A NEW LOOK AT BUFFERS TO EXTINCTION FOLLOWING LOSS OF PRIMARY PRODUCTIVITY AFTER THE K/T IMPACT

Both floral and isotopic changes indicate a temporary loss of primary productivity following the K/T impact both on land and in the oceans. Phytoplankton with resting stages preferentially survived, suggesting loss of sunlight for several months. Patterns of extinction and survival of many groups were governed by the loss of primary production. Animals in food chains tied directly to primary productivity were especially hard hit, while members of detritus based food chains preferentially survived. Because of the short duration of lost primary productivity, animals with low metabolic rates or those with larval stages not dependent on phytoplankton also preferentially survived. The culling of food chains based on primary production and buffering of food chains based on detritus feeding is controversial and will be explored. Synecologic reorganization following the event involved evolution into vacated niches previously occupied by herbivores and their predators, and these patterns also are suggestive of selective extinction in food chains based on primary productivity. Members of the Paleozoic Marine Evolutionary Fauna (EF) were characterized by low metabolic rates and bodies with relatively little biomass. These features are shared with animals that were buffered from the K/T event. As a result, impacts during the Paleozoic may have been less likely to cause mass extinctions than similarly sized impacts during the dominance of the Modern Marine EF.