Abstract
When the toxic red tide alga Gymnodinium catenatum H.W. Graham accumulates in sediment through sexual reproduction, it provides the provenance of a periodic outbreak of red tide, a potential threat to the marine environment. In our study, the flocculation effects of four coagulants were compared. Bacteria fermentation (Ba3) broth and coagulant were combined with Ba3 to reduce the vegetative cells of G. catenatum, inhibit the cystic germination in the sediment, and control the red tide outbreak. To promote a more efficient and environmentally friendly algae suppression method, we studied these four coagulants combined with algae suppression bacteria for their effect on G. catenatum. The results show that polyaluminum chloride (PAC) is more efficient than other coagulants when used alone because it had a more substantial inhibitory effect. Ba3 broth also had a beneficial removal effect on the vegetative cells of G. catenatum. The inhibition efficiency of 2-day fermentation liquid was higher than that of 1-day and 3-day fermentation liquids. When combined, the PAC and Ba3 broth produced a pronounced algae inhibition effect that effectively hindered the germination of algae cysts. We conclude that this combination provides a scientific reference for the prevention and control of marine red tide. Our results suggest that designing environmentally friendly methods for the management of harmful algae is quite feasible.
Highlights
At present, red tides have become one of the ocean’s most catastrophic global disasters.The occurrence frequency, outbreak intensity, and impact range of red tides worldwide have been increasing and causing various degrees of harm to many countries’ coastal regions
Our results show that the feasibility of using appropriate concentrations of polyaluminum chloride (PAC) combined with Ba3 fermented broth is potentially useful for controlling G. catenatum blooms
The effect of bacterial fermentation broth on killing algae is complete, but the time needed for effective action is longer
Summary
At present, red tides have become one of the ocean’s most catastrophic global disasters.The occurrence frequency, outbreak intensity, and impact range of red tides worldwide have been increasing and causing various degrees of harm to many countries’ coastal regions. It is conservatively estimated that the annual loss of fishery and tourism caused by harmful algae blooms (HABs) in Europe is up to EUR 862 million, while the annual loss caused by HAB in the United States is up to USD 82 million. 2004, an average of USD 1.31 million was lost annually in South Korea’s fisheries due to harmful algal blooms. Red tide refers to the rapid proliferation or accumulation of various dinoflagellates and diatoms under external environmental conditions, mainly in marine environments such as coastlines or estuaries [1].The algal cell density reaches a certain level, causing water discoloration and affecting coastal areas and aquatic ecosystems, which, in turn, cause severe effects and hinder tourism [2]. The dinoflagellate Gymnodinium catenatum is a dominant harmful algae bloom (HAB)-forming species along coasts worldwide [3,4]
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