Solving the Ocean's Decomposition Mystery
The secret world of carcass decomposition in the deep sea holds crucial clues for forensic science.
When a body disappears in the ocean, what happens next remains one of forensic science's greatest mysteries. Unlike terrestrial decomposition, which is well-documented, the fate of remains in marine environments has largely been shrouded in uncertainty—until now. In the deep waters of the Strait of Georgia, British Columbia, a groundbreaking study using pig carcasses as human proxies has revealed a fascinating world of deep-sea scavengers whose feeding habits follow distinct seasonal patterns, providing crucial insights for forensic investigations and ecological understanding 1 .
Every year, countless individuals are lost in the ocean through natural disasters, accidents, and other tragedies 1 . Understanding what happens to their remains is critical for recovery efforts, managing family expectations, and determining postmortem intervals in forensic cases 1 . According to forensic researcher Gail S. Anderson and colleagues, "The taphonomy of carcasses submerged in the ocean is little understood, yet it is extremely important ecologically and forensically" 1 .
The challenges of studying marine decomposition are significant—the environment is inaccessible, expensive to work in, and conditions can change dramatically within just a few meters of depth 1 .
Previous knowledge came primarily from anecdotal reports of drowning victims or studies of enormous whale falls, which can take decades to fully decompose 5 . But human remains are much smaller, creating a critical knowledge gap.
To overcome these challenges, researchers turned to Ocean Networks Canada's Victoria Experimental Network Underseas (VENUS) observatory—a cabled underwater laboratory that provides unprecedented access to the deep sea 1 . This high-tech installation allowed continuous monitoring of decomposition in real-time, something previously impossible with periodic diver visits limited by weather and safety concerns 1 .
Depth
170 meters
Location
Strait of Georgia, BC
Monitoring
Continuous video recording
| Equipment | Function | Research Importance |
|---|---|---|
| VENUS observatory platform | Cabled underwater laboratory with power and fiber optic connections | Enables real-time, continuous monitoring impossible with periodic diver visits |
| Digital webcam (AXIS Q6034) with lighting array | Records high-definition video (720p) of carcasses | Documents scavenger activity and decomposition progression |
| Remotely-operated vehicle (ROV) | Positions and connects equipment on seafloor | Allows precise deployment without endangering human divers |
| CTD instrument | Measures conductivity, temperature, and depth | Correlates environmental conditions with decomposition rates |
| Oxygen optode | Measures dissolved oxygen concentrations | Determines how oxygen levels influence scavenger activity |
The study, conducted in 2014, placed two freshly-killed pig carcasses on the seafloor during both spring (March) and fall (September) 1 . Each season, one carcass was fully exposed while another was protected by widely-spaced bars designed to deter large scavengers like sharks while still allowing arthropod access 1 . This design had proven successful in previous experiments and helped ensure at least one carcass would remain for observation 1 .
Pigs were chosen as human proxies because they:
The results revealed striking differences between spring and fall decomposition, driven primarily by which scavengers arrived first and how they interacted with the carcasses.
In spring, the carcasses were immediately colonized by Lyssianassidae amphipods and spot prawns (Pandalus platyceros) 1 . The amphipods removed the bulk of the soft tissue from the inside while the shrimp shredded the skin and tissue from the outside 1 . This coordinated assault was remarkably efficient—both carcasses were completely skeletonized within 8-10 days 1 .
Complete skeletonization within 8-10 days
The fall scenario unfolded quite differently. Here, Dungeness crabs (Metacarcinus magister) became the primary initial scavengers, removing most of the soft tissue from one carcass 1 . Surprisingly, amphipods didn't appear in large numbers until Day 15, but once they arrived, they skeletonized the previously scavenged carcass by Day 22 and the less scavenged one by Day 24 1 .
Complete skeletonization by Day 22-24
Immediate colonization by amphipods and shrimp
Heavy amphipod and shrimp activity
Complete skeletonization achieved
Dungeness crabs begin scavenging
Continued crab scavenging
Large amphipod arrivals
Complete skeletonization achieved
| Day | Spring Scavengers | Fall Scavengers |
|---|---|---|
| 0-1 | Lyssianassidae amphipods, Pandalus platyceros shrimp | Metacarcinus magister (Dungeness crab) |
| 2-4 | Heavy amphipod and shrimp activity | Continued crab scavenging |
| 8-10 | Complete skeletonization | Minimal amphipod activity |
| 15+ | N/A | Large amphipod arrivals |
| 22-24 | N/A | Complete skeletonization |
| Species | Type | Scavenging Role |
|---|---|---|
| Lyssianassidae amphipods | Crustacean | Remove bulk soft tissue from inside |
| Pandalus platyceros (spot prawn) | Crustacean | Shred skin and tissue from outside |
| Metacarcinus magister (Dungeness crab) | Crustacean | Remove large sections of soft tissue |
The dramatic seasonal differences observed in this study highlight how marine decomposition is driven by complex ecological factors. Oxygen levels, water temperature, and seasonal patterns of scavenger activity all play crucial roles in determining a carcass's fate 5 .
From a forensic perspective, these findings provide valuable tools for investigating water-related deaths. By understanding which scavengers are active at different seasons, investigators can:
As Anderson notes, "Such data are very valuable for predicting preservation, planning recoveries, and managing family expectations" 1 .
This research represents just the beginning of understanding human decomposition in marine environments. The VENUS observatory continues to provide unprecedented access to deep sea processes, offering opportunities for more detailed studies of how environmental factors—including changing ocean conditions—might affect decomposition patterns.
Climate Impact
How warming oceans affect decomposition
Depth Variations
Decomposition at different depths
Species Interactions
More detailed study of scavenger behavior
As technology advances and more data is collected, forensic scientists will increasingly be able to read the story of a body's underwater journey in the marks left by its deep-sea clean-up crew. Each scavenger species leaves distinctive evidence, from the precise nibbling of amphipods to the crushing damage caused by crabs, creating a timeline that can help reconstruct events in death investigations 5 .
What happens to remains in the ocean is no longer a complete mystery—thanks to innovative technology and careful observation, scientists are gradually decoding the complex ecological processes that unfold in the deep, providing closure for families and valuable tools for justice.
This article is based on the study "Comparison of Faunal Scavenging of Submerged Carrion in Two Seasons at a Depth of 170 m, in the Strait of Georgia, British Columbia" by Gail S. Anderson and Lynne S. Bell, published in the journal Insects (2017).