Theoretical Ecospace for Ecosystem Paleobiology: Energy, Nutrients, Biominerals, and Macroevolution

Abstract

Changes in nutrient cycles and energy fluxes (i.e., ecosystem dynamics) likely drove numerous trends and disruptions in the history of life. Advances in geochemistry offer great insights into paleoecosystem function, as does an understanding of the biogeochemical roles played by ancient organisms. A theoretical ecospace that describes the chemical exchanges between organisms and their environments is presented. Previous descriptions of ecospace principally described spatial and physical aspects of ecology; the new ecospace description broadens the concept to encompass a wider range of ecological processes that control abundance and diversity of fossil organisms. Organisms require materials from the environment for generating energy and building tissues, and these factors are broken down, ultimately specifying particular substances acquired from the environment. Different organisms require specific substances in different amounts depending on factors such as physiology, environmental conditions, etc.; thus, physiological ecospace describes an organism's sensitivity to ecosystem/earth system perturbations and trends. Several examples relating to organisms' requirements for skeletal minerals are reviewed, and a new analysis of extinction selectivity related to ocean acidification is presented. Selective extinction of heavily calcified metazoa is demonstrated to have occurred at least eight times during the Phanerozoic, including the early Cambrian, Frasnian (Late Devonian), and Aptian (Early Cretaceous). Multidimensional structure of ecospace occupation (e.g., correlations among ecological traits) strongly controls the effects of an extinction such that the same kill mechanism applied at different times will affect the ecological composition of the biosphere in a variety of ways.