The elevated carbon dioxide levels expected to be found in the world’s oceans by 2100 will likely lead to physiological impairments of jumbo (or Humboldt) squid, according to research by two University of Rhode Island scientists.
The results of a study by Brad Seibel, URI assistant professor of biological sciences, and Rui Rosa, a former URI post-doctoral student now on the faculty at the University of Lisbon, Portugal, was recently reported in the Proceedings of the National Academy of Sciences.
The researchers subjected the squids (Dosidicus gigas) to elevated concentrations of CO2 equivalent to those likely to be found in the oceans in 100 years due to anthropogenic emissions. They found that the squid’s routine oxygen consumption rate was reduced under these conditions, and their activity levels declined, presumably enough to have an effect on their feeding behavior.
Jumbo squid are an important predator in the eastern Pacific Ocean, and they are a large component of the diet of marine mammals, seabirds and fish.
According to Seibel, jumbo squid migrate between warm surface waters at night where CO2 levels are increasing and deeper waters during the daytime where oxygen levels are extremely low.
“Squids suppress their metabolism during their daytime foray into hypoxia, but they recover in well-oxygenated surface waters at night,” he said. “If this low oxygen layer expands into shallower waters, the squids will be forced to retreat to even shallower depths to recover. However, warming temperatures and increasing CO2 levels may prevent this. The band of habitable depths during the night may become too narrow.”
Carbon dioxide enters the ocean via passive diffusion from the atmosphere in a process called ocean acidification. This phenomenon has received considerable attention in recent years for its effects on calcifying organisms, such as corals and shelled mollusks, but the study by Seibel and Rosa is one of the first to show a direct physiological effect in a non-calcifying species.
Science Daily, 15 December 2008. Full article.