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Because of the high production rates, low recycling rates, and poor waste management of plastics, an increasing amount of plastic is entering the aquatic environment, where it can provide new ecological niches for microbial communities and form a so-called plastisphere. Recent studies have focused on the one-way impact of plastic substrata or biofilm communities. However, our understanding of the two-way interactions between plastics and biofilms is still limited. This review first summarizes the formation process and the co-occurrence network analysis of the aquatic plastisphere to comprehensively illustrate the succession pattern of biofilm communities and the potential consistency between keystone taxa and specific environmental behavior of the plastisphere. Furthermore, this review sheds light on mutual interactions between plastics and biofilms. Plastic properties, environmental conditions, and colonization time affect biofilm development. Meanwhile, the biofilm communities, in turn, influence the environmental behaviors of plastics, including transport, contaminant accumulation, and especially the fragmentation and degradation of plastics. Based on a systematic literature review and cross-referencing from these disciplines, the current research focus, and future challenges in exploring aquatic plastisphere development and biofilm-plastic interactions are proposed. Refereed/Peer-reviewed

Plastic accumulates in the environment because of insufficient waste handling and the materials' high durability. Better understanding of plastic behaviour in the aquatic environment is needed to estimate transport and accumulation, which can be used for monitoring strategies, prevention measures, and plastic clean-up activities. Plastic transport models benefit from accurate description of particle characteristics, such as rising and settling velocities. For macroplastics, these are however still scarce. In this research, the rising and settling behaviour of three different polymer types (PET, PP, and PE) was investigated, which are the most common in the environment. All of the plastic particles were foils of different surface areas. A new method for releasing rising plastics without interfering the flow and disturbing the column was used. Four models that estimate the velocity based on the characteristics of the plastics are discussed, of which three are from literature, and one is newly derived. These models are validated using the data generated in this research, and data from another study on rising and settling velocities of plastic. From the models that were discussed, the best results are from the newly introduced velocity model for foils (R^2 = 0.96 and 0.58, for both datasets). This model shows potential to estimate the rising and settling velocity of plastics, and should be examined further by using additional data. The results of our paper can be used to further explore the vertical distribution of plastics in rivers, lakes and oceans, which is crucial to optimize future monitoring and cleanup efforts.

Land-based plastic waste, carried to the sea through rivers, is considered a main source of marine plastic pollution. However, most plastics that leak into the environment never make it into the ocean. Only a small fraction of plastics that are found in the terrestrial and aquatic compartments of river systems are emitted, and the vast majority can be retained for years, decades, and potentially centuries. In this presentation we introduce the concept of river systems as plastic reservoirs. Under normal conditions, hydrometeorological variables (such as wind, runoff and river discharge) mobilize, transport and deposit plastics within different river compartments (e.g. riverbanks, floodplains, lakes, estuaries). The emptying of these plastic reservoirs primarily occurs under extreme hydrological conditions (e.g. storms, floods). We specifically focus on the retention mechanisms within different river compartments, and their effect on the fate of the plastics that are accumulated over various timescales. With this presentation, we aim to introduce the concept of rivers as (long-term) sinks for plastic pollution, and provide suggestions for future research directions.

Study region: The Santa Ana River middle reach, a small coastal urban catchment in Southern California, USA experiences a Mediterranean climate and lowflows dominated by wastewater effluent. Study focus: River macroplastic flux can inform watershed management of plastic pollution. However, continuous macroplastic monitoring is not possible, so concentrations must be predicted during unobserved periods. We monitored macroplastic concentration and aimed to improve macroplastic flux estimation using strategies commonly employed in estimating mineral sediment flux. New hydrological insights for the region: Floating macroplastic size distributions were statistically equivalent between lowflow and stormflow samples – evidence that channel processes controlled macroplastic size distribution or macroplastic size distributions outside the channel were the same as inside. Concentrations fell during the falling limb of one hydrograph and rose during the rising limb of another hydrograph. A generalized additive model (GAM) revealed that macroplastic concentration increased in response to small discharge increases but decreased for the largest discharges. Macroplasitc depletion (relative to discharge) occurs at high flow magnitudes or during the falling limb. The annual mass flux of floating macroplastic was 27.4 (2.8–84.8) tonnes1yr−1 or 18.2 (2.9–222.2) tonnes1yr−1 as predicted using mean concentration or the GAM, respectively. With little data, the mean concentration approach may be appropriate but likely underestimates uncertainty – which will require extensive monitoring to reduce.

Earth science reviews 228, 104021 (2022). doi:10.1016/j.earscirev.2022.104021, Published by Elsevier, Amsterdam [u.a.]

Water 13(12), 1648 (2021). doi:10.3390/w13121648 special issue: "Special Issue "Microplastics in Water Bodies and in the Environment" / Special Issue Editors: Dr. Hrissi K. Karapanagioti, Guest Editor; Dr. Ioannis K. Kalavrouziotis, Guest Editor", Published by MDPI, Basel