Estuary In Spring Research Articles

Species composition and abundances of ichthyolplankton in Yeongsan River Estuary in Spring and Summer

Species composition and abundances of ichthyolplankton in Yeongsan River Estuary in Spring and Summer

Long-Term Passive Acoustic Monitoring to Support Adaptive Management in a Sciaenid Fishery (Tagus Estuary, Portugal)

AbstractPassive acoustic monitoring (PAM) is useful for monitoring vocal fish but has had so far limited application in fisheries management. Here, four years (2016–2019) of concurrent daily catch and effort fishery data in Portugal and species-specific vocal activity in the Tagus estuary are compared to describe biological and small-scale fishery dynamics for a large sciaenid fish, the meagre (Argyrosomus regius), that aggregates to spawn. Consistent patterns in seasonality of acoustic and fisheries variables indicate that most fishing takes place within the Tagus estuary in spring and summer months, when higher vocal activity related to spawning aggregations is detected in the PAM station. Good fit of statistical models shows that PAM (sound pressure level in the third-octave band with centre frequency at 500 kHz during dusk) and PAM-supported variables (mean weekly catch per first sale transaction) can provide useful surveillance indicators to improve local management. Signs of overexploitation and hyperstability are detected and communicated to the estuarine fishing communities with the aim to initiate an adaptive local management cycle. The approach can be relevant for fisheries targeting other vocal fish that seasonally aggregate and face similar threats of overexploitation. Graphical Abstract

Spatial–temporal variability of phytoplankton community and potentially harmful species in the Golden Horn Estuary (Sea of Marmara, Türkiye)

Abstract Spatial–temporal variability of phytoplankton community and potentially harmful species in the Golden Horn Estuary (Sea of Marmara) was investigated from October 2018 to September 2019 together with some environmental factors. A total of 148 phytoplankton taxa were identified during the study period. Among these, 134 taxa (90.5%) consisted of diatoms (71 taxa, 48%) and dinoflagellates (63 taxa, 42.5%), while 14 taxa (9.5%) were other groups. Seventeen species were recorded for the first time in the study area. Species richness was highest in October, while it was lowest in August. The species diversity (H') varied according to sampling stations. Cell abundances were higher especially in the middle and upper estuary in spring and summer than in autumn and winter. The abundance of diatoms and euglenophyceans was highest in spring, while the abundance of raphidophycean and cryptophycean was highest in summer. Temperature was correlated positively with total abundance (P < 0.01), but negatively with species diversity (H') (P < 0.01). Several dense algal blooms causing discolouration in surface water occurred in spring and summer. A total of 12 microalgae species known as potentially toxic were detected during this study period. Among these, dinoflagellates Alexandrium cf. tamarense and Dinophysis infundibulum were recorded for the first time in the study area. The increase in species diversity and richness in the upper estuary, and the decrease in frequency of bloom events compared with the previous years indicated the changes in environmental conditions in this study period. Findings showed that phytoplankton might be used as an indicator of the changing environmental conditions in such ecosystems.

Sea otters in a California estuary: Detecting temporal and spatial dynamics with volunteer monitoring

AbstractVolunteer monitoring can support conservation of imperiled wildlife, by providing higher resolution data in space and time than those available from professional scientists. However, concerns have been raised that data collected by amateurs are inaccurate or inconsistent and thus do not allow for robust detection of spatial or temporal trends. We evaluated the rigor and value of volunteer monitoring data for one iconic wildlife species, the southern sea otter (Enhydra lutris nereis), in Elkhorn Slough estuary in central California, USA, and explored whether volunteer monitoring could provide added value to complement limited professional surveys. First, we compiled and analyzed sea otter counts taken on daily ecotourist boat trips along the estuary, and then compared temporal patterns to data collected by professional scientists tasked with monitoring this federally listed species. Second, we analyzed data on sea otter abundance, habitat use, and behavior collected by a team of trained volunteers, the Elkhorn Slough Reserve Otter Monitoring Program. Overall, we demonstrated the ability to detect important ecological patterns relevant to sea otter conservation and wetland habitat management using volunteer‐derived datasets. Long‐term trends and inter‐annual variability were similar between professional agency monitoring data and volunteer datasets. Moreover, the much higher frequency of volunteer observations allowed for seasonal and tidal dynamics to be detected that could not be revealed by less frequent professional monitoring. We found higher sea otter abundance in the estuary in spring–summer, indicating seasonality in use of the estuary. We detected differences in habitat use of the estuary between higher and lower tides, and greater frequency of foraging at low tide and in certain areas. Volunteer observations revealed fine‐scale differences in habitat use: eelgrass beds were used much more heavily than adjacent areas only a few meters away. Volunteer data can thus provide critical information about coastal habitat use and behavior that can improve conservation strategies for threatened wildlife species.

