Why do offshore breakwaters trap low levels of fine-grained sediments? Insights from Vietnam

Coastal erosion trend analysis using a combination of remote sensing and hydrodynamic models: Case study of Ca Mau Cape, Mekong Delta

Biotic and abiotic properties most closely associated with subtropical forest soil respiration differ in wet and dry seasons: A 10-year in situ study

The southwestern mountains of Hainan Island are the southernmost region with tropical karst landform in China. The frequent alternation of dry and wet seasons leads to the loss of the mineral nutrients of limestone, creating karst fissure habitats. Plants living in karst fissure habitats for long periods of time have developed local adaptation mechanisms correspondingly. In the paper, hydrogen–oxygen stable isotope technology was applied to determine the water-use sources of Impatiens hainanensis in the dry and wet seasons, hoping to expound the adaptation mechanism of I. hainanensis in karst fissure habitats to the moisture dynamics in the wet and dry seasons. In the wet season (May to October, 2018), the air humidity is relatively high in the I. hainanensis habitat; in the dry season (November 2018 to April 2019), there is a degree of evaporation. In the wet season, fine-root biomass increases with soil depths, while coarse-root biomass decreases with soil depths; in the dry season, fine-root biomass is lower and coarse-root biomass is higher compared with the wet season. It was found that the average rainfall reached 1523 mm and the main water-use sources were shallow (0–5 cm) and middle (5–10 cm) soil water, epikarst water, and shallow karst fissure water during the wet season; the average rainfall reached 528 mm, and the deep (10–15 cm) soil water and shallow karst fissure water were the main water-use sources during the dry season. Fog water has a partial complementary effect in the dry season. The differences in the distribution of root biomass and each source of water in the wet and dry seasons of I. hainanensis also reflect the different water-use strategies of I. hainanensis in the wet and dry seasons. In both dry and wet seasons, I. hainanensis formed a water-use pattern dominated by soil water and shallow fissure water (0–15 cm) under the influence of the “fissure-soil-plant” system in the karst region.

Decline in suspended sediment concentration delivered by the Changjiang (Yangtze) River into the East China Sea between 1956 and 2013

