Along with directly impacting the well being, humans also have the potential to indirectly threaten marine populations. The ecologic and climactic changes that arise due to human activities can result in the spread of infectious diseases.
As marine life becomes more increasingly exposed to humans and 
domesticated and feral animals, the prevalence of infectious disease will increase. Animals that forage close to areas of human activity could be increasingly affected by exposure to contaminated waters from sewage and freshwater runoff. For example, the parasite Toxoplasma gondii is transmitted primarily through cat feces and reaches ocean waters through contaminated runoff. Over the past decade, there have been incidences of monk seal mortality due to T. gondii infection. Because the overall population of monk seals is declining, it is even more troublesome that the risk of encountering diseases and contaminants is likely to increase. In 2010, there were only 1,100 monk seals left in the wild. If you have a cat, please do not flush its litter down the toilet; sewage treatment doesn’t always kill the parasite’s eggs.
Exposure to environmental contaminants such as pollutants and certain trace elements can compromise animals’ immune responses, which will result in increased risk of infectious diseases. For example, in the late 1990s, high adult mortality rates were seen in sea otters, with the major cause of death being infectious disease.
As inhabitants of this planet, we have a responsibility to help these creatures that we live with. We need to be more responsible about the impacts we have on both the environment and animal life.
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