In October a story came to light that had taken place in 2014. An MIT investigation had managed to trace an unparalleled event under the sea: the largest species kill in the ocean with the death of millions of creatures. Something similar happened a few hours ago, but the “killer” in this case has little to do with animal fauna, although is a usual suspect.
A heat wave. Between 2014 and 2016, an unprecedented marine heat wave known as “Blob” dramatically raised temperatures in the northeast Pacific, triggering a catastrophic chain reaction in the marine ecosystem.
Now we know through a new study published in Science that this phenomenon has resulted in the mass death of 4 million common murres (Uria aalge), a loss equivalent to half the population of this species in the Gulf of Alaska and the Bering Sea (a quarter of its global population), and which marked the largest mortality event of non-fish vertebrates in the modern era.
Blob Impact. As the researchers say, the tremendous heat wave profoundly affected the marine food chainreducing phytoplankton populations and, consequently, essential forage fish for seabirds such as guillemots. Between 2015 and 2016these birds died of starvation in large numbers, with 62,000 carcasses found on beaches from Alaska to California, and an estimated mortality reaching 10 billion snow crabs in the Bering Sea.
Key populations such as Pacific cod and humpback whales also experienced significant declineswhile other species remained neutral or even thrived, revealing the very complexities of these climatic perturbations. There is no doubt, the speed and magnitude of this population collapse are shocking and suggest fundamental changes in the ecosystem that make recovery difficult.
A system in crisis. The macro study, based on 14 years of monitoring murre colonies in the Gulf of Alaska and the Bering Sea, documents a decrease of between 52% and 78% in the populations of these birds since the event. Guillemots, which form dense colonies of hundreds of thousands of individuals, are now showing drastically reduced numbers with no signs of recovery.
And it is not an isolated phenomenon. As the researchers remember in their work, it is a warning of the systemic effects of climate change in the oceans, with marine heat waves projected to be more frequent and intense.
Challenge for conservation. In this regard, researchers such as Heather Renner and Brie Drummond highlight that Events like Blob reflect the direct impact of global warming on biodiversity and in coastal communities that depend on productive marine ecosystems, exacerbating stress on already weakened ecosystems.
Although common murres are not at immediate risk of extinction, their drastic decline is a reminder of the fragility of marine systems and the urgency of adapting to these new conditions. For Megan Williamsfrom the Ocean Conservancy, ecosystems like the Bering Sea cannot be expected to remain as productive as they have been in the past 50 years.
Ultimately, although it is difficult to control marine heat waves directly, the findings underline the need for complementary conservation measures, such as the elimination of invasive predators or the mitigation of other pressures on seabird populations. As experts emphasize, the collapse of these key species should be a global alarm signal about the increasingly severe impacts of the repetitive usual suspect.
Image | Pexels