“Ocean Acidification”, a new book to be published by Oxford University Press

Ocean Acidification
Edited by Jean-Pierre Gattuso and Lina Hansson
344 pages | 75 illustrations | 246×189 mm
Publication date: September 2011

About this book

• Synthesizes the findings of recent national and international research efforts, including those of EPOCA (European Project on Ocean Acidification), set in a broader global context
• Reviews our current knowledge of the chemical, biological, biogeochemical, and societal implications of ocean acidification, with a particular emphasis on its impact on marine organisms and ecosystems
• Assesses the uncertainties, risks, and thresholds related to ocean acidification at molecular, cellular, organismal, local, and global scales

Trajectories of Late Permian – Jurassic radiolarian extinction rates: no evidence for an end-Triassic mass extinction

The hypothesis that ocean acidification was a proximate trigger of the marine end-Triassic mass extinction rests on the assumption that taxa that strongly invest in the secretion of calcium-carbonate skeletons were significantly more affected by the crisis than other taxa. An argument against this hypothesis is the great extinction toll of radiolarians that has been reported from work on local sections. Radiolarians have siliceous tests and thus should be less affected by ocean acidification. We compiled taxonomically vetted occurrences of late Permian and Mesozoic radiolarians and analyzed extinction dynamics of radiolarian genera. Although extinction rates were high at the end of the Triassic, there is no evidence for a mass extinction in radiolarians but rather significantly higher background extinction in the Triassic than in the Jurassic. Although the causes for this decline in background extinction levels remain unclear, the lack of a major evolutionary response to the end-Triassic event, gives support for the hypothesis that ocean acidification was involved in the dramatic extinctions of many calcifying taxa.

Simulating the biogeochemical effects of volcanic CO2 degassing on the oxygen-state of the deep ocean during the Cenomanian/Turonian Anoxic Event (OAE2)

Cretaceous anoxic events may have been triggered by massive volcanic CO2 degassing as large igneous provinces (LIPs) were emplaced on the seafloor. Here, we present a comprehensive modeling study to decipher the marine biogeochemical consequences of enhanced volcanic CO2 emissions. A biogeochemical box model has been developed for transient model runs with time-dependent volcanic CO2 forcing. The box model considers continental weathering processes, marine export production, degradation processes in the water column, the rain of particles to the seafloor, benthic fluxes of dissolved species across the seabed, and burial of particulates in marine sediments. The ocean is represented by twenty-seven boxes. To estimate horizontal and vertical fluxes between boxes, a coupled ocean–atmosphere general circulation model (AOGCM) is run to derive the circulation patterns of the global ocean under Late Cretaceous boundary conditions. The AOGCM modeling predicts a strong thermohaline circulation and intense ventilation in the Late Cretaceous oceans under high pCO2 values. With an appropriate choice of parameter values such as the continental input of phosphorus, the model produces ocean anoxia at low to mid latitudes and changes in marine δ13C that are consistent with geological data such as the well established δ13C curve. The spread of anoxia is supported by an increase in riverine phosphorus fluxes under high pCO2 and a decrease in phosphorus burial efficiency in marine sediments under low oxygen conditions in ambient bottom waters. Here, we suggest that an additional mechanism might contribute to anoxia, an increase in the C:P ratio of marine plankton which is induced by high pCO2 values. According to our AOGCM model results, an intensively ventilated Cretaceous ocean turns anoxic only if the C:P ratio of marine organic particles exported into the deep ocean is allowed to increase under high pCO2 conditions. Being aware of the uncertainties such as diagenesis, this modeling study implies that potential changes in Redfield ratios might be a strong feedback mechanism to attain ocean anoxia via enhanced CO2 emissions. The formation of C-enriched marine organic matter may also explain the frequent occurrence of global anoxia during other geological periods characterized by high pCO2 values.

NOAA’s ocean acidification data-in-the-classroom module

Ocean acidification is a topic of growing concern for the world’s coral reef and other marine calcifiers. This web seminar will provide a brief science overview ocean acidification, its impacts to marine life, and provide new in-depth tools to teach it in the classroom. We will introduce the new NOAA Data-in-the-Classroom Module on ocean acidification, consisting of five scalable lesson plans, aimed for High School science educators, based on increased levels of student engagement and interaction, plus classroom demos to showcase simple concepts behind ocean acidification. Register Today!

EGU Today – Daily column

by Jean-Pierre Gattuso

The oceans provide a much valuable service to society by absorbing about one fourth of the CO2 released by humans into the atmosphere, thereby moderating climate change. However, this generates considerable changes in the chemistry of seawater (“ocean acidification”), among which an increase in its acidity. As this century progresses, ocean acidification has the potential to affect a wide range of marine organisms, food webs, habitats and ecosystems that supply important goods and services to humankind. However, the socio-economic consequences of ocean acidification are still unknown and hampered by the poor knowledge of the impacts on an ecosystem scale.