Decomposition

Decomposition seemed much slower than on land in similar geographic areas (Anderson and VanLaerhoven 1996). On land, carcasses progress through fresh, bloat, active decomposition, advanced decomposition and remains stages (Anderson and VanLaerhoven 1996, adapted from Payne 1965). In these experiments, the carcasses did go through most of these stages, although they were modified from those seen on land (Anderson and Hobischak 2004). When first placed, most of the carcasses floated with the head towards the ground for a few hours, then sank after 18-28 h at both depths (Table 12.1). The remains appeared to be in the fresh stage from submergence until 3 days after submergence, when bloat was first observed. Bloat lasted from Day 3 to Day 11 in most carcasses, despite depth. In some carcasses, the body remained suspended in the water column for several weeks, apparently being held up by gases maintained in pockets in areas of the body rather than true bloat (Anderson and Hobischak 2002, 2004). In the fall experiments, the first examination was not possible until Day 19, and at that time, most of the pigs were still floating, except one or two that had become wedged between rocks (Table 12.2).

By Day 11 in spring, the flesh was decomposing, with exposed bone in places at both depths. Significant scavenging had occurred and the skin was sloughing in places, and hair was shedding (Anderson and Hobischak 2002).

Table 12.1 Description of pig carcasses placed out in May (spring) in Howe Sound at 7.6 and 15.2 m. See Table 12.3 for details of fauna collected and observed on remains (Anderson and Hobischak 2004; 2002) Elapsed time since submergence 7.6 m 15.2 m

3 days

11 days

No fauna present, floating with snout towards seabed. Coagulated blood still at wounds.

All three carcasses have sunk to seabed. Many small amphipods "sea lice" seen all over carcasses, several species present. Carcasses look fresh, slight stomach distention in one. lividity visible in some. Larval herring present, feeding on amphipods. All coagulated blood gone.

No fauna seen on carcasses. Strong current present. Silt on carcasses. No outward signs of decomposition.

Bloating starting in some carcasses, a few amphipods on one carcass, a mottled sea star and 3 Oregon tritons present. One carcass has no fauna, but ears appear frayed from feeding.

Decay apparent, exposed areas of flesh, some exposed bone, skin sloughing, hair falling off. hind ends, thighs, tail, and ears show signs of feeding. Silt and algae on carcasses. Bloat apparent, adipocere seems to be forming on snout of one carcass floating with snout in contact with sediment. Fauna only on carcass on seabed. 1 leather star and some sand dabs near body.

Two of three carcasses floating, snout down. Two carcasses one floating and one on seabed, have fauna present, including whelks in nostrils and on skin and sea stars on and actively moving towards remains. Crab, shrimp, copepods. annelids, and sea urchins also collected.

Two of three carcasses have sunk, one still floating. Some small amphipods present but not as many as at 7.6 m. Coon striped shrimp seen but scared away by lights. More whelks getting into wound. Seas stars present, including large sunflower sun star enveloping rump of one. Carcasses same as at 7.6 m, look fresh, lividity visible in some. Larval herring present, feeding on amphipods. All coagulated blood gone. Silt accumulating over body.

Much less current. Large sunflower sea star still present on rump as well as Vermillion sea stars . One carcass still floating, only one shrimp present on it, but red marks on hocks, may be feeding damage.

Bloating starting in some carcasses. Large sea star gone, but large circular mark left at site of sea star, appears partially 'digested'. Some Vermillion sea stars and Oregon tritons present, 2 red rock crabs tearing at flesh.

Decay apparent, exposed areas of flesh, some exposed bone on legs, bloat still present. Evidence of scavenging on ears, abdomen and hind end. One carcass less bloated, lying on seabed and adipocere appears to be forming on snout. Many large sunflower sea stars on two carcasses, completely covering one. Hermit crabs and sand dabs present and feeding. Two carcasses covered in algae and silt.

30 days One carcass lost, rope fouled on concrete blocks, and cut by wave action. Both remaining carcasses floating. Feet gone in one and one foot remaining in other. Skin and hair remaining in some areas, but parts of skull and much of spine and legs skeletonized. Skin of ears remaining. Abdomen and torso intact. No fauna observed.

