Asteroid impact that killed dinosaurs spared freshwater species

The natural biological resilience of freshwater species likely spared them from the otherwise devastating effects of the Chicxulub asteroid impact 66 million years ago, which had caused massive extinction in terrestrial and marine environments. 

When the Manhattan-sized asteroid slammed into Earth, it created an “impact winter,” a mass of dust and smoke in the atmosphere that blocked sunlight from reaching Earth’s sunlight for one or two years. The enduring lack of sunshine and cool temperatures meant a loss of phytoplankton, but CIRES scientist Douglas Robertson and his team propose that freshwater ecosystems proved more resilient to the sudden change. Freshwater species are often adapted to annual freeze-thaw cycles and would have held up better to the impact winter conditions. Fast-flowing streams could have reoxygenated inland waterways and organic matter could have been supplied by surface runoff. Furthermore, since many freshwater organisms have dormant stages they would have been able to wait out the inclement conditions imposed by the asteroid. 

The study was published online in July in the Journal of Geophysical Research Biogeosciences http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20086/abstract