Ceratium Species Research Articles

Diversity of Ceratium Schrank (Dinophyceae) species in the surface waters of Dhamra, Odisha, Eastern India

Aim: To study the diversity of Ceratium Schrank (Dinophyceae) species in the surface waters of Dhamra, Odisha, Eastern India. Methodology: The present study was carried out at six GPS coordinated stations in the coastal waters of Dhamra, Odisha during pre-monsoon, monsoon and post-monsoon periods (March 2021, October 2021 and February 2022). Standard methods were followed for measuring sea surface temperature, transparency, dissolved oxygen, pH, alkalinity, salinity, silicate, nitrite, nitrate and phosphate. Samples were collected by filtration as well as towing method. Light microscopy and scanning electron microscopy were carried out for the identification of Ceratium species. Results: A total of twenty-eight species of Ceratium were observed. Out of the reported twenty-eight species, C. massiliense var. armatum and C. breve var. breve have not been reported earlier in the coastal waters of Dhamra, Odisha. Diversity of Ceratium species was influenced by various parameters. Analyses of water quality parameters, showed that the transparency, salinity, alkalinity, nitrite and phosphate were maximum during pre-monsoon whereas temperature and silicate concentration were higher in monsoon. Similarly, during post-monsoon, pH and nitrate concentration were maximum. Availability of nutrients might have probably influenced the distribution of Ceratium species in the coastal waters and one of the sources was from the riverine influx. Interpretation: Abundance of Ceratium species is probably regulated by alkalinity, high transparency, salinity and phosphate concentration in the surrounding water. Dhamra coastal water is conducive for the growth of Ceratium sp. which primarily uses phosphate for developing the horns. Key words: Abundance plot, Bray-Curtis, Ceratium, Dinophyceae, Species diversity

Ceratium furcoides (Levander) Langhans in reservoirs at the Ebro watershed, Spain and Sao Paulo state, Brazil

This study compares the morphological characteristics of the dinoflagellate Ceratium furcoides from three Ebro basin reser¬voirs (Spain) and from six reservoirs at São Paulo state (Brazil) with the aim to identify the distinct morphotypes of Ceratium furcoides in Spain and Brazil. We studied the physical and chemical variables to determine the trophic state of each reservoir. Unlike Ceratium hirundinella, Ceratium furcoides is not a frequent species within the plankton community at Ebro Basin reservoirs, however, this species has been responsible of one monospecific bloom at El Val reservoir. Nevertheless, both Ce-ratium species are considered invasive in South America. Ceratium furcoides has displaced C. hirundinella at São Paulo state reservoirs, reaching high densities, to the extent of forming monospecific blooms. Morphometric analysis was performed by optic and electronic microscopy (DIC and SEM respectively). The analysis shows significant differences in: i) total cell length, ii) horns length and iii) presence or absence of a fourth horn. While the microscopic study allows differentiating morphotypes according to the reservoir typology, a deeper study using molecular genetic techniques on the different populations of C. fur¬coides would allow to know better the relationship between the dinoflagellate dynamics and the reservoirs trophic states.

Biodiversity in the occurrence of different species of phytoplankton along the Chennai coast

