There are many sources of pollutants, which are contaminating our oceans and negatively affecting marine life and ecosystems. Pollutants include different types of litter or foreign marine debris, chemicals and noise.

 

Types of Ocean Pollution

 

Marine Debris 

Marine debris: Items made by humans that are discarded, disposed of or abandoned and in the coastal or marine environments.

Foreign marine debris (aka from human sources, not naturally occurring debris) can be found in every ocean – plastic has been found at the bottom of the deepest trenches, frozen into sea ice and floating at the surface. Marine debris degrades the health of marine ecosystems and can cause harm to marine life.

Plastic makes up around 80% of all marine debris across the world. Plastic doesn’t just disappear, it breaks down over time into smaller and smaller pieces called ‘microplastic’. Most plastic is not reused ends up as litter or landfill.

• It’s estimated that the equivalent of a garbage load of plastic ends up in our oceans every minute.
• 32% of the 78 million tons of plastic packaging produced globally each year flows into our oceans (World Economic Forum).
• By 2050, there could be more plastic than fish in the oceans and in some areas, this is already the case.

Plastic marine debris contains harmful additives and chemicals and can act as a magnet for other toxins from the surrounding air or water. The degradation of plastic is slow and constant, where larger plastic objects break down over time and increase levels of microplastics exponentially.

 

Where does marine debris come from?

Most marine debris originates from land and is washed down rivers, drains and sewage systems. Some marine debris is also discarded at sea from recreational boats, ships and fishing boats.

Most marine debris is discarded everyday items including; toothbrushes, pens, coffee cups, balloons, balloon strings, plastic bags, plastic bottles and bottle tops.

Marine debris can travel thousands of kilometres from the source in currents and can move across oceans. It accumulates in massive ocean circular currents called gyres. There are five gyres in the oceans where higher concentrations of plastic pollution are prevalent.

Rivers are the main source of plastic marine debris, which is swept downstream into the coastal waters, and eventually out into the greater ocean. It’s estimated that 1000 rivers around the world contribute 80% of the marine debris.

Discarded, abandoned or lost fishing equipment such as nets, line, hooks and buoys makes up another large amount of marine debris. Most fishing nets and lines are made of plastic and also contribute to the level of plastic pollution in our oceans. Over 46% of the marine debris in the Great Pacific Garbage patch gyre consists of discarded fishing gear. 

Lost fishing nets and lines, called ghost gear, float along currents and continue to indiscriminately catch marine life that can become entangled or ingest the gear. Lost fishing gear not only impacts the environment but can also cause significant economic impacts to communities.

• It’s estimated that 2% of all fishing gear from commercial fisheries used worldwide ends up as pollution in the world’s oceans.
• The amount of longline fishing gear littering the oceans can circle the Earth more than 18 times (740,000kms).
• 14 billion longline hooks, 3000 km² of gill nets, 75,000km² purse seine nets and 218km² trawl nets litter the oceans each year.

Much more fishing gear is also lost, abandoned or discarded from recreational fisheries activities. This includes crab pots, fishing line, fish hooks, gill nets, ropes and other equipment.

 

Most items of marine debris that are found along the beaches of Australia are:

1. Hard plastic remnants
2. Cigarette butts and filters
3. Plastic lids
4. Foam insulation and packaging
5. Soft plastic remnants
6. Plastic food packaging
7. Plastic drink bottles
8. Fishing line
9. Broken glass and ceramic
10. Straws/confection sticks/cups/plates/cutlery

(Source: AMDI Database, Tangaroa Blue)

 

The impacts of marine debris

It is estimated that over 900 marine species, from micro-organisms, crustaceans and fish, to turtles, whales and sharks, have been harmed by foreign marine debris that has caused injury, illness and death.

Ingestion

Animals often mistake marine debris, such as microplastics, balloons, plastic bags, confectionary wrappers and plastic bottle caps, for food. Some marine debris can look very similar and imitate prey items. For example, plastic bags look very similar to jellyfish, a primary prey source of loggerhead turtles. Polystyrene balls and small plastic objects can look like fish eggs and crustaceans to sea birds. 

Ingestion of marine debris can cause blockages in the digestive systems of marine animals. In addition, ingestion of plastics also allows toxic chemicals to enter the food chain (including humans who consume seafood). Toxins from pollutants can bioaccumulate up the food chain as animals are consumed by higher-order predators.

