Marine artificial structures as amplifiers of Aurelia aurita s.l. blooms: a case study of a newly installed floating pier

Increase of marine artificial structures, providing more substrate for jellyfish polyps, has been argued to increase jellyfish outbreaks, although no explicit evidence exists. We report a case study demonstrating a remarkable increase of Aurelia aurita s.l. ephyrae after the installation of a floating pier (48 × 6 m) in a fishing port on the Inland Sea of Japan. Monitoring of ephyrae from January 2010, prior to the installation of the floating pier in April 2010, to July 2011, revealed that their time-weighted average density increased 3.5 fold, from 1.1 to 3.9 ephyrae m^?3, and the integrated number of ephyrae exported from the port increased 4.3 fold, from 5.7 × 10⁶ to 25 × 10⁶ ephyrae, after the installation. However, in a nearby port, a control site, the abundance of ephyrae decreased by ca. one third during the same period. Monitoring of polyps showed that they initially colonized the undersurface of the pier by August 2010, followed by a rapid population increase. They strobilated from December 2010 to May 2011. We computed the number of ephyrae released from the strobilae to be ca. 25 × 10⁶, very close to the net increase of ephyrae produced and exported from the port. This study corroborates that the installation of an artificial structure provides new a substrate for polyps, which allows them to produce more ephyrae to induce medusa blooms.     

基于高通量测序技术的两种水螅水母现场食物研究

水母类在自然海区的食物组成是摄食生态学研究的核心问题,本研究利用高通量测序技术分析了管花萨氏水母(Sarsia tubulosa)和八斑芮氏水母(Rathkea octopunctata)的现场食物组成。结果表明:管花萨氏水母和八斑芮氏水母现场摄食食物具有较高的多样性,管花萨氏水母摄食食物31种,八斑芮氏水母29种;两种水母从食物组成上看,属于杂食性生物,其食物包括浮游动物、真菌、浮游植物、陆地植物碎屑等;管花萨氏水母和八斑芮氏水母二者互为捕食对象;二者摄食的食物类群具有相似性,主要来源于节肢动物门和颚足纲,均以太平真宽水蚤为摄食优势种,分别贡献两者食物总量的45.14%和42.42%。高通量测序技术是深入探究水母现场食物组成新的技术手段,两种水母的现场食物组成结果为水母摄食生态学的研究提供了重要参考。     

Clearance rates of ephyrae and small medusae of the common jellyfish Aurelia aurita offered different types of prey

Prey selection and knowledge of the amounts of water processed by the early stages of the common jellyfish Aurelia aurita may at certain times of the year be crucial for understanding the plankton dynamics in marine ecosystems with mass occurrences of this jellyfish. In the present study we used two different methods (“clearance method” and “ingestion-rate method”) to estimate the amount of water cleared per unit of time of different types and sizes of prey organisms offered to A. aurita ephyrae and small medusae. The mean clearance rates of medusae, estimated with Artemia sp. nauplii as prey by both methods, agreed well, namely 3.8 ± 1.4 l h^? 1 by the clearance method and 3.2 ± 1.1 l h^? 1 by the ingestion-rate method. Both methods showed that copepods (nauplii and adults) and mussel veligers are captured with considerably lower efficiency, 22 to 37% and 14 to 30%, respectively, than Artemia salina nauplii. By contrast, the water processing rates of ephyrae measured by the clearance method with A. salina nauplii as prey were 3 to 5 times lower than those measured by the ingestion-rate method. This indicates that the prerequisite of full mixing for using the clearance method may not have been fulfilled in the ephyrae experiments. The study demonstrates that the predation impact of the young stages of A. aurita is strongly dependent on its developmental stage (ephyra versus medusa), and the types and sizes of prey organisms. The estimated prey-digestion time of 1.3 h in a steady-state feeding experiment with constant prey concentration supports the reliability of the ingestion-rate method, which eliminates the negative “container effects” of the clearance method, and it seems to be useful in future jellyfish studies, especially on small species/younger stages in which both type and number of prey can be easily and precisely assessed.     

