Ecological effects of co-culturing the sea cucumber Apostichopus japonicus with the Chinese white shrimp Fenneropenaeus chinensis in an earthen pond

Using net enclosures in an earthen pond, we established three culture treatments with the sea cucumber Apostichopus japonicus and the Chinese white shrimp Fenneropenaeus chinensis : monoculture of sea cucumbers(C), monoculture of shrimp(S), and co-culture of the two species(CS). We measured levels of suspended particulate matter in the water column; total organic matter, total organic carbon, total nitrogen, and carbon/nitrogen ratios in both settling particles and the sediment; and chlorophyll a levels in the sediment. We then compared these variables between the three treatments. We also examined growth, survival, and yield of the two species in the different treatments. From June to September, the mean monthly suspended particulate matter sedimentation rates in the CS and S treatments were significantly( P 0.05) greater than those in the C treatment. From August to November, the mean monthly total organic matter, total organic carbon, total nitrogen, and chlorophyll a contents in the sediment in the CS and S treatments were significantly( P 0.05) greater than those in the C treatment. Final wet weight, specific growth rate, survival rate, and total yield of sea cucumbers in co-culture were all significantly greater than those of sea cucumbers in monoculture. There were no significant differences among any of these variables for shrimp reared in the two systems. The bioturbation of the sediment and fecal production of the shrimp likely supplied natural food for the sea cucumbers. Co-culture of the two species is a viable option for increasing yield per unit area, maximizing use of the water body, and diversifying crop production.     

CARBON CYCLE IN SHRIMP POLYCULTURE MESOCOSM

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Ecological effects of co-culturing the sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> with the Chinese white shrimp <Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis> in an earthen pond

Using net enclosures in an earthen pond, we established three culture treatments with the sea cucumber Apostichopus japonicus and the Chinese white shrimp Fenneropenaeus chinensis: monoculture of sea cucumbers (C), monoculture of shrimp (S), and co-culture of the two species (CS). We measured levels of suspended particulate matter in the water column; total organic matter, total organic carbon, total nitrogen, and carbon/nitrogen ratios in both settling particles and the sediment; and chlorophyll a levels in the sediment. We then compared these variables between the three treatments. We also examined growth, survival, and yield of the two species in the different treatments. From June to September, the mean monthly suspended particulate matter sedimentation rates in the CS and S treatments were significantly (P<0.05) greater than those in the C treatment. From August to November, the mean monthly total organic matter, total organic carbon, total nitrogen, and chlorophyll a contents in the sediment in the CS and S treatments were significantly ( P <0.05) greater than those in the C treatment. Final wet weight, specific growth rate, survival rate, and total yield of sea cucumbers in co-culture were all significantly greater than those of sea cucumbers in monoculture. There were no significant differences among any of these variables for shrimp reared in the two systems. The bioturbation of the sediment and fecal production of the shrimp likely supplied natural food for the sea cucumbers. Co-culture of the two species is a viable option for increasing yield per unit area, maximizing use of the water body, and diversifying crop production.     

Distribution and accumulation of soil carbon in temperate wetland,northeast China

Estimating carbon sequestration and nutrient accumulation rates in Northeast China are important to assess wetlands function as carbon sink buffering greenhouse gas increasing in North Asia. The objectives of this study were to estimate accreting rates of carbon and nutrients in typical temperate wetlands. Results indicated that average soil organic carbon(SOC), total nitrogen(TN) and total phosphorus(TP) contents were 37.81%, 1.59% and 0.08% in peatlands, 5.33%, 0.25% and 0.05% in marshes, 2.92%, 0.27% and 0.10% in marshy meadows, respectively. Chronologies reconstructed by 210 Pb in the present work were acceptable and reliable, and the average time to yield 0–40 cm depth sediment cores was 150 years. Average carbon sequestration rate(Carbonsq), nitrogen and phosphorus accumulation rates were 219.4 g C/(m~2·yr), 9.16 g N/(m~2·yr) and 0.46 g P/(m~2·yr) for peatland; 57.13 g C/(m~2·yr), 5.42 g N/(m~2·yr) and 2.16 g P/(m~2·yr) for marshy meadow; 78.35 g C/(m~2·yr), 8.70 g N/(m~2·yr) and 0.71 g P/(m2·yr) for marshy; respectively. Positive relations existed between Carbonsq with nitrogen and precipitations, indicating that Carbonsq might be strengthened in future climate scenarios.     

Effect of co-culture of Chinese shrimp (<Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis>) and sea cucumber (<Emphasis Type="Italic">Apostichopus japonicus</Emphasis> Selenka) on pond environment

Monoculture of sea cucumber (pond S) and polyculture of shrimp with sea cucumber (pond SS) were established to evaluate the effect of shrimp on the environmental conditions of sea cucumber farming pond. Contributions of sediment organic matter (SOM2) resuspended from benthic sediment and the suspended particulate organic matter (SPOM) deposited from the water column to the precipitated organic matter (SOM1) collected with sediment traps were estimated with carbon stable isotope analysis. The results showed that the levels of SPOM and SOM2 in pond SS significantly decreased in comparison with those in pond S at the end of experiment (P < 0.05), indicating that co-culturing shrimp in sea cucumber farming pond could purify the farming water. Carbon stable isotope analysis showed that the proportion of SOM2 in SOM1 in pond SS (84.97% ± 0.38%) was significantly lower than that in pond S (95.20% ± 0.30%) (P < 0.05), suggesting that the resuspension of organic matter from benthic sediment into overlying water was reduced in polyculture pond. In contrast, the proportion of SPOM in SOM1 in pond SS (15.03% ± 0.38%) was significantly higher than that in pond S (4.80% ± 0.30%) (P < 0.05), indicating that the sedimentation of SPOM from water column was enhanced in pond SS owing to the biodeposition effect of shrimp.     

Chronology and nutrients change in recent sediment of Taihu Lake,lower Changjiang River Basin,east China

Two short sediment cores named ZS and THS dated by the 210Pb or 137Cs method were collected from the northwest and southwest of Taihu Lake respectivly,and total organic carbon(TOC) and nutrients including total nitrogen(TN) and total phosphorus(TP) were determined to analyze the chronology and nutrients change in recent sediment.The results show that 137Cs activities are low(less than 15 Bq/kg) in the two cores,attributed to the 137Cs migration.Based on 210Pb constant rate of supply(CRS) model,the sedimentation accumulation rates range from 0.13 g/(cm2·yr) to 0.76 g/(cm2·yr) in the ZS core,and from 0.10 g/(cm2·yr) to 0.56 g/(cm2·yr) in the THS core.A remarkable increase in organic matter and nutrients has occurred in the two dated cores since the mid-1980s.The historical changes of organic matter and nutrients in the two cores are consisitent with the monitoring data for surface sediment after the 1960s.The TP accumulation rates after the early 1980s are 0.97 and 0.92 times higher than those from the 1950s to the 1980s in ZS and THS cores,respectively.Higher TP concentrations in the past two-decade deposits of Taihu Lake are due to both diagenetic factors and human activities.     

APPROACH TO THE REGIONALIZATION OF AGRICULTURAL—PASTURALIZATION AROUND CHANGSHAN ISLANDS IN NORTHERN YELLOW SEA

Based on the data of resources,environment and foundation of production,applying principal compo-nents-clustering quantitative analysis,this article divides the maritime space of Changshan Islands into three regions of agricultural-pasturalization,providing a scientific basis for the rational distribution of marine cultivation.The three re-gions are as follows:1)The region of an agricultural-pasturalization in the northern part of maritime space.It includes Da Wangjia and Shicheng islans.The main production is cultivation of prawn and mollusks in sea beach,float raft culture of mussel in shallow sea and scallop ,and breeding of sea cucumber in submarine.2)The region of agricultur-al-pasturalization in the middle western part of maritime space.It includes Da Changshan and Guanglu islands and west-ern part of Xiao Chengshan Island.The man production is folat raft culture of mussel and scallop in shallow sea,and breed-ing of sea cucumber in submarine.3)The region of agricultural-pasturlization of the southeastem part of maritime space.It includes the eastern part of Xiao Chan Island,Haiyang and Zhangzi islands.The main production is breeding of abalone,sea cucumber,algaes and fish.     