• It’s estimated that 34% of marine turtles in Moreton Bay, Queensland have ingested marine debris including food wrappers, packing, plastic bags, fruit sticks and balloons (Schuyer et al. 2019).
• Ingestion of plastic is likely to be responsible for over 18% of albatross mortalities in the Southern Hemisphere, with single use plastics, including plastic bottles and balloons, the major contributor (Roman et al. 2020).
• Plastic or garbage whales are becoming more common around the world, washing ashore with stomachs full of foreign matter. Many of these species are deep diving, wide ranging species including sperm whales and beaked whales. A case of an adult sperm whale that wash ashore deceased at Seilebost Beach, Isle of Harris, Scotland, in 2019, had over 100 kilograms of trash in its stomach. Items included gloves, plastic bags, rope, plastic cups, packing straps, tubing and net.
• Humpback whales are estimated to ingest 200,000 pieces of microplastic every day (Kahane-Rapport et al 2022).
• Zooplankton that ingest microplastic also consume 40% less carbon biomass and sink slower. This can have a significant impact on the ‘carbon pump’ of the ocean.

Entanglement

• Entanglement and ingestion of fishing gear is one of the main threats to marine megafauna including dolphins, whales, seals, turtles and sharks. Entanglement in fishing gear and other marine debris can restrict mobility, cause starvation, infection, amputation, drowning and asphyxiation of the marine animal.
• Over 35% of Indo-Pacific bottlenose dolphins in Moreton Bay are estimated to have injuries and mutilations (e.g. amputated dorsal fins) from entanglement in fishing gear (Hawkins et al 2022).

In Australia, ‘Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris’ has been listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).

 

Chemical Pollution

Contamination of our waterways and oceans from chemicals can be an ‘invisible threat’. Often not visible at first, chemical or nutrient pollution, is a growing issue and can have dire and long-term consequences. 

Chemical pollution can cause increased concentrations of chemicals, such as nitrogen and phosphorus, promoting algal blooms which can be toxic to wildlife. Algal blooms can deplete the water of oxygen, creating dead zones where life struggles to survive.

• Nitrogen discharges from rivers into the sea rose by 43% between 1970 and 2000.
• The amount of chemicals entering the ocean is estimated to have increased by 12% between 2003 and 2012 (although in some areas, it is decreasing).

The most dangerous chemicals are persistent, bioaccumulative, and toxic substances. Many chemicals are extremely slow to break down and become more concentrated further up the food chain.

 

Where does it come from?

Sources of chemical pollution include fertilizers and animal manure, which are the primary source of nitrogen and phosphorous through run-off. Around 20% of nitrogen fertiliser is lost through surface run-off or leaching into groundwater.

Other sources include; crude oil and petroleum products, paints, antifoulants, pesticides, pharmaceuticals, personal care products, sewage, stormwater, burning of fossil fuel, aquaculture, domestic waste, cleaning products and fire retardants.

Atmospheric depositions from burning fossil fuels also contributes to nitrogen input in the ocean and can cause severe eutrophication in the ocean and can lead to toxic algal blooms.

Personal care products that contain cryptic chemicals, e.g. oxybenzone, can negatively impact coral growth and reproduction. These can include products like sunscreen, so be sure to check the ingredients before purchasing and choose reef safe and earth friendly options.

 

The impacts of chemical pollution in our oceans

Chemical pollutants that are endocrine disruptors and teratogens can inhibit the ability of marine animals to reproduce or reduce offspring survival, and present a growing concern.

Due to their positions as apex predators, toothed whales and shark species can have some of the highest levels of chemical contamination due to bioaccumulation; through uptake of contaminants in food and or offloading contaminants through lactation to offspring. There are strong links between the susceptibility of diseases due to suppression of immune function and the presence of accumulated contaminates (e.g. PCBs and mercury). 

– Accumulation of organochlorine compounds (DDTs, PCBs, HCB) have been found in Australian humpback dolphins and snubfin dolphins along the east coast of Australia, above thresholds which immunosuppression and reproductive anomalies occur (Cagnazzi et al., 2013; Weijs et al., 2016 )

– PCBs have been detected above National Food Authority Maximum Residue Limits in commonly consumed fish species including sea mullet, yellowfin bream and silver biddy in the Georges/Cooks Rivers and Sydney Harbour (Roach & Runcie 1998).

– Global killer whale populations are at a high risk of decline and potential collapse due to PCB toxicity (Desforges et al., 2018)

Noise Pollution is another major type of pollution in our oceans. This topic we will address separately