A combination of elevated carbon dioxide levels and an increase in ocean water temperature, both of which are factors associated with climate change, has a significant impact on survival and development in certain Antarctic fish species, a new study has shown.
Scientists at University of California Davis and San Francisco State University assessed the effects of near-future ocean warming and acidification on early embryos of the naked dragonfish (Gymnodraco acuticeps) through measuring the response of warming and increased pCO2 (partial pressure of carbon dioxide) in the developing fish. It has long been understood that polar organisms are vulnerable to climate change specifically because of their adaptation to historically stable thermal regions, however with the speed at which the poles are currently changing, this area of research is likely to grow in order to understand how these species could be affected by climate change.
This study, published in the journal Conservation Physiology, was achieved through measuring the survival and metabolism of dragonfish embryos over time in two different temperatures and three pCO2 levels over a three-week period, which allowed the researchers to assess potential vulnerability of developing dragonfish to future ocean scenarios.
The researchers initially found that in the presence of increased pCO2 alone, embryonic mortality didn’t increase, with greatest overall survival observed at the highest pCO2 levels. In addition, embryos were significantly more likely to have reached a later developmental stage by 3 weeks at a high pCO2 compared to at ambient pCO2.
It was only when combined with increased water temperatures (as would be expected in near-future ocean warming) that the researchers observed a decrease in survival of the dragonfish embryos as well as them developing at a slower rate. These findings suggest that developing dragonfish are more sensitive to ocean warming and may experience negative physiological effects of ocean acidification only in the presence of an increased temperature. The research is also significant in that it shows that single stressors alone may not be sufficient to predict the effects on early development of fish, as the negative effects of increased pCO2 may only manifest at increased temperatures.
One of the article’s authors, Assistant Professor Anne Todgham, explained that “temperature will probably be the main driver of change, but increases in pCO2 will also alter embryonic physiology, with responses dependent on water temperature.“
Professor Todgham went on to say: “Dragonfish embryos exhibited a synergistic increase in mortality when elevated temperature was coupled with increased pCO2 over the course of the three week experiment. While we predictably found that temperature increased embryonic development, altered development due to increased pCO2 was unexpected.“
The team’s findings also indicate that, in addition to reduced hatching success, alterations in development and metabolism due to ocean warming and acidification could have negative ecological consequences owing to changes in phenology (i.e. early hatching) in the highly seasonal Antarctic ecosystem.
Header photo credit:
An Antarctic dragonfish (Gymnodraco acuticeps). Credit: Rob Robbins, US Antarctic Program
Ocean acidification exerts negative effects during warming conditions in a developing Antarctic fish’ Erin E. Flynn, Britanny E. Bjelde, Nathan A. Miller, and Anne E. Todgham, Conservation Physiology, DOI: 10.1093/conphys/cov033