Tiny Fossils-Big Data: microplankton and their ecology in the climate system

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The Mesozoic marine revolution stabilized Earth's climate by shifting the locus of carbonate preservation in the ocean from continental shelves to the deep-sea. The shift was largely due to the two different groups of microplankton, calcareous nannofossils and the planktic foraminifera. These groups sequester carbon on the seafloor in substantial amounts; nearly 40% of the seafloor today is covered by calcareous ooze derived from these taxa. Other important groups primarily produce siliceous material. The heterotrophic planktic foraminifera produce carbonate tests, heterotrophic radiolarians secrete siliceous tests, the calcareous nannofossils (inc. coccolithophorids) are autotrophs, and the autotrophic diatoms produce siliceous frustules. Because these organisms form much of the sediment on the seafloor, there is a connection between their evolution and the marine sedimentary record. Their evolution is controlled by a mix of biotic (e.g., diversity dependence) and abiotic (climate and oceanography) factors. There are, however, gaps in our understanding of the connections between these factors and the evolution of these groups. For example, the calcite compensation depth (CCD), the depth above which carbonate (CaCO3) is preserved and thus CO2 stored, is the most important single threshold in the marine carbonate cycle. It is thought to be governed by global climate, geochemical cycles (e.g., weathering of the continents), calcareous plankton productivity, sea level, and circulation. Ecological or evolutionary changes are generally not included when discussing past CCD fluctuations, despite evidence that local CaCO3 flux influences the CCD. Climate and biogeochemical models generally ignore key aspects of pelagic microorganisms: their evolution, ecology, abundances, seasonal productivity or flux, or even the size of their shells or liths. My group will address this key question: How does plankton ecology affect pelagic carbonate and siliceous production dynamics? The four main mineralized microfossil groups provide an excellent experimental set up. Studying them in tandem allows us to examine the differential success among the different groups, their evolution, and the impact(s) they have on climate and marine sediments. Within the literature, it is rare to examine these groups other than in isolation. Even when they are examined together, typically their spatial distribution, population dynamics, seasonality, or their role as sediment producers are studied in isolation - we only think of each groups' macroevolutionary success. This research program will address these weaknesses by using novel approaches utilizing a new synthetic data compilation. This program of study will use a holistic approach to look at the ecological success and spatial patterns of these organisms over the past 200 million years.