海月水母与海蜇不同幼体阶段的种间短期竞争研究

近年来海蜇池塘养殖业的兴起,补充了传统海蜇渔业捕捞生产的不足,推动了海蜇产业的迅猛发展。海月水母常常在海蜇养殖池塘中泛滥成灾,对海蜇养殖业常常造成很大损失,但关于海蜇与海月水母的种间竞争关系尚缺乏研究。本文对海月水母与海蜇的螅状体、碟状体及水母体幼体相互之间的短期生存竞争关系进行了初步观察研究。结果表明:除海月水母碟状体可以被海蜇螅状体所捕食外,各种类型的海蜇幼体基本不能对海月水母幼体造成危害。但海月水母螅状体及其水母体幼体对海蜇幼体均存在一定的危害性,尤其是对海蜇碟状体的危害性最为严重,在饵料缺乏的情况下海蜇碟状体可以100%地被捕食。随着海蜇幼体的生长,其对于海月水母危害的抵抗力逐渐增强。本研究显示海月水母相对于海蜇而言,在幼体种间竞争关系中处于绝对优势,这是海月水母时常暴发成灾的一个重要因素。在海蜇池塘养殖生产及苗种培育过程中,应当严禁混入海月水母幼体,以避免对海蜇养殖生产造成损害。     

Planktonic ciliates as food for the scyphozoan <Emphasis Type="Italic">Aurelia coerulea</Emphasis>: feeding and growth responses of ephyra and metephyra stages

Blooms of the moon jellyfish, Aurelia coerulea, often occur in eutrophic embayments where microzooplankton are abundant. Hence, microzooplankton may play a role in A. coerulea population dynamics. In this study, feeding and growth responses of the ephyra and metephyra stages of A. coerulea were examined on a diet of planktonic ciliates, the main components of microzooplankton. Laboratory experiments indicated that ephyrae actively fed on ciliates and that the central disc diameter increased over the 5-day incubation period. Carbon-specific growth rates estimated from daily increases of central disc diameter increased with carbon-specific prey consumption rates until about 4 µg C ind day^?1 and then became saturated. By fitting these results to rectangular hyperbolic equations, the maximum specific growth rates were estimated to be 0.32 day^?1 for ciliate prey. However, the central disc diameter of the metephyrae did not increase on a diet of ciliates during the 5-day incubation, even though consumption of prey ciliates was observed. These results suggest that planktonic ciliates serve as a food source for growth at the ephyra stage of A. coerulea and then the contribution to growth decreases at and after the metephyra stage. This prey switch-dependency on the development stage of A. coerulea may be associated with the frequent occurrence of jellyfish blooms in eutrophic embayments.     

Diet of sardine Sardinops sagax in the southern Benguela upwelling ecosystem

The diet of sardine Sardinops sagax in the southern Benguela was investigated by microscopic examination of stomach contents. The relative dietary importance of prey size and prey type was assessed by calculating the carbon content of prey items. Sardine is an omnivorous clupeoid, ingesting both phytoplankton and zooplankton, with the relative importance of these two food types varying both spatially and temporally. Stomach contents were numerically dominated by small prey items, principally dinoflagellates, followed by crustacean eggs, cyclopoid copepods, calanoid copepods and diatoms. Virtually all prey items ingested by sardine were <1.2 mm maximum dimension, the particle size below which sardine only filter-feed. Despite the numerical dominance by phytoplankton, zooplankton contributed the major portion to sardine dietary carbon, small calanoid and cyclopoid copepods, anchovy eggs and crustacean eggs being the primary prey types. These results indicate that, like anchovy Engraulis capensis, sardine in the southern Benguela are primarily zoophagous, and contrast with earlier dietary studies on sardine in the region. However, the two species appear to partition their prey on the basis of size; sardine consume small zooplankton, whereas anchovy consume large zooplankton. This difference has been observed in other upwelling ecosystems where the two genera co-exist and is likely to contribute to the regime shifts observed between sardine and anchovy.     

On the Polyps of the Common Jellyfish Aurelia aurita in Kagoshima Bay

There is the natural habitat of polyps of the common jellyfish Aurelia aurita in the Taniyama area, Kagoshima Bay. We examined the attachment substrata, density, colony structure and strobilation of the polyps. The polyps were observed only on the horizontal undersurface of floating piers. They attached specifically to Mytilus shells, solitary ascidians, calcareous polychaete tubes, muddy amphipod tubes and the gap space that fouling animals peeled off the substrata. The polyp colonies were distributed in patches. Spatial distribution patterns of the polyps within their colonies were uniform. Strobilation occurred during late December to March, when water temperatures were 16–17°C, and a large number of ephyrae were released. An increase in man-made structures such as floating piers in coastal areas may lead to bloomings of Aurelia aurita medusae. This revised version was published online in July 2006 with corrections to the Cover Date.     

