Effects of Water Pollution [Part 2]
Marine Debris
Marine debris is basically trash in the ocean. Trash fouls inland waterways too, for sure, but trash seems to be a particular problem in our seas.
The debris includes escaped inland trash and garbage thrown overboard by ships and boaters—plastic bottles and bags, six-pack rings, cigarette butts, Styrofoam, etc. Marine animals can swallow the trash items, which often look similar to prey they would normally eat, or the trash item may have barnacles or other delectables attached and is inadvertently ingested with the food. For instance, sea turtles will eat a plastic bag believing it to be a jellyfish. The bag can cause an intestinal blockage and sometimes death.
A new and potentially devastating effect of marine debris is emerging. After years of degradation at sea, plastic breaks up. The plastic has not biodegraded but rather has disintegrated into very small pieces. Marine animals near the bottom of the food chain are now ingesting these teeny-tiny little pieces of plastic pollution. How far up the food chain the stuff will go is unknown.
Discarded or lost fishing gear—line, rope, nets—and certain trash items can get wrapped around marine animals fins or flippers, causing drowning or amputation. Marine debris can also degrade coral reefs, sea grass beds, and other aquatic habitats.
Thermal Pollution
It's easy enough to see how discharging the heated-up water from a power plant into a river could cause problems for aquatic organisms used to having their water home stay at a fairly specific temperature. Indeed, industrial thermal pollution is a problem for our waterways—fish and other organisms adapted to a particular temperature range can be killed from thermal shock, and the extra heat may disrupt spawning or kill young fish.
Additionally, warmer water temperatures lower the dissolved oxygen content of the water. That's a double-whammy to aquatic organisms, since the warmer water also causes them to increase their respiration rates and consume oxygen faster. All this increases aquatic organisms' susceptibility to disease, parasites, and the effects of toxic chemicals.
Global warming is imparting extra heat to our oceans, which have absorbed about 20 times as much heat as the atmosphere over the past half-century. The ocean is a complex system, and scientists don't know yet what all of the effects of this type of "water pollution" will be, but here are some likely ones:
- Sea levels will rise (because of thermal expansion and melting ice), increasing coastal flooding and inundation.
- There will be more intense hurricanes as they gather additional strength from warmer surface waters.
- Temperature-sensitive species like corals will see tougher times. The Pew Oceans Commission notes that an increase in the mean sea-surface temperature of only 2 degrees F could cause the global destruction of coral reef ecosystems.
- Increasing sea-surface temperatures are associated with the northward spread of a oyster pathogen in the eastern US. Similar cases are highly likely.
Noise Pollution
"Noise pollution" from ship engines and sonar systems make it difficult for marine mammals like whales, dolphins, and porpoises to communicate, find food, and avoid hazards. Powerful sonar systems operating at certain frequencies have been implicated in whale beachings and may cause damage to marine mammals' sound-sensitive internal structures, causing internal bleeding and even death.
Frequent or chronic exposure to both high- and low-intensity sounds may cause stress on all higher forms of marine life, potentially affecting growth, reproduction, and ability to resist disease.