Microplastics distribution and possible ingestion by fish in lacustrine waters (Lake Bracciano, Italy)

Microbial colonization patterns and biodegradation of petrochemical and biodegradable plastics in lake waters: insights from a field experiment

Introduction

Once dispersed in water, plastic materials become promptly colonized by biofilm-forming microorganisms, commonly known as plastisphere.

Methods

By combining DNA sequencing and Confocal Laser Scanning Microscopy (CLSM), we investigated the plastisphere colonization patterns following exposure to natural lake waters (up to 77 days) of either petrochemical or biodegradable plastic materials (low density polyethylene - LDPE, polyethylene terephthalate - PET, polylactic acid - PLA, and the starch-based MaterBi® - Mb) in comparison to planktonic community composition. Chemical composition, water wettability, and morphology of plastic surfaces were evaluated, through Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and static contact angle analysis, to assess the possible effects of microbial colonization and biodegradation activity.

Results and Discussion

The phylogenetic composition of plastisphere and planktonic communities was notably different. Pioneering microbial colonisers, likely selected from lake waters, were found associated with all plastic materials, along with a core of more than 30 abundant bacterial families associated with all polymers. The different plastic materials, either derived from petrochemical hydrocarbons (i.e., LDPE and PET) or biodegradable (PLA and Mb), were used by opportunistic aquatic microorganisms as adhesion surfaces rather than carbon sources. The Mb-associated microorganisms (i.e. mostly members of the family Burkholderiaceae) were likely able to degrade the starch residues on the polymer surfaces, although the Mb matrix maintained its original chemical structure and morphology. Overall, our findings provide insights into the complex interactions between aquatic microorganisms and plastic materials found in lake waters, highlighting the importance of understanding the plastisphere dynamics to better manage the fate of plastic debris in the environment.

Distribution and abundance of microplastics in the water column of Vembanad Lake-A Ramsar site in Kerala, India

The study focuses on the occurrence, abundance and characteristics of microplastics (MPs) in the subsurface and bottom waters of Vembanad Lake, a Ramsar site in the state of Kerala. Even though several studies elucidate the prevalence of microplastic pollution in the surface waters of aquatic ecosystems, a little is known about the vertical distribution of MPs in the water column. Vembanad Lake water is greatly affected by microplastic pollution compared to other Indian lakes as it receive discharges from six rivers; a number of sewage canals and run-off. Ubiquitous distribution of MPs was found in the lake with a mean abundance of 26.79 ± 3.74 items L-1 and 52.70 ± 5.43 items L-1 in subsurface and bottom waters respectively. Fibers, constitute more than half of the total MPs in both subsurface and bottom waters. The dominance of polyamide and polypropylene with most of the MPs being fibers indicate that they originate probably from fishing activities and laundry wastewater. The particles with in the size range 100-500 μm were in excess in the water samples. Further fragmentation, increasing the number of MPs in the lake water was envisaged from the SEM images of MPs showing cracks and crevices. These MPs along with adsorbed contaminants upon ingestion by the aquatic organisms become a threat to the food web of the lake. The local population which depends mainly on the fishes and mussels of the lake for their dietary needs would be greatly affected by the contamination of the lake with MPs. Further research on MPs contamination in edible biota would give more insights on the extent and risks of MPs pollution in the lake.

Carassius auratus as a bioindicator of the health status of Lake Trasimeno and risk assessment for consumers

Fish are good bio-indicators of the health status of the aquatic environment and can be used as biomarkers to assess the aquatic behavior of environmental pollutants, the exposure of aquatic organisms, and the health risk for consumers. Goldfish are a significant bioindicator in the Lake Trasimeno aquatic system (Umbria, Italy). This study aimed to characterize the health status and the chemical and biotic contamination of Lake Trasimeno to define its anthropogenic and natural pressures and the risk associated with consuming its fishery products. 114 determinations were performed on Carassius auratus samples from 2018 to 2020, and the occurrence of brominated flame retardants, non-dioxin-like polychlorinated biphenyls, heavy metals, and microplastics was analytically investigated. Dietary exposure assessment, risk characterization, and benefit-risk evaluation were performed for schoolchildren from 3 to 10 years old. Flame-retardants registered high levels of non-detects (99% for polybrominated diphenyl ether and 76% for hexabromocyclododecanes), while polychlorinated biphenyls were found in all samples with a maximum level of 56.3 ng/g. Traces of at least one heavy metal were found in all samples, though always below the regulatory limit. Microplastics were found with a 75% frequency of fish ingesting at least one particle. Dietary exposure and risk characterization reveal negligible contributions to the reference values of all contaminants, except for mercury, which reached up to 25% of admissible daily intake. The benefit- risk assessment highlighted that the benefits of freshwater fish intake outweigh the associated risks. The examination of goldfish as indicator fish reveals the quality of Lake Trasimeno's aquatic environment and the safety of its products.