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1.
We made comparative studies of three tropical ox-bow lakes in India with different trophic states. The species number of zooplanktons was negatively correlated with the degree of water eutrophication, and lakes of similar trophic status had higher similarity of species. The most significant differences of species composition were observed with rotifers and zoobenthos. The density and biomass of phytoplankton, rotifers, oligochaetes and chironomids tended to increase with increasing nutrients. We observed a significant difference of dominant species in different waters, especially the eutrophic lake, which was dominated by a few species of oligochaetes. The abundance of Tanypus bilobatus showed a highly significant correlation with the degree of eutrophication. Rotifers and zoobenthos showed considerably lower biodiversity in the eutrophic lake.  相似文献   

2.
Often facilitated by human-mediated pathways, aquatic invasive species are a threat to the health and biodiversity of global ecosystems. We present a novel approach incorporating survey data of watercraft movement in a social network analysis to reconstruct potential pathways of aquatic invasive species spread between lakes. As an example, we use the green alga Nitellopsis obtusa, also known as starry stonewort, an aquatic invasive species affecting the Great Lakes region in the United States and Canada. The movement of algal fragments via human-mediated pathways(i.e., watercraft) has been hypothesized as the primary driver of starry stonewort invasion. We used survey data collected at boat ramps during the 2013 and 2014 openwater seasons to describe the flow of watercraft from Lake Koronis, where N. obtusa was first detected in Minnesota, to other lakes in the state. Our results suggest that the risk of N. obtusa expansion is not highly constrained by geographic proximity and management efforts should consider highly connected lakes.Estimating human movement via network analysis may help to explain past and future routes of aquatic invasive species infestation between lakes and can improve evidence-based prevention and control efforts.  相似文献   

3.
Freshwater mussels are a major component of the zoobenthos and they therefore play an important role in freshwater ecosystems. The community composition and the standing crop of freshwater mussels in Poyang Lake, the largest freshwater lake in China and one of two lakes connected to the Changjiang (Yangtze) River, were investigated from February 2008 to May 2009. Mussels were sampled in hydrologically and geographically distinct sampling areas. A total of 42 species and 13 genera were identified, of which 32 species were endemic to China. Two species, Unio douglasiae and Lamprotula caveata, dominated all sampling areas. The number of genera and species, and the number of species within each genus, differed significantly among sampling areas. Freshwater mussels were very abundant, with an overall density of 0.28 ± 0.22 ind./m2 and biomass of 4.08 ± 3.96 g/m2. Significant variation observed among sampling areas and among genera was probably due to the variety of habitats among the areas sampled and to the adaptability of different freshwater mussels to environments. This study suggests that Poyang Lake and other freshwater lakes in the region are important sites of freshwater mussel biodiversity and conservation.  相似文献   

4.
Harmful algal blooms in eutrophic waters pose a serious threat to freshwater ecosystems and human health. In-situ light availability control is one of the most commonly used technologies to suppress algae in lakes and reservoirs. To develop a better understanding of the effects of light on algal growth, specific density, colony size and sinking loss, Anabaena flos-aquae(cyanobacteria) and Scenedesmus obliquus(green algae) were evaluated in varying light scenarios. The results showed that the specific density and colony size of these two species varied during growth, and there were obvious differences among the light scenarios. At the end of exponential phase, S. obliquus incubated under light-limited condition maintained a higher specific density and formed larger aggregates, whereas A. flos-aquae formed a longer filament length. Both species exhibited higher sinking loss rates with lower light availability. These results implied that the sinking loss rate was not always constant but should be considered as a variable response to the change of light availability, and in-situ light availability control might result in a significant increase of the sinking loss of algae due to the change of size and specific density, thereby further affecting the algal biomass in the water column.  相似文献   

