Impact of polystyrene microplastics on major marine primary (phytoplankton) and secondary producers (copepod).

The effect of microplastic adsorption on marine microalgae Tetraselmis suecica, Amphora subtropica, and copepod Pseudodiaptomus annandalei was investigated in the present study. Fluorescence microscopic images were used to evaluate MP interactions with algae and copepods. T. suecica growth rate decreased with effects of 0.1 µm polystyrene exposure to 75 µl/100 ml (0.899 to 0.601 abs), 50 µl/100 ml (0.996 to 0.632 abs) and 25 µl/100 ml (0.996 to 0.632 abs), respectively. On the other hand, at 10th day of experiment, the control T. suecica showed the highest growth rate (0.965 abs), chlorophyll concentration (Chl-'a' = 21.36 µg/L; Chl-'b' = 13.65 µg/L), and cell density (3.3 × 106 cells/ml). A marine diatom A. subtropica absorbed 2.0 µm microplastics, and the maximal inhibition rate increased at higher MP concentration until 10th day. The highest MPs (75 µl/100 ml) treatment resulted in decreased growth rate of A. subtropica from 0.163 to 0.096 abs. A. subtropica (without MPs) had the highest lipid concentration of 27.15%, whereas T. suecica had the lowest lipid concentration of 11.2% (without MP). The maximum survival (80%) of P. annandalei was found in control on 15th day whereas on 12th day, the microplastics ingested copepod had the lowest survival rate (0%). On 15th day, the maximum Nauplii Production Rate (NPR) (19.33) female-1 was observed in control, whereas the minimum (17.33) female-1 NPR was observed in copepod ingested with MPs. The maximum lipid production (17.33% without MPs) was reported in control, whereas MPs fed copepods had the lowest lipid production (16%). Long-term exposure to polystyrene microplastics significantly reduced algae growth and chlorophyll concentration and also NPR and lipid concentration rate of copepod. We inferred that microplastic exposure of algae and copepods might results in persistent decreases in ingested carbon biomass over time.

Biodegradation of low-density polyethylene and polypropylene by microbes isolated from Vaigai River, Madurai, India.

The present study aimed to evaluate the microplastic degradation efficiency of bacterial isolates collected from Vaigai River, Madurai, India. The isolates were processed with proper methods and incorporated in to the UV-treated polyethylene (PE) and polypropylene (PP) degradation. Based on preliminary screening, four bacterial isolates such as Bacillus sp. (BS-1), Bacillus cereus (BC), Bacillus sp. (BS-2), and Bacillus paramycoides (BP) were proceed to further degradation experiment for 21 days. The microplastics were filled with bacterial isolates which is use microplastic (PE, PP) as carbon source for their growth and proceed for shake flask experiment were carried out by two approaches with control. The microplastic degradation was confirmed through their weight loss, increasing fragmentations and changes of surface area against control experiments (microplastic without isolates) also confirms degrading efficiency of isolated bacterial strains through non-changes in their weight and surface area. The highest degradation of PP and PE were observed in BP (78.99 ± 0.005%), and BC (63.08 ± 0.009%) in single approach, while in combined approach BC & BP recorded the highest degradation in both PP (78.62 ± 2.16%), and PE (72.50 ± 20.53%). The formation of new functional groups is confirming the biofilm formation in the surface area of microplastics by isolates and proving their efficiency in degrade the microplastics. The degradation of microplastic experiments should be cost effective and zero waste which is helpful to save the environment and the present findings could reveal the way to degrade the microplastics and prevent the microplastic pollution in aquatic environment.