Effects of Cyanobacteria on Survival and Reproduction of the Littoral Crustacean Gammarus zaddachi (Amphipoda)

Toxic cyanobacteria can have harmful or fatal impacts on aquatic organisms. In the archipelagos of the northern Baltic Sea, the open sea blooms often drift into littoral areas, where they decompose and release toxins and other chemical compounds in the water. However, the effects of cyanobacteria on the littoral organisms have not previously been investigated. We studied the effects of three cyanobacteria species (toxic Nodularia spumigena, non-toxic N. sphaerocarpa and non-toxic Aphanizomenon flos-aquae) and purified dissolved nodularin (produced by N. spumigena) on a common littoral amphipod Gammarus zaddachi. Nodularin was transferred to eggs, juveniles and adults of G. zaddachi, but no significant negative effects of dissolved nodularin were detected on adults, eggs or juveniles. However, survival of adults decreased by the exposure to toxic N. spumigena cells. The egg hatching rate and juvenile survival were not affected when exposed to the three cyanobacteria species. In contrast, a weak decrease in the egg production and an increased abortion of embryos from the brood pouch of females was observed, the later indicating a failure in parental care. Further, a decrease in grazing rate on the filamentous green alga Enteromorpha intestinalis was observed. The results suggest that toxic cyanobacteria blooms are not extremely fatal, but may have, in high concentrations, negative effects on the adult survival, fecundity, and feeding behaviour of gammarids inhabiting the littoral zone.