We did not consider N concentrations, because Anabaena is an N-fixer
(Niemi,1979).Anabaena was added at a concentrationof20 mg C l1,
B. submarina at 200 mg C l1, and R. salina at 50 mg C l1, added
according to natural concentrations. Copepods were kept in a
10 3 cm mesh bag (20 mm), kept open by a plastic cylinder
allowingthe chemical signals fromthe copepods to enter the bottles,
but preventing physical interaction between algae and animals. The
bottles were incubated in 14 8C for 22–26 h (cf. similar incubation
periods:Gorokhova&Engstro¨m-O¨ st,2009;Engstro¨m-O¨ stetal.,2011)
in 0.7 mEm1 s1 light at 16:8 h light:dark regime in the laboratory.
The experiment was repeated at two sites, Tva¨rminne in the Gulf of
Finland and Reposaari in the Bothnian Sea. Ten replicates were
conducted for each treatment (in two separate batches) at each site.