Well, considering our bodies all eventually end up feeding lower animals, plants, and bacteria, it can't be
that fatal to them.
Edit: If you want way too much detail in answer to your question: http://www.chemet.com/assets/1/6/Copper_and_the_Ocean_Enviro... The most relevant bit is probably this bit on the bottom of page 5 and into page 6: "A study was performed to determine if pen-raised salmon were bioaccumulating copper from the antifouling coatings on the pens (20). Five pens were used - three of which were treated with cuprous oxide containing antifouling coatings and the other two were left untreated. The concentrations of copper in the muscle and liver of the salmon were measured, Figure 7. It was found that there was no correlation to pen treatments. It was speculated that the reason for this is the leaching of the copper was sufficiently slow such that the natural homeostasis of the fish and their detoxification processes are not compromised
and that the leached Cu ion is reduced by complexation with organic and inorganic substances in the seawater."
It isn't clear to me if these "pens" were enclosed or not; if they were then there really doesn't seem to be much reason to worry about copper antifouling.
The article also says "Copper is an essential element required for normal growth in all plants and animals. As such, it is considered a normal constituent in the ecosystem
in both soil and water where its presence is partially due to the metabolic by-products of plants and animals as previously discussed." The oceanic concentration of copper is given as 0.25ppb, which comes out to 340 million metric tons of copper in the oceans overall. I suspect that, like many do with "radiation", we tend to casually assume the normal concentration in the world is zero, thus rendering any human addition to the world an infinite-percent increase, but the natural world is messier than that.
I thank you for your question, the research was interesting.