COMPARATIVE TAXONOMIC AND FUNCTIONAL DIVERSITY OF BRYOZOAN MOUNDS ABOVE AND BELOW THE CRETACEOUS – PALEOGENE BOUNDARY AT STEVNS KLINT, DENMARK

The functional diversity and spatial heterogeneity of ecological communities are key determinants of ecosystem persistence and resilience, and these dimensions of biodiversity are the focus of much modern conservation research. Mass extinctions, however, are usually characterized in terms of taxonomic diversity, creating a disconnect between paleobiology and modern ecology. Bridging this gap requires an integrative understanding of the rare mass extinction boundary localities with fossil preservation across sufficient space and time. In this study, we examine how the effect of the Cretaceous – Paleogene mass extinction on bryozoan taxonomic and functional diversity varied across paleoenvironments at Stevns Klint. Stevns Klint, Denmark is a UNESCO World Heritage Site known for its exceptional exposure of the K-Pg boundary. We sampled the Sigerslev and Højerup Members (latest Maastrichtian) and the Korsnœb Member (earliest Danian), which all consist of subtidal bryozoan-supported reef mounds. The taxonomic diversity and the depositional environments of Stevns Klint are both well described. We took replicate samples of distinct microhabitats across multiple bryozoan mounds within each stratigraphic member. Fossils were sieved from their chalk matrix, and all fossil material from the > 2mm size fraction was imaged and identified. The 125 µm – 250 µm size fraction was used to estimate bryozoan biomass density. Preliminary results show bryozoan biomass, taxonomic diversity, and functional diversity exhibit correlated variation across a bryozoan mound, but the nature of this spatial heterogeneity changes after the mass extinction.