Seagrass Thalassia Hemprichii Research Articles

The metabolic network response and tolerance mechanism of Thalassia hemprichii under high sulfide based on widely targeted metabolome and transcriptome

Costal eutrophication leads to increased sulfide levels in sediments, which has been identified as a major cause of the global decline in seagrass beds. The seagrass Thalassia hemprichii, a dominant tropical species in the Indo-Pacific, is facing a potential threat from sulfide, which can be easily reduced from sulfate in porewater under the influence of global climate change and eutrophication. However, its metabolic response and tolerance mechanisms to high sulfide remain unclear. Thus, the current study investigated the physiological responses and programmed metabolic networks of T. hemprichii through a three-week mesocosm experiment, integrating physiology, stable isotope, widely targeted metabolomics, transcriptomics, and microbial diversity assessments. High sulfide reduced the sediment microbial diversity, while increased sediment sulfate reduced bacterial abundance and δ34S. The exposure to sulfide enhanced root δ34S while decreased leaf δ34S in T. hemprichii. High sulfide was shown to inhibit photosynthesis via damaging PSII, which further reduced ATP production. In response, abundant up-regulated differentially expressed genes in energy metabolism, especially in oxidative phosphorylation, were activated to compensate high energy requirement. High sulfide also promoted autophagy by overexpressing the genes related to phagocytosis and phagolysosome. Meanwhile, metabolomic profiling revealed that the contents of many primary metabolites, such as carbohydrates and amino acids, were reduced in both leaves and roots, likely to provide more energy and synthesize stress-responsive secondary metabolites. Genes related to nitrate reduction and transportation were up-regulated to promote N uptake for sulfide detoxification. High sulfide levels specifically enhanced thiamine in roots, while increased jasmonic acid and flavonoid levels in leaves. The distinct differences in metabolism between roots and leaves might be related to sulfide levels and the growth-defense trade-off. Collectively, our work highlights the specific mechanisms underlying the response and tolerance of T. hemprichii to high sulfide, providing new insights into seagrass strategies for resisting sulfide.

Isolation and Identification of Endophytic Bacteria from Seagrass Thalassia hemprichii as Antibacterial Producer

Isolation and Identification of Endophytic Bacteria from Seagrass Thalassia hemprichii as Antibacterial Producer

Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification

Seagrass meadows play vital ecological roles in the marine ecosystem. Global climate change poses considerable threats to seagrass survival. However, it is unclear how seagrass and its associated bacteria will respond under future complex climate change scenarios. This study explored the effects of ocean warming (+2 °C) and ocean acidification (−0.4 units) on seagrass physiological indexes and bacterial communities (sediment and rhizosphere bacteria) of the seagrass Thalassia hemprichii during an experimental exposure of 30 days. Results demonstrated that the synergistic effect of ocean warming and ocean acidification differed from that of one single factor on seagrass and the associated bacterial community. The seagrass showed a weak resistance to ocean warming and ocean acidification, which manifested through the increase in the activity of typical oxidoreductase enzymes. Moreover, the synergistic effect of ocean warming and ocean acidification caused a significant decrease in seagrass's chlorophyll content. Although the bacterial community diversity exhibited higher resistance to ocean warming and ocean acidification, further bacterial functional analysis revealed the synergistic effect of ocean warming and ocean acidification led to significant increases in SOX-related genes abundance which potentially supported the seagrass in resisting climate stress by producing sulfates and oxidizing hydrogen sulfide. More stable bacterial communities were detected in the seagrass rhizosphere under combined ocean warming and ocean acidification. While for one single environmental stress, simpler networks were detected in the rhizosphere. In addition, the observed significant correlations between several modules of the bacterial community and the physiological indexes of the seagrass indicate the possible intimate interaction between seagrass and bacteria under ocean warming and ocean acidification. This study extends our understanding regarding the role of seagrass associated bacterial communities and sheds light on both the prediction and preservation of the seagrass meadow ecosystems in response to global climate change.

