Constructing an Eocene Marine Ecosystem Sensitivity Scale

Abstract:

A key question in the face of current global environmental change is how marine ecosystems will respond and evolve in the future. To answer this, we first need to understand the relationship between environmental and ecosystem change – i.e., the ecosystem sensitivity. Addressing this question requires understanding of how biota respond to (a succession of) sudden environmental perturbations of varying sizes and durations in varying background conditions (i.e., climatic, oceanographic, biotic).

Here, we compare new and published data from the Early to Middle Eocene greenhouse world to understand the sensitivity of marine ecosystems to background environmental change and hyperthermal events. This work focuses on the early Paleogene, because it is considered to be a good analog for a future high CO₂ world. Newly generated high-resolution multiproxy datasets based on northern Atlantic DSDP Leg 48 and IODP Leg 342 material will allow us to compare the marine ecosystem responses (including bentho-pelagic systems) to abiotic drivers across climatic disruptions of differing magnitude.

Initial results of a benthic foraminiferal community comparison including the PETM and ETM2 hyperthermals in the northeastern Atlantic DSDP sites 401 and 550¹ suggest that benthic ecosystem sensitivity may actually be non-linearly linked to background climate states as reflected by a range of geochemical proxies (XRF, TOC, CaCO₃, grain sizes, XRD clay mineralogy and foraminiferal δ¹⁸O, δ¹³C, Mg/Ca)^2,3, in contrast to planktic communities⁴. Testing the type of scaling across different taxa, communities, initial background conditions and time scales may be the first big step to disentangle the often synergistic effects of environmental change on ecosystems⁵.

References:

¹D’haenens et al., 2012, in prep.

²Bornemann et al., 2014, EPSL

³D’haenens et al., 2014, PA

⁴Gibbs et al., 2012, Biogeosc.

⁵ Norris et al., 2013, Science