Resilience of marine invertebrate communities during the early Cenozoic hyperthermals

William J Foster,Christopher L Garvie,Martin Aberhan,John W Counts,Anna M Weiss,A D Muscente,Rowan C Martindale

doi:10.1038/s41598-020-58986-5

Abstract

The hyperthermal events of the Cenozoic, including the Paleocene-Eocene Thermal Maximum, provide an opportunity to investigate the potential effects of climate warming on marine ecosystems. Here, we examine the shallow benthic marine communities preserved in the late Cretaceous to Eocene strata on the Gulf Coastal Plain (United States). In stark contrast to the ecological shifts following the end-Cretaceous mass extinction, our data show that the early Cenozoic hyperthermals did not have a long-term impact on the generic diversity nor composition of the Gulf Coastal Plain molluscan communities. We propose that these communities were resilient to climate change because molluscs are better adapted to high temperatures than other taxa, as demonstrated by their physiology and evolutionary history. In terms of resilience, these communities differ from other shallow-water carbonate ecosystems, such as reef communities, which record significant changes during the early Cenozoic hyperthermals. These data highlight the strikingly different responses of community types, i.e., the almost imperceptible response of molluscs versus the marked turnover of foraminifera and reef faunas. The impact on molluscan communities may have been low because detrimental conditions did not devastate the entire Gulf Coastal Plain, allowing molluscs to rapidly recolonise vacated areas once harsh environmental conditions ameliorated.

Highlights

Human activities are drastically changing conditions in coastal marine ecosystems by polluting, destroying habitats, overexploiting resources, enabling invasive species, and driving climate warming
Our analyses provide evidence for two substantial changes in generic richness: a significant (Kruskall-Wallis test (KW): p < 0.01), temporary drop at the Cretaceous/Paleogene (K/Pg) boundary and high values of richness in the middle Eocene (Lutetian-Bartonian)
The late Ypresian samples, which coincide with the Early Eocene Climatic Optimum (EECO), are less diverse than those of other time bins; some outliers have a greater richness than other time bins (Fig. 1a,b)

Summary

Introduction

Human activities are drastically changing conditions in coastal marine ecosystems by polluting, destroying habitats, overexploiting resources, enabling invasive species, and driving climate warming. The Eocene witnessed two separate long-term warming trends of ~6 °C culminating in the late Ypresian and Bartonian, known as the Early Eocene Climatic Optimum (EECO) and the Middle Eocene Climatic Optimum (MECO), respectively (Fig. S1) Superimposed on these long-term trends are many short-lived intervals of increased carbon injection into the atmosphere and increased sea surface temperatures, known as hyperthermals, and of these the Paleocene-Eocene Thermal Maximum (PETM) and the Eocene Thermal Maximum 2 have the highest magnitude and pace[3] (Fig. S1). The PETM was the most rapid warming event of the early Cenozoic and had the largest ecological impact on marine ecosystems of any hyperthermal during that time[7]. To improve our understanding of the impact of the early Cenozoic hyperthermals on shallow marine benthic communities, we quantitatively investigated changes in their diversity and composition along the Gulf Coastal Plain. The faunal record does not allow for the assessment of the short-term (up to millennial-scale) responses of molluscs to the early Cenozoic hyperthermals, our comprehensive analysis shows that the early Cenozoic hyperthermals did not significantly impact the evolutionary history of benthic molluscan communities

Methods

Results

Conclusion