Anemone Dysbiosis

Jakob Kaare-Rasmussen, Elise Cypher
Ecology, Evolution, & Marine Biology
The Moeller Lab


Cnidaria, marine invertebrates that include reef-building stony corals, often rely on photosynthetic endosymbionts that live within the outer tissue of the Cnidaria to obtain the energy they need for growth. Increased temperatures and/or nutrient pollution can disrupt mutualistic properties of the symbiosis, leading to host mortality such as coral bleaching. However, the precise mechanism by which this dysbiosis occurs is still unclear. Sea anemones, other cnidarians that host algal endosymbionts, are used as a model organism for the coral holobiont to understand the costs and benefits of symbionts, but the exact nature of the costs of symbionts on the hosts is still unclear.


Here we developed a Dynamic Energy Budget (DEB) model and fit the model to data from the anemone Exaiptasia pallida and its endosymbiotic algae, Breviolum minutum, in order to identify the most likely mechanism of symbiont costs. The model diagram visually represents the mathematical equations of the anemone biomass (H), symbiont biomass (S) and the fluxes of nitrogen and carbon between the two organisms. In order to accurately represent the system, our model required a novel explicit symbiont demand term, in which the symbiont can ‘‘consume’’ host tissue to forcibly extract nitrogen. The model demonstrates the role of the symbiont as an amplifier of the host’s state: a growing anemone grows better with symbionts, while a malnourished anemone loses biomass faster with a symbiont than without. This model allows us to project Cnidaria holobiont growth as a function of environmental conditions, adds a new framework for which to capture the direct cost a symbiont has on Cnidaria hosts and may give us a deeper understanding of the components Cnidaria systems that can lead to mortality.