Study ties Cambrian 'fecal revolution' to early marine ecosystem complexity

An international study led by Flinders University argues that rising volumes of animal waste helped reshape early oceans and fuel more complex marine ecosystems, a process the authors call a "fecal revolution." Writing in Trends in Ecology & Evolution, fossil and evolutionary researchers from Australia and Germany link buildup of fossilized fecal pellets, or coprolites, to redistribution of organic matter and nutrients around the Cambrian Explosion roughly 540 million years ago. During that interval, the first complex marine ecosystems developed and most major animal groups began to appear. Primitive sea animals deposited coprolites throughout early Cambrian environments, and the authors say moving nutrients and carbon through the oceans may have created conditions that encouraged organisms to evolve and diversify. Dr. Russell Bicknell, an Australian Research Council DECRA fellow at Flinders University's College of Science and Engineering, said the importance of feces in ancient ecosystems is often overlooked next to rising oxygen levels and other factors. With lead author Dr. Julien Kimmig of Germany's Karlsruhe Institute of Technology, the team examined ancient diets, developing digestive systems, and trophic interactions that describe how organisms obtain food and transfer energy. The earliest animals appeared approximately 600 million years ago during the Ediacaran Period. More elaborate digestive systems and the first fossilized coprolites began appearing near the start of the Cambrian. Evidence comes from more than 35 fossil deposits worldwide. Fossilized digestive systems and coprolites became increasingly varied in size, shape, and complexity as the Cambrian progressed. Bicknell said fecal matter ranges from microscopic pellets to centimeter-scale coprolites containing shells and other animal fragments. Some specimens preserve recognizable prey remains, offering direct evidence of early diets. Growing variety reflects specialized feeding strategies and more complex predator-prey relationships. Early arthropods evolved specialized foreguts and digestive glands capable of processing a wider variety of food. As animals processed broader diets, waste moved organic carbon and nutrients into new parts of the marine environment. Bicknell said the fossil record shows feeding-strategy evolution aligning with production and distribution of organic carbon and nutrients toward conditions later seen in modern oceans and on land, where fertilizer is used in food production. The research was funded through an Australian Research Council grant and a MAT Program postdoctoral fellowship to Bicknell.