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Sediment water, organic and silt/clay contents - There were no statistical
differences between patches and non-patches for water content (Figure 8.12(i)), while
for the % silt/clay and % organic contents, significantly higher values were found in P.
elegans patches throughout the sampling period from April 1997 to August 1998
(Figures 8.12(ii-iii)). Silt/clay content remained at approximately 5% in non-patch
samples while it rose to 14.2% ± 0.64% in August 1997 in patches, then slowly
decreased to 9.58% ± 0.95% in August 1998. A decreasing trend was observed for the
organic content in patches from 3.6% ± 0.19% at the start of the sampling period to
2.4% ± 0.08% in August 1998, although this was always significantly higher than in
non-patch sediments, which was consistently around 2%.
Redox potentials - Whilst sedimentary variables such as the silt/clay and organic
contents showed clear differences between patch and non-patch sediments, the results
of the redox measurements were more equivocal. Figures 8.13(i-iii) show that the
redox profiles of the two plot types were very similar between April and December
1997. However, during August 1998, the sediments at 1 cm and 2cm depths in P.
elegans patches were significantly more reducing than those in non-patch areas, while
at the 4cm depth, they were significantly less reducing than non-patch sediments
(Figure 8.13(iv)).
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