D. magna in situ bioassays were conducted as described by
Barata et al. (2007) using the same test chambers and procedures
of Mc William and Baird (2002b) with only minor modifications
that included 9–10 test chambers to allow collection of animals for
biomarker determination and to increase the number of replicates
for post-exposure feeding rate measurements. Chamberswere constructed
from clear polyvinyl chloride cylindrical piping (13 cm
long, 5 cm external diameter). Each chamber had two rectangular
windows (7cm×3.5 cm) cut into either side of the cage, covered
with 150-m nylon mesh. Pipe ends were sealed with polypropylene
caps. Groups of 4–5 chambers were placed inside a 13-mm2
wire-mesh cylinder that was positioned in the stream perpendicular
to flow. Deployments were conducted during spring (April)
and summer (July) of 2004 and 2006 in the Llobregat and Beso´ s
river basins, respectively.Within each month two to three deployments
were conducted simultaneously in three to four locations
that always included at least one reference site