With the effects of climate change going up throughout the day, scientists are studying the ways in which human behavior contributes to the damage. A recent study at Walla Walla University, in collaboration with researchers from Walla Walla University and La Sierra University, examined the effects of acid water on octopuses, which may offer a new perspective on both as that our actions affect the world around us, and thus a changing world in response.
The study, “The Impact of Short- and Long-Term Exposure on Elevated Seawater PCO2 on Metabolic Level and Hypoxia Tolerance in Octopus rubescens, ”he focused on the metabolic rate of octopuses exposed to acidified by carbon dioxide, and the changes it made to the animals.2 This is a key indicator of the growing acidity of our oceans as much of the gas released into the air by humans melts into the seawater.
The first work in the field focused on the negative effects of ocean acidity: weak growth of affected species such as magnifying crabs, for example, or lower survival rates of fish species over time. Fitness, however, has not received so much attention, especially when it comes to octopuses and other cephalopods. The studies conducted showed conflicting results, especially when it comes to short-term vs long-term increased ocean acidity (OA).
For example, studies on shellfish do not show any significant change in their metabolism after being exposed to more OA, while squid under the same conditions showed a decrease in aerobic metabolism, which ‘showed less oxygen circulation in the subjects.
For the purposes of this experiment, researchers used octopus rubescens a small species of octopus that is common on the west coast of North America. The subjects were open to more CO2-activity of acid for a period of 5 weeks. Researchers measured their normal metabolic rate (RMR) without any prediction of the acidic water, and then again at 1 week and at 5 weeks. The subjects’ critical oxygen pressure was also measured at 5 weeks.
Metabolic levels are well-reported in such a situation because the most important physiological changes – such as smaller organs or smaller growths – are reflected in the movement in metabolism. (Changes in biology are largely changes in energy use, which can be seen by monitoring metabolism.)
The results showed a remarkable degree of flexibility in the subjects, as well as possible reasons for data differentiation in other experiments. The subjects experienced high levels of metabolic change within the first 24 hours since increased acidity: deviation from earlier studies on various cephalopods, which showed a decrease in metabolic change.
However, when the same subjects were assessed after a week, their RMR had returned to normal. The normal readings remained after 5 weeks as well, although their ability to function at low oxygen levels suffered due to increased acidity.
The findings show that octopuses may be better able to withstand changes in marine acidity levels, which may have a long-term impact on our understanding of climate change. It also marks the first study to compare the long-term and short-term effects of excess acid. Further research is needed to clarify the mechanism driving the change in RMR, but the experimental parameters – and the use of octopus rubescens as test subjects – provide an excellent modeling system for study of the effect of OA on cephalopods.
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