3.5. Elemental composition of the carcasses.
In this analysis, we aimed to identify inorganic ions that enhance the
preservation of SBO. Thus we focused on the correlation between the
deposition of different elements on the carcasses and the degree of
their preservation. We used SEM/EDX multiple point analysis to measure
chemical elements (1) in the patches of tissues free of visible sediment
particles and bacteria and (2) in the sediment particles that were
adhered to tissues (Figure 5, Table 5).
In the three sediments with the highest degree of preservation
(montmorillonite, kaolinite and silica, Table 3) the carcasses were
enriched in aluminium and silicon. In the chamosite and clinochlore,
where the preservation was poor, aluminium and silicon entered the
tissues in minimal amounts (Table 5). Iron appeared in increased amounts
in the well preserved carcasses from the montmorillonite and in the
poorly preserved carcasses from the chamosite. The chamosite-hosted
carcasses contained much more iron and less magnesium than the carcasses
from the clinochlore, in concordance with the initial chemical
composition of the two sediments (Tables 2 and 5, Figure 6 A).
Calcium was detected in the carcasses from all sediments and ASW,
regardless of the initial elemental composition of the sediments and
water. The results imply that calcium was effectively absorbed by the
carcasses both from the sediment and from the water (Figure 6 B). Other
elements from the dissolved sediments (Al, Si, Mg, Fe) apparently have
entered the carcasses in a more passive way, and this is why the greater
the amount of an element in the sediment, the higher is its content in
the body tissues (Figure 6 B).
Different elements appeared in the solutions due to leaching of the
corresponding sediments. This is in concordance with mineralogical
transformations detected in the experimental sediments. The results of
mineralogical analysis (STA, see Material and Methods) of the kaolinite
and clinochlore were reported previously (Naimark et al., 2018 a, b).
The results for the chamosite and montmorillonite are shown in Figure 7.
They show that decaying organic matter promotes structural
disintegration of the sediment and leaching of ions. In the
montmorillonite, the strong alkaline environment accelerated the release
of silicon species to a greater extent than in the artificial silica
sediment with moderate alkalinity (Crundwell, 2014).