Phytoplankton is the major food of zooplankton and small pelagic occurring along the Chennai coast. The distribution of phytoplankton vary from place to place and the occurrence of different species decides the biodiversity of the ecosystem. This paper describes the occurrence and the characteristics of most common phyto organisms along the Chennai coast using primer 6.0 software. The phytoplankton distribution consists of dissolved volume, Ceratium species, Navicula, Bidulphia, Nitzschia, Gyrosigma and Chlorella during the year’2011. The occurrence of the phytoplankton, Chaetoceros, 38.01%, followed by Thalasirrothrix is 11.95%, Nitzschia is 8.94%, Navicula, 8.19%, Gyrosigma is 7.22%, Bidulphia is 6.57%, Coscinodiscus, 5.85%, Pleurosigma, 5.81%, Ceratium species, 4.58%, Chlorella is 2.74% and dissolved volume is 0.03% of the total phytoplankton distribution. The primer graphs for eclidean distance of different months for different species of phytoplankton were drawn. From the bray Curtis similarity graph it is evidenced that the distribution of phytoplankton component. Chaetocerus is far from the other species since its occurrence is more during the month of Jan’11. From the similarity graph, it is found that Chaetoceros and Coscinodiscus are closely related, Ceratium species and Pleurosigma are closely related, Navicula and Bidulphia are closely related. The occurrence of Chlorella is not closely related to any species. Bubble plots displays the individuals species abundances in relation to the overall community pattern. Funnel graphs are drawn for the number of phytoplankton. As the temperature increases during the summer month the phytoplankton decreases. The environmental variables, temperature, pH, salinity, TSS, TDS, dissolved oxygen, chlorophyll a, b and c, primary productivity, gross and net, nutrients, phosphate and ammonia vary significantly with the phytoplankton occurrence. The correlation coefficient of occurrence of Ceratium-Nitzschia (0.78), Ceratium- Thalassirothrix-(0.98), Ceratium- Pleurosigma (0.90), Navicula-Bidulphia (0.57), Navi cula-Nitzscia (0.10), Navicula -Gyrosigma (0.95), Navicula- Chaetoceros (0.93), Navicula- Coscinodiscus (0.57), Navicula-Pleurosigma (0.19), Bidulphia-Nitzschia (0.50), Bidulphia - Gyrosigma (0.31), Bidulphia- Chaetoceros (0.25), Bidulphia- Coscinodiscus (0.94), Nitzschia-Thalassirothrix (0.82), Nitzschia-Coscinodiscus (0.34), Nitzschia-Pleuro -sigma (0.64), Gyrosigma-Chaetoceros (0.99), Gyrosigma- Coscinodiscus (0.33), Gyro sigma-Pleurosigma (0.26), Chaetoceros-Coscinodiscus (0.26), Chaetoceros –Pleurosigma (0.30), Gyrosigma-Chlorella (0.09), Chaetoceros-Chlorella (0.05). The species richness, d varies from 0-2.40, Pielous’s index of evenness (J') varies from 0-0.97, Shannon–Wiener’s diversity index (H'), 0-2.32, simpson’s dominance index, , 0-0.9. The species richness, species evenness, species diversity and dominance index are all significant at p  0.05. The correlation between the environmental variables and the phytoplankton species distribution were worked out.

Speciation and Infrageneric Classification in the Planktonic Dinoflagellate Tripos (Gonyaulacales, Dinophyceae)

Background:: The genus Tripos, formerly known as marine species of Ceratium, is the dinoflagellate with the greatest number of species and infraspecific taxa (~800) due to the high morphological intraspecific variability of numerous species. In the past, the species of Tripos were proposed into distinct genera. Objective:: To propose an infrageneric classification and to review the taxonomy and nomenclature of each taxon in order to establish the correct species and synonymy. Method:: Observations from the Mediterranean Sea, and Atlantic and Pacific Oceans, a review of the original descriptions and further literature, and the available molecular data. Results:: A re-instatement of this generic split is not justified due to the difficulties to circumscribe the basal subgenera Amphiceratium and Archaeceratium, and the polyphyletic character of Biceratium. The subgenus Amphiceratium is dismembered after the classification of the sections Inflata and partially Fusiformia into Archaeceratium. The subgenus Tripos (autonym) replaces other names such as Tripoceratium or Orthoceratium. Based on the original descriptions, the records of T. furca and T. lineatus correspond to T. eugrammus and T. furca, respectively, and T. macroceros has been reported as T. contrarius. The names T. belone and T. carriensis have been misapplied for T. pacificus and T. volans, respectively. Tripos arcuatus, T. gracilis, T. inclinatus, T. scapiformis and T. subcontortus are revived to replace T. euarcuatus, T. declinatus, T. horridus, T. longirostrum and T. contortus, respectively. The species T. ramakrishnae and T. fusus var. schuettii were described from individuals infected by endoparasites. Tripos rotundatus comb. nov. is proposed for C. digitatum var. rotundatum. Conclusion:: Tripos is restricted to 57 correct species, although the speciation and synonymy are incomplete due to lack of studies in the life cycle and molecular data.

