In a new study published in the Marine Drugs, researchers have revealed that the isolation of natural compounds from many aquatic and terrestrial plants and seaweeds has become an alternative approach for controlling harmful algae in aquatic systems.

Enhanced growth of aquatic vegetation or phytoplankton and algal blooms disrupts the normal functioning of aquatic ecosystems all over the world. When toxic microalgae and cyanobacteria are involved in these eutrophication consequences, a variety of ecological, economical, and sanitary health problems could arise.

Cyanobacteria are found globally due to their adaptation to various environments. The occurrence of cyanobacterial blooms is not a new phenomenon. The bloom-forming and toxin-producing species have been a persistent nuisance all over the world over the last decades.

Evidence suggests that this trend might be attributed to a complex interplay of direct and indirect anthropogenic influences. To control cyanobacterial blooms, various strategies, including physical, chemical, and biological methods have been proposed. Nevertheless, the use of those strategies is usually not effective.

Most of the recent studies on the control of the Harmful Algal Blooms (HABs) have focused on the use of chemical, physical, and biological treatment agents but these processes show serious environmental consequences. With respect to bioactive compounds extracted from seaweeds, most of them have been applied for their biocidal (anti-fungi, anti-bacterial) and pharmaceutical activities.

However, very few reports have focused on their algicide and anti-cyanobacterial activities. In order to explore macroalgae as an alternative and an available natural source of bioactive compounds, the researchers recommend that works could be oriented on the research of new natural products extracted from seaweeds.

Seaweed extracts show interesting potential against many harmful microalgae and cyanobacteria species but not much is yet known, namely the structure and mechanisms of action of the effective substances. These substances should be tested for their biocide activities against micro-algae growth in general and particularly against cyanobacteria growth.

The isolation of natural compounds from many aquatic and terrestrial plants and seaweeds has become an alternative approach for controlling harmful algae in aquatic systems. The undesirable effects of cyanobacteria proliferations and potential control methods are here reviewed, focusing on the use of potent bioactive compounds, isolated from seaweeds, against microalgae and cyanobacteria growth. Research on novel biomolecules is needed in order to better control the phytoplankton excessive growth in a sustainable way and to maintain the ecological equilibrium and the stability of the aquatic ecosystems.