Objective:To search for new sources of safe and inexpensive antioxidants,the leaf,root and rhizome of Enhalus acoroides(E.acoroides) were screened for the first time for their antioxidant activities.Methods:Samples of...Objective:To search for new sources of safe and inexpensive antioxidants,the leaf,root and rhizome of Enhalus acoroides(E.acoroides) were screened for the first time for their antioxidant activities.Methods:Samples of leaf,root and rhizome from E.acoroides were tested for total phenolic content,proanthocyanidins and in vitro antioxidant activity in terms of total antioxidant assay,DPPH assay and FRAP assay.Results:The leaf sample was found to have high levels of phenolic(0.323±0.028 mg TAE/g) and proanthocyanidins(0.570 0±0.000 3 mg TAE/g) when compared to root and rhizome.The leaf samples exhibited higher total antioxidant activity (11.770±0.026 mg Ascorbic acid equivalent/g),higher percentage of DPPH radical scavenging activity(25.76±0.04) and higher reducing power(18.060±0.073) in terms of mg GAE/g.In addition, there was a significant correlation between total phenolic content and total antioxidant activity (R^2=0.923),DPPH assay(R^2=0.509).FRAP assay(R^2=0.994).Similarly,significant correlation was found between the proanthocyanidin and total antioxidant activity(R^2=0.977),DPPH assay (R^2=0.464) and the FRAP assay(R^2=0.998).Conclusions:These results suggested that E.acoroides have strong antioxidant potential.Further study is necessary for isolation and characterization of the active antioxidant agents,which can be used to treat various oxidative stress-related diseases.展开更多
A benthic harmful dinoflagellate bloom caused by Prorocentrum concavum occurred at Xincun Bay,a lagoon characterized by a tropical seagrass ecosystem in the southern China,in summer 2018.Both abiotic and biotic factor...A benthic harmful dinoflagellate bloom caused by Prorocentrum concavum occurred at Xincun Bay,a lagoon characterized by a tropical seagrass ecosystem in the southern China,in summer 2018.Both abiotic and biotic factors may affect the abundance dynamics of P.concavum.One of the biotic factors,allelopathy,is known to be especially common among aquatic species and is suggested to be an economical and environmentally-friendly way to eliminate Benthic Harmful Algal Blooms(BHABs).To investigate the possible allelopathic interactions between seagrasses and P.concavum,a field survey was conducted to study the cell densities of P.concavum on four major substrates over 12 months.In laboratory,fresh Enhalus acoroides leaves and a crude aqueous extract of dry E.acoroides leaves were added to the culture of P.concavum respectively to assess possible effects on the growth and photosynthesis activities of P.concavum cells.Our results showed that the average abundance of P.concavum on E.acoroides leaves was statistically lower than that on the sediment outside the seagrass meadow and that on Thalassia hemperichii leaves.Both the growth and photosynthesis activities of P.concavum cells were inhibited in the two experiments,which can be attributed to the release and production of allelochemicals by E.acoroides.Our results offer new insights into the interaction between the submerged seagrass E.acoroides and the benthic harmful algal bloom dinoflagellate P.concavum,which can influence the abundance dynamics of P.concavum and provide an alternative for reducing potential threat of BHABs.展开更多
Seagrass beds degraded significantly since the last century on both, global and local scale. The seagrass species Enhalus acoroides(Linnaeus f.) Royle is a common species found in almost all marine ecosystems includin...Seagrass beds degraded significantly since the last century on both, global and local scale. The seagrass species Enhalus acoroides(Linnaeus f.) Royle is a common species found in almost all marine ecosystems including bays,lagoons and around offshore islands in tropical regions of the West Pacific. It was shown that genetic diversity is an essential indicator of the conditions of ecosystems. In the present study, microsatellite markers were used to assess the genetic diversity and population structure of six distinct seagrass beds along the coast of the Khanh Hoa Province, Vietnam. The results indicate that the genetic diversity of the populations in the open sea is higher than in the lagoon. Seagrass beds occurring in disturbed sites show reduced genetic diversity. The fixing index value(FST) depicts a relatively high genetic structure among populations. Structure analysis clusters the populations into open sea and lagoon populations and cluster analysis and AMOVA indicate a significant difference between the two groups. There are low but non-significant positive correlations between geographic and genetic distances.The different habitats of the open sea and the lagoon are probably responsible for forming two groups.展开更多
During low tide,the intertidal seagrass Enhalus acoroides is often exposed to high light and desiccation,which can seriously threaten its survival,at least partly by inhibiting photosystem Ⅱ(PSⅡ)activity.The respons...During low tide,the intertidal seagrass Enhalus acoroides is often exposed to high light and desiccation,which can seriously threaten its survival,at least partly by inhibiting photosystem Ⅱ(PSⅡ)activity.The response of leaves of E.acoroides to high light and desiccation was compared for seedlings and mature plants.Results show that the resistance of seedling and mature leaves to high light was quite similar,but to desiccation was very different.Seedling leaves were more sensitive to desiccation than the mature plant leaves,but had better water retention.The damage of desiccation to seedling leaves was mainly caused by dehydration,whereas that to mature plant leaves