Recent research has revealed that red algae exhibit distinct colors not just for aesthetic reasons but as a means of inter-species communication. A study led by Kawai Hiroshi and his team, published in the European Journal of Phycology, highlights how certain species, particularly Asparagopsis taxiformis, utilize structural colors for both visual signaling and possible defensive mechanisms against herbivores. This pioneering research provides important new data on the ecology of deep-water red algae. Read the full article, here, or cite it using the DOI 10.1080/09670262.2025.2483980.
The research turned up something really fascinating. When red algae grow, they tend to grow white, however the growing tips of these algae can often be a striking blue. This special coloration is due to microspheres that reflect certain wavelengths of light. Together, these findings remind us that colors often serve as powerful communication and protective agents. As environmental conditions fluctuate, these roles are needed now more than ever.
The Role of Structural Color
Structural color in Asparagopsis taxiformis appears as red-orange to pink under white light due to these microspheres located at its growth tips. These microspheres scatter light in such a way as to create a vibrant, singular blue color. While this finding is exciting, it begs some pretty interesting questions as to how these colors work on the natural landscape of these algae.
As Kawai Hiroshi for the Japan Underwater Research Center writes, this was a fascinating introspection as a scientific diver. For one thing, as he pointed out, some red algae actually look quite white when viewed under water. In my first few minutes on a recent diversity survey, I got to witness one of the most incredible fisheries rehabilitation success stories. The young shoots in one of the species developed bright blue tips. These observations piqued my curiosity, and I set out to understand the mechanism behind these colors.
Our study demonstrates the ability of structural color to attract algae. It could act as a deterrent signal to would-be herbivores. Fortunately, Hiroshi was able to elaborate on this component. He noted that the inner material making it the colorful sea creature is very toxic and could scare off algae-feeding fish. This powerful repellent gets even better with a contrasting, warning color. As discussed above, specifically tailored features like the blue tint at the ends of algal blooms can improve its potency.
Protective Mechanisms Against Grazers
The research points to an additional purpose for these vibrant colorations, arguing that they might act as camouflage for the reproductive structures of some algae. The regions surrounding the fruiting structures are luminescent and appear bright white. This natural camouflage protects them from visual predators lurking in their clear-cut and chemically infused environment.
Hiroshi provided this image of the white structures surrounding the organism’s fruiting bodies, possibly to provide camouflage. This is an important adaptation since it helps hide their bright red coloration from visual grazers who search for their meals by spotting flashes of red. This two-fold utility of coloration offers an evolutionary benefit to these species.
As the climate warms and warm-water fish species rapidly follow the temperature gradient of the planet northward, these protective mechanisms are more important than ever. Hiroshi sounded alarm over the northward migration of warm-water fish. This would be a major risk for the algae in those regions, which do not have the protective pigmentation.
Challenges of Studying Deep-Water Algae
The study’s findings highlight not only the unique adaptations of red algae but the challenges researchers face when studying these organisms. Red algae usually grow underwater (under the littoral or tidal zone), so collecting and observing them is a challenge. Scuba diving is often what it takes for researchers to bring back physical samples that they can study and analyze.
Hiroshi noted the difficulties involved: “These species grow deep underwater below the tidal zone, which requires scuba diving for their observation and collection. Most of these deep-water species are just extremely delicate. This further complicates the ability to perform detailed observations and experiments on them, while they are still alive in the laboratory. Additionally, it uses advanced methods to allow viewing of the complex structures with an electron microscope.
This juxtaposition of challenge and discovery highlights the need for more exploration and research into deep-water ecosystems. Researching red algae provides important clues and a unique window into the vast world of marine biodiversity. These results help highlight the major ecological roles that these organisms serve.