Abstract
Abstract. Phytoplankton responses to a ∼350 kyr (kiloyear) long phase of gradual late Maastrichtian (latest Cretaceous) global warming starting at ∼66.4 Ma can provide valuable insights into the long-term influences of global change on marine ecosystems. Here we perform micropaleontological analyses on three cores from the New Jersey paleoshelf to assess the response of phytoplankton using cyst-forming dinoflagellates and benthic ecosystems using benthic foraminifera. Our records show that this latest Maastrichtian warming event (LMWE), characterized by a 4.0±1.3 ∘C warming of sea surface waters on the New Jersey paleoshelf, resulted in a succession of nearly monospecific dinoflagellate-cyst assemblages, dominated by the species Palynodinium grallator. This response, likely triggered by the combination of warmer and seasonally thermally stratified seas, appears to have been more intense at offshore sites than at nearshore sites. The LMWE, and related dinoflagellate response, is associated with an impoverished benthic ecosystem. A wider geographic survey of literature data reveals that the dominance of P. grallator is a marker for the LMWE throughout the northern midlatitudes. While the dinocyst assemblage returned to a stable, normal marine community in the last tens of thousands of years of the Maastrichtian, benthic foraminiferal diversity appears to have remained slightly suppressed. Increased ecosystem stress during the latest Maastrichtian potentially primed global ecosystems for the subsequent mass extinction following the Cretaceous Paleogene (K–Pg) boundary Chicxulub impact.
Highlights
Forced increases in atmospheric greenhouse gas concentrations are projected to substantially impact climate on a global scale in the near future (IPCC; Pachauri et al, 2014)
With respective first appearance dates of 66.77 and 67.0 Ma (e.g., Williams et al, 2004), both P. grallator and D. carposphaeropsis were already well-established before the latest Maastrichtian warming event (LMWE) but generally occurred in low numbers
We argue that the combination of a more frequent thermally stratified water column with higher mean annual seawater temperatures during the LMWE stimulated dinoflagellate-cyst production
Summary
Forced increases in atmospheric greenhouse gas concentrations are projected to substantially impact climate on a global scale in the near future (IPCC; Pachauri et al, 2014). The higher upper ocean temperatures predicted under future climate scenarios will increase stratification of the water column and differentially affect growth of phytoplankton groups in the global oceans (Behrenfeld et al, 2006; Boyd and Doney, 2002; Doney, 2006). Such a warmer ocean might bear analogies in the Cretaceous to Paleogene greenhouse world (Hay, 2011). The potential consequences of such largescale patterns of climate variability for marine dinoflagellate communities are not well understood (Moore et al, 2008)
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