水位的洪枯变化通过江湖连通影响泛滥平原湖泊鱼类的组成和分布，因而江湖过渡带是反映泛滥平原生态系统鱼类交流和多样性变动的关键区域.尽管如此，针对江湖过渡带鱼类群落随水位洪枯变化的研究十分匮乏.本研究以菜子湖江湖过渡带为例，分别在洪水和枯水期选取包括静水和流水生境的样点对鱼类群落进行系统的调查采样，探讨水位洪枯变化对菜子湖江湖过渡带鱼类物种和功能多样性的影响.共采集到鱼类6目12科37属52种，其中，洪水期和枯水期物种数差异显著，分别采集到鱼类50和42种，而静水生境和流水生境物种数差异不明显，分别采集到鱼类47和48种.与洪水期相比，枯水期山溪河流性鱼类的物种数、重量、尾数和优势度百分比分别减少了7.3%、6.3%、14.4%和12.0%；与静水生境相比，流水生境山溪河流性鱼类的物种数、重量、尾数和优势度百分比分别增加了5.3%、14.6%、18.0%和22.3%.SIMPER分析结果显示，麦穗鱼（Pseudorasbora parva）、蛇鮈（Saurogobio dabryi）、（Hemiculter leucisculus）、鲤（Cyprinus carpio）、鲫（Carassius auratus）、短颌鲚（Coilia brachygnathus）、似鳊（Pseudobrama simoni）、翘嘴鲌（Culter ilishaeformis）、达氏鲌（Culter dabryi）、光唇蛇鮈（Saurogobio gymnocheilus）和无须鱊（Acheilognathus gracilis）是引起水位洪枯变化以及不同生境类型鱼类群落结构差异的主要物种.优势度分析结果表明枯水期和静水生境的优势种鱼类相似，重要值较高的优势种鱼类为鲤、鲫、和似鳊；而洪水期和流水生境的优势种鱼类同样相似，重要值较高的优势种鱼类为麦穗鱼、蛇鮈、光唇蛇鮈和短颌鲚.通过双因素方差分析解析了水位洪枯变化和不同生境类型对鱼类物种和功能多样性的影响.发现洪枯水位变化仅对物种多样性指数中的物种数（Richness）产生显著差异，而对功能多样性的3个指数（功能丰富度指数（FRic）、功能离散指数（FDiv）和功能分散指数（FDis））均有显著影响.洪水期鱼类的Richness、FRic、FDiv和FDis指数均显著高于枯水期.同时，静水生境条件下的FRic指数要显著高于流水生境.本研究发现，与传统的物种多样性相比，基于功能性状的功能多样性对水位的洪枯变动更为敏感，河流周期性洪泛是泛滥平原生态系统中鱼类功能补充的重要方式.;Water level fluctuations between wet and dry seasons, assisting by lateral connectivity, play a fundamental role in underpinning the composition and distribution of fish fauna in floodplain lakes. The ecotone floodplains between the floodplain rivers and lakes are generally considered as the key areas where witness the exchange of fish species and the variations of biodiversity. However, the study of changes in taxonomic and functional diversity of fish communities in the ecotone floodplain in response to water level fluctuations is limited. Here we address this issue by measuring temporal (dry and wet seasons) and spatial (lotic and lentic habitat patches) changes in taxonomic and functional diversity of fish communities in the ecotone floodplain between the Yangtze River and Lake Caizi. A total of 52 species belonging to 37 genera, 12 families and 6 orders were collected in our study. Among them, there were significant differences in species number between wet and dry seasons, with 50 species and 42 species collected respectively. On the other hand, there was no significant difference in the number of species between lentic and lotic habitat patches, with 47 species and 48 species collected respectively. In comparison with wet season, the species richness, weight, abundance and importance value percentage of riverine species decreased by 7.3%, 6.3%, 14.4% and 12.0% in dry season. In comparison with lentic habitat patches, the species richness, weight, abundance and importance value percentage of riverine species increased by 5.3%, 14.6%, 18.0% and 22.3%. The fish fauna differences between seasons (dry and wet) and habitat patches (lentic and lotic) were determined by the abundance of Pseudorasbora parva, Saurogobio dabryi, Hemiculter leucisculus, Cyprinus carpio, Carassius auratus, Coilia brachygnathus, Pseudobrama simony, Culter ilishaeformis, Culter dabryi, Saurogobio gymnocheilus and Acheilognathus gracilis. Important value analysis showed that the dominant species of fish in lentic habitat patches and dry season were similar, and the dominant species of fish in lotic habitat patches and wet season were similar as well. The dominant species in wet season and lotic habitat patches were P. parva, S. dabryi, S. gymnocheilus and C. brachygnathus, while the dominant species in dry season and lentic habitat patches were C. carpio, C. auratus, H. leucisculus and P. simoni. Two-way ANOVA analysis indicated that one taxonomic diversity indices (Richness) and three functional diversity indices (FRic, FDiv and FDis) significantly differed between wet and dry seasons. Taxonomic richness, functional richness, functional divergence and functional dispersion were significantly higher in wet season than in dry season. Meanwhile, the functional richness was significantly higher in lentic than in lotic habitat patches. Functional diversity exhibited higher sensitivity than the traditional taxonomic diversity, since three functional diversity indices showed significant variations between wet and dry seasons. Meanwhile, our study highlight important functional recruitments of fish assemblages triggered by seasonal flood pulses.