A 3600 years paleoclimatic change inferred from organic δ13C and TOC/TN of the Gucheng Lake sediments, southeast China

A 6.2 m thick core of Gucheng Lake sediment provided a 3600 years record of climate change. The contents of the TOC in the core changed from 2.63% to 8.48%, and the δ¹³C values of organic matter were from −21.54% to −27.3%. The TOC/TN ratios indicated that the organic materials in sediments were from lake plankton and land-derived plants. The 2.9–22 m core interval with high TOC/TN ratios, low δ¹³C values and low contents of TOC indicated a cold climate stage. The 6.2–5.5 m and 0.4–0.1 m intervals were characterized by low TOC/TN ratios, high δ¹³C values and high contents of TOC, and reflected temperate climate stages. Project 49372129 supported by NSFC.     

Reconstructing environmental changes of a coastal lagoon with coral reefs in southeastern Hainan Island

Coastal lagoons with small catchment basins are highly sensitive to natural processes and anthropogenic activities. To figure out the environmental changes of a coastal lagoon and its contribution to carbon burial, two sediment cores were collected in Xincun Lagoon, southeastern Hainan Island and (210) ~Pb activities, grain size parameters, total organic carbon(TOC), total nitrogen(TN), total inorganic carbon(TIC) and stable carbon isotopes(δ~(13)C) were measured. The results show that in 1770–1815, the decreasing water exchange capacity with outer open water, probably caused by the shifting and narrowing of the tidal inlet, not only diminished the currents and fined the sediments in the lagoon, but also reduced the organic matter of marine sources. From 1815 to 1950, the sedimentary environment of Xincun Lagoon was frequently influenced by storm events. These extreme events resulted in the high fluctuation of sediment grain size and sorting, as well as the great variation in contributions of terrestrial(higher plants, soils) and marine sources(phytoplankton, algae, seagrass). The extremely high content of TIC, compared to TOC before 1950 could be attributed to the large-scale coverage of coral reefs. However, with the boost of seawater aquaculture activities after 1970, the health growth of coral species was severely threatened, and corresponding production and inorganic carbon burial flux reduced. The apparent enhanced inorganic carbon burial rate after 1990 might result from the concomitant carbonate debris produced by seawater aquaculture. This result is important for local government long-term coastal management and environmental planning.     

Emissions of biogenic sulfur gases (H<Subscript>2</Subscript>S,COS) from <Emphasis Type="Italic">Phragmites australis</Emphasis> coastal marsh in the Yellow River estuary of China

Emissions of biogenic sulfur gases (hydrogen sulfide (H₂S) and carbonyl sulfide (COS)) from Phragmites australis coastal marsh in the Yellow River estuary of China were determined during April to December in 2014 using static chamber-gas chromatography technique with monthly sampling. The results showed that the fluxes of H₂S and COS both had distinct seasonal and diurnal variations. The H₂S fluxes ranged from 0.09 μg/(m²·h) to 7.65 μg/(m²·h), and the COS fluxes ranged from–1.10 μg/(m²·h) to 3.32 μg/(m²·h). The mean fluxes of H₂S and COS from the P. australis coastal marsh were 2.28 μg/(m²·h), and 1.05 μg/(m²·h), respectively. The P. australis coastal marsh was the emission source of both H₂S and COS over the whole year. Fluxes of H₂S and COS were both higher in plant growing season than in the non-growing season. Temperature had a dramatic effect on the H₂S emission flux, while the correlations between COS flux and the environmental factors were not found during sampling periods. More in-depth and comprehensive research on other related factors, such as vegetation, sediment substrates, and tidal action is needed to discover and further understand the key factors and the release mechanism of sulfur gases.     

Application of Wet Waste from Shrimp (Litopenaeus vannamei) with or Without Sea Mud to Feeding Sea Cucumber (Stichopus monotuberculatus)

In the present study, the applicability of the wet waste collected from shrimp(Litopenaeus vannamei) to the culture of sea cucumber(Stichopus monotuberculatus) was determined. The effects of dietary wet shrimp waste on the survival, specific growth rate(SGR), fecal production rate(FPR), ammonia- and nitrite-nitrogen productions of sea cucumber were studied. The total organic matter(TOM) level in the feces of sea cucumber was compared with that in corresponding feeds. Diet C(50% wet shrimp waste and 50% sea mud mash) made sea cucumber grow faster than other diets. Sea cucumber fed with either diet D(25% wet shrimp waste and 75% sea mud mash) or sole sea mud exhibited negative growth. The average lowest total FPR of sea cucumber occurred in diet A(wet shrimp waste), and there was no significant difference in total FPR between diet C and diet E(sea mud mash)(P > 0.05). The average ammonia-nitrogen production of sea cucumber in different diet treatments decreased gradually with the decrease of crude protein content in different diets. The average highest nitrite-nitrogen production occurred in diet E treatment, and there was no significant difference in nitrite-nitrogen production among diet A, diet B(75% wet shrimp waste and 25% sea mud mash) and diet C treatments(P > 0.05). In each diet treatment, the total organic matter(TOM) level in feces decreased to different extent compared with that in corresponding feeds.     

