On-site sampling and monitoring in Hong Kong waters
Harmful algal blooms (HABs) have been regarded as a global environmental challenge. They refer to rapid growths of algae in water that can produce toxins harmful to marine life, animals, and humans. Karenia mikimotoi (KM) is one such toxic HAB species known for its potent fish-killing ability. Mainland China and Hong Kong have experienced severe impacts from KM blooms. For instance, in 2016, KM blooms resulted in the death of over 200 tons of fish in various local fish-farming zones in Tolo Harbour, Hong Kong.[1] Over the years, despite various methods have been employed to control HABs, these methods are either expensive or can lead to secondary pollution.
A sustainable and cheaper approach to control HABs involves employing algicidal bacteria that can kill algae. These bacteria originate from nature and can be massively and easily cultivated. However, the algicidal mechanism of such bacteria remains poorly understood, and algicidal bacteria isolated from Hong Kong waters have yet to be reported. Therefore, understanding the algicidal mechanism of these bacteria is crucial as it affects the success of using algicidal bacteria to control HABs.
A research team led by Prof. Fred Lee, Associate Dean and Professor in the School of Science and Technology at Hong Kong Metropolitan University, conducted a study on the algicidal mechanism of an algicidal bacterium Maribacter dokdonensis (P4) isolated from Tolo Harbour, on KM. The study seeks to determine the algicidal effects of P4 under various factors (such as how much bacteria is present, the growth stage of the algae and bacteria, and the presence or absence of algal-associated bacteria) as well as figure out the interactions between P4 and KM using proteomics (the study of proteins), in order to provide insights into how P4 can be utilised effectively to combat KM and other HABs. The research is supported by Research Grants Council's Faculty Development Scheme.[2]
Karenia mikimotoi cells lysed by algicidal bacteria P4
The findings showed that P4 was very effective at killing KM. The strongest effect of P4 was observed when it was present at a concentration of 25% bacterial culture dose after 24 hours. When both P4 and KM were in the stationary phase (where the population remains relatively stable), the algicidal efficacy of P4 was higher. Additionally, P4's ability to kill KM was stronger when the algae were in the presence of other bacteria compared to when they were alone. The findings suggest that the interactions between P4 and the algal-associated bacteria of KM could enhance P4's capacity to eliminate the algal cells of KM. Apart from its impact on KM, the research team also found that P4 demonstrated a strong algicidal effect on other dinoflagellate species (aquatic organisms that may form HABs), indicating its versatility and potential to be used as a universal algicidal bacterium for removing algal blooms.
Regarding the interactions between P4 and KM, the research team found that the essential metabolic processes of KM were disrupted after 8 hours of co-culture with P4, ultimately leading to the death of KM. Additionally, after 24 hours of co-culture with KM, they observed an increase in the iron complex outer-membrane receptor protein – a type of protein in P4 responsible for transporting iron. These results suggest that P4 might secrete potential algicidal substances capable of killing KM.
This research offers insights into the algicidal effect of P4 on KM under different conditions and explores the interactions between algicidal bacteria and algae. It provides valuable scientific information on the potential application of algicidal bacteria for controlling HABs in Hong Kong and mainland China, and potentially other regions.
For more details, please refer to the following publications generated from the research project:
'Revealing the algicidal characteristics of Maribacter dokdonensis: An investigation into bacterial strain P4 isolated from Karenia mikimotoi bloom water', Journal of Phycology.
'Proteomic insights of interaction between ichthyotoxic dinoflagellate Karenia mikimotoi and algicidal bacteria Maribacter dokdonensis', Marine Pollution Bulletin.
[1] Kwok, S. N. C., Wan, W. W., Chan, K. K., Xu, J. L. S., Lee, W. F. F., & Ho, K. C. (2016). “Karenia mikimotoi, a rare species in Hong Kong waters, associated with a recent massive fish kill”, Harmful Algal News, 53, 4–5.
[2] Reference no.: UGC/FDS16/M06/20
