Corals in crisis: mechanisms to survive
climate change and emerging diseases
University of Texas at Arlington, USA
Tropical corals are under unprecedented
stress from climate change, including increasing sea surface temperatures and
acidity as well as an increase in infectious diseases. Recently, the effects of
these stressors on coral physiology have been highlighted, showing resilience
of some corals to temperature and pH stress and more physiological plasticity
than previously expected. Such studies have examined coral heterotrophy,
decalcification and symbiont exchange as mechanisms by which corals can
overcome changing ocean conditions. Another aspect of coral plasticity is in
the innate immune system. Corals can fight invading pathogens with a suite of
innate immune responses designed to arrest pathogen growth and prevent further
tissue damage. Several of these responses, such as the melanin cascade,
circulating amoebocytes and antioxidants are induced in coral hosts during
pathogen invasion or disease. Surprisingly, some of these responses were
elevated during temperature stress and even in bleached corals, suggesting that
some corals may be immunocompetent even during times of extreme physiological
stress. Even though these examples point to potential resilience to climate
change, there is considerable variability of these responses between coral
species, and the compounding effects of all these stressors are unknown. The
implications of all these physiological processes to current and predicted reef
health will be discussed.