A little too much nutrients

In our previous blog post, we have discussed some of the detrimental consequences of heavy metal pollution in our water bodies. Today, we are going to talk about the ways in which our daily food consumption contributes to pollution.

Before the semester started, I was scrolling through Instagram and I saw a post advocating for veganism. Curious, I clicked on it and I was led to a Netflix documentary called “Cowspiracy: The Sustainability Secret (2014)”. This documentary alluded that animal agriculture is the primary driver of deforestation, greenhouse gases emission and pollution. It also caught my attention that agriculture be it animal or crops, are actually polluting our environment in ways that we do not realise.

                                 Cowspiracy: The Sustainability Secret (2014)

Agriculture Pollution

Farmers often dump a huge amount of fertilisers, herbicides, and pesticides into the soil for agriculture. When rain falls, water laden with Nitrogen (N) and Phosphorus (P) is washed away as surface runoff into nearby water bodies either as point source or non-point source pollution. Such anthropogenic input of nutrients into the aquatic ecosystem would usually cause the proliferation of harmful algae bloom.

Agricultural runoff

Source: Conley, D. et al. (2009)

What Exactly is Eutrophication?

Eutrophication is the over-enrichment of nutrients in the water body. Abundant N and P released into water bodies are the main causes of eutrophication. Deposits of N and P mostly originates from the usage of fertilizer on agricultural. This oversupply of nutrients will boost primary productivity and provide the optimal condition for the flourish of the algae bloom.

Impact

A classic example would be the toxic bloom of cyanobacteria in Lake Erie in 2014 which made local water supply toxic overnight. A more recent case in 2019, toxic algae bloom called the ‘red tide’ occurred in Florida and it killed 100 manatees, 127 dolphins, 589 sea turtles, and also hundred tonnes of fishes. Not only is harmful algae bloom deadly to marine life, but its production of toxins pose an equal threat to humans too. The city of Toledo released a statement warning the public of possible abnormal liver function, diarrhoea, vomiting, nausea, numbness or dizziness following the ingesting of contaminated water.

Lake Erie Algae Bloom

Source: The Guardian (2020)

 

This occurrence of eutrophication will adversely affect the aquatic ecosystem (Bennett, Carpenter & Caraco, 2001). With harmful algae bloom covering the surface of water bodies, sunlight is unable to penetrate through the water column resulting in oxygen depletion, essentially creating dead zones.

In this highly anaerobic condition, most aquatic life is unable to survive. Moreover, the decomposition of algal bloom will also lead to massive fish kills as a result of asphyxiation. Thus, affecting the aquatic ecological system adversely (Bennett, Carpenter, & Caraco, 2001).

Closer to home, in 2015 fish farmers in Singapore lost an approximate of 600 tonnes of fishes as a result of an algae bloom. Mass fish death was also observed along the Pasir Ris Beach. 🙁 Therefore, the pollution of our water bodies through anthropogenic activities can have a deadly impact on both aquatic organisms and the locals. Such mass killings of fish could also pose food security issues for countries that rely on fish as their main source of protein.

Before you jump into any water body, beware of any pungent-smelling or green, blue, red-looking scum on the surface. Algae blooms can be toxic and you certainly do not want to be inside.

 

Till next time,

Shee Wen & Nicole   

 

 

References

Animal United Movement Films & Media. (2014). Cowspiracy: The Sustainability Secret. Retrieved September 03, 2020, from https://www.cowspiracy.com/about

Bennett, E. M., Carpenter, S. R., & Caraco, N. F. (2001). Human Impact on Erodable Phosphorus and Eutrophication: A Global Perspective. BioScience, 51(3), 227. DOI:10.1641/0006-3568(2001)051[0227:hioepa]2.0.co;2

Conley, D. et al. (2009). Controlling Eutrophication: Nitrogen and Phosphorus. Science (New York, N.Y.). 323. 1014-5. 10.1126/science.1167755. Retrieved September 03, 2020, from https://www.researchgate.net/publication/24026915_ECOLOGY_Controlling_Eutrophication_Nitrogen_and_Phosphorus

The Guardian. (2020). Lethal algae blooms – an ecosystem out of balance. Retrieved September 03, 2020, from https://www.theguardian.com/environment/2020/jan/04/lethal-algae-blooms-an-ecosystem-out-of-balance

Today Online. (2015). Up to 600 tonnes of fish lost to algal bloom: AVA. Retrieved September 03, 2020, from https://www.todayonline.com/singapore/600-tonnes-fish-lost-algal-bloom-ava

Yousef, M & Sayed Ali Ahmed, Elmustafa. (2019). Internet of things in Smart Environment: Concept, Applications, Challenges, and Future Directions. Retrieved September 03, 2020, from https://www.researchgate.net/publication/335207701_Internet_of_things_in_Smart_Environment_Concept_Applications_Challenges_and_Future_Directions