Pathogens

As on land, large numbers of pathogenic micro-organisms are found in the world's oceans, and these are a natural part of functioning ecosystems. In addition to these, further pathogens have been linked to human activities. These include some which are naturally occurring marine pathogens, and which in this Atlas are covered under invasive species, but others which originate from terrestrial sources. The major concern from the latter comes from their human health impacts .

The major types of pathogens occurring near human settlements are bacteria and viruses, largely originating from untreated sewage entering into coastal waters. These include Hepatitis A, campylobacter, salmonella, cholera and typhoid. Whilst most of these pathogens are unable to survive or reproduce in marine waters, many can survive for a few days to a few months. During this period they may be ingested directly by bathers, or may become lodged within the bodies of filter-feeders such as shellfish which may then be harvested for consumption by humans.

Unlike the impacts on humans, the impact of land-based pathogens on marine organisms is not well understood, but may be important. There is growing evidence that such impacts may occur even over very long distances. There is, for example, ongoing transport of dust from North Africa towards Central and South America, and there is now considerable evidence that diseases affecting corals in this region may have been driven by the import of fungal pathogens carried with this dust. The Aspergillosis disease causing widespread mortality of gorgonian sea fans, for example, has been linked to Aspergillus fungi which cannot survive for long in sea water. There is some evidence that they may have been transported with African dust.