Decreased oxygen levels could pose threat to marine species

Decreased oxygen levels could pose threat to marine species
The prevalence of low oxygen areas in coastal waters is predicted to increase in the future in both scale and duration.

According to research published in Nature Scientific Reports, marine species living in coastal regions could face a significant future threat from reduced levels of oxygen in the marine environment.

The prevalence of low oxygen areas in coastal waters is predicted to increase in the future in both scale and duration. However, while it is understood that adults of many marine species can cope with short periods of hypoxia (low oxygen), it is unclear whether that ability is present if animals are bred and reared under chronic hypoxia.

A study by the University of Plymouth, UK, showed that exposure to even moderate hypoxia can have distinctly different effects on metabolic performance, depending on whether adults are exposed to short-term hypoxia or undergo the whole of their development under hypoxic conditions.

What does the research demonstrate?

Researchers warn that differing reactions could result in the number of vulnerable marine species in an affected region currently being underestimated, and ultimately lead to vastly reduced biodiversity.

Lecturer in marine molecular biology Dr Manuela Truebano said: “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. Most studies to date focus on short-term responses observed in adults and, based on these, many estuarine species are currently considered hypoxia-tolerant.”

For the study, scientists focused on the brackishwater Gammarus chevreuxi, which as an amphipod is a pervasive and ecologically important group found throughout the marine environment from the poles to the tropics.

Researchers exposed both adults and young to the reduced levels of oxygen typically and periodically found in coastal regions for one week and monitored their varying responses.

Adults collected from the wild and tested under laboratory conditions maintained their levels of oxygen uptake when exposed to moderate hypoxia for one week. However, the offspring of these adults, when raised in hypoxic conditions, showed less ability to regulate their oxygen uptake.

From this the scientists deduced that short-term acclimation ability observed in adults after one week does not predict the ability of their offspring to cope with low oxygen, if reared under moderate hypoxia.

What is hypoxia?

  • Hypoxia means low levels of oxygen – combined with ocean warming and acidification, these global drivers are threatening marine biodiversity; and
  • It can lead to reduced growth and reproduction of animals, and impairs ecosystems.

Source: University of Plymouth

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