A huge population of snow crabs across eastern Bering Sea apparently vanished due to an aquatic heat wave that hit back in 2018 and 2019. This intense wave of heat exponentially grew the caloric needs of these creatures and eventually made them starve to death.
Deadly Heat Wave Drives Over 10 Billion Snow Crabs to Starvation and Death
The intense wave of heat hit polar waters in between Siberia and Alaska in 2018. It went on for two years and led to record-high temperatures in the ocean and historic drops in sea ice.
It was these circumstances that brought snow crab populations in the eastern Bering Sea to their knees, according to a new study that looked into the phenomenon.
The researchers explain that the snow crab population collapse was an intense reaction to the aquatic heatwave. The warming ocean temperatures did not directly lead these creatures to succumb. Rather than that, the snow crabs apparently died due to starvation.
Dramatic Drop of Snow Crabs
These round-shelled and tiny crustaceans have a lifespan of up to 20 years. They typically live on seabed that are soft and that are less than 200 meters deep. Because of its seafood commercial value, snow crabs in the eastern Bering Sea are closely managed and monitored.
Dramatic drops in snow crab populations were first observed by scientists when they conducted a survey in 2021. The survey found that the number of snow crabs in the eastern Bering shelf is the fewest since the start of the survey back in 1975.
Due to the COVID-19 pandemic, no survey was performed in the year 2020. Because of this, scientists only observed the disappearance of the crabs in the next year. However, until this new study, the reason behind the collapse of their population had remained unclear.
It appears that the heat wave caused warming temperatures in the water that may have affected the crabs' metabolism and, in turn, boosted their need for calories. According to an earlier lab study, the energy requirements of these creatures doubled when the temperatures of water went up from 32 to 37.4 degrees Fahrenheit.
This temperature jump matches the changes that juvenile snow crabs experienced back in 2017 to 2018. These creatures typically dwell in the cold pool and then move to warmer spots as they grow older.
The heightened caloric needs of these creatures were reflected by body size changes from 2017 to 2018.
Snow crabs were also a victim of timing. When the heat wave struck, their population was actually booming. However, the mix of higher caloric needs and higher crab concentration appeared to be a deadly combination.
There were other factors, including predation by Pacific cod, cannibalism, disease, and fishing, that could have also affected mortality. However, according to the researchers, population density and temperature changes were the key drivers in their recent collapse.
The researchers note how the die-off of these snow crabs serve as a prime example of how a population's outlook can quickly change, especially in light of the pressing challenges that come with climate change.
The population of these creatures in the eastern Bering Sea is still uncertain, as they have not yet reached recovery. Nevertheless, these creatures could make their habitats in northern cold waters.
How the widespread death of these creatures could affect the larger ecosystem still remains a mystery.
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