Aglaura Hemistoma Research Articles

Assemblages of planktonic cnidarians in winter and their relationship to environmental conditions in the NW Mediterranean Sea

In the present study, we addressed the spatial characterization and species assemblages of the planktonic cnidarian community (Siphonophorae, Hydromedusae, and Scyphomedusae) in winter, a period that has been the subject of few studies in the NW Mediterranean. Data were obtained on two oceanographic cruises, in February 2017 and 2018. In 2017, the early onset of spring conditions and the subsequent phytoplankton bloom favored a mixture of winter and spring species, resulting in a higher species richness but a lower abundance of cnidarians. However, the typical winter oceanographic conditions in 2018 allowed winter species populations to develop, leading to a higher abundance of cnidarians that year. The most abundant species in both winters were Lensia subtilis, Muggiaea kochii, Chelophyes appendiculata, Abylopsis tetragona (eudoxid), Aglaura hemistoma, and Velella velella rataria larvae, while Obelia spp. was particularly numerous in 2017. In both years, the cluster and redundancy analyses showed a coastal-offshore ordination in species assemblages resulting from the effect of environmental variables (particularly bathymetry) and oceanographic structures (water masses and the shelf-slope density front). The presence of submarine canyons, in which great depths are reached close to the coast, modified the circulation patterns, resulting in a mixture of coastal and offshore species in these areas. In the current scenario of global warming, our results will help to provide a baseline for identifying future changes in the structure of the planktonic cnidarian community.

Biodiversity and frequency of occurrence of jellyfish (cnidaria) in Al Hoceima Bay (North coast of Morocco, Alboran Sea)

Jellyfish are the best-known group of gelatinous zooplankton; they refer to organisms from the phylum Cnidaria, including animals with cnidocytes (stinging cells). As part of our research on jellyfish that swarm in the bay of Al Hoceima conducted during the period (2021-2022), a study of the diversity of species of jellyfish in the bay has proved to be of paramount importance because of the risks associated with their proliferation, especially in summer periods. The species composition and frequency of occurrence of the jellyfish community in Al Hoceima Bay (The northern coast of Morocco) were studied during two seasons, summer 2021 and winter 2022. Zooplankton sampling was conducted within the epileptic layer (between 0 and 80 m) at 9 stations. A total of 9 species of Hydromedusae and Scyphomedusae were identified in the study area. The populations of Hydromedusae are represented by Trchymedusae (4 species), Anthomedusae (2 species), and Leptomedusae (one species). The Trachymedusa Aglaura hemistoma was widely distributed in the bay, as it was found in six sampling stations, with a frequency of occurrence Fi>66% during the summer period. The Antomedusae Pantachogon militare was inventoried for the first time in the southwestern Mediterranean Sea.The population of Scyphomedusae is represented by two species, Pelagia noctiluca and Rhizostoma Pulmo, both species showed dense aggregations in the Bay during the summer of 2022.

Distribución y ecología de medusas y sifonóforos en tres estaciones de la zona marino costera de la Península de Santa Elena, Ecuador

Con la finalidad de incrementar el conocimiento sobre los cnidarios se estudió la composición, distribución, abundancia y ecología de la comunidad de medusas y sifonóforos durante la época húmeda desde diciembre del 2015 a mayo del 2016 en seis estaciones ubicadas en la zona costera de Ancón, Anconcito y Punta Carnero (Ecuador), a partir de 51 muestras zooplanctónicas colectadas mediante arrastres superficiales y verticales. Se identificaron 22 especies de medusas clasificadas en 5 órdenes, 14 familias y 16 géneros y 14 especies de sifonóforos con 1 orden, 2 subórdenes, 4 familias y 10 géneros. Las especies más abundantes a nivel superficial fueron Aglaura hemistoma en febrero, Liriope tetraphylla en marzo, Obelia sp. y Proboscidactyla ornata en febrero, Nanomia bijuga en abril, Muggiaea atlantica en febrero, Sulculeolaria chuni y Diphyes dispar en marzo, mientras que en la columna de agua (10 metros) fueron Proboscidactyla ornata en febrero, Liriope tetraphylla, Solmundella bitentaculata, Obelia sp., Muggiaea atlantica y Nanomia bijuga en abril, la máxima diversidad en medusas fue de 2.14 bits/ind en la columna de agua para abril, mientras que en sifonóforos a nivel superficial con 1.67 bits/ind para diciembre. La similitud de Bray-Curtis determinó a las estaciones E2, E3 y E4 como las más afines por sus máximas abundancias. El análisis de correspondencia canónica destacó la relación entre Obelia sp. y Muggiaea atlantica con la temperatura y de Liriope tetraphylla con la salinidad. En general, la fauna de medusas y sifonóforos mostró una representativa afinidad ecológica para aguas tropicales y subtropicales así como también presencia de especies cosmopolitas, neríticas y oceánicas, estudio de vital importancia para asociarlos en futuras investigaciones al Evento El Niño.

