Dynamic signatures of microplastic distribution across the water column of Yangtze River Estuary: Complicated implication of tidal effects

Abundant small microplastics hidden in water columns of the Yellow Sea and East China Sea: Distribution, transportation and potential risk

Microplastics (MPs) pose significant concerns for marine ecological security due to their minuteness and ubiquity. However, comprehensive knowledge on their distribution and fate in seawater columns remains limited. This study investigated the abundances and characteristics of MPs across 3-6 water layers in the South Yellow Sea and East China Sea. Results indicate that high-abundance small MPs (< 100 µm) (average 6567 items/m3) were hidden beneath the sea-surface, predominantly fine-grained particles (< 20 µm) and high-density polymers (> 1.03 g/cm3). The total suspended MPs (5.0-834.2 µm) are estimated at 2.9-3.1 × 1017 particles, with most of them occurring in upper layers. In profiles, their distribution varied by physical properties with depth; fragment-shaped and high-density MPs increased in proportion at greater depths, contrasting with fibrous MPs. These MPs originated primarily from the Yangtze River and their winter transport was driven by the Yangtze River Dilution Water, East China Sea Coastal Current, and Yellow Sea Warm Current, resulting in their accumulation in coastal and estuarine regions. Consequently, the Yangtze River Estuary ecosystem faces substantial risks from MP pollution throughout the water column. This work unveils the prevalence of small MPs in coastal water columns and intricate interaction between their fate and hydrodynamic conditions.

Insights into the seasonal distribution of microplastics and their associated biofilms in the water column of two tropical estuaries

The present study describes the seasonal distribution of microplastics (MPs) and their associated biofilms in the water column of the Netravathi-Gurupura estuary, southwest India. An average abundance of 8.15 (±3.81) particles/l and 1.14 (±0.78) particles/l was observed during the wet and dry seasons, respectively. Fibres, films, and fragments accounted for majority of the microplastics. Polyethylene terephthalate, polyethylene, polyurethane, polyester, polystyrene, and high-density polyethylene were the major polymers. The risk assessment revealed a low Pollution Load Index, but the Polymer Hazard Index showed higher toxicity. Diatoms from nine genera were observed attached to the microplastic samples with Amphora and Navicula spp. reported in both estuaries during both seasons. The considerable diversity of diatoms, along with other microbial groups, in microplastic-associated biofilms in this study, highlights the urgent need to understand the structure and development of microplastic-associated biofilms and their role in the vertical and horizontal transport of microplastics in tropical estuaries.

Dynamics of microplastic abundance under tidal fluctuation in Musi estuary, Indonesia

Tidal dynamics contribute to fluctuations in microplastic abundance (MPs). This is the first study to characterize MPs under the influence of tidal fluctuations in the Musi River Estuary. MPs samples were collected during flood and ebb tides at 10 research stations representing the inner, middle and outer parts of the Musi River Estuary. MPs were extracted to identify the shape, color and size. MP abundances were 467.67 ± 127.84 particles/m3 during flood tide and 723.67 ± 112.05 particles/m3 during ebb tide. The concentration of MPs in the outer zone of the estuary (ocean) was detected to be higher than in the inner zone of the estuary (river). The MPs found were dominated by black color, film shape and size 101-250 μm. A greater abundance of MPs at ebb tide than at flood tide implies that the Musi Estuary's largest source of emissions is discharge from the river.

Do tidal fluctuations affect microplastics distribution and composition in coastal waters?

The hydro-meteorological conditions in marine environments are recognized to have a major impact on the transport and dispersion of microplastics (MP), although their precise effects remain poorly understood. This study investigates the effects of tidal fluctuations on MP abundance and composition in a megatidal coastal water. Waters samples were collected every ninety minutes over the course of two complete tidal cycles - one during spring tide and another during neap tide. There were no significant disparities in term of abondance, size, and composition of MPs between the samples collected during the two tidal cycles. Nevertheless, MP abundance and characteristics (morphology, size and polymer types) can be influenced over the course of a complete tidal cycle due to the impact of tidal currents and water height. This study highlights the need to consider the fluctuations of the tidal cycle when planning in-situ surveys to better assess MP pollution in coastal environments.

Distribution and characteristics of microplastics in 16 benthic organisms in Haizhou Bay, China: Influence of habitat, feeding habits and trophic level

Microplastics (MPs) are widely found in the ocean and cause a serious risk to marine organisms. However, fewer studies have been conducted on benthic organisms. This study conducted a case study on the pollution characteristics of MPs on 16 marine benthic organisms in Haizhou Bay, and analyzed the effects of habitat, trophic level, and feeding mode on the MPs pollution characters. The results showed that MPs were detected in all 16 organisms with an average abundance of 8.84 ± 9.14 items/individual, which is in the middle-high level in the international scale. Among the detected MPs, the main material was cellophane. This study showed that benthic organisms can be used as indicator organisms for MPs pollution. MPs in organisms can be affected by their habitat, trophic level, and feeding mode. Comprehensive analysis of MPs in benthic organisms will contribute to fully understand the characterization and source resolution of MPs pollution.