Combined effects of polyamide microplastics and the pathogenic bacterium
Vibrio parahaemolyticus on the immune parameters of Mytilus coruscus
The thick-shell mussel Mytilus coruscus is a crucial marine ecological indicator species, sensitive to environmental changes and pollution. Its population size, growth condition, and reproductive capacity serve as key indicators of the health of the marine environment (Qian et al., 2023). Additionally, as a valuable marine economic resource, M. coruscus is widely distributed in coastal areas, has a long growth cycle, filters plankton from seawater, and plays a vital role in main- taining marine ecosystem balance. It is also extensively used in food processing and aquaculture, providing a rich protein source for humans (Li et al., 2010). However, the deteriorating environment, with pollut- ants like microplastics and bacteria, threatens the survival and repro- duction of M. coruscus. Increased microplastics in the environment raise the risk of ingestion and adsorption by M. coruscus (lvarez-Ruiz et al.,2021), while bacterial contamination can lead to diseases in M. coruscus (Robert-Pillot et al., 2004), ultimately affecting their growth and sur- vival. Thus, studying the biological characteristics and environmental responses of M. coruscus is significant for monitoring and assessing marine ecosystem health.
In recent years, increased human activities have led to unprece- dented pollution and pressure on the marine environment, with pol- lutants such as microplastics and the rise in pathogenic marine bacteria becoming significant environmental issues (Díaz-Mendoza et al., 2020; Hder et al.,2020). Microplastics are plastic particles smaller than 5 mm that are prevalent in the marine environment (Ajith et al., 2020). These tiny particles originate from the decomposition of various plastic products, leakage during production, and plastic waste from human activities. Due to their small size and light weight, microplastics can be transported across different marine compartments, including surface
waters and sediments (Turan et al., 2021). The presence of microplastics poses several hazards to marine life (Ma et al., 2020). Firstly, marine organisms may accidentally ingest microplastics, mistaking them for food(Williams, 2017). These particles can accumulate, leading to malabsorption of nutrients, internal organ damage, and even death. Secondly, microplastics can adsorb organic pollutants (Fu et al., 2021; Bhagat et al., 2022), potentially leading to the enrichment and spread of these pollutants in the ocean and disrupting the environmental balance within organisms. Additionally, microplastics can impact physiological processes such as behavior, growth, and reproduction, thereby affecting the stability and health of the marine ecosystem (Guzzetti et al., 2018; Khalid et al., 2021; Ma et al., 2020). Polyamide microplastics (PA-MPs) are a common type of microplastic known for their high occurrence in the marine environment (Lara et al., 2021).
Vibrio parahaemolyticus is a group of bacteria widely distributed in marine environments, including seawater, bottom sediments, and aquatic organisms (McCarter, 1999). These bacteria, characterized by their curved morphology typical of the Vibrio family, can rapidly pro- liferate under favorable conditions (Wang et al., 2015). In marine en- vironments, V. parahaemolyticus primarily interacts with its host as an opportunistic pathogen, with its pathogenicity influenced by environ- mental conditions (Lovell, 2017). While it can form mutualistic re- lationships with certain marine organisms, V. parahaemolyticus is also known to compromise the immune systems of marine species like shellfish, leading to diseases and infections under stressful conditions (Ndraha et al., 2020; Williams et al., 2017). In M. coruscus, exposure to
V. parahaemolyticus in contaminated environments can trigger immune responses, release harmful toxins, and increase susceptibility to in- fections, potentially resulting in disease outbreaks (Li et al., 2019; Wang et al., 2015).
Therefore,it is crucial to thoroughly investigate the effects of microplastics and bacteria on the immune system of M. coruscus and their roles as ecological indicator species in the marine ecosystem. Un- derstanding these impacts will help protect the marine environment and maintain ecological balance. By monitoring the health status and envi- ronmental responses of the M. coruscus population, we can identify and address abnormal changes in the marine environment. This approach is essential for safeguarding the stability and healthy development of marine ecosystems.