Bacterial diversity of gut content in sea cucumber (Apostichopus japonicus) and its habitat surface sediment

This study investigated the bacterial diversity of gut content of sea cucumber(Apostichopus japonicus) and its habitat surface sediment in a bottom enhancement area using PCR-based denaturing gradient gel electrophoresis(DGGE) technique. Bacterial diversity evaluation showed that the value of the Shannon-Wiener index of gut content in different intestinal segments of A. japonicus varied between 2.88 and 3.00, lower than that of the surrounding sediment(3.23). Phylogenetic analysis showed that bacterial phylotypes in gut content and the surrounding sediment of A. japonicus were closely related to Proteobacteria includingγ-, α-, δ-and ε-proteobacteria, Bacteroidetes, Firmicute, and Actinobacteria, of which γ-proteobacteria were predominant. These results suggested that the sea cucumber A. japonicus was capable of feeding selectively, and PCR-DGGE was applicable for characterizing the bacterial community composition in gut content and the surrounding sediment of sea cucumber. Further investigation targeting longer 16S rDNA gene fragments and/or functional genes was recommended for obtaining more information of the diversity and function of bacterial community in the gut content of sea cucumber.     

Induction and cultivation of cloned filaments of Polysiphonia urceolata (Rhodomelaceae, Rhodophyta)

A filamentous clone of Polysiphonia urceolata was regenerated from segments cut from the fronds of gametophytes. Unlike wild thalli with short virgate branchlets, the clone was filamentous with few branches. Many transparent trichoblasts arose from pericentral cells during the induction culture, but these were seldom observed during normal growth. The trichoblasts were uniseriate, often colorless, and formed lobed rhizoids rapidly when they came into contact with solid substrates. In addition to morphological characteristics, the photosynthetic properties and growth conditions of the clone differed from those of the mother plant. Cross-gradient light and temperature culture experiments revealed that the most favorable conditions for culture of the filamentous clone were 22°C and 95-120 μE/(m2-s) light intensity. The photosynthetic light saturation value for filaments was approx. 100 μE/(m2-s), which is far lower than that of wild thalli. These results could be used to develop techniques for mass cultures of P. urceolata in photobioreactors for production of seed stock or bioactive products.     

Tempo-spatial variations of sediment-associated nutrients and contaminants in the Ruxi tributary of the Three Gorges Reservoir,China

Ruxi River is a tributary of the Three Gorges Reservoir. This study examined the temporal and spatial dynamics in particle size characteristics and the associated nutrients and contaminants of the fluvial suspended and deposited sediments along the Ruxi River. Temporal variations in the particle size distribution of the suspended sediment are controlled mainly by differences in sediment source during different seasons. Total organic carbon(TOC), total nitrogen(TN) and total phosphorous(TP) in the 62μm fraction of the suspended sediment exhibit considerably higher concentrations in spring,indicating high probability of algal blooms in the backwater areas. Downstream trends in the nutrient contents of 62 μm deposited sediments imply the greatest potential for eutrophication in the backwater ends, where highest nutrient concentrations were detected. Assessment of metal contamination shows that the sediments deposited in the water-level fluctuation zone were moderately to strongly contaminated by Cadmium(Cd), with a considerably high potential ecological risk. The findings reported have emphasized the impacts of reservoir impoundment on aquatic and/or terrestrial environment in this region. More information on physical, chemical and biological processes of sediment and sediment-associated materials are needed for developing environmentally and ecologically sound policies of water and sediment management.     

Study on the Free Radical Scavenging Activity of Sea Cucumber （Paracaudina chinens vat.） Gelatin Hydrolysate

Gelatin from the sea cucumber （Paracaudina chinens var.） was hydrolyzed by bromelain and the hydrolysate was found to have a high free radical scavenging activity. The hydrolysate was fractionated through an ultrafiltration membrane with 5 kDa molecular weight cutoff （MWCO）. The portion （less than 5 kDa） was further separated by Sephadex G-25. The active peak was collected and assayed for free radical scavenging activity. The scavenging rates for superoxide anion radicals （O2·^-） and hydroxyl radicals （·OH） of the fraction with the highest activity were 29.02% and 75.41%, respectively. A rabbit liver mitochondrial free radical damage model was adopted to study the free radical scavenging activity of the fraction. The results showed that the sea cucumber gelatin hydrolysate can prevent the damage of rabbit liver and mitochondria.     

