What’s causing mass fish death in India’s ponds and lakes?

What’s causing mass fish death in India’s ponds and lakes?

Subject: Environment

Section: Pollution

Context: Every year, several ponds and lakes across various Indian states become sites of mass fish deaths. The primary cause for this phenomenon is water pollution, most often stemming from anthropogenic activities

What has led to pollution of ponds and lakes in India?

India’s fast-paced development has resulted in around 70% of its surface water becoming unfit for consumption and severe water body contamination has caused mass deaths of aquatic life.

Sewage and garbage dumping majorly contribute to water pollution and low DO levels in India’s ponds and lakes.

Religious events also contribute to water pollution

Harmful substances such as chemicals or microorganisms contaminate a stream, river, lake, ocean, aquifer or any other body of water, degrading its quality and rendering it toxic to humans and the environment

Heavy metal poisoning is often a key factor for such fish kill events. Even if a small amount of heavy metals enter a waterbody, their effect on the ecosystem gets amplified due to processes such as biomagnification and bioaccumulation

How do we know if the water is polluted?

The five basic water quality parameters are dissolved oxygen, temperature, electrical conductivity or salinity, pH and turbidity

Dissolved oxygen:

It is the amount of oxygen dissolved in water – essential for the survival and growth of most aquatic organisms.

This is a key indicator of water quality and the potential of the water body to support aquatic life and ecosystems.

Temperature:

The temperature of the water affects water chemistry and functions of aquatic organisms, such as metabolic rates of organisms, timing of reproduction, migration etc

Conductivity:

It is the ability of the water to conduct electricity – an outcome of dissolved salts in the water that break into positively and negatively charged ions

Salinity:

It is a measure of the amount of salts in water; dissolved salts increase both salinity and conductivity

pH:

The pH is a measure of how acidic or alkaline the water is. Several chemical reactions that are necessary for aquatic organisms to survive and grow, require a very narrow pH range

Turbidity:

It is a measure of the amount of suspended particles in the water. Algae, suspended sediment, and organic matter particles all contribute to turbidity.

The presence of total coliform bacteria, faecal coliform bacteria and E. coli suggests that a water body has been contaminated by faecal matter (e.g.: through untreated sewage discharge)

They are also called ‘indicator bacteria’ because they are easier to test for compared to other pathogens and can therefore reveal the extent of contamination of a water body

What are possible solutions to the water pollutiion?

• Decentralised governance and localised initiatives are often the best ways to undertake the several lake and pond restoration projects as they can address the issues specific to the water body in concern.
• Data collection, especially using automated, geotagged, time-stamped real-time sensors to gather data on water quality in a non-stationary manner is one way to effectively identify the spread of water pollution locally.
• Regulations, policies and funding towards developing wastewater treatment infrastructure, improving solid-waste management and implementing stringent laws towards curbing industry pollution can lead to pivotal and widespread change in water quality
• Promoting greener agricultural practices that cut the use of the chemical inputs can effectively address one major source of water pollution
• Stakeholder involvement and innovation are crucial. Supporting frugal innovations and localised, participatory management of water bodies can scale up restoration efforts from the ground up

Concept:

Eutrophication:

Nitrogen is essential for plant growth in an aquatic ecosystem. However, when large amounts of nitrogen are introduced into an aquatic ecosystem (e.g.: due to fertiliser runoff), it can cause excessive algal growth.

In a process known as ‘eutrophication’, the algae use up the oxygen for photosynthesis, depleting the oxygen available to aquatic organisms. This reduces the dissolved oxygen in the water body and can suffocate and kill the organisms within.

Bioaccumulation

It is typically associated with the build-up of damaging or harmful chemicals in a living thing. These chemicals will not break down in the body or are not able to be excreted. This will cause the chemical to accumulate over time

Biomagnification

Plants that are exposed to and absorb chemicals in the water or soil will accumulate them when they can’t break them down. When an animal starts to eat these plants they are also consuming the chemicals. The more plants they eat the more chemical they consume. This is called biomagnifications

Biomagnification occurs as the chemical moves further up in the food chain. The amount of chemical magnifies or the amount increases at each level. This means that animals at the top of the food chain accumulate the highest levels of the chemical through biomagnification.