The effect of hypoxia onDaphnia magnaperformance and its associated microbial and bacterioplankton community: a scope for Genotype x Microbial community interactions upon environmental stress ?

Abstract

AbstractThe depletion of oxygen as a result of increased stratification and decreased oxygen solubility is one of the most significant chemical changes occurring in aquatic ecosystems as a result of global environmental change. Hence, more aquatic organisms will be exposed to hypoxic conditions over time. Deciphering the effects of hypoxia on strong ecological interactors in this ecosystem’s food web is critical for predicting how aquatic communities can respond to such an environmental disturbance. Here, (sub-)lethal effects of hypoxia and whether these are genotype specific inDaphnia, a keystone species of freshwater ecosystems, are studied. This is especially relevant upon studying genetic responses with respect to phenotypic switches (G x E interactions) upon environmental stress. Further, we investigated the effect of hypoxia on theDaphniamicrobial community to test if the microbiome plays a role in the phenotypic switch and tolerance to hypoxia. For this, twoDaphniagenotypes were exposed for two weeks to either hypoxia or normoxia and host performance was monitored together with changes in the host associated and free-living microbial community after this period. We found G x E interactions for some of the testedDaphniaperformance traits. The microbial community responded to hypoxia stress with responses in the bacterioplankton and in theDaphniaassociated microbial community with respect to species richness and community composition and structure. The latter response was different for the two genotypes suggesting that the microbiome plays an important role in G x E interactions with respect to hypoxia tolerance inDaphnia, but further testing (e.g. through microbiome transplants) is needed to confirm this.