Strong Genetic Structure and Limited Gene Flow among Populations of the Tropical Seagrass Thalassia hemprichii in the Philippines

Seagrasses are marine angiosperms, and seagrass beds maintain the species diversity of tropical and subtropical coastal ecosystems. For proper understanding, management and conservation of coastal ecosystems, it is essential to understand seagrass population dynamics. Population genetic studies can cover large geographic scales and contribute to a comprehensive understanding of reproductive dynamics and potential dispersal among locations. The clonal and genetic diversity and genetic connectivity of Thalassia hemprichii in the Philippines were estimated by a population genetics approach. The geographic scale of this study has a direct distance of approximately 1600 km. Although high clonal diversity was found in some sites (R = 0.07–1.00), both sexual and asexual reproduction generally maintains separate populations. Genetic diversity is not definitely correlated with latitude, and genetic differentiation is significant in all pairs of sites (FST = 0.026–0.744). Complex genetic structure was found in some regions, even at a fine geographic scale. The migration of fruits and seedlings was elucidated as an infrequent and stochastic event. These results suggest the necessity for the conservation of this species due to a deficiency in migrants from external regions.

Assessing the Effects of Ocean Warming and Acidification on the Seagrass Thalassia hemprichii

Seagrass beds serve as important carbon sinks, and it is thought that increasing the quantity and quality of such sinks could help to slow the rate of global climate change. Therefore, it will be important to (1) gain a better understanding of seagrass bed metabolism and (2) document how these high-productivity ecosystems are impacted by climate change-associated factors, such as ocean acidification (OA) and ocean warming (OW). A mesocosm-based approach was taken herein in which a tropical, Western Pacific seagrass species Thalassia hemprichii was cultured under either control or OA-simulating conditions; the temperature was gradually increased from 25 to 31 °C for both CO2 enrichment treatments, and it was hypothesized that this species would respond positively to OA and elevated temperature. After 12 weeks of exposure, OA (~1200 ppm) led to (1) increases in underground biomass and root C:N ratios and (2) decreases in root nitrogen content. Rising temperatures (25 to 31 °C) increased the maximum quantum yield of photosystem II (Fv:Fm), productivity, leaf growth rate, decomposition rate, and carbon sequestration, but decreased the rate of shoot density increase and the carbon content of the leaves; this indicates that warming alone does not increase the short-term carbon sink capacity of this seagrass species. Under high CO2 and the highest temperature employed (31 °C), this seagrass demonstrated its highest productivity, Fv:Fm, leaf growth rate, and carbon sequestration. Collectively, then, it appears that high CO2 levels offset the negative effects of high temperature on this seagrass species. Whether this pattern is maintained at temperatures that actually induce marked seagrass stress (likely beginning at 33–34 °C in Southern Taiwan) should be the focus of future research.

Biochar Addition Altered Bacterial Community and Improved Photosynthetic Rate of Seagrass: A Mesocosm Study of Seagrass Thalassia hemprichii.

Seagrass meadows, as typical “blue carbon” ecosystems, play critical ecological roles in the marine ecosystem and decline every year. The application of biochar in soil has been proposed as a potential soil amendment to improve soil quality and mitigate global climate change. The effects of biochar on soil bacterial activities are integrally linked to the potential of biochar in achieving these benefits. However, biochar has been rarely applied in marine ecosystems. Whether the application of biochar could work on the seagrass ecosystem remained unknown. In this study, we investigated the responses of sediment and rhizosphere bacterial communities of seagrass Thalassia hemprichii to the biochar addition derived from maize at ratios of 5% by dry weight in the soil during a one-month incubation. Results indicated that the biochar addition significantly changed the sedimental environment with increasing pH, total phosphorus, and total kalium while total nitrogen decreased. Biochar addition significantly altered both the rhizosphere and sediment bacterial community compositions. The significant changes in rhizosphere bacterial community composition occurred after 30days of incubation, while the significant variations in sediment bacterial community composition distinctly delayed than in sediment occurred on the 14th day. Biochar application improved nitrification and denitrification, which may accelerate nitrogen cycling. As a stabilizer to communities, biochar addition decreased the importance of deterministic selection in sediment and changed the bacterial co-occurrence pattern. The biochar addition may promote seagrass photosynthesis and growth by altering the bacterial community compositions and improving nutrient circulation in the seagrass ecosystem, contributing to the seagrass health improvement. This study provided a theoretical basis for applying biochar to the seagrass ecosystem and shed light on the feasible application of biochar in the marine ecosystem. Graphical

High rates of herbivory in remote northwest Australian seagrass meadows by rabbitfish and green turtles

Herbivory is a key ecological process that often determines the composition and abundance of plants. Estimates of herbivory in seagrass meadows are typically lower than those in other vegetated coastal ecosystems, but herbivory can be intense when large herbivorous vertebrates are abundant. We surveyed rates of herbivory on 2 species of tropical seagrasses (Thalassia hemprichii and Enhalus acoroides), the abundance of herbivorous vertebrates, and the diet of 2 abundant herbivorous vertebrates (the green turtle Chelonia mydas and the rabbitfish Siganus lineatus) in lagoons adjacent to remote islands off northwestern Australia. Rates of herbivory in some deployments of tethered seagrass were more than 1000 times higher than rates of production and were among the highest recorded. Consumption exceeded production in half the deployments (9 of 18). Remote underwater video revealed that S. lineatus was the most abundant herbivore. Stomachs of S. lineatus contained mostly seagrass, and models based on stable isotopes indicated that seagrass was the primary source of nutrition. Stomach contents of C. mydas were more variable, containing seagrass and macroalgae (although the sample size was low), but models based on stable isotopes indicated that seagrass was likely the primary source of nutrition. Multiple lines of evidence suggest that the high rates of herbivory on the seagrasses T. hemprichii and E. acoroides are mainly due to direct consumption by the abundant S. lineatus, and perhaps also C. mydas. Seagrass is the primary contributor to the nutrition of both species.

Optimization of Extraction Condition to Obtain Antioxidant Activity and Total Phenolic Content of Seagrass Thalassia hemprichii (Ehrenb.) Asch from Indonesia

Background: Thalassia hemprichii (Ehrenb.) Asch is one of the commonly found seagrasses spread over the coast of Indonesia and has not been utilized. Previous studies have reported its potency as an antioxidant, however, studies on optimal extraction conditions using ethanol as a solvent to obtain higher antioxidant activity are still limited. Objective: The purpose of this study is to optimize the extraction condition for obtaining the highest antioxidant activity and total phenolic content of the seagrass T. hemprichii. In an addition, percentage yield of extract was also evaluated. Methods: In this study, factorial design with independent factors of ethanol concentrations (50%, 70%, and 100%), the use of HCl 1 N (Yes/No), and temperature (300C, 600C) was developed. The analysis of variance (ANOVA) was used to determine the significance of the above factors towards antioxidant activity and total phenolic content. The antioxidant activity was evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and the total phenolic content was determined by Folin-Ciocalteu method. Results: The highest antioxidant activity (IC50=83.48 μg/mL) was shown in sample R1 (extracted with 50% ethanol, added with HCl 1 N, and 600C). The sample was also showed total phenolic content 41.03 mg GAE per gram and 22% yield extract. Among the factors examined, the used of HCl 1 N showed the most significant effect to the antioxidant activity and the total phenolic content, with the p-value of 0.048 and 0.034 respectively (p<0.05). Conclusion: This extraction condition can be applied to obtain higher antioxidant activity and total phenolic content from the plant.

Seagrass Thalassia hemprichii Biomass in Waleo Waters, Kema District, Minahasa Utara Regency

This study was aimed at knowing the aquati environmental condition, the fresh weight and ry weight of root, rhizome, and leaf of Thalassia hemprichii, and the ratio of seagrass biomass of Thalassia hemprichii with sampling sites.It was done in Waleo waters, Kema district, Minahasa Utara regency. Data collection used 50×50 cm quadrat, and each T. hemprichii in the quadrat was removed. Water temperature and salinity were measured. Each study site was photographed.This study was done at the lowest tide in 3 locations, near mangrove forest, in the seagrass bed, and coral reefs. Seagrass samples were put in separated plastic bags with location, placed in the cool box, ans brought to the laboratory for further analysis. The samples were cleansed and put in the alcohol-containing plastic bag. Then, the samples were dried and weighed. Results showed that the highest biomass occurred in root, then leaf, and rhizome for all study sites. Keywords: seagrass, biomass, Thalassia hemprichii. ABSTRAKTujuan Penelitian adapun tujuan penelitian ini yaitu untuk mengetahui kondisi lingkungan perairan di lokasi penelitian, untuk mengetahui berapa besar berat basah dan berat kering dari bagian-bagian (akar, rhizoma, dan daun) dari lamun Thalassia hemprichii, untuk mengetahui perbandingan biomassa dari lamun Thalassia hemprichii berdasarkan masing-masing stasiun pengambilan sampel. Penelitian ini dilaksanakan di Perairan Waleo Kecamatan Kema Minahasa Utara. Pengambilan data menggunakan kuadaran 50×50 cm, dan setiap lamun Thalassia hemprichii di dalam kuadran dicabut. Suhu dan salnitas air juga diukur. Lokasi penelitian diambil gambar bawah air. Pengambilan sampel dilakukan pada saat surut terrendah dekat hutan mangrove, di hamparan lamunn dan daerah terumbu karang. Sampel lamun dimasukan ke dalam plastik di pisahkan sesuai sub lokasi, sampel di masukan kedalam cool box dan di bawah ke laboratorium untuk di teliti. Lamun dicuci bersih menggunakan air bersih dan diisi dalam plastik sampel dengan memakai alkohol. Lamun di bawah ke laboratorium akan di keringkan dan ditimbang. Hasil biomassa lamun Thalassia hemprichii di lokasi penelitian menunjukkan bahwa biomassa tertinggi terdapat pada akar, kemudian daun, dan batang.Kata Kunci : Lamun, Biomassa, Thalassia hemprichii.

