ECOSYSTEM ENGINEERING DURING AN INTERVAL OF GLOBAL WARMING: THE EARLY TRIASSIC HOTHOUSE OCEAN

Ecosystem engineers are organisms that significantly alter habitats thus affecting physical and chemical processes as well as biodiversity. The Early Triassic represents an interval which may have experienced some of the hottest ocean temperatures in the Phanerozoic. Complete ecosystem analyses are needed for various iterations of Early Triassic oceans, but ecosystem engineers stand out as warranting high priority for study, because of their potential importance towards understanding ecosystem function in the modern ocean as it continues to warm over the next one hundred years. The Early Triassic ocean is not a direct analogue for the modern ocean, as a number of biological, geochemical, paleogeographic, and climatic factors differ. But, several significant patterns for Early Triassic ocean ecosystem engineers have emerged which are likely to appear in the future global warming ocean. Metazoan reefs represent large-scale ecosystem engineering in many nearshore marine carbonate environments, and contain much of the biodiversity of modern oceans. In the Early Triassic reefs were severely diminished, of small size typically consisting primarily of microbial fabrics. Metazoan components can include sponges as well as serpulids and towards the end of the Early Triassic bivalves. Reduced bioturbation is also a common characteristic of the Early Triassic, and because this ecosystem engineering process influences sediment properties and marine biogeochemical cycles similar wide-scale reductions in modern marine ecosystems could lead to significant impacts. Proliferation of shelled ecological dominants or disaster taxa in Early Triassic oceans may have also had a strong ecological engineering effect. Compounding these phenomena was a reduction in size of a variety of Early Triassic marine organisms, which can have a significant effect on the products of engineering organisms. Further analysis of Early Triassic marine ecosystems will yield additional ecosystem engineer characteristics worthy of focused study. Understanding the nature of ecosystem engineers in the Early Triassic hothouse ocean is a necessary step towards providing a full understanding of projected conditions for future ocean ecosystems in a world that is rapidly warming.