Siyanobakteri yoğunluğuna çevresel faktörlerin etkisinin araştırılması = Investigation of the effect of environmental factors on cyanobacterial density

Abstract

Sucul ekosistemin ilk basamağı olan alglerin, ağır metal ve mikroplastik stresinden etkilenmesiyle ekosistemin tür kompozisyonu değişmektedir. Bu durum sonucunda besin zincirinin üst basamağındaki canlılar da etkilenmektedir. Bu çalışmada Polipropilen (PP) ve bakır metalinin farklı konsantrasyonlardaki (0.5, 1, 2.5, 5, 10 ppm) maruziyetin kültürlerin gelişimi üzerindeki etkilerini gözlemlemek amacıyla Microcystis aeruginosa, Synechocystis sp. ve Arthospira platensis kültürlerinden çalışma süresinde 15 gün boyunca 2 günde bir örnek alınarak hücre sayıları, hücre yoğunlukları, askıda katı madde miktarları, klorofil-a miktarları, malondialdehit ve hidrojen peroksit miktarları ölçülmüş; mikroskobik olarak hücre sayımları yapılmıştır. Çalışma sonucunda, ağır metallerin incelenen alglere toksik etki ettiği ve alglerin büyüme ve gelişimini yavaşlattığı, hücre ölümlerine sebebiyet verdiği; düşük konsantrasyondaki (0.5 ppm) bakırın sonuçlar üzerinde fazla düşüş göstermediği fakat metal konsantrasyonu artışı ile tüm alg hücre sayılarında kontrole göre düşüş gözlemlendiği, özellikle Synechocystis sp. hücreleri boyutlarını sınırlandırdığı, Microcystis aeruginosa ve Arthospira platensis'te artan konsantrasyonla birlikte hücre çapının önemli ölçüde küçüldüğü tespit edilmiştir. Sonuç olarak ağır metal ve mikroplastik maruziyetinde alglere uygulanan konsantrasyon miktarındaki artışa bağlı olarak klorofil-a, optik yoğunluk ve AKM miktarında kontrole göre azalmalar görülmüş; MDA ve H2O2 miktarında bakır ve polipropilen stresine bağlı artış gözlemlenmiştir.