40 days Only one carcass observed. Still floating. No skin present, spinal column and part of skull fully exposed. Adipocere tissue present. Bones fallen to seabed below carcass. Ribs skeletonized. Gut still intact and floating. Seal nearby and schools of fish.

47 days Both carcasses still floating, although one not as high as before. Vertebrae exposed. Adipocere. Barnacles appear to be growing in one eye socket. Very little fauna.

54 days Remaining tissue being eroded by surge of tide against concrete blocks. Body showing extreme adipocere formation. Mandible still articulated. Stomach in one is still intact and hanging out as a bag. Other carcass is now touching seabed at snout, but hind end is still bloated and floating, with intestines present near rectal area. Only fauna present are mussels and some small fish.

116 days Two remaining carcasses are reduced to just a few bones.

Some bones missing. White moss algae all over one set of bones. Bones appear brown, no cartilage present.

140 days Fifty-nine bones recovered from one carcass and 12 from other. Many small animals recovered on bones.

Part of intestine 'balloon-like' and holding up two carcasses, although most of the carcasses are skeletonized. Rib cage appears empty of organs in one, with abdomen intact in two. Skull skeletonized in all three. Limbs gone. Muscle falling off, and bones on sediment in carcasses still afloat. Only fauna are sunflower and Vermillion sea stars.

Only one carcass observed. Floating, snout down. Head heavily scavenged, with bones on face exposed. Brain still present. Internal organs exposed. Adipocere tissue present. No fauna on carcass.

Two floating, even though one is almost completely skeletonized. One on ground also mostly skeletonized. Sunflower sea star on bones of one. Small halibut under body of one. No other fauna.

Skin remaining on bones and some bones now disarticulated and on ground. Two carcasses now on seabed. Bag of skin and bones is all that is left of one, still floating. Mandibles disarticulated, most of remains are skeletonized. Large hole seen in chest area of one carcass. Stomach present in one and hanging out like a bag, although now supine on ground. Only animals are sea stars and small fish.

One carcass gone, no bones recovered. Remaining carcasses are only bones, some teeth and bones missing. No fauna. Leaf kelp present.

Twenty-four bones recovered from one carcass and 57 from second. Most bones black in colour. Many small animals recovered on bones.

Table 12.2 Description of pig carcasses placed out in October (fall) in Howe Sound at 7.6 and 15.2 m. See Table 12.4 for details of fauna collected and observed on remains (Anderson and Hobischak 2004; 2002) Elapsed Time Since

Submergence 7.6 m 15.2 m

19 days

26 days 33 days

35 days

48 days

225 days

Head of one carcass wedged between two rocks. Algae covering one carcass more than others. Not much silt. Carcasses mostly intact. Scavenging damage on surface of body, such as ears. feet, along spine. Only one leg intact in one carcass. Skin sloughing. Very few fauna present.

One carcass very heavily scavenged. Tissue hanging off. extremities missing, skin sloughing. Adipocere tissue. Algae present. Very few fauna present.

Two carcasses still floating, one on seabed. One leg remaining on one carcass, rest of limbs gone or skeletonized. Adipocere on nose of one carcass. Surface scavenging on head. ears, partial skeletonization, spine exposed. Head and hind quarters still intact in one. Algae present. No fauna seen.

Only one shallow carcass recovered for close examination then replaced after 1 h. Carcass still bloated and floating. Skin and hair sloughing, surface scavenging on neck, lower abdomen and hind quarters, three legs gone, most of abdomen covered in adipocere. face still intact, silt collecting in shedding hair. Deep hole in one flank, and eroded area on other flank. Fauna included annelids, copepods and some arthropods.

No carcasses examined.

Only bones remaining, many animals, mostly mollusks associated with the bones. Mussel and kelp bed forming in area on one carcass. Four bones recovered from one carcass. 57 from another and nothing recovered from the last. Bones blackish in colour. Most bones from torso rather than limbs.

One carcass on sediment, other two floating or partially floating. Heavily scavenged, internal organs exposed and hanging out of body cavity, algae and silt on all carcasses. Partial skeletonization. Two legs missing in one carcass. Very few fauna present.

Heavily scavenged, adipocere tissue and skeletonization. Remains of one on ground. Tissue present on ground nearby. Very few fauna present.

All three floating again. Adipocere formation, tissue lying on ground below carcasses. Tissue on ground attracting sea stars. Algae and silt on carcasses. Skin, tissue, hair and adipocere tissue sloughing. Partial skeletonization. Feet absent in one carcass, three intact on another.

No carcasses examined.

Only one deeper carcass recovered for close examination then replaced after 1 h. Carcass still bloated. Skull partly skeletonized, with spinal column and muscle tissue exposed. Remaining skin looks bleached and speckled. Hair mostly gone. Three legs gone.

Only bones remaining, many animals, mostly mollusks associated with the bones. Twenty-eight bones recovered from one. with some mollusks attached. Most bones associated with torso not limbs. Some bones have spongy appearance. Twenty-seven bones recovered from a second, and none from the last, although all rope apparatus tethering carcass was intact, so bones removed.

Bloat was still apparent in some carcasses at this time. Also, at this time, two carcasses, floating but with the nose in contact with the sediment, appeared to be forming adipocere on the tissue in contact with the seabed. In the spring experiments, extensive adipocere formation was seen by Day 40, and by Day 33 in the fall experiments (Tables 12.1 and 12.2).

In the spring experiment, by Day 30, half the carcasses were still floating, held up still by gases in the intestines. Those that had sunk to the seabed were much more scavenged and skeletonized than those that floated, and the degree of skele-tonization also appeared to be a function of whether the carcass fell onto sand or rock. One carcass was lost at the shallower depth by the rope rubbing against the concrete weight and breaking. In the fall experiment, by Day 33, five of the six carcasses were still floating. The limbs had been scavenged, and most carcasses were missing some or all the legs, although the torso was mostly intact and skin and hair remained in places (Anderson and Hobischak 2002). There was no clear distinction seen between active and advanced decay.

In spring, the remaining shallow carcasses and two of the deeper carcasses were still suspended in the water column by Day 47, although all were partially skeletonized. In the fall experiments, two different carcasses (one from 7.6 m and one from 15.2 m) were each briefly brought to the surface for closer examination on Day 35 and Day 48, and then immediately replaced. On both occasions, the remains were still bloated and adipocere tissue was present. At Day 35, only surface scavenging was noted on the abdomen, hind end and neck. At Day 48, the carcass was partially skeletonized and both muscle tissue and the spinal column were visible (Anderson and Hobischak 2002). In one case, part of the remains was externally coated in adipocere tissue, which protects the inner areas (Hobischak and Anderson 2002; Hobischak 1998).

During active decay, parts of the carcasses were skeletonized but in many cases, the carcasses continued to exhibit bloat and remained off the sea bed. Organs were still present in some carcasses, although ribs, skull and spine became exposed. There was no clear delineation between active and advanced decay as there is on land, and by 40 days post submergence in the spring experiments, most carcasses were entering the remains stage, although tissue and organs were still present in some carcasses (Anderson and Hobischak 2004, 2002). The bones were recovered on Day 140 after the spring experiment.

Only six examination days were possible in the fall due primarily to a lack of divers and vessels. No examination was possible until 19 days after submergence. Therefore, much of the decomposition and faunal colonization was missed. By 19 days post submergence, the carcasses had passed the bloat stage, although some continued to float, as in spring (Table 12.2). Those on the ground had been heavily scavenged although tissue and organs did remain and skin was sloughing. By 26 days post submergence, several of the carcasses showed extensive adipocere formation, and some had been scavenged heavily although few animals were present. At Day 33, all but one carcass was still floating. In the fall experiments, the remains were not examined between Day 48 and Day 225, when the bones were recovered and at Day 48, the remains were still bloated and the torso was intact.

0 0

Post a comment