以艾比湖流域主要入湖河流为研究对象，在5月（丰水期）和8月（枯水期）分别沿博尔塔拉河（博河）和精河进行采样，采用平行因子模型（PARAFAC）和三维荧光区域积分法对水体三维荧光特性进行研究并对其与水质的关系在枯、丰水期下的变化进行探讨.结果表明①河流DOM在枯水期与丰水期都含有C1（240、425 nm） UVC类腐殖质，C2（225、290 nm）紫外区内络氨酸类有机物，C3（230/280、330 nm）蛋白类有机物，C4（265、260 nm）腐殖质类共4种组分.通过对水体三维荧光进行区域积分可以看出DOM荧光成分的占比在不同时期的变化.博河在枯水期时EEM光谱中的区域Ⅲ富里酸含量低于丰水期，枯水期时区域Ⅱ芳香类蛋白质、区域Ⅳ可溶性微生物代谢物以及区域Ⅴ类腐殖质酸高于丰水期；对于精河来说，区域Ⅱ芳香类蛋白质和区域Ⅳ可溶性微生物代谢物在枯水期的含量高于丰水期，区域Ⅲ富里酸和区域Ⅴ类腐殖质酸的含量枯水期低于丰水期，这表明水体腐质化程度较高.②本研究选取了一些常规的荧光指数来描述枯、丰水期水体的荧光指数特性.经研究发现，精河的荧光指数、自生源指数和腐殖化指数在不同时期的变化幅度较小，而博河的变化幅度较大.③将荧光指数与水质参数进行相关性分析并建模，结果表明枯水期自生源指数（BIX）与化学需氧量呈显著正相关，相关系数R=0.688；丰水期时BIX与铵态氮浓度呈显著负相关，相关系数R=-0.493.通过对比分析艾比湖主要入湖河流的三维荧光光谱特性与水质在枯、丰水期时的关系进一步表明水体中DOM的特性以及在枯、丰水期下的差异，为艾比湖流域的治理改善提供一定的理论支持和参考依据.;This study takes the main lakes in Lake Ebinur Watershed as the research object, and samples along the Bortala River and Jing River in May (wet season) and August (dry season). The PARAFAC analysis method and the three-dimensional fluorescence region integration method is used to study the three-dimensional fluorescence characteristics of water and its seasonal variation with water quality. The results show that:1)In both dry and wet seasons, river DOM contains C1 (240, 425 nm) and C4 (265, 260 nm) kind of humus, C2 (225, 290 nm) uranium-like organic matter compounds. It found that fulvic acid is lower, while the aromatic protein, soluble microbial and humic acid were highest in dry season than wet season in Bortala River. The concentration of the aromatic protein and soluble microbial in dry season was higher than in wet season, and the fulvic acid and humic acid in dry season was lower than in the wet season in Jing River, based on fluorescence regional integral (FRI) analysis and the regional standards related to water quality and fluorescence. This indicates that the degree of decomposition in water is relatively high; 2)In this study, some conventional fluorescence indexes were selected to describe the fluorescence index characteristics of water in wet and dry season. It found that the three indexes (FI, BIX, HIX) of the water quality of Jing River and Bortala River in dry and wet seasons showed slight changes, comparing to larger changes in the Bortala River. In general, the change of water quality of Jing River and Bortala River in dry and wet seasons is mainly influenced by microbial activities and human activities; 3) In terms of the correlation coefficients of water quality parameters and fluorescence indexes in different seasons, the results showed that the relationship between BIX and COD concentration was best and a significant positive correlation in dry season(R=0.688, P<0.01). Secondly, there is a significant negative correlation between BIX and ammonium nitrogen concentration in wet season (R=-0.493, P<0.05). The study provides theoretical support and reference basis for the improvement of the governance of Lake Ebinur Watershed, which further proved that exogenous characteristics and the differences in different periods of DOM sources in the water.

The study analysed the spatial and temporal contamination levels of fresh water resources by saline intrusion in the Douala coastal area. Water samples were collected from 19 stations. 3 stations were selected from the mangrove area and 16 stations were selected from the rest of the area partitioned into four transects (coastal transect, inner transect 1, inner transect 2 and inner transect 3). Sampling was done repeatedly during the wet and dry seasons. They were analyzed for physico-chemical parameters according to the American Public Health Association methods. Geostatistical analysis was used in mapping the water properties. Considerable levels of actual electrical conductivity values (208.91 to 660.63 and 45 to 7540 μS/cm for the wet and dry seasons, respectively); calcium (0.06 to 85 and 4 to 256 mg/L for the wet and dry seasons, respectively); sulphate (0 to 103 and 0 to 99 mg/L for the wet and dry seasons) and total dissolved solids (15.79 to 1467 and 20 to 3750 mg/L for the wet and dry seasons, respectively) were observed for ground water in the study area based on spatio-temporal assessment. From the output grid, it could be deduced that the south eastern region had a hint of salt water intrusion (SWI) contamination of fresh water resources with actual value highs of electrical conductivity (1790 and 820 μS/cm) for the dry and wet seasons, respectively. Calcium highs (140 and 16 mg/L) for the dry and wet seasons were obtained at the central part of the study area. The spatial distribution of calcium highs extends from the central zone of the study area in the dry season and the south eastern zone in the wet season. The southern region is more vulnerable to contamination by calcium ions during this season. An up to date scope for surveillance monitoring and forecasting regarding the deterioration of coastal aquifers is recommended. Modelling of aquifers shifts for the coastal zone should be instituted as a means of ensuring efficient fresh water resources evaluation and utilization. An indepth study of the geochemical characteristics of ground water of the coastal zone could determine factors that most significantly impact on fresh water resource quality.

