The copepods were collected in June and August 2009 from two
pelagic areas, Storfja¨rden close to Tva¨rminne Zoological Station in
the Gulf of Finland and off Reposaari in the Bothnian Sea.
Zooplankton samples were taken from approximately 25m depth
using a 50 or 200 mm net. The contents of the tows were diluted in
surface water, brought to the laboratory and kept at 15 8C with
gentle aeration until sorting commenced. Five egg-bearing females
of the calanoid copepod Eurytemora affiniswere added into each 1.2 l
bottle of the AZ treatment (cf. below). Animals were sorted in petri
dishes filled with GF/C filtered seawater (FSW) using glass pipettes