Ocean dead zones more deadly for marine life than previously predicted

Stony Brook University Newsroom: Ocean dead zones – regions with levels of oxygen too low to sustain marine life - have grown to become a common feature of coastal regions around the world.  A new study published in the January 8 issue of PLOS One by Christopher Gobler, Professor in the School of Marine & Atmospheric Sciences at Stony Brook University and colleagues, has found that low pH levels within these regions represent an additional, previously unappreciated, threat to ocean animals.

For decades, marine biologists have investigated the effects of low oxygen on marine life without considering pH levels. In reality, low oxygen waters are also acidified waters, but studies investigating how these two conditions affect marine life together have been lacking.

In a series of experiments on young bay scallops and hard clams, marine organisms of significant economic and ecological value, the investigators found that the combined effects of low oxygen and low pH led to higher rates of death and slower growth than by either individual factor.  Further, in some cases there was negative synergy between these environmental factors, which means that the performance of the animals was worse than predicted by either individual factor.

The paper, Hypoxia and acidification have additive and synergistic negative effects on the growth, survival, and metamorphosis of early life stage bivalves, written by Gobler, SoMAS Prof. Hannes Baumann, and Stony Brook graduate students, Elizabeth Depasquale and Andrew Griffith, has important implications for climate change as well.

“Low oxygen zones in coastal and open ocean ecosystems have expanded in recent decades, a trend that will accelerate with climatic warming,” said Gobler. “There is growing recognition that low oxygen regions of the ocean are also acidified, a condition that will intensify with rising levels of atmospheric CO2 due to the burning of fossil fuels causing ocean acidification. Hence, the low oxygen, low pH conditions used in this study will be increasingly common in the World’s Oceans in the future.”...

Image by NOAA Photo Library: fish4524, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license