Combined influence of sedimentation and vegetation on the soil carbon stocks of a coastal wetland in the Changjiang estuary

Coastal wetlands play an important role in the global carbon cycle.Large quantities of sediment deposited in the Changjiang(Yangtze) estuary by the Changjiang River promote the propagation of coastal wetlands,the expansion of saltmarsh vegetation,and carbon sequestration.In this study,using the Chongming Dongtan Wetland in the Changjiang estuary as the study area,the spatial and temporal distribution of soil organic carbon(SOC) stocks and the influences of sedimentation and vegetation on the SOC stocks of the coastal wetland were examined in 2013.There was sediment accretion in the northern and middle areas of the wetland and in the Phragmites australis marsh in the southern area,and sediment erosion in the Scirpus mariqueter marsh and the bare mudflat in the southern area.More SOC accumulated in sediments of the vegetated marsh than in the bare mudflat.The total organic carbon(TOC) stocks increased in the above-ground biomass from spring to autumn and decreased in winter;in the below-ground biomass,they gradually increased from spring to winter.The TOC stocks were higher in the below-ground biomass than in the above-ground biomass in the P.australis and Spartina altemiflora marshes,but were lower in the below-ground biomass in S.mariqueter marsh.Stocks of SOC showed temporal variation and increased gradually in all transects from spring to winter.The SOC stocks tended to decrease from the high marsh down to the bare mudflat along the three transects in the order:P.australis marsh S.alterniflora marsh S.mariqueter marsh bare mudflat.The SOC stocks of the same vegetation type were higher in the northern and middle transects than in the southern transect.These results suggest that interactions between sedimentation and vegetation regulate the SOC stocks in the coastal wetland in the Changjiang estuary.     

Construction of cDNA library from intestine, mesentery and coelomocyte of Apostichopus japonicus Selenka infected with Vibrio sp. and a preliminary analysis of immunity-related genes

The aquaculture of sea cucumber Apostichopus japonicus (Echinodermata, Holothuroidea) has grown rapidly during recent years and has become an important sector of the marine industry in Northern China. However, with the rapid growth of the industry and the use of non-standard culture techniques, epidemic diseases of A. japonicus now pose increasing problems to the industry. To screen the genes with stress response to bacterial infection in sea cucumber at a genome wide level, we constructed a cDNA library from A. japonicus Selenka (Aspidochirotida: Stichopodidae) after infecting them with Vibrio sp. for 48 h. Total RNA was extracted from the intestine, mesentery and coelomocyte of infected sea cucumber using Trizol and mRNA was isolated by Oligotex mRNA Kits. The ligated cDNAs were transformed into DH5α, and a library of 3.24×105 clones (3.24×105 cfu mL-1) was obtained with the sizes of inserted fragments ranging from 0.8 to 2.5 kb. Sequencing the cDNA clones resulted in a total of 1106 ESTs that passed the quality control. BlastX and BlastN searches have identified 168 (31.5%) ESTs sharing significant homology with known sequences in NCBI protein or nucleotide databases. Among a panel of 25 putative immunity-related genes, serum lectin isoform, complement component 3, complement component 3-like genes were further studied by real-time PCR and they all increased more than 5 fold in response to Vibrio sp. challenge. Our library provides a valuable molecular tool for future study of invertebrate immunity against bacterial infection and our gene expression data indicates the importance of the immune system in the evolution and development of sea cucumber.     

