Marine bioturbation collapse during Early Jurassic deoxygenation: implications for post-extinction marine ecosystem functioning

Abstract

Abstract Climate change is undermining the health and integrity of seafloor ecosystems, with declines in bioturbation expected to impact future ecosystem functioning. We explored changes in the nature and degree of bioturbation during Early Jurassic global warming and ocean deoxygenation. Understanding how these communities responded can help anticipate how bioturbation and ecosystem functioning might change over large spatial and temporal scales. Trace and body fossils from outcrop and core in the Cleveland Basin, UK show how healthy seafloor communities deteriorated through the Pliensbachian spinatum Zone, and macroinfaunal behaviour fluctuated across the Pliensbachian–Toarcian boundary coincident with mass extinction. Deoxygenation began above the stage boundary, and conditions deteriorated until bioturbation ceased completely (upper tenuicostatum Zone) for 0.6–2.5 Ma, longer than anywhere else in NW Tethys. The macroinfaunal record revealed new details on the progression and timing of deoxygenation, benthic recovery and fluctuations in the palaeoredox boundary. After the oceanic anoxic event infauna were fewer, smaller and did not mix sediments to depth, and while the depth and diversity of bioturbation had increased by the fibulatum Subzone ( bifrons Zone), the benthos had not recovered to late Pliensbachian pre-oceanic anoxic event state. Bioturbation collapse over large parts of the Northern Hemisphere probably contributed to regional-scale changes in ecosystem functioning.