The drifting dinoflagellate Ceratium furcoides (Levander) Langhans 1925: fundamental niche shift during global invasion

Hydrobiologia - Ceratium furcoides is a freshwater dinoflagellate originally from cold waters of northern Europe that has been expanding its distribution into new areas worldwide. Species...     

Potential distribution of the invasive freshwater dinoflagellate Ceratium furcoides (Levander) Langhans (Dinophyta) in South America

Dinoflagellates of the genus Ceratium are predominantly found in marine environments, with a few species in inland waters. Over the last decades, the freshwater species Ceratium hirundinella and Ceratium furcoides have colonized and invaded several South American basins. The purpose of this study was to create a distribution model for the invasive dinoflagellate C. furcoides in South America in order to further investigate the basins at potential risk, as well as the environmental conditions that influence its expansion. This species is known to develop blooms due to its mobility, resistance to sedimentation, and optimized use of resources. Although nontoxic, blooms of the species cause many problems to both the natural ecosystems and water users. Potential distribution was predicted by using a maximum entropy algorithm (MaxEnt). Model was run with 101 occurrences obtained from the scientific literature, and climatic, hydrological and topographic variables. The developed model had a very good performance for the study area. The most susceptible areas identified were mainly concentrated in the basins between southeastern Brazil and northeastern Argentina. Besides already affected regions, new potentially suitable areas were identified in temperate regions of South America. The information generated here will be useful for authorities responsible for water and watershed management to monitor the spread of this species and address problems related to its establishment in new environments.     

Spatial and temporal variations of Dinophyceae in subtropical reservoirs in southern Brazil

Knowledge of dinoflagellate diversity in Brazilian reservoirs is limited, especially in subtropical environments. We investigated as to how nutrients and other environmental variables influenced the biomass of Dinophyceae species in three subtropical ecosystems. The reservoirs Samuara, Faxinal, and São Miguel were sampled fortnightly from 2002 to 2006, and eight dinoflagellate taxa were identified. High temperature was a determining factor for the occurrence of Peridinium africanum Lemmermann. Peridinium umbonatum Stein and P. willei Huitfeld-Kass required high concentrations of nutrients. P. willei was inversely related to temperature and directly related to nutrients. P. umbonatum Stein var. umbonatum Stein showed the largest range of tolerance toward resources. Durinskia baltica Carty &; Cox and Peridinium gatunense Nygaard could be opportunistic, since they did not show any spatial or temporal pattern.     

Spatial and temporal variation of phytoplankton in two subtropical Brazilian reservoirs

The purpose of this study was to verify the longitudinal distribution of phytoplankton biomass in two subtropical Brazilian reservoirs in the State of Paraná and investigate intervening factors on changes in phytoplankton biomass according to functional groups. In the Capivari and Segredo reservoirs, samples were obtained every 3 months during 2002, along a longitudinal axis (fluvial, transition, and lacustrine zones) at different depths. One hundred and eighteen taxa were identified, with Chlorophyceae as the most specious group. During the study period, both reservoirs had mostly low biomass values (less than 1 mm³ l⁻¹). The short retention time of these reservoirs constituted the principal limiting factor to phytoplankton development. Biomass values above 1 mm³ l⁻¹ were observed in the Capivari fluvial zone in March and in the Segredo lacustrine zone in December, with dominance by Microcystis aeruginosa Kütz (L_M) and Anabaena circinalis Rab. (H₁), respectively. Vertical and horizontal gradients of analyzed abiotic variables and phytoplankton biomass were observed. Considering the phytoplankton biomass values, both reservoirs were oligotrophic for the duration of the study. The Canonical Correspondence Analysis (CCA) evidenced temporal and spatial gradients of phytoplankton biomass; nevertheless, it did not follow the classic model proposed for deep reservoirs, since higher biomass was registered in the lacustrine zone during some months and in fluvial zones during other months. Distinct functional groups of phytoplankton characterized both studied reservoirs. Capivari Reservoir was best characterized by L_M and Y groups, indicative of its greater water column stability and higher phosphorus concentration, whereas Segredo Reservoir was principally characterized by the MP functional group, indicative of its greater mixing zone extension and higher nitrate concentration. The obtained results also evidenced the influence of morphometric conditions and watershed purposes as important structuring factors of phytoplankton biomass in these reservoirs. Handling editor: L. Naselli-Flores     

Macrothrix flabelligera, a newly-recorded Cladocera Macrothricidae in Brazilian freshwaters.

A short characterization of Macrothrix flabelligera Smirnov, 1992 (Cladocera, Macrothricidae) is presented, following a recent record of this species in Brazil. General aspects and morphological details of the body of parthenogenetic and ephippial females, as well as of males, are described and illustrated.     

