Light pollution alters the skeletal morphology of coral juveniles and impairs their light capture capacity

Urbanization and infrastructure development have changed the night-time light regime of many coastal marine habitats. Consequently, Artificial Light at Night (ALAN) is becoming a global ecological concern, particularly in nearshore coral reef ecosystems. However, the effects of ALAN on coral architecture and their optical properties are unexplored. Here, we conducted a long-term ex situ experiment (30 months from settlement) on juvenile Stylophora pistillata corals grown under ALAN conditions using light-emitting diodes (LEDs) and fluorescent lamps, mimicking light-polluted habitats. We found that corals exposed to ALAN exhibited altered skeletal morphology that subsequently resulted in reduced light capture capacity, while also gaining better structural and optical modifications to increased light levels than their ambient-light counterparts. Additionally, light-polluted corals developed a more porous skeleton compared to the control corals. We suggest that ALAN induces light stress in corals, leading to a decrease in the solar energy available for photosynthesis during daytime illumination.

Automated summary

Urbanization and infrastructure development have caused changes in the night-time light regime of coastal marine habitats, and Artificial Light at Night (ALAN) is now a global ecological concern for nearshore coral reef ecosystems. In this study, we conducted a long-term ex situ experiment to investigate the effects of ALAN on the morphology and optical properties of juvenile Stylophora pistillata corals. Corals exposed to ALAN showed altered skeletal morphology and reduced light capture capacity, but also exhibited better structural and optical modifications in response to increased light levels. Additionally, light-polluted corals developed a more porous skeleton compared to control corals. We suggest that ALAN induces light stress in corals, leading to decreased solar energy available for photosynthesis during the day.