What happens when algae create red, black, or oily streaks in water?

The presence of red, black, or oily streaks in water typically indicates an algal bloom. Algal blooms occur when there is a rapid increase in the population of algae, often due to nutrient overload from sources such as fertilizers or wastewater. These blooms can lead to visible color changes in the water, including the formation of streaks, and can sometimes produce toxins harmful to aquatic life and even humans.

Understanding this phenomenon is important because blooms can have significant ecological impacts, including the depletion of oxygen levels in the water, which can lead to dead zones where aquatic life cannot survive. Thus, the observation of these colored streaks serves as a critical signal for environmental monitoring and management of aquatic ecosystems.