Ecological outcomes of echinoderm disease, mass die-offs, and pandemics

Abstract

Echinoderms are an ancient deuterostome phylum of marine animals that, under physiological stresses or increases in pathogen populations, often from environmental changes, can be infected and may succumb to diseases in both larvae and adults. Mass die-offs of echinoderms that are keystone species alter their essential functions in maintaining ecosystem structure and diversity. Changes in echinoderm population can alter trophic cascades that result in phase shifts to a different ecological structure composed of a different assemblage of species. An example is a shift to macroalgal dominated marine habitats when sea urchin populations decrease from disease. Alternatively, mass die-offs of predatory sea stars and the resulting population explosion of the prey echinoderm herbivores can drive phase shifts to barrens. The shifted ecosystems are either maintained for long periods or may return to the previous structure depending on the time required for echinoderm population recovery from disease, the recovery of the echinoderm predator, and the time required for recolonisation and growth to establish the alternative stable ecological structure. Hence, echinoderm pathology versus healthy echinoderm populations have direct impacts on marine ecology.