5.
The status of fishery stocks in the coastal waters of China is far from ideal, mainly due to climate change and the impacts of human activities (e.g., pollution and overfishing). Thus, the restoration and protection of fishery resources have become critical and complex. The stability and balanced structure of the fish community is a basic foundation for the protection of fishery resources. Based on data collected from bottom trawls by the R/V Beidou in continental shelf of the East China Sea in November 2006 and February 2007, changes in the composition and diversity of fish species and functional groups were analyzed. The research area was divided into offshore waters and inshore waters by the two-way indicator species analysis (TWIA). The results showed that the dominant species were different between offshore waters and inshore waters and also varied with the survey time. The most abundant family was Sciaenidae and Teraponidae in November 2006, Sciaenidae, Engraulidae and Triglidae were most abundant in February 2007. The species belonged mainly to mobile piscivores (G6), benthivores/piscivores (G4), benthivores (G3) and planktivores (G1), and the dominant species in November 2006 were commercial species (e.g. Larimichthys polyactis and Trichiurus japonicus), but small-sized species were dominant in February 2007 (e.g., Harpadon nehereus, Benthosema pterotum, Champsodon capensis, and Acropoma japonicum). The species diversity showed a similar trend as the functional group diversity. Stations with higher diversity were mainly distributed in inshore waters in February 2007, whereas higher diversity was found in offshore waters in November 2006. The highest biomass and species number were found in G6 group, followed by the G4, G5 and G1 groups. The distribution of the number of individuals of each functional group showed the opposite trend as that of the biomass distribution. In addition, the size spectra were mainly concentrated around 3–29 cm, and the individual number of fish species gradually decreased with the increase in body size, but the relative biomass showed a moderate fluctuation in each size class. These changes showed that species with faster growth rate and earlier maturity age became dominant in continental shelf of the East China Sea. So the variations in biological characteristics of fish should be fully considered in maintaining sustainable utilization of fishery resource.  相似文献   

6.
From 1997 to 2000, four field surveys were conducted in the East China Sea (ECS) (23°30′–33°00′N, 118°30′–128°00′E). A field data yield density model was used to determine the optimal salinities for 19 dominant copepod species to establish the relationship between surface salinities and abundance of those species. In addition, ecological groups of the copepods were classified based on optimal salinity and geographical distribution. The results indicate that the yield density model is suitable for determining the relationship between salinity and abundance. Cosmocalanus darwini, Euchaeta rimana, Pleuromamma gracilis, Rhincalanus cornutus, Scolecithrix danae and Pareucalanus attenuatus were determined as oceanic species, with optimal salinities of >34.0. They were stenohaline and mainly distributed in waters influenced by the Kuroshio or Taiwan warm current. Temora discaudata, T. stylifera and Canthocalanus pauper were nearshore species with optimal salinities of <33.0 and most abundant in coastal waters. The remaining 10 species, including Undinula vulgaris and Subeucalanus subcrassus, were offshore species, with optimal salinity ranging from 33.0–34.0. They were widely distributed in nearshore, offshore and oceanic waters but mainly in the mixed water of the ECS.  相似文献   

7.
The present study preliminarily examined the differences in maximum handling size, prey size and species selectivity of growth hormone transgenic and non-transgenic common carp Cyprinus carpio when foraging on four gastropods species( Bellamya aeruginosa, Radix auricularia, Parafossarulus sinensis and Alocinma longicornis) under laboratory conditions. In the maximum handling size trial, five fish from each age group(1-year-old and 2-year-old) and each genotype(transgenic and non-transgenic) of common carp were individually allowed to feed on B. aeruginosa with wide shell height range. The results showed that maximum handling size increased linearly with fish length, and there was no significant difference in maximum handling size between the two genotypes. In the size selection trial, three pairs of 2-year-old transgenic and non-transgenic carp were individually allowed to feed on three size groups of B. aeruginosa. The results show that the two genotypes of C. carpio favored the small-sized group over the large-sized group. In the species selection trial, three pairs of 2-year-old transgenic and non-transgenic carp were individually allowed to feed on thin-shelled B. aeruginosa and thick-shelled R. auricularia, and five pairs of 2-year-old transgenic and non-transgenic carp were individually allowed to feed on two gastropods species( P. sinensis and A. longicornis) with similar size and shell strength. The results showed that both genotypes preferred thin-shelled Radix auricularia rather than thick-shelled B. aeruginosa, but there were no significant difference in selectivity between the two genotypes when fed on P. sinensis and A. longicornis. The present study indicates that transgenic and non-transgenic C. carpio show similar selectivity of predation on the size-and species-limited gastropods. While this information may be useful for assessing the environmental risk of transgenic carp, it does not necessarily demonstrate that transgenic common carp might have lesser environmental impacts than non-transgenic carp.  相似文献   

