Impact of Supplemental Lighting on Corals in an Analog Ocean

Coral reefs are critical habitats for biodiversity and coastal erosion control. Due to climate change, we have lost half our reefs worldwide and will continue to lose more. The Biosphere 2 Ocean is an ideal testing ground for coral resilience because of its scale and control. However, there are pitfalls with Biosphere 2 replicating coral lighting needs; supplementing the lighting is a solution to mask these shortcomings. Corals respond differently under different lighting treatments, with less bleaching and calcification under treatments specialized to shorter wavelengths, and will bleach and calcify more under general wavelength treatments. Using three species of corals (Montastraea cavernosa, Orbicella faveolata, and Pseudodiploria clivosa) and the Mini-Ocean and Coral Raceway tanks at the Biosphere 2, we tested the tissue growth, calcification, and color change of coral fragments under different lighting treatments. The two lighting treatments were a general purple, blue, and red and a specialized purple, blue, and cyan. We found the corals in the Mini-Ocean lost blue and green at a significant rate during the treatments. Contextual data from our study found temperatures in the Mini-Ocean were over the preferred ranges of corals during the trials. Future studies on the topic at Biosphere 2 should standardize temperature and other water parameters in the ocean if it isn't a variable under study.