was caused by hypersaline toxicity.The recovery rate of PSⅡ of seedling leaves was significantly slower than that of the mature plants after the stresses disappeared,which may at least partly contribute to seedling mortality in the wild.In addition,compared to high light,desiccation seriously inhibited the recovery rate of PSⅡ activities even if the leaves became fully rehydrated to their normal relative water content(RWC)in the following re-immersion.Desiccation inhibited the recovery rate of RC/CS_(M)(reaction center per cross section(at t=t_(Fm)))to decrease the production of assimilatory power,which maybe the cause of the slower PSⅡ recovery in desiccation treatments.This study demonstrates that desiccation particularly coupling with high light have a very negative ef fect on the PSⅡ of E.acoroides during low tide and the sensitivity of seedlings and mature plants to desiccation is significantly different,which have important reference significance to choose an appropriate transplanting depth where seedlings and mature plants of E.acoroides not only receive sufficient light for growth,but also that minimize desiccation stress during low tide.展开更多
[Objective] This study aimed to investigate the chromosomes and karyotypes of three seagrass species of hydrocharitaceae-Enhalus acoroides, Thalassia hemprichii and Halophila minor collected from Li’an Lagoon, Hainan...[Objective] This study aimed to investigate the chromosomes and karyotypes of three seagrass species of hydrocharitaceae-Enhalus acoroides, Thalassia hemprichii and Halophila minor collected from Li’an Lagoon, Hainan Province, China. [Method] The root-tips of E. acoroides, T. hemprichii and the axillary buds of H. minor were selected as the materials in this study. The conventional crushing method was used to prepare the slice specimens of chromosomes, and the karyotypes of the three species were analyzed. [Result] The chromosome numbers of E. acoroides, T. hemprichii and H. minor were 2n=18, 18, 28, respectively. The karyotype formulas were K （2n）=18= 12m＋6sm, K（2n）=18=12m＋6sm and K（2n）=28=16m＋8sm＋4st, respectively. According to the standard of Stebbins, the karyotypes of E. acoroides and T. hemprichii were 2A, and that of H. minor was 2B. There was no B chromosome and satellite in these three species. [Conclusion] According to the comparison on the karyotypes of this three species, E. acoroides and T. hemprichii are similar in karyotypes to each other, indicating that there is close, inter-relationship between E. acoroides and T. hemprichii.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
文摘Objective:To search for new sources of safe and inexpensive antioxidants,the leaf,root and rhizome of Enhalus acoroides(E.acoroides) were screened for the first time for their antioxidant activities.Methods:Samples of leaf,root and rhizome from E.acoroides were tested for total phenolic content,proanthocyanidins and in vitro antioxidant activity in terms of total antioxidant assay,DPPH assay and FRAP assay.Results:The leaf sample was found to have high levels of phenolic(0.323±0.028 mg TAE/g) and proanthocyanidins(0.570 0±0.000 3 mg TAE/g) when compared to root and rhizome.The leaf samples exhibited higher total antioxidant activity (11.770±0.026 mg Ascorbic acid equivalent/g),higher percentage of DPPH radical scavenging activity(25.76±0.04) and higher reducing power(18.060±0.073) in terms of mg GAE/g.In addition, there was a significant correlation between total phenolic content and total antioxidant activity (R^2=0.923),DPPH assay(R^2=0.509).FRAP assay(R^2=0.994).Similarly,significant correlation was found between the proanthocyanidin and total antioxidant activity(R^2=0.977),DPPH assay (R^2=0.464) and the FRAP assay(R^2=0.998).Conclusions:These results suggested that E.acoroides have strong antioxidant potential.Further study is necessary for isolation and characterization of the active antioxidant agents,which can be used to treat various oxidative stress-related diseases.
基金supported by the National Natural Science Foundation of China(Nos.42076144,41876173)the Special Foundation for National Science and Technology Basic Research Program of China(No.2018FY100200).
文摘A benthic harmful dinoflagellate bloom caused by Prorocentrum concavum occurred at Xincun Bay,a lagoon characterized by a tropical seagrass ecosystem in the southern China,in summer 2018.Both abiotic and biotic factors may affect the abundance dynamics of P.concavum.One of the biotic factors,allelopathy,is known to be especially common among aquatic species and is suggested to be an economical and environmentally-friendly way to eliminate Benthic Harmful Algal Blooms(BHABs).To investigate the possible allelopathic interactions between seagrasses and P.concavum,a field survey was conducted to study the cell densities of P.concavum on four major substrates over 12 months.In laboratory,fresh Enhalus acoroides leaves and a crude aqueous extract of dry E.acoroides leaves were added to the culture of P.concavum respectively to assess possible effects on the growth and photosynthesis activities of P.concavum cells.Our results showed that the average abundance of P.concavum on E.acoroides leaves was statistically lower than that on the sediment outside the seagrass meadow and that on Thalassia hemperichii leaves.Both the growth and photosynthesis activities of P.concavum cells were inhibited in the two experiments,which can be attributed to the release and production of allelochemicals by E.acoroides.Our results offer new insights into the interaction between the submerged seagrass E.acoroides and the benthic harmful algal bloom dinoflagellate P.concavum,which can influence the abundance dynamics of P.concavum and provide an alternative for reducing potential threat of BHABs.
