A field survey was performed to examine nonstructural carbohydrate （NSC） dynamics in seagrass Thalassia hemprichii at the Xincun Bay in southern China. An indoor experiment to investigate the response of NSC in T. h...A field survey was performed to examine nonstructural carbohydrate （NSC） dynamics in seagrass Thalassia hemprichii at the Xincun Bay in southern China. An indoor experiment to investigate the response of NSC in T. hemprichiito shade was conducted. Belowground tissue of T. hemprichiiwas the dominant site of NSC reserves, and soluble sugar was the primary storage compound. The starch content of belowground tissue was lower in high intertidal areas than in low intertidal areas, indicating that the longer air exposure in high intertidal areas resulted in less NSC synthesis and less accumulation of NSC in T. hemprichii. The lowest level of soluble sugar and its proportion to NSC in belowground tissue were observed near the cage culture area, where the nutrient concentration in water and sediment was the highest; while the highest level of that was observed near the coastal shrimp farm, where salinity was the lowest. Soluble sugar in belowground tis- sue showed the following trend： summer〉spring〉winter〉autumn. This corresponded to seasonal changes in the intensity of light. Leaf sugar accumulated during the autumn-winter period, providing a carbon and energy source for flower bud formation and seed germination. Short-term shading decreased NSC accumu- lation. Collectively, these results suggest that nutrient enrichment, freshwater discharge and exposure to air affect NSC dynamics in T. hemprichii. Light intensity, flower bud formation, and seed germination were all found to induce seasonal variations in NSC in T. hemprichii.展开更多
This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum ...This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum yield (△F/F′m),photosynthetic pigments and antioxidative enzymes like superoxide dismutase (SOD),guaiacol peroxidase (POD) were also examined.Cadmium was the most highly accumulated metal.Meanwhile,high metals levels led to a remarkable breakdown of photosynthetic parameters.Especially,△F/F′m,chlorophyll and carotenoid were significantly low during prolonged Cu exposure.Besides,△F/F′m was more severely depressed by Cu and Zn than Pb and Cd.However,T.hemprichii had positive response by increasing the activity of SOD and POD.The results indicate that T.hemprichii is the most sensitive to Cu,and the antioxidative protection mechanisms of T.hemprichii are more efficiently activated to avoid damage of Zn,Cd and Pb stress. Finally,due to the high Cd-accumulation and strong Cd-tolerance capacity,T.hemprichii can be used for phytoremediation in Cd-contaminated areas.展开更多
Dissolved organic matter（DOM） represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM ...Dissolved organic matter（DOM） represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon（C）, 70% nitrogen（N） and 38% phosphorus（P） of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon（DOC）, dissolved organic nitrogen（DON） and dissolved organic phosphorus（DOP） of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides（MCHO）, DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/（g·d）. Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON： DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production（the Xincun Bay, South China Sea）, the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter（POM）from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.展开更多
基金supported by UNEP and Global Environment Foundation (No. UNEP/GEF/SCS/Chi/MoU2c)the Key Innovation Project of Chinese Academy of Science ((No. KSCZ2-SW-132)the National Natural Science Foundation of China (No. 40576052 and No. U0633007)
基金The National Natural Science Foundation of China under contract Nos 41076069 and 40776086the Project of Environmental Quality Evaluation of Seagrass Bed in South China Sea under contract No. DOMEP (MEA)-01-03+1 种基金the Public Science and Technology Research Funds Projects of Ocean under contract No. 201305030the Knowledge Innovation Program of the Chinese Academy of Sciences under contract No. SQ201219
文摘A field survey was performed to examine nonstructural carbohydrate （NSC） dynamics in seagrass Thalassia hemprichii at the Xincun Bay in southern China. An indoor experiment to investigate the response of NSC in T. hemprichiito shade was conducted. Belowground tissue of T. hemprichiiwas the dominant site of NSC reserves, and soluble sugar was the primary storage compound. The starch content of belowground tissue was lower in high intertidal areas than in low intertidal areas, indicating that the longer air exposure in high intertidal areas resulted in less NSC synthesis and less accumulation of NSC in T. hemprichii. The lowest level of soluble sugar and its proportion to NSC in belowground tissue were observed near the cage culture area, where the nutrient concentration in water and sediment was the highest; while the highest level of that was observed near the coastal shrimp farm, where salinity was the lowest. Soluble sugar in belowground tis- sue showed the following trend： summer〉spring〉winter〉autumn. This corresponded to seasonal changes in the intensity of light. Leaf sugar accumulated during the autumn-winter period, providing a carbon and energy source for flower bud formation and seed germination. Short-term shading decreased NSC accumu- lation. Collectively, these results suggest that nutrient enrichment, freshwater discharge and exposure to air affect NSC dynamics in T. hemprichii. Light intensity, flower bud formation, and seed germination were all found to induce seasonal variations in NSC in T. hemprichii.
基金The Chinese Nature Science Foundation (CNSF) Project under contract Nos 40776086 and 41076069Forefront Program of the Knowledge Innovation Project,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No. LYQY200706the National 908 Special Project under contract No. GD908-02-08
文摘This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum yield (△F/F′m),photosynthetic pigments and antioxidative enzymes like superoxide dismutase (SOD),guaiacol peroxidase (POD) were also examined.Cadmium was the most highly accumulated metal.Meanwhile,high metals levels led to a remarkable breakdown of photosynthetic parameters.Especially,△F/F′m,chlorophyll and carotenoid were significantly low during prolonged Cu exposure.Besides,△F/F′m was more severely depressed by Cu and Zn than Pb and Cd.However,T.hemprichii had positive response by increasing the activity of SOD and POD.The results indicate that T.hemprichii is the most sensitive to Cu,and the antioxidative protection mechanisms of T.hemprichii are more efficiently activated to avoid damage of Zn,Cd and Pb stress. Finally,due to the high Cd-accumulation and strong Cd-tolerance capacity,T.hemprichii can be used for phytoremediation in Cd-contaminated areas.
基金The National Basic Research Program of China under contract Nos 2015CB452905 and 2015CB452902the National Natural Science Foundation of China under contract No.41730529the National Specialized Project of Science and Technology under contract No.2015FY110600
文摘Dissolved organic matter（DOM） represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon（C）, 70% nitrogen（N） and 38% phosphorus（P） of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon（DOC）, dissolved organic nitrogen（DON） and dissolved organic phosphorus（DOP） of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides（MCHO）, DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/（g·d）. Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON： DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production（the Xincun Bay, South China Sea）, the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter（POM）from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.
基金Supported by the State key Subjecet of Botany at Hainan University (071001)the Malor Scientific Research Protect of Hainan Province, China(20080137)~~