Zooplankton composition and distribution in the Lembeh Strait of North Sulawesi, Indonesia

Based on oceanographic survey data in June 2012 in the Lembeh Strait, the zooplankton ecological characteristics such as species composition, individual abundance, dominant species and distribution were analyzed. The results showed that 183 species (including 4 sp.) had been recognized, most of them belonged to copepoda. Cnidaria followed with 43 species (including 1 sp.) were identified. The average abundance of zooplankton was (150.47±58.91) ind./m3. As to the horizontal distribution, the abundance of the zooplankton was higher in the southern waters than in the northern waters. The dominant species in the study area were Lensia subtiloides, Sagitta enflata, Lucifer intermedius, Oikopleura rufescens, Diphyes chamissoni, Creseis acicula, Subeucalanus subcrassus, Temora discaudata, Aglaura hemistoma, Doliolum denticulatum, Canthocalanus pauper, Oikopleura longicauda and Nanomia bijuga. Zooplankton biodiversity indexes were higher in study area than previous study in the other regions. The findings from this study provide important baseline information for future research and monitoring programs.

Estudios de zooplancton marino en Costa Rica: una revisión y perspectivas a futuro

This review summarizes marine zooplankton research performed in the Costa Rican Pacific and Caribbean coasts and at Isla del Coco National Park. Composition, abundance, biomass, distribution and some ecological features of the zooplankton for each system is discussed. Pacific coastal zooplankton composition has been described in Bahía Salinas and Bahía Culebra. The local oceanography of these bays is heavily influenced by the Papagayo wind jet, which produces seasonal coastal upwelling and most likely drives the seasonal changes in zooplankton abundance and biomass. Copepods and ostracods were the dominant taxonomic groups throughout the year with a strong seasonality, furthermore 53 hydromedusae species has been found, where Liriope tetraphylla (Chamisso & Eysenhardt, 1821), Solmundella bitentaculata (Quoy & Gaimard, 1833) and Aglaura hemistoma (Péron & Lesueur, 1810), were the most abundant species. Zooplankton herbivory rates at Gulf of Nicoya estuary was estimated over 50 % removal of primary production. This is a typical value for tropical productive environments. Copepods numerically dominated zooplankton community from the Gulf of Nicoya. Other dominant taxa includes merozooplanktonic decapod larvae and ichthyoplankton. Biomass is high and there are strong crossshelf gradients in the Gulf. Zooplankton collected in the southern Pacific coast (close to Isla del Caño) is also dominated by copepods, while Bahía Coronado has a mixed zooplankton composition of oceanic and coastal transition waters. In Golfo Dulce, zooplankton is highly diverse and dominated by copepods, appendicularians, and ostracods. About 35 % of daily primary production is consumed by microzooplankton, and zooplankton adapt to anomalous conditions of El Niño-Southern Oscillation (ENSO). Coco´s Island, and other oceanic islands in the Eastern Tropical Pacific are “hot spot” of zooplankton diversity, where > 160 zooplankton species have been reported (predominantly copepods). The biomass is dominated by mesozooplankton, and new species records for the Eastern Tropical Pacific have been found in this insular ecosystem. In the other hand, early works of 1980 carried out at Caribbean coast (Cahuita National Park), show a considerably low zooplankton diversity and abundance while research at the end of the 2000 decade recognized a significant increase in zooplankton diversity, specially fish larvae. Recent zooplankton studies have added six new copepod species and several new records of species from different taxonomic groups such as appendicularians, amphipods, chaetognats, euphausiids, gastropods, and polychaetes. Future work should focus on monthly long-term monitoring programs to investigate the effects of ocean acidification and the trophic dynamics associated with fisheries. Alike, longterm studies are needed to see trends of change in planktonic communities, especially comparing areas under human activity in the coastal zone (tourism, port, urban development) with protected areas as targets for study. An increase of sampling efforts must be done in the relatively understudied Northern Caribbean coast.

