Ongoing anthropogenically-driven changes to the ocean are expected to alter marine ecosystems on timescales outside of human experience. To anticipate ecosystem responses and effectively manage resources, we must understand the effects of these perturbations. Here we present results of an ongoing study of marine paleocommunity dynamics during the Mesozoic (250 to 66 mya), an interval of Earth’s history when the groundwork for modern ocean ecosystems was laid. Increasing ecospace utilization, predation intensity, and motility during the Mesozoic suggest that the marine ecological complexity has increased through geologic time as specialized morphologies and functions evolved. To determine the reliability of fossil food web reconstructions and understand how properties such as functional diversity, trophic level structure, species dietary breadths, food chain lengths, and food web modularity may be affected by preservation biases, we simulated the fossilization of a highly resolved modern Jamaican reef community for comparison. We then tested the hypothesis of increasing community complexity by reconstructing a marine food web from the Middle Triassic (247-242 mya), an early Mesozoic interval. Similar properties were evaluated from the Triassic food web and compared to the modern Jamaican coral reef ecosystem, as well as applied to models of paleocommunity global stability and resilience.
Results/Conclusions
Analysis of the modern reef reveals a highly structured system in which 728 species can be collapsed into 249 trophospecies, further organized into 110 unique feeding guilds. The food web is organized into four modules, each comprising a set of distinct producers and food chains. Several invertebrate food chains exceed 5 steps in length, but those chains, and the modules, are bound together by pelagic carnivorous vertebrates that feed at multiple trophic levels and across modules. Comparison between the modern food web and the simulated fossilized version indicates that despite loss of species (particularly soft-bodied organisms), guilds, and trophospecies interactions during the fossilization process, the overall guild diversity, structure, and modularity of the fossil ecosystem remained intact. Furthermore, overall richness of planktonic species can be estimated with high accuracy based on food chain relationships between plankton guilds and preserved zooplanktivores. In contrast, the reconstructed Middle Triassic marine food web had relatively low ecosystem complexity. Increasing global taxonomic richness and escalation of predator-prey dynamics during the later Mesozoic likely led to increased ecospace utilization. The creation of deep-time paleocommunity food webs has the ability to advance our current knowledge of how natural systems behave, especially in response to future environmental changes.