STRIVE - Environmental Protection Agency

2.2 Field Sampling
2.2.1 Summer 2009 and 2010 Surveys
In 2009, one station was sampled in each water
body, directly from the shore or within 300 m using a
floating platform. An effort was also made to spatially
segregate sampling occasions within the clusters
so as to encompass potential seasonal succession
changes (Fig. 2.3, Table 2.2). The station location was
selected according to road access so as to limit the time
requirement on the lake and minimise sampling costs.
All samples were taken just beneath the water surface.
In 2010, sampling was carried out on a near weekly
basis in Lough Corrib (Co. Galway) and Lough
Ballyquirke (Co. Galway) where surface water samples
were collected along a transect of stations (Fig. 2.4).
Samples from Lough Graney (Co. Clare) were also
periodically collected from the shoreline throughout
the summer and using an autonomous water column
sampler (Aquamonitor, EnviroTech) for 30 days during
August–September (Fig. 2.4). The instrument collects
independently up to 50 water samples according to
a predefined sampling sequence through a syringe
pumping mechanism and a 50-way multi-port valve.
The instrument was programmed to collect 200 ml
water sample every two days during the deployment
period. Samples were stored in gas-impermeable
bags containing 3 ml of Lugol’s Iodine for preserving
the planktonic material. In addition, in-line cartridges
containing the polymer resin SP700 (Sepabeads ® )
were used as passive samplers for the adsorption of
microcystins. Every two days and for one week, 400 ml
were passed through one cartridge, four cartridges
being connected to different collecting ports of the
N. Touzet (2008-FS-EH-3-S5)
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instrument. In situ temperature was also recorded
during the sampling period using a StowAway TidbiT
Temperature Logger, which was attached to the frame
of the Aquamonitor. After the instrument was retrieved,
the content of each bag was transferred in the laboratory
into a tissue culture bottle supplemented with ~0.5 ml
of Lugol’s Iodine for ulterior phytoplankton analysis,
and the cartridges were stored at -20°C until further
processing.
2.2.2 Data Acquisition
Samples and data were acquired for each lake/station
as follows. Surface water temperature and depth
were measured using a handheld echo sounder,
geographical coordinates were taken with a GPS and
water transparency was determined with a Secchi disk.
Water samples were collected and preserved with
Lugol’s Iodine in 50 ml bottles for microscopy analysis.
Water samples were also filtered onto Whatmann GF/F
filters (47 mm diameter) for subsequent analysis of
chlorophyll-a, used as a phytoplankton biomass proxy,
and the cyanobacterial toxins microcystins. Additional
water samples were filtered (150 ml) onto cellulose
nitrate filters (Whatmann, 25 mm diameter, 1.0 µm
pore size) and placed into 2 ml tubes for ulterior nucleic
acid extraction. All filters were stored in the dark at
-20°C until further processing. The meteorological
conditions at the time of sampling were logged under
the following designations: sunny spells, overcast and
rain. Additionally in 2010, water column profiling up to
15 m depth was carried out in both Lough Corrib and
Ballyquirke Lough using an YSI MultiQuatroPro probe,
which was slowly lowered from the side of the sampling
platform to measure temperature, conductivity, pH and
dissolved oxygen levels.
Figure 2.3. Designations and sampling timeline of the 50 lakes selected in 2009 from the clusters of river
catchments defined by similarity analysis and hierarchical clustering.