Nitrogen deposition and its spatial pattern in main forest ecosystems along north-south transect of eastern China

A continuous three-year observation(from May 2008 to April 2011)was conducted to characterize the spatial variation of dissolved inorganic nitrogen(DIN)deposition at eight main forest ecosystems along the north-south transect of eastern China(NSTEC).The results show that both throughfall DIN deposition and bulk DIN deposition increase from north to south along the NSTEC.Throughfall DIN deposition varies greatly from 2.7 kg N/(ha·yr)to 33.0 kg N/(ha·yr),with an average of 10.6 kg N/(ha·yr),and bulk DIN deposition ranges from 4.1 kg N/(ha·yr)to 25.4 kg N/(ha·yr),with an average of 9.8 kg N/(ha·yr).NH4+-N is the dominant form of DIN deposition at most sampling sites.Additionally,the spatial variation of DIN deposition is controlled mainly by precipitation.Moreover,in the northern part of the NSTEC,bulk DIN deposition is 17%higher than throughfall DIN deposition,whereas the trend is opposite in the southern part of the NSTEC.The results demonstrate that DIN deposition would likely threaten the forest ecosystems along the NSTEC,compared with the critical loads(CL)of N deposition,and DIN deposition in this region is mostly controlled by agricultural activities rather than industrial activities or transportation.     

Effects of dietary β-glucan and glycyrrhizin on non-specific immunity and disease resistance of the sea cucumber (<Emphasis Type="Italic">Apostichopus japonicus</Emphasis> Selenka) challenged with <Emphasis Type="Italic">Vibrio splendidus</Emphasis>

Sea cucumbers, Apostichopus japonicus Selenka, were fed diets containing non-immunostimulant (basal diet), 0.2% β-glucan and 0.02% glycyrrhizin in a recirculatory water system for 45 days, and subsequently challenged with Vibrio splendidus by injection at 1.0×10⁸ cfu / sea cucumber for 15 days. Phagocytic capacity (PC), intracellular superoxide anion production (ISAP), lysozyme (LSZ) activity and superoxide dismutase (SOD) activity in the coelomic fluid were analyzed on the 0^th, 5^th, 10^th and 15^th days after injection. Results showed that after the 45-day feeding period, PC, ISAP, LSZ activity and SOD activity in sea cucumbers fed with dietary β-glucan or glycyrrhizin were significantly higher than in those fed with the basal diet. On the 5th day after infection, all the immune parameters examined in the sea cucumbers injected with V. splendidus decreased in value significantly. On the 15^th day, PC, ISAP and LSZ activity returned to levels similar to those on the 0^th day. For the sea cucumbers injected with saline, there were no significant differences in all the immune parameters examined and in the cumulative morbidity during the 15-day challenging trial. After injecting with V. splendidus, the cumulative morbidity of sea cucumbers fed with the basal diet was significantly higher than those fed with dietary β-glucan or glycyrrhizin when challenged with V. splendidus challenged sea cucumber fed with the basal diet was significantly higher than those fed with dietary β-glucan or glycyrrhizin. There was no significant difference in cumulative morbidity between the dietary β-glucan and glycyrrhizin treatments over time.     

Anthropogenic Effect on Deposition Dynamics of Lake Sediments Based on ~（137）Cs and ~（210）Pb_（ex） Techniques in Jiuzhaigou National Nature Reserve,China

Radionuclide dating techniques characterized by137Cs and210Pbex have recently been applied in the study of lake sediments around the world.In this study,a chronological series of sediment cores was established based on137Cs and210Pbex analyses along with the evaluation of sediment properties,such as particle size distribution,total organic carbon(TOC),carbonate content,and acid-insoluble residue,to study sediment accumulation rates,sediment sources,and responses to human activities in the Jiuzhaigou National Nature Reserve in southwestern China.In terms of the particle size distribution of sediments,silt content was the highest,and clay and sand contents were relatively low.The sediments displayed high TOC contents because of the significant amounts of vegetation grown in the lakes.The carbonate content was also high due to the overall geological background of carbonates in Jiuzhaigou.Carbonate content tended to decline from top to bottom in the sediment cores,whereas the acid-insoluble residue tended to increase.These results suggested that the depth variation of the environmental parameters of the sediments in two lakes in Jiuzhaigou would correspond to each other.The results indicated that the sediment rate of Jiuzhaigou was generally high with strong siltation,indicating that serious soil loss was induced by intensive human activities in the basin over the past decades.The increases in the mass accumulation rate,contents of acid-insoluble residue,and mean particle size during the periods of 1840–1900s,late 1930s–early 1950s,1966–1978,and2003–2006 revealed the occurrence of severe soil and water loss as a result of extensive agricultural expansion,large-scale deforestation,and road construction in Jiuzhaigou.The deposition rate and the properties of lacustrine sediments could reflect the significant impact of human activities on lake sedimentation during Jiuzhaigou′s history.