Eutrophication in freshwaters: A Global Environmental Concern

Eutrophication in freshwaters is an alarming environmental phenomenon that poses significant risks to the world’s freshwater ecosystems. It occurs when excess nutrients, primarily phosphorus and nitrogen, accumulate in water bodies, triggering a series of detrimental effects on flora, fauna and overall quality of a system. In this article, we will discuss the causes, consequences and solutions to combat nutrient pollution, specifically phosphorus pollution in freshwater.

What is eutrophication in freshwaters?

Eutrophication is a natural process driven by nutrient enrichment in an ecosystem which usually takes hundreds of years to significantly change its ecological structure. However, since the 1950s this process has accelerated by nutrient pollution from human activity, climate warming and climate change patterns which include increased intensity and frequency of rain events which increases run-off from catchments that has increased nutrient emissions into freshwaters. As a result of anthropogenic activities nutrient delivery to freshwaters is happening much more quickly than it would naturally and it can cause the complete deterioration of a waterbody’s ecological structure which results in fatal loss of ecosystem function and biodiversity decline which can happen now in only a few years.

What are the three primary causes of eutrophication in freshwaters?

1. Agricultural Runoff: Excessive use of fertilizers in agriculture contributes significantly to excess nutrients entering freshwaters. During heavy rainfall events, these nutrients are washed into nearby rivers and lakes.
2. Sewage and Wastewater Discharge: Improperly treated or untreated sewage and wastewater adds excess nitrogen and phosphorus into freshwaters.
3. Industrial Activities: Industrial processes generate effluents containing pollutants and high nutrient concentrations that find their way into freshwaters if they are not treated.

What are the consequences of nutrient pollution?

1. Algal Blooms: Excess nutrients, along with warm temperatures, sunlight and low wind create ideal conditions for algal growth which can result in dense blooms. These blooms can reduce water clarity and the amount of sunlight that reaches deeper water layers which can hamper the photosynthesis of submerged plants.
2. Oxygen Depletion: When algae cells and aquatic plants begin to breakdown, they are decomposed by bacteria which consume oxygen. If there is a lot of organic matter to decompose, this leads to reduced oxygen concentrations, causing hypoxic or anoxic conditions, known as “dead zones.”
3. Loss of Biodiversity: The decline in oxygen levels and the dominance of certain species due to algal blooms can reduce the occurrence of other species groups or organisms, leading to a loss of biodiversity.
4. Fish: Reduced oxygen concentrations due to algal blooms or aquatic plant dominance can put pressure on fish populations, causing mass mortality events and disrupting the community composition.

How to combat Eutrophication in freshwaters?

Catchment Management: Implement measures that will aid the reduction of excess nutrients entering freshwaters. These can include but are not limited to nature-based solutions such as the creations of wetlands or riparian woodlands, vegetated drainage ditches and agri-environment schemes which include adding buffer strips along water courses and field margins. Good management practices are also important to prevent soil and nutrients entering freshwaters particularly during heavy and prolonged rainfall. Minimal tillage instead of ploughing, optimising fertilizer use by understanding soil chemistry and only applying nutrients that are lacking in the soil. Another solution is to capture phosphorus before it reaches our waterways and negatively impacts water quality. Phosflow is a filter media that removes phosphorus from flowing waters. It can be also used in wastewater effluents including municipal, industrial, and agricultural wastewaters.

In-lake nutrient management: There are a number of different in-lake management approaches available to improve water quality. The majority of these different measures are used to treat the symptoms of nutrient pollution and do not target the cause/s. Depending on geographic location, there are options to use algaecides to directly target algal blooms. Physical measures such as aeration or oxygenation to help improve oxygen concentrations in deeper waters or sediment dredging to remove legacy sediment. There are biological measures such as fish removal to help prevent sediment disturbance and phosphorus release or aquatic plant transplantation to aid restoration of desirable species. Chemical measures help to control phosphorus concentrations in waterbodies, which can include iron, aluminium salts, calcium carbonate or lanthanum-based clays. Phoslock is a lanthanum-modified bentonite; a geo-engineered product that significantly reduces phosphorus concentrations in the water column and controls phosphorus released from sediment complexes; improving the water quality.

Eutrophication is a grave environmental issue that demands immediate attention. It is important to understand the causes, consequences, and potential solutions to controlling nutrient pollution in freshwaters. It is fundamental to work towards mitigating nutrient pollution causes and preserving our precious aquatic ecosystems in a safe, efficient way.

For more information about how to apply Phoslock and Phosflow, contact PET.