Environmental Engineering Reference
In-Depth Information
2D Stress: 0.11
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Figure 7.3. Multidimensional scaling of data on bacterial community structure in
the Hayle and Fal estuaries (from Ogilvie & Grant 2008 ). Site numbers as in Fig. 7.2 ,
with higher numbers indicating higher sediment pore water Cu concentrations.
replicate T-RFLP analyses on each of two sediment samples collected from each
site. Replicate analyses on the same sample are generally close together in Fig.
7.3 , but replicate samples from the same site may have bacterial communities
that are almost as different from each other as the differences between the
least and most contaminated sites. Despite this, the communities show strong
differentiation in metal tolerance that is closely correlated with sediment
metal concentrations. Thymidine and leucine incorporation rates at the least
contaminated site are more than four orders of magnitude more sensitive to
Cu than those from the most contaminated site in the Hayle estuary. So there is
a strong ecological impact of Cu on the microbial communities present, but
conventional ecological monitoring methods completely fail to detect it.
It is difficult to reach any clear conclusions as to the extent of ecological
impacts on the macrofauna in these systems. Only very occasional individuals
of the bivalve Scrobicularia plana are found in Restronguet Creek, although this
does occur in the other tributaries (Bryan & Gibbs 1983 ). Warwick ( 2001 ) shows
that the macrofauna in the Fal is different from that in other muddy estuaries
in South West Britain, with over-representation of small polychaetes relative to
other muddy estuaries. He notes that the isopod Cyathura carinata is absent from
the Fal. He also suggests that the amphipod Corophium volutator is absent from
the Fal, but in fact it does occur sporadically in the most contaminated parts
of Restronguet Creek (Bryan & Gibbs 1983 ) and the Hayle estuary (personal
 
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