Long-term changes in the planktonic cnidarian community in a mesoscale area of the NW Mediterranean

In the present work, possible long-term changes in the planktonic cnidarian community were investigated by analyzing (1) species and community spatial distribution patterns, (2) variations in abundance and (3) changes in species richness during three mesoscale surveys representative of the climatic and anthropogenic changes that have occurred during the last three decades (years: 1983, 2004 and 2011) in the NW Mediterranean. These surveys were conducted during the summer (June) along the Catalan coast. All surveys covered the same area, used the same sampling methodology, and taxonomic identification was conducted by the same team of experts. An increase in the abundance of total cnidaria was found from 1983 to 2011. The siphonophore Muggiaea atlantica and the hydromedusa Aglaura hemistoma were the most abundant species, while Muggiaea kochii presented the largest abundance increment over time. Temperature was the main environmental parameter driving significant differences in the cnidarian community composition, abundance and spatial distribution patterns among the surveys. Our results suggest that in the current climate change scenario, warm-water species abundances will be positively favored, and the community will suffer changes in their latitudinal distribution patterns. We consider it extremely important to study and monitor gelatinous zooplankton in mesoscale spatial areas to understand not only long-term changes in abundances but also changes in their spatial distributions since spatial changes are sensitive indicators of climate change.

High spatial heterogeneity of two planktonic cnidarian species related to the variability of a shelf-slope front at short time scales

We investigated the variability in the mesoscale distribution of the siphonophore Muggiaea atlantica and the hydromedusa Aglaura hemistoma in relation to the rapid spatial oscillations of the shelf-slope front off the Catalan coast (NW Mediterranean). Three extensive surveys were carried out in spring at ten-day intervals. High variability in the position of the front resulted from the advection of low-salinity waters originating in the Gulf of Lions, mainly from the Rhône River runoff. High spatial variability in the distribution of the two species was closely related to the shifting positions of the front. Both species occurred on its inshore side in much higher abundances than on its offshore side, where they were scarce or absent. The front acts as a barrier limiting offshore displacement of these two cnidarians. Statistical analyses showed that bottom depth and salinity, as independent variables, were indicators of the signature and position of the front, explaining most of the variance in the distribution and abundance of the two species.

Segregated Distribution of <i>Liriope tetraphylla</i>, <i>Aglaura hemistoma</i> and <i>Nausithoe punctata</i> (Cnidaria) in the Southern Gulf of Mexico

In order to study the segregated distribution of the three most abundant jellyfish species in the southern Gulf of Mexico, a total of 85 stations were sampled during an oceanographic cruise from 19 May to 18 June 2006. Trawling took place from surface to a maximum depth of 200 m, using a Bongo net with a 61 cm mouth diameter and 333 and 500 μm mesh sizes. Temperature and salinity were recorded. Samples were preserved in 4% formalin, neutralized with sodium borate, and changed to 70% ethylic alcohol after 24 hours for conservation. The jellyfish data were standardized to 100 m3 of filtered water. A total of 10,610 jellyfish were collected from the 333 μm mesh size net, of which eight species represented 88.49% of the total density: Aglaura hemistoma, Liriope tetraphylla, Nausithoe punctata, Clytia hemisphaerica, Persa incolorata, Obelia spp., Clytia folleata and Eutima gracilis. The former three species are the subject of this study. The results obtained indicate that the high density areas of these three species have a segregated distribution. Segregation values (White’s index) recorded between pairs of specie were very high: L. tetraphylla - A. hemistoma, 0.88; L. tetraphylla - N. punctata, 0.86 and A. hemistoma - N. punctata, 0.84. The spatial distribution of the high density areas of these species fits well with the three hydrodynamically different areas: A. hemistoma in Campeche Bank, L. tetraphylla on the Campeche and Tabasco shelves and N. punctata in Campeche Bay. This spatial distribution pattern corresponds to their main habitat and reproductive habits of the species, as well as the influence of the hydrodynamics that dominate each area.

Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight).

The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45’S; 47°33’W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1°C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70 m); warm (>20°C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3–0.6 mg m-3). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the “hunger-satiation hypothesis”, maximizing feeding and minimizing the chances of being predated.

Jellyfish assemblages are related to interplay waters in the southern east China Sea

Zooplankton communities are affected by spatial and temporal factors, as well as by general weather conditions, monsoons, and ocean currents. Present study examined the effects of typhoons, monsoons, and interplay waters on jellyfish assemblages in the complex hydrosystem in the coastal areas of the southern East China Sea. The species and composition of jellyfish and their seasonal succession in the coastal areas of northern Taiwan were investigated through 6 research cruises between October 2007 and January 2009. Among the samples obtained during these cruises, 23 jellyfish species from 2 classes, 7 orders, 13 families, and 19 genera were identified. The 3 most abundant jellyfish species were Nausithoe punctata (relative abundance, RA: 91.72%), Aglaura hemistoma (RA: 4.20%), and Diphyes chamissonis (RA: 1.13%). The species A. hemistoma exhibited the highest occurrence ratio (OR, 52.78%), and only this species was observed during all 6 research cruises. The abundance of Corymorpha bigelowi and Lensia multicristata correlated significantly and positively with seawater temperature, indicating that these species are brought to northeastern Taiwan by the warm Kuroshio Current. The formation of an N. punctata bloom yielded a density of 543.25 individuals/m−3 in October 2008, indicating that the jellyfish assemblage was influenced by a typhoon event and exhibited a clear pattern of seasonal succession. However, the interplay waters of the China Coastal Current and Kuroshio Current had a greater influence in shaping the jellyfish assemblage structure than did either typhoons or monsoons.

