Terrestrial forcing of marine biodiversification

The diversification of the three major marine faunas during the Phanerozoic was intimately coupled to the evolution of the biogeochemical cycles of carbon and nutrients via nutrient runoff from land and the diversification of phosphorus-rich phytoplankton. Nutrient input to the oceans has previously been demonstrated to have occurred in response to orogeny and fueling marine diversification. Although volcanism has typically been associated with extinction, the eruption of continental Large Igneous Provinces (LIPs) is also a very significant, but previously overlooked, source of phosphorus involved in the diversification of the marine biosphere. We demonstrate that phosphorus input to the oceans peaked repeatedly following the eruption and weathering of LIPs, stimulating the diversification of nutrient-rich calcareous and siliceous phytoplankton at the base of marine food webs that in turn helped fuel diversification at higher levels. These developments were likely furthered by the evolution of terrestrial floras. Results for the Meso-Cenozoic hold implications for the Paleozoic Era. Early-to-middle Paleozoic diversity was, in contrast to the Meso-Cenozoic, limited by nutrient-poor phytoplankton resulting from less frequent tectonism and poorly-developed terrestrial floras. Nutrient runoff and primary productivity during the Permo-Carboniferous likely increased, based on widespread orogeny, the spread of deeper-rooting forests, the fossil record of phytoplankton, and biogeochemical indices. Our results suggest that marine biodiversity on geologic time scales is unbounded (unlimited), provided sufficient habitat, nutrients, and nutrient-rich phytoplankton are also available in optimal amounts and on optimal timescales.

Automated summary

The diversification of marine faunas during the Phanerozoic is closely related to the evolution of carbon and nutrient biogeochemical cycles, particularly the nutrient runoff from land and the diversification of phosphorus-rich phytoplankton. The eruption and weathering of continental Large Igneous Provinces (LIPs) are significant sources of phosphorus that stimulate the diversification of marine life. This process, along with the evolution of terrestrial floras, leads to an increase in marine biodiversity. In contrast, nutrient-poor phytoplankton limited the diversity in the early-to-middle Paleozoic due to less frequent tectonic activity and poorly-developed terrestrial floras. The study suggests that marine biodiversity on geological time scales is unlimited, given sufficient habitat, nutrients, and nutrient-rich phytoplankton.