Spring Ichthyoplankton Assemblage Structure in the Yangtze Estuary Under Environmental Factors

Estuaries, where fresh and salty water converge, provide abundant nutrients for ichthyoplankton. Ichthyoplankton, including fish eggs, larvae, and juveniles, are important fishery recruitment resources. The Yangtze Estuary and its adjacent waters comprise a typical large-scale estuary and supply many important fish spawning, feeding, and breeding areas. In this study, 1,291 ichthyoplankton individuals were collected in the Yangtze Estuary in spring, from 2013 to 2020. The aims of the study were to provide detailed information on characteristics of the ichthyoplankton assemblage, explore interannual variation, and evaluate the effects of environmental variables on the temporal variation in assemblage structure. Twenty-six species in seventeen families were identified. The dominant species were Coilia mystus, Chelidonichthys spinosus, Engraulis japonicus, Hypoatherina valenciennei, Larimichthys polyactis, Salanx ariakensis, Stolephorus commersonnii, and Trachidermus fasciatus. The ichthyoplankton assemblage changed significantly over time, and Chelidonichthys spinosus became one of the dominant species. Canonical correspondence analysis showed that temperature and chlorophyll a were the key factors affecting the assemblage structure in the Yangtze Estuary in spring.

Assemblage Structure of the Ichthyoplankton and Its Relationship With Environmental Factors in Spring and Autumn off the Pearl River Estuary

Ichthyoplankton assemblages and their relationship with environmental variables are investigated in waters off the Pearl River Estuary in spring and autumn of 2019. Of 80 ichthyoplankton taxa identified using DNA barcode and morphological methods, 61 are identified to species. The most abundance families (Carangidae, Trichiuridae, Mullidae, and Scombridae) account for 61.34% of the horizontal total catch in spring, while Menidae and Carangidae are the most abundant families identified in autumn, accounting for 89.72% of the horizontal total catch. Cluster analysis identifies three species assemblages in spring, and four in autumn based on horizontal trawls. Relationships between assemblage structure and environmental variables (in situ and remote sensed) are determined by canonical correspondence analysis. Ichthyoplankton assemblage structure appears to be strongly influenced by sea level anomalies, salinity, water depth, temperature at 10 m depth, and distance from shore. We demonstrate the efficacy of using DNA barcode to identify ichthyoplankton, and suggest how these data can be used to protect fish spawning grounds in waters off the Pearl River Estuary.

Molecular and Morphological Identification and Seasonal Distribution of Eggs of Four Decapterus Fish Species in the Northern South China Sea: A Key to Conservation of Spawning Ground

Although species of Decapterus form important pelagic fisheries in the northern South China Sea, information on their spawning grounds is limited because identification of fish eggs based on their morphology is difficult. We identify eggs of four Decapterus species (D.macrosoma, D.maruadsi, D.macarellus, and D.tabl) with DNA barcodes from the fishery resources surveys in Spring and Autumn 2018 in Xisha islands, and Spring and later summer-Autumn 2019 along the continental shelf of the northern South China Sea, and describe egg morphology. Of 1405 fish eggs with obtained COI sequences, 81 were successfully attributed to four Decapterus species; eggs of each are spherical, have a smooth chorion and narrow perivitelline space, and can be partly differentiated by diameter, melanophore drops on the oil globule, and the notum of the embryo. Seasonal distributions of eggs reveal spawning grounds, with that of D.maruadsi located mainly off the Pearl River estuary in spring; eggs of D. maruadsi rarely co-occur with those of D.macrosoma. Spawning grounds of D.macrosoma are probably further south, where water temperature and salinity are higher. Spawning periods of these four Decapterus species overlap slightly. Spawning habitat D.maruadsi has been lost, and the spawning season of D.macrosoma has extended. Identification of Decapterus eggs using DNA barcodes can assist with the identification of eggs using traditional morphological approaches. Spatial and temporal information on the distributions of Decapterus eggs can be used for improved conservation of spawning grounds and fisheries management in the northern South China Sea.

