Complex marine bioturbation ecosystem engineering behaviors persisted in the wake of the end-Permian mass extinction

Abstract

the end-permian mass extinction was the most severe mass extinction event of the phanerozoic and was followed by a several million-year delay in benthic ecosystem recovery. While much work has been done to understand biotic recovery in both the body and trace fossil records of the early triassic, almost no focus has previously been given to analyzing patterns in ecosystem engineering complexity as a result of the extinction drivers. Bioturbation is a key ecosystem engineering behavior in marine environments, as it results in changes to resource flows and the physical environment. Thus, the trace fossil record can be used to examine the effect of the end-Permian mass extinction on bioturbating ecosystem engineers. We present a dataset compiled from previously published literature to analyze burrowing ecosystem engineering behaviors through the permian-triassic boundary. We report two key observations: first, that there is no loss in bioturbation ecosystem engineering behaviors after the mass extinction, and second, that these persisting behaviors include deep tier, high-impact, complex ecosystem engineering. These findings suggest that while environmental conditions may have limited deeper burrowing, complex ecosystem engineering behaviors were able to persist in the early triassic. furthermore, the persistence of deep tier bioirrigated three-dimensional network burrows implies that benthic biogeochemical cycling could have been maintained at pre-extinction states in some local environments, stimulating ecosystem productivity and promoting biotic recovery in the early triassic.The end-Permian mass extinction is recognized as the most devastating mass extinction event of the Phanerozoic, resulting in an estimated loss of 81% of all marine species 1 and a turnover of the Paleozoic evolutionary fauna to the Modern evolutionary fauna 2 . The proposed trigger of this extinction event -the eruption of the Siberian traps 3-5 -resulted in global warming, ocean anoxia 6 , ocean acidification 7 and habitat loss 8 . The environmental conditions following the eruption of the Siberian traps contributed to prolonged instability of biogeochemical cycles and inhabitable environments that led to a delay in global ecosystem and biotic recovery of several million years 9-11 . The nature of how ecosystems during the Early Triassic returned to stability is not currently well understood. Here, we examine the trace fossil record, an overlooked dataset to understanding biotic recovery. Compared to body fossils, trace fossils not only record the response of soft bodied organisms not easily preserved as fossils to mass extinction events 12 , but, more importantly, record the diversity and complexity of these organisms' behaviors and, in particular, those which involve ecosystem engineering.Ecosystem engineering refers to the behaviors of organisms which modify, create, and maintain habitable environments 13 . Ecosystem engineering can be classified as autogenic or allogenic. Autogenic ecosystem engineers modify environments by providing a ...

A multiscale view of the Phanerozoic fossil record reveals the three major biotic transitions

“…Sepkoski formulated this three-phase model based on a factor analysis of family-level diversity 2 , which became a framework-setting assumption in studies on the evolution of marine faunas and ecosystems [3][4][5][6] , changing our view of the Phanerozoic history of life. However, while the hypothesis continues to serve as a conceptual platform for many recent studies 5,[7][8][9] , some analyses question the validity of Sepkoski's hypothesis 10 . Moreover, because Sepkoski's study predicts unusual volatility in the Modern evolutionary fauna starting during the mid-Cretaceous, a three-phase model fails to capture the overall diversity dynamics during long portions of the Mesozoic 11 .…”

Resilience of infaunal ecosystems during the Early Triassic greenhouse Earth

“…Some deep-tier, high-impact, bioirrigated ecosystem engineering modes persisted in local environments such as the lower shoreface in the late Griesbachian (figs. S3D and S9I), implying that benthic biogeochemical cycling could have been maintained at pre-extinction states in stimulating ecosystem productivity ( 16 ).…”

“…Trace fossils therefore provide unique information on colonization patterns, behavioral styles, ecologic categories, and paleoenvironmental trends of ancient trace-making animals (10)(11)(12)(13). In particular, infaunal ecosystem engineering behaviors could have affected the carbon cycle by increasing the provision and use of organic matter in deeper levels of the sediment, which may have resulted in a positive feedback on biodiversity, increasing the utilizable ecospace, and resource availability (14)(15)(16)(17). Bioturbation also increases the complexity of geochemical gradients in sediments and recycles nutrients such as nitrogen and phosphorus, which, in turn, can greatly increase microbial biomass, attracting further bioturbators and expanding the habitable zone, showing a strong positive feedback effect on biodiversity of skeletonized animals (18)(19)(20)(21).…”

“…Bioturbation also increases the complexity of geochemical gradients in sediments and recycles nutrients such as nitrogen and phosphorus, which, in turn, can greatly increase microbial biomass, attracting further bioturbators and expanding the habitable zone, showing a strong positive feedback effect on biodiversity of skeletonized animals (18)(19)(20)(21). Whether the behavioral and ecologic diversifications of trace-making animals facilitated the initial recovery of skeletonized animals during the Early Triassic has been debated (15,16,22). When and where infauna flourished in this Early Triassic greenhouse world (23) and potential environmental controls remain poorly understood (7,(24)(25)(26)(27)(28).…”

Investigating Biotic Interactions in Deep Time

“…During these periods of ecological reorganization, functional diversity may play important roles in determining the time it takes to reach a new dynamically stable state (Figure 2). Recovery of the marine biological nutrient pump post-KPg was accelerated relative to increase in species richness, suggesting that functional roles of species were more important in shaping whole ecosystem recovery [77][78][79]. Conversely, reassembly of tetrapod communities following the PT mass extinction was marked by the recovery of species richness prior to substantial ecomorphological diversification [16], suggesting that the importance of functional diversity in recovery vary with ecological and environmental setting.…”