Algal blooms: What are they?
Algal blooms are also known as marine blooms or water blooms, and are actually a sudden increase in the population of algae in water scenery. Algal blooms usually take place in freshwater, such as lakes and water reservoirs as well as in marine milieus. They can be easily identified by coloration of the water ensuing from the high density of pigmented cells. Though many types of algae can form blooms, freshwater harmful algal blooms have the implication to produce toxins that are dangerous to other organisms including humans, pets, and livestock. This article focuses on the causes and related problems of harmful algal blooms.
What are Harmful Algal Blooms (HABs)?
An algal bloom, understood as a rapid rise of the algae, is considered as a perturbance in the water environments where it occurs, and may have austere organic effects on wildlife. Certain types of algal blooms are known to be composed of phytoplankters, from which the organically created biotoxins are often referred to as Harmful Algal Blooms i.e. HABs. Harmful Algal Blooms are known as red tides too; blue-green algae or cyanobacteria are a major environmental problem and have a severe impact on human health, aquatic ecosystems and the economy.
Algal blooms are usually natural portents, and their frequency, period and intensity are amplified by nutrient pollution. Some classes of algae develop in clusters covered in a jellylike coating and have the ability to float, permitting cells to stick together into bulky surface layers in calm weather. Other algae turn out as thick mats that float on or just underneath the surface along the coastline. Algal blooms also can be seen in colors such as green, yellowish-brown, or red.
What is causing HABs?
There are two major factors influencing the occurrence of HABs, and these are high temperatures and nutrients runoff. Harmful Algal Blooms are formed as a result of excess of nutrients, predominantly phosphorus and nitrogen, in the waters, and the increasing temperatures attributed to Global Warming is making the aquatic environments more prone to HAB’s events.
When the algae reach such high concentrations that it is considered to be a HAB, the effect in the water comes at the moment of the decomposition of this organism once they have finalized their life cycle, as the dead organic matter becomes a meal for the bacteria that decompose it. And with extra nutrients available, the bacteria rise in quantity and use up the dissolved oxygen in the water. Furthermore, as the available oxygen content declines, several fishes and aquatic organisms depending on the oxygen may not survive, and the outcome is a dead zone.
In conclusion – algal blooms occur due to an overabundance of the essential nutrients nitrogen and phosphorus, and though these elements are naturally available in nature, an excess of them causes significant disparities in the water body’s ecology, and blooms are one warning sign.
Problems caused by Cyanobacteria
Cyanobacteria can produce geosmins, which for drinking water is crucial, as it affects the organoleptic properties of the water potentially distributed, giving the water an ‘earthy’ taste. Once the geosmins liberated by the cyanobacteria are in the water, the treatment of such metabolites is challenging, as they are dissolved. The control by means of chemical methods has the implication of a THM formation, when the water also contains organic matter.
Moreover, cyanobacteria or blue-green algae can produce toxins that affect the water quality. Blue-green algae growth can cause a foul odor of the water, a layer of scum on the surface and even pose a health risk. People may be exposed to cyanobacterial toxins by drinking contaminated water. Therefore, an algae problem is often unwanted and algae control is desired.
Cyanobacteria and their pervasiveness in recreational and drinking water sources are a significant challenge for water utilities worldwide. The video provides information on the science behind cyanobacteria and cyanotoxins (source Water Research Foundation).
How to control Algal Blooms
The best way to reduce algal blooms is to provide measures in which reduction of those nutrients will minimize the manifestation and intensity of harmful algal blooms. Regulations applied by authorities against uncontrolled introduction of agricultural wastes are the most widespread preventive measure adopted, since blooms have shown a seasonal variation related to agricultural practices. Surveillance of nutrients in the water body during critical periods is extremely important for the success of such approaches. However, as these preventive measures do not necessarily work to solve the situation, treatment of HAB is still of significant importance.