Picture: for illustration purposes
The mystifying disappearance of roughly 10 billion snow crabs from the Bering Sea over the course of three years has now been explained, thanks to a recent study conducted by the National Oceanic and Atmospheric Administration (NOAA). The unprecedented phenomenon had confounded scientists, but the study published by NOAA researchers in Science reveals that the massive loss of snow crabs - deemed the largest mortality collapse known to the species - was driven by increasing water temperatures.
Lead researcher and fishery biologist at NOAA, Cody Szuwalski, expressed his initial disbelief at the staggering data in 2021, which confirmed the scale of the diminishing snow crab population. Despite hopes that the figures represented an error or that the crabs were simply migrating, the 2022 data reaffirmed the grim reality.
The entity instigating the large-scale die-off was not predatory activity, but rather warmer waters in the Bering Sea. Contrary to initial assumptions that extreme temperatures could have directly resulted in the die-off, the NOAA team discovered that while snow crabs can withstand temperatures of up to 12°C, the resultant metabolic implications prove detrimental.
The water temperature rise initiated by a marine heatwave in 2018, increased the crabs' caloric needs up to four times their regular intake, while competing marine species further raided the crab's food stocks. The culmination of these factors created a resource scarcity that led to a catastrophic collapse in the snow crab population.
Another impact of this marine heatwave was a notable shift in aquatic biodiversity with species such as the Pacific cod, which feed on snow crabs, finding their way into these waters.
The aftermath of these shifting temperature patterns indicate a future threat to marine species with climate change contributing to more such marine heatwaves. Bering Sea, in particular, is one of the regions hardest hit by global warming, experiencing a rate of warming up to four times the global average.
Szuwalksi suggests that the future of the snow crab may lie further north, as the Bering Sea continues to warm and ice coverage continues to shrink.