Ocean Acidification: The other CO2 problemWhat are the impacts on biology and biodiversity?

Rob Dunbar, Stanford University Center for Ocean Solutions

dunbar@stanford.edu http://dunbar.stanford.edu

Impacts on Marine Life

1)Direct effects on carbonate producersDissolution of shells and skeletonsIncreased energy demand to build & maintain shellsLoss of carbonate reefsDecreased biodiversity

2) Effects on many other organismsPhysiological sensitivitiesAcidosis, reduced metabolism, torporReduced oxygen uptakeReduced reproductive successCompromised immune systemLoss of Biodiversity

(Fabry et al. 2008 for review)

(Simon Wright, Australian Antarctic Division)

Pristine Coccosphere of E. Huxleyi E. Huxleyi cultured in Southern Ocean under elevated pCO2

Independent groups have now grown marine nanoalgae at elevated CO2 levels. Sometimes the “shells” get larger but they always show defects.

(Riebesell et al., 2000; Zondervan et al., 2002; Wright, 2006; Barcelos e Ramos,2009; Iglesias-Rodrigues et al., 2008, and others)

Effect of CO2 on Sea Urchin Survival

Post-Experiment Urchin Condition

CO2 Pool Control

Urchins in cage near CO2 pool

Barry et al. 2003, 2004

Jim Barry (MBARI) shows that elevated CO2 levels are lethal to sea urchins in the deep sea. At ph ~ 0.7, spines dissolve. Other studies show decline in reproductive success.

5 10 15 20Millions of Years Ago

Tripati et al., 2009

Today (387 ppmv)

5 10 15 20Millions of Years Ago

Tripati et al., 2009

Today (387 ppmv)

2030? (450 ppmv)

LM of the diatom Asteromphalus sp.Image: Fiona Scott

An example of impacts on non-carbonate organisms:

Threats to the base of the food chain in the Southern Ocean

Diatoms – the most important primary producer in the seas around Antarctica

In cold waters, carbon chemistry dictates that increasing CO2 levels have a greater impact on ocean acidity than in warm waters.

380 ppm CO2

800 ppm CO2

Tortell et al., 2009; Feng et al., 2009; Rose et al., 2009

Highly reproducible experiments using chemostats in Antarctic waters show major changes in relative abundances of marine plants at higher CO2 levels.

Feely et al; Gilmer & Harbison, 2004

Pteropods (small marine snails), a major member of the Antarctic plankton, are affected as well. Multiple impacts near base of food chain lead to biodiversity loss in polar food webs.

“The prospect of ocean acidification is potentially the most serious of all predicted outcomes of anthropogenic CO2

increase.”- J.E.N. Veron, 9/08