Impact of Climate Change on the Gut Microbiome of Fish and Shellfish

The impact of global warming on animal and plant biodiversity is well-known. Consequently, the impact of climate change on the gut microbiota of fish and shellfish is bound to be there and getting momentum, and in the recent past, considerable research work has been carried out in such niche areas of science. It is well known that the impact of climate change on the gut microbiota could lead to possible dysbiosis with strong consequences on hosts and ecosystems. These changes may be caused by a number of environmental factors particularly rising temperatures, changes in water salinities, pH, turbidity, depletion of oxygen levels, pollutants, etc. that may lead to an increase in disease prevalence in the habitat ecosystems. Hence, understanding the factors affecting host–microbiota interactions with cultivable organisms would improve predictions on biodiversity responses to climate change. Several environmental factors which act as stressors can disrupt the strong relationship between hosts and their associated microbiomes leading to dysbiosis and enhancing the chances of host diseases. Hosts and their associated microbiomes form a coherent biological entity termed "holobionts"—that must be studied together to properly understand biological systems and how they will be impacted by climate change. This is particularly crucial for habitat-forming organisms because impacts on these holobionts can affect entire ecosystems. There are several reports indicating that the capacity of organisms to adapt to new habitat conditions basically depends on their plasticity attributes, of which their gut commensal microbiota might be an essential impact factor. Particularly in aquatic organisms, which inhabit the aquatic environment, the complex and dynamic microbiota have significant effects on health and development. However, an understanding of the relative contribution of internal sorting and colonization processes of the microbiota in the gut system is still not clear and research investigation is required in this particular area on a priority basis. Besides environmental factors, pollutants in the form of contaminants and toxins present in the environment may also influence the fish gut microbiota, and also other kinds of chemicals such as pesticides, heavy metals, and antibiotics can also induce gut microbiota dysbiosis associated with changes in the intestinal mucus layer and inflammation in the digestive tract in fish, thereby reducing the ability to absorb nutrients.