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Nutrients and temperature are the major elements in maintaining stable endosymbiotic relationships. The mechanisms and response of cultured Symbiodinium cells in the absence of nitrogen, and at various temperatures are still unclear. The present study investigated the influence of different temperatures and nitrogen-deprivation on free-living Symbiodinium cultures. The physiological responses of free-living Symbiodinium cells cultured at different temperatures during nitrogen deprivation under a 12:12 h light:dark were measured. Symbiodinium cell growth was significantly lower in response to lower temperatures. Transmission electron micrographs (TEMs) revealed the formation of lipid droplets induced by nitrogen deprivation under different temperatures. The results of this study will increase our understanding of adaptive responses occurring in Symbiodinium under environmental stress.

To provide a theoretical basis for alpine source lake protection, ten samples were taken from each lake annually from 2012 to 2015. Each year, the various species of nitrogen and phosphorus nutrients were measured. The average contents of nitrate nitrogen, ammonia nitrogen, nitrite nitrogen, total phosphorus, and total nitrogen in the four lakes are 0.195-0.0 mg/L, 0.038-0.143 mg/L, 0.004-0.168 mg/L, 0.006-0.740 mg/L, and 0.050-0.547 mg/L, respectively. The total phosphorus contents in Eling Lake, Longbao Lake and Sea Star were higher than Class I water quality standards, and the total nitrogen contents in Eling Lake, Sea Star and Zhaling Lake were higher than Class I water quality standards as well. The concentration contour maps of the nitrate nitrogen, ammonia nitrogen, nitrite nitrogen, total phosphorus and total nitrogen showed that the indicators of the four lakes in the east, the west, and the center of the lake did not have the same trend. From 2012 to 2015, each of the measured nutrients showed a rising trend year by year. The four lakes are polluted by both endogenous and exogenous pollution, and it is necessary to limit the exogenous pollution and protect the alpine lakes immediately. [ABSTRACT FROM AUTHOR]