Conclusion
Marine chemical pollution is an important driver modulating the
structure and function of microbial communities. Spatial clines in the
intensity and magnitude of this driver can result in different patterns
of environmental filtering, even across short geographic scales.
However, for microbial communities associated with marine animal hosts
(e.g., the sea cucumber H. leucospilota ), there are additional
mechanisms influencing their composition and abundance. Such mechanisms
are underpinned by intrinsic characteristics of their host (e.g., body
compartments, biochemistry composition, immune systems), resulting in
intra-individual differences in associated microbiomes, and their
divergence from the environmental source. These findings support the
hypothesis of an intrinsic capacity of the host to regulate its
microbiome. Such regulation favours specific microbial functional
pathways that may play an important role in the survival and physiology
of the animal host, particularly in high polluted areas. Despite the
observed differences in the environment and sea cucumber hosts, there
was a small component of the microbial community (core microbiome) that
was constant across the pollution cline and the animal body parts,
suggesting that other mechanisms are also involved in the control of
microbial communities in these animals.