BackgroundDisentangling the relative importance of environmental variables and interspecific interaction in modulating co-occurrence patterns of sympatric species is essential for understanding the mechanisms of community assembly and biodiversity. For the two sympatric Galliformes, Silver Pheasants (Lophura nycthemera) and White-necklaced Partridges (Arborophila gingica), we know little about the role of habitat use and interspecific interactions in modulating their coexistence.MethodsWe adopted a probabilistic approach incorporating habitat preference and interspecific interaction using occupancy model to account for imperfect detection, and used daily activity pattern analysis to investigate the co-occurrence pattern of these two sympatric Galliformes in wet and dry seasons.ResultsWe found that the detection probability of Silver Pheasant and White-necklaced Partridge were related to habitat variables and interspecific interaction. The presence of Silver Pheasant increases the detection probability of White-necklaced Partridge in both the wet and dry season. However, the presence of White-necklaced Partridges increases the detection probability of Silver Pheasants in the wet season, but decreases the probability in the dry season. Further, Silver Pheasants were detected frequently in the sites of high values of enhanced vegetable index (EVI) in both the wet and dry season, and in sites away from human residential settlement in the wet season. White-necklaced partridges were mainly detected in low EVI sites. The site use probabilities of two Galliformes were best explained by habitat variables, Silver Pheasants and White-necklaced Partridges preferred steeper areas during the wet and dry season. Both species mainly occurred in low EVI areas during the wet season and occupied sites away from the resident settlement during the dry season. Moreover, the site use probabilities of two species had opposite relationships with forest canopy coverage. Silver Pheasants preferred areas with high forest canopy coverage whereas White-necklaced Partridges preferred low forest canopy coverage in the dry season, and vice versa in the wet season. Species interaction factor (SIF) corroborated weak evidence of the dependence of the site use of one species on that of the other in the either dry or wet season. Temporally, high overlapping of daily activity pattern indicated no significantly temporal niche differentiation between sympatric Galliformes in both wet and dry seasons.ConclusionsOur results demonstrated that the presence of two species influenced the detection probability interactively and there was no temporal partitioning in activity time between Silver Pheasants and White-necklaced Partridges in the wet and dry seasons. The site use probability of two Galliformes was best explained by habitat variables, especially the forest canopy coverage. Therefore, environmental variables and interspecific interaction are the leading drivers regulating the detection and site use probability and promoting co-occurrence of Silver Pheasants and White-necklaced Partridges.

The study aimed to determine pathological conditions across two seasons, leading to condemnations of beef edible red offals in Kgatleng District, Botswana. Offals are valued in communities of Botswana. Data from slaughter facilities was evaluated for dry/winter and wet/summer seasons. Financial losses were also determined. 7405 cattle were processed in the two seasons, with 4005 cattle slaughtered in the dry season and 3400 in the wet season. Of the slaughtered cattle, 55.2% (2209) of the dry season and 45% (1531) of the wet seasonhad some forms of pathological conditions that led to condemnations of the offals. Lungs were highly condemned at 26.2% in the wet season and 32.7% during the dry season, followed by livers at 16.2 and 18.4% in the wet and dry seasons, respectively. Emphysema led to a condemnation rate of lungs at 20% and 17% for the dry and wet seasons, respectively. The least condemned offals were the spleen at 2.3% (wet season) and 2.1% (dry season), followed by the kidneys at 0.3% (wet season) and 2% (dry season). Financially, the dry season losses were relatively higher at BWP62 950.55 compared to the wet season at BWP43 863.95. Management strategies should be put in place to avail offals to consumers. Key words: Beef, edible red offals, pathological conditions, wet and dry seasons.