Phytotoxic effects of Cu, Cd and Zn on the seagrass Thalassia hemprichii and metal accumulation in plants growing in Xincun Bay, Hainan, China.

Seagrasses play an important role in coastal marine ecosystems, but they have been increasingly threatened by human activities. In recent years, seagrass communities have rapidly degenerated in the coastal marine ecosystems of China. To identify the reasons for the decline in seagrasses, the phytotoxic effects of trace metals (Cu, Cd and Zn) on the seagrass Thalassia hemprichii were investigated, and the environmental contents of the metals were analyzed where the seagrass grows. The results showed that leaf necrosis in T. hemprichii exposed to 0.01-0.1 mg L-1 of Cu2+ for 5 days was more serious than that in plants exposed to the same concentrations of Cd2+ and Zn2+. The chlorophyll content in T. hemprichii declined in a concentration-dependent manner after 5 days of exposure to Cu2+, Cd2+ and Zn2+. The evident reduction in ΔF/Fm' in T. hemprichii leaves was observed at day 1 of exposure to 0.01-1.0 mg L-1 of Cu2+ and at day 3 of exposure to 0.1-1.0 mg L-1 of Cd2+. The antioxidant enzyme activities (SOD, POD and CAT) in T. hemprichii leaves exposed to the three metal ions also showed significant changes. In seawater from Xincun Bay (Hainan, China), where T. hemprichii grows, Cu had reached a concentration (i.e., 0.01 mg L-1) that could significantly reduce chlorophyll content and ΔF/Fm' in T. hemprichii leaves. Our results indicate that Cu influences the deterioration of seagrasses in Xincun Bay.

Bioaktivitas Antibakteri Lamun Thalassia hemprichii dan Enhalus acoroides

The objective of present study was to identify bioactivity of antibacterial Indonesian Seagrass Thalassia hemprichii dan Enhalus acoroides from Karang Tirta Beach, Padang City, West Sumatera. This is a preliminary research for a new alternative antibiotic from Seagrass in Indonesia. In this study the seagrass was examined by a maceration process and using the rotary evaporator to obtain viscous extract. The material for the bioactivity testing was performed upon several intended bacteria such as Escherichia coli, Stapillococcus aureus, and Bacillus subtilis. The bioactivity testing was performed by using the method of resazurin and MIC (Minimum Inhibitory Concentration), which is determined by looking at well blue-colored at the smallest concentration. The result revealed that the best antibacterial bioactivity of Thalassia hemprichii extract was a total of 62.50 μg/mL N-hexane solvent against Escherichia coli and Stapillococcus aureus bacteria. While the best antibacterial bioactivity of Enhalus acoroides extract is 15.62 μg/mL of N-hexane solvent against Stapillococcus aureus.

Community Composition and Transcriptional Activity of Ammonia-Oxidizing Prokaryotes of Seagrass Thalassia hemprichii in Coral Reef Ecosystems.

Seagrasses in coral reef ecosystems play important ecological roles by enhancing coral reef resilience under ocean acidification. However, seagrass primary productivity is typically constrained by limited nitrogen availability. Ammonia oxidation is an important process conducted by ammonia-oxidizing archaea (AOA) and bacteria (AOB), yet little information is available concerning the community structure and potential activity of seagrass AOA and AOB. Therefore, this study investigated the variations in the abundance, diversity and transcriptional activity of AOA and AOB at the DNA and transcript level from four sample types: the leaf, root, rhizosphere sediment and bulk sediment of seagrass Thalassia hemprichii in three coral reef ecosystems. DNA and complementary DNA (cDNA) were used to prepare clone libraries and DNA and cDNA quantitative PCR (qPCR) assays, targeting the ammonia monooxygenase-subunit (amoA) genes as biomarkers. Our results indicated that the closest relatives of the obtained archaeal and bacterial amoA gene sequences recovered from DNA and cDNA libraries mainly originated from the marine environment. Moreover, all the obtained AOB sequences belong to the Nitrosomonadales cluster. Nearly all the AOA communities exhibited higher diversity than the AOB communities at the DNA level, but the qPCR data demonstrated that the abundances of AOB communities were higher than that of AOA communities based on both DNA and RNA transcripts. Collectively, most of the samples shared greater community composition similarity with samples from the same location rather than sample type. Furthermore, the abundance of archaeal amoA gene in rhizosphere sediments showed significant relationships with the ammonium concentration of sediments and the nitrogen content of plant tissue (leaf and root) at the DNA level (P < 0.05). Conversely, no such relationships were found for the AOB communities. This work provides new insight into the nitrogen cycle, particularly nitrification of seagrass meadows in coral reef ecosystems.

