31 Marine Pollution (Types and Sources)
There are a number of different types of marine pollution that come from a variety of sources. These include inorganics such as metals, organic contaminants including the pesticide Dichlorodiphenyltrichloroethane (DDT) and flame retardants such as Polybrominated Diphenyl Ethers (PBDE), nutrients including nitrogen and phosphorus, biological contaminants and litter including plastics. Understanding the pathways from the source to bioaccumulation and impact are essential to allow for adequate management.
‘Piles Of Garbage By The Shore’ by Lucien Wanda used under a Pexels License
Marine Pollution Introduction
Pollution of the marine environment is caused by a wide range of activities, and it is commonly reported that as much as 80% of marine pollution is a result of land-based activities (Figure 1). Fertiliser runoff from agricultural land has been highlighted as the cause of the dead zone in the Gulf of Mexico. The Northern Pacific Gyre Garbage Patch is an example of the consequences of poor solid waste management on a global scale. The Fukushima Daiichi nuclear accident in 2011, ocean acidification, ports and shipping, and multiple other land-based point and non-point source (also known as diffuse source) inputs highlight the challenges for minimising the threat of marine pollution. Contemporary research publications related to marine pollution not only cover the traditional focus on oil spills and radioactive waste dumping, but include a wide range of existing and emerging chemicals and substances of concern such as pesticides, pharmaceuticals, phthalates, metals, fire retardants, nano and micro-particles, and mixtures of these. The growing body of knowledge has aided our understanding of how these substances behave in the marine environment and how organisms interact with them, helping to define the study of marine pollution.
Marine pollution is a challenging field of study requiring a multidisciplinary approach to assessment and management that incorporates social, environmental, economic, and political considerations (e.g. Ducrotoy and Elliott 2008). Importantly, we must also consider the impacts of pollution in combination with other stressors that affect the health of marine ecosystems, such as over-exploitation and harvesting of marine species, natural disasters, diseases, and exotic species.
Our consumption as individuals and communities has inevitably contributed to global-scale demands for raw materials, industrial chemicals, pharmaceuticals, and the associated waste production and pollution caused by the way we live in modern society. Indeed, our human footprint varies between different social and cultural circumstances across the globe. On a per capita basis, higher income countries are generally the greatest consumers of resources. At the same time, there is a large increase in consumerism in middle-income countries with the expansion of a middle-class population who have more money to spend on products and services (Balatsky et al. 2015). Low-income countries tend to have a per capita lower contribution to consumption, but also have fewer resources to manage the waste that is produced. Low-income countries also accept waste from high-income countries for payment and recycling, sometimes in working conditions that are harmful to human and environmental health (e.g. e-waste and plastics) (e.g. Makam 2018).
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Figure 1. Consider the different causes of pollution and how they might be managed differently
Diagram showing a coastal dwelling town, with 3 areas depicting pollution sources, movement and exchange.
Area 1 is the urban settlement and surrounding natural resource production and processing, which includes the following pollution sources and pathways:
- Mining and ore processing adjacent to tailings storage and tailings disposal
- Agriculture, forestry, grazing and feedlots adjacent to wetlands and the estuary
- Sheet and rill erosion
- Urban settlement, sewage treatment and ocean disposal and municipal solid waste storage
- With industrial ports, power generation and aquaculture adjacent to the ocean
Area 2 is the ocean, which includes the following pollution sources and pathways:
- Off flow from urban settlement activity, covered above
- Shoaling, dredging and resulting turbidity plume
- Transportation, shipping lanes, and oil spills
- Recreation and fisheries activities
- Oil extraction
- Deep water mining and resulting surface plumes, and
- Tailings disposal and deepwater tailings disposal, impacting plume shearing which in turn impacts zooplankton, phytoplankton and pelagic species
Area 3 is the atmosphere, which includes the following pollution sources and pathways: pollution pathways from mining, tailings storage and industrial ports, leading to atmospheric deposition (into the ocean) and gaseous exchange between the ocean and the atmosphere.
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What is the difference between an contaminant and a pollutant?
“Marine contamination occurs when the input of a substance from human and human-related activities results in the concentration of that substance in the marine environment becoming elevated above the naturally occurring concentration of that substance in that location”.
According to the joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP):
“Pollution is the addition by human activity, directly or indirectly, of substances or energy to the marine environment which results in detrimental effects, for example hazards to human health, hindrance to amenity use, recreational activities and fishing.”
