Impact of spectral variations on the gut microbiota of Tripneustes gratilla (collector urchin)

The population of Tripneustes gratilla (the collector urchin) has declined significantly due to overfishing, prompting researchers to explore aquaculture as a potential solution. However, the effects of different light conditions on the breeding of T. gratilla remain largely unexplored. This study investigated the impact of LED lighting on the bacterial composition of sea urchin culture water and its intestinal microbiota under various lighting conditions. The initial size of the sea urchins used in the experiment was about 11 mm. The experiment was divided into three groups: full-spectrum, red- and blue-light, with three replicates in each group. The experiment lasted seven weeks, with a 12:12 LD cycle daily. After seven weeks, the sea urchins in the blue-light group had a higher survival rate (93.3 %), and the bacterial content in the culture water varied significantly among groups. The bacterial concentration in the water of the red-light group was notably higher, and its biofilm formation capacity was increased. Next-generation sequencing revealed distinct bacterial community compositions across different light conditions, with the red-light group showing lower bacterial diversity but greater total species richness. Sequencing of bacterial strains from the red-light group identified Vibrio mediterranei and V. hangzhouensis , both of which displayed significantly higher colony formation rates under red light. In conclusion, these findings suggest that a long-wavelength environment may promote bacterial growth and influence the composition of the sea urchin's intestinal flora. However, short-wavelength environments may enhance the diversity of the flora. Juvenile sea urchin farming is conducted indoors with indirect lighting. This study suggests that specific wavelengths of light can be used to optimize aquaculture conditions and enhance the efficiency of cultivation. • Red light significantly increased bacterial levels and promoted biofilm formation. • Red light may lead to a more selective composition of bacterial flora. • Exposure to blue light resulted in a more diverse microbial ecosystem. • The colony formation rates of the genus Vibrio were notably higher under red light.