73 D18. Paleontology, Extinctions and Paleoecology

Monday, 5 November 2018
8:00 AM - 12:00 PM
Room 141

CHANGING COMMUNITY DYNAMICS ACROSS THE CRETACEOUS-PALEOGENE BOUNDARY IN SEYMOUR ISLAND, ANTARCTICA

Paper number: 73-4
Program: Technical Sessions
Time: 8:45 AM – 9:00 AM

Authors

Abstract

The Cretaceous-Paleogene mass extinction (K-PG) is one of the most widely studied crises of the Phanerozoic, with most work focusing on the impact on specific taxonomic groups. A more complete understanding of the ecological implications of the K-PG and the subsequent reorganization in its aftermath requires a community-wide approach. Here, we lay the groundwork to carry out such an approach by compiling a dataset of 7 Late Cretaceous (Maastrichtian) and 3 Early Paleocene (Danian) marine paleocommunities spanning the K-PG boundary from the Lopez de Bertodano Formation of Seymour Island, Antarctica. Species richness declined from 344 to 155 species, while functional guild richness declined from 57 to 29 across the K-PG boundary. Nektonic predator guilds were heavily affected, including those containing sharks, fish, marine reptiles, and ammonites. Danian communities showed a slight rebound of species richness (210 species), but a further decrease of the number of guilds (22).

Consistent with a hypothesized environmental perturbation during the K-PG, each community was tested for its dynamic response to primary productivity collapse, which allowed us to identify a dramatic shift in the ecological dynamics of communities coincident with the K-PG. 1000 species level food webs were simulated for each community and the fraction of species that became secondarily extinct as a result of increasing levels of primary productivity collapse was estimated using the Cascading Extinction on Graphs model. Pre-extinction communities exposed to low levels of perturbation (< 70% of productivity) yielded uniformly low levels of secondary extinction (< 10%). Conversely, post-extinction communities behaved less uniformly, with greater variance of secondary extinction at all levels of perturbation. These results suggest that under normal conditions of environmental disturbance the pre-extinction communities would have been significantly less susceptible to secondary extinction than the post-extinction communities. Additionally, pre-extinction communities yielded high levels of secondary extinction relative to post-extinction communities at high levels of perturbation, suggesting that the extinction may have conditioned communities that were more capable of enduring mass extinction scale perturbations.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-325002

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