Mikroplastik konsantrasyonu siyonabakteri yoğunluğu üzerine etkisinin araştırılması
Investigation of the effect of microplastic concentration on cionababacteria density
Yazar: FATMA GÜZEL YILMAZ
Danışman: PROF. DR. NURTAÇ ÖZ
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2023
Konu: Çevre Mühendisliği = Environmental Engineering

Özet:
Son yıllarda plastik günlük hayatın ayrılmaz bir parçası haline gelmiştir. Her yıl dünya çapında milyonlarca ton plastik malzeme üretilmektedir. Plastiğin birçok farklı sektörde yaygın olarak uygulanması ve uzun ömürlü özellikleri nedeniyle, son zamanlarda plastik çöp miktarı önemli ölçüde artmış olup günümüzde  plastik kirliliği, çevre ile ilgili en sorunlu konular arasında kabul edilmektedir. Plastikler, ucuz, ulaşılabilir, hafif, esnek yapıda oldukları ve insanlara sağladığı faydadan dolayı diğer ürünler yerine tercih edilmektedir. Birçok avantajına rağmen plastikler atık haline geldiğinde uzun yıllar doğada varlığını sürdürerek çevre için ciddi bir tehdit haline gelmektedir. Boyut olarak 1μm ila 5mm arasında değişen plastik parçacıklar mikroplastik olarak tanımlanmaktadır. Çok çeşitli ürünlerden kaynaklanan mikroplastikler küresel ölçekte yayılım göstermiş olup ekosistemleri ciddi boyutta etkilemektedir. Mikroplastikler, endüstriyel üretim ve insanın günlük yaşamı süreçlerinde kozmetiklerin veya küçük boyutlu liflerin doğrudan suya bırakılması gibi çeşitli şekillerde su ortamına deşarj edilmektedir. Mikroplastiklerin son derece küçük boyutları ve geniş dağılımları nedeniyle memeliler, balıklar, kabuklular ve zooplankton gibi çeşitli trofik seviyelerdeki organizmalar tarafından doğrudan veya dolaylı olarak alınabilmekte ve su ekosistemi için büyük bir tehdit oluşturmaktadır. Aynı zamanda, büyümenin azalmasına, doğurganlığın engellenmesine, oksijen tüketiminin değişmesine, yaşam süresinin azalmasına, sınırlı beslenme kapasitesine neden olur. 
Mavi-yeşil algler, prokaryotik hücre yapılarından kaynaklı olarak 'siyanobakteriler' olarak da isimlendirilirler. Fotosentez özelliğine sahip olup, bulunan ve hala varlığını sürdüren en eski fosildir. Mikroplastikler sucul ortamda canlılar için etkili bir kirletici olup siyonabakteriler içinde tehlike oluşturmaktadır. Mikroplastiklerin sucul ekosistemdeki varlığı siyonabakterilerde klorofil içeriğinin, fotosentez aktivitesinin giderek azalmasına sebep olmaktadır.  
Bu çalışmada farklı tür ve boyutlardaki PS, PP, PVC mikroplastiklerin siyanobakteri kültürlerinin gelişimi üzerindeki etkisininin gözlemlenmesi amacıyla; Microcystis aeruginosa, Synechocystis sp ve Arthrospira platensis kültürlerinden çalışma süresinde, 2 günde bir örnek alınarak 15 gün boyunca siyanobakterilerin spektrofotometrik hücre yoğunlukları, biyokütle miktarları, klorofil-a miktarları, ve mikroskobik olarak hücre sayımları yapılıp ve Malondealdehit (MDA) ve Hidrojen peroksit (H2O2) enzimleri analiz edilmiştir. Her mikroplastik için >100 µm ve <100 µm olmak üzere iki farklı boyutta uygulama yapılmıştır. Sonuç olarak hücrenin maruz kaldığı mikroplastik boyutunun siyonabakterilere doğrudan etkisinin olduğu belirlenmiştir.

Abstract:
In recent years, plastic has become an integral part of daily life. Millions of tons of plastic materials are produced worldwide every year. Due to the widespread application of plastic in many different sectors and its long-lasting properties, the amount of plastic garbage has increased significantly in recent times, and today plastic pollution is considered one of the most problematic issues related to the environment. When plastics are broken down in various ways and come to smaller sizes, they are called microplastics. In recent years, it is known that microplastics are frequently seen in sea, fresh water resources, land and organisms.
