Hunting squid reduced by increasing carbon levels

High carbon dioxide levels cause squid to bungle attacks on their prey.

Adult bigfin reef squid, Sepioteuthis lessoniana. Image: Blake Spady
Adult bigfin reef squid, Sepioteuthis lessoniana. Image: Blake Spady

According to a recent study by the James Cook University (JCU) scientists, high carbon dioxide levels make squid fumble assaults on their prey.

Scientists particularly studied cephalopods (a group that includes squid, cuttlefish, and octopuses) as most of the previous studies have focused on fishes, and the effects of elevated CO2 on highly active invertebrates. They tested the effects of elevated CO2 on the hunting behaviors of pygmy squid and bigfin reef squid.

Ph.D. candidate Blake Spady from JCU’s ARC Centre of Excellence said, “The oceans absorb over one-quarter of all the excess carbon dioxide (CO2) released into the atmosphere by humans and this uptake of additional CO2 causes seawater to become more acidic.”

Adult bigfin reef squid, Sepioteuthis lessoniana. Image: Blake Spady
Adult bigfin reef squid, Sepioteuthis lessoniana. Image: Blake Spady

“Climate models project that unless there is a serious commitment to reducing emissions, CO2 levels will continue increasing this century to reach levels that will have far-reaching effects on sea life.”

“Cephalopods also prey on just about anything they can wrap their arms around and are themselves preyed upon by a wide range of predator species, so they occupy an important place within marine food webs.”

Scientists found 20% decrement in the extent of squid that assaulted their prey after the presentation to hoisted CO2 levels. They were likewise slower to assault, assaulted from assisting away, and regularly picked more prominent body design shows at raised CO2 conditions.

reef squid
Image: Blake Spady

Bigfin reef squid showed no difference in the proportion of individuals that attacked prey, but, like the pygmy squid, they were slower to attack and used different body patterns more often.

Mr. Spady said, “Both species showed increased activity at elevated CO2 conditions when they weren’t hunting, which suggests that they could also be adversely altering their ‘energy budgets’.”

Co-author Dr. Sue-Ann Watson said, “Overall, we found similar behavioral effects of elevated CO2 on two separate cephalopod orders that occupy largely distinct niches. This means a variety of cephalopods may be adversely affected by rising CO2 in the oceans, and that could have significant consequences in marine ecosystems.”

reef squid
Image: Blake Spady

According to Mr. Spady, because squid has short lifespans, large populations, and a high rate of population increase, they may have the potential to adapt to rapid changes in the physical environment.

He said, “The fast lifestyle of squid could mean they are more likely to adapt to future ocean conditions than some other marine species, and this is the next question we intend to investigate.”

the study is published in the Journal Global Change Biology.