Qualitative and quantitative study of phytoplankton of River Wainganga near Markandadeo, Dist. Gadchiroli (M.S.)

Phytoplankton is a heterogeneous group of micro-organism and plays a major role in the food chain of aquatic ecosystems by biosynthesis of organic matter and thus they act as primary producers of food. The phytoplankton of many Indian rivers consists of diverse assemblages of major taxonomic groups. Many of these forms have different physiological and environmental requirements. During the investigation period of two years phytoplankton were collected randomly from three different sites i.e. S1, S2 and S3 of river Wainganga for qualitative and quantitative analysis. During the course of study total 31 species of phytoplankton were recorded belonging to five different classes. Seasonal analysis of plankton from this lotic water body showing wide diversity of phytoplankton. Chlorophyceae or green algae comprise an important phytoplanktonic group both in terms of abundance (15 species) and frequently occurrence and Bacillariophyceae (Diatoms) was represented by seven species. Myxophyceae or blue-green comprises of six species and Euglenophyceae were represented by two species i.e. Euglena sp. and Phacus sp. while Dinophyceae was represented by only one species of genus Ceratium.

ФИТОПЛАНКТОН ОТКРЫТОЙ СЕВЕРО-ВОСТОЧНОЙ ЧАСТИ ЧЕРНОГО МОРЯ В ЗИМНИЙ ПЕРИОД 2017 г.

The seasonal dynamics of phytoplankton development in winter is less studied than in other seasons, therefore it is of certain interest. The article presents the results of the study of taxonomic structure and the level of quantitative development of phytoplankton in the open area of the Black Sea northeastern shelf in December 2017. 34 Species belonging to 5 divisions of Bacillariophyta, Dinophyta, Chrysophyta, Cryptophyta and Chlorophyta were found in phytoplankton. The maximum species diversity was recorded among Dinophyta (21 species) and Bacillariophyta (8 species), other divisions were represented by 1–2 species. Previous studies have shown that the taxonomic composition of phytoplankton in the open area of the Black Sea northeastern part includes a large number of dinophytic species, while the diversity of diatoms is significantly inferior to them. The abundance and biomass of planktonic algae were extremely low during the study period (on average, 2706 cells / liter 11.49 mg / m3 ). The maximum abundance of species (26) and the highest values of quantitative development (5399 cells / l and 32.27 mg / m3 ) were observed in the area of the Taman Peninsula. These values were 2–4 times higher than the values of abundance and biomass found in the rest of the study area. The abundant development of planktonic algae was probably facilitated due to the ingress of waters of the Azov Sea, richer in nutrients, into the Kerch region of the Black Sea. Bacillariophyta (Pseudo-nitzschia pseudodelicatissima, P. seriata, Thalassionema nitzschioides, Pseudosolenia calcar-avis, Ditylum brightwellii), and Dinophyta (Prorocentrum cordatum, Prorocentrum micans and Ceratium species) formed the basis of the abundance (55 and 23 %, respectively) and biomass (24 and 68 %) of phytoplankton. Cryptophyta (Plagioselmis prolonga and P. punctata) accounted for 16 % of the phytoplankton population during the study period. Among the Chrysophyta and Chlorophyta, the species Octactis octonaria and Pterosperma undulatum, common for the open part of the Black Sea, were observed in small quantities. The favorable ecological situation in this region of the sea is proved by the complete absence of Cyanophyta and Euglenophyta, which are indicative of polluted and desalinated sea areas.

