In addition to coral bleaching and rising sea levels, a new factor concerns scientists that may threaten marine life. Hypoxia, a phenomenon characterized by low oxygen levels in marine environment, is believed to pose a possible significant threat to marine life by some scientists. A study published in Scientific Reports predict that the occurrences of hypoxia – in terms of duration and affected area – in coastal regions will increase in the future.
“Along with ocean acidification and rising temperatures, hypoxia is considered one of the main threats to species within the marine environment – but it is currently the least talked about. As the duration and extent of hypoxic areas is predicted to increase in coastal regions, it is likely that some species will be exposed chronically throughout their life cycle,” explained Dr. Manuela Truebano, lead author of the study and a lecturer in Molecular Marine Biology in the University of Plymouth.
While it has been known that the adults of species thriving in the coastal regions can manage short period of hypoxia, it is uncertain whether this ability is also exhibited by marine species that were raised in a chronic hypoxic environment. “Most studies to date focus on short term responses observed in adults and, based on these, many estuarine species are currently considered hypoxia-tolerant,” added Dr. Truebano.
In line with this, the study conducted by Dr. Truebano and Professor John Spicer “…observed a detrimental effect of hypoxia in animals reared under low oxygen, not apparent from observations in short term studies in adults.” The scientists “believe hypoxia will have marked effects on some aquatic invertebrates currently thought of as hypoxia tolerant, based largely on their ability to do well during exposure to periodic hypoxia.”
How was the study conducted? The scientists studied a certain group of amphipods called brackishwater or Gammarus chevreuxi. For one week, both youngsters and adults of this group were exposed to recurring low oxygen levels usually experienced in coastal regions.
The adults were found out to have stable oxygen levels despite the exposure. The youngsters, however, were found to have difficulty in regulating their oxygen levels. This result concerns the scientists that the actual effects of hypoxia might be taken too lightly as current studies are conducted only with adults.
“The observation that these small and seemingly insignificant estuarine animals, reared in hypoxic conditions, become physiologically compromised as adults is a cause of concern for this species. But as a vital part of the food chain, there could be significant knock-on effects for other species as well. Importantly, our study suggests that, by focusing research exclusively on adults, it is likely that we will underestimate the number of species vulnerable to decreasing levels of oxygen in the marine environment.”