As one of the oldest living metazoans, sponges represent fascinating experimental organisms for studying early animal-microbe relationships. My research involves understanding how sponges, as complex associations of microbes and host cells, process one of their main dietary components: dissolved organic matter (DOM). My thesis aims to elucidate how nutrients are transferred between sponge cells and their associated microbes, and if this varies between sponges with different densities of associated microbes. I use a range of different complementary techniques, including: