Abstract
Decomposition and faunal colonization of a carcass in the terrestrial environment has been well studied, but knowledge of decomposition in the marine environment is based almost entirely on anecdotal reports. Three pig carcasses were deployed in Saanich Inlet, BC, over 3 years utilizing Ocean Network Canada’s VENUS observatory. Each carcass was deployed in late summer/early fall at 99 m under a remotely controlled camera and observed several times a day. Dissolved oxygen, temperature, salinity, density and pressure were continuously measured. Carcass 1 was immediately colonized by Munida quadrispina, Pandalus platyceros and Metacarcinus magister, rapidly scavenged then dragged from view by Day 22. Artifacts specific to each of the crustaceans’ feeding patterns were observed. Carcass 2 was scavenged in a similar fashion. Exposed tissue became covered by Orchomenella obtusa (Family Lysianassidae) which removed all the internal tissues rapidly. Carcass 3 attracted only a few M. quadrispina, remaining intact, developing a thick filamentous sulphur bacterial mat, until Day 92, when it was skeletonized by crustacea. The major difference between the deployments was dissolved oxygen levels. The first two carcasses were placed when oxygen levels were tolerable, becoming more anoxic. This allowed larger crustacea to feed. However, Carcass 3 was deployed when the water was already extremely anoxic, which prevented larger crustacea from accessing the carcass. The smaller M. quadrispina were unable to break the skin alone. The larger crustacea returned when the Inlet was re-oxygenated in spring. Oxygen levels, therefore, drive the biota in this area, although most crustacea endured stressful levels of oxygen to access the carcasses for much of the time. These data will be valuable in forensic investigations involving submerged bodies, indicating types of water conditions to which the body has been exposed, identifying post-mortem artifacts and providing realistic expectations for recovery divers and families of the deceased.
Highlights
Terrestrial decomposition and the related taphonomic processes have been, and remain, an area of considerable investigation, see [1,2,3] A solid understanding of decomposition and the biotic and abiotic factors which impact it is valuable ecologically, and in a more pragmatic, medico-legal setting
Very little is known about the taphonomy of a body in the marine environment
The third carcass deployment, was quite different, with only M. quadrispina attracted at the beginning, followed by a long period with no arthropod activity, a sudden upsurge of both invertebrate and vertebrate activity
Summary
Terrestrial decomposition and the related taphonomic processes have been, and remain, an area of considerable investigation, see [1,2,3] A solid understanding of decomposition and the biotic and abiotic factors which impact it is valuable ecologically, and in a more pragmatic, medico-legal setting. In general, temporal changes to the body are known and some early temporal statement may be made on elapsed time since death using environmental factors such as insect colonization [2] and plant growth [4]. This study was developed in order to begin an understanding of the decomposition process and the factors that impact it, in a deep coastal marine environment near Vancouver Island, British Columbia
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