Algae blooms, dense growths of algae in water bodies, are often linked to human activities. These dense growths can significantly alter aquatic environments. This article explores how excess nutrients, particularly from fertilizers, contribute to these environmental changes.
Understanding Algae Blooms
Algae are microscopic organisms naturally present in aquatic environments like lakes, rivers, and oceans. They use sunlight for energy through photosynthesis, similar to plants. An algae “bloom” is a rapid, excessive increase in their population, often discoloring the water green, blue-green, red, or brown. While some blooms are natural, human influences have increased their frequency and intensity. This overgrowth significantly impacts water quality and overall ecosystem health.
Fertilizer Nutrients and Algae Growth
Fertilizers promote algae growth by introducing excess nutrients, mainly nitrogen and phosphorus, into aquatic systems. These elements are essential for plant growth, but their natural availability often limits algae populations. When abundant nitrogen and phosphorus enter the water, they act as a rich food source, leading to rapid algae proliferation, a process known as eutrophication. In freshwater systems, phosphorus is frequently the limiting nutrient, meaning its increased availability triggers significant algal growth.
Pathways of Nutrient Pollution
Fertilizer nutrients primarily reach water bodies as runoff from land, with agricultural runoff from farms applying fertilizers to enhance crop yields being a major contributor. Often, more nutrients are applied than crops can absorb, leading to excess washing into surface or groundwater. Stormwater runoff from urban and suburban areas also carries nutrients from lawns, gardens, and golf courses; this runoff flows over hard surfaces, preventing natural filtration. Additionally, wastewater treatment plants can contribute residual nutrients to waterways, as even treated water may contain nitrogen and phosphorus.
Consequences of Algae Blooms
Excessive algae blooms negatively impact aquatic ecosystems and human interests. As dense algae populations die, their decomposition by bacteria consumes large amounts of dissolved oxygen, leading to hypoxia or anoxia. This oxygen depletion causes widespread fish kills and harms other aquatic life, creating “dead zones.” Thick algae mats also reduce water clarity, blocking sunlight from submerged plants important for the ecosystem. Some blooms, called harmful algal blooms (HABs), produce toxins dangerous to humans, pets, and wildlife upon contact or ingestion, affecting various bodily systems. Algae blooms also incur economic costs through impacts on fisheries, tourism, and drinking water treatment.
Reducing Nutrient Runoff
Mitigating nutrient pollution requires a combination of responsible practices. In agriculture, implementing nutrient management plans, conservation tillage, and cover cropping help farmers apply fertilizers efficiently, retain soil nutrients, and reduce erosion. Establishing vegetated buffer zones along waterways can filter sediment and nutrients. At the individual level, responsible lawn care, proper pet waste disposal, and directing downspouts into plant beds reduce urban runoff. Upgrading wastewater treatment facilities to remove more nitrogen and phosphorus is also a significant step in reducing nutrient discharge, and these collective actions help protect water quality.