北部湾北部生态系统结构与功能研究IV：水母动物群集结构与数量分布

PDF HTML阅读 XML下载 导出引用 引用提醒 北部湾北部水母类群集结构与数量分布 DOI: 10.5846/stxb201307011812 作者: 作者单位: 厦门大学海洋与地球学院,厦门大学海洋与地球学院,厦门大学海洋与地球学院,厦门大学海洋与地球学院 作者简介: 通讯作者: 中图分类号: 基金项目: 我国近海海洋综合调查与评价专项(908-01-ST09);海洋公益项目"东南沿海半封闭海湾生态系统对人类活动干扰的响应评价、生态重构技术及示范"(201005012);国家自然科学基金(41006078) The assemblage and abundance distribution of jellyfish in northern Beibu Gulf Author: Affiliation: College of Ocean and Earth Science,Xiamen University,College of Ocean and Earth Science,Xiamen University,College of Ocean and Earth Science,Xiamen University,College of Ocean and Earth Science,Xiamen University 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:根据"908"专项北部湾2006-2007年四个季节的调查数据,分析了北部湾北部(20°N以北海域)水母类的种类组成、数量分布、优势种和群集结构特征及其环境影响因子。该区共记录水母类4类125种,分别为水螅水母类99种、管水母类17种、钵水母类4种和栉水母5种;以沿岸暖水种为主,占本区水母总种数的61.6%,其次是大洋暖水种,占37.6%,沿岸暖温种仅占0.8%。种数季节变化呈单峰型,夏季83种,冬季56种,秋季和春季各49种,四季均以水螅水母类为主。周年丰度变化呈单峰型,夏季(943.0 个/m3)> 春季(572.4 个/m3)> 冬季(548.2 个/m3)> 秋季(427.6 个/m3)。拟细浅室水母、双生水母、球型侧腕水母、四叶小舌水母、半口壮丽水母、两手筐水母、异摇篮水母、双小水母、单囊美螅水母、疣真囊水母、半球美螅水母、六幅和平水母、八囊摇篮水母、刺胞真囊水母、黑球真唇水母、端粗范式水母和细颈和平水母共17种全年出现,为四季种;其中,前7种为四季优势种,优势度(Y)分别为0.25、0.19、0.09、0.08、0.05、0.03和0.03,各季节的优势种演替模式不尽相同。依据水母种类和数量分布情况,北部湾北部水母类可划分2个群集:栖息在受沿岸流影响的20 m以浅的低盐群集,代表种有拟细浅室水母和双生水母等;栖息在受外海水影响的20 m以深的高盐群集,代表种有四叶小舌水母、半口壮丽水母和两手筐水母等。海流与水团的消长是影响水母类群集结构和水平分布格局的重要影响因素。 Abstract:The assemblage structure and abundance distribution of jellyfish were studied based on the samples of Beibu Gulf during 4 seasons in 2006-2007. The environmental factors that probably affected the number of species, abundance and assemblage structure were analyzed. The study showed that a total of 125 jellyfish species were identified, which belongs to 4 assembleges, they were Hydromedusae, Siphonophora, Scyphomedusae and Ctenophore. Hydromedusae was the dominant assemblege, accounted for 79.2% of the total species. The species number of jellyfish varied seasonally, there was 83 in summer, which was the highest among 4 seasons, followed by winter, autumn and spring, the species number were 56, 49 and 49. The 20 meters deep of water could be considered as the boundary according to the horizontal distribution of jellyfish species, the species number of the above was more than the under. There were three ecological groups of the jellyfish, the neritic warm-water group such as Lensia subtiloides, Diphyes chamissonis and Pleurobrachia globosa was the dominant group, accounted for 61.6% of total species, followed by the high-temperature oceanic group, occupied 37.6%, Liriope tetraphylla, Aglaura hemistoma and Solmundella bitentaculata were belonged to this group, and there was only one neritic low-temperature specie identified, that was Ocyropsis crystallina. The abundance of jellyfish varied seasonally, was highest in summer, followed by spring, winter and autumn. The abundance in the northwest of the studied area was higher, and the northern of Weizhou Island was lower, basiclly less than 10.0 ind/m3. There were 17 seasonal species which appeared the whole year, 7 of them were dominant species, Lensia subtiloides, Diphyes chamissonis, Pleurobrachia globosa and Liriope tetraphylla were the most important. Lensia subtiloides got the largest abundance in summer, made contributions to 40.4% of the sum. Diphyes chamissonis' abundance was large in spring and winter, occounted for 36.3% and 32.6% of the sum in each season. The abundance of Liriope tetraphylla in autumn occupied 36.7% of the sum, was far more than the other three seasons. Pleurobrachia globosa' abundance in 4 seasons changed not much compared to the 3 mentioned species, was largest in summer, occupied 12.2% of the sum. The assemblage of jellyfish in northern Beibu Gulf was analyzed based on the effect of 10 factors, they were deeper (D, m), surface temperature (Ts,℃), middle temperature (Tm, ℃), bottom temperature (Tb, ℃), surface salinity (Ss), middle salinity (Sm), bottom salinity (Sb), surface chlorophll a (Chas, mg/m3), middle chlorophll a (Cham, mg/m3) and bottom chlorophll a (Chab, mg/m3). Though the results showed details difference in 4 seasons, it could be divided into two groups, the low-salinity group (lower than 20 m) and high-salinity group (deeper than 20 m) formed northern Beibu Gulf jellyfish assemblage structure. The low-salinity group was mainly affected by the coastal current from Guangxi to Vietnam, this group had two types depended on temperature, they were the neritic low-temperature type and the neritic warm-water type. The high-salinity group was mainly affected by the seawater. The environmental factors varied during four seasons. Currents and water masses were the main factors on jellyfish assemblage and abundance distribution. 参考文献 相似文献 引证文献

