By Nat Spring, Senior Research Director, Earthwatch

Marine pollution is a growing problem, coming from a variety of sources and having a multitude of impacts.  Physical pollution includes sewage, rubbish (particularly plastic litter), excess nutrients in run-off from the land, oil and hazardous chemicals.

Untreated sewage is pumped into the sea from coastlines around the world.  For example, Guernsey in the Channel Islands has been in the press in recent years because around16,000 tonnes of raw sewage is pumped into the sea from the island each day1.  Many countries have no sewage treatment system whatsoever.  Raw sewage entering the sea increases nutrient loading which leads to eutrophication.  This is a process by which excessive growth of algae causes oxygen deficiency in the water, and in extreme cases, ‘dead zones’ are created where the water is so low in oxygen that it is devoid of marine life.  The same effects are seen in areas where high levels of run-off from agricultural land introduces excess nutrients into the water, particularly where mangroves and seagrass habitats, which would normally absorb the nutrients, have been removed.

Around 500 million gallons of oil enters the ocean each year through ships pumping their bilge waters, vessels running aground and industrial and municipal waste.  Old shipwrecks are another source, for example, at the world famous Chuuk Lagoon in Micronesia Earthwatch volunteers working with scientist Bill Jeffery discovered World War II wrecks were leaking environmentally damaging amounts of oil2.  The short term effects of oil spills on the marine environment are fairly well researched, but much less is known about the long-term damage.  Such research is vital, for example Dr. Peter Barham, lead scientist on Earthwatch project South African Penguins, is trying to improve our knowledge by studying the effects on reproductive success of the Vulnerable (IUCN Red List3) African penguin after the Treasure oil spill in 2000.

Waste dumped into the ocean, accidentally or on purpose, often does not dissipate or become evenly diluted, but instead becomes caught up in large circular ocean currents and concentrated in certain areas, such as one area in the Pacific to the east and west of Hawaii, which has become known as the “Great Pacific Garbage Patch”.  Plastic waste is a major cause of mortality for turtles, seabirds and marine mammals, filling up their stomachs so they cannot feed or digest properly. UNEP estimates numbers of seabird deaths caused by plastic debris to be over one million, and for marine mammals over 100,000.  In 2006 it was estimated that every square mile of ocean contained 46,000 pieces of floating plastic – a number which is increasing due to the length of time it takes for plastic to degrade in the natural environment (up to a century).  Going “plastic bag free” is an easy step you can take to help reduce this problem!  And no one needs reminding how important it is to dispose of your waste carefully, always remembering to “reduce, re-use and recycle”4 where possible.

Noise pollution also affects the marine environment - from shipping, offshore oil and mining activities, military activity, recreation and fish farming.  The noise generated can be heard for miles by marine life due to the huge distances that sound can travel in water.  Excessive noise pollution of any kind can deter marine life from an area. Particularly affected are cetaceans (whales and dolphins) because they depend on sonar for feeding, communication and navigation.  Military sonar can induce cetacean strandings, haemorrhaging, decompression sickness, disruption to mating and feeding behaviour, mask communication calls and cause displacement from migratory routes.  Strandings have been documented on numerous Earthwatch projects, and scientists on Whales and Dolphins of Abaco Island in the Bahamas encountered a mass stranding event in 2000, discovered later to have been caused by military sonar testing.  Data collected on the project was used in a comprehensive report to the Government of the Bahamas, helping them to understand the impacts of military activities and develop effective mitigation policies for the future to reduce their impact on marine life and prevent such events from happening.

1 Story from the Telegraph newspaper online http://www.telegraph.co.uk/travel/travelnews/2013966/Guernsey-attacked-over-dirty-beaches.html

2 World War II wreck oil leaks in Chuuk Lagoon:
New Scientist report
http://www.newscientist.com/article/dn14645?DCMP=ILC-hmts&nsref=news1_head_dn14645
Earthwatch report
http://www.earthwatch.org/europe/newsroom/science/news-3-truk.html
http://www.earthwatch.org/europe/downloads/Newsroom/Oil_leaking_Chuuk_report.pdf

3 IUCN Red List http://www.iucnredlist.org/

4 http://www.reducereuserecycle.co.uk