Disentangling effects of river inflow and marine diffusion in shaping the planktonic communities in a heavily polluted estuary

Estuarine ecosystems are important in terms of biodiversity processes because there are intense interactions between the river and sea environments. Phytoplankton and zooplankton have been shown to be ecological indicators of the water quality status in estuary ecosystems. Therefore, a comprehensive evaluation of the effects that multiple pressures have on the phytoplankton and zooplankton communities in estuarine ecosystems is essential. In this study, water samples from 29 stations were collected from the Liaohe Estuary over three different seasons, and biotic factors (i.e., phytoplankton and zooplankton) were obtained and compared. The results showed that there were significant temporal and spatial variations in the phytoplankton and zooplankton communities from the Liaohe Estuary. The correlation analyses showed that water temperature was the most important factor regulating the variation in phytoplankton communities, whereas the main driving force for the zooplankton was nutrient concentrations. Large amounts of nutrients entered the estuary in spring and summer due to intensive human activities in the Liaohe River basin. The inflows by the Liaohe River introduced some phytoplankton and zooplankton into the estuary, such as Coscinodicus asteromphalus, Chaetoceros decipiens, and Schmacheria poplesia. The impacts of Liaohe inflows on the estuary region gradually decreased as the distance from the inlet increased and this change was mediated by marine diffusion. The results from this study will improve knowledge about planktonic communities in estuarine ecosystems and provide a theoretical foundation for estuary environmental management.

금강 하구역의 춘계와 하계에 어류플랑크톤 종조성과 출현량

Ichthyol-plankton and the environment data were collected in Geum River Estuary in spring and summer of 2016~2018. These data were collected though “National Survey of Marine Ecosystem” project. Geum River Estuary is one of the main estuaries in the West Sea of Korea. A total of 18 taxa of fish larvae were collected. Eight taxa were collected in spring, and the mean abundance was 242 ind./1,000m3. Thirteen taxa were collected during the summer, and the mean abundances was 109 ind./1,000m3. During this study, most dominant species was Gobiidae spp. (49.4%), which was followed by whiting, Sillago japonica (37.3%). Yearly species composition showed Gobiidae spp. was most dominant specie except in 2018. In 2018, Sillago japonica was dominant in spring and anchovy (Engraulis japonicus) was dominant in summer. When abnormal high water temperature period (>28℃) occurred, Gobiidae spp. was not dominant.

Characteristics of Absorption Spectra of Chromophoric Dissolved Organic Matter in the Pearl River Estuary in Spring

In this study, absorption variation of chromophoric dissolved organic matter (CDOM) was investigated based on spectroscopic measurements of the water surface and bottom during a cruise survey on 2–12 May 2014 in the Pearl River Estuary (PRE). Multiple spectral signatures were utilized, including the absorption ratios E2/E3 (a(250)/a(365)) and E2/E4 (a(254)/a(436))) as well as the spectral slopes over multiple wavelength ranges. The horizontal variations of a(300), E2/E3, spectral slope (S) of Ultraviolet C (SUVC, 250–280 nm), Ultraviolet B (SUVB, 280–315 nm), and S275–295 (275–295 nm) were highly correlated, revealing that CDOM of terrigenous origin in the upper estuary contained chromophores of larger molecular size and weight, while the marine CDOM in the lower estuary comprised organic compounds of smaller molecular size and weight; the molecular size of surface CDOM was generally larger than that at the bottom. Results of Gaussian decomposition methods showed that CDOM in the middle estuary of terrigenous origin produced more Gaussian components per spectrum than those of marine origin in the lower estuary and the adjacent Hong Kong waters. The surface CDOM composition was more diverse than at the bottom, inferred by the finding that the average number of Gaussian components yielded per surface sample (5.44) was more than that of the bottom sample (4.8). A majority of components was centered below 350 nm, indicating that organic compounds with relatively simple structures are ubiquitous in the estuary. Components centered above 350 nm only showed high peaks at the head of the estuary, suggesting that terrigenous CDOM with chromophores in complex structures rapidly lose visible light absorptivity during its transport in the PRE. The relatively low and homogenous peak heights of the components in Hong Kong waters imply higher light stability and composition consistency of the marine CDOM compared with the terrigenous CDOM.