A newly recorded species of freshwater blooming dinoflagellates from China and its ecological risks

2019年6月，在山东省峡山水库多个位点采集到角藻属（Ceratium）样品，并发现其在局部位点形成明显的浅褐色水华.系统发育分析结果显示该种与角藻属常见种飞燕角藻（C.hirundinella）亲缘关系最近，但形态学上有明显区别，前者具有1块间插板和3个顶板，而飞燕角藻具有4块顶板.通过对比，发现该种为我国淡水甲藻门未经描述的新记录物种——拟二叉角藻（C.furcoides）.峡山水库中，水华发生位点的水体叶绿素a浓度高达125.77 μg/L，拟二叉角藻的密度达1.23×10⁶ cells/L，占总藻细胞密度的1.21%.细胞数量上，占优势的主要是尖头藻（Merismopedia spp.）和浮丝藻（Planktothrix spp.）等一些丝状蓝藻；但因个体细胞体积非常大，鲜重高达86.31 mg/L，占总藻鲜重的49.34%，因此在生物量上拟二叉角藻是绝对优势种.此外，通过核查采自我国东北、华中、西南地区不同时期、温度较高季节的多个标本，基于其自身特性和分布特点，本研究认为拟二叉角藻偏好高温和富营养水体，有在我国不同地区水体扩张并形成水华的潜在能力.;In recent years,dinoflagellate blooms had occurred frequently, and most of them were caused by the species of genus Peridinium and Peridiniopsis, and caused by the species of genus Ceratium were rare. Recently, however, the genus Ceratium species had been found throughout the world in the water bodies such as eutrophic reservoirs and fish ponds. In June 2019, some samples of the genus Ceratium were collected at various sites in Xiashan Reservoir of Shandong Province and found that it formed obvious light brown water blooms at local sites. Phylogenetic analyses showed that this species had the closest relationship with the common species C. hirundinella of the genus Ceratium, but the morphologically, the former had one intercalary plate and three apical plates, which were different from the C. hirundinella with four apical plates. By contrast, it is a newly recorded species of dinoflagellates-C. furcoides, which do not have been described in China. It has been reported as an invasive and water blooming species, which is often found in eutrophic water bodies during high-temperature seasons. In the Xiashan Reservoir, the chlorophyll-a concentration at the bloomed site is as high as 125.77 μg/L, and the density of the C. furcoides is 1.23×10⁶ cells/L, accounting for 1.21% of the total algal cell density. The number of cells is dominated by some filamentous cyanobacteria such as Merismopedia spp. and Planktothrix spp.; however, due to the very large individual cell size of the C. furcoides, its fresh weight is as high as 86.31 mg/L, accounting for 49.34% of the total algae fresh weight, which is the absolute dominant species in biomass. In addition, by examining multiple specimens collected from northeast China, central China, and southwest China in different periods during high-temperature seasons, based on its own and distribution characteristics, we held that C. furcoides preferred the high temperature and the eutrophic waters, and it has the potential ability to expand and form water bloom in different areas of China.

Towards a comprehension of Ceratium (Dinophyceae) invasion in Brazilian freshwaters: autecology of C. furcoides in subtropical reservoirs

Ceratium species are not a common component of freshwater phytoplankton in South America. However, these dinoflagellates have often been observed in many water bodies over the past two and a half decades. We investigated Ceratium furcoides’ abundance and morphological variation during its initial phase of colonization (2012–2013) in two subtropical reservoirs in southern Brazil in order to explore which environmental factors were related to the occurrence, persistence and bloom formation of this dinoflagellate in those environments. Biomass of C. furcoides showed a strong seasonal pattern, in which warm seasons led to an increase in population density, resulting in cell-size reduction, while in the cold seasons cells increased in volume. Maximum densities over 2,500 cells ml−1 were observed in spring–summer periods in both reservoirs. C. furcoides’ abundance in the studied reservoirs was associated, primarily, with a combination of optimal conditions of temperature, organic matter, and pH, and secondarily, with nutrient availability. The possible factors for the successful colonization performed by C. furcoides across distinct Brazilian waterbodies include good swimming performance, low herbivory pressure, and ability to form dense blooms, as strategies that allow maintenance of populations and effective dispersal.

First record of expansive Ceratium Schrank, 1793 species (Dinophyceae) in Southern Brazil, with notes on their dispersive patterns in Brazilian environments

Ceratium Schrank is a planktonic dinoflagellate ubiquitous in temperate and subtropical freshwater environments from Northern Hemisphere. Over the past two decades, Ceratium species have been recorded in South American water bodies, with expansive behavior and fast colonization. This study registered C. furcoides (Levander) Langhans and C. hirundinella (O. F. Müller) Dujardin for the first time in South Brazil. Ceratium furcoides was found in samples from States of Paraná and Rio Grande do Sul and C. hirundinella occurred only in the southernmost Brazil. No co-occurrence of these species was detected on samples. The morphological variation, as well as the dispersal patterns of these species in Brazilian environments, is discussed based on LM and SEM analyses.

Forty years of monitoring water quality in Grasmere (English Lake District): separating the effects of enrichment by treated sewage and hydraulic flushing on phytoplankton ecology

1. Grasmere is a small lake (area: 0.64 km2; mean depth 7.7 m) in a catchment with high rainfall (typically 2–3 m annually), which subjects the lake to intermittent episodes of rapid flushing. 2. An overview of the trends in water quality and of phytoplankton of Grasmere is presented, covering almost 40 years of observations following the construction and commissioning of a waste-water treatment plant to serve a nearby village. 3. There was a threefold increase in annual areal phosphorus loading during the 25 years following commissioning. Moving the original outfall of the sewage works from the River Rothay, just above its inflow into Grasmere, to a point in the lake, 7.5 m below the surface and, normally, below the summer thermocline, mitigated direct biomass response to epilimnetic enrichment. Maximum concentrations of chlorophyll a increased about twofold, but the annual mean concentrations altered little; interannual variability seems to relate more to flushing than to changing fertility. Cyanobacterial blooms occurred during years of relative summer drought. 4. Since 1996, nutrient loadings have been alleviated by better wastewater management and tertiary treatment of effluents discharged during dry weather. Recent chlorophyll a maxima have declined with the reduced supportive capacity of phosphorus availability. 5. An updated annotated list of phytoplankton species known to have occurred in Grasmere is provided. The incidence and abundance of species supposed to indicate eutrophication probably reflect the enrichment that has occurred, while others, mostly associated with oligo-mesotrophic lakes, seem to have declined. Inherently slow-growing species (of Ceratium, Microcystis) have been unable to establish a significant presence in the lake. A group of algae in Grasmere that indicate nutrient-poor, acidic habitats are suggested to originate in the catchment and flourish briefly in the wake of flushing events.

Ceratium Schrank (Dinophyceae) del parque nacional Sistema Arrecifal Veracruzano, Golfo de México, con clave para identificación

Se estudió la morfología de 33 especies de Ceratium (38 incluso los taxa infraespecíficos) con base en aproximadamente 600 muestras de red (20 µm) tomadas de mayo de 2005 a marzo de 2008 en ocho estaciones de muestreo en el sector noroeste del Parque Nacional Sistema Arrecifal Veracruzano, la parte sur del Golfo de México. Para cada especie se dan descripciones cortas, así como la sinonimia. La variación de tamaño de las células, el promedio y la desviación estándar se presentan para la mayoría de las especies. Para 23 taxa se proporcionan notas sobre sus afinidades, al igual que comentarios taxonómicos, nomenclaturales y biogeográficos. Se incluye una clave dicotómica para la identificación, así como las fotografías en microscopio fotónico y dibujos a línea de todas las especies encontradas. Ceratium dens, C. bigelowii, C. limulus, C. tripos f. tripodoides y C. declinatum var. angusticornum son nuevos registros para la parte mexicana del Golfo de México.

