STRIVE - Environmental Protection Agency

Figure 3.32. Scatter plot showing the correlation
between DNA extract and chlorophyll-a
concentrations for samples collected in Lough
Corrib (circle) and Ballyquirke Lough (triangle).
However, the nucleic acid extract concentrations
were on average significantly greater in Lough Ballyquirke
than in Lough Corrib (Student t-test, p < 0.010). This
reflected the chlorophyll-a concentrations determined
for the corresponding samples in both lakes as there
was an overall significant positive correlation between
chlorophyll-a and nucleic acid concentrations (Pearson
correlation coefficient = 0.741, p < 0.001, n = 26)
(Fig. 3.32).
A region of the 16S rDNA gene was amplified using
a nested PCR approach and two reverse primers
N. Touzet (2008-FS-EH-3-S5)
Figure 3.33. 16S rDNA polymerase chain reaction (PCR) (a) and restriction fragment length polymorphous
(RFLP) electrophoresis gels (b) of field sample extracts collected from Lough Corrib and Ballyquirke
Lough during summer 2010. The 300s and 400s number series correspond to samples from Lough Corrib
and Ballyquirke Lough, respectively.
45
specific for filamentous and spherical cyanobacteria,
respectively. The samples used were collected near
Inchiquin in the upper Corrib and at the southern
end of Lough Ballyquirke. Most extracts were
amplified successfully, returning amplicons of various
intensities and suggesting the common presence of
cyanobacteria in the two lakes during the sampling
period (Fig. 3.33). In a preliminary attempt to compare
the cyanobacterial communities in both lakes and
possibly detect seasonal changes, RFLP analysis
was carried out using a dual digestion protocol on
the pooled (filamentous and spherical) cyanobacterial
nested PCR products. The restriction profiles were
analysed visually by recording the presence and
absence of bands for each sample.
A cluster diagram showing the relationships between
the samples was then constructed from the binary
matrix (Fig. 3.34). Two major clades were apparent,
separating first samples from Lough Corrib and Lough
Ballyquirke, clustered into two separate groups,
and corresponding to all samples collected during
the June–July period of the survey. A mixed group
of samples from both lakes, mainly collected during
August (except for Lough Corrib, sample 304), was
identified. This suggests that a seasonal change in
the cyanobacterial community of the two lakes might
have occurred at the end of July.