It is a remarkable survivor of an ancient aquatic world, now a new study sheds light on how one of Earth’s oldest reefs was formed. Researchers have discovered that one of these reefs, now located on dry land in Namibia was built almost 550 million years ago, by the first animals to have hard shells.
These tiny creatures first developed the ability to construct hard protective coats and build reefs; the purpose of these reefs was to provide shelter. These were the first creatures to build structures similar to non-living reefs, which form through erosion and sediment deposits.
Scientists say it was at this point that tiny aquatic creatures developed the ability to construct hard protective coats and build reefs to shelter and protect them in an increasingly dangerous world.
The study reveals that the animals attached themselves to fixed surfaces and to each other by producing natural cement composed of calcium carbonate to form rigid structures.
The creatures, known as Cloudina built reefs in ancient seas that now form part of Namibia. Their fossilised remains are the oldest reefs of their type in the world.
Cloudina were tiny, filter-feeding creatures that lived on the seabed during the Ediacaran Period, which ended 541 million years ago. Fossil evidence indicates that animals had soft bodies until the emergence of Cloudina.
Researchers say animals may have developed the ability to build reefs to protect themselves against increased threats from predators. Reefs also provided access to nutrient-rich currents at a time when there was growing competition for food and living space.
Previously, the oldest reefs on record were dated to about 530 million years ago.
Scientists said the development of hard biological structures, through a process called biomineralisation, sparked a dramatic increase in the biodiversity of marine ecosystems. “Modern reefs are major centers of biodiversity with sophisticated ecosystems. Animals like corals build reefs to defend against predators and competitors,” said Rachel Wood, professor at the University of Edinburgh, who led the study. “We have found that animals were building reefs even before the evolution of complex animal life, suggesting that there must have been selective pressures in the Precambrian Period that we have yet to understand.”
The study was published in the journal Science and was carried out in collaboration with the University College London the Geological Survey of Namibia. The work was supported by the Natural Environment Research Council, the University of Edinburgh and the Laidlaw Trust.