Gastrointestinal nematode (GIN) infestations are a major constraint to sheep production in the West Indies (WI). Intensive and semi-intensive management systems are most commonly employed. These islands display tropical weather patterns with wet and dry seasons. Semi-intensive farming combined with increased rainfall during the wet season has been reported to be most favourable for development and survival of GIN. This study was conducted to determine whether there was a relationship between GIN burdens in sheep with seasonality and management practices of farmers in Trinidad and Tobago (T&T). Farms were visited on a monthly basis from January to December 2017. A maximum of ten sheep, three to nine months of age, were selected from each farm. A total of 3,053 faecal samples were collected and analysed using the Modified McMaster technique. Environmental data on daily precipitation and temperature were collected from the Trinidad and Tobago Meteorological Office during the period of sampling. A mixed effects negative binomial regression model was constructed to analyse the relationship between gastrointestinal nematode faecal egg counts (GINFEC) with season, management system and use of dewormers as fixed effects and farm as a random effect. Average diurnal temperatures of T&T fluctuated between 23.2°C to 32.6°C and 23.9°C to 32.3°C in the dry and wet seasons, respectively. Average daily precipitation ranged between 1.6-1.8mm and 6.1-8.5mm during the dry and wet seasons, respectively. A decreased risk of 0.34 (95% CI 0.25-0.47, p<.0001) for GINFEC was observed in dewormed animals versus not dewormed. Semi-intensive management systems experienced an increased risk of GINFEC by 1.39 (95% CI 1.05-1.84, p=.021) compared with intensive and the risk of GINFEC was reduced by 0.40 (95% CI 0.33-0.49, p<.0001) in the wet season versus the dry. A higher prevalence of GIN was observed during the drier months of the year. Climatic conditions observed in T&T remained favourable for GIN survival, development and distribution year-round. Proper management is therefore required for reducing the occurrence of GIN in sheep of T&T throughout the year. This is the first reported study in the WI on the influence of seasonality and management on GIN infestations in sheep during the dry and wet seasons. Further investigation is needed to elucidate why GIN burdens appear to be higher in the dry season than the wet season. This study can be used as a baseline for public education in T&T as well as other developing countries.

This study was conducted to evaluate the impact of seasonal variations (wet and dry season) on the reproductive and productive performance and to do an economic evaluation of hair sheep under Halaieb rangeland conditions and determine which season is the best in grazing areas. A total of 64 multiparous Abou-Delik ewes were bred in two different seasons. During the first season (dry season), a total of 35 ewes, 2-4years of age and 32.02 0.52 kg weight, were bred during May and June, while lambing and lactation took place in the months of November, December and January. On the other hand, during the wet season, 29 ewes, 2-4years age and 31.06 0.57 kg weight, were bred during November and December, whereas lambing and lactation took place in the months of May, June and July. Sheep grazed 8 h daily in the same pastures during the study and then moved back to the barns to receive a sorghum vulgare supplement with a dosage of 250 g per head per day. The results revealed that there were no significant effects of breeding season on conception, lambing and abortion rates. However, the wet season had higher ( ) prolificacy, mortality rates, lambs' weight and lambs born to ewes serviced. Contrariwise, dry-season lambs had a higher ( ) weaning weight. Also, milk yield (mL d ) and number of lambs weaned per lambs born (LW/LB) increased ( ) in the dry season compared to the wet season. No significant differences between the two seasons regarding the biological criteria studied were observed. On the other hand, the flock bred in the dry season generated a higher gross margin than that bred in the wet season. In this context, variable costs of the wet breeding season flock were recorded to be close to the value of the dry breeding season. Hence, it is concluded that the reproductive and productive performance of hair sheep raised in grazing areas in the Halaieb triangle is affected when lambs are born during the dry season because of the higher lamb mortality rate during this period which eliminates any comparative advantage for the good reproductive performance of ewes during the period of feed availability in the wet season. The high lamb mortality rates and low weaning weights in the wet breeding season lessen the economical merits of higher reproductive performance during the seasonal availability of feed in the wet season.

