Journal Article

Comparative immune responses of corals to stressors associated with offshore reef-based tourist platforms

Lamb, Joleah B, Bourne, David G, van Oppen, Madeleine J H, van de Water, Jeroen A J M, Willis, Bette L

2015

Overview

We investigated the effect of stressors associated with offshore reef-based tourist platforms on the coral immune system. Our findings suggest that stressors associated with platform-related activities, in synergy with seasonal factors, compromise the coral immune system, contributing to the higher coral disease prevalence observed at these locations.AbstractUnravelling the contributions of local anthropogenic and seasonal environmental factors in suppressing the coral immune system is important for prioritizing management actions at reefs exposed to high levels of human activities. Here, we monitor health of the model coral Acropora millepora adjacent to a high-use and an unused reef-based tourist platform, plus a nearby control site without a platform, over 7 months spanning a typical austral summer. Comparisons of temporal patterns in a range of biochemical and genetic immune parameters (Toll-like receptor signalling pathway, lectin–complement system, prophenoloxidase-activating system and green fluorescent protein-like proteins) among healthy, injured and diseased corals revealed that corals exhibit a diverse array of immune responses to environmental and anthropogenic stressors. In healthy corals at the control site, expression of genes involved in the Toll-like receptor signalling pathway (MAPK p38, MEKK1, cFos and ATF4/5) and complement system (C3 and Bf) was modulated by seasonal environmental factors in summer months. Corals at reef platform sites experienced additional stressors over the summer, as evidenced by increased expression of various immune genes, including MAPK p38 and MEKK1. Despite increased expression of immune genes, signs of white syndromes were detected in 31% of study corals near tourist platforms in the warmest summer month. Evidence that colonies developing disease showed reduced expression of genes involved in the complement pathway prior to disease onset suggests that their immune systems may have been compromised. Responses to disease and physical damage primarily involved the melanization cascade and GFP-like proteins, and appeared to be sufficient for recovery when summer heat stress subsided. Overall, seasonal and anthropogenic factors may have interacted synergistically to overwhelm the immune systems of corals near reef platforms, leading to increased disease prevalence in summer at these sites.

• Publisher: Oxford University Press
• Subject: Anthropogenic factors / Complement / Complement component C3 / Complement system / Coral reefs / Coral reefs and islands / Corals / Environmental aspects / Environmental factors / Fluorescence / Genes / Green fluorescent protein / Heat stress / Heat tolerance / Human influences / Immune response / Immune system / MAP kinase / Melanization / Offshore platforms / Physiological aspects / Prophenoloxidase / Proteins / Signal transduction / Summer / Toll-like receptors / Tourism / Tourists