Recurrent Red-tides in the Southampton Water Estuary Caused by the Phototrophic CiliateMesodinium rubrum

In the Southampton Water estuary (southern England, U.K.), red-tides caused by the planktonic, phototrophic ciliateMesodinium rubrum(=Myrionecta rubra) occur during most summers and sometimes in autumn. These events were investigated in detail between 1985 and 1987 and were characterized by levels of chlorophylla(chl a) of over 100 μg l⁻¹, cell numbers ofM. rubrumof over 1×10³ ml⁻¹, oxygen saturations of around 150%, and depleted numbers of macrozooplankton. Initiation of red-water did not appear to be triggered by irradiance or nutrients, but coincided with an increase in temperature and water column stability. This enhanced stability was promoted by increased surface to bottom gradients of both temperature and salinity, and by reduced mixing during neap tides. Development of red-water was accompanied by removal of most of the dissolved NH⁺₄from the water column, whereas some NO⁻₃persisted, presumably maintained by freshwater input. NO⁻₃and NH⁺₄gradually returned to pre-bloom concentrations as the red-water declined in late summer. Maximal biomass ofM. rubrumappeared to be limited by irradiance, and self-shading probably imposed an upper limit of around 300 mg chl a m⁻²within the water column. At the observed levels of chl a, irradiance values within the population maximum between 1 and 3 m depth were only just of the order (≈15 μmol photons m⁻² s⁻¹) required to balance estimated respiratory demands. Oxygen concentration became undersaturated during the late bloom phase, with minimal values of 20–30% saturation recorded in deeper waters; however, despite this and reduced numbers of macrozooplankton, direct deleterious effects on other organisms were not observed.     

Multi-bioindicator study of a small estuary in Vendée (France)

Surficial sediment (about 5 mm) was scraped off in 15 stations selected in the Vie Estuary, a small estuary on the French Atlantic coast. The samples, prepared using the suitable methods, were used for comparing the behaviour of periphytic algae, sporopollinic and other palynologic material, ostracoda and foraminifera for proposing a synthetic evaluation of the information provided by each of them. Dinoflagellate cysts, which are found in an almost monospecific assemblage in low-salinity water, are dispersed by tidal currents, but the location of tintinnids in only the lower reaches shows a limited inward transport. Sporopollinic material is clearly related to the adjacent vegetation, indicating a local origin, and then little influence of transport on the microbenthos, even if fragments of freshwater crustaceans and of Pediastrum alga are found down to the mouth in the sporopollinic deposits. This limited transport of microbenthos allows the use of periphytic algae, benthic ostracoda and benthic foraminifera as indicators of local environmental conditions. It was then possible to determine the extent of marine influence in the estuary, to discriminate between the main channel and adjacent basins, and between different stages of evolution of the basins, from a recently dug basin to a eutrophicated one.     

Effects of an Artificial Breakwater on the Distributions of Planktonic Microbial Communities

The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semienclosed, inner area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. 0.4 mg L¹) and high concentrations of inorganic nutrients (nitrogenous nutrients >36 μM, phosphate <4 μM) in the bottom layer. Higher densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed into more than 10⁶ cells L¹ at the surface layer of the inner area, while its abundance was much lower (10³-10⁴ cells L¹) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p < 0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to theT. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates.     

Temporal change of clustered distribution of planktonic ciliates in Toyama Bay in summers of 1989 and 1990

Temporal change of clustered distribution in vertical profiles of three nutritional groups of planktonic ciliates, e.g. heterotrophic naked ciliates, mixotrophic naked ciliates and heterotrophic loricated ciliates, was investigated by following a drifting buoy in Toyama Bay on the Japan Sea coast of central Japan in summers of 1989 and 1990. Clustered distribution, represented as the mode of population density in the vertical plane, occurred mainly in the oligotrophic upper layer (0–50 m depth) above the subsurface chlorophyll-a maximum layer. Its clustered degree was stronger when the mode of population density in the vertical plane was formed at shallower depth, while its longevity was shorter as mentioned above. Vertical distribution of ciliates during summer in Toyama Bay is characterized by ephemeral clustered distribution, or in other wards, by rapid alternations of appearance and disappearance of the clustered distribution.     

Taxonomic Studies on a New Marine Ciliate, Apocoleps magnus gen. nov., spec. nov. （Ciliophora, Colepidae）, Isolated from Qingdao, China

The morphology and infraciliature of a new marine colepid ciliate, Apocoleps magnus gen. nov., spec. nov., are described based on living observations and silver impregnations. The new genus Apocoleps is characterized by having 8 (vs. 6 in most other related genera) armour tiers, spines at both ends of the cell, 3 adoral organelles and plates with 4 reniform uni-windows. Apocoleps magnus spec. nov. is defined by the following features: body elongated and slightly curved, about 100–120μm× 35–45 μm in vivo; an...     