As a part of an Australian Centre for International Agricultural Research (ACIAR) project on management of aflatoxin in Indonesia and Australia (PHT 97/017), a survey on pre- and postharvest handling of peanuts at farmer, collector retailer levels, including Aspergillus flavus  infection and aflatoxin B1 contamination of peanuts collected in Wonogiri regency, Central Java, was conducted during the harvest period of the wet (February 2003) and dry (June 2003) seasons. Interviews using questionnaires, with farmers, collectors and retailers concerning pre- and post-harvest handling of peanuts were carried out. The moisture contents and physical quality of the peanut kernels were also determined. During the wet and dry seasons, fresh pod samples were collected from farmer fields (24 samples), dry raw pod samples from collector (24 samples) and raw kernel samples from retailer levels (54 samples). Thus, during each season 102 samples of various kinds of peanuts were collected for analysis. The A. flavus infection in kernel samples of peanuts collected from retailers were the highest, followed by samples collected from collectors and farmers. The A. flavus infection in kernel samples collected during the dry season was in general lower than in the wet season. It was alarming to note that all most all samples of raw kernel samples collected from retailers were infected by A. flavus during the wet and dry seasons. In general aflatoxin B1 levels in peanut samples collected in the wet season were higher than the dry season. During the wet and dry seasons, the aflatoxin B1 contents in retailer samples were the highest, followed by those collected from collectors and farmers. During the wet season, around 4, 17 and 33% of peanut samples collected from farmers, collectors and retailers, were respectively contaminated with more than 15 ppb of aflatoxin B1. During the dry season, around 42 and 74% of peanut samples collected from collectors and retailers, were respectively contaminated with more than 15 ppb of aflatoxin B1, while aflatoxin levels in wet raw pod samples collected from farmers were less than 15 ppb. In 2003 Codex Alimentarius Commission has determined a maximum level of total aflatoxins in peanuts intended for further processing at 15 ppb.

PDF HTML阅读 XML下载 导出引用 引用提醒 北部湾近岸海域浮游动物群落结构特征及季节变化 DOI: 10.5846/stxb201807191553 作者: 作者单位: 广西壮族自治区海洋环境监测中心站,广西壮族自治区海洋环境监测中心站,广西壮族自治区海洋环境监测中心站,广西壮族自治区海洋环境监测中心站 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(41466001);广西科技计划项目(桂科AA17129001,桂科AD17129041,桂科AB16380340) Community structure and seasonal variation of zooplankton in coastal Beibu Gulf Author: Affiliation: Marine Environmental of Monitoring Center of Guangxi,Marine Environmental of Monitoring Center of Guangxi,Marine Environmental of Monitoring Center of Guangxi,Marine Environmental of Monitoring Center of Guangxi Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:2017年3月(枯水期)、7月(丰水期)和10月(平水期)分别对北部湾近岸海域44个站位的浮游动物进行了调查。结果共检出浮游动物251种和浮游幼体24类,其中枯水期138种(类),丰水期134种(类),平水期191种(类),分属河口低盐、近岸暖温、近岸暖水和外海暖水4个生态类群。优势种9种,其中枯水期以原生动物占绝对优势,丰水期以枝角类、桡足类和浮游幼体类占优势,平水期以十足类和浮游幼体类占优势。浮游动物丰度年均值为789.95个/m3,呈现出枯水期(1540.19个/m3)明显高于平水期(457.58个/m3)和丰水期(372.08个/m3)的季节变化特征;浮游动物生物量年均值为252.40 mg/m3,生物量的季节变化与丰度变化不一致,平水期生物量(385.01 mg/m3)明显高于枯水期(221.41 mg/m3)和丰水期(150.78 mg/m3)。多样性指数平水期最高(3.16),丰水期(2.35)次之,枯水期(2.22)最低。枯水期和丰水期北部湾近岸海域浮游动物生物量和丰度水平分布特征基本呈现自河口近岸海域向外海递增的趋势,平水期浮游动物生物量与丰度的空间分布较为均匀。浮游动物的种类组成结构以及优势种的演替对浮游动物的生物量和丰度季节变化有着重要的决定作用。径流导致的悬浮物、营养盐等的变化可能是决定北部湾近岸海域浮游动物生物量和丰度空间分布的主要因素。研究还表明与其他海湾相比,北部湾近岸海域浮游动物群落结构趋于小型化,需加大关注。 Abstract:A comprehensive investigation on the population of zooplankton was conducted at 44 stations in the Beibu Gulf coastal area in the dry,wet and normal seasons in 2017. In total,251 zooplankton species including 24 larvae were identified during the investigation,among which 138,134,and 191 species occurred in the dry,wet and normal seasons,respectively. All zooplankton could be grouped into four ecotypes:estuary,offshore warm-water, offshore warm-temperature and eurytopic. There were 9 dominant species during the sampling period,with protozoa dominating the community in dry season,Cladocera,Copepoda and pelagic larvae dominating in the wet season, Decapoda and pelagic larvae in the normal season.The annual average abundance of zooplankton was 789.95 ind./m3. Dry season had the largest abundance (1540.19 ind./m3), followed by normal (457.58 ind./m3) and wet (372.08 ind./m3) seasons. The annual average biomass of zooplankton was 252.40 mg/m3, with the highest biomass during normal season (385.01 mg/m3),followed by dry (221.41 mg/m3) and wet (150.78 mg/m3) seasons.The highest diversity index (3.16) was found in normal season, followed by wet season (2.35), while the least diversity (2.22) presented in the dry season. Both the horizontal distribution of biomass and abundance of zooplankton increased gradually moving offshore in dry and wet seasons, while remaining relatively evenly distributed in normal season. Seasonal variation of biomass and abundance was determined by composition and dominant species. Correlation analysis shows that the distribution of biomass and abundance of zooplankton in the coastal waters of Beibu gulf are influenced by suspended matter and nutrients. Compared with the other bays, the population structure of zooplankton in the coast of the Beibu Gulf exhibited a clear tendency toward miniaturization that require additional attention. 参考文献 相似文献 引证文献

