MH370 in an Iconic Deep-sea Ecosystem

(In the image: note that the Penang-Longitude Hole ("PL Hole Target") is approximately at 33oS and 100oE; and the width of the EBR protected area is approximately 80 km.)

I describe the iconic very deep Hadal Zone environment in the southern Indian Ocean where MH370 is most likely located.

?To enhance our knowledge and understanding of biological life at the depth where MH370 is most likely located, I did a short review of major discoveries of deep-ocean species and communities of the Hadal Zone. The Hadal Zone, at ocean depths of 6,000–11,000 m, hosts unique ecosystems which researchers attribute to three key variables: extreme depth/pressure, limited food supply, and diverse topographic features like trenches, deep holes, and steep slopes.

?I recently also spoke to Dr. Peter “Scary” Last, an internationally-renowned colleague from CSIRO whom I worked with, along with many of Australia’s fish taxonomists, to pioneer (since 1995) construction of what is now known as the “Fish Atlas of Australia”. This globally-unique Atlas underlies the characterization of Australia’s bioregions and forms the basis of Australia’s offshore marine protected areas and descriptions of its ecosystems. Dr. Last assured me that, contrary to expectations that species below the Calcite Compensation Depth (~4500 m) would lack bony structure, there are some which also have teeth. However, the adaptations with respect to bone density and depth “is complex and likely tied to a range of behavioral, environmental, and life history factors.” according to Martin et al. (2022). Notwithstanding these complex adaptations in deep-sea animals, the default expectation is still one of dissolution of non-deep-sea calcite structures.

?New deep-sea discoveries also illustrate how organisms are highly adapted to these variables and thrive in one of Earth’s most unimaginably hostile environments. For further fascinating information collected during the HADES expeditions, see: https://web.whoi.edu/hades/about-hades/

?Depth/Pressure

• Pressure Increases: Up to 1,100 atmospheres at the greatest depths.
• Adaptations: Organisms show flexible skeletal systems, pressure-tolerant enzymes, and specialized cellular structures to maintain function.

?Food Supply

• Marine Snow: Organic detritus sinking from surface waters forms the primary food source.
• Carcass Falls: Whale falls and other large organic material provide nutrient-rich "oases."
• Patchy Availability: Food scarcity leads to efficient opportunistic feeding strategies.

?Topographic Morphology

• Trenches: Create isolated ecosystems that encourage speciation.
• Slopes: Gradual depths with moderate food availability.
• Sediment Variability: Shapes benthic community structure.

Major species and their adaptations are summarized in the following Table.

MH370 is located within a deep-trench environment at the intersection where Broken Ridge collides with the Diamantina Fracture Zone. This location contains the second-deepest hole in the Indian Ocean known as the Dordrecht Deep at a depth of 7,079 m (see: https://en.wikipedia.org/wiki/Dordrecht_Deep), about 120 km south-east of where MH370 is presumed located in the Penang-Longitude Hole (~6000 m). It is reasonable to assume that this location which is highly energetic oceanographically is also highly productive as it supports high-seas fisheries.

?An ecologically unique voluntary Benthic Protected Area (BPA) has been established by the SIODFA (Southern Indian Ocean Deepwater Fisheries Association), called the East Broken Ridge BPA (~5000 km2), which encloses a seamount that rises up to about 1000 m. As shown in the image, this BPA (of about 80 km width) is just to the east of the Penang-Longitude Hole; further details can be found at:

https://siofa.org/sites/default/files/documents/meetings/SC-01-INFO-15%2520-%2520SIODFA%2520Benthic%2520Protected%2520Areas.pdf

?Isolation in this unique environment should also lead to the evolution of endemic species and community assemblages which can be summarized as:

?Community Assemblages

• Scavenger Guilds: Amphipods and grenadiers dominate food falls, with amphipods swarming carcasses and grenadiers acting as top scavengers.
• Predators: Predatory snailfish and cusk eels occupy niches with limited competition due to extreme conditions.
• Deposit Feeders: Holothurians and polychaete worms consume organic detritus from sediment-rich trench floors.
• Opportunistic Species: Many species alternate between predation and scavenging depending on food availability.

?As examples, the following are documented for some of the deepest trenches:

• Mariana Trench: World’s deepest fish (Pseudoliparis belyaevi) recorded at 8,336 m. Amphipod species adapted to pressure with high levels of osmolytes.
• Kermadec Trench: High diversity of amphipods and holothurians.
• Japan Trench: Unique snailfish species displaying localized adaptations.

Conclusion

MH370 is most likely located at the top of an iconic and unique Hadal ecosystem of the Indian Ocean whose communities will be shaped by depth, food supply, and topography. It is most likely a biologically active and biodiversity-rich hotspot located just to the west of a designated and ecologically unique environment: the East Broken Ridge voluntary Benthic Protected Area. We can expect to find a rich range of species from cartilage-based predators (e.g., snailfish) to scavenging amphipods and deposit feeders.

If MH370 is found at the suggested location, consideration should be given to extending the EBR protected area to enclose that location

Reference

Martin, R.P., Dias, A.S., Summers, A.P., & Gerringer, M.E. (2022). Bone Density Variation in Rattails (Macrouridae, Gadiformes): Buoyancy, Depth, Body Size, and Feeding. Integrative Organismal Biology, 4, obac044