Put simply, a contaminant is a substance present in the environment where it should not normally occur, or at concentrations above background levels, and a pollutant is a contaminant that causes adverse effects in the natural environment.
This text, image and its associated caption is from “Marine Pollution in Context” In: Reichelt-Brushett, A. (eds) “Marine Pollution – Monitoring, Management and Mitigation” 2023, by Amanda Reichelt-Brushett, which is licensed under CC BY 4.0, except for the introduction paragraph and emphasis (bolding) of words, which has been added by Trish Corbett.
Contaminant and their types, sources, distribution and transport types in the Marine Environment
Click on each tab below to learn more about they types, sources, distribution and transport of contaminants in the marine environment.
Contaminant types in the Marine Environment
Contaminant types in the Marine Environment
Trace elements
e.g. Arsenic (As), cadmium (Cd), copper (Cu), Iron (Fe)
Organometallic compounds
- e.g. Mono, di and tri-butyltin (TBT), methylmercury (CH3Hg+), and some pesticides
Agricultural chemicals
- e.g. Insecticides, herbicides, fungicides, and other specific pesticides and disinfectants
Nutrients
- e.g. Nitrogen (N) and phosphorous (P)
Persistent organic and halogenated chemicals
- e.g. Dioxin, fluorocarbons, organochlorines, organophosphates, organobromines
Hydrocarbons and dispersants
- e.g. Oil, gas, and some petroleum products, dispersants
Dissolved gases
- e.g. Carbon dioxide (CO2)
Pharmaceuticals
- e.g. Antibiotics, antidepressants, blood pressure and diabetes medication, birth control, anti-bacterial agents, illicit drugs, and veterinary products
Personal care and household products
- e.g. Soaps; sunscreens; disinfectants; surfactants; nanoparticles (e.g. zinc and titanium dioxide)
Pathogens
- e.g. Parasites, viruses, protozoans, and bacteria
Plastics and debris
- e.g. Plastic bottles; packaging and general rubbish; microplastics; fishing nets and lines; timber; metal; other building materials
Sediment
- e.g. Soil; clay; sand; fine sediment
Other
- Radioactivity and explosives
- Noise
- Thermal pollution
(Reichelt-Brushett, 2023)
Sources of Marine Pollution
Sources of Marine Pollution
Pollution is not always deliberate; a distinction can be made between intentional, accidental, and uncontrollable pollution (Figure 2). Furthermore, marine pollution may be slow and chronic or sudden and more acute. Sudden pollution events tend to be unintentional, and include accidents and natural dis-asters. Chronic pollution is often intentional and controlled, and may have a direct point source or nonpoint sources. Accidents are usually caused by factors or events that were unforeseen in risk assessment and/or are a result of inadequate risk minimisation strategies (Garrick 2008). This generally reflects a lack of knowledge and/or poor contingency provisions. Disaster events, such as cyclones/hurricanes/typhoons (e.g. Hurricane Irma, Cyclone Debbie, and Typhoon Hato all in 2017), floods (e.g. monsoon floods in India and Bangladesh in 2017, flooding and mudflows in California in 2018), and tsunamis (e.g. affecting Thailand and Indonesia in 2004, Japan in 2010, and Haiti in 2010) are largely uncontrollable, but can be major generators of pollution. Extreme events such as these create large volumes of marine debris and cause the breakdown of urban infrastructure such as sewage systems, and waste disposal and storage facilities. Extensive flooding during these events transports polluting substances from activities on land into marine environments.
This ‘sources of marine pollution’ text, image and its associated caption is from “Marine Pollution in Context” In: Reichelt-Brushett, A. (eds) “Marine Pollution – Monitoring, Management and Mitigation” 2023, by Amanda Reichelt-Brushett, which is licensed under CC BY 4.0, except for the introduction paragraph, which has been added by Trish Corbett.
