Finding Nemo: Clownfish, Sharks and Ocean Acidification

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​When humans burn fossil fuels, greenhouse gasses including carbon dioxide (CO₂), are released into the atmosphere.  Nearly half of the added atmospheric CO₂ is absorbed into the oceans, which cause the acidification of the ocean waters - termed ocean acidification.  Concern that ocean acidification will severely impact the biodiversity of marine ecosystems has escalated.  Average ocean pH has already declined by 0.1 units since pre-industrial times, and is predicted to fall another 0.3 - 0.4 units by 2100.  Scientists were initially most concerned about the effects of ocean acidification on calcifying organisms.  A range of impacts, including the dissolution of calcifying plankton, and a declining growth rate in reef-building corals have been documented.  However, it was not until more recently that the impacts ocean acidification have on fish were assessed.  Experiments have shown that the behavior of fish can be seriously affected by projected future CO₂ concentrations.  Documented impacts range from the iconic clownfish unable to process information from chemical cues important in the identification of their host sea anemones, to temperate sharks unable to properly track prey.  Whether​ fish can acclimate to elevated CO₂ over the longer term, and the consequences of altered behavior on the structure of fish communities remains unknown.  However, evidence from natural volcanic CO₂ seep reefs demonstrate the same behavioral abnormalities as shown with laboratory experiments.  If fish behavior does not adapt to rising CO₂ levels over coming generations, there could be serious consequences for the structure and function of future marine communities.

​​Danielle Dixson

Assistant Professor, Marine Science and Policy      

Danielle Dixson is an Assistant Professor in the school of Marine Science and Policy within the College of Earth, Ocean and the Environment at the University of Delaware. She is a behavioral ecologists with a focus on how human induced changes, such as ocean acidification, pollution and habitat degradation will impact animal behavior. Her work is conducted primarily on the coral reefs of Belize, Fiji, Australia and Papua New Guinea, however she has recently started projects investigating the temperate species native to the Delaware coast.  Most recently, she is leading a study funded by the Gordon and Betty Moore Foundation to investigate the sensory cues used by Belizean coral reef animals to choose a coral reef.

Danielle Dixson, UD Profile

The Dixson Lab