Why should we be concerned about Nutrient Pollution?
by Yasim Edoo, Associate Professional
Institute of Marine Affairs
Many countries around the world are susceptible to different types of pollution. The countries of the Wider Caribbean Region (WCR) are no exception. In recent times, the issue of nutrient pollution has come to the attention of many islands in the WCR and the question of “How can this form of pollution be mitigated?” arises but what is nutrient pollution? Very simply put, nutrient pollution is the process whereby excess nitrogen and phosphorous compounds (nutrients) enter into water bodies and cause an excessive growth of algae leading to poor condition such as oxygen depletion (National Ocean Service). These nutrients act as fertiliser, which stimulate algal growth.
The United Nations Sustainable Development Goal (SDG) 14 states: ‘By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution’. In order to achieve SDG 14 (life below water), Caribbean nations need to develop a strategy to reduce the amount of nutrients that enter the marine environment from land-based sources. An excess of nutrients in waterways can lead to a phenomenon termed eutrophication.
What is Eutrophication?
According to the United Nations Environment Programme, eutrophication is a process in which there is a gradual enrichment of a waterbody by nutrients especially compounds of nitrogen, phosphorous and minerals which lead to:
- increased growth, primary production and biomass of algae;
- changes in the balance of nutrients, which in turn causes changes to the balance of organisms, for example, coral reef can be smothered by macroalgae which results in loss of biodiversity; and
- degradation of water quality, which results in oxygen depletion that causes fish kills.
Why should we be concerned?
If nutrient levels in waterways go unchecked, there can be adverse effects on both humans and the environment. It is known that high levels of nitrates in drinking water can cause a condition in infants termed ‘blue baby syndrome’, where there is a decrease in haemoglobin in the blood (World Health Organisation). Additionally, there is also an economic cost associated with high levels of nutrients as marine ecosystems are negatively impacted. The following are the effects of nutrient pollution on the marine ecosystem:
- Harmful algal blooms (HABs) – these are an overgrowth of harmful algae in waterways. The effects include mass mortality of marine fauna and a reduction in the quality of recreational and shellfish harvesting areas, which leads to an economic loss. Human health can be at risk if humans consume contaminated seafood exposed to HABs. Human poisonings associated with HABs include paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning and neurotoxic shellfish poisoning. Neurological effects and respiratory problems are among the health problems associated with direct exposure to the toxic algae. The first State of the Cartagena Convention Area Report (SOCAR) indicated that during 1970 and 2007, approximately 7,800 human intoxications, including 119 human fatalities, were mainly associated with paralytic shellfish poisoning which were linked to HABs in the Pacific and Atlantic coasts.
- Low oxygen (hypoxic) and dead zones – high nutrient levels in water can cause hypoxia, which results in low or no oxygen levels in the water. Dead zones are created when algae die and consume the water’s oxygen in the process of decomposition. When dead zones occur, it fails to sustain marine life resulting in the reduction or elimination of organisms.
- Marine habitats degradation – loss of nursery sites such as coral reefs and seagrass beds can lead to reduced fish population. Coral death and a decrease in hard coral cover in the Caribbean is due to high nutrient levels, primarily from improper treated sewage. Closer to home, nutrient enrichment has been identified as a cause of degradation on Buccoo Reef, where there has been a decline in hard coral cover and increase in macroalgal cover.
On the economic side nutrient pollution can affect:
- The cost associated with the treatment of drinking water – high levels of nitrates in drinking water can cause water treatment to be very costly. In the state of Minnesota, nitrate-removal systems resulted in an increase in water supply costs from 5-10 cents per 1000 gallons to over US$4 per 1000 gallons (United States Environmental Protection Agency).
- Tourism – the United States reports that tourism losses were estimated at US$1 billion annually due to nutrient pollution as recreational activities such as fishing and boating were affected (United States Environmental Protection Agency).
- The fishing industry (commercial) – harmful algal blooms can cause fish kills, which then lead to a decline in the fishing industry. The economical loss to the fishing industry due to nutrient pollution is estimated to be tens of millions of dollars annually (United States Environmental Protection Agency).
- Real estate – the value of property on waterfronts and coastal areas can decrease due to the poor aesthetics from water degradation. Nutrient enrichment causes algal blooms eg. Sargassum seaweed, which when rotting causes a pungent odour (hydrogen sulphide) similar to the smell of rotten eggs.
How can we mitigate this problem?
For a solution to be found, one must first find the source of a problem. In the case of nutrient pollution, the following are the major sources: agricultural surface runoff, natural surface runoff and wastewater, which includes both grey water and sewage. According to the first State of the Cartagena Convention Area Report (SOCAR), which is an assessment on land-based pollution of countries of the Caribbean region, agricultural surface runoff accounts for 55.7% of major sources of phosphorous and 19.8% of major sources of nitrogen in the WCR.
The Institute of Marine Affairs has been given the task to lead the development of a regional nutrient reduction strategy for the WCR. When this is completed, governments of the WCR can benefit from this strategy and take the necessary actions to alleviate nutrient pollution to achieve SDG 14.
We as citizens should also do our part to help reduce nutrient levels in the natural environment. Some ways in which you can play an integral role in nutrient reduction are; use phosphate-free detergents, use fertilisers in small quantities and only when necessary, avoid discharging sewage directly into waterways, and instead have a sewage treatment set up.
The ocean provides many benefits to us and we should do our part to take care of it. For some, the ocean generates income, and for most, a source of recreation. If pollution continues unabated, there will be job losses for those who rely on the ocean for sustenance, unsafe bathing waters and scarcity of fish/other seafoods for consumption. Let us be cognizant of our daily activities from here on, realising how it can impact our marine environment and if possible, alter the way we conduct our business.
“With every drop of water you drink, every breath you take, you’re connected to the sea.” – Sylvia Earle – Marine Biologist.