A Harmful Algal Bloom (HAB) occurs when certain types of algae grow rapidly in water, often due to excess nutrients like nitrogen and phosphorus. These blooms can produce toxins that are harmful to marine life, humans, and the environment. They can occur in both freshwater and saltwater, affecting lakes, rivers, and coastal areas. HABs can lead to serious ecological and health issues. For example, when fish consume toxic algae, it can result in fish kills and contaminate seafood. Additionally, recreational activities like swimming and fishing may be restricted in affected areas to protect public health.