Distribution of planktonic cnidarian assemblages in the southern Gulf of Mexico, during autumn

BackgroundDespite their ecological, economic and medical relevance, very little information is available on the distribution of planktonic cnidarians, this being particularly true for some regions of the ocean such as the Gulf of Mexico. In fact, the effect of locally important oceanographic features such as the offshore autumnal transport on the distribution of planktonic cnidarians has long been overlooked in this region. Because of this, the present study aimed to analyse the spatial patterns of planktonic cnidarian assemblages in the southern Gulf of Mexico during the autumn of 1998, when particularly intense conditions of convergence, offshore water transportation and productivity were recorded. The assemblages were described in terms of their composition, abundance (volume), diversity, dominance and equitability. Cluster (Bray-Curtis index) and ordination (multidimensional scaling (MDS)) analysis were performed in order to link the observed distribution of species with the environmental parameters.ResultsSixty-eight taxa were recorded, with Koellikerina fasciculata and Muggiaea atlantica representing new records for the region. The holoplanktonic species Diphyes dispar, Abylopsis spp., Liriope tetraphylla, Diphyes bojani, Aglaura hemistoma, Muggiaea kochi, Chelophyes appendiculata and Eudoxoides mitra were dominant with respect to abundance (ml/1000 m3) and frequency of occurrence and defined the differences among the groups of stations. Four groups of sampling stations were identified: (A) the mouth of the Grijalva-Usumacinta system, (B) the Campeche Bank, (C) the area of offshore oil rigs and (D) the continental shelf off Tabasco and associated oceanic waters. The parameters that defined the groups of stations were zooplankton volume, sampling station depth, salinity and dissolved oxygen concentration.ConclusionsPlanktonic cnidarians are useful as indicators of water masses, since the observed zonation was congruent with the surface circulation patterns that are present during the autumn (offshore transportation) and the presence of particular local environmental conditions, including those at the mouth of the Grijalva-Usumacinta system and those associated with the area of oil rigs. We would expect that similar conditions of strong offshore transport would lead to a similar horizontal stratification in the assemblages of planktonic cnidarians in other parts of the world, driven mainly by salinity, oxygen, depth and zooplankton gradients.

Distribution of planktonic cnidarians in response to South Atlantic Central Water intrusion in the South Brazilian Bight

Five oceanographic cruises were made between November 2005 and June 2006, sampling a cross-shelf transect off the South Brazilian Bight (SBB; 26°46′S) to follow the seasonal development of the South Atlantic Central Water (SACW) intrusion over the shelf and its influence on the assemblage of planktonic cnidarians. An onshore wind-driven bottom intrusion of the SACW was clearly perceptible, reaching the coast in January. From March onward, the SACW influence was gradually displaced seaward due to wind and tidal mixing. By late June the SACW influence was offshore and the inshore was dominated by low-salinity waters (<34.5). The abundance, distribution, and general taxonomic composition of both medusae and siphonophores were strongly influenced by the onshore intrusion of the SACW. An inshore–offshore gradient was clear. The Canonical Correspondence Analysis suggested that coastal species – dominated by Liriope tetraphylla, actinula larvae and Muggiaea kochi – were mostly related to food availability and a vertically mixed environment inshore, and their abundance and extent were reduced during intrusion periods. In contrast, species with offshore affinities tended to increase their abundance and distribution during intrusion periods, and were mostly related to the presence of thermal stratification and a deep chlorophyll maximum layer. Most of these offshore species, such as Aglaura hemistoma, Rhopalonema velatum and many calycophorans, are associated with the warm upper layer. However, high concentrations of large (>20mm in diameter) Solmaris corona were observed exclusively in cold waters, suggesting this medusa is a SACW indicator.

