Australia: The Land Where Time Began

A biography of the Australian continent 

The Great Ordovician Biodiversification Event (GOBE) - The Palaeoecological Dimension

There was a spectacular increase in the biodiversity of marine organisms at all taxonomic levels during the Great Ordovician Biodiversity Event (GOBE), largely within the phyla that were established in the Cambrian Explosion that had occurred much earlier. The authors¹ suggest that it probably resulted from a combination of several geological and biological processes and the feedbacks resulting from them. In this paper the authors¹ review the palaeoecological dimension associated with the GOBE. The rise of the Palaeozoic Evolutionary Fauna, that was dominated by suspension feeders and involved a greater occupation of ecospace and ecological structures that were more complex in the Ecological Evolutionary Units P1 and P2, were largely associated with the major increases in α, β and γ biodiversity. These include food webs in the benthos that were more complex than those in the Cambrian, a greater degree of tiering, especially above the sediment-water interface, and guild structures that developed, which indicated the increased competition for particular resources between taxa.. A profound change in reef composition characterised the Ordovician, that included microbial-dominated reefs in the Early and Middle Ordovician, switching to reefs dominated by metazoans in the Late Ordovician. Deep water fossil assemblages increased in complexity, beginning in the Early Ordovician, and marking increased exploitation in that environment, and bioerosion and encrusting strategies, as well as the appearance of cryptic communities, that were permitted by the development of hardgrounds.

A significant increase in the diversity of phytoplankton and a significant development of zooplankton, that included planktotrophic larvae from a range of invertebrate clades, in the water column. A diverse fauna of pelagic vertebrates, molluscs and arthropods were allowed to become established by the revolution in the plankton, and it also promoted a rise of suspension feeders among the benthos. The authors¹ suggest that a major driver for biodiversification may have been an escalation among the predators, and therefore community evolution.

Sources & Further reading

1. Servais, Thomas, Alan W. Owen, David A. T. Harper, Björn Kröger, and Axel Munnecke. "The Great Ordovician Biodiversification Event (Gobe): The Palaeoecological Dimension." Palaeogeography, Palaeoclimatology, Palaeoecology 294, no. 3–4 (8/15/ 2010): 99-119.