ENERGETIC STRUCTURE IN EARLY ANIMAL ECOSYSTEMS QUANTIFIED THROUGH CAMBRIAN SITES OF EXCEPTIONAL PRESERVATION

Sites of exceptional preservation from the Cambrian are crucial for understanding early animal evolution. By preserving the most labile structures and organ systems, sites such as the Burgess Shale in Canada and Chengjiang in China provide information on the origins of phyla as disparate as arthropods and chordates. However, our understanding of the ecosystems in which these animals lived is comparatively more rudimentary. Recent studies have tackled ecological questions in the Cambrian through patterns of taxonomic diversity, which does not necessarily correlate with ecosystem complexity or trophic structure. Trophic structure is a fundamental characteristic in determining how a community of animals behaves but is rarely tractable in fossil contexts when trophic behaviour cannot be directly observed.

Here, we present a multi-locality community study of three sites from the Burgess Shale and one from Chengjiang. We approach this data from the perspective of trophic structure by analyzing the distribution of biovolume (as a proxy for biomass) of these animal communities through four areas of the water column: the infauna, the epibenthos, the nektobenthos, and the pelagic realm. We are thus able to discern the localities’ unique energetic structures (where energy is being sequestered within these communities) without the need to infer direct trophic relationships between taxa. We see not only that the distributions of biomass throughout the water column differ across localities, but also the total biomass in the ecosystem. Additionally, analysis of each locality divided into 10cm stratigraphic bins in show that the energetic structure is not stable and can change drastically across relatively short timescales.

These results carry significant ramifications that underscore the uniqueness of each Cambrian locality. First, the energetic structure of each of the best studied Cambrian localities differs from each other drastically. Second, the total biovolume, and therefore total energy supported, of each community also differs drastically between all sites. Third, within a single locality the energetic structure can change many times and rapidly. Ultimately, quantifying the energetic structure of these early ecosystems allows us to further investigate how trophic strategies may interact with other the ecological drivers in the Cambrian.