6 research outputs found
Sex-associated variations in coral skeletal oxygen and carbon isotopic composition of <i>Porites panamensis</i> in the southern Gulf of California
Coral δ18O variations are used as a proxy for changes in sea
surface temperature (SST) and seawater isotope composition. Skeletal δ13C of coral is frequently used as a proxy for solar radiation because
most of its variability is controlled by an interrelationship between three
processes: photosynthesis, respiration, and feeding. Coral growth rate is
known to influence the δ18O and δ13C isotope record to a
lesser extent than environmental variables. Recent published data show
differences in growth parameters between female and male coral in the
gonochoric brooding coral Porites panamensis; thus, skeletal
δ18O and δ13C are hypothesized to be different in each
sex. To test this, this study describes changes in the skeletal
δ18O and δ13C record of four female and six male
Porites panamensis coral collected in Bahía de La Paz, Mexico,
whose growth bands spanned 12 years. The isotopic data were compared to SST,
precipitation, photosynthetically active radiation (PAR), chlorophyll a,
and skeletal growth parameters. Porites panamensis is a known
gonochoric brooder whose growth parameters are different in females and
males. Splitting the data by sexes explained 81 and 93 % of the
differences of δ18O, and of δ13C, respectively, in the
isotope record between colonies. Both isotope records were different between
sexes. δ18O was higher in female colonies than in male colonies,
with a 0.31 ‰ difference; δ13C was lower in female
colonies, with a 0.28 ‰ difference. A difference in the skeletal
δ18O could introduce an error in SST estimates of ≈ 1.0
to ≈ 2.6 °C. The δ18O records showed
a seasonal pattern that corresponded to SST, with low correlation
coefficients (−0.45, −0.32), and gentle slopes (0.09,
0.10 ‰ °C−1) of the δ18O–SST relation.
Seasonal variation in coral δ18O represents only 52.37 and
35.66 % of the SST cycle; 29.72 and 38.53 % can be attributed to
δ18O variability in seawater. δ13C data did not
correlate with any of the environmental variables; therefore, variations in
skeletal δ13C appear to be driven mainly by metabolic effects. Our
results support the hypothesis of a sex-associated difference in skeletal
δ18O and δ13C signal, and suggest that environmental
conditions and coral growth parameters affect skeletal isotopic signals
differently in each sex. Although these findings relate to one gonochoric
brooding species, they may have some implications for the more commonly used
gonochoric spawning species such as Porites lutea and
Porites lobata
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Characterisation of microbial attack on archaeological bone
As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved