The Benthic Ecosystem Engineers After The Cambrian Explosion

As the ecosystem engineers,benthic organisms change the morphology of sediments through bioturbation and bioirrigating and induce material exchange between sediments and seawater,which not only profoundly affects the colonization of benthic communities into sediments,but also significantly affects the geochemical circulation of atmosphere-ocean-sediment.Trace fossils are the direct evidence of benthic organisms activities,which can provide a basis for studying the evolution of benthic ecosystem engineers in Cambrian and evaluating their ecosystem engineering impacts.In this paper,the Cambrian trace fossil data of Henan province are used for the study of evolution of benthic ecosystem engineers using the ecological space and ecosystem engineering model.The impacts of benthic ecosystem engineers are evaluated from three aspects: functional group,tiering and bioirrigation.The results show that after the Cambrian explosion,benthic ecosystem engineers had occupied deeper tiering and their feeding mode became more diverse.In other words,benthic organisms rapidly occupied a large number of vacant ecological niches and the complexity of ecosystem engineering gradually increased.In early Cambrian,the benthic ecosystem was dominated by simple biodiffusion,but in the middle and late Cambrian,the benthic ecosystem was composed of a variety of types of engineers,mainly reformer and conveyor.The impact value of benthic engineers on ecosystem engineering was gradually increased.Benthic ecosystem engineering can significantly affect the geochemical cycle.In the early Cambrian,benthic ecosystem engineers changed the carbon cycle,phosphorus cycle and other processes in the ocean,leading to the gradual enhancement of atmospheric and oceanic oxidation,which provided necessary conditions for the development of benthic communities.In addition,by affecting the nitrogen cycle in the benthic ecosystem,the engineers accelerated the transformation of nutrients and generated positive feedback to promote the rapid diversification of benthic communities.With the gradual improvement of the benthic ecosystem,the engineers of benthic ecosystem engineering induced the Cambrian substrates revolution,which gradually developed the mixed substrates and inhibited the microbial mat substrates.On the whole,the Cambrian sedimentary substrate is characterized by the coupling development of two kinds of sediments.Although the gradually complex benthic ecosystem inhibited the development of microbial mat substrate,but the microbial mat substrate were still not completely replaced by mixed beds.So,we think the Cambrian has already seen the emergence of benthic engineers with high ecosystem engineering influence,and those engineers had a significant impact on the benthic ecosystem.However,the low average value of ecosystem engineering impact of the benthic organisms gave the Cambrian substrate a dual character.There is no doubt that the substrate revolution is still not over in the Cambrian.