A Genus Name for the Marine Species of Ceratium. : Reply to Commentary by A. Calado and J.M. Huisman on Gómez, F., Moreira, D., and López-García, P. (2010). Neoceratium gen. nov., a New Genus for All Marine Species Currently Assigned to Ceratium (Dinophyceae). Protist 161: 35-54

A Genus Name for the Marine Species of Ceratium. : Reply to Commentary by A. Calado and J.M. Huisman on Gómez, F., Moreira, D., and López-García, P. (2010). Neoceratium gen. nov., a New Genus for All Marine Species Currently Assigned to Ceratium (Dinophyceae). Protist 161: 35-54

Commentary: Gómez, F., Moreira, D., and López-García, P. (2010). Neoceratium gen. nov., a New Genus for All Marine Species Currently Assigned to Ceratium (Dinophyceae). Protist 161: 35-54

The recent publication by Gomez et al. (2010) described DNA sequence studies that demonstrated a taxonomic distinction between the freshwater and marine taxa of the dinoflagellate genus Ceratium. Since the type of Ceratium is a freshwater species, a segregate genus for the marine species was therefore required. The new genus name Neoceratium was erected, with type species N. furca, and 76 additional new combinations in this genus proposed. In the discussion that accompanied the description, the authors recognized that several legitimate generic names had been proposed in the nineteenth century for different species of Ceratium, but for various reasons these names were rejected, primarily, “to avoid potential confusion derived from the use of previous subgeneric names” (Gomez et al. 2010, p. 44).We contend that the reasons for rejecting these earlier legitimate generic names, each with their type species included in Neoceratium as circumscribed by Gomez et al. (2010), were inadequate and that the name of the newly recognized genus should have been adopted from one of these historical names.

Occurrence of a subsurface anticyclonic eddy, fronts, and Trichodesmium spp.

Eddies and fronts created by geostrophic balance between counter-rotating currents are hydrodynamic processes that concentrate or dilute plankton and suspended material by physical processes of accumulation, retention, or dispersion. Over Campeche Canyon, in the southern Gulf of Mexico, observations revealed an anticyclonic eddy, a cyclonic current off the continental shelf, and an associated thermal front in their common boundary. Along this front there was high Trichodesmium spp. occurrence. Three water masses were found in the upper 120 m layer: Caribbean Tropical Surface Water (CTSW), Caribbean Subtropical Underwater (CSUW), and Gulf Common Water (GCW). The frontal zone between the warm core and cyclonic circulation was observed below the hot summertime mixed layer. The presence of Trichodesmium spp. was associated with the front, indicating its influence on the distribution of this diazotrophic cyanobacterium that enters the Campeche Canyon region via modified CTSW. The associated phytoplankton was dominated by tropical oceanic species of diatoms and dinoflagellates, especially species of Ceratium.

Neoceratium gen. nov., a New Genus for All Marine Species Currently Assigned to Ceratium (Dinophyceae)

The dinoflagellate genus Ceratium contains marine and freshwater species. Freshwater species possess six cingular plates, thick plates in the concave ventral area and usually develop a third hypothecal horn. The marine Ceratium species (>62 species) possess five cingular plates and thin plates in the concave ventral area; a third hypothecal horn is atypical. Resting cysts, a common feature in the freshwater species, are unreported in marine species. We illustrate for the first time resting cysts in marine Ceratium species (C. furca and C. candelabrum). We obtained small subunit ribosomal RNA gene (SSU rDNA) sequences of 23 Ceratium species (more than one third of the total marine species described so far), with representatives of the four acknowledged subgenera. Phylogenetic analyses including the type species, the freshwater C. hirundinella, showed that the four available sequences of freshwater species formed a strongly supported subclade, very distant from the marine cluster. Our data support the splitting of Ceratium sensu lato into two genera. Ceratium sensu stricto should be reserved for freshwater species possessing six cingular plates (three cingular plates in dorsal view). The new genus name, Neoceratium gen. nov. should be applied to the marine species of Ceratium sensu lato that possess five cingular plates (two cingular plates in dorsal view).

