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SUMMARY:Rates of Ocean Acidification: linked to Oceanic Extinction Pattern
 s? - Dr. Ellen Thomas (Yale)
DTSTART:20130221T153000Z
DTEND:20130221T163000Z
UID:TALK43625@talks.cam.ac.uk
CONTACT:Lois Salem
DESCRIPTION:Deep-sea benthic organisms derive food from export of organic 
 matter produced in the photic zone\, so that pelagic and benthic productiv
 ity are coupled in the present oceans\, and severe extinction of plankton 
 and benthos in the geological past thus should have been coupled. Foramini
 feral records\, however\, show decoupling between planktic and benthic ext
 inctions. The asteroid impact at the end of the Cretaceous (K/Pg) caused m
 ass extinction of calcifying plankton (foraminifera and nannoplankton) but
  not of the benthos\, whereas the reverse occurred 10 myr later\, during t
 he carbon-cycle perturbation and global warming at the Paleocene-Eocene bo
 undary. The K/Pg extinction has been interpreted as a darkness-caused coll
 apse of productivity\, but such a collapse is not supported by the lack of
  benthic extinction. Across the K/Pg boundary\, the decrease in export pro
 ductivity was moderate\, regionally variable\, and insufficient to explain
  the severe marine mass extinction at higher levels of the food chain. Acr
 oss the P/E boundary\, productivity increased at many locations close to t
 he continents\, whereas open ocean productivity may have declined\, i.e.\,
  the trophic resource continuum increased. There is thus no solid evidence
  that planktic or benthic extinctions were linked to changes in (export) p
 roductivity. The unexpected difference between planktic and benthic extinc
 tion patterns may have been caused by the occurrence of ocean acidificatio
 n at different rates. Very rapid surface ocean acidification at the K/Pg b
 oundary may have been due to influx of impact-generated nitric acid\, foll
 owed by rapid oceanic buffering\, and have been a factor in the massive ex
 tinction of pelagic calcifyers\, ammonites and top-level predators\, while
  oceanic productivity in terms of biomass recovered rapidly. Acidification
  at the end of the Paleocene was triggered by the much slower injection of
  a large mass of carbon-compounds into the atmosphere and transfer into th
 e oceans\, leading to severe extinction of deep-sea calcifying benthos\, m
 uch less severe turnover in the plankton. The study of the biogeography of
  biotic effects of events at the K/Pg and P/E boundaries thus may assist i
 n the evaluation of the varying effects on oceanic biota with varying rate
 s and sources of acidification.
LOCATION:Harker Room 1\, Department of Earth Sciences
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