大亚湾核电站邻近水域桡足幼体现场摄食研究

桡足类种类多、数量大、分布广, 在食物链中处于中间环节, 对海洋生态系统的结构稳定起着重要作用。桡足类幼体获取的营养直接影响其发育, 进而影响桡足类成体补充乃至种群的稳定。本研究于2015年夏季分别在大亚湾核电站邻近海域S1 (进水口水域)和S2 (排水口水域)站进行了调查采样, 应用分子生物学方法检测了桡足幼体现场摄食食物组成。结果显示: 1)两个站的桡足幼体内共检测到16种不同食物, 包括浮游植物(硅藻)11种, 后生动物2种、真菌、Ichthyosporea 和卵菌类各1种共5大类, 其中硅藻(47.30%, 克隆数百分比, 下同)和被囊动物类后生动物(41.89%)是其主要的食物类群; 2)在S1和S2站桡足幼体内分别检测到9种和10种食物, 但主要食物类型有差异, S1站较多后生动物(61.54%), 而S2站较多硅藻(68.57%); 3) S2站的桡足幼体杂食偏植食程度更高, 其杂食性系数(0.31)低于S1站(0.72)。结果表明, 桡足幼体能根据食物环境有选择地摄食植物饵料和动物饵料, 调节食物营养结构; 温排水影响水域桡足幼体更偏向植食性, 尤其是硅藻, 暗示全球变暖可能导致桡足幼体食性偏移。     

Use of the Aurelia Metamorphosis Test System to detect subtle effects of selected hydrocarbons and petroleum oil

The Aurelia Metamorphosis Test System was devised to use simple Aurelia polyps as indicator organisms for the detection of subtle effects of petroleum-related hydrocarbons and of Alaskan crude petroleum oil (ACPO) on developmental processes involved in strobilation initiation, differentiation of ephyrae, and genetic modification expressed through cloning. Compounds tested were ACPO, aniline, anthracene, benzanthracene, benzene, benzo[a]pyrene, biphenyl, cresol, naphthalene, perylene, phenol and pyrene. Gross morphology of the ephyrae (patterning, numbers and appearance of structures), statolith and mematocyst numbers, and pulsing behavior were recorded using the light microscope. Selected ephyrae with teratological malformations were studied with the scanning electron microscope and swimming behavior was observed visually. The variety of subtle developmental, behavioral and genetic effects due to marine hydrocarbons detected using the Aurelia Metamorphosis Test System demonstrated that this test system could be used as an early warning system to detect subtle effects of other marine pollutants.     

The diet of mesopelagic fish from the Pacific coast of Hokkaido,Japan

The diet of at least 28 species of mesopelagic fish from the Pacific coast of Hokkaido was examined. The dominant family was the Gonostomatidae (42%) which was represented by five species. The most abundant species wasCyclothone atraria which together with the other species of this genus preyed predominantly on copepods. Euphausiids and copepods were dominant in the diet ofGonostoma gracile. The next most abundant family was the Myctophidae (32%) which was represented by seven species. The dominant species,Stenobrachius nannochir, preyed mainly on copepods. Copepods were also the dominant food item of the other myctophids except forLampanyctus jordani which fed mainly on euphausiids. The other important family was the Bathylagidae (21%).Leuroglossus schmidti was the dominant species and its diet was more diverse with ostracods, copepods, molluscs and larvaceans being the most important food items.Bathylagus ochotensis had a similar diet. Copepods were the most important food items for all but a few species and their occurrence in the fish stomachs was related to the known vertical distribution of both predators and prey. Ostracods and euphausiids were also important prey items, the latter especially in large fish species. Molluscs and larvaceans were restricted to the two species of the family Bathylagidae.     