Growth of dinoflagellates, Ceratium furca and Ceratium fusus in Sagami Bay, Japan: The role of vertical migration and cell division

To better understand the mechanism underlying the bloom outbreaks of dinoflagellates, Ceratium furca, and Ceratium fusus in the temperate coastal area of Sagami Bay, we investigated the diel changes of vertical migration, swimming speed, cell volume, and cell division. Our results from both the field and laboratory indicate that C. furca and C. fusus can migrate vertically between surface and sub-surface layers to avoid strong sunlight (>1000 μmol m −2 s −1). Diel vertical migration (DVM) of C. furca was observed in the laboratory, while that of C. fusus was not observed. C. furca demonstrated a constant DVM rhythm, i.e., their cells began to descend from the surface before the light was extinguished, and ascended into the surface before the light was turned on. The downward and upward migrations of the cells occurred at every 3 h before turning on and off the light, suggesting that the DVM pattern was independent of nutrient concentration. The swimming speeds of C. furca (avg. 250 μm s −1) were always faster than those of C. fusus (avg. 75 μm s −1). In addition, the speeds of C. furca during light periods were faster than those during dark periods, whereas the speeds of C. fusus remained relatively constant. A higher proportion of dividing cells was recorded near dawn (05:00–07:00 h). Cell volumes of C. furca and C. fusus did not markedly change between 12:00 and 21:00 h, but gradually increased until 03:00 h and then sharply decreased. Furthermore, the cell volume of the two Ceratium species was significantly shifted to the temporal pattern of cell division. Combined with the DVM manner of two Ceratium and cell division timing, only C. furca divided at the bottom, and then moved toward the surface shortly before the dark to light transition. Based on our observations, C. furca has an ecological advantage due to their DVM activity, since nutrients can be obtained well in the near bottom layers, while during the daytime, light present in nutrient-depleted surface water can be obtained using their high swimming speed. On the other hand, C. fusus stimulated by low salinity conditions, might be dependent on external environmental conditions such as additional nutrients following freshwater discharge by heavy rainfall because they may not perform active DVM due to a slow swimming ability. Our findings support that specific characteristics, including the DVM behavior in C. furca, yield a competitive advantage over C. fusus in Sagami Bay.

Similar patterns of patterns of community organization characterize distinct groups of different trophic levels in the plankton of the NW Mediterranean Sea

Abstract. Planktonic populations were sampled over a 4 week period in the NW Mediterranean, at a site subject to little vertical advection during the Dynaproc 2 cruise in 2004. The characteristics of the phytoplankton, the tintinnid community and the zooplankton have recently been described in detail. Based on these studies, we compared the characteristics of 3 well-circumscribed assemblages of different trophic levels: Ceratium of the phytoplankton, herbivorous tintinnids of the microzooplankton, and large (>500 μm) omnivorous and carnivorous copepods of the metazoan zooplankton. In all three groups, diversity as H' or species richness, was less variable than concentration of organisms. Plotting time against species accumulation, the curves approached plateau values for Ceratium spp, tintinnids and large copepods but only a small number of species were consistently present (core species) and these accounted for most of the populations. For Ceratium core species numbered 10, for tintinnids 11 species, and for large copepods, core species numbered 4 during the day and 16 at night. Ceratium, tintinnids and large copepods showed some similar patterns of community structure in terms of species abundance distributions. Ceratium species were distributed in a log-normal pattern. Tintinnid species showed a log-series distribution. Large copepod assemblages were highly dominated with night samples showing much higher abundances and greater species richness than day samples. However, species abundance distributions were similar between day and night and were mostly log-normal. The paradox of the plankton, describing phytoplankton communities as super-saturated with species, extends to the microzooplankton and zooplankton.