Temporal variation in the composition and abundance of fish larvae and juveniles off the Yangtze River Estuary in spring and summer

PDF HTML阅读 XML下载 导出引用 引用提醒 春夏季长江口邻近水域仔稚鱼种类组成和丰度的月变化 DOI: 作者: 作者单位: 中国水产科学研究院东海水产研究所, 农业部东海渔业资源开发与利用重点实验室, 上海 200090 作者简介: 李建生(1976-),副研究员,从事渔业资源与生态学研究.E-mail:jianshengli@sina.com 通讯作者: 中图分类号: S931 基金项目: 国家公益性行业（农业）科研专项经费项目（201303047）. Temporal variation in the composition and abundance of fish larvae and juveniles off the Yangtze River Estuary in spring and summer Author: Affiliation: East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences;Key Laboratory of East China Sea Fishery Resources Exploitation, Ministry of Agriculture, Shanghai 200090, China 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:利用2015年4—7月在长江口邻近水域的调查数据，对春夏季该水域仔稚鱼种类组成和丰度的月变化特征进行了观测。结果表明，共采获62种、35839尾仔稚鱼，分别属于14目、30科、45属。各月种类数范围为22~36种，从4月到6月，先是缓慢增加然后快速增加，至6月达到高峰期，7月则大幅降低。各月的丰度范围为11.45~114.31 ind/（100 m3）；丰度随时间的推移而持续增加。各月主要种类数范围为5~13种，具有较大的波动性；优势种主要为小黄鱼（Chaeturichthys hexanema）、鳀（Acanthogobius ommaturus）、（鱼衔）属（ sp.）等。优势种随时间推移表现出较大的更替性。种类数以20 m以浅水域最多，不同水深范围的月变化有一定的差异性。20 m以浅海域的种类数与表层水温的关系在4—6月为显著正相关（=-0.91，<0.05）。从春季到夏季，仔稚鱼高丰度区从浅水区向深水区转移。 Abstract:The present study investigated the monthly variation in species composition and abundance of fish larvae and juveniles from April to July 2015 off the Yangtze River Estuary. A total of 35839 larvae and juveniles were collected, and these included 62 species from 45 genera, 30 families, and 14 orders. Species richness ranged from 22 to 36, depending on month, increased from April to June, and then declined sharply in July. Meanwhile, the total abundance of larvae and juveniles ranged from 11.45 to 114.31 individuals per 100 m3 and increased throughout the study period, with small increases during the first three months and a greater increase in July. The number of dominant species varied by month, ranging from 5 to 13, and the dominant species mainly included Chaeturichthys hexanema, Engraulis japonicus, Odontamblyopus rubicundus, Acanthogobius ommaturus, and sp.. The dominant species showed greater replacement over time. The greatest species richness was observed in the nearshore water (<20 m depth), and the spatial pattern of species richness along the depth gradient varied among months. Surface temperature and species richness were positively correlated (<0.05) from April to June but negatively correlated from June to July, and in every month, abundance and surface salinity were negatively correlated (<0.05) in the nearshore water (<20 m depth). The high-abundance region shifted away from the shore over time. 参考文献 相似文献 引证文献

Diversity and distribution of the planktonic diatom genus Chaetoceros (Bacillariophyceae) in the Golden Horn Estuary (Sea of Marmara)

