Which of the following situations results from an algal bloom in an ecosystem? A. increased biodiversity B. increased health issues for people, such as allergic reactions C. decreased water temperatures D. decreased phosphorus in the water supply

Whenever there’s an algal bloom in an ecosystem, there’s also an increased health issues for people, such as allergic reactions (option B). Algae-causing blooms are potential sources of toxins that make people sick or are considered fatal for animals. It is even considered a toxicant for the community's water supply.