One of the interesting things that happened once animals evolved was that they started to make holes in the sediment. This not only opened a new niche once they figured out how to dig but also changed how some elements (e.g., sulfur) exchanged with the water above. www.nature.com/articles/nge... 🧪⚒️

Protracted development of bioturbation through the early Palaeozoic Era - Nature Geoscience

Mobile organisms first appeared in the fossil record prior to the Precambrian–Cambrian transition. Sediment textures indicate that the degree of sediment mixing by animal activity remained low for 120...

It seems to have started already in the late Ediacaran (even before mineral shells) that some things began to go into the sediment (doi.org/10.1130/G328...doi.org/10.3389/fmar...).

Frontiers | Digging Deeper: Bioturbation increases the preserved sulfur isotope fractionation

Bioturbation enhances mixing between the seafloor and overlying ocean due to changes the redox state of the sediment and influences the biogeochemical cyclin...