The diversity and distribution of the diatom genus Chaetoceros (Bacillariophyceae) was studied at monthly, bi-weekly and weekly intervals over two periods (2009–2010, 2013–2014) in the Golden Horn Estuary. Chaetoceros was the most diverse genus in the diatom assemblage of the study area. A total of 23 Chaetoceros species were identified based on light and scanning electron microscopy. Three taxa, Chaetoceros aequatorialis, C. contortus and C. lorenzianus f. forceps were recorded for the first time in Turkish seas. The most common species were C. affinis, C. curvisetus, C. decipiens and C. holsaticus. The contribution of Chaetoceros species to the number of total phytoplankton species was between 15% and 17%. The highest abundance of Chaetoceros species was 507 × 103 cells L−1, dominated by C. affinis, C. constrictus, C. holsaticus, C. lauderi in the middle estuary in spring. Chaetoceros species were more abundant in the middle and lower estuary in April and May. In the upper estuary (UE), Chaetoceros species were rarely observed due to low water transparency caused by suspended particulate materials. Light limitation may be considered one of the most important factors affecting the diversity and spatial distribution of these species in the UE. The present work is the first detailed study on the diversity and distribution of Chaetoceros species for Turkish seas.

Change characteristics of DSi and nutrition structure at the Yangtze River Estuary after Three Gorges Project impounding and their ecological effect

Abstract The variation law of dissolved silica (DSi), dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and nutrition structure after the Three Gorges Project (TGP) impounding as well as their ecological effect were analyzed according to monitoring survey of the Yangtze River Estuary in spring (May) and summer (August) from 2004-2009. The results showed that after impounding, DSi and DIN concentration decreased and increased, respectively. During the study period, DSi decreased by about 63%, while DIN almost tripled. DIP concentration fluctuated slightly. With respect to nutrition structure, N:P increased, whereas Si:P and Si:N declined. According to chemometry standard of nutrient limits, nutrition structure tended to be imbalanced and the limiting factor of phytoplankton growth (P) was studied. Changes of nutrition structure have largely decreased diatom and caused different composition of dominant phytoplankton species. This may change ecosystem structure of the Yangtze River Estuary.

Phthalate esters in water and surface sediments of the Pearl River Estuary: distribution, ecological, and human health risks.

The Pearl River Estuary (PRE) is vulnerable due to the increasingly serious environmental pollution, such as phthalate esters (PAEs) contaminants, from the Pearl River Delta (PRD). The concentrations of six US Environmental Protection Agency (USEPA) priority PAEs in water and surface sediments collected from the PRD's six main estuaries in spring, summer, and winter 2013 were measured by GC-MS. Total PAEs (∑6PAEs) concentrations were from 0.5 to 28.1μg/L and from 0.88 to 13.6μg/g (dry weight (DW)) in water and surface sediments, respectively. The highest concentration was detected in summer. Higher concentrations of PAEs were found in Yamen (YM) and Humen (HM) areas than the other areas. Bis(2-ethylhexyl)phthalate (DEHP) and dibutyl phthalate (DBP) were the dominant PAEs in the investigated areas, contributing between 61 and 95% of the PAEs in water and from 85 to 98% in surface sediments. Based on risk quotients (RQs), DEHP posed greater ecological risks to the studied aquatic environments than other measured compounds. Little human health risk from the target PAEs was identified.

Phytoplankton pigments and functional community structure in relation to environmental factors in the Pearl River Estuary

Summary Two cruises were undertaken in the Pearl River Estuary in November 2011 and March 2012 to analyze the distribution of phytoplankton pigments and to define the relationships of pigment indices and functional community structure with environmental factors. Among 22 pigments, 17 were detected by high-performance liquid chromatography. Chlorophyll a was found in all samples, with a maximum of 7.712 μg L −1 in spring. Fucoxanthin was the most abundant accessory pigment, with mean concentrations of 2.914 μg L −1 and 0.207 μg L −1 in spring and autumn, respectively. Chlorophyll a , chlorophyll c 2 , fucoxanthin, diadinoxanthin, and diatoxanthin were high in the northern or northwest estuary in spring and in the middle-eastern and northeast estuary in autumn. Chlorophyll b , chlorophyll c 3 , prasinoxanthin, and peridinin were similarly distributed during the two cruises. Chlorophyll a and fucoxanthin positively correlated with nutrients in spring, whereas 19′-hex-fucoxanthin and 19′-but-fucoxanthin negatively correlated. The biomass proportion of microphytoplankton (BP m ) was higher in spring, whereas that of picophytoplankton (BP p ) was higher in autumn. BP m in spring was high in areas with salinity p and the biomass proportion of nanophytoplankton (BP n ) were high in areas with salinity >30. BP m increased but BP n reduced with the increase in nutrient contents. By comparison, BP p reduced with the increase in nutrient contents in spring, but no relationship was found between BP p and nutrient contents in autumn. The ratios of photosynthetic carotenoids to photoprotective carotenoids in the southern estuary approached unity linear relationship in spring and were under the unity line in autumn.