Jellyfish diversity and distribution patterns in the tropical Southwestern Atlantic

Jellyfish are often the most prominent components of plankton, with severe consequences for fisheries and tourism. However, in tropical regions, there is much uncertainty about these consequences due to the lack of basic data. Our objective was to improve the knowledge about jellyfish in the Western Atlantic, with an emphasis on understanding diversity, abundance, and distribution patterns. Samples were collected at 34 stations in 1995 using a 300-μm-mesh Bongo net. The 21 species identified belonged to Hydromedusae (11), Siphonophora (nine), and Scyphomedusae (one). The overall mean density was low (5.2 ± 5.3 ind. m−3). Total Hydromedusae biomass was 130.86 mg C m−3, and total Siphonophora biomass was 19.04 mg C m−3. Chelophyes appendiculata (Eschscholtz, 1829) was the most frequent species captured in the oceanic samples, and Aglaura hemistoma (Péron & Lesueur, 1810) was the most common in the neritic region. The latter species is sometimes characterized as a bloom associated with the most polluted and eutrophic river plumes. The main role of jellyfish species in the area is as a higher-order carnivore. A cross-shelf significant difference (P < 0.05) was registered, with higher species numbers in oceanic regions and higher densities and biomass in neritic regions.

Faunistic survey of Hydromedusae (Cnidaria, Medusozoa) from the coast of Paraná State, Southern Brazil.

This study is the first faunistic inventory of hydromedusae from the inner continental shelf of Paraná State. We describe the composition of hydromedusae species, collected with bottom-trawl and Hensen nets, in campaigns carried out from 1997 to 2006. We analyzed 17,797 specimens from 578 samples, and provide descriptions, photographs, and information about the biology of the 22 species found. All species had previous records from the Brazilian coast; however, this is the first record of Bougainvillia frondosa, Ectopleura dumortieri, Cirrholovenia tetranema, Eucheilota maculata, Gossea brachymera, Solmaris corona, and Amphogona apsteini for the coast of Paraná. Most species are typical of tropical and subtropical coastal waters from the South Brazilian Bight. However, Turritopsis nutricula, Niobia dendrotentaculata, Solmaris corona, and Aglaura hemistoma are abundant in oceanic waters, and Olindias sambaquiensis and Solmaris corona are associated with colder waters (&lt;20°C). The current number of species known for the state is 26. Additional collection effort is needed in regions not sampled in this work, such as bays and offshore waters.

Short-term temporal variation in gelatinous zooplankton populations over 48 hours in a coral reef at Redang Island, Malaysia

Gelatinous zooplankton abundance and species composition were investigated at 3-h intervals for a 48-h period at a fringing reef in Malaysia. A total of 20 gelatinous zooplankton species were observed; the community was dominated by the calycophoran siphonophore Diphyes chamissonis (79.9%), followed by the trachymedusdae Aglaura hemistoma (5.6%) and Liriope tetraphylla (4.8%). The gelatinous zooplankton were not collected in the water column during most of the daytime hours (1200, 1500 and 1800 h) but were common during the night. However, an abrupt peak in abundance was found at 0900 h on the second day. The times of appearance at night were different depending on the species, and the number of species was also different depending on the hour of sampling. Sampling at 3-h intervals over a 48-h period revealed that the temporal variation (or sampling availability) was large in this study. Careful consideration should be given to the sampling variability in handling the gelatinous zooplankton samples in coral reef areas.

Medusas (Cnidaria: Hydrozoa) de una zona de afloramiento costero, Bahía Culebra, Pacífico, Costa Rica

The hydromedusae have an important role in marine trophic webs due to their predatory feeding habits. This is the first study of this group of gelatinous marine zooplankton in a coastal upwelling area of Central America. The composition and abundance variability of hydromedusae were studied during six months in 1999 at four stations in Culebra Bay, Gulf of Papagayo, Pacific coast of Costa Rica (10 degrees 37' N-85 degrees 40' W). A total of 53 species were identified, of which 26 are new records for Costa Rica, 21 are new records for Central America, and eight are new records for the Eastern Tropical Pacific. The more abundant species (more than 30% of the total abundance) were Liriope tetraphylla, Solmundella bitentaculata and Aglaura hemistoma. Six species occurred throughout the sampling period, 10 were present only during the dry season (December-April), and 17 were so during the rainy season (May-November). Significant differences of medusan abundances were found between seasons (dry vs. rainy). Maximum abundance (2.1 +/- 4.3ind./m3) was recorded when upwelled deeper water influenced the Bay, as indicated by local higher oxygen concentrations and lower water temperatures. The relatively high species richness of medusae found in Culebra Bay is probably related to factors like the pristine condition of the Bay, the arrival of oceanic species transported by the Equatorial Counter Current (ECC), the eastward shoaling of the Costa Rica Dome, and local currents. Illustrations of the 15 more important species are included to facilitate their identification and foster future work in the region.

