Give examples of point-source and nonpoint-source pollutants, and describe how each one affects marine ecosystems

Question

What will be an ideal response?

Answer 1

Point-source marine pollutants are those that can be traced back to a single source. Large oil spills are a prime example of point-source pollution. The Deepwater Horizon oil spill in the Gulf of Mexico spilled millions of gallons of oil into the Gulf. Such oil spills coat birds with oil and prevent them from being able to fly. The oil also suffocates animals, kills vegetation along coasts, and has toxic effects on marine ecosystems for years. Small-scale oil seepages and spills from myriad watercraft would be an example of a nonpoint-source pollutant. Another point-source pollutant would be municipal sewage released by a city into the ocean. Sewage contains pathogens harmful to humans and marine life, and it also contains high levels of nutrients that can cause eutrophication, potentially leading to hypoxic conditions and the death of marine life. Such conditions can also be caused by nonpoint-source pollution from fertilizers applied to agricultural fields. Excess fertilizers can run off into local waterways that flow into larger rivers that eventually flow into the oceans, thus adding nutrients such as phosphorus and nitrogen to marine ecosystems. Solid waste such as trash would generally be considered a nonpoint-source pollutant. Trash enters the ocean through various routes, such as blowing or washing from shore, accidental and intentional dumping from ships, and abandoned fishing lines and nets. Animals can become entangled in such debris, and many marine animals mistake the trash as food and ingest it, with disastrous consequences. Animals can choke on larger items, and smaller items can fill the stomachs of marine creatures, causing starvation.