Developmental consequences of association with a photosynthetic substrate for encapsulated embryos of an intertidal gastropod

► We tested for developmental consequences of egg mass deposition on macrophytes. ► In high light, gastropod embryos develop faster on a photosynthetic surface. ► In low light, development and growth are faster on a non-photosynthetic surface. ► Macrophytes also reduce the growth of fouling and potentially harmful microphytes. ► Egg mass-macrophyte interactions are driven by oxygen and depend on light conditions.