Quantifying sponge host and microbial symbiont contribution to dissolved organic matter uptake through cell separation (original) (raw)

Sponge-microbe symbioses underpin the ecological success of sponges in many aquatic benthic ecosystems worldwide. These symbioses are often described as mutually beneficial, but identifying positive symbiotic interactions and quantifying the contribution of partners to physiological processes is challenging. For example, our understanding of the relative contribution of sponge cells and their microbial symbionts to the uptake and exchange of dissolved organic matter (DOM)—a major component of sponge diet—is limited. Here, we combined host-symbiont cell separation with pulse-chase isotopic labelling in order to trace the uptake of13C- and15Nenriched DOM into sponge cells and microbial symbionts of the encrusting Caribbean spongesHaliclona vansoestiandScopalina ruetzleri, which are low microbial abundance (LMA) species. Sponge cells were responsible for >99% of DOM assimilation during the pulse-chase experiment for both sponge species, while the contribution of symbiotic microbes t...