8.
Water quality, size, connectivity and other physical properties of hydrological systems might have different functions in the formation and maintenance of biodiversity, but this remains mostly unclear due to the lack of undisturbed sites for experimental modelling. Alpine freshwater habitats such as micro-waterbodies(MWB) represent a kind of natural system suitable for biodiversity research. In order to assess potential linkages between environmental factors, connectivity of MWBs and aquatic species richness, we conducted a pilot study in two separated MWB systems located in Gaoligong Mountain, northwest Yunnan province, China. A total of 27 MWBs have been analyzed, including 22 connected and 5 isolated bodies. 13 conventional environmental factors were tested while all kinds of aquatic macro-organisms were collected and classified. Results showed a high environmental heterogeneity among MWBs and significant differences between the two systems but only a few environmental variables such as the depth of soil bottom, total Nitrogen and altitude were related to species richness and the formation of the community structure. As a benefit from the high environmental heterogeneity, the cascaded MWB systems provided divergent habitats able to support species richness at a higher level than the same number of randomly selected MWBs. This finding supports the idea that habitat connectivity matters also in extremely small aquatic ecosystems. Moreover, although still a preliminary result, a polarization effect within connected chains where edge MWBs host higher taxa and endemic taxa richness as well as larger populations, was detectable. This study gives interesting insights on the spatial processes driving community structure and a new prospective for biodiversity conservation. Since alpine MWBs have significant effects on the maintenance of watershed biodiversity, further research on such small and crucial ecosystems is encouraged.  相似文献   

9.
In this study, a coniferous tree species (Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains (QLM) to detect the trends in carbon isotope ratio (δ13C), leaf nitrogen content (LNC) and stomatal density (SD) with altitude variation in north-subtropical humid mountain climate zone of China. The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m, whereas leaf δ13C exhibited a significantly negative correlation with the altitude. Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment, suggesting that the pattern of increasing δ13C with the altitude cannot be generalized. The negative correlation between δ13C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude. Furthermore, there was a remarkable negative correlation between leaf δ13C and LNC. One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ13C. The significant negative correlation between leaf δ13C and SD over altitudes was also found in the present study, indicating that increases in SD with altitude would reduce, rather than enhance plant δ13C values.  相似文献   

10.
This study provides a checklist of species distributed at the altitude gradient of Moghan-Sabalan rangelands in Ardabili province, Northwest Iran. We evaluated the changes in species composition, growth types of species, Raunkiaer’s life forms, geographical distribution, threat and endemicity status, and palatability of species along two altitudinal gradients in the sampling plots, which were conducted in eleven sites/habitats with 300 meters above sea level (masl) altitude intervals (from 100 to 3300 masl). We assessed the plant species composition with special reference to the gradient analysis, and identified overall 396 species, which was comprising 44 families and 194 genera. Results showed that Asteraceae family is by far the most species-rich family, followed by Poaceae, Fabaceae, Caryophyllaceae and Brassicaceae. Among the genera, Astragalus is the most diverse genus, followed by Allium, Veronica and Bromus, Galium, Silene and Ranunculus. Results indicated that the number of species increased as the altitude increased to 1200–1500 masl, but then starts to decline to 3300 masl. Family-to-genera ratio was 1:4.4, the family-tospecies ratio was 1:9, and the genera-to-species ratio was 1:2.04. Growth type of species analysis shows that the frequency of perennial plants was higher in the study area followed by annual species while the lower group was biennial species. The number of annuals showed a decreasing trend towards higher altitude. Hemicryptophytes and therophytes were the most frequent life forms constituted each with (41.9%). Hemicryptophytes showed an increasing trend with altitude, while therophytes showed a decreasing trend with altitude increase, followed by geophytes, chamaephytes, and phanerophytes. Results showed more than half of the species of the study area belonged to Iran-Turanian region and these species showed an increasing trend with altitude. In contrast, Sahara-Sindian species comprise a minor component of the spectrum, with decreasing trend with altitude. The rare and endangered species out of the surveyed taxonomic groups comprised 53 species in total which 29 of them are considered lower risk (LR), 13 data deficient (DD), 5 vulnerable (Vu) and with 3 rare (R) and identified endemic plants comprised 24 species. Some 56.6% species were identified as class III, 22.6% were class I and 20.8% were class II as the palatability variation. Moghan-Sabalan rangelands require strong conservation management policies in case of species loss and changing natural communities due to the occurrence of conversion into cropland, over-grazing and other anthropogenic effects.  相似文献   

