Healthy lake transitioning into algae-covered lake due to phosphates.

Is Your Lake Turning Green? Unmasking the Phosphate Problem and How to Fix It

Author's portrait.
Reese Marlowe in Climate & Environment December 2025 • 4 min read.

"Discover how excessive phosphate levels are impacting lakes like Sipin Lake, and what innovative solutions can help restore their health."


Lakes are the lifeblood of communities, providing drinking water, supporting agriculture, and offering recreational opportunities. However, these precious ecosystems are increasingly threatened by a silent menace: phosphate pollution. Activities like intensive agriculture, urban runoff, and even seemingly harmless fish farming can overload lakes with phosphates, triggering a cascade of ecological problems.

One of the most visible consequences of phosphate enrichment is eutrophication—the overgrowth of algae and aquatic plants. This algal bloom might seem like a sign of life, it actually suffocates the lake, blocking sunlight, depleting oxygen, and ultimately killing fish and other aquatic organisms. Beyond the ecological damage, eutrophication can also impact human health, contaminate drinking water, and damage local economies dependent on recreation and tourism.

The study on Sipin Lake in Jambi, Indonesia, offers a stark reminder of the dangers of phosphate pollution. This lake, surrounded by a dense population and supporting significant fishery activities, has experienced increasing phosphate levels in recent years. But the story of Sipin Lake is not unique. Many lakes around the world are facing similar challenges, making it crucial to understand the sources, impacts, and potential solutions for phosphate enrichment.

What's Causing All This Phosphate? Understanding the Sources

Healthy lake transitioning into algae-covered lake due to phosphates.

Pinpointing the sources of phosphate pollution is the first step toward effective solutions. While natural weathering of rocks can release small amounts of phosphate into waterways, human activities are the primary culprits behind the surge in phosphate levels seen in many lakes.

Several factors contribute to phosphate overload:

  • Agricultural Runoff: Fertilizers used in agriculture are rich in phosphates. When rain washes over farm fields, it carries these phosphates into nearby lakes and rivers.
  • Urban Runoff: Cities contribute phosphate through sewage discharge, detergents, and stormwater runoff from roads and other paved surfaces.
  • Industrial Effluents: Some industries release phosphate-containing wastewater directly into waterways.
  • Fish Farming: Intensive aquaculture, like the floating fishery nets used in Sipin Lake, introduces significant amounts of phosphate through fish feed and waste products.
In the case of Sipin Lake, the study highlights the impact of floating fishery nets (keramba). As fish are fed and excrete waste within these nets, a concentrated source of phosphate is released directly into the lake. This finding underscores the need for sustainable aquaculture practices to minimize environmental impacts.

Turning the Tide: Solutions for Phosphate Enrichment

The good news is that phosphate pollution is a problem we can solve. By implementing a combination of strategies, communities can reduce phosphate inputs into lakes, restore water quality, and protect these vital ecosystems for future generations. For example, the Sipin Lake study explored different solution to lower the phosphate amount, these were the the application of double floating fishery net, Application of 'pelet' (food) additive on fish feeding and Reduction of phosphate from river streams. Each one of these methods are effective on its own but combined can improve results. We as individuals can help reduce the level by selecting phosphate-free detergents and being careful with fertilizer application.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What does it mean if a lake experiences phosphate enrichment, and why should I care?

Phosphate enrichment is when there's too much phosphate in a body of water, like a lake. This often leads to eutrophication, where algae and aquatic plants grow excessively. It's important because this overgrowth can block sunlight, use up oxygen, and harm or kill aquatic life. This process not only damages the ecosystem but can also negatively affect human health, drinking water quality, and local economies.

2

Where does all the phosphate in the water come from?

Human activities are the primary causes. Agricultural runoff, which includes fertilizers rich in phosphates, is a significant source. Urban runoff, including sewage discharge and stormwater, also contributes. Industrial effluents can release phosphate-containing wastewater directly into waterways. Additionally, fish farming, especially intensive aquaculture practices, introduces phosphates through fish feed and waste.

3

What is eutrophication, and why is it bad for lakes?

Eutrophication is the excessive growth of algae and aquatic plants due to high nutrient levels, particularly phosphates. It's significant because it disrupts the ecological balance of lakes. The dense algal blooms block sunlight, which is essential for underwater plant life. As the algae die and decompose, the process consumes oxygen, creating 'dead zones' where fish and other aquatic organisms cannot survive.

4

How can phosphate pollution in lakes be reduced or prevented?

Several strategies can be implemented to reduce phosphate levels. These include measures like applying double floating fishery nets, using 'pelet' (food) additives in fish feed, and reducing phosphate from river streams. Individuals can also help by choosing phosphate-free detergents and being careful with fertilizer application. Reducing these inputs can help restore water quality and protect ecosystems.

5

How do floating fishery nets contribute to phosphate issues in lakes?

The floating fishery nets, or 'keramba,' contribute to phosphate pollution because they concentrate fish waste and uneaten food directly into the lake. This concentrated source of phosphate release accelerates eutrophication. Managing or modifying these practices is important for reducing phosphate inputs and minimizing environmental impacts on bodies of water like Sipin Lake.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.