长江口南支、北支、北港及口外水域浮游动物群聚相似性

PDF HTML阅读 XML下载 导出引用 引用提醒 长江口南支、北支、北港及口外水域浮游动物群聚相似性 DOI: 10.5846/stxb201503190530 作者: 作者单位: 中国水产科学院东海水产研究所农业部海洋与河口渔业重点开放实验室;上海海洋大学海洋学院,中国水产科学院东海水产研究所,中国水产科学院东海水产研究所 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（41176131）；海洋公益性行业科研专项经费项目（201305027） Similarity analysis of zooplankton assemblages among different zones in the Yangtze River estuary Author: Affiliation: Ministry of Agriculture Key and Open Laboratory of Marine and Estuary Fisheries;College of Marine Sciences,Shanghai Ocean University,Ministry of Agriculture Key and Open Laboratory of Marine and Estuary Fisheries,Ministry of Agriculture Key and Open Laboratory of Marine and Estuary Fisheries Fund Project: The foundation was financially supported by the project of National Natural Science foundation(41176131) 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:依据2009-2010年春、秋季在长江口南支、北支、北港以及口外水域的海洋综合调查资料，基于聚类、排序等多元分析方法，对长江口不同水域的浮游动物群聚进行相似性分析。春季，长江口水域的浮游动物群聚在40%相似性程度上可以明显分为口外和口内两组，分别记为Ⅰ、Ⅱ组。位于口外水域的I组受外海水团和长江径流的影响，浮游动物以近海种、沿岸种和河口种为主，如中华哲水蚤（Calanus sinicus，35.30ind/m3）、真刺唇角水蚤（Labidocera euchaeta，34.59 ind/m3）、虫肢歪水蚤（Tortanus vermiculus，42.46 ind/m3）。位于长江口内的Ⅱ组可以进一步分为Ⅱ-1、Ⅱ-2和Ⅱ-3三个组。受长江径流的影响，口内水域的的浮游动物群聚以河口种为主，主要优势种为中华华哲水蚤（Sinocalanus sinensis）。秋季，长江口水域可明显分为Ⅲ、Ⅳ、Ⅴ、Ⅵ 4个组，由于外海势力和长江径流都增大，导致不同水域的水环境差异更大，浮游动物群聚的差异也相对增大。其中，Ⅲ组（北港水域）以河口种为主，主要种类为虫肢歪水蚤，丰度为3.08个/m3；Ⅳ组（北支水域）因受长江径流影响较小，盐度较高，以沿岸种为主，主要种类为针刺拟哲水蚤（Euconchoecia aculeata），丰度为4.97个/m3；Ⅴ组（口外水域）受外海水团和台湾暖流的影响，以外海种和近海种为主，外海种主要有亚强次真哲水蚤（Subeucalanus subcrassus）等，近海种主要有中华哲水蚤等；受长江径流的强烈影响，Ⅵ组（南支水域）以淡水种为主，主要种类为汤匙华哲水蚤（Sinocalanus dorrii），其优势度高达0.93，是该水域的关键种。可以看出，盐度和水团是导致长江口浮游动物群聚在不同水域产生差异的主要因素。 Abstract:Similarity analyses were performed on zooplankton communities in the South Branch (SB), North Branch (NB), North Channel (NC), and offshore area (OS) of the Yangtze River estuary based on the survey conducted during spring and autumn from 2009 to 2010. According to the results of the hierarchical cluster analysis and non-metric multidimensional scaling. The zooplankton species occurring in this estuary in spring can be divided into two communities:I and Ⅱ.. Community I in OS is significantly different from community Ⅱ. Community I was dominated by offshore zooplankton species, e.g., Calanus sinicus (density of 35.30 ind/m3), which may be due to the effect of water masses. Few estuarine and coastal species were also observed during this period. As a result of the Yangtze River runoff, community Ⅱ was dominated by estuarine species; this community can be further divided into community Ⅱ-1 (NC), Ⅱ-2 (NB), and Ⅱ-3 (SB). Sinocalanus sinensis was the most dominant species across these subcommunities, present at varying densities. The differences in estuarine communities were mainly caused by the adaption of S. sinensis to freshwater environment. In autumn, the communities of the Yangtze River could be distinctly divided into four clusters:Ⅲ, Ⅳ, Ⅴ, and Ⅵ. Owing to the stronger runoff and the offshore water mass, there were considerable differences from the dominant species which led to form the different communities. Estuarine species prevailed in community Ⅲ (NC), with Tortanus vermiculus observed as the dominant species (3.08 ind/m3). Due to the small impact of the Yangtze River Runoff and with a high salinity in the waters of NB, community Ⅳ was mainly composed of coastal species. Furthermore, owing to the effects of offshoe currents and water mass, community Ⅴ (OS) was dominated by offshore species such as Calanus sinicus and marine species such as Subeucalanus subcrassus and Sagitta enflata. As a result of the stronger runoff of the Changjiang River, freshwater species dominate community Ⅵ (SB). Sinocalanus dorrii was the key species of community Ⅵ, with a high dominance(0.93). Thus, salinity and water masses were considered key factors to cause differences in zooplankton communities in the Yangtze River Estuary, and the differences between the offshore area and the estuarine areas were larger than those in the estuarine areas. 参考文献 相似文献 引证文献