11.
A considerable part of the world's population is currently experiencing a severe scarcity of freshwater and nutrition. Inland aquaculture has the fastest growth in fresh waters, and this contributes to the eutrophication of freshwater bodies. The increase in freshwater aquaculture impacts on the increasing demand for fresh water. A way to overcome this is to develop aquaculture in saline lakes. This article discusses how saline and hypersaline lakes may contribute to overcome this problem and gives a list of fish and shrimp species that can be cultivated in saline lakes. Successful development of aquaculture depends on a healthy cultured stock of commercial fish and shrimps. A sustainable healthy stock of fish and shrimps can be only maintained using live food for the cultured fish larvae, fry and fingerlings. As well as Artemia spp. there are many other crustacean species with the potential for growing in hypersaline waters. At least 26 copepod species around the world can live at a salinity above 100 g/L with 12 species at a salinity higher than 200 g/L, and these all have excellent nutritional value. There is a high potential to use eukaryotic organisms of diff erent taxa in saline/hypersaline aquaculture for food, agri-aquaculture, diff erent industries and as food supplements.  相似文献   

12.
The total benthic macrofauna consisting of 62 species in 5 groups, viz. crustaceans （18）, gastropods （17）, bivalves （16）, polychaetes （9） and fishes （2）, was recorded in western Kachchh mangroves near Gujarat. The population densities of benthic macrofauna ranged from 424 to 2393 ind.m^-2, the diversity ranged from 1.84 to 2.45 bits ind.^-1, the richness varied between 0.82 and 0.98, and the evenness varied between 0.64 and 0.81. Two maximum diversity values were recorded during winter and summer. The salinity ranged from 34 to 44, temperature varied between 17 and 37 ℃, and the acidity ranged from 7 to 8.9.  相似文献   

13.
We evaluated the response of a rotifer community to environmental changes in five shallow lakes in the middle reach of the Changjiang （Yangtze） River in summer and autumn 2010. These five lakes differed in trophic status and rotifer community structure. Twenty-nine rotifer species were collected, of which Keratella cochlearis, Polyarthra dolichoptera, and Trichocerca elongate were dominant. The mean density, Shannon-Wiener diversity, and equitability among the five lakes differed significantly （P〈0.05）. The mean rotifer density was positively correlated with trophic state. The diversity was higher in lakes with high macrophyte coverage. The composition of rotifer species was closely associated with the trophic gradient. Five environmental variables, Secchi depth, conductivity, TN, NHa-N, and TP, significantly affected the composition of rotifer species. Keratella quadrata, Brachionus calyciflorus, and B. forficula were more common in eutrophic conditions. Our results suggest that eutrophication has a significant influence on the rotifer community structure and highlight the potential for using rotifer community structure as an indicator of trophic status in subtropical lakes.  相似文献   

14.
Geng  Huixia  Sun  Hongxiao  Liu  Chao  Kong  Fanzhou  Zhang  Qingchun  Yan  Tian  Yu  Rencheng 《中国海洋湖沼学报》2022,40(6):2218-2230

