Right at the bottom of the deep sea, the first very simple forms of life on Earth probably emerged a long time ago. Today, the deep sea is known for its bizarre fauna. Intensive research is being conducted into how the number of species living on the sea floor have changed in the meantime.
Some theories say that the ecosystems of the deep sea have emerged again and again after multiple mass extinctions and oceanic upheavals. Today’s life in the deep sea would thus be comparatively young in the history of the Earth. But there is increasing evidence that parts of this world are much older than previously thought.
A research team led by the University of Göttingen has now provided the first fossil evidence for a stable colonization of the deep sea floor by higher invertebrates for at least 104 million years. Fossil spines of irregular echinoids (sea urchins) indicate their long-standing existence since the Cretaceous period, as well as their evolution under the influence of fluctuating environmental conditions. The results have been published in the journal PLOS ONE.
The researchers examined over 1,400 sediment samples from boreholes in the Pacific, Atlantic and Southern Ocean representing former water depths of 200 to 4,700 meters. They found more than 40,000 fragments of spines, which they assigned to a group called irregular echinoids, based on their structure and shape.
For comparison, the scientists recorded morphological characteristics of the spines, such as shape and length, and determined the thickness of around 170 spines from each of two time periods. As an indicator of the total mass of the sea urchins in the habitat—their biomass—they determined the amount of spiny material in the sediments.
2023-09-05 20:00:04
Link from phys.org
