Aquatic biomonitoring: Importance, challenges, and limitations

Aquatic contamination caused by micropollutants, such as pesticides, medicines, hormones, metals, and microplastics, is an issue affecting ecosystems worldwide (Bertoldi et al., 2020; Calvo et al., 2021; Chi̧tescu et al., 2021; Zind et al., 2021). It is therefore extremely important to find methodologies that address the specificities of regional environmental conditions and portray the real effects of exposing living organisms to xenobiotics in situ. Furley et al. (2018) identified priority topics for the development of research focused on achieving environmental sustainability in Latin America; the following topics stood out among those highlighted: (i) developing, improving, and harmonizing methodologies to help identify contaminants and their metabolites in environmental matrices (including biota); (ii) predicting the risks and effects of individual and mixed contaminants, as well as abiotic changes, on different ecosystems; and (iii) improving environmental management and regulatory tools. Therefore, biomonitoring studies are emerging as very useful tools to help us better understand the issues described by Furley et al. (2018). Accordingly, studies carried out in the laboratory environment play an important role in providing answers about the toxicity, pathways, and action mechanisms of contaminants. These studies are conducted in an artificial environment, which enables parameters such as environmental physical–chemical variables, contaminant concentrations, and exposure time to be controlled. In the natural environment, in addition to a complex and diffuse mixture of xenobiotics, abiotic fluctuations, mainly the seasonal ones (e.g., rainfall, temperature, and pH), can occur in aquatic environments, and change contaminants' behavior (e.g., toxicity, solubility, and availability) and, consequently, affect aquatic organisms. Thus, an assessment of aquatic organisms capable of living in these environments can provide information about the bioaccumulation of different contaminants in the tissues of, or metabolic changes observed in, individuals subjected to long-term exposure to these contaminants. It is clearly necessary to develop and consolidate specific methodologies to be applied in biomonitoring studies involving different climatic and environmental features. This is important because protocols based on the features of a specific region are not suitable for standardization worldwide since even regions relatively close to one another can present significant climatic, environmental, and faunal differences. Therefore, the use of native species is recommended due to their incidence and ecological relevance (Brodeur & Poliserpi, 2017). In addition, other limitations observed in biomonitoring studies must be addressed since aquatic environmental contamination occurs in all regions worldwide, even in the most remote ones (Bessa et al., 2019). It is difficult to find contamination-free sites that can be used as controls or references in scientific studies. Biomonitoring studies play a vital role in managerial measures and decision-making processes related to the sources of contaminants' release into water and help improve environmental quality as a whole. Biomonitoring provides relevant information for the advancement of science since it helps promote a better understanding of phenomena taking place in aquatic environments. Moreover, it enables social well-being by ensuring the use of healthy water resources by local populations. It is therefore essential to understand the effects of xenobiotic mixes on aquatic organisms living in their natural environments to determine the health of these ecosystems, as well as the future consequences of likely exposure to these contaminants. Biomonitoring studies play a vital role in managerial measures and decision-making processes related to the sources of contaminants' release into water and help improve environmental quality as a whole.