Effects of microplastics on reproductive characteristics and mechanisms of the marine rotifer Brachionus plicatilis.

Microplastic pollution, especially secondary microplastics (MPs), poses a significant threat to marine ecosystems. Despite its prevalence, the impact of natural-aged MPs on marine organisms, hindered by collection challenges, remains poorly understood. This study focused on 1-3 µm natural-aged MPs collected from Japan's coastal sea, investigating their effects on the rotifer Brachionus plicatilis sensu stricto and its reproductive mechanisms. Rotifers exposed to varying MP concentrations (0, 20, and 200 particles/mL) over 14-day batch cultures exhibited reduced population growth and fertilization rates. Down-regulation of reproductive genes and up-regulation of oxidative stress-related genes were observed, indicating MP-induced disruptions. Enhanced activities of superoxide dismutase and acetylcholinesterase and elevated malondialdehyde levels further emphasized oxidative stress. These findings underscore the detrimental impact of MPs on rotifer reproductivity, shedding light on the underlying mechanisms.

Impact of nano- and micro-sized polystyrene beads on larval survival and growth of the Pacific oyster Crassostrea gigas.

This study successionally monitored how nano- and micro-sized polystyrene beads (MNPs) influence larval mortality, growth, and attachment behavior of the Pacific oyster Crassostrea gigas related to MNP diameter and concentration. D-shaped larvae were sequentially exposed to three-diameter MNPs (0.55, 3.00, 6.00 µm) at five concentrations (0, 0.1, 1.0, 10, 20 µg/mL), and their mortality, growth stages and attachment were observed daily until they die. In addition, MNP intake and accumulation in larvae at each growth stage were determined using fluorescent beads. Deterioration in larval growth and survival was observed under all the exposure conditions, while significant negative effects on the growth parameters were defined with smaller MNPs at lower concentrations. Fluorescent signals were detected in larval digestive tracts at all except D-shaped larval stage, and on the mantle and foot in pediveligers. Therefore, MNP intake adversely affects larval physiological conditions by the synchronal effects of MNP size and concentration. Our findings highlight the implications of MNP characteristics on Pacific oyster larvae, emphasizing the interplay between size, concentration, and physiological responses, crucial for mitigating nanoparticle pollution in marine ecosystems.