Source and distribution of contaminants in the Marine Environment
Source and distribution of contaminants in the Marine Environment
All contaminants originate from a source and are distributed around the environment by physical forces such as winds, tides, upwelling, downwelling, currents, ocean circulation, rainfall, groundwater movement, and surface runoff. Throughout these distribution processes, biota come into contact with contaminants and may accumulate and transport them. The size and density of solid particles
influence their distribution and the contaminants that bind to them. In general, heavy or larger particles settle out first and deposit in higher energy environments compared to fine particles like clay. Clays (diameter < 2 μm) may remain in suspension for months or years and have a high surface area to volume ratio, and, therefore greater adsorptive capacity for contaminants (Reichelt-Brushett et al. 2017). Fine particles can potentially transport bound contaminants many kilometres from the original source (Figure 3).
The solubility of a contaminant also influences its distribution. Water-soluble substances will move readily in the marine environment as they will be dissolved throughout the water column and transported with currents and tides. Some water-soluble substances, such as metal ions, are charged and will adsorb to particulates. Similarly, insoluble substances will more commonly be associated with sediments, or float on the water surface.
This text, image and its associated caption is from “Collecting, Measuring, and Understanding Contaminant Concentrations in the Marine Environment” In: Reichelt-Brushett, A. (eds) “Marine Pollution – Monitoring, Management and Mitigation” 2023, by Amanda Reichelt-Brushett, which is licensed under CC BY 4.0
Transport of chemicals to biological systems
Transport of chemicals to biological systems
Many of the chemicals in the environment are naturally derived from compounds in plants, petroleum oils, or minerals in rocks. However, their chemical composition, concentration, and distribution through the environment have been altered by humans, usually as a result of an economic incentive (e.g. mining). Other chemicals are synthetic, produced in laboratories, and manufactured for specific uses. These manufactured chemicals are known as xenobiotics and include some fertilisers, pesticides, dyes, manufactured petroleum products, personal care products, and pharmaceuticals. What is common to all natural and Synthetic chemicals is that they are potentially toxic and likely to have come from a small geographic area or a limited number of sources. The chemicals are then redistributed in the environment through natural and anthropogenic activities, where organisms can intentionally or unintentionally be exposed to them. Some exposed species, and indeed some individuals, will be more sensitive than others, which can lead to adverse effects at the population level. When sensitive species are keystone or foundation species for a particular ecosystem, or enough species are affected, this can alter the structure and function of the exposed communities, having flow-on effects at the ecosystem level (Figure 4).
This text, image and its associated caption are from “Assessing Organism and Community Responses” In: Reichelt-Brushett, A. (eds) “Marine Pollution – Monitoring, Management and Mitigation “ 2023, by Amanda Reichelt-Brushett, Pelli L. Howe, Anthony A. Chariton, Michael St. J. Warne, which is licensed under CC BY 4.0
Image Text Version: Figure 2
Figure 2. Summary of some of the primary sources of marine pollution
Summary of some of the primary sources of marine pollution is depicted as a wheel. The wheel is split into 4 segments:
Diffuse sources
These have no obvious discharge point, with some being ongoing, including: runoff (agricultural, urban, industrial), atmospheric deposition, erosion and leachate or groundwater seepage.
Disaster events
These are sudden and unintentional, including: natural (e.g. floods, earthquake, tsunami, cyclone and fire) and human (e.g. civil unrest).
Accidents
These are sudden and unintentional, including: shipping (e.g. grounding, ballast, spills), cargo spills, nuclear accidents, consequence of poor risk assessment and infrastructure fails (e.g. pipes, dams).
Point Sources
These have a controlled discharge, with some being ongoing including: littering, illegal dumping, industrial effluents, mine tailings (commercial and artisanal) and sewage outfall.
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Image Text Version: Figure 3
Figure 3 Marine contaminant distribution and storage in the environment
The diagram for marine contaminant distribution and storage in the environment depicts a cross-section of a segment of land descending into the ocean.
System input starts with riverine inputs (point and diffuse sources) entering ocean via the land segment, through and bypassing an ice cover segment. Through thaw-freeze cycles, the inputs are cycled into the ocean system, entering the biological phase.
The Biological phase (benthic and pelagic marine organisms; biomass storage), which transitions to depuration and decomposition, leading to the cycling dissolved phase or the particulate phase. From here, materials either:
- Proceed from dissolved phase to uptake and back to the biological phase, or
- Proceed from the particulate phase to sedimentation and downwelling and either: surface transport and eventual sediments burial.
Through sediment and porewater interactions (redox conditions, reactive surface area and surface charge), this could lead to remobilisation or resuspension (also via benthic fauna, primary producers, physical sourcing, seepage, upwelling) and re-entry of materials into the biological phase, sedimentation and downwelling or into other processes.
