Table 1.
Effects of physicochemical shifts on the coral holobiont.
| Stressor Direction | Response (and representative references) |
|---|---|
| Organic carbon | • Growth of heterotrophic bacteria and increased abundance (Kline et al., 2006; Nelson et al., 2013) |
| ↑ | • Reduced dissolved oxygen (Simpson et al., 1992) |
| • Enrichment of virulent bacteria or virulence genes (Vega Thurber et al., 2009; Nelson et al., 2013) | |
| Nutrients (N, P or Fe) | • N/P/Fe: Increased algal growth and activity in benthos and plankton and DOM exudation (Bell et al., 2007; Kelly et al., 2012) |
| ↑ | • N/P/Fe: Enrichment of virulent bacteria or virulence genes (Vega Thurber et al., 2009; Kelly et al., 2012) |
| • N/P: Increased proportion of viral sequences (Vega Thurber et al., 2008) | |
| • N/P: Decreased larval production (Ward and Harrison, 2000; Koop et al., 2001; Loya et al., 2004) | |
| • P: increased rates of skeletal extension, contributing to decreased skeletal density (Koop et al., 2001) | |
| • P: increased rates of bioerosion by microborers (Koop et al., 2001; Carreiro-Silva et al., 2012) | |
| Dissolved oxygen | • Survival of dark-incubated Montipora peltiformis in anoxic water for up to 96 h (Mass et al., 2010). |
| ↓ | • Enhanced mortality of Montipora peltiformis in anoxic water with other stressors (low pH, elevated sulfide, contact with organic rich sediment)(Mass et al., 2010). |
| • Nighttime anoxia at tissue/water interface of healthy corals (Shashar et al., 1993), in the gastrovascular cavity (Agostini et al., 2012), and in coral tissue consumed by black band disease (Carlton and Richardson, 1995). | |
| Sedimentation | • Stimulated microbial activity from organic carbon and nutrients leading to reduced pH, elevated sulfide and coral tissue death (Mass et al., 2010) |
| ↑ | • Reduced mass transfer across coral surface (oxygen, nutrients, waste) (Rogers, 1990) |
| • Shading and decreased photosynthesis (Rogers, 1990) | |
| • Increased mucus production and sloughing, along with nitrogen uptake from sediment sources (Mills and Sebens, 2004) | |
| Light/UV | • Elevated rates of oxygenic photosynthesis (Shashar et al., 1993; Mass et al., 2010) |
| ↑ | • Incident light above photoacclimation thresholds, or associated with thermal stress, associated with formation of reactive oxygen and free radicals (Downs et al., 2002), photosystem and host tissue/DNA damage (Lesser and Farrell, 2004) |
| ↓ | • Low light: Reduced coral growth rates for species reliant on photosynthetic Symbiodinium for nutrition (Muscatine, 1973) |
| Temperature | • Symbiodinium loss (bleaching) (Glynn, 1991, 1993; Brown, 1997; Brandt and McManus, 2009) |
| ↑ | • Increased abundance and virulence of pathogens (Ben-Haim et al., 1999, 2003b; Banin et al., 2000; Cervino et al., 2004) |
| • Increased abundance of viral sequences (Vega Thurber et al., 2008, 2009; Littman et al., 2011) | |
| • Decreased larval recruitment to CCA (Webster et al., 2011) | |
| pH/pCO2 | • Experimental pH gradient (pH 7.3 and 8.2): increased % pathogens (Meron et al., 2011) |
| ↓ ↑ | • Natural pH/pCO2 gradient pH 7.3–8.1: no change in % pathogens (Meron et al., 2012) |
| • Natural pCO2 gradient: microbiota shift where proportions of Endozoicomonas spp. decrease while Halomonas spp. increase (Morrow et al., 2014). | |
| • Low pH: Induction of viruses (Vega Thurber et al., 2008) | |
| • Low pH: Decreased larval recruitment to CCA (Webster et al., 2013) |