Study of the marine planktonic dinoflagellate Ceratium divaricatum (Dinophyceae), a confused and considerably variable species

The species Ceratium divaricatum (Lemmermann) Kofoid has largely been subject to misidentification and taxonomic confusion. The history of the species is complex: originally illustrated by Bergh (1881) as Ceratium tripos var., for which Lemmermann (1899) gave it the name Ceratium tripos var. divaricatum; the name Ceratium divaricatum was used by Kofoid (1908) with no specification of authors or references. It shows a high degree of morphological variation and development of autotomy of the apical and antapical horns. This great morphological variation has led to misidentifications in routine examinations of phytoplankton materials, and several names have been used for this species, including Ceratium dens, Ceratium porrectum and Ceratium tripos var. ponticum, as well as Ceratium balechii, a proposed new species for intermediate forms. Here, the species is redescribed, on the basis of material from Mexican Pacific coasts. Morphological and ecologic differences exist among this species and other closely related ones. Distribution of C. divaricatum is wider than previously documented (mainly because of previous misidentifications): the North Pacific Ocean, from British Columbia in Canada to temperate or subtropical waters of Mexico, and then is interrupted to reappear again in coasts of Peru and Chile, and also in coasts of the Benguela area, the South‐west Atlantic Ocean. In tropical and equatorial areas of the Pacific Ocean, a more delicate form occurs, herein proposed as a variety of this species: Ceratium divaricatum var. balechii. C. divaricatum and var. balechii may be relatively abundant, even producing non‐toxic red tides, in various spots along coasts of the Pacific Ocean (Canada to Mexico). It appears to be a neritic form, with high sensibility to changes in water temperature, and presumably associated to upwelling areas.     

Inclusion bodies in several species of Ceratium Schrank (Dinophyceae) from the Caribbean Sea examined with DNA-specific staining

Several dinoflagellate species in the genus Ceraiium Schrankwere examined, with the help of a DNA-specific dye, for thepresence of a nucleus, chloroplasts and inclusion bodies. Theabundance of Ceratium in the Caribbean Sea in April 1990 wasbetween 1.3 and 4.9 x 10⁵ cells m^–3 Most Ceratium teresKofoid contained 5–10 small chloroplasts and among 529C.teres cells. 8% possessed an inclusion body. The shape andsize of inclusion bodies varied, and 7% of the inclusions hada DNA-containing particle inside. Similar inclusion bodies werealso observed in Ceratium declinatum f. normale Jörgensen,Ceratium furca (Ehrenberg) Claparede and Lachmann, and Ceratiumfusus (Ehrenberg) Dujardin. Our observations indicated thatinclusion bodies are common in oceanic Ceratium. ¹Present address: Institute of Marine Biology, National TaiwanOcean University, Keelung 20224, Taiwan, ROC     

A fish-kill in Heart Lake, Ontario, associated with the collapse of a massive population of Ceratium hirundinella (Dinophyceae)

SUMMARY. A massive population of the common dinoflagellate Ceratium hirundinella developed in Heart Lake. Ontario, Canada during the summer of 1976 and its sudden collapse and subsequent decomposition depleted dissolved oxygen and resulted in a fish-kill in the lake. The lake was being artificially mixed at the time by supplying compressed air to the bottom waters and the limnological events contributing to the development of the Ceratium population and its collapse appear to be closely related to the artificial destratification process. Artificial destratification during 1976 precluded the development of blue-green algue. The process also led to an increase in the density of herbivorous zooplankters which controlled the development of smaller planktonic algae. Ceratium flourished in Heart Lake because there was little competition for nutrients from other algae and because Ceratium cells are too large to be grazed by the zooplankton. The maximum size of the Ceratium population (53 mm³ 1⁻¹) is apparently the highest biomass reported in the literature and its collapse may have been related to a depletion of inorganic nitrogen. There is apparently no previously published record of a Ceratium -induced fish-kill in a freshwater lake.     

