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T. Sime-Ngando et al. (eds.), Lake Pavin, DOI 10.1007/978-3-319-39961-4
Glossary
δ^13 C this parameter corresponds to the isotopic carbon
composition (so-called isotopic signature) of a sample,
expressed as^13 C/^12 C ratio which is compared to a refer-
ence material:
δ^1313
12
13
12C 1C
C
C
Csamplereference=
−
×1000‰Both isotopes have similar physicochemical properties
but slight behavior differences, mainly due to the mass
difference, lead to isotope fractionation. For example,
during photosynthesis, faster diffusion of^12 C relative^13 C
in leaf tissues and other chemical processes results in a
greater uptake of^12 C versus^13 C in the organic matter. The
δ^13 C of the organic matter is consequently lower (typi-
cally −25‰ for C3 plants) than to that of the dissolved
CO 2 or atmospheric CO 2 (≈−8‰). By consequence of
photosynthesis, in water, the residual dissolved CO 2 (or
DIC) is enriched in heavy isotope. δ^13 C is then a powerful
tool to infer biogeochemical reactions, as well as carbon
sources (as isotope carbon composition depends also on
the producer organisms).(^14) C ages dating of materials containing carbon is now a days
performed through the determination of the ratio of^14 C
radioactive isotope versus 12 C stable isotope in a sample
that initially incorporated^14 C from atmospheric CO 2
(piece of wood, leaf, charcoal, particulate organic matter
(POC), carbonate precipitate from water DIC content...).
The principle is based on the radioactive decay of^14 C
(half-life ⊕ 5730 yrs). There are several ways to express
the result: (1) age in years BP (before present = before
1950); (2) however, due to some variation in the^14 CO 2
production rate in the atmosphere (^14 C is continuously
produced in the upper atmosphere due to solar radiation),
the raw age value has to be corrected: age is expressed in
years cal. BP (calibrated BP); (3) alternatively the result
may be expressed in percent of modern carbon (PMC):
100 % PMC means that the sample is “modern” – actual –
whereas 0 % PMC means that the sample is old (contains
“dead” carbon, i.e. more than tenfold the half-life).
18S rDNA (18S rRNA) Abbreviation of 18 S ribosomal
DNA (or RNA). 18S rDNA is a part of the rribosomal
DNA. The small subunit (SSU) 18S rDNA is one of the
most frequently used genes in phylogenetic studies.
18S rDNA Gene encoding the RNA component of the small
ribosomal subunit, and widely used to identify and clas-
sify organisms. clone library Heterogeneous collection of
cloned sequences (often 18S rDNA) derived from a com-
plex assemblage of organisms.
AD Latin abbreviation for Anno Domini used in Julian and
Gregorian calendars.
AMS radiocarbon radiometric method using an accelera-
tor mass spectrometry (AMS) to measure isotopic record
of^14 C carbon in order to date an organic sample. The
isotopic composition of C can be used for stratigraphic
correlations.
ASCONIT engineering consulting firm
ATHOS engineering consulting firm
Abiotic Not associated with or derived from living
organisms.
Acoustic facies acoustic signature of sedimentary material
according to the presence, frequency, amplitude, continu-
ity and geometry of reflections on seismic profiles.
Acoustic substratum horizon or formation absorbing
acoustic waves on sub-bottom profiles generally associ-
ated with bedrock.
Aerobic Relating to, involving, or requiring free oxygen.
Alcian Blue a dye used to stain acidic polysaccharides.
Aliphatic Compound having an open chain structure, not
aromatic.
Alkalinity by definition this chemical quantity is:
alkH=+[]CO 33 −− 2 []CO^2 ++[]OH−+[]basesH−−[][]acids
where [bases] corresponds to basic species engaged in
acid-base couple with pKa> 4 and [acids] corresponds
to acid species engaged in acid-base couple with pKa< 4
(e.g. [NH 3 ], [HPO 42 −], 2 ×...[]PO 43 − or [H 3 PO 4 ] respec-
tively). Alkalinity is modified by dissolution or precipi-
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