A scientist from the University of Leicester has discovered a new type of fossil that sheds light on life in the oceans half a billion years ago. A new study in the journal Proceedings of the Royal Society B details the tiny creatures, which are similar to modern-day algae and may also give scientists insights into the climate changes affecting our oceans.
Plankton fossils from 500 million years ago. These tiny algae are less than a millimeter in size. They evolved their own community structure to avoid being eaten by earlier animals. Source: THPHarvey
The fossils are so tiny that they look like balls of spines connected together. Study author Dr Tom Harvey, from the School of Geography, Geology and Environment at the University of Leicester, said: "When I first saw them I had no idea what they were. I wondered if they could be animal eggs, or some new type of organism."
But as more specimens were discovered, Dr. Harvey discovered similarities with modern green algae that live in plankton in ponds and lakes. He explained: "The fossils have the same colony structure as modern algae, with cells connected together so they are arranged neatly and in geometric shapes. But surprisingly, these fossils lived in the ocean, giving people a rare glimpse of what early ocean plankton looked like."
Connection to the Cambrian Explosion
The importance of these fossils lies in their enormous age. It's probably no coincidence that they lived during the period when animals first evolved, the Cambrian 'explosion' of life. In today's world, phytoplankton are an essential food source for nearly all organisms in the ocean. However, modern phytoplankton groups evolved relatively recently, and we do not know which groups of phytoplankton once inhabited the Cambrian oceans.
"When we look at modern plankton, we see that algae form colonies when animals try to eat them. This is a defense mechanism. So the presence of algal colonies during the Cambrian period suggests that early animals evolved to feed on plankton, thus beginning a predator-prey relationship that continues today. Given that plankton is the basis of ocean life, plankton fossils help us build ancient climate models, and these small fossils play an important role in telling the history of life on Earth," Dr Harvey explained.
This new discovery will prompt a rethinking of other early microfossils. For years, scientists thought spiny balls found alone were dormant cysts of single-celled life.
For Dr. Harvey, the new fossils seriously challenge that view: "I wonder if we've been wrong all along, and many of these microfossils actually lived in communities in plankton. It's easy to accidentally break them when we extract fossils from rocks, so we all need to go back to collections, back to our labs, and find out just how common they are."
References "Colonial green algae in Cambrian plankton" by Thomas H.P. Harvey, October 24, 2023, "Proceedings of the Royal Society B".
Compiled source: ScitechDaily