Growth of Ceratium hirundinella in a subtropical Australian reservoir: the role of vertical migration

A study into the photophysiology, growth and migration of Ceratiumhirundinella in Chaffey Reservoir in subtropical northern NewSouth Wales, Australia, revealed that a proportion of cellsformed subsurface accumulations at depths that optimized lightintensity (212–552 µmol photons m^–2 s^–1)for photosynthesis and cell growth. At high incident irradiance,Ceratium migrated downwards from the near-surface waters, avoidinghigh-light-induced, slow-recovering non-photochemical quenchingof photosystem II. Overnight deepening of the surface mixedlayer by convective cooling produced homogeneous distributionsof Ceratium with a significant proportion of the populationbelow the depth where light saturation of photosynthesis occurred.Ceratium migrated towards the surface from suboptimal lightintensities, at a velocity of 1.6–2.7 x 10^–4 m s^–1.Subsurface accumulations occurred under a variety of turbulenceintensities; however, accumulation was significantly reducedwhen the turbulent velocity scale in the mixed layer was >5x 10^–3 m s^–1, beyond which turbulent diffusion dominatedadvection by swimming. The formation of subsurface accumulationswith increased computed water column integral photosynthesisby 35% compared to a uniform cell distribution.     

Plagiodinium ballux sp. nov. (Dinophyceae), a deep (36 m) sand dwelling dinoflagellate from subtropical Japan

A new species of marine sand‐dwelling dinoflagellate, Plagiodinium ballux N. Yamada, Dawut, R. Terada & T. Horiguchi is described from a deep (36 m) seafloor off Takeshima Island, Kagoshima Prefecture, Japan in the subtropical region of the northwest Pacific. The species is thecate and superficially resembles species of Prorocentrum, but possesses an extremely small epitheca. The cell varies from ovoid to a rounded square, and is small (15.0–22.5 μm in length) and laterally compressed. The thecal plates are smooth and the thecal plate arrangement (Po, 1′, 0a, 5″, 5C, 2S, 5?, 0p, 1″″) is similar to that of Plagiodinium belizeanum, the type species of the genus. Molecular phylogenetic analyses based on SSU rDNA and partial LSU rDNA reveal that the dinoflagellate is closely related to P. belizeanum, but it can be clearly distinguished by its size and cell shape. This suite of morphological and molecular differences leads to the conclusion that this deep benthic dinoflagellate represents a new species of the genus Plagiodinium.     

Presence of the dinoflagellates Ceratium dens, C. fusus and C. furca (Gonyaulacales: Ceratiaceae) in Golfo de Nicoya, Costa Rica

Harmful Algae Blooms (HAB) are a frequent phenomenon in the Gulf of Nicoya, Costa Rica, as in other parts of the world. The morphology and physiology of these microalgae are important because HAB species have adaptive characteristics. The production of high concentrations of paralytic toxins by Ceratium dinoflagellates has only been documented at the experimental level. However, this genus has been associated with the mortality of aquatic organisms, including oyster and shrimp larva, and fish, and with decreased water quality. Recently, fishermen reported massive mortality of encaged fish near Tortuga Island (Gulf of Nicoya). Samples were taken from an algal bloom that had produced an orange coloration and had a strong foul-smelling odor. Ultrastructural details were examined with scanning electron microscopy. The dinoflagellates Ceratium dens, C. furca and C. fusus were found in samples taken at the surface. The cell count revealed four million cells of this genus per liter. The morphological variability of these species is high; therefore electron microscopy is an useful tool in the ultrastructural study of these organisms. This is the first time that three Ceratium species are reported concurrently producing harmful blooms in Costa Rica.     

Annual cycle and diversity of species and infraspecific taxa of Ceratium (Dinophyceae) in the Ligurian Sea,northwest Mediterranean1

We examined the well‐documented and species‐rich dinoflagellate genus Ceratium Schrank in the northwest Mediterranean Sea as a possible model for marine phytoplankton diversity and as a biological indicator of global climate change. First, we investigated the influence of counting effort; we then documented temporal changes in Ceratium specific and infraspecific taxa over 2 years (2002 and 2003) in the Villefranche Bay based on a monthly net sampling. Finally, we tried to identify factors associated with shifts in biodiversity. The calculation of taxonomic diversity, regularity, and richness were highly dependent on counting effort. We determined that a minimal sample volume of ～70 L was needed to obtain a good estimation of species richness. The annual cycle was characterized by a seasonal trend of high winter species richness followed by low spring biodiversity. Infraspecific variability not only appeared to depend on water temperature but also seemed to be influenced by bottom‐up control and was strongly affected by top‐down control. Thus, the occurrence of high concentrations of salps (Thalia democratica) and copepods larger than 2 mm (Calanus helgolandicus) coincided with a drastic decrease of Ceratium abundance and diversity during spring 2003. Ceratium is sensitive to both abiotic and biotic factors and could prove to be a good candidate as a biological indicator of global change.     