基金The NAFOSTED under contract No.106-NN.02-2014.04the Umbrella of JSPS Core-to-core Program,B.Asia-Africa Science Platforms
文摘Seagrass beds degraded significantly since the last century on both, global and local scale. The seagrass species Enhalus acoroides(Linnaeus f.) Royle is a common species found in almost all marine ecosystems including bays,lagoons and around offshore islands in tropical regions of the West Pacific. It was shown that genetic diversity is an essential indicator of the conditions of ecosystems. In the present study, microsatellite markers were used to assess the genetic diversity and population structure of six distinct seagrass beds along the coast of the Khanh Hoa Province, Vietnam. The results indicate that the genetic diversity of the populations in the open sea is higher than in the lagoon. Seagrass beds occurring in disturbed sites show reduced genetic diversity. The fixing index value(FST) depicts a relatively high genetic structure among populations. Structure analysis clusters the populations into open sea and lagoon populations and cluster analysis and AMOVA indicate a significant difference between the two groups. There are low but non-significant positive correlations between geographic and genetic distances.The different habitats of the open sea and the lagoon are probably responsible for forming two groups.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB42000000)the National Natural Science Foundation of China(No.32071577)+2 种基金the International Partnership Program of Chinese Academy of Sciences(No.GJHZ2039)the Shandong Provincial Natural Science Foundation(No.ZR201911130493)the Taishan Industrial Experts Program(No.Tscy20200102)。
文摘During low tide,the intertidal seagrass Enhalus acoroides is often exposed to high light and desiccation,which can seriously threaten its survival,at least partly by inhibiting photosystem Ⅱ(PSⅡ)activity.The response of leaves of E.acoroides to high light and desiccation was compared for seedlings and mature plants.Results show that the resistance of seedling and mature leaves to high light was quite similar,but to desiccation was very different.Seedling leaves were more sensitive to desiccation than the mature plant leaves,but had better water retention.The damage of desiccation to seedling leaves was mainly caused by dehydration,whereas that to mature plant leaves was caused by hypersaline toxicity.The recovery rate of PSⅡ of seedling leaves was significantly slower than that of the mature plants after the stresses disappeared,which may at least partly contribute to seedling mortality in the wild.In addition,compared to high light,desiccation seriously inhibited the recovery rate of PSⅡ activities even if the leaves became fully rehydrated to their normal relative water content(RWC)in the following re-immersion.Desiccation inhibited the recovery rate of RC/CS_(M)(reaction center per cross section(at t=t_(Fm)))to decrease the production of assimilatory power,which maybe the cause of the slower PSⅡ recovery in desiccation treatments.This study demonstrates that desiccation particularly coupling with high light have a very negative ef fect on the PSⅡ of E.acoroides during low tide and the sensitivity of seedlings and mature plants to desiccation is significantly different,which have important reference significance to choose an appropriate transplanting depth where seedlings and mature plants of E.acoroides not only receive sufficient light for growth,but also that minimize desiccation stress during low tide.
基金Supported by the State key Subjecet of Botany at Hainan University (071001)the Malor Scientific Research Protect of Hainan Province, China(20080137)~~
文摘[Objective] This study aimed to investigate the chromosomes and karyotypes of three seagrass species of hydrocharitaceae-Enhalus acoroides, Thalassia hemprichii and Halophila minor collected from Li’an Lagoon, Hainan Province, China. [Method] The root-tips of E. acoroides, T. hemprichii and the axillary buds of H. minor were selected as the materials in this study. The conventional crushing method was used to prepare the slice specimens of chromosomes, and the karyotypes of the three species were analyzed. [Result] The chromosome numbers of E. acoroides, T. hemprichii and H. minor were 2n=18, 18, 28, respectively. The karyotype formulas were K （2n）=18= 12m＋6sm, K（2n）=18=12m＋6sm and K（2n）=28=16m＋8sm＋4st, respectively. According to the standard of Stebbins, the karyotypes of E. acoroides and T. hemprichii were 2A, and that of H. minor was 2B. There was no B chromosome and satellite in these three species. [Conclusion] According to the comparison on the karyotypes of this three species, E. acoroides and T. hemprichii are similar in karyotypes to each other, indicating that there is close, inter-relationship between E. acoroides and T. hemprichii.
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.
