and the average of the Treatment system replicates (orange) to a control with no antibiotic. FIGURE 10. Bacterial-resistance to tetracycline (Tetr.). X axis represents the last five weeks of the experiment, after heavy metals were added to systems. Y axis represents the ratio of bacterial counts of the average of Control system replicates (blue) and the average of the Treatment system replicates (orange) to a control with no antibiotic.