Distribution of ciliates in relation to environmental factors along the coastline of the Gulf of Gabes, Tunisia

We studied the seasonal distribution of the ciliate community coupled with environmental factors along the coast at three stations sampled (from March 2006 to February 2007) in the Gulf of Gabes (Tunisia, Eastern Mediterranean Sea). A total of 56 species belonging to 11 orders, were identified. Harbor of Gabes station was more diversified (45 species) than both Tabia (26 species) and Karboub (31 species) stations. The ciliate assemblage was numerically dominated by Spirotrichea in Tabia (82% of the total abundance), in the Harbor of Gabes (86% of the total abundance), whereas, in Karboub, Spirotrichea represented only 40% of the total abundance. The unexpected lower quantitative importance of Spirotrichea in Karboub station was apparently the result of the high salt concentration found in water samples throughout the study, probably originating from the saline area surrounding Karboub station, known as Sabkha. The distribution of species in the nearshore of the Gulf of Gabes seemed most likely influenced by the combined effects of temperature, salinity and hydrographic conditions.     

中国北部黄海近岸水体周丛硅藻的群落群集动态特征的研究

The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time interval of 1, 3, 7, 10, 14, 21 and 28 d from two depths of 1 and 3 m. The dynamics of diatom colonization process had a similar pattern in community structure and fitted the logistic model in growth curve at both depths. The maximum abundance and the time for reaching 50% maximum abundance （10 d） showed no significant differences （P〉0.05） between two depths 1 and 3 m. Although the diatom communities repre- sented similar taxonomic composition, they differed in the temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. The species richness showed significantly higher values during the colonization period more than 14 d, while the species diversity and evenness rep- resented a higher variability with significantly different values （P〈0.05） at a depth of 1 m than at a deeper layer. The results suggest that the diatom colonization follows the logistic model growth curve and differs in colonization features between different depths in the coastal waters, and that the sampling strategy at i m is more effective to detect the ecological features for bioassessment in marine ecosystems.     

基于形态学与核糖体DNA及其cDNA高通量测序的海洋沉积物中纤毛虫多样性比较

高通量测序技术广泛应用于环境真核微生物多样性的研究,可检获较之传统形态学方法更高的多样性。然而,检获的高分子多样性与基于形态的物种多样性在构成上的差异仍然不明。本研究首次对比分析了基于形态学的南黄海沉积物中的纤毛虫物种多样性与基于核糖体18S DNA和c DNA高通量测序的多样性异同。结果表明:形态鉴定获得8纲、20目、30科、36属共97种纤毛虫;DNA测序检获10纲、28目、55科、76属共174个OTUs;而通过c DNA测序获取的纤毛虫多样性最高,获10纲、31目、68科、99属共284个OTUs。研究发现,形态学方法检获的纤毛虫均为底栖生纤毛虫;两种分子手段检获的多样性更高,群落结构更为近似,覆盖了形态鉴定所获的绝大部分类群。但DNA测序还检获了序列比例高达90%的浮游类群,可能源于包囊或死亡沉降的物种;而c DNA测序检获了约7%的浮游纤毛虫序列。较之DNA测序,c DNA法检获的底栖纤毛虫在群落结构上与形态学结果更为接近。本研究表明,分子手段有助于更全面地揭示沉积物中的纤毛虫多样性,DNA测序可同时揭示休眠包囊、胞外DNA及过去群落的信息,而c DNA测序在研究活动纤毛虫多样性上更有优势。     

Trophic interactions of the pelagic ciliate Stentor spp. in North Patagonian lakes

The zooplankton of oligotrophic lakes in North Patagonia is often dominated by mixotrophic ciliates, particularly Stentor amethystinus and Stentor araucanus. Therefore, we tested whether Stentor spp. (i) is an important food for juvenile endemic (Cheirodon australe, Galaxias maculatus, Odontesthes mauleanum, Percichthys trucha) and introduced (Oncorhynchus mykiss) fish species, and (ii) represents a remarkable grazer of bacteria. Ingestion rates of fish estimated by disappearance of Stentor in feeding experiments ranged between 8 (G. maculatus) and 53 (C. australe) ciliates per fish and day, and assimilation rates measured by using radioactively labelled Stentor ranged between 3 (P. trucha) and 52 (C. australe) ciliates per fish and day. However, although we detected the consumption of Stentor by fish, the daily consumption amounted to at most 0.2% of the fish biomass which can not cover the energy requirement of the fish. Furthermore, the daily consumption was equivalent to a maximum of 1.6% of the Stentor standing stock so that fish predation does not seem to be an important mortality factor for the ciliates. The clearance rate of Stentor sp. on natural bacteria was on average 3.8 μl cil⁻¹ h⁻¹. The daily ingestion (mean 3.9 ng C cil⁻¹ d⁻¹) was about 3.5% of the individual biomass of Stentor sp. Therefore, bacteria ingestion might explain a ciliate growth rate of appr. 1% d⁻¹, which was about 17% of the photosynthesis of endosymbiotic algae. The maximum density of Stentor sp. in the lake could ingest about 1 μg C L⁻¹ d⁻¹ bacteria which is only 3% of average bacterial production. Thus, grazing by Stentor sp. does not seem to be a main loss factor for the bacteria.     

海水养殖水体中危害性纤毛虫原生动物研究Ⅰ.盾纤目习见类群的口器结构及鉴别特征

对发现自我国北方海区养殖环境中危害性盾纤目纤毛虫的常见类群 (16属 )之口器结构、一般形态学与鉴别特征以及属种模式做了概要性介绍。同时涉及了生活类型、已知种的分布范围、纤毛图式水平的示差鉴别及属级定义并借助模式图例为该类广泛分布而又不易识别的病害纤毛虫类群提供了一份简明的病原鉴定资料