The combined effects of climate change and pollutants is a major threat to marine life and seafood worldwide

Original title

Climate change impacts on pollutants mobilization and interactive effects of climate change and pollutants on toxicity and bioaccumulation of pollutants in estuarine and marine biota and linkage to seafood security

Illustrated version

Introduction

Both climate change and pollutants are a global problem and a major threat to social, economic, and environmental sectors. The combined effects of the two stressors (i.e., climate change and pollutants) can increase mortality and reduce growth and reproduction in aquatic life. It can also enhance the bio-accumulation of pollutants (accumulation of pollutants over time) in seafood organisms including seaweeds, prawns, shrimps, fish, mussels, and oysters. Seafood provides about 60% of animal protein supply in developing countries like Bangladesh, Maldives, and the Pacific Island countries. It is also a source of protein, vitamins (B6, B12), omega-3 fatty acids, income (employment), export (foreign exchange earnings), and support livelihoods of coastal people across the globe.   As a consequence of bio-accumulation, seafood contamination and seafood quality could be impacted worldwide.

Some of the most important climate change related stress factors are: 

1. Rise in temperatures (the earth’s surface temperature is projected to increase by 1.8°C to 4.0°C by the end of the 21st century, whereas in the Polar region, the temperature change could be much higher in the range of 2°C to 9°C)
2. Ocean acidification (decrease in pH) (there has already been a decrease of ocean pH of 0.1 units since the pre-industrial period and it is projected to decrease by 0.3–0.4 pH units by 2100 due to absorption of CO₂ by the ocean)
3. Low oxygen in the sea (hypoxia) (hypoxia is associated with excessive growth of algae as a result of increased inputs of nitrogen (N) and phosphorous (P) in waterways from agriculture, aquaculture and sewage outfall).  When algae die and sink to the bottom, they are decomposed by bacteria (using the available dissolved oxygen in waterbodies). This causes a very low or close-to-zero dissolved oxygen environment called “hypoxic environment”. The severity and prevalence of hypoxia are projected to rise due to rise in seawater temperatures (due to climate change).

Some of the high-risk pollutants are heavy metals, pesticides, nutrients, medicines, detergents, flame retardants, oil compounds and POPs: 

1. Heavy metals such as cadmium, cobalt, copper, lead, mercury, nickel, and zinc (these pollutants may enter into the environment as waste products from mining, agriculture farms (farms that usages inorganic fertilisers), and e-waste plants (plants which receive or recycle discarded electrical or electronic devices such as TVs, mobile phones, laptops, batteries, and toner cartridges)
2. Pesticides such as atrazine, chlorpyrifos, dimethoate, endosulfan, methyl-parathion (used to control pests and diseases in agriculture)
3. Medicines such as 17α-ethinylestradiol (EE2) (birth control pills) and Ibuprofen (medicine that reduces pain)
4.  Detergents such as nonyl-phenol (nonylphenol is used in laundry and dish detergents)
5. Flame retardants such as polybrominated diphenyl ethers) (PBDEs are used as flame retardants in a variety of consumer products such as plastics, textiles, carpets, polyurethane foams, television sets, electronic devices, computers and building materials)
6. Oil compounds such as BTEX (benzene, toluene, ethylbenzene, and xylenes) and Polycyclic aromatic hydrocarbons (PAHs) (oils are fossil fuels that occur naturally in coal, crude oil, and gasoline).
7. Persistent organic pollutants (POPs)  such as DDT, dieldrin  (organochlorine pesticides), and dioxins (comes from burning of municipal waste or forest/bush fires)

Findings

Evidence gathered by my colleagues and I reveal that the combined effects (synergetic or additive) of the two stressors impaired growth and reproduction, and enhanced bio-accumulation in aquatic life. In fact, the combined effects of climate change and pollutants would enhance the uptake and toxicity of pollutants to marine life and seafood organisms including the following:  

• Climate change would lead to pollutants easier moving into waterways due to the vaporisation of pollutants and increased inputs through the increase in the frequency and intensity of extreme weather conditions such as
  • cyclones/hurricanes
  • heavy rainfall/precipitation
  • floods
  • droughts
  • storms
  • bush fires/forest fires
  • melting/thawing of snows/ice.
• The toxicity of several high-risk pollutants would increase with increasing levels of climate change stressors.
• The combined effects of climate change and pollutants would impair the growth, and reproduction in marine life and suppress their immune functions and defence activities.
• The combined effects of climate change and pollutants would enhance the bio-accumulation of pollutants (such as cancer-causing heavy metals) in seafood organisms.

Conclusion

The combined effects of climate change and pollutants would exacerbate global pollution problems and would pose significant threats and risks to the following sectors:

1. aquatic ecosystems, marine plants, and seafood
2. people depending on seafood for animal protein supply
3. livelihoods of people associated with seafood
4. marine export business
5. human health.

To reduce and minimise the impacts of climate change and pollutants, implementation of several sustainable development goals will be required including the increased use of renewable energy, promotion of low-carbon economic development, and minimisation of high-risk pollutants’ presence in the environment.

Article info

Please refer to the original article for more technical details. Submitted by Dr. Golam Kibria (RMIT University Australia, Global Scientist of Artificial Mussel Pollution Watch Program, Australia). Article  ID: 2021.06.10. Reviewed by Dr. Jonas N. Søndergaard (editor at the Fair Journal).

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