Question

Eutrophieation causes reduction in (a) dissolved hydrogen (b) dissolved oxygen (c) dissolved salts (d) all the above

Short answer

Eutrophication causes a reduction in dissolved oxygen (b).

Step-by-step solution

Identify the Definition of Eutrophication

Eutrophication is the process by which an aquatic environment becomes enriched with nutrients (such as nitrogen and phosphorus), leading to excessive growth of algae and other plants.

Understand the Impact of Eutrophication

Excessive algal growth reduces the amount of sunlight that can penetrate the water, eventually leading to decay and decomposition of these algae by bacteria.

Analyze Chemical and Biological Changes

Decomposition of algae consumes oxygen, leading to a significant reduction in dissolved oxygen levels in the water. This low oxygen condition can harm aquatic life.

Review the Options

a) dissolved hydrogenb) dissolved oxygenc) dissolved saltsd) all the above. Eutrophication specifically causes a significant reduction in dissolved oxygen (b).

Key concepts

Dissolved Oxygen

Dissolved oxygen (DO) refers to the amount of oxygen that is present in water. It is essential for the survival of fish, invertebrates, and microorganisms. The level of DO in water is a critical indicator of water quality.
When eutrophication occurs, excessive nutrients in the water promote algal growth. As these algae die, they are broken down by bacteria in a process that consumes oxygen. This leads to a decrease in DO levels.
Low levels of dissolved oxygen can create hypoxic conditions, which are detrimental to aquatic life. Fish and other organisms may suffocate and die if DO levels drop too low. Therefore, maintaining healthy levels of dissolved oxygen is very important for aquatic ecosystems.

Algal Growth

Algal growth is a natural part of aquatic ecosystems. Algae are photosynthetic organisms that play a key role in the food chain. However, excessive algal growth can become problematic.
During eutrophication, nutrient enrichment from sources like agricultural runoff and sewage discharge causes a rapid increase in algae population. This phenomenon is commonly known as an algal bloom.
Algal blooms may initially seem beneficial because they increase primary productivity. But they can block sunlight, limiting the growth of aquatic plants in deeper waters. Eventually, the algae die and decompose.
Decomposition of a large biomass of algae results in the consumption of a significant amount of dissolved oxygen. This can lead to further environmental issues like dead zones, where the oxygen levels are too low to support most marine life.

Nutrient Enrichment

Nutrient enrichment, often referred to as nutrient loading, is the process by which water bodies receive excess nutrients. These nutrients, primarily nitrogen and phosphorus, come from various sources:

• Agricultural runoff, containing fertilizers
• Sewage and wastewater
• Industrial discharges

When these nutrients enter an aquatic ecosystem in large amounts, they stimulate the growth of algae and other aquatic plants. This process is a key driver of eutrophication.
While some nutrients are essential for the growth of aquatic plants and organisms, an overabundance can upset the balance of the ecosystem. Nutrient enrichment can lead to the overproduction of organic matter, which eventually decomposes and reduces the levels of dissolved oxygen in the water.
Managing nutrient inputs and preventing excessive nutrient loading are crucial steps in preventing eutrophication and its harmful effects on aquatic environments.