Feeding ecology of the deep-water blue–red shrimp Aristeus antennatus (Decapoda: Aristeidae) in the Greek Ionian Sea (E. Mediterranean)

The feeding habits of the deep-sea blue–red shrimp Aristeus antennatus were determined based on the analysis of 1047 stomach contents, sampled in the Greek Ionian Sea (E. Mediterranean). The diet of this economically and biologically important decapod was studied in relation to the season, size class and sex. The diet of A. antennatus consisted of 54 different prey categories, and belonged mainly to smaller crustaceans (e.g. natantian decapods, euphausiids, tanaidaceans), molluscs, polychaetes, chaetognaths and, to a lesser extent, fishes. The above prey categories consisted of 71–82% of the relative abundance and total occurrence for males and 61–81% for females. Females seemed to be better fed than males (stomach fullness, food quality). A. antennatus displayed a highly diversified diet and the different feeding patterns were discussed. Diet composition showed slight seasonal fluctuations. The observed slight differences on A. antennatus diet among the western, central and eastern Mediterranean could be attributed to the more oligotrophic character of the eastern part of the basin. The principal factors driving the changes in the feeding strategy of this decapod among the seasons are the increased energy demands related to sexual requirements and the food availability in the marine environment. The ontogenetic changes in the shrimp's diet were relatively clear. Larger individuals exhibited selecting prey with a good swimming capacity (e.g. fishes), while the smaller individuals consumed prey with low mobility (e.g. copepods, ostracods).     

Feeding Habits of the Mesopelagic Fish Gonostoma gracile in the Northwestern North Pacific

The diet of Gonostoma gracile, a numerically abundant mesopelagic fish in the Subtropical Region and the Transition Domain of the northwestern North Pacific, was examined using 520 specimens collected during June–July 1988, June 1995 and November 1995. The prey included mainly copepods, ostracods, amphipods and euphausiids. Copepods and ostracods were the most abundant, comprising approximately 70% of the total diet. There was little evidence of an ontogenetic dietary shift; Pleuromamma copepods were the most abundant prey for all size classes of fish ranging from 19 to 116 mm in standard length. The size range of prey increased with growth, but all fish sizes examined fed mainly on 1–4 mm long prey. Luminescent copepods and ostracods were the most abundant prey, suggesting that G. gracile detects its prey visually. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dietary separation between co-occurring copepods in a food-limited tropical coral reef of the Sanya Bay

Food differentiation among coexistent species in the field is important strategy for copepods to acquire materials and maintain population stabilization.In situ diet analysis of co-occurring six copepod species in coral waters of the Sanya Bay was conducted using a PCR protocol based on 18 S ribosomal gene.Various prey organisms were uncovered,including dinoflagellate,diatom,green algae and plant,protozoa and metazoan.All these spatially coexisting six species showed different dietary diversity,with the food niche breadth(B)ranging from 1.00(Temora turbinate in morning)to 10.68(Calanopia elliptica in night).While food overlap between all these copepods were low,with the average value of the diet niche overlap index being approximately 0.09.Even temporally co-existing species sampled from the same time point fed on different groups of prey items with the food overlap index of 0.04 to 0.07 in midday and night but 0 in morning.As the most important dominant copepod in the Sanya Bay,Subeucalanus subcrassus seems to be capable to regulate its feeding,by exhibiting a rhythm of herbivorous feeding in midday and carnivorous feeding in morning and night,to better coordinate with other competitors for utilization of food resources.For most copepods,none of the prey items belonged to the dominant phytoplankton in the ambient water,indicating that copepod can better their survival by widening the choice of potential food resources in food limited environment.The dietary separation observed here might be important strategy for copepod to maintain population stabilization and thriving in the Sanya coastal waters.     

宁德市东部海域浮游动物群落及其与水环境因子的关系

浮游动物在海洋生态系统中发挥重要作用,也是海洋食物链的主要环节。为科学保护和评价海洋生态环境和渔业资源,文章基于2016年春、秋季宁德市东部海域的相关调查结果,采用多样性指数、丰富度指数、均匀度指数和优势度指数以及去趋势对应分析法和冗余分析法,分析浮游动物群落及其与温度、pH值、溶解氧、无机氮、无机磷和化学需氧量6个水环境因子的关系。研究结果表明:春、秋季调查共鉴定浮游动物12类67种,季节和站位差异不大,均以水母类、桡足类和浮游幼虫为主;共出现优势种18种,春、秋季分别以桡足类和水母类为主,相同优势种仅有2种;3种指数分布无明显季节差异,但秋季指数总体较高;春、秋季浮游动物种类分别与各水环境因子呈正相关或负相关关系,其中温度是影响浮游动物种类的最主要水环境因子。     

海月水母(Aurelia sp.1)对中肋骨条藻(Skeletonema costatum)和东海原甲藻(Prorocentrum donghaiense)摄食的研究

