How can drought conditions affect nutrient cycling in lakes, and what management strategy helps minimize negative impacts?

How can drought conditions affect nutrient cycling in lakes, and what management strategy helps minimize negative impacts?

• A. Drought reduces nutrient concentrations by concentrating water
• B. Drought has no effect on algal dynamics
• C. Drought reduces water volume, concentrates nutrients, intensifies algal blooms, and can cause hypoxia upon rewetting
• D. Drought uniformly redistributes nutrients to the littoral zone

Answer: (C)

Drought lowers the water volume in a lake, so nutrients like nitrogen and phosphorus become more concentrated. That higher nutrient availability fuels algal blooms, especially when temperatures are warm and light is abundant. When rainfall returns and the lake rehydrates, the bloom biomass decomposes; microbial activity can consume a lot of the dissolved oxygen, creating hypoxic conditions, and the altered mixing can release even more nutrients from sediments, potentially triggering another bloom. A management strategy to minimize these impacts focuses on limiting external nutrient inputs to the lake—reducing agricultural runoff, wastewater, and urban fertilizers—so there’s less nutrient to fuel blooms during drought and after rewetting. Protecting and restoring wetlands and employing watershed practices that slow and retain nutrients also helps dampen the concentration effects and the risk of hypoxia.

Drought lowers the water volume in a lake, so nutrients like nitrogen and phosphorus become more concentrated. That higher nutrient availability fuels algal blooms, especially when temperatures are warm and light is abundant. When rainfall returns and the lake rehydrates, the bloom biomass decomposes; microbial activity can consume a lot of the dissolved oxygen, creating hypoxic conditions, and the altered mixing can release even more nutrients from sediments, potentially triggering another bloom.

A management strategy to minimize these impacts focuses on limiting external nutrient inputs to the lake—reducing agricultural runoff, wastewater, and urban fertilizers—so there’s less nutrient to fuel blooms during drought and after rewetting. Protecting and restoring wetlands and employing watershed practices that slow and retain nutrients also helps dampen the concentration effects and the risk of hypoxia.