Lipophilic marine toxins (LMTs) produced by some microalgae in the sea could accumulate in shellfish and pose potential threats to the health of seafood consumers. Phytoplankton and shellfish samples were collected from coastal waters of Weihai in Shandong Peninsula, China in autumn, 2020, and screened for lipophilic marine toxins and their potential producers using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and high throughput sequencing of partial DNA (V4 region of the 18S rRNA gene) extracted from phytoplankton. Pectenotoxin-2 (PTX2), trace amounts of azaspiracid (AZA1 or AZA40), and 13-desmethyl spirolide C (13-DesMe-C) were detected in phytoplankton samples, while PTX2 and gymnodimine (GYM) were detected in shellfish samples. The toxin content in shellfish samples was much lower than the regulatory limit or values reported previously. Results suggest that lipophilic marine toxins should have low risk in coastal waters of Weihai in autumn. Based on the data of high throughput sequencing, the OTUs were assigned to 5 identified species of Alexandrium, including A. ostenfeldii capable of producing 13-DesMe-C and GYM. Two OTUs were found closely related to the toxic species in genus Dinophysis, but it is impossible to assign them to any identified species due to the low resolving power of the V4 region for Dinophysis. The OTUs could not be assigned to any identified species in the genus Azadinium, suggesting the existence of unidentified species in this region.

  相似文献   

15.
This paper reports the first photosynthetic study of marestail in Jiuzhaigou. In this work, we used PAM fluorometry to examine photosynthetic rates of submerged and emerged marestail in three lakes. Three lakes were studied across a gradient of water temperature, with low water temperature conditions in Grass Lake and Arrow Bamboo Lake, and higher water temperature in Five Colored Lake. In the field, electron transport rates (ETRmax) were measured as rapid light curves (RLCs) by in situ yield measurements. Submerged and emerged marestail showed higher photosynthetic activity in Five Colored Lake compared to the other lakes, a response consistent with the adaptation of marestail in Five Colored Lake to high water temperature. The optimal temperature for photosynthesis of submerged marestail in Jiuzhaigou was about 12 °C. Nonphotochemical quenching (NPQ) of submerged and emerged marestail increased with increasing water temperature. Maximum quantum yield (F v/F m) of submerged marestail in Five Colored Lake showed full recovery at 1700 h due to higher NPQ. Further, the chlorophyll a for submerged marestail was the highest in Grass Lake and the lowest in Five Colored Lake. These results indicate that in different lakes the function of these aquatic plants is associated with a diversity of place-dependent environmental conditions, especially water temperature that leads to pronounced differences in the plant’s ecophysiological reactions.  相似文献   

16.
根据2010~2011年中街山列岛水域4个季节的渔业资源调查资料,分析了该水域虾类资源密度和群落多样性,并探讨了底层温度、底层盐度和水深对虾类数量分布和多样性的影响.结果表明:共有虾类20种,隶属于9科18属;广温广盐种无论在种类数还是尾数密度与生物量均占主导地位;虾类生物量和尾数密度在季节分布上,以冬季最高,冬季均与春、夏和秋三季呈显著差异(p值<0.05);平面分布上,生物量与密度指数总体上呈南北高、中间低,东部高西部低的特征;生物量与平均底温显著相关(P<0.05),与平均底盐和水深相关性较差(p值>0.05);葛氏长臂虾、细巧仿对虾、中国毛虾、日本鼓虾和中华管鞭虾为四季的优势种,且均属广温广盐种;虾类群落Margalef丰富度指数为0.61~1.09,Shannon-Wiener多样性指数为0.76~1.31,Pielou均匀度指数为0.50~0.70,其中丰富度指数和多样性指数春季与冬季均存在显著差异(P<0.05),均匀度指数秋季与冬季存在显著差异(p值<0.05).  相似文献   

17.
This article presents the results ofhydrochemical and hydrobiological studies of shallow saline lakes of the Borzya group （Zabaikalsky K_rai, Russia） at the initial filling phase. The lake-margin ecosystems of the studied lakes are characterized by varying degrees of salinity from polyhaline to brine water. Cyclical variations of meteorological conditions and high salinity determined that the compositions of the aquatic organisms are specific, mostly between stenohaline and euryhaline species, the quantities are low, and the community structures are simple.  相似文献   

