Aquatic toxicity: classification, effects, measurement, and control

It is the study of manufactured chemicals and other manmade and natural materials and the behavior of aquatic species at different organizational levels, from individual organisms to populations and ecosystems toxicology:

Classification of aquatic toxicants 

Aquatic toxicants are categorized into seven major classes:

1. Organic toxicants (detergents, domesticated waste).
2. Pathogens (viruses, bacteria).
3. Fertilizers and nutrients.
4. Sediments and solids (minerals, sand, silt).
5. Inorganic toxicants (Cu, Hg, Cd).
6. Reservoirs of heat.
7. Radioactive toxicants (Cs137, Pu248).

Organic toxicants (detergents, domesticated waste)

Organic toxicants include:

O2 demanding waste

water waste like a domesticated waste, water waste from factories, tanneries, etc. is in large quantity consider as organic pollutants compounds. These wastes are decomposed and degraded by bacteria.  The amount of oxygen present in water is used by these bacteria. This leads to the low level of dissolved oxygen in the water which affects aquatic life.

Addition of synthetic compounds

The synthetic compounds are produced by many sources like spillage of oil, surface runoff pesticides, flush of medicines, glass and fibers, detergents, etc. When these compounds enter into aquatic ecosystem cause harmful effect on aquatic life many of these are toxic.

Spillage of oil

There are many sources of production of oil like plant fossils. The main components of the oil are hydrocarbons. The oil from spills, leakage through pipes and factories enter into water bodies. The density of oil is less than water so it does not dissolve in water and cause depletion of DO. It becomes dangerous for water birds and creates a hindrance for light transmission through water.

Pathogens

The major source of pathogens is sewage discharge from industries like slaughterhouses. These pathogens (bacteria, viruses, etc.) are the source of many water-borne diseases like fever, vomiting, hepatitis in living organisms.

Fertilizers and nutrients

Pesticides from agricultural land and fertilizer industries contain a large number of nutrients e.g. N2 and P. When this nutrient-rich water enters into the aquatic ecosystem and increases the rate of growth of algal blooms, as a result, decreases the DO concentration in water and cause eutrophication in water. The high concentration of nitrogen in water is dangerous, especially to infants.

Sediments and solids (minerals, sand, silt)

This includes the sediments (minerals, sand, silt) by soil. Those sediments enter into water during rainy season by surface runoff. This decreases the storage capacity of reservoirs. This causes the hindrance in the way of penetration of sunlight into water bodies it is necessary for aquatic plants for photosynthesis. The accumulation of these solids in oceans or streams affects the life and diversity of the aquatic ecosystem. These suspended solids injure the gills of fishes.

Inorganic toxicants (Hg, Cu, Cd)

High level of inorganic metals such as minerals, salts, metals (Cu, Cd, and Hg) sulfates or cyanides they are non-biodegradable and contaminate the water. They cause harmful effects on aquatic animals and plants. They also cause algal growth in water. A high level of these metals can be toxic.

The reservoir of heat

Release of heat and warm water from many plants like nuclear and thermal cause heat pollution. The release of this warm water into the aquatic ecosystem increases the water temperature which causes a decrease in dissolved oxygen level in the water and affects aquatic organisms.  High-temperature water increases the bacterial action as a result rapid decrease of DO.

Radioactive pollutants

Radioactive elements from mining, agriculture, medicine, and industries. The discharge from radioactive power plants such as Cesium, Plutonium, and Uranium are toxic to aquatic life. ^[1]Microsoft PowerPoint – Lecture 1-Intro to Aquatic Tox (csulb.edu)

Effects of aquatic toxicity on human health  

 Aquatic toxicity causes many human diseases and leading to severe illness especially in those countries which have no developed system to control water pollution like Africa. Some harmful effects of drinking polluted ware include:

Diarrhea

It is due to the disorder of the digestive tract which causes abdominal pain, vomiting, and loose stools. Its not life threatened disease but the condition can be severe. The people who drink contaminated water or food diarrhea is common.

Salmonella

 It is a bacterium that causes disease when we take polluted water or food. The signs which appear due to the infection of these bacteria include headache, fever, vomiting, abdominal cramp, and loss of appetite.

Cholera

 It is a waterborne disease and causes by bacteria About 95000 deaths each year caused by this disease. Sometimes it shows mild or no symptoms some symptoms include leg cramps, vomiting, and fever.

Dysentery

 It caused by the swelling of the intestine or bloody diarrhea. This can cause by parasites, bacteria, or a virus found in polluted water. It includes the symptoms of stomach pain, cramping, and diarrhea appear about 1 to 3.

 E.coli

 It is also a form of bacteria that enters into the intestines of the human. The ingestion of this bacteria can cause many symptoms like vomiting, diarrhea, and abdominal cramps.

 Hepatitis A

 It is due to the disorder in liver function causes by drinking contaminated water or food. The symptoms include stomach pain, fatigue, low appetite, jaundice, and vomiting, joint pain.

Hepatitis E

 This is also caused by the live infection and the hepatitis E virus. It is often spread by the consumption of polluted water especially in those areas which have not developed a sanitation system. It includes symptoms like fatigue, fever, jaundice, nausea, and vomiting.

Parasitic infection

 It is due to the presence of parasites in polluted water which are harmful it causes gastrointestinal like stomach problems and vomiting when ingested. It also causes scarcity of water, fever, loss of weight.

Typhoid Fever

This condition also caused by ingesting contaminated water and food. This include symptoms like weakness, high fever, headache, and loss of appetite death can also occur. ^[2]https://www.frontiersin.org/articles/10.3389/fenvs.2022.880246/pdf

Methods of measurement of aquatic toxicity   

Aquatic toxicity can be measured by aquatic toxicity tests these tests provide data about the adverse effects of toxicants on aquatic organisms. An aquatic toxicity test can be performed in fields or in laboratories. Following are the different types of tests that can use on various species.

 Exposure system

In the exposure system following techniques is used on test organisms

Static

In the static test, the organism is placed in still water, and a toxicant is added into the water in an order to obtain the correct concentration the test organisms are placed in the test solution, and water is not changed.

Recirculation

Similarly to the static test, a recirculation test was also attempted, but the solution passed through the chamber (filter) to maintain the water quality.

Renewal

This is just like the static, but the test solution is constantly altered in this, and the test organism move to the new solution. ^[3]https://www.epa.gov/sites/default/files/2015-08/documents/acute-freshwater-and-marine-wet-manual_2002.pdf

How to control aquatic toxicity

Wastewater treatment

 In this method, pollutants remove from wastewater by using different methods like physical, chemical, or biological methods.

Stormwater management

In this method, different techniques or efforts use to reduce runoff melted snow or rainwater, and other sites to improve the water quality.

Air pollution prevention

Air pollution has a harmful effect on the water the emission of CO2 absorbed by oceans causes the acidification of the ocean and affects marine life.

Plastic waste reduction

About 70% of plastic in oceans comes from the land we should control the use of plastic and its discharge into water bodies.

Use phosphate-free detergents

We can reduce the water pollution by using phosphate-free detergents because phosphate causes the algal bloom and decrease oxygen level in the water.

Dispose of medical waste properly

We should never flush medicine in the toilet or in the ponds. The harmful drugs accumulate in water and aquatic organisms these hormones cause many health problems in organisms. ^[4]https://www.epa.gov/sites/default/files/2015-09/documents/owm0330.pdf

Reviewed by:
Dr. Muhammad Khalid Mukhtar (Ph.D.)
University of Sargodha, Sargodha