www.trjfas.org ISSN 1303-2712 Turkish Journal of Fisheries and Aquatic Sciences 12: 309-314 (2012) DOI: 10.4194/1303-2712-v12_2_16 Toxicity and Removal of Zinc in the Three Species (Acutodesmus obliquus, Desmodesmus subspicatus and Desmodesmus armatus) Belonging to the Family, Scenedesmaceae (Chlorophyta) Zekiye GÜÇLÜ1,*, Ömer Osman ERTAN1 1 Süleyman Demirel University, Fisheries Faculty, 32500 Eğirdir, Isparta, Türkiye. * Corresponding Author: Tel.: +90.246 3133447 ; Fax: +90.246 3133452; Received 04 November 2011 E-mail: [email protected] Accepted 28 March 2011 Abstract In this study, the effects of zinc upon growth of three green microalgal species, Acutodesmus obliquus (Turpin) Hegewald and Hanagata, Desmodesmus subspicatus (Chodat) Hegewald and Schmidt and Desmodesmus armatus (Chodat) Hegewald, and the capability of these green algae for removal of zinc were investigated. Growth inhibition of the microalgal cells was determined following exposure for 96 h to five initial concentrations of zinc. The growth of the alga decreased with -1 increasing zinc concentrations. EC50 values were determined as 2257.824, 1922.049 and 1634.275 µg L for Zn in the case of D. subspicatus, A. obliquus and D. armatus, respectively. The highest zinc removal percentage from media was determined in D. subspicatus (40%), and followed by A. obliquus (30%) and D. armatus (18%). Phenotypic plasticity in Scenedesmus has been documented in response to a wide variety of conditions. The phenotypic plasticity was observed in A. obliquus and D. armatus in all tested zinc treatments. Keywords: Zinc, algae, Acutodesmus, Desmodesmus, Scenedesmus, removal. Scenedesmaceae (Chlorophyta) Familyasına Ait Üç Türde (Acutodesmus obliquus, Desmodesmus subspicatus ve Desmodesmus armatus) Çinkonun Toksisitesi ve Uzaklaştırılması Özet Bu çalışmada; üç yeşil mikroalg türü, Acutodesmus obliquus (Turpin) Hegewald ve Hanagata, Desmodesmus subspicatus (Chodat) Hegewald ve Schmidt and Desmodesmus armatus (Chodat) Hegewald,’nün gelişimi üzerine çinkonun etkisi ve bu yeşil alglerin çinkoyu uzaklaştırması araştırıldı. Mikroalg hücrelerinin gelişiminin engellenmesi, 5 başlangıç çinko derişimine maruz bırakılarak belirlendi. Alglerin gelişimi, artan çinko derişimi ile azaldı. EC50 değerleri, D. subspicatus, A. obliquus ve D. armatus’da sırasıyla 2257,824, 1922,049 ve 1634,275 Zn µg L-1 olarak belirlendi. Ortamdan en yüksek çinko uzaklaştırma yüzdesi, D. subspicatus (%40)’ta belirlendi ve bunu sırasıyla A. obliquus (%30) ve D. armatus (%18)’un izlediği saptandı. Scenedesmus’ta fenotipik plastisiti, değişen çevre koşullarına tepki olarak bildirilmektedir. Fenotipik plastisiti, A. obliquus ve D. armatus’da test edilen tüm çinko derişimlerinde belirlendi. Anahtar Kelimeler: Çinko, alg, Acutodesmus, Desmodesmus, Scenedesmus, uzaklaştırma. synthesis and cell proliferation (U.S. EPA, 2005); Introduction however, it becomes toxic when available in higher Zinc is one of the most common elements in the concentrations (Nalimova et al., 2005) since it Earth’s crust. Most zinc enters the environment as the decreases cell division, mobility, total chlorophyll results of mining, purifying of zinc, lead, and content, ATPase activity and carotenoid/chlorophyll cadmium ores, steel production, coal burning, and ratio in microalgae (Omar, 2002). The toxicity of zinc burning of wastes. These activities can increase zinc depends on the external concentration, the zinc levels in the atmosphere (ATSDR, 2005). Zinc is an speciation, and the pH and hardness of the water essential micronutrient in all biota owing to its (WHO, 2001). In defense against the toxic effects of involvement in many physiological processes. It is heavy metals, the algal cells are equipped with a essential in the maintenance of plasma membrane variety of resistance mechanisms. At this respect, stability, in the activation of more than 300 enzymes phenotypic plasticity is a mechanism commonly (WHO, 2001), DNA and ribonucleic acid (RNA) documented for Scenedesmus in a variety of © Published by Central Fisheries Research Institute (CFRI) Trabzon, Turkey in cooperation with Japan International Cooperation Agency (JICA), Japan 310 Z. Güçlü and Ö.O. Ertan / Turk. J. Fish. Aquat. Sci. 12: 309-314 (2012) ecological conditions (Trainor, 1998; Peña-Castro et according to OECD-guideline 201 (OECD, 1984) al., 2004; Lürling, 2006; Lombardi et al., 2007). For (Table 1). To minimize the metal contamination, all example, in a study of the ecological impact of mine laboratoryware in contact with the culture or test effluents on freshwater microalgal populations, medium were soaked for 24 h in 1% HNO3 and rinsed Monteiro et al. (1995) found that Desmodesmus with deionised water. armatus (R. Chodat) E. Hegewald was the dominant Zinc