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MICROBIAL GROWTH ON POLYETHYLENE PLASTIC FROM 2 DIFFERENT LOCATIONS IN A WETLAND ENVIRONMENT

Abstract

Plastic pollution is a growing concern worldwide because of its persistence in the environment. Plastics in the environment can become colonized by various microorganisms which could aid in their natural degradation. Few microorganisms have been identified that can break down certain types of plastics, however the extent of microbes growing on plastic waste is vastly unknown, which highlights a need for further research in this area. This research aimed to determine whether plastics deposited in stream or soil environments exhibited significantly different types and amounts of microbial growth. Two environments, soil and stream, were chosen to deposit low-density polyethylene plastic (LDPE) films. Five similar sized films were placed inside 6 mesh bags and secured with rope and stakes to prevent loss. Three replicate bags contianing 5 films each, were placed in each environment for approximately two months to allow microbial colonization on the LDPE plastic films. After collection of the samples, the films were sterilely swabbed, and microorganisms were plated on Tryptic-soy agar plates that were incubated for 24 hours. After incubation, microorganisms and their morphological differences were observed on each plate using a bifocal microscope. Additionally, a count of open space was performed for each plate. There were similar and recognizable morphological characteristics of microorganisms observed on both the soil and stream plates. Although the stream plates had a greater variety of morphological traits, containing several highly distinct microorganisms. From the counts of open space, an independent samples T-test was used to compare the relative amount of growth on each plate. It was concluded that there is a significant difference in the amount of microbial growth on plastics deposited in soil and stream environments, with the stream environment containing more growth. Streams provide continuous sources of nutrients, carrying rich organic matter downstream providing a stable environment for microbial growth. Nutrient acquisition in the soil environment is slower than in streams due to less nutrient mobility and a slower decomposition. The factors of nutrient availability, temperature, and moisture content in a stream help provide a more favorable environment for microbial growth and potentially more microbial degradation of plastics in that environment.

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