Another system input starts with advection via the atmosphere, leading to the atmospheric phase (vapour and particulates) which flow into the ocean via deposition and absorption and back to the atmosphere via volatilisation. Debris could also be classed as ‘floating debris’.
Throughout the system, inputs, debris, sediment etc. are all impacted and transported via seawater and currents.
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Activity: Test your Knowledge
Test your knowledge in the quiz below:
Images used in this image sequencing activity which explores the transport of chemicals to biological systems is based on figure 4. Images are from “Marine Pollution in Context” In: Reichelt-Brushett, A. (eds) “Marine Pollution – Monitoring, Management and Mitigation” 2023, by Amanda Reichelt-Brushett, which is licensed under CC BY 4.0.
Activity Text Version
Activity: Test your Knowledge
This exercise invites readers to answer questions to test their knowledge, based on the Marine Pollution information above. Questions and answers are listed below.
Question 1
Which of these are examples of point sources? Select those that apply from:
- Littering
- Natural events
- Cargo spills
- Illegal dumping
- Sewage outfall
Answers to question 1
- Littering
- Illegal dumping
- Sewage outfall
Question 2
Which of these are examples of Diffuse sources? Select those that apply from:
- Runnoff
- Atmospheric deposition
- Shipping (e.g grounding, ballast, spills)
- Human influence (e.g civil unrest)
- Erosion
Answers to question 2
- Runnoff
- Atmospheric deposition
- Erosion
Question 3
Which of these are examples of Disaster events? Select those that apply from:
- Nuclear accidents
- Industrial effluents
- Consequences of poor risk assessment
- Human influence (e.g civil unrest)
- Natural events
Answers to question 3
- Human influence (e.g civil unrest)
- Natural events
Question 4
Which of these are examples of Accidental sources? Select those that apply from:
- Infrastructure failure
- Illegal dumping
- Nuclear accidents
- Leachate/groundwater seepage
- Shipping (e.g grounding, ballast, spills)
Answers to question 4
- Infrastructure failure
- Nuclear accidents
- Shipping (e.g grounding, ballast, spills)
End Activity Text Version
Activity: Transport of chemicals to biological systems
Try out the image ordering activity below to learn more:
Image used in activity is from “Marine Pollution in Context” In: Reichelt-Brushett, A. (eds) “Marine Pollution – Monitoring, Management and Mitigation” 2023, by Amanda Reichelt-Brushett, which is licensed under CC BY 4.0.
Activity Text Version
Activity: Transport of chemicals to biological systems
An image sequencing activity which explores the transport of chemicals to biological systems based on Figure 4. Answers in order are listed below.
- Source
- Distribution processes
- Abiotic environment
- Exposure to biota
- Organism response
- Ecological response
End Activity Text Version
References
Balatsky, A. V., Balatsky, G. I., & Borysov, S. S. (2015). Resource demand growth and sustainability due to increased world consumption. Sustainability, 7(3), 3430-3440. https://doi.org/10.3390/su7033430
Ducrotoy, J. P., & Elliott, M. (2008). The science and management of the North Sea and the Baltic Sea: Natural history, present threats and future challenges. Marine pollution bulletin, 57(1-5), 8-21. https://doi.org/10.1016/j.marpolbul.2008.04.030
Garrick, B. J. (2008). Quantifying and controlling catastrophic risks. Academic Press.
Makam, A. N., Puneeth, M. K., & Jayarekha, P. (2018, August). E-waste management methods in Bangalore. In 2018 Second International Conference on Green Computing and Internet of Things (ICGCIoT) (pp. 6-11). IEEE. https://doi.org/10.1109/ICGCIoT.2018.8752976
Reichelt-Brushett, A. (2023). Marine Pollution in Context. In: Reichelt-Brushett, A. (eds) Marine Pollution – Monitoring, Management and Mitigation . Springer Textbooks in Earth Sciences, Geography and Environment. Springer, Cham. https://doi.org/10.1007/978-3-031-10127-4_1
Reichelt-Brushett, A., Clark, M., & Birch, G. (2017). Physical and chemical factors to consider when studying historical contamination and pollution in estuaries. In Applications of paleoenvironmental techniques in estuarine studies (pp. 239-276). Dordrecht: Springer Netherlands.