New contributions to the jellyfish fauna of the Marmara Sea

This manuscript deals with the first records of five jellyfish species in the Marmara Sea (Turkey) of previously unrecorded medusozoan species (four hydrozoan taxa, Liriope tetraphylla, Aglaura hemistoma, Solmundella bitentaculata, Neoturris pileata, and one scyphozoan, Paraphyllina ransoni) from plankton collections made in the years 2001–2008. Jellyfish abundances and distribution patterns are reported here, with a discussion about their possible introduction pathways and potential predatory outcomes into the fragile pelagic ecosystem of the Marmara Sea.

Diel vertical migration of medusae in the open Southern Adriatic Sea over a short time period (July 2003)

AbstractDiel vertical migration (DVM) of medusae was investigated at a fixed station in the oligotrophic Southern Adriatic Sea at several depths during summer (July) 2003. We hypothesized that medusan DVM is considerably influenced by environmental variables such as hydrographic features, light intensities, and potential prey densities. We used short‐term repetitive sampling as an approach to detail these relationships. Of the 26 species collected, the highest abundance was in the layer between the thermocline (15 m) and 100 m depth, where Rhopalonema velatum predominated, reaching the maximum count of 93 individuals per 10 m3. Seven species were observed over a wide depth range: Solmissus albescens (15–1200 m), R. velatum (0–800 m), Persa incolorata (50–1200 m), Octophialucium funerarium (200–1200 m), Arctapodema australis (200–1200 m), Amphinema rubra (100–800 m), and Rhabdoon singulare (15–600). According to the medusan weighted mean depth (WMD) calculations, the longest DVMs were noted for the deep‐sea species S. albescens, O. funerarium, and A. australis. The shallowest species, Aglaura hemistoma, was primarily non‐migratory. Certain medusan assemblages were associated consistently with a particular depth layer characterized by a particular light intensity. The interplay of environmental factors and trophic relationships explains some of the features of medusan migratory patterns. These findings thus contribute to understanding the variables that determine patterns of medusan vertical migratory behavior.

Distribution of the mesozooplankton at continental shelf off Sergipe, Brazil

The purpose of this work was to study the composition and abundance of the mesozooplankton at two stations at the continental shelf off Sergipe. At each station, oblique plankton tows were carried using plankton nets with 200 µm mesh size, in six hours intervals during three consecutive days. One hundred and three taxa were identified and Copepoda was the dominant group with fifty one species. The mesozooplankton assemblage was composed by coastal, neritic and oceanic tropical species. There were significant differences in composition and abundance between the two studied stations (p&lt;0,05) but not between tidal stages. At station 1, the most abundant species were Creseis acicula, Oikopleura spp., Temora stylifera, Paracalanus quasimodo and Aglaura hemistoma, and at station 2 Paracalanus quasimodo, Paracalanus spp., Siphonophora, Gastropoda and Decapoda larvae. Coastal species such as Parvocalanus crassirostris, Acartia lilljeborgi, Euterpina acutifrons and Corycaeus giesbrechti occurred only at the last station, located close to the mouth of the São Francisco River, where surface salinity and transparency values were low. In this station the salinity average value at surface was 30,8±1,9 and at the bottom layer was 35.0±0.3 PSU. Mesozooplanhton density values ranged between 124 ind.m-3 and 2,658 ind.m-3 at station 1, and from 734 ind.m-3 to 3,061 ind.m-3 at station 2. A Monte Carlo test based on a canonical ordination revelead that local depth and water transparency were significantly correlated to the mesozooplankton distribution. Key words: zooplankton community, Copepoda, shelf off Sergipe, tropical.