Nutrition of Corals and Their Trophic Plasticity under Future Environmental Conditions

Abstract

Scleractinian corals obtain metabolic energy from their endosymbiotic autotrophic microalgae, and from remineralization of organic matter by bacteria and viruses, along with the heterotrophic food sources. The mutualistic symbiosis is generally stable but can be disrupted when environmental conditions surrounding the corals, such as increasing seawater temperature, become unfavorable to sustain each component of the holobiont. In this connection, the effects of global stressors such as climate change, and local stressors such as pollution, and their combination, are posing serious threats to the metabolic resistance of corals. However, some more resilient coral species have developed specific mechanisms to cope with fluctuating environmental conditions according to the trophic strategy (autotrophy, heterotrophy, or mixotrophy), and by modulating their energy expenditure. In this chapter, the role of nutrition in the coral symbiosis as the energetic budget for metabolic performance will be discussed, with a focus on the role of acquisition of nutrients through feeding, regulation of energy reserves (lipids, proteins, and carbohydrates), and adaptation capability in the natural environment, including the expression of heat-shock proteins (Hsps). Future environmental conditions under a combination of global changes and local impacts will also be discussed, with the aim of identifying the trophic niches of corals and geographical areas as possible refugia.