Effects of short-term exposure to different salinity levels onMyriophyllum spicatumandCeratophyllum demersumand suitability of biomarkers to evaluate macrophyte responses to salinity stress

M. spicatumandC. demersumexposed to different salinity levels in a laboratory study. Two species exhibited species-specific salinity sensitivities reaching different physiological statuses at each salinity level. Elongation rates were correlated with several biochemical parameters. These correlations can be used in evaluating the expected responses of two species to salinity. Sea-level rise caused by global warming is leading to increased freshwater salinization, which causes significant stress on aquatic ecosystems and species, including macrophytes. To form a better understanding of the responses of macrophytes to salinity stress, we assessed biochemical, pigmentation and growth responses ofMyriophyllum spicatumL. andCeratophyllum demersumL. exposed to different salinity levels (0, 1.5, 2.5, 5.0, and 10 ppt). For both species, elongation rates decreased, and levels of photosynthetic pigments (chlorophyllaand chlorophyllb) increased at higher salinities (5 ppt and 10 ppt). Anthocyanin and H(2)O(2)concentrations increased inM. spicatumbut decreased inC. demersumwith the increase in salinity. The activities of antioxidant enzymes (guaiacol peroxidase, catalase, and ascorbate peroxidase) were different between two species and fluctuated along the salinity gradient.M. spicatumandC. demersumexhibit species-specific salinity sensitivities, reaching different physiological statuses at each salinity level. Elongation rates were significantly correlated with several biochemical parameters in a species-specific manner. These correlations can be used in evaluating the expected responses of these two species to salinity changes. The species-specific responses of most parameters measured in the present study suggests the inapplicability of common biochemical responses across species.