stock solution was prepared from analytical species when heavy metal concentrations were high grade zinc chlorid (ZnCl2.2H2O). The effective enough to inhibit the growth of other microalgae. concentration range was determined from a range- Lombardi et al. (2007) also found that Acutodesmus finding test. Based on the results of the range-finding acuminatus (Lagerheim) Tsarenko caused phenotypic test, culture media of zinc concentrations 250, 500, -1 alterations by the presence of copper. On the other 1000, 2000, 4000 µg L were prepared by diluting a hand, the absorption of heavy metals by green algae stock of 1000 mg L-1. Control cultures were incubated affects trophic chains since these producers can in the same medium without toxicant. There were contaminate the organisms that depend directly or three replicates for the control and each of the indirectly on them (Magdaleno et al., 1997). Many treatment concentrations. chemical methods are currently known for removing The algal suspension of known cell density was heavy metals from aqueous solutions: precipitation, taken from the stock culture during the exponential electrolysis, ionic exchange, filtration, evaporation, growth phase. After mixing with synthetic OECD and others. Disadvantages of these methods are their culture medium, the initial cell density was high cost prize, low economic efficiency, especially approximately 8x104 cells ml-1. Different parameters, during removing small amounts of heavy metals, and including growth and removal of zinc were monitored a necessity of slag burial. Biological methods of metal repeatedly, at 24, 48, 72 and 96 hours after the start of detoxication and removal from aqueous solutions lack the test. The cell number was determined using a these disadvantages (Nalimova et al., 2005). neubauer improved counter (Marienfeld, Germany). Microalgae have been found to be very effective in Algal cell densities for each flask were measured removing heavy metals from wastewater because of daily and calculated as cell numbers (algal cell ml-1). their large surface area and high binding affinity The average specific growth rate µ (per day) for (Chong et al., 2000). In this research, the inhibition exponentially growing cultures was calculated using µ effects of zinc on the growth of three species = ln Nn – ln N1 / tn – t1 [where Nn the measured final belonging to the family, Scenedesmaceae cell density, N1 the nominal initial cell density and tn (Chlorophyta) to were evaluated, and the 96 h the time (day) after the initiation of the test] (OECD, removal processes of zinc in microalgae were 1984). The percentage inhibition of the cell growth at investigated. Additionally, we recorded the each test substance concentration (IA) was calculated morphological development observed during 96 h as the difference between the area under the control static cultures of A. obliquus, D. subspicatus and D. growth curve (AC) and the area under the growth armatus. Materials and Methods Table 1. Summary of standart bioassay protocol for Acutodesmus and Desmodesmus species growth inhibition Algal Stock Cultures bioassay Experiments were performed with the green algae A. (formerly Scenedesmus) obliquus (276-3a 1. Test type Static SAG), D. (formerly Scenedesmus) subspicatus (86.81 2. Temperature 25±2 °C 3. Light quality Cool white fluorescent SAG) and D. armatus (formerly S. quadricauda) lighting (276-4d SAG) obtained from Sammlung von 4. Light intensity 120 µE m-2 s-1 Algenkulturen der Universitat Göttingen (SAG, 5. Illumination Permanent Göttingen, Germany). These green algae were grown 6. Test chamber size 250 ml in a medium recommended by OECD (1984). The pH 7. Test solution volume 100 ml of culture medium was adjusted to 8 using NaHCO3- 8. Renewal of test solutions None HCl (0.1 N). Stock cultures were incubated in 250 ml 9. Age of test organisms 3-4 days 4 -1 erlenmeyer flasks containing 100 ml of sterilised 10. Initial cell density in test 8x10 cells ml chambers OECD medium under a photon irradiance of -2 -1 11. No. Of replicate 3 approximately 120 µE m s (cool white fluorescent chambers/concentration tubes) in constant illumination by constant shaking at 12. Shaking rate 100 rpm 100 rpm and temperature 25±2°C. 13. Test medium OECD culture medium 14. Metal concentrations Minimum of five and a Growth Inhibition Bioassays control 15. Test duration 96 h 96 h growth inhibition bioassays were conducted 16. Test endpoint Growth rate Z. Güçlü and Ö.O. Ertan / Turk. J. Fish. Aquat. Sci. 12: 309-314 (2012) 311 curve at each test substance concentration (At) as IA= EPA) Probit Analysis Program Version 1.5. The dose 2 AC – At / AC x 100 (OECD, 1984). response equation was X tested with 95% confidence. The data relative to growth and growth rate were Phenotypic