| Summary: | The Cretaceous-Paleogene (K/P) bolide impact decimated surface ocean ecosystems. While the extinction has been well studied, there have been few investigations of the recovery of ecosystems from the K/P extinction. The relationship between the post-extinction ecologies of nannoplankton and planktonic foraminifera can lend insight into how ecosystems were rebuilt after the K/P impact. This study utilizes multivariate analysis on abundance counts from five sites with wide global distribution to compare the recoveries of these calcareous plankton groups. The analysis shows there is a distinct geographical differentiation in the recovery of both groups, with assemblages in the northern hemisphere surface oceans diversifying more slowly than southern hemisphere surface oceans. This is most likely a result of higher extinction intensity caused by the concentration of dust created by the bolide impact in the northern hemisphere. The multivariate analysis results suggest a probable long-term influence on the post-extinction marine ecosystem was increased nutrient concentration in the surface ocean resulting from the collapse of the biological pump. Nannoplankton recover before planktonic foraminifera in the open ocean, as expected, but after planktonic foraminifera on the shelf. Dinoflagellates, which were common at many shelf locations across the K/P boundary may have provided another food source for planktonic foraminifera and hindered nannoplankton diversification by invading niche space emptied by the K/P extinction. Ecological recovery of calcareous microplankton took place only after the biologic pump was restored ~300 Kyr after the K/P extinction, removing the enhanced nutrient concentrations from the surface ocean.
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