Ocean Acidification as a Hearing Aid for Fish?
New study shows that the effects of changing ocean pH may result in a significant increase in the hearing sensitivity of fish
April 18, 2013
Micro-CT imagery of a cobia larva head that has been filtered to view the entire skull (top image) and the more dense otolith (ear stone) structures (bottom image). Similar 3D images were used by researchers to obtain the first measurements larval fish otoliths while still inside the skull.
MIAMI – April 18, 2013 – Ocean acidification, which occurs as CO2 is absorbed by the world's oceans, is known to negatively impact a wide variety of marine animals ranging from massive corals to microscopic plankton. However, there is much less information about how fish may be impacted by acidification, should carbon emissions continue to rise as a result of human activities.
In a new study published in the Proceedings of the National Academy of Sciences USA, University of Miami (UM) Rosenstiel School of Marine & Atmospheric Science researcher Sean Bignami, along with National Oceanic and Atmospheric Administration (NOAA) scientists Ian Enochs, Derek Manzello, and UM Professors Su Sponaugle and Robert Cowen, report stunning new insight into the potential effects of acidification on the sensory function of larval cobia (Rachycentron canandum). Cobia are large tropical fish that are highly mobile as they mature and are popular among recreational anglers.
Bignami and the team utilized 3D X-rays (micro-CT scans) similar to what a patient might receive at a hospital to determine that fish raised in low-pH seawater, simulating future conditions, have larger and more dense otoliths (ear stones) than those from higher-pH seawater. Otoliths are distinct calcium carbonate structures within the inner ear of fishes that are used for hearing and balance. The changes resulted in up to a 58-percent increase in otolith mass, and when tested in a mathematical model of otolith function, showed a potential increase in hearing sensitivity and up to a 50-percent increase in hearing range.
"Increased hearing sensitivity could improve a fish's ability to use sound for navigation, predator avoidance, and communication. However, it could also increase their sensitivity to common background noises, which may disrupt the detection of more useful auditory information," said Bignami, who recently completed his PhD in Marine Biology and Fisheries at UM.
The study, a collaboration between UM and NOAA's Ocean Acidification Program at the Atlantic Oceanographic and Meteorological Laboratory in Miami, is the first to use micro-CT technology to examine otoliths while still inside the heads of the larval fish.
"This effect of ocean acidification represents a significant change to a key sensory system in fish. Although the ultimate ecological consequences still need to be determined, there is the potential for serious impact on important processes such as larval fish recruitment and fisheries replenishment in this species and perhaps other critical fisheries," Bignami added.
Article: Bignami S, Enochs I, Manzello D, Sponaugle S, Cowen RK (2013) Ocean acidification alters the otoliths of a pan-tropical fish species with implications for sensory function. Proceedings of the National Academy of Sciences USA. doi:10.1073/pnas.1301365110
About the University of Miami's Rosenstiel School
The University of Miami is the largest private research institution in the southeastern United States. The University's mission is to provide quality education, attract and retain outstanding students, support the faculty and their research, and build an endowment for University initiatives. Founded in the 1940's, the Rosenstiel School of Marine & Atmospheric Science has grown into one of the world's premier marine and atmospheric research institutions. Offering dynamic interdisciplinary academics, the Rosenstiel School is dedicated to helping communities to better understand the planet, participating in the establishment of environmental policies, and aiding in the improvement of society and quality of life. For more information, please visit www.rsmas.miami.edu.