10. Coral bleaching: expulsion of endosymbiotic dinoflagellates from coral, causing colony death or decreased growth and fecundity An increase in ocean temperature of 1-2°C could result in a loss of most current coral systems. Symbiodinium: type of dinoflagellate that’s a single celled alga classified as a protist. Coral-algae maintain mutualistic, endosymbiotic relationship. Dinoflagellates are the sites of photosynthesis, which fuels the energetic processes of coral. Combination of irradiance acting with elevated ambient temperatures compounds bleaching. Due to rising seawater temperatures, natural mechanisms are now contributing to coral bleaching through a positive feedback loop. Coral bleaching is highest in the tropics and increasing most rapidly there. Nutrient loading: the addition of chemical elements such as phosphorous or nitrogen to an ecosystem often from runoff. The change in concentration ratio can lower the amount of other necessary nutrients, namely phosphate, resulting in a phosphate deficiency in Symbiodinium. Corals can contain many types of Symbiodinium; this diversity is known as symbiotic plasticity. This plasticity: -expands coral’s realized niche space -allows coral to survive in warmer temperature environments -D1a symbionts (the stress-tolerant symbionts), C3 symbiont (stress-sensitive) Bleaching increased the diversity within Symbiodinium communities transforming from monocultures of only C3 symbionts to mixed communities including D1a symbionts. “…lag time between greenhouse gas emissions and the climate impact means that decisions made in the short term...will commit the planet to a minimum level of warming in the long term.” The Effects of Rising Ocean Temperatures on Coral Reefs