Effects of food salinization on terrestrial crustaceans Porcellio scaber
Salinization of soil as the main cause for soil degradation is a global issue. Despite this, the data concerning the effects of different salts on terrestrial organisms are still missing. Our aim was to address the effects of four different salts (NaCl, KCl, NaNO3, and KNO3) on terrestrial isopods Porcellio scaber. Two types of experiments were performed. In the first experiment, the isopods were exposed to 1, 2, and 5 g salt/kg dry leaf for 14 days and afterwards animal mortality, feeding activity, moult and growth were monitored. In the second experiment, a 48-h soil selection tests was done to investigate their preference/avoidance to certain salts. The feeding rate and growth efficiency of isopods decreased in a dose-dependent manner after 14 days exposure to KNO3 and NaNO3. We suggest that nitrate (NO3−) may be the predominant reason for these effects, because (i) the effects were only observed in the case of NO3−-salts, and (ii) K+ and Na+ induced no effects in the case of Cl−-salts where the concentrations of these two cations were even higher as in the case of NO3− salts. 48-h soil selection test showed that isopods were able to choose between NaCl dosed and unamended soil: the isopods preferred to spend time on NaCl spiked soil (up to 5 g salt/kg dry soil). In the case of KNO3 and NaNO3 no significant soil selection by isopods was found. In these two exposures isopods spent approximately 50% of their visits on both sides of the soil. The survival of isopods decreased in a dose independent manner when exposed to NaNO3, KNO3, and KCl. We conclude that NaNO3, KCl, and KNO3 affect the isopods, while no effects were caused by NaCl under the exposure conditions of this study. This study implies that also other salts besides commonly investigated NaCl should be tested when the potential hazard of soil salinization to terrestrial organisms is in question.