Ocean pollution crisis

In eight of ten cases, pollutants identified in the sea originate from  terrestrial sources. As industrial or household waste, they are either  discharged directly into the water, escape from poorly functioning  wastewater treatment plants, are washed from the fields and streets by  rainfall from above, or are leached from landfills and garbage dumps  into subterranean water channels or streams. Litter and plastics are  also ­carried to the sea by the wind. The remaining input of pollu­tion  occurs directly at sea, as a result of fishing and aquaculture or from  shipping.
Winds and ocean currents transport garbage and pollutants to  the most inaccessible regions of the world’s oceans. Evidence of the  pollution can be found on remote islands, in the polar sea ice and in  deep ­ocean trenches.

Pollutants especially hazardous for marine biotic communities are those  that are long-lived and that accumulate in the food webs. These are  characteristic, for example, of the group of persistent organic  pollutants (POPs), which includes many pesticides and industrial  chemicals.
The consequences of contamination are manifold and are  distinguished according to the species affected and pollutant concerned.  Known environmental pollutants cause diseases such as cancer, evoke  deformities and behavioural changes in marine organisms, impair  reproduction in affected species and can cause death in contaminated  individuals. As a rule, predators at the highest trophic levels are  especially impacted by environmental pollutants. These include sharks,  toothed whales and seals. Animals that come into contact with plastic  waste are in danger of being trapped, or of ingesting the plastic and  starving with a full stomach. At least 700 animal species have now been  identified for which plastic in the ocean can be a deadly hazard.

The international community is attempting to limit the input of  pollutants into the seas through a variety of international agreements  as well as trans-regional and national regulations. The prohibition of  selected persistent organic pollutants by the Stockholm Convention, for  example, is delivering results. The concentrations of these pollutants  in the sea are declining.
But in many other cases, politicians and scientists are  facing the problem that regulatory authorities are not always fully  informed about the chemicals that are used in popular products, or about  the impacts ­these ingredients would have should they someday end up in  the sea. In many cases, the risk analyses required for a ban on  dangerous substances are only possible after excessive quantities of  them have already been introduced into the ocean and researchers are  able to demonstrate the links between pollutant input and ecosystem  destruction.
An end to the crisis of marine pollution will not be  possible until a large proportion of the households and businesses  around the world are connected to func­tioning sewage and solid-waste  management systems, until substances toxic to the environment and  carbon-based plastics are replaced by biodegradable alter­natives, and  the use of chemicals and plastics is ­limited to closed-loop systems.