Reproductive organ characteristics and phenology of a seagrass Thalassia hemprichii (Ehrenberg) Ascherson in the Andaman Sea, Thailand

Reproductive organ characteristics and phenology of a seagrass Thalassia hemprichii (Ehrenberg) Ascherson in the Andaman Sea, Thailand

English

Eight seaweed species in Teluk Kemang and three seagrass species in Teluk Pelanduk, Port Dickson, respectively, were screened for antibacterial activities. The antibacterial activities were screened using disc diffusion test, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against six aquacultural pathogens strains Aeromonas hydrophila ATCC35654, Vibrio harveyi BB120, Vibrio harveyi ATCC14126, Vibrio alginolyticus ATCC17749, Vibrio parahaemolyticus ATCC17803 and Vibrio anguillarum ATCC43313. The results showed that among all the pathogens, seaweed Padina minor and seagrass Thalassia hemprichii had the strongest antibacterial activity against Vibrio harveyi BB120 and Vibrio harveyi ATCC14126, respectively. The lowest values for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were obtained from Padina minor against V. harveyi BB120 and Thalassia hemprichii against V. harveyi ATCC14126, respectively. The findings suggested that seaweed and seagrass in Port Dickson coastal water have the potential to prevent bacterial diseases particularly in aquaculture.

Illumina-based analysis the microbial diversity associated with Thalassia hemprichii in Xincun Bay, South China Sea.

In order to increase our understanding of the microbial diversity associated with seagrass Thalassia hemprichii in Xincun Bay, South China Sea, 16S rRNA gene was identified by highthrough sequencing method. Bacteria associated with seagrass T. hemprichii belonged to 37 phyla, 99 classes. The diversity of bacteria associated with seagrass was similar among the geographically linked coastal locations of Xincun Bay. Proteobacteria was the dominant bacteria and the α-proteobacteria had adapted to the seagrass ecological niche. As well, α-proteobacteria and Pseudomonadales were associated microflora in seagrass meadows, but the interaction between the bacteria and plant is needed to further research. Burkholderiales and Verrucomicrobiae indicated the influence of the bay from anthropogenic activities. Further, Cyanobacteria could imply the difference of the nutrient conditions in the sites. γ-proteobacteria, Desulfobacterales and Pirellulales played a role in the cycle of sulfur, organic mineralization and meadow ecosystem, respectively. In addition, the less abundance bacteria species have key functions in the seagrass meadows, but there is lack knowledge of the interaction of the seagrass and less abundance bacteria species. Microbial communities can response to surroundings and play key functions in the biochemical cycle.

Development of multiplex microsatellite PCR panels for the seagrass Thalassia hemprichii (Hydrocharitaceae).

• Premise of the study: New microsatellites were developed for the seagrass Thalassia hemprichii (Hydrocharitaceae), a long-lived seagrass species that is found throughout the shallow waters of tropical and subtropical Indo-West Pacific. Three multiplex PCR panels were designed utilizing new and previously developed markers, resulting in a toolkit for generating a 16-locus genotype.• Methods and Results: Through the use of microsatellite enrichment and next-generation sequencing, 16 new, validated, polymorphic microsatellite markers were isolated. Diversity was between two and four alleles per locus totaling 36 alleles. These markers, plus previously developed microsatellite markers for T. hemprichii and T. testudinum, were tested for suitability in multiplex PCR panels.• Conclusions: The generation of an easily replicated suite of multiplex panels of codominant molecular markers will allow for high-resolution and detailed genetic structure analysis and clonality assessment with minimal genotyping costs. We suggest the establishment of a T. hemprichii primer convention for the unification of future data sets.

