Response Of Physiology And Quality Of Macroalgae Ulva Prolifera And U. Linza To Salinity Change Of Seawater

The experiments were carried out studying the effects of different concentrations of seawater (0%,10%,50%,100%,200%,300%seawater) on Ulva prolifera (floating type, fixation type) and U. linza. The main study contents were growth, osmotic adjustment, inorganic ions and organic solute content, antioxidant metabolism and alga quality. We also compared their salt tolerance capacity. The main results are as follows:(1) compared with the non-seawater treatment, the biomass of U. prolifera (floating type) and U. prolifera (fixation type) showed a positive growth under10%,50%,100%,200%seawater treatments, and the biomass of U. linza only showed a positive growth under50%and100%seawater treatment. The FM and RGR of U. prolifera (floating type) and U. linza reached the maximum values under100%seawater treatment while the the FM and RGR of U. prolifera (fixation type) reached maximum values under50%seawater treatment. The growth of these3Ulvas were all inhibited significantly under300%seawater treatment, and the inhibition degree of U. linza was the largest. The contents of Chl a, Chl b, Chl, Car, and the ration of Chl a/Chl b of these3plant materials were increased significantly under10%seawater treatment, and then decreased with with seawater salinity increasing. The contents of Chl a, Chl b, Chl,Car, and Chl a/Chl b ratios of U. prolifera (floating type) and U. linza achieved the peak values under100%seawater treatment, while the contents of Chl a, Chl b, Chl,Car, and Chl a/Chl b ratios of U. prolifera (fixation type) reached peak values under50%seawater treatment. With the salinity increasing, the chlorophyll fluorescence parameters of3Ulvas were changed with the same pattern of indices of FM and chlorophyll.(2) The contents of Na+, Ca2+, Cl" of U’va prolifera (floating type, fixation type) and U. linza were increased gradually with the seawater salinity increasing, they all reached the maximum under300%water treatment. The K+and K+/Na+were reduced gradually with seawater salinity increasing, and reached the minimum under300%seawater treatment. Compared with control, the Mg2+, N, P, SS, SP, PRO, OA contents of Ulva prolifera (floating type, fixation type) and U. linza were increased significantly under10%seawater treatment, and with the seawater salinity increasing, the Mg2+, N, P, SS, SP, PRO, OA contents were increased. The Mg2+, N, P, SS, SP, PRO, OA contents of Ulva prolifera (floating type) and U. linza reached the maximum under100%seawater treatment, while the Mg2+, N, P, SS, SP, PRO, OA contents of Ulva prolifera (fixation type) reached the maximum under50%water treatment. The PRO contents of3Ulvas reached the maximum under300%seawater treatment. The OAA of these Ulvas were increased under10%seawater treatment, the OAA of Ulva prolifera (floating type) and U. linza reached the maximum under100%water treatment, while the OAA of Ulva prolifera (fixation type) reached the maximum under50%seawater treatment, and were decreased with seawater salinity increasing.(3) Compared with control, the contents of TBARS, SOD, POD, CAT, GR and GSH of two Ulva species were decreased under10%seawater treatment. With the seawater salinity increasing, the contents of TBARS, SOD, POD, CAT, GR and GSH of both plants were decreaced, the contents of TBARS, SOD, POD, CAT, GR and GSH of Ulva prolifera (floating type) and U. linza reached the minimum under100%seawater treatment, and were increased with salinity increasing. With seawater salinity increasing, the APX activities of2Ulvas reached the maximum under300%seawater treatment. The contents of ASA were decreased significantly and reached the minimum under300%seawater treatment.(4) With the seawater salinity increasing, the water contents of2Ulvas were decreased and reached the minimum under100%seawater treatment, and then increased with salinity increasing. Compared with the control, the total sugars, polysaccharides, crude fiber, crude protein contents of two plants were increased with seawater salinity increasing, the total sugars, polysaccharides, crude fiber, crude protein contents of Ulva prolifera (floating type) and U. linza reached the maximum under100%seawater treatment. Compared with control, the trehalose contents of two plants were increased significantly and reached the highest maximum under300%water treatment.In conclusion, we found that Ulva prolifera (Floating type), Ulva prolifera (Fixation type) and Ulva linza all have tolerant ability to salinity changes, but can not survive well under too low or too high salinity, the optimal salinity of Ulva prolifera (Floating type) and Ulva linza was100%seawater, while the optimal salinity of Ulva prolifera (Fixation type) was50%seawater. Ulva prolifera (Floating type) had a wider range of adaption under salinity change than Ulva prolifera (Fixation type) and Ulva linza, and Ulva prolifera (Floating type) had stronger ability to adapt both low-salinity and high-salinity than that of Ulva prolifera (Fixation type) and Ulva linza. The reason is that Ulva prolifera (Floating type) could maintain higher pigment content, photosynthetic level, osmotic adjustment ability, nutrient content and antioxidant levels. Under all salinity, most quality indicators of Ulva prolifera (Floating type) were better than Ulva linza. When cultivating Ulva for food or feed, it should always pay attention to its optimal salinity, high salinity or low salinity conditions could cause the loss of their nutrientions.