Plastic pollution in a broad sense; It can be stated as the accumulation of plastic wastes left to nature by humans, on land and in the seas. Plastics have diversified so much with the advancement of science, pollutants that are difficult to filter as part of people's daily life. In our society, the land is polluted first, as people throw their garbage into the environment uncontrollably and use plastic excessively. The plastic wastes formed are naturally transported from the land to the aquatic environment over time. During this event, plastics break down into smaller pieces in size, forming plastics microplastics.
The term microplastic was first used in 2004 by Thompson et al. was used to describe the abundance of microscopic plastic debris observed in marine environments. These substances, defined as microplastics, are plastic particles ranging in size from 1μm to 5mm, and they are present in all ecosystems and have reached everywhere from urban areas to freshwater regions, from the open seas to the great oceans. Terrestrial ecosystems play an important role in the transport of microplastics to aquatic ecosystems. Microplastics can occur in the terrestrial environment with the effect of ultraviolet rays or natural effects such as water, air, wind and sun.
The first studies in this area were made in aquatic ecosystems, and microplastics are considered as serious aquatic environment pollutants. Microplastics with a density greater than water may show accumulation in the sediment. Surface microplastics in the waters may become biologically contaminated over time, absorb other pollutants, and increase in density and collapse. Microplastics that settle to the bottom can be repeatedly raised and transported to the aquatic environment by the movements of water and aquatic organisms.
Microplastics are an effective pollutant for living things in the aquatic environment and pose a danger to cyanobacteria. The presence of microplastics in the aquatic ecosystem causes cyanobacteria to gradually decrease in their chlorophyll content and photosynthesis activity.
The most important symptom of cyanobacteria and their toxins is organic contamination and eutrophication. Eutrophication prepares the environment for deterioration of water quality, formation and proliferation of cyanobacteria. Excessive algal growth and eutrophication cause pollution in the aquatic ecosystem, endanger usable water resources, and pose a great threat to aquatic organisms and humans. The first studies in this area were made in aquatic ecosystems, and microplastics are considered as serious pollutants of the aquatic environment.
Microplastics with a density higher than water may accumulate in the sediment. Surface microplastics in waters can become biocontaminated over time, absorb other pollutants, increase in density and precipitate. Microplastics that settle to the bottom can be transported to the aquatic environment by rising repeatedly with the movements of water and aquatic organisms.
In the study, polypropylene, polyvinyl chloride, polystyrene microplastics in different sizes; The effects of a single application on various cyanobacteria species such as Microcystis aeruginosa, Arthrospira platensis, and Synechocystis sp will be investigated. In this thesis, spectrophotometric cell densities, biomass amounts, chlorophyll-a amounts, and microscopic cell counts of cyanobacteria will be made and Malondealdehyde (MDA) and Hydrogen peroxide (H2O2) enzymes will be analyzed.
The mode of action of microplastics against microalgae is very complex. Considering that a typical algal cell wall pore size is < 20 nm (smaller than most single microplastics), two interaction effects can be pointed out between these organisms and microplastics. The first is that microplastics can affect microalgae through their cell walls or cause membrane damage after direct contact, which may eventually lead to cytotoxic effects (Zhang et al., 2017; Liu et al., 2019), and the other effect is the shading effect of microplastics in the water column (access to light). These are the effects of being able to affect microalgae through a reduction in photosynthesis (Bhattacharya et al., 2010; Liu et al., 2019; Wang et al., 2020). Microplastics can also physically damage algal cells by increasing osmotic pressure and altering biocomponent compositions (including carbohydrate, lipid, and protein levels) (Manzi et al.,2022).
Toxicity of microplastic to microalgae; It depends on many variables such as the type and size of microplastics, surface properties, concentrations and exposure time of microalgae to microplastics.
During the presented 15-day study, reduction in cell density of Microcystis aeruginosa, Synechocystis sp and Arthrospiraplatensis algae greater than 100 µm in polyvinylchloride and polypropylene microplastics, reduction in cell density of less than 100 µm in polyvinylchloride and polypropylene microplastics, and polypropylene microplastics in 1 µm. not observed. It was observed that the cell density and optical density progressed in direct proportion in each experimental group. While a certain increase in the amount of chlorophyll-a was observed for each cyanobacterial culture in PP and PVC types with microplastic size less than 100 µm, a higher increase was observed in polystyrene with 1 µm size compared to other small size microplastics. This result shows us that photosynthesis may be adversely affected as the microplastic size increases in cyanobacteria.
Toxicity of microplastic to microalgae; It depends on many variables such as the type and size of microplastics, surface properties, concentrations and exposure time of microalgae to microplastics. In our study, it was observed that chlorophyll-a values, cell density and cell numbers and AKM amounts were affected in different degrees in all three cyanobacteria species.