Temperature affects coral disease resistance and pathogen growth

Abstract

Temperature anomalies on coral reefs now routinely exceed coral stress thresholds, making temperature a critical variable to consider in coral host -pathogen systems. While temperature is widely hypothesized to drive coral disease outbreaks by decreasing coral resistance and increasing pathogen growth rates, tests of the temperature hypothesis are rare. Here we report evidence from the sea fan coral Gorgonia ventalina -Aspergillus host -pathogen system that temperature stress increases one component of sea fan resistance. Experimentally infecting sea fan fragments while increasing temperatures to reflect summertime highs in the Florida Keys, USA, caused a 176% increase in activity of host-derived antifungal compounds. Thus, temperature stress and infection induce higher levels of resistance. However, pathogen growth rate also increases over the same temperature range, providing an opportunity for pathogen establishment before host resistance is maximal. This dual effect of temperature emphasizes the need to test intact host -pathogen systems. Given predictions for future warming events, aspergillosis is predicted to continue causing sea fan mortality in the Caribbean Sea.

Temperature induced disease in the starfish Astropecten jonstoni

“…Furthermore increasing water temperatures in reef environments allow pathogens to expand their ecological thermal disease in starfishniche, for example by colonizing low pH environments (Remily & Richardson, 2006). Although thermal stress can induce higher levels of resistance in the host, the growth rate of pathogenic bacteria can increase, and an infection become established before host resistance is maximal (Ward, 2007). In contrast to the numerous tropical reef studies of sessile species, relatively little information exists about thermal induced diseases and potential pathogens in temperate mobile invertebrate populations (Eckert, 2000;Farto et al, 2003;Becker et al, 2004).…”

“…Lawrence, 2004;Sabaté, 2006;Ward et al, 2007;Webster, 2007). A majority of these studies deal with mass mortalities observed in different coral species and other sessile invertebrates (Perez et al, 2000;Kushmaro et al, 2001;Boyett et al, 2007;Remily & Richardson, 2006;Ward et al, 2007).…”

Spatial and temporal patterns of scleractinian coral, soft coral, and zoanthid disease on a remote, near-pristine coral reef (Palmyra Atoll, central Pacific)

“…Environmental stress impairs coral host immunity and promotes pathogen virulence (Fitt et al 2001, Blanford et al 2003, Lafferty & Holt 2003, Ward et al 2007). As such, disease prevalence (predominantly tissue loss diseases) often increases during or proceeding coral bleaching events when temperatures are high and the coral hosts are compromised (Jones et al 2004b, Miller et al 2006, Whelan et al 2007, Brandt & McManus 2009, Bruckner & Hill 2009, Cróquer & Weil 2009).…”

The roles of endolithic fungi in bioerosion and disease in marine ecosystems. II. Potential facultatively parasitic anamorphic ascomycetes can cause disease in corals and molluscs

“…Nevertheless, fungi that are known to cause marine diseases can thrive in unusually high temperatures. One example of this is A. sydowii which causes asperillosis, a disease of G. ventalina (Ward et al 2007). This disease has become epidemic in sea fan populations in the Caribbean with the warming of ocean temperatures in mid-summer to over 30°C.…”