Microscopic algae (phytoplankton) is an important part of the ecosystem because in the presence of sunlight, they produce oxygen through photosynthesis and release this oxygen into the water. However, its massive growth and the production of toxins can generate negative impacts.
These natural events known as Harmful Algal Blooms (HAB), can affect aquatic life, human health and local economies. Due to accumulated biomass, it has resulted in severely lower oxygen levels, creating “dead zones” in water bodies, which leads to high mortalities of fish. The toxins are transformed and transferred to humans by the consumption of contaminated fish, potentially leading to Ciguatera Fish Poisoning (CFP). Worldwide, algal toxins of all types may be responsible for as many as 60,000 intoxications.
Economic impact in the US
Today, it is estimated that HABs impact the US economy by $82 million per year. US Harmful Algal Bloom and Hypoxia Research and Control Act of 1998 stated that toxic algal blooms have been responsible for an estimated $1,000,000,000 in economic losses during the past decade. This is mainly due to its impact on human health, fishery, and high monitoring and management costs. Tourism and recreation increases this number, with a harmful algal bloom event in a single lake in Ohio costs of $37 to $47 million in lost tourism revenue over two years. In an assessment of US toxic algal blooms published in 2017, researchers concluded that the number of days of a cyanobacteria bloom would likely increase from an average of 7 days per year today to 16-23 by 2050 and 18-39 by 2090.
Algal blooms down under
Although Australia is already very close to achieving universal basic drinking water services, there are still occurrences when the tap water cannot be taken for granted. The citizens of Louth found toxic blue-green algal blooms in their water supply. Tap water turned into a brown, cloudy color with a distinct odor, unsafe for drinking and showering. Toxins from cyanobacteria can potentially cause illnesses, paralysis in humans, and some are even suspected to be involved in the occurrence of liver cancer. In January this year, blue-green algae bloom in the Darling River at Menindee led to the death of more than a million fish. In response, Berejiklian government installed nine water aerators to boost oxygen levels in different water bodies across Australia. These proved ineffective due to its lack of effect on algae and not enough systems, as one aerator can cover only an area about the size of a basketball court. Up to today, the most common method of algal bloom treatment is harmful chemicals. Those, however, are harmful to the environment and often produce unwanted side effects. Furthermore, herbicide and algaecide treatments often require expensive permits from the local government for environmental protection. When using aquatic herbicides, the lake or reservoir must be closed for several days.
Alternative algal bloom treatment is the ultrasound technology developed by LG Sonic. It is not based on cavitation nor does it break or lyse the cells, as such, toxins are not released into the water. Due to the adaptability of algae during seasons within a water reservoir, the ability to change these ultrasonic frequencies is of importance for the long-term effects of the technology. With the use of ultrasound technology, combined with monitoring and adjustment of ultrasonic frequencies, the blooms can be reduced by 70-90% in concentration, compared to no treatment.