Evaluation of primary production in the estuaries of the Razdolnaya/Suifen and Sukhodol Rivers (Peter the Great Bay, Japan Sea)

Production-destruction balance is determined and primary production is evaluated for different parts of the estuaries of two rivers with different hydrological regime in Peter the Great Bay basin (Razdolnaya/Suifen and Sukhodol) in different seasons on the data of chemical surveys conducted in 2010-2013. The values of production and destruction are calculated from the difference between observed nutrients (phosphorus) concentration in the estuaries and their potential concentration conditioned by the river water dilution. The nutrients concentration in the water passing through estuaries increased in their upper parts over the potential values due to the nutrients influx from destruction, then decreased below the potential values because of the consumption for photosynthesis. Production processes prevailed over the estuaries in spring, the sign of production-destruction balance changed in summer from destruction in the upper estuaries to production in the lower estuaries, and destruction processes prevailed in autumn-winter. Productivity of the Razdolnaya/Suifen estuary is based mainly on utilization of terrigenous nutrients dissolved in its highly mineralized water, but in the Sukhodol estuary the nutrients of terrigenous origin are consumed quickly and its productivity is maintained by recycling of nutrients. Passing the estuaries, 1 m 3 of both rivers water produces on average 0.8-1.0 gС/m 3 km that corresponds to values of primary production up to 5.6 gC/m 3 day in summer, with the maximum in the upper parts of the external estuaries under salinity 5-10 ‰, at the haline front dividing almost fresh water of the internal estuary from brackish water of the external estuary. Taking destruction of organic matter into account, net production is mostly below zero in the river parts of estuaries, particularly in autumn, it reaches the maximum in the upper part of external estuaries (up to 0.7-1.0 gC/m 3 km or 3-5 gC/m 3 day) and remains on lower but positive level further offshore. So, estuaries are simultaneously «marginal filters» limiting penetration of terrigenous nutrients into the sea and «factories of nutrients»: the latter process dominates in their internal parts and enhances considerably biological productivity of these water bodies.

