542 million years ago, there was a rapid diversification of life forms on planet earth. Suddenly, bam, there were more kinds of animals than ever. This period in time is aptly named “The Cambrian Explosion,” and it happened in the sea, before animals realized there was a ton of land up there to conquer.
Not only were there more kinds of animals, the animals were getting more complex. For the first time ever, fossils from the Cambrian explosion captured the existence of animals with generalized skeletons, like ours.
Things changed a lot in this time, because these new animals could burrow into sand and mud. In other words, these new animals could physically alter their environment, and turn it from a 2-dimensional environment to a 3D space.
Doing so opened up new habitats and niche space, which is what allowed more animals to co-exist, because there were new slots in the food chain and physical environment for new animals to exist. A change that vast to an ecosystem changed the flow of nutrients and inter-relational dynamics on the seafloor.
New research out of MUN, on fossils from Newfoundland and Labrador, was published by the Geological Society of London. It provides new insights into exactly which burrowing animals were the most important engineers.
Dr. Duncan McIlroy (Department of Earth Sciences) co-wrote the paper. “For the first few billion years of life on Earth, life in the oceans was pretty simple,” said Dr. McIlroy. “It was mostly microscopic. Most of the organic matter ended up on the seafloor, and became permanently buried. ”
Buried organic materials is wasted organic material. These new burrowing animals tapped into that resource. “It was not until the start of the Cambrian period, around 542 million years ago, that animals like worms and arthropods evolved, and started burrowing into the seafloor in search of buried nutrients.” Dr. McIlroy explained.
The research argues that this evolution of burrowing caused a fundamental change in the interactions between the Earth’s chemistry, geology, and biology, helping to trigger The Cambrian Explosion.
In addition to allowing these animals access to buried (lost!) organic matter, and new habitats and niche space, their activities introduced oxygen and other elements to the seafloor environment, that increased the activity and diversity of micro-organisms in the seafloor sediments.
The paper theorizes that the additional microbial food resources engineered by burrowing may have fuelled the Cambrian-era explosion of animal life, by providing a rich new energy source able to meet a higher metabolic demand for more and more complex animals.
“The process by which animals change an environment to their own benefit is known as ecosystem engineering. By studying the fossilized burrows from the earliest Cambrian rocks preserved in Newfoundland and Labrador, we could apply modern ecological methods to try to better understand what these pioneer burrowers were doing, and how their behaviour affected the surrounding sediment and water column.”
“The creation of the more 3D Cambrian world, with positive feedback loops between microbial productivity in the sediment, and the burrowing organisms that feed on those microbes, is an example of ecosystem engineering at the grandest scale,” said Dr. McIlroy. “One might even call it biosphere engineering!”