Could it be possible that the animals just moved on to other areas? I believe, this was not investigated.
When scientists long for a "pristine environment"! Whatever that is or means for the inhabited planet Earth! Clearly indicates bias! Was the Earth pristine before the appearance of Homo sapiens?
The language used by the authors strongly suggest bias and that they knew the answer before they started their research!
Notice also the Deepwater Horizon oil spill is an educated guess by these authors not verified fact!
"Like other oil spills, the 2010 Deepwater Horizon disaster killed untold numbers of seabirds, shallow-water fish, and other sea life. Now, scientists report that the spill also likely caused major carnage at depth: A 13-year survey, begun the year after the spill, has discovered a steep, sustained decline in fish, crustaceans, and cephalopods in the deep waters of the Gulf of Mexico. ..."
From the significance and abstract:
"Significance
It is becoming increasingly difficult to find a pristine environment on Earth [???]. In a vertical sense, remoteness from human activity typically confers ecological integrity, be it high (mountains) or low (deep sea). The latter would also ostensibly benefit from the pollution-dilution effect afforded by its size; the deep-pelagic biome is larger than all other ecosystems combined.
Here, we show a severe decline in the abundance of deep-pelagic fishes, crustaceans, and cephalopods in an oceanic ecosystem.
Available evidence rules out natural phenomena [???] as likely drivers, suggesting a large-scale pollution event [???] and its associated mitigation measures most likely precipitated the declines. Events such as this, coupled with Allee effects, may result in long or potentially irreversible ecosystem shifts in Earth’s largest ecosystems.
Abstract
The deep-pelagic habitat of the Gulf of Mexico comprises 90.4% of its volume and houses an exceptionally diverse deep-pelagic animal community that provides numerous ecosystem services, including carbon cycling and prey provisioning for oceanic predators.
Here, we report sudden, severe, and persistent declines in the abundance of deep-pelagic fishes, crustaceans, and cephalopods that have persisted for over a decade.
Over a 3.5-y period, animal abundances declined by 60 to 85%, taxon depending. Particularly hard-hit were ecologically foundational taxa such as euphausiids and lanternfishes. The magnitude of population-level decline that occurred during this 3.5-y period was greater than any observed over a 60-y period in the California Current system, the only comparable dataset, making this the fastest and most severe faunal decline reported for Earth’s largest ecosystem type.
These declines were detected both via direct sampling and acoustic sensing, providing independent corroboration.
Genomic analyses indicate reductions in genetic diversity among dominant taxa, both a corroboration and a consequence of the decline. Furthermore, resource managers report that these trends parallel those of managed or protected Gulf species that are dependent on deep-pelagic prey, including endangered species (e.g., beaked whales, Rice’s whale).
No naturally occurring factors (e.g., temperature, oxygen, food supply) correlated with the observed declines, suggesting an anthropogenic proximate cause.
That the declines began shortly after the Deepwater Horizon oil spill points to that event as the most parsimonious explanation. These findings suggest that despite its immense size the deep-pelagic biome is vulnerable to human-induced disturbance and possesses limited resilience to facilitate recovery."
ScienceAdviser
Fig. 5. Stations sampled between 2011 and 2023 in the Gulf of Mexico.
Symbol colors represent the time periods of sampling [blue = 2011 (before decline); red = 2015–2023 (during and after decline)]. Numbers within symbols indicate the number of research cruises conducted at that station. The 200-m, 500-m, 1,000-m, 2,000-m, and 3,000-m isobaths are indicated by continuous white lines. The Deepwater Horizon site is indicated by a star, Standard Station by a square.