18.
冰川变化监测对生态灾害预防、区域水资源调控、气候变化研究等意义重大。利用冰川在雷达干涉影像上表现出失相干这一特性,选用1998年ERS 1/2与2018年 Sentinel-1A重轨单视复数SAR数据,通过相干系数取阈值的方法获取东帕米尔高原两个时期的冰川边界,以Landsat TM/OLI影像和全球陆地冰川空间监测计划发布的数据验证本文冰川边界提取的精度,从而分析冰川变化。结果表明：① 拟合研究区相干系数图上相干系数γ与对应像元个数的曲线关系,冰川区像元个数会在低相干区域积累形成一个小的波峰。曲线一阶导数变缓的点（冰川区向非冰川区过渡的转折点）即为所选阈值点,利用SAR相干系数取阈值法提取的冰川边界与光学遥感影像结合RGI6.0数据提取的验证冰川边界具有较好的一致性,SAR干涉相干系数提取冰川边界的方法是可行而有效的,ERS 1/2与Sentinel-1A提取的冰川总面积精度均在90%以上,而且SAR数据能够有效提取光学遥感影像难以识别的冰川表碛覆盖;② 1998年和2018年东帕米尔高原冰川总面积减少了318.59 km2,年平均变化速率为-15.93 km2/a,冰川退缩面积占冰川总面积的23%;③ 对大、中型规模冰川来说,表碛覆盖型冰川退缩较其他冰川明显;从坡向上来看,20年各个坡向冰川均有所退缩,其中东南坡冰川退缩最多,西坡冰川退缩最少;从海拔上来看,1998年冰川集中分布在4519~5421 m海拔区间内,2018年集中分布在4682~5320 m海拔区间内;在3325~5710 m海拔区间内冰川退缩明显,4915 m海拔附近达到退缩极大值。  相似文献   

19.
Willow species(Salix fragilis L.and S.alba L.) are important elements of cold desert agroforestry systems in the Lahaul valley,northwestern Himalaya.Their ability to grow through shoot-cuttings plantations under extreme and xeric climatic conditions of cold deserts,makes them ecologically suited and socially accepted for forestry programmes.Willow species in cold deserts may combat desertification and can thrive well in these areas as compared to any other species.Salix fragilis L.and S.alba L.are under cultivation in the Lahaul valley.However,S.fragilis is widely cultivated under the agroforestry and plantation forestry systems.In the Lahaul valley,willow species are used as subsistence resources and for socio-religious purposes.The present study was carried out to examine the vegetation analysis,density,diversity and distribution of willow species,present status and potential willow plantation sites and uses.The results of present study revealed that a higher species density was recorded at middle altitude villages(Jahlma-3,000 m asl and Hinsa-2,700 m asl),except,a higher density of S.fragilis was at Khoksar(3,200 m asl) in plantation forestry on south-facing slopes.In forests,S.fragilis was planted mainly along the water channels,resulted a low density.The shrubby willow species occurred naturally in the entire Lahaul valley up to an altitude of 3,850 m asl.81% of households felt the scarcity of willow trees,whereas,19% of households were satisfied with the willow trees they owned.The majority of willow species were planted in middle altitudes on privately owned irrigated lands.It was rated most potential prospective willow planting site by the farmers.Small size of land-holdings was one of the main constraints for establishing a large number of willow plantations.Commercial aspects of willow species need to be investigated to encourage the farmers to plant more willows further.  相似文献   

20.
Silicon is a necessary nutrient for diatoms, silicon uptake in diatom reproduction decreased seawater silicon content. This paper clarified the characteristics of silicon transferring in the sea, which plays an important role in phytoplankton growth, zooplankton graze and marine ecosystem. Analysis revealed that silicate is supplied by terrestrial sources, through plankton uptake, death, and eventually deposits to the sea bottom, and cannot diffuse upward. This is a general silicon deficit process. Many global marine waters showed the same silicon transfer route: land→silicon biogeochemical process→sea bottom. River flow brings abundant silicate into marine waters, silicate concentration in the waters decreased in the distance away from the river estuaries. In discussion of silicon characteristics and its transfer route, it was considered that the main factor controlling the mechanism of diatom and non-diatom red tides occurrence is silicon, and the changes in silicon source. Human activities, such as sea-route cutting by building embankment and dam, and silicon supplement by the sea, such as sandstorm, rainstorm and storm tide, have largely impaired the earth ecosystem and hugely threatened the human existence. It is suggested in this paper that man should resume the original face of the Si input into the sea to keep natural ecosystem in sustainable pattern.  相似文献   

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