With the rapid population growth, technology, development of agricultural and industrial activities, water quality deteriorates with the direct and indirect wastes of human origin reaching the aquatic ecosystem and as a result, it causes biological accumulation and eutrophication. Heavy metals and microplastics taken into the body with food and water accumulate in the tissues and affect the food chain by causing damage to vital activities. The first of the activities that increase environmental pollution and cause deterioration of the ecological balance is the establishments containing heavy metals in their wastewater. Organizations that use various heavy metals such as lead, copper, cadmium, chromium, nickel, mercury, silver and arsenic in their processes are important for environmental health due to the permanent effects of these metals and are extremely toxic when exceeding a certain limit. Even low concentrations of copper, a metal used in various fields, have a toxic effect on the soil and aquatic ecosystem. Metal pollution in aquatic environments is a major global environmental problem facing humanity today that is attracting a lot of attention. Copper (Cu) and zinc (Zn) are among the most important elements in the metabolic processes of living organisms. Copper is a cofactor in various redox reactions for many metalloenzymes in biological metabolic activities, but excess copper adversely affects the growth of microalgae, can lead to cell death while causing photosynthetic system damage, inhibition of cell growth, and tissue damage in organisms. Plastics consist of a wide variety of long-chain polymeric materials obtained from different sources such as coal, oil and natural gas, which have various applications in everyday life and industry. Plastic waste adversely affects life on Earth through their unwanted accumulation in landfills, leaching into the soil, increasing greenhouse gas emissions, etc. Its ubiquitous presence and persistence in the aquatic environment is of concern as they pose a growing threat to marine organisms and ecosystems. Microplastics also cause decreased growth, inhibition of fertility, altered oxygen consumption, decreased life expectancy, limited nutritional capacity and increased activity of antioxidant-related enzymes.It is known that plastics, especially in the form of microplastics, interfere with the chemical interaction between marine organisms and cause intrinsic toxicity by absorbing persistent organic pollutants as well as pathogens. Since the complexity of the environmental environment plays an important role in the kinetics of biodegradation, biodegradation by microorganisms largely depends on the individual or synergistic energy of different environmental elements on the polymer. Even if microalgae do not have a direct effect on the degradation of plastic, their presence may be important in determining the presence of bacteria that break down other hydrocarbons, and that diatoms can serve as an important habitat for such microorganisms, while at the same time biocontamination of large surfaces protects the plastic from UV radiation and processes photodegradation. It has been suggested that it may have the opposite effect by delaying The aim of this study is; to contribute to the studies carried out to determine the effects of microplastic and heavy metal stress on the aquatic ecosystem. Therefore in order to observe the effects of exposure of polypropylene (PP) and copper metal at different concentrations (0.5, 1, 2.5, 5, 10 ppm) on the development of cultures, Microcystis aeruginosa, Synechocystis sp. and Arthospira platensis cultures were sampled every 2 days during the study period and spectrophotometric cell densities, chlorophyll-a amounts, suspended solids, malondialdehyde and hydrogen peroxide amounts and microscopic cell counts were performed for 15 days. At the beginning of the negative effects caused by heavy metals in algae, the vitality activities of the organism and the metal toxicity applied in the studies with algae; it has been reported to depend on the type of metal, the concentration of the metal in the environment, the chemical structure of the metal, the tolerance of the organism, its response to metal interaction, and the type of algae. In our study, it was observed that the amount of chlorophyll-a, cell density, optical density, MDA and H2O2 of all three algae species were affected to different degrees due to copper heavy metal. In the literature, heavy metals inhibit the growth of algae, causing disruption of the lag phase of growth. That the growth in increased concentrations of heavy metals caused a decrease in the rate of photosynthesis and the amount of chlorophyll-a, and that this may be because the toxic effect of heavy metals had inhibited chlorophyll-a; For this reason, it is stated that growth stops by inhibiting cell division in the algae. The decrease in chlorophyll-a content can have two reasons: first, the accumulation of intracellular reactive oxygen species disrupts the cell structure and blocks the synthesis of chlorophyll; Secondly, microplastics have a large surface area and strong adsorption ability, and microalgae and microplastics are suitable for hetero-aggregates of different sizes, neutralizing algae. During the presented 15-day study, cell densities decreased with increased copper concentration in Microcystis aeruginosa and Arthrospira platensis algae, while no significant decrease in cell density of Synechocystis sp. was observed. In polypropylene copper application, a further decrease in the number of cells was observed at the PP + 0.5 ppm Cu concentration, which is the lowest in Microcystis aeruginosa and Arthrospira platensis algae, and the cell numbers in Synechocystis sp. increased compared to the control. Microplastics in culture can have shading effects that reduce light intensity and algal photosynthesis. Microplastics can also physically damage algae cells by increasing osmotic pressure and altering their biocomponent composition (including carbohydrate, lipid and protein levels). Polymer type and size also contribute to algae toxicity and can have a direct effect on its distribution across the water column, leading to sedimentation or buoyancy. A significant decrease was observed in OD560 and chlorophyll-a measurements in three algae species exposed to copper and polypropylene copper dual applications with increasing concentration compared to the control group. Microcystis aeruginosa, Synechocystis sp. and Arthrospira platensis algae, the decrease in chlorophyll-a due to copper and microplastic effects may be due to the failure of enzymes responsible for chlorophyll-a biosynthesis, disruption of the biosynthesis process or breakdown of chlorophyll. In all cultures where copper was applied, the rapid decrease was at a concentration of 0.5 ppm, but the lowest value was measured at a concentration of 10 ppm. While there was a decrease in the amount of AKM of Microcystis aeruginosa treated with copper compared to the control, there was no significant decrease in Synechocystis sp. and Arthrospira platensis samples and the lowest amount of biomass was seen at a concentration of 5 ppm. In dual practice, a decrease in the amount of AKM was observed with increasing concentration in all algae cultures. Malondialdehyde (MDA) is the effective end product of oxidative lipid peroxidation. It is used to understand the level of oxidative damage. An increase in the amount of MDA in the microorganism means an increase in the amount of free radicals.In our study, the amount of MDA of Microcystis aeruginosa and Arthrospira platensis cultures applied to copper metal was determined at concentrations of 1, 2.5, 5 and 10 ppm; A statistically significant increase in concentrations of 0.5, 1, 5 ppm was observed in Synechocytis sp. cultures. A positive relationship was observed between changes in the amount of MDA and the amount of hydrogen peroxide in all algae cultures and stress factors. In the dual application of polypropylene and copper, the amount of MDA of Microcystis aeruginosa algae cultures increased with increasing concentration; In Synechocystis sp. and Arhrospira platensis algae, the highest amount of MDA was measured in application with polypropylene and 2.5 ppm copper, while the lowest amount was observed in polypropylene and 1 ppm concentration. As a result of the study, it was determined that heavy metals had a toxic effect on the algae examined and slowed the growth and development of the algae and caused cell death. The presence of hydrogen peroxide and malondialdehyde products resulting from enzyme activities and their increase due to heavy metal concentration is also an indication that copper metal affects the metabolic balance within the cell.