Benefits

Costs

Indirect Effects

Animal

Symbiont "solar energy panels" provide ready supply of translocated photosynthetically fixed carbon

Increased growth and reproductive rates

Increased calcification rate

Sequestration of toxic compounds by algae

Need to regulate algal growth, mechanisms for the acceptance and rejection of algal symbionts; produce specialized vacuoles

Need defense against oxygen toxicity, high light (UV and visible)

Vulnerable to environmental stresses (or diseases) affecting plants

Restricted to photic zone

Maximize surface area : volume ratio

Algae

Supply of carbon dioxide and nutrients from host

Protected from grazers

Maintenance in photic zone

Animal tissues provide protection from damaging UV radiation

Increased photosynthetic efficiency: uniform environmental conditions allow for high yields by dominant algal genotypes

High rent: must translocate significant fraction of photosynthetic gains to animal host

Nutrient supply is limited, resulting in slower growth rates in hospite, perhaps because carbon dioxide and nutrients are regulated by coral host.

Risk of eviction: may be expelled from coral host (especially high during bleaching events)

Dispersal by corallivorous fish and invertebrates

Reef coral symbioses

Increased growth rates: better competitors for space on the reef

Resource partitioning for food and space

High calcification provides high wave resistance

Compounded sensitivity to stresses that affect plants, animals or both

Restricted range of tolerance to light, temperature and sediment conditions