If pesticides can’t be used beneficially, then what could be done to prevent the problem? Already some measures have been taken to prevent the key nutrients that lead to harmful algal blooms from flooding into the oceans. Many states and municipalities ban the use of phosphates in detergents. While bans on phosphates in soap helps, it does not completely eliminate the problem. In addition, many people oppose the bans because detergents that don’t contain phosphates don’t clean as well as the detergents with phosphates. I even know several people in my own community who, dissatisfied with the quality of the locally sold detergents which are phosphate-free, go to a neighboring state that does not have the ban to get their detergents, making the ban somewhat ineffective. If bans on phosphates are to be successful, better detergents need to be developed that are of a similar—or even better—quality for cleaning.
At present, the addition of chemicals is used to treat areas that have already had blooms of toxic algae. Chlorination, ozonation, and the addition of activated carbon have all been used to treat water sources to eliminate toxins produced by algae. Unfortunately, both the addition of chlorine and ozone to water, while moderately effective in destroying toxins, prove also to be moderately effective in destroying fish and other aquatic life if the levels of either chemical is too high. Activated carbon has also been used to eliminate toxins in harmful algal blooms. Activated carbon is also used in filters for aquariums, and is much less likely to harm fish. Unfortunately, none of these methods are completely effective, and many toxins, such as microcystins produced by some species of cyanobactera, are left unaffected. In addition, they’re not as affective in combating the oxygen depletion that is caused by bacteria feeding on dead algae.
Because of the toxin release and oxygen depletion that results from algal death, it is far better to remove the algae from a harmful bloom before they die than to kill them. In order to remove algae, microfilters would be needed to sift through an area. At present, some technology exists to do this, but it is highly expensive. Further research needs to be done in the area of microfilters to find a way to implement them more cheaply. Like with most new forms of technology, the price would go down as more was discovered and the use of microfilters became more widespread. Another unfortunate pitfall is that, due to the necessary fineness of the filter for catching algae and cyanobacteria, the filtration process in an area would take copious amounts of time and larger species may be harmed. To help cut down on time, several filters could be used in an area at once. As for the potential problem for larger species, the filters would need to be built so that organisms that could propel themselves could back out of the filter if needed.
Ideally, the concentrations of nutrients like nitrates and phosphates that flow into the ocean from farms and other human-based causes need to decrease to prevent the growth of algal blooms in the first place. It is, however, unrealistic to expect farmers to quit using fertilizers on their crops, as it would significantly decrease their profits and the amount of food available to the public. Instead, biofilters containing bacteria that utilize the nitrates in the water could be used. These filters could be installed as components to already existing dams. For rivers which are undammed or receive runoff from farms downstream of any dams, filters could be placed in different sections of the river. The housing for the filters would not span across the entire river, so fish would still be able to swim up and down stream. Because water would still be able to move downstream without going through the biofilters—either through fish ladders or in the area around the housing for the biofilters that weren’t in dams—so there would still be a high enough concentration of nutrients that the oceanic regions at the mouths of rivers would still be able to sustain life.
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