采用饵料浓度差减法,在实验条件下研究了不同细胞密度的中肋骨条藻和东海原甲藻对海月水母水螅体、碟状体和水母体摄食活动的影响。结果表明,不同种类和密度的微藻细胞密度对水螅体、碟状体和水母体的摄食有显著影响。在实验的藻细胞密度范围内,随藻细胞密度的增加,水螅体和碟状体对中肋骨条藻和东海原甲藻的摄食率一直升高。水螅体对中肋骨条藻和东海原甲藻的最大摄食率均发生在藻细胞密度最高处,分别为4623cells/(ind.h)和4118cells/(ind.h)。碟状体对中肋骨条藻和东海原甲藻的最大摄食率也是发生在藻细胞密度最高处,分别为174671cells/(ind.h)和47218cells/(ind.h)。清滤率随着藻细胞密度增加而降低。在相似细胞密度下,碟状体对中肋骨条藻的摄食率高于东海原甲藻。水螅体和碟状体对同种藻的摄食情况不同,在相似藻细胞密度下,碟状体的摄食率比水螅体高。经过藻类饵料适应处理的水螅体对藻类的摄食率会有显著增加,约为未经饵料适应处理的10倍。水母体对中肋骨条藻和东海原甲藻未发生摄食。     

Genetic Structure and Diversity of the Moon Jellyfish Aurelia coerulea Polyp Population in Jaran Bay,Korea, Revealed by Mitochondrial COI and 16S rRNA Genes

Ocean Science Journal - Blooms of the moon jellyfish (Aurelia coerulea) have been responsible for huge economic losses and environmental disruptions in oceans around the world. The mass occurrence...     

中国近海区域古菌群落结构研究概述

古菌作为海洋微生物的重要组成部分,是海洋生态系统中物质与能量传递的重要贡献者,在全球生物地球化学循环中扮演着不可或缺的角色。虽然目前绝大多数的古菌尚未获得纯培养,但近年来分子生物学技术的发展使人们认识到古菌参与甚至主导了海洋生源要素循环的关键过程。本文介绍了目前研究海洋古菌多样性的主要手段,包括:荧光定量PCR、16S rRNA基因扩增子高通量测序、宏组学以及单细胞测序等技术,系统地阐述了中国近海不同区域(包括辽河口、黄河口、渤海、南北黄海、长江口、东海北部、珠江口以及南海区域)海水及沉积物中的古菌群落结构和多样性特征。研究表明我国近海地区的主要古菌类群为广古菌门(Euryarchaeota)、奇古菌门(Thaumarchaeota)、乌斯古菌门(Woesearchaeota)和深古菌门(Bathyarchaeota)等,其生物地理学分布主要受到环境因子和距离因素的影响,且在河口和近海海域呈现出完全不同的分布特点。在此基础上,对未来的研究方向进行展望,为全面深入了解我国边缘海生态系统中古菌群落及其参与的生物地球化学循环奠定了基础。     

Density Estimates of Moon Jellyfish (Aurelia coerulea) in the Yeongsan Estuary using Nets and Hydroacoustics

Ocean Science Journal - Using nets and acoustic frequencies of 38 and 120 kHz, we estimated the density distribution of the moon jellyfish, Aurelia coerulea, in the Yeongsan Estuary, where a large...     

Coupling bio-logging with nutritional geometry to reveal novel insights into the foraging behaviour of a plunge-diving marine predator

It is widely believed that predators maximise their energy intake while foraging and consume prey that are nutritionally similar. We combined GPS data loggers, miniaturised cameras, dietary sampling and nutritional geometry to examine the nutritional variability in the prey and selected diet, and foraging performance, of the masked booby (Sula dactylatra tasmani), a wild carnivore and marine top predator. Data loggers also revealed no significant differences between sexes in the foraging performance of chick-rearing adults. Females provided more food to their chicks than the males and, regardless of the nutritional variability of prey consumed, both sexes showed similar amounts of protein and lipid in their diets. Miniaturised cameras combined with nutritional analysis of prey provided, for the first time, fine-scale detail of the amounts of macronutrients consumed in each plunge dive and the overall foraging trip. Our methodology could be considered for future studies that aim to contribute to the general understanding of the behavioural and physiological mechanisms and ecological and evolutionary significance of animal foraging (e.g. energy expenditure budgets and prey selection for self- and offspring-feeding that could lead to sex-specific foraging strategies).