Flow-ecology relationships that underpin environmental flows are often not well-established, particularly at lower trophic levels. We are studying downstream effects of small environmental flows in a coastal Victorian stream by measuring changes in the periphyton assemblage using DNA metabarcoding. We expect the periphyton assemblage to rapidly shift in response to each experimental release in the regulated stream in comparison to nearby, unregulated streams. Documenting a response from the primary producers provides evidence to managers that environmental flows may be influencing ecosystems from the resource base up.