Patterns of nutrients distribution along salinity gradient in the estuaries of the rivers Sukhodol and Razdolnaya/Suifen (Peter the Great Bay, Japan Sea)

Sign of production-destruction balance is determined for different parts of two rivers estuaries in Peter the Great Bay (Razdolnaya/Suifen and Sukhodol) on the data of chemical samplings in different seasons of 2010-2013. For this purpose, the nutrients concentration dependence on ratio of river and sea waters mixing is determined. In the case of conservative behavior of nutrients, their concentration should have negative linear dependence on increasing salinity, but its non-linearity shows removal or addition of the nutrients by processes of biological production or destruction: negative deviations indicate production and positive deviations indicate destruction. The concentration of mineral nitrogen is close to zero everywhere in the estuaries in spring, so below the line of conservative behavior that is the evidence of active nitrogen consumption. Patterns of silicon and phosphorus distribution are similar to the distribution of nitrogen. Summer nutrients concentrations are mainly below the conservative values, as well, with exception of the areas at the river bar, so production prevails in the external estuaries of both rivers, but remineralization prevails in the lower parts of the internal estuaries in this season. In autumn, destruction of organic matter becomes more important in both estuaries, so heightened values of nutrients are observed in all their parts, in particular in the «silicon belt» of brackish water (≈ 13-17 eps). The silicon concentration increasing at the river bar (above the concentration in the river water) is the most significant in the Razdolnaya estuary which is generally poor by this nutrient. There is concluded that terrigenous nutrients of the river water are utilized for new production mostly in the external estuaries, whereas the process of organic matter mineralization dominates in the internal estuaries. Besides of the production-destruction processes, changes of the mineral silicon concentration are determined by transformation of its inorganic forms, as dissociation of low-soluble silicates to silicon acid under heightened pH. Principal difference of the production-destruction balance between the internal and external parts of estuary could be an ecological basis for formation of different ecosystems in these zones, with principally different structure and functioning patterns.

Northward drift of suspended sediments in the Yangtze estuary in spring

The spatial distribution of suspended sediment concentration (SSC) in spring (February–April) from 2007 to 2013 in the Yangtze (Changjiang) estuary and coastal seas was analysed using remote-sensing data. The results indicated that areas of high SSC drifted northwards along the coast about 100 km away from the Yangtze estuary. SSC increased considerably in both mass and area in 2013. The first principal component analysis (PCA) pattern explained the dominant spatial distribution pattern of SSC in the study area. This highly clustered controlling pattern may have been caused by the joint effects of Yangtze diluted water (YDW), the Taiwan Warm Current (TWC), coastal currents, northeasterly winds, and the shallow coastal shelf. The SSC dispersed and extended into a wide area, and the main range of sediment concentration was located in an area the shape of a trapezium (31.9° N–33.8° N, 122° E–125.5° E, 30.7° N–32.6° N). YDW and the TWC could be the main reason for this northward drift of SSC. The long-term sinking of suspended sediment in clustered areas may have contributed considerably to the formation of the shallow coastal shelf above the 60 m isobath.

Seasonal co-occurrence of sea turtles, bottlenose dolphins, and commercial gill nets in southern Pamlico and northern Core Sounds, and adjacent coastal waters of North Carolina, USA

We assessed the seasonal co-occurrence of sea turtles and bottlenose dolphins Tursiops truncatus with commercial gill nets in southern Pamlico and northern Core Sounds, and adjacent coastal waters of North Carolina, USA, from 41 aerial surveys conducted from 2004 to 2006. Generalized linear models were used to examine the influence of several variables (month, year, habitat type [coastal and estuarine], sea surface temperature, and visibility conditions) on counts of turtles, dolphins, and gill nets. A total of 86 turtles, 1559 dolphins, and 378 gill nets were observed. Predicted counts of turtles and dolphins were highest concurrent with gill nets in spring and autumn in both habitats. Observed spatial overlap of dolphins and gill nets occurred throughout the estuary from spring to autumn, but was limited mainly to the eastern portion of the estuary in winter; spatial overlap of turtles and gill nets occurred predominantly in the eastern portion of the estuary in spring and autumn, and throughout the estuary in summer. During all seasons, dolphins (57 to 75%) and gill nets (80 to 88%) were predominantly observed in shallow (<2 m) waters of the estuary; turtles (75%) were seen most often in shallow estuarine waters in spring. Along the coast, observed spatial overlap of turtles and dolphins with gill nets occurred most often in the region extending from Cape Hatteras south to Ocracoke. These findings improve our knowledge of habitat use by these species, and may also help manage interactions.