A New 8-Hydroxy Flavone O-Xyloside Sulfate and Antibacterial Activity from the Egyptian Seagrass Thalassia hemprichii

A new 8-hydroxy flavone O-xyloside sulfate, isoscutellarein 7-O-β-xyloside-2′′-O-sulfate, along with four known metabolites, were isolated and identified from seagrass, Thalassia hemprichii, collected from the Egyptian Red sea coast. The structures of the isolated compounds were established by chemical degradation and spectral analysis. The crude extract and the new compound displayed different potent antimicrobial activity against both Gram-positive and Gram-negative bacteria as well as fungi with MIC ranging from 0.1 to 10 μg/mL.

Optimalizatiom use of Seagrass Leafs Thalassia hemprichii As Natural Antioksidan Source

Seagrass is a wealth of marine resources, one of the ecosystems found in coastal areas, able to produce a variety of secondary metabolites, and one water plant that has important benefits that can replace natural source of antioxidants that seagrass (seagrass). Seagrasses are flowering plants (Angiospermae) who can adjust himself to life in the sea water. The purpose of this study was to determine the antioxidant potential in seagrass leaves. Extraction using maceration with the way the samples were stored by using the solvent n-hexane, ethyl acetate and methanol for each 1x24 hours after it evaporated with a vacuum rotary evaporimeter to obtain a crude extract, then extract tested by using antioxidant aktvitas diphenilpycrylhydrazil (DPPH). Antioxidant activity test carried out by the ability of the samples used in reducing the stable free radical diphenilpycrylhydrazil (DPPH). Three milliliters diphenilpycrylhydrazil (DPPH) as a positive control was weighed and added to methanol with a ratio of 1:3. An additional 2 mg of DPPH was diluted with 50 mL of methanol and added at each 1 mL to 3 mL of methanol at a concentration of 75 ppm, 125 ppm and 175 ppm. DPPH mixture is homogenized and rested for 30 minutes. Antioxidant activity assay on leaf Seagrass Thalassia hemprichii showed that the IC50 value of 25.98344501. This value indicates that the samples tested were able to inhibit the free radicals are very strong. Samples containing great potential in the utilization as a source of natural antioxidants Keywords : Extraction, Maceration, Antioxidant, DPPH

Detection of Phytochelatin and Glutathione in Seagrass Thalassia hemprichii as a Detoxification Mechanism Due to Lead Heavy Metal Exposure

Seagrass Thalassia hemprichii is used to study lead (Pb) metal accumulation and synthesis of phytochelatin (PC) and glutathione (GSH) as defense mechanisms against lead toxicity. The plants were exposed by lead (Pb (NO 3 ) 2 ) metal in some concentrations (0, 5, 15 and 25 ppm) for some periods of time (1, 2, 3 and 4 weeks). The contents of lead (Pb), phytochelatin (PC) and glutathione (GSH) are analyzed in leaf and root tissue. Lead accumulation in seagrass depends on the greatness of metal concentration and length of exposure time where the root accumulates lead higher than the leaf. Glutathione is produced higher in the root during lead exposure, while phytochelatin is produced in week 1 and 2. Then, production of phytochelatin turns to higher in the leaf in week 3, although it decreases in week 4. Phytochelatin and glutathione are formed at different retention time in UPLC, when glutathione content is formed earlier and lower than phytochelatin. The study not only reveals that content formation of phytochelatin (PC) and glutathione (GSH) occurs to respond Pb metal, but also shows that production of PC and GSH correlates significantly to Pb metal accumulation in the root and leaf of T. hemprichii . Therefore, in short, formation of PC and GSH, for sure, is a part of defense mechanisms conducted by seagrass T. hemprichii to protect itself against Pb metal toxicity.

Physiological responses of the seagrass Thalassia hemprichii (Ehrenb.) Aschers as indicators of nutrient loading

To select appropriate bioindicators for the evaluation of the influence of nutrients from human activities in a Thalassia hemprichii meadow, environmental variables and plant performance parameters were measured in Xincun Bay, Hainan Island, South China. Nutrient concentrations in the bay decreased along a gradient from west to southeast. Moreover, the nutrients decreased with an increase in the distance from the shore on the southern side of the bay. Among the candidate indicators, the P content of the tissues closely mirrored the two nutrient loading gradients. The epiphytic algae biomass and the N content in the tissues mirrored one of the two nutrient loading trends. The leaf length, however, exhibited a significant negative correlation with the nutrient gradients. We propose that changes in the P content of T. hemprichii, followed by epiphytic algae biomass and N content of the tissues, may be the useful indicators of nutrient loading to coastal ecosystems.