High-fluoride (F-) deep groundwater in the vicinity of mining areas poses severe ecological risks. In this study, we aimed to characterize and reveal the seasonal distribution and influencing factors of elevated F- concentrations in the deep groundwater in the Shendong mining area, Shaanxi and Inner Mongolia province, China. In addition, the ecological risks associated with F- concentrations in irrigation water were assessed. During the wet and dry seasons, the F- concentrations in mine water samples ranged between 0.12 and 13.92 mg/L (mean: 4.24 mg/L) and between 0.20 and 17.58 mg/L (mean: 4.59 mg/L), respectively. The F- content of mine water was clearly higher during the dry season than that during the wet season. F- concentrations in deep groundwater exhibited consistent spatial distributions during both the dry and wet seasons, with an evident increase from southeast to northwest. The dissolution and precipitation of F--bearing and calcium minerals, cation exchange, competitive adsorption, evaporation, and anthropogenic activities during both the wet and dry seasons were identified as important factors influencing F- concentrations in deep groundwater. In addition, the ecological assessment revealed that 100% and 88.89% of low-F- deep groundwater samples were suitable for practices during the dry and wet seasons, respectively. In contrast 84.00% and 84.62% of high-F- deep groundwater samples were unsuitable for irrigation practices during the dry and wet seasons, respectively. This research provided useful prevention policies of deep groundwater extraction to mitigate environment problems associated with excessive F- irrigation.

The main seasonal characteristics in the tropics include both spatial patterns and temporal parameters of onset, cessation, duration, and the number of wet and dry seasons. Previous studies showed that wet seasons shortened and dry seasons extended with global warming, but the changes in spatial distribution and the number of wet and dry seasons are still unclear. Here, we analyze the climatic characteristics of once wet and dry season a year (annual regime) and twice wet and dry seasons a year (biannual regime), and find that regimes of wet and dry seasons have changed from 1935 to 2014. Across the equator and the Tropic of Cancer and Capricorn, some regions where there used to be an annual regime have become a biannual regime; instead, other regions have shifted from a biannual regime into an annual regime. With seasonal regimes shifting, areas of the biannual regime have expanded at a rate of 31 000 km2/decade. Meanwhile, in annual regime regions, wet seasons have been shortened in 60.3% of regions, with an average of 7 d; the onset dates of wet seasons have been delayed in 64.8%, with an average of 6 d. Besides, wet seasons have become wetter in 51.1% of regions, and dry seasons have become drier in 59.9%. In biannual regime regions, the shortened wet seasons have occurred in 83.7% of regions, with an average shortening of 8 d, and precipitation has decreased in both wet and dry seasons. Moreover, the shorter wet seasons will amplify further by the end of the 21st century. The continuous seasonal changes will threaten agricultural, ecological security, and even human well-being.