Oceanic ecosystems are dominated by minute microorganisms that play a major role in food webs and biogeochemical cycles. Many microorganisms thrive in the dilute environment due to their capacity to locate, attach to, and use patches of nutrients and organic matter. A combination of in situ sampling techniques and next generation sequencing has been used to study the biological filtration of microbes at the phylotype level to test for differential grazing efficiency for different bacteria by benthic tunicates (ascidians).