<P> When phosphates are introduced into water systems, higher concentrations cause increased growth of algae and plants . Algae tend to grow very quickly under high nutrient availability, but each alga is short - lived, and the result is a high concentration of dead organic matter which starts to decay . The decay process consumes dissolved oxygen in the water, resulting in hypoxic conditions . Without sufficient dissolved oxygen in the water, animals and plants may die off in large numbers . Use of an Olszewski tube can help combat these problems with hypolimnetic withdrawal . </P> <P> Blooms may be observed in freshwater aquariums when fish are overfed and excess nutrients are not absorbed by plants . These are generally harmful for fish, and the situation can be corrected by changing the water in the tank and then reducing the amount of food given . </P> <P> A harmful algal bloom (HAB) is an algal bloom that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means . HABs are often associated with large - scale marine mortality events and have been associated with various types of shellfish poisonings . </P> <P> In studies at the population level bloom coverage has been significantly related to the risk of non-alcoholic liver disease death . </P>

Algal bloom causes and effects on oxygen levels