@Mortie31 here are a couple quotes as well:
1. Can the presence of inorganics/metals (focusing particularly on aluminium, copper, chromium and zinc) suppress the immune system of marine organisms?
Yes. There is literature evidence that all named metals but also other metals, organic chemicals and other stress factors can suppress the function of the immune system in a wide range of marine organisms. Further, in the aquatic environment, metals and organic chemicals are not present as individual compounds but mixture effects need to be taken into account.
All species reviewed have different levels of immunocompetence. Invertebrates mainly have innate, nonspecific response, while fish have all functionalities of innate and adaptive (acquired) response, which is more targeted, albeit in an evolutionary older state than mammals. Finfish have a highly developed immune system, while the immune system of sharks is more primitive. Thus the cellular effects of metals and organic chemicals have a degree of (dis)similarity in different species that is related to the degree of (dis)similarity of the immune functions.
2. What concentrations and exposure period are required in order to cause immunosuppression and/or decreased resistance to parasites and diseases?
There is no clear-cut answer to this question. Suppression of molecular immune responses may occur without reduced disease resistance. Many parameters related to immune function can be measured but there is no one single endpoint that can be associated with a well functioning immune system. Effects on the immune system are dependent on species, time, concentration and environmental factors. At low exposure levels, stimulatory effects may also occur but at higher exposure levels, mainly immunosuppressive effects are observed. Sometimes suppression is followed by recovery or even stimulation. Overall immune response is multifactorial and influenced by a combination of environmental factors and species-specific traits.
3. Can the presence of inorganics/metals (focusing particularly on aluminium, copper, chromium and zinc) increase the susceptibility of organisms to opportunistic parasites and diseases?
Yes. There is quite extensive evidence from aquaculture research and practice on the relationship between immunosuppression and susceptibility to pathogens and parasites, be the cause of immunosuppression chemical induction or other stressors. In wildlife, the evidence is more anecdotal or epidemiological, i.e., in many (but not all) cases, higher levels of chemical pollutants are found in animals affected by various parasites and diseases. Some examples from the literature are reviewed in this report.
https://www.researchgate.net/profil...ure_review/links/555b59d408aec5ac22322bd0.pdf