Preliminary survey of potentially harmful dinoflagellates in Nigeria´s coastal waters.

In many coastal states the presence and impacts of harmful dinoflagellates have been investigated and documented in the literature. Scientists and government officials in many countries routinely monitor their coastal waters for harmful algae in order to prevent harvesting of contaminated seafood. But this is not the case for Nigeria, a coastal state in the Gulf of Guinea, West Africa. The present work reports findings from a first attempt to monitor potentially harmful algae in the coastal waters of Nigeria. Samples were collected from specific locations that included a coastal sea, a lagoon, estuaries and creeks along Nigeria's coastline in November 1999 and April 2001. Potentially harmful dinoflagellates recorded during these periods included 3 Ceratium species, 5 Dinophysis species, 3 Gonyaulax species, 1 Gymnodinium sp, 1 Lingulodinium species, 4 Prorocentrum species and 1 Scrippsiella species. The potential ecological and human health risks associated with similar species in the literature are highlighted.

Phytoplankton biodiversity and NW Mediterranean Sea warming: changes in the dinoflagellate genus Ceratium in the 20th century

Our knowledge of the response of phytoplankton to climate change is restricted by the lack of phytoplankton long-term studies, especially those reporting species data. To circumvent this problem, we combined recent data from sampling at monitoring sites with old bibliographic data. The study was conducted on the genus Ceratium (planktonic dinoflagellates) in the NW Mediterranean, as numerous studies have been conducted in the area since the beginning of the 20th century. In ad- dition, species of this highly diverse genus are known to be particularly sensitive to water tempera- ture, and should thus be responsive to global warming. The temporal distribution of Ceratium species over the last century showed a progressive disappearance from the surface layer of likely stenother- mic species, which may have moved to deeper layers in response to water warming, along with a de- crease of species richness during the annual cycle. Seasonal and phenological aspects of Ceratium assemblages were also affected, as illustrated by the earlier timing in the minimum of richness. A change in the overall species assemblage also occurred from past to present in the Ligurian Sea, sug- gesting a warming in this area consistent with the development in surface water temperatures. Our results suggest that Ceratium species may constitute good biological indicators of warming in the NW Mediterranean Sea. In addition, the present study showed the importance of time-series data and the value of historical literature as the basis for ecological studies of long-term trends needed to substan- tiate our current understanding of the impact of global change on marine biodiversity.

Population Development of the DinoflagellatesCeratium furca andCeratium fusus during Spring and Early Summer in Iwa Harbor, Sagami Bay, Japan

To examine the population development of the dinoflagellates, Ceratium furca and Ceratium fusus, daily field monitoring was conducted between April and July 2003 in the temperate coastal water of Sagami Bay, Japan. During the study period, the concentrations of C. furca were always lower than those of C. fusus. A sharp increase in the densities of both species was recorded on 5 May showing the maximum cell concentrations (C. furca = 14,800 cells L-1, C. fusus = 49,600 cells L-1). In the 7 days prior to the May bloom of the Ceratium species (29 April to 1 May), the highest density of the heterotrophic dinoflagellate Noctiluca scintillans was observed. Additionally, a second bloom of C. fusus occurred on 22 July. Here, two causes of the significant increases in the Ceratium populations during the two blooming periods (first time; 1 to 8 May, second time; 15 to 22 July) are presented. First, an increase in the nutrients of the surface layer regenerated by the breakdown of blooms by N.scintillans could be considered as a major cause of the population increase of the two Ceratium species. Second, a decrease in salinity (to 27 psu) was correlated with the later bloom ofC. fusus. These results suggest that the population development of the two Ceratium species requires nutrients regenerated after the reduction of the diatom population byN. scintillans and, forC. fusus, continuous low salinity conditions, compared to other environmental factors during the rainy season. Key words: Ceratium furca; Ceratium fusus; Noctiluca scintillans; Bloom process; Environmental factor