## 4 A Case Study of Glyphosate Transport via Polyethylene Microplastic Fomites
Following the inadequate application of GBHs on plants, glyphosate residues and their adjuvants in feed ingredients can end up in commercial or self-prepared shrimp feed. During feeding, those pesticide residues can interact with ubiquitous microplastics or fragmented pond liners in the water and at the bottom of a pond. Furthermore, runoff from a field can contain both microplastic polyethylene and GBH residues either separately or already adsorbed. Their passage through the water column already infiltrated with microplastics from other sources, including pond liners, further allows for interactionsand the adsorption of GBHs on PE microplastics. This situation results in the increased availability of GBHs-PE for shrimp to ingest during their normal feeding behavior [203]. Besides the direct consequences and toxic effects of GBHs-PE microplastics in shrimp, possible indirect effects along the gastrointestinal tract can also be of significance, such as interference with the natural shrimp intestinal microbiome and the disturbance of the microbiome roles in disease protection, improved feed energy utilization via microbial digestion, and the production of vitamins. The other possible exposure route is through the water, i.e., the waterborne route. The waterborne GBHs-PE microplastics in a shrimp farm could originate from different sources, including the fragmentation and weathering of the deteriorating pond liner, wind, runoff, and flooding, in combination with glyphosate residues, its metabolites, adjuvants released from the contaminated feed in water, and GBHs polluted from soil surface runoff or by leaching. Such GBHs-PE particles may enter shrimp via their gill filaments as well as their susceptible epidermis during the molting process and spread via the hemolymph and other tissues, causing alterations in different body systems. Despite the poorly understood adverse effects of GBHs-PE microplastics on shrimp, many studies illustrating their adverse effects on other organisms have been reported. Polyethylene microbeads combined with glyphosate showed a modified toxicological effect on the mortality rate of _Daphnia magna_. The different sorption capacities of PE to various glyphosate formulations significantly increased or reduced the mortality rate of _Daphnia magna_[204]. The interaction between polyethylene microplastics and GBH decreased lethal concentration 50 (LC50) and increased glutathione S-transferases (GST) activity compared with the direct negative effects of individual polyethylene microplastics and GBH additions in _Scinax squalirovstris_[205]. The chronic co-exposure of polyethylene microplastics and glyphosate to _Cyprinus carpio_ L. caused a decrease in swimming activity, changed the morphological integrity and dysfunction of the intestinal barriers, altered gut microbiota abundance and diversity, and modified the metabolic profiles associated with an altered amino acid and lipid metabolism [206]. Due to our limited knowledge about GBHs-polyethylene microplastics' fate and transport in a real environmental matrix and the gaps in our understanding regarding different adverse outcome pathways in shrimp bodies, it is still difficult to confirm this new contaminant class as being a serious hazard for shrimp in aquaculture. The lack of information concerning the toxicity and bioaccumulation of GBHs-PE microplastics in shrimp requires additional time and effort to assess the health risks to shrimp and consumers, interfering with providing guidelines for sustainable shrimp production to reduce the risks of introducing microplastic-pesticde contaminants in the food supply.