STRIVE - Environmental Protection Agency

3.6.2 Detection of Microcystins in Field Samples by
PP2A and Analytical Chemistry
All the methanolic extracts obtained from the filtered
surface water samples were tested using PP2A.
Inhibition was quantifiable in 12 extracts only, with a
range of estimated concentration from 0.006 to
0.020 µg.l-1 MC-LR eq. in the corresponding lakes,
values well below the recommended WHO limit of
1 µg.l-1 . The highest concentrations were determined
in the methanolic extracts from loughs Graney,
Sheelin and Lickeen. Contingency tables showed
there were no significant patterns in space and time
for the detection of microcystins in the lakes sampled
(X < 5.06, p = 0.05, df = 2). There was also no
significant correlation between the MC-LR equivalent
concentration estimates found from the water extracts
with the trichome concentrations of Anabaena sp. and
N. Touzet (2008-FS-EH-3-S5)
Figure 3.24. Un-weighted pair group method with arithmetic averages (UPGMA) dendrogram generated in
PAUP based on the restriction profile analysis of the polymerase chain reaction (PCR) amplified mcy-A gene
fragments from the water extracts obtained during summer 2009.
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Oscillatoria sp. determined in the corresponding water
column samples (p = 0.32, r = -0.15, n = 12). Only in 7
out of the 12 lakes where MC-LR activity was detected
by PP2A was the mcy-A gene detected by PCR. Those
were both from cluster A (Lough Graney, Lickeen,
Garadice) and from cluster B (New Lake, Knocka
Lough, Lough Ree, Lough Sheelin).
Confirmatory HPLC and MS/MS analysis was carried out
on the methanolic extracts that proved positive by either
mcy-A or PP2A analysis. The presence of microcystins
was positively confirmed in only three extracts from
Lough Lickeen, Garadice Lough and Lough Sheelin,
all three both positive for PP2A and mcy-A. The variant
microcystin LR (MC-LR) was identified in all the three
lakes while MC-YR was additionally present in the
Lough Sheelin extract (Fig. 3.25).