Studies On The Iron And Copper Absorption Patterns Of Mineral Elements Of Eelgrass(Zostera Marina L.) And Alleviating Effects Of Iron Addition On The Sulfide Stress Towards Eelgrass Bed

Mineral elements are one of the key factors that affect the survival and growth of seagrasses. In the present study, we investigated firstly the effects of different concentrations of iron and copper on survival, growth and photosynthetic pigment contents of Zostera marina seedlings and young plants under laboratory conditions to determine the optimum concentrations of iron and copper for cultivating eelgrass seedlings and young plants. Secondly, we investigated the iron absorption patterns of above- and underground parts of plants to identify the main iron absorption part of eelgrass. Finally, the effect of different sulfide levels on density fluctuation and growth of plants were studies. Also the alleviating effect of iron addition on sulfur stress towards eelgrass bed was estimated. The findings of the research will provide theoretical basis and scientific foundation to establish the ecological restoration technology of degraded eelgrass beds. The main results were summarized as follows.1. The survival and growth of seedlings and young plants exposed to different iron (500-1500 μg L-1) and coppe (3-50 μg L-1) concentrations were investigated under laboratory conditions. The results showed that the growth parameters of seedlings and young plants exhibited a similar trend, in which survival, morphological parameters and productivity of seedlings and young plants reached the greatest values under low concentrations of copper from 3 to 5 μg L-1. The change of these parameters showed increases firstly and then decreases as the increase in iron concentration with the maximum values under 700 μg L-1. Comprehensive analysis suggested that the demand of copper for seedlings and young plants were very low, so we should pay attention to the copper pollution. But they had high demand for iron and the optimum concentration of iron was 700 μg L-1. The findings of the research will provide information for mineral nutrition of marine higher plant and artificial cultivation of eelgrass seedlings.2. Separate mode of eelgrass plants was constructed in the laboratory, then setted No separated and without iron treatment (NS), separated and without iron treatment (LL), separated and with iron for underground parts of shoots treatment (LH), separated and with iron for aboveground parts of shoots treatment (HL). separated and with iron for above- and underground parts of shoots treatment (HH) were set. The iron concentrations in no iron addition treatments and iron addition treatments are 500 μg L-1 and 700 μg L-1. respectively. Then we investigated the effects of different iron addition treatments on survival, growth and photosynthetic pigment contents of plants to identify the main iron absorption part of eelgrass. The results showed that survival, morphological parameters of new tissues and photosynthetic pigment contents of plants under LH, HL, and HH were significantly higher than those of pants under the NS and LL. Also, survival, morphological parameters of underground parts and productivity of plants under LH were clearly higher than those of plants under HL. Comprehensive analysis suggested that eelgrass plants could absorb iron via the above-and underground parts, but the underground parts were the main absorption tissues. The findings of the research will provide scientific foundation to establish the strategy of artificial forcing breeding under natural conditions.3. We investigated the content of copper and iron in seawater, porewater, sediment and eelgrass plants in Swan Lake in June 2013. The relationship of the content of copper and iron between environments and plants was discussed. The effect of different sulfide levels on density fluctuation and growth of plants was conducted. In the meantime, the alleviating effect of iron addition on sulfur stress (90.6-818.7 μmol L-1) towards eelgrass bed was estimated. The results showed that the content of copper of plants was young leaves> mature leaves> underground parts, and the copper contents of plants was not sensitive to surrounding environmental factors. The iron content of plants was underground parts> mature leaves> young leaves, which was influenced by the content of porewater and sediment. The density fluctuation, morphology parameters of new tissues and productivity of plants were decreased as the increase in sulfide levels with the minimum values under 818.7 μmol L-1. Iron addition under high sulfide concentration could improve the density and growth of plants. However, no obvious influences were found under lower sulfide concentration with the addition of iron. Comprehensive analysis suggested that the iron absorption of eelgrass was influenced by chemical and physical characteristics of sediments. High sulfide concentrations had an obvious negative effects on the growth of eelgrass plants, but iron addition could alleviate the toxicity of sulfide. Also, the effect was enhanced when sulfide concentrations increased. The findings of the research will provide theoretical basis for establishing the strategy of in situ habitat restoration and management for damaged eelgrass beds.