There has been a recent observation about mass death of fishes in Dal lake, as dead fish were seen floating on the surface along Boulevard and Foreshore road. This raises a major concern about the safety and well-being of aquatic life within the lake.
An identical incident occurred last year at Fashkoori wetland of Pampore, with a possibility of similar unreported happenings elsewhere. As usual, the local grapevine is full of theories, but we cannot rule out the two-day rain spell or the increased motor-boat patrolling activity.
The Dal lake occurrence may be an early warning sign and needs serious introspection regarding its causes and mitigation.
The ability of a water body to support its aquatic life is generally ascertained through six parameters i.e. Dissolved Oxygen, Temperature, Conductivity, pH value, Turbidity, Nitrogen level.
The main parameter – Dissolved Oxygen level has a direct bearing on the aquatic life within a water body. Dissolved oxygen is the amount of free, non-compound oxygen molecules in water. Fish usually cannot survive at dissolved oxygen levels less than 4 mg/L and it is desirable to have levels exceeding 9mg/L to support proper flora and fauna.
Temperature and Conductivity impact Dissolved Oxygen levels and bear an inverse relationship with the same.
pH level is an indicator of the acidic nature of a solution, varying from 0 to 14. Extreme pH values are known to cause physical damage to gills, exoskeleton and fins of fish.
Turbidity is a measure of suspended particles. Increased turbidity prevents sunlight reaching the depths of a water body, thereby impacting organism growth and oxygen levels.
Excessive levels of Nitrogen lead to abnormal algal growth, depleting the available oxygen, as the algae die and decompose.
It is observed that a variety of factors - including the effects of excess nutrients and stratification of water due to saline or temperature gradients - can create hypoxic conditions, which would make the water body devoid of any life.
The other impacting aspects are fast-paced development, inflow of untreated effluents, chemicals and pesticides. Sewage and garbage dumping majorly contribute to water pollution and low oxygen levels.
Another facet to be considered is Heavy Metal poisoning, which is often a prime culprit for such fish kill incidents. Heavy metals get retained by aquatic plants, settle on the beds, get consumed by bottom feeding organisms, and magnify up the food chain to bigger fish. Further, the addition of pollutants drives organisms to consume more oxygen for their degradation, decreasing the available dissolved oxygen.
Given the conditions of Dal Lake, the population along its shoreline, vegetable farming and other commercial/ non-commercial activities, one cannot rule out the influx of untreated sewage, some levels of pesticide and Heavy metals making ingress into the lake.
The moot question is whether Dal Lake is gradually turning into a Eutrophic water body, which would not be able to support any aquatic life. The condition could be caused by excessive nutrients augmenting algae growth. Once the algae die, the bacteria present use up a lot of dissolved oxygen leaving the lake deprived of its main ingredient for supporting the flora and fauna.
To summarise, there are three main causes of mass fish deaths- Oxygen depletion, Algal bloom and Pesticide Toxicity. A proper solution has to mitigate all three factors. Besides looking for solutions, there is an immediate need for monitoring the health of the Lake by concerned administrative agencies. The exercise could be initiated with in-depth data collection of all parameters and their real-time monitoring using sensors or other IoT devices.
The Dal-lake fishkill is a wakeup call for us to initiate proactive action towards preservation of our water bodies.
DISCLAIMER: The views and opinions expressed in this article are the personal opinions of the author.
The facts, analysis, assumptions and perspective appearing in the article do not reflect the views of GK.