Summary: This review synthesizes the adverse effects of microplastics on marine copepods, which are crucial zooplankton and trophic links. It highlights that microplastic ingestion can impede feeding, block digestive tracts, and cause physiological stress, including immune responses, metabolism disorders, energy depletion, behavioral changes, growth retardation, and reproductive disturbances, with effects varying by species and life stage. The review also notes that microplastics can act as vectors for organic contaminants, exacerbating their toxicity. It calls for more multigenerational, mechanistic research using environmentally realistic conditions and integrated technologies to better understand the biological impacts and inform ecological assessments.

Summary: This review examines recent toxicological studies on microplastic (MP) pollution in marine environments, highlighting their widespread presence and impacts on various organisms including phytoplankton, zooplankton, bivalves, and fish. The studies primarily focus on MP bioaccumulation and their resulting biological effects at multiple levels, from molecular to organismic. The abstract emphasizes the diversity of impacts and the need to consider organism physiology and MP properties, calling for future research to focus on environmental relevance and quantitative modeling for risk assessments.

Summary: This study investigated microplastic ingestion by the copepod Acartia tonsa in Tampa Bay, Florida, between November 2017 and January 2020. Using laboratory and field methods, researchers collected copepods from seven stations, digested their gut contents, and visualized ingested microplastics using epifluorescent microscopy. They found that A. tonsa consumed microplastic fragments, ranging from 0.018 to 0.642 mm, with an average of 15.38 particles per 1,000 copepods. While ingestion rates and particle sizes varied between stations and months, no clear spatial or temporal trends were identified. The findings establish baseline data for microplastic-copepod interactions in this significant estuarine system.

Summary: This study exposed adult pearl oysters (*Pinctada margaritifera*) to polystyrene microbeads (6 and 10 μm) at concentrations of 0.25, 2.5, and 25 μg L–1 for two months to assess microplastic impacts. Results showed a significant decrease in assimilation efficiency and a dose-dependent reduction in Scope For Growth (SFG), with negative SFG observed at the highest concentration, indicating a negative impact on the oysters' energy balance. The study suggests that gonads may have been catabolized to maintain metabolism, leading to repercussions on reproduction.

Summary: This study compared microplastic (MP) concentrations in Manila clams and Pacific oysters, along with their surrounding sediment and water, between commercial shellfish aquaculture sites and nearby non-aquaculture beaches in coastal British Columbia, Canada. The findings indicated no significant difference in MP concentrations between the two site types for either bivalve species or environmental samples. While oysters at sites with synthetic nets showed marginally higher MP content, analysis of suspected MPs revealed a predominance of textile fibers, suggesting sources other than aquaculture degradation, potentially linked to larger average body weight at non-aquaculture sites.

Summary: This study exposed juvenile oysters (*Crassostrea gigas*) to three different concentrations of 6μm Polystyrene microbeads for 80 days to assess the impacts of microplastic (MP) exposure on growth, Condition Index, and Lysosomal Stability. Microbeads were detected in the oysters' intestines and digestive tubules without observed cellular inflammation. While weight and shell length were unaffected, the Condition Index initially increased but significantly decreased over time in the highest MP concentration group, which also exhibited the lowest Lysosomal Stability scores, indicating impaired cellular defense mechanisms. Most critically, oysters chronically exposed to the highest MP loads showed increased mortality.

Summary: This paper reviews the widespread ingestion of microplastics by commercially important marine species such as mollusks, crustaceans, and fish. It highlights growing evidence for direct impacts on organism physiology, reproductive success, and survival, as well as potential transfer through food webs, though ecological implications remain unclear. The abstract also notes concerns about microplastics acting as vectors for chemical pollutants and emphasizes the need for standardized methods, broader geographical studies, and urgent actions to control microplastic sources.

Summary: This study investigated the population-level effects of microplastics on the marine copepod Temora longicornis using laboratory experiments and a mechanistic model. Researchers found that microplastics reduced the copepod's filtration rate in a concentration-dependent manner, with a median effect concentration for filtration rate of 1956 particles L⁻¹. When these data were incorporated into an individual-based model, the theoretical concentration causing a 50% decrease in population equilibrium density was estimated to be 593 particles L⁻¹, which is four times lower than individual-level effect concentrations. However, the study notes that these theoretical effect concentrations remain significantly higher than ambient microplastic levels, and further in situ investigations are needed due to the short-term laboratory nature of the experiment.

Summary: This review synthesizes current knowledge on the ingestion of microplastics by marine organisms and their potential consequences, highlighting that while ingestion is common, experimental demonstration of effects is a growing research area. It discusses how heteroaggregate formation in prey guts may facilitate trophic transfer, and negative impacts on the survival and energetics of lower trophic level species raise concerns about energy transfer to higher levels. The paper also notes that microplastics can adsorb pollutants, potentially introducing and biomagnifying toxic chemicals in marine food webs, though the net effect on organism pollutant load compared to ambient water is unclear. Furthermore, it suggests microplastic ingestion may cause endocrine disorders and neoplasia in adult fish.

Summary: This study investigated macro- and microplastic intake across various marine seafood species, including fish, molluscs, and crustaceans, correlating ingestion levels with feeding behavior. Plastic fragments larger than 200 μm were detected in 71.5% of the 390 specimens analyzed from 26 species. Carnivorous species showed the highest prevalence of plastic ingestion, followed by planktivorous and detritivorous species, suggesting potential food chain transfer. However, the research found no evidence of microplastic translocation or bioaccumulation in the muscle tissue of these organisms, and it highlights the ubiquitous presence of microplastics as a threat to marine wildlife and human health.

Summary: This study examined the ecological impacts of microplastics on bivalve-dominated habitats using outdoor mesocosms with European flat oysters (Ostrea edulis) or blue mussels (Mytilus edulis). Researchers exposed sediment cores to two densities of biodegradable or conventional microplastics for 50 days, hypothesizing effects on bivalve filtration rates, nitrogen cycling, microphytobenthos productivity, and benthic invertebrate assemblages. Results showed that high microplastic concentrations (25 μg L-1) reduced filtration by M. edulis, while O. edulis filtration increased, accompanied by decreased porewater ammonium and benthic cyanobacteria biomass, and altered infaunal invertebrate assemblages (fewer polychaetes, more oligochaetes). The findings suggest microplastics can impact sedimentary habitat functioning and structure, with effects varying by dominant bivalve species.