Unless you have been living under a rock, you would have come across the social media frenzy that surrounded the brilliant bioluminescence that occurred at Changi Beach Park over the past week. This sensation has taken Singapore by storm, attracting hundreds and even causing major traffic jams as many rushed to witness the bright blue waves in action, a phenomenon that occurred previously in 2016 (Zhang, 2022).
However, the glittering magic witnessed is not as harmless as we think…
Firstly, the glow is produced by a bloom of dinoflagellates that release bioluminescence. It was discovered that the bioluminescent dinoflagellate in question (Noctiluca scintillans) paired up with eukaryotes such as green algae (Pedimonomas noctiluca), expediting the dinoflagellate’s proliferation. Soh (2022) elucidates how since the Noctiluca scintillans species lack the ability to produce food on its own through photosynthesis, it typically ingests plankton cells to aid with photosynthesis. In this unique case, however, a symbiotic relationship was formed between the two where the green algae photosynthesise for the pair. While the existing bioluminescence is an indicator of pollution in Singapore’s waters and is not extremely harmful to human health, the continued proliferation of dinoflagellates (which are also bioluminescent), rising levels of nitrogen and phosphorus in the likely oxygen-low waters of Changi Beach Park may give rise to eutrophic conditions and outbreaks of HAB (Harmful Algal Blooms), posing significant implications for larger marine webs.
In studying how bioluminescence potentially gives rise to HAB persistence and initiation, Cusick and Widder (2020) highlight how when L.polyedra (a dinoflagellate species) lit up when it came in contact with copepods (a small crustacean that feeds on dinoflagellates), it was rejected and unharmed. Therefore, preferential feeding by predators on non-luminescent prey will inadvertently contribute to intensified bloom initiation as bioluminescent dinoflagellates can thrive without grazing pressures. Nonetheless, Cusick and Widder (2020) also caution how the flashes emitted by dinoflagellates as a deterrent are dependent on predators in the ecosystems.
What is especially noteworthy is that although dinoflagellates are both bioluminescent and toxin producers, these two factors are rarely studied together as deterrents against grazing predators. Just like bioluminescence, toxin production may expedite HAB growth as it removes grazing pressures on HAB. To provide deeper insight, Barreiro et al. (2006) as cited in Cusick and Widder (2020) indicate how studies on organisms from varying trophic levels (copepods, fish, macroinvertebrates, meso and microzooplankton etc.) However, the role of toxins as a grazing obstacle varies and have produced largely contradictory results that range from harmless effects to increased mortality risks of the grazer. Similar to bioluminescence, both the grazer and the toxin strain administered must be taken into careful consideration leading Cusick and Widder (2020) to conclude that more studies must be undertaken to analyse rates of bioluminescence and toxins in effectively contributing to HAB.
Well, I hope that this post has not put too much of a dampener on such a beautiful yet potentially harmful phenomenon. While we may be able to enjoy it from afar, we may also want to consider some interventions that will impede the growth of HAB which I will share more about in the next post. In the meantime, check out this video of the amazing yet potentially harmful phenomenon below!
References
Cusick, K. and Widder, E., 2020. Bioluminescence and toxicity as driving factors in harmful algal blooms: Ecological functions and genetic variability. Harmful Algae, 98, p.101850.
Zhang, J., 2022. Large crowds gather at Changi Beach on Saturday night to see blue bioluminescent waves. [online] Mothership.sg. Available at: <https://mothership.sg/2022/03/changi-beach-crowds-blue-bioluminescent-waves/>