Detection of Chronic Stress in Corals Exposed to Invasive Algae Mats

Invasive algae mats like those common in Kāne‘ohe Bay, O‘ahu, are known to negatively affect coral health and recruitment through a variety of mechanisms including shading, abrasion, oxidative stress, and allelopathic interactions. Algae-induced stress has thus far been documented through changes in photosynthetic efficiency and coloration (bleaching) of the coral, and these studies have been largely accomplished through experimental manipulation, inflicting acute stress on coral nubbins. Few studies have investigated the stress response of corals chronically exposed to algae-induced stress, and fewer have used molecular methods to demonstrate and quantify this stress. This study focuses on Porites compressa colonies in chronic contact with the invasive alga Kappaphycus alvarezii on naturally occurring patch reefs in Kāne‘ohe Bay, O‘ahu, Hawai‘i. Our findings demonstrate the ability of these methods to detect and monitor coral stress before outward signs of stress such as bleaching are evident, which will allow for more proactive management of at-risk coral reef ecosystems. The differential expression of genes and gene products (proteins) between corals in long-term contact with invasive algae and those not in contact with algae highlight the specific metabolic pathways involved in algae-induced stress response of corals and lays the foundation for understanding mechanisms of acclimation and resilience towards these stressors.