Using cutting-edge technology, scientists investigated a substantial group of deep-sea octopus congregating near thermal springs close to an inactive underwater volcano off the coast of Central California. The elevated temperature of the hydrothermal springs expedites the growth of octopus embryos, enhancing the survival odds for young octopuses.
Octopus Garden: World's Largest Octopus Aggregation
Dubbed the "Octopus Garden," this is the most extensive known assembly of octopuses globally. In 2018, researchers from NOAA's Monterey Bay National Marine Sanctuary and Nautilus Live discovered the deep-sea site off the Central California coast where over 6,000 octopuses and potentially 20,000 more octopuses nest.
This phenomenon intrigued global audiences, including MBARI scientists. Over three years, MBARI and partners employed advanced tools to study why this area is so attractive to deep-sea octopuses.
A recent study, titled "Abyssal hydrothermal springs-Cryptic incubators for brooding octopus" published in Science Advances, confirmed that octopuses migrate to the garden to mate and nest. The Octopus Garden, the world's largest known octopus aggregation, is warmed by thermal springs, which accelerate egg development, enhancing hatchling survival chances.
Through advanced marine technology and collaborations with local researchers, MBARI closely studied the Octopus Garden, uncovering its appeal to deep-sea octopuses and its potential for informing the protection of similar habitats.
Remotely Operated Submersible Uncovers Mystery of Octopus Garden
At a depth of 3,200 meters (10,500 feet) below the ocean's surface, the Octopus Garden can be found on a small hill adjacent to the base of Davidson Seamount, an inactive underwater volcano situated 130 kilometers (80 miles) southwest of Monterey, California.
In this area, one can encounter Muusoctopus robustus, which MBARI researchers have affectionately dubbed the pearl octopus due to its opalescent pearl-like appearance when nesting from a distance.
Researchers from MBARI and collaborating institutions used advanced underwater technology to comprehensively study the octopus garden. Over a span of three years, the institute's ROV Don Ricketts conducted 14 extended dives to the site, capturing high-definition video footage of the octopuses and meticulously mapping the garden with a meter-scale resolution.
The remotely operated submersible also deployed a time-lapse camera and sensors to monitor temperature and oxygen levels, enabling continuous observations of octopus behavior. This camera recorded an image every 20 minutes, amassing approximately 12,200 images from March to August 2022.
Scientists used collected data to deduce the attraction of octopuses to the site, aided by distinctive markings for tracking individuals and monitoring their offspring's growth. The presence of adult males, females, developing eggs, and hatchlings indicated the site's role as an exclusive breeding and nursery location.
No intermediate-size octopuses or signs of feeding were observed. Hatchlings were seen swimming away, suggesting that they venture elsewhere to begin their lives.
The study revealed unexpectedly rapid hatching of eggs in under two years, contrary to the typical years-long brooding period for deep-sea octopuses. Despite the potential risks of warm water brooding, the advantage lies in shorter brood times, contributing to apparent high hatch rates.
The warmth from thermal springs likely speeds up female octopus metabolism and egg incubation, reducing predation risk, though its necessity remains uncertain. Ongoing research at Davidson Mount will explore this phenomenon further and seek similar conditions for more octopus gardens.
Despite costly deep-sea exploration, understanding these sites continues. Octopuses' self-sacrifice as parents, ceasing to eat and dying after egg-laying, sustains nearby invertebrates. Four deep-sea octopus gardens are documented, two off California's coast and two near Costa Rica.
RELATED ARTICLE: Deep-Sea Octopuses 'Brood' Faster Than We Thought, Exploiting Thermal Energy to Enhance Reproductive Success
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