Acidification of freshwaters by red soil in a subtropical silicate rock area,Okinawa, Japan

Two samples of red soil, one from Gushikawa Recreation Center (GRC) and one from Okinawa Royal Golf Club (ORGC), were examined for particle size distribution, textures, minerals, and chemical compositions. The effects of particle size and grinding of clay minerals on pH, electrical conductivity (EC), and dissolved chemical species were studied in deionized water and river water. The results of red soil solutions were compared with those of acidic waters found in red soil dominated areas. The minimum pH values of soil solutions extracted by deionized water were 4.38–5.36 and 5.16–5.89 and the maximum values of EC were 4.91–16.98mSm^–1 and 3.54–11.23mSm^–1 for GRC and ORGC, respectively. In the river water samples equilibrated with red soils, the minimum pH values were 4.48–5.10 and 4.77–5.91 and the maximum EC values were 19.6–34.2mSm^–1 and 17.5–25.0mSm^–1 for GRC and ORGC, respectively. The values of pH and EC varied with the soil–solution ratio and the particle size. The chemical composition of river water without mixing with red soil shows Na⁺K⁺ and Ca²⁺Mg²⁺. After mixing with red soil, the trend of the concentrations changed to Na⁺K⁺ and Mg²⁺Ca²⁺, which is the same as that of soil solutions in deionized water as well as that of acidic waters found in the red soil area. The pH of the acidic waters was 4.95–5.81 and EC was 7.76–30.0mSm^–1. Laboratory experimental results agreed well with those found in the field in terms of trend of concentrations of the chemical species and pH. Therefore, the results of this study suggest that the low pH and trend of the concentrations of chemical species of the acidic waters found in the red soil dominated areas were the result of the interaction of natural water and red soil.     

Molecular and phylogenetic characterization of Ostreopsis (Dinophyceae) and the description of a new species,Ostreopsis rhodesae sp. nov., from a subtropical Australian lagoon

Cryptic and pseudo-cryptic species are common amongst marine phytoplankton, and may cause misleading inferences of ecological and physiological data of plankton community studies. Deciphering the diversity and distribution of species of the benthic dinoflagellate Ostreopsis is one example, as there are many morphologically indistinct clades that differ greatly genetically and toxicologically from one another. In this study, a new species, Ostreopsis rhodesae from the southern Great Barrier Reef was described. While it initially appeared to be highly similar to several other Ostreopsis species, we found O. rhodesae can be distinguished based on the relative size of the second apical plate (2′), which is twice as long as the APC plate, and separates the third apical (3′) from the third precingular (3′′) plate. Phylogenetic trees based on the SSU, ITS/5.8S and D1-D2 and D8-D10 regions of the LSU rRNA were well supported, and showed a clear difference to other Ostreopsis clades. Compensatory base changes (CBCs) were identified in helices of the ITS2 between O. rhodesae and O. cf. ovata and O. cf. siamensis, which were also present in the same habitat. Fish gill cell lines were toxic to O. rhodesae, cell extracts but no palytoxin-like analogues were found in them. The findings highlight a case of pseudo-cryptic speciation, found in sympatry with closely related and morphologically similar species, but biologically and functionally distinct.     

Allelopathic effects of Alexandrium fundyense (Dinophyceae) on Thalassiosira cf. gravida (Bacillariophyceae): a matter of size

Allelopathic interactions among phytoplankton are well documented. The potency of allelopathic species and responses of target species to allelochemicals are quite variable, however, limiting full understanding of the role these interactions may play in nature. One trait that may influence the sensitivity of an individual to allelochemicals is cell size. The few studies that have examined relationships between cell size and susceptibility to allelochemicals have compared different species and thus could not distinguish between the role of size and species‐specific physiological differences. Culturing an actively sexually reproducing diatom allowed us to focus on the influence of target cell size within a single species. We studied growth and nutrient acquisition by the chain‐forming Thalassiosira cf. gravida Clever in the presence and absence of allelochemicals released by Alexandrium fundyense Balech as a function of T. cf. gravida cell size. Upon exposure to filtrate of A. fundyense, T. cf. gravida cultures “bleached” and both growth and nutrient utilization ceased for up to 4 d. The magnitude of the effect was dependent on filtrate concentration and T. cf. gravida cell surface area:volume ratio. The greatest inhibition was observed on the smallest cells, while T. cf. gravida cultures that had undergone cell enlargement via sexual reproduction were least sensitive to A. fundyense filtrate. These results demonstrate that competitor cell size, independent from taxonomy, may influence the outcome of allelopathic interactions. The findings presented here suggest a potential ecological impact of diatom cell size reduction and sexual reproduction that has not yet been described and that may be important in determining diatom survival and success.     

亚热带人工林松树~(13)C/~(12)C比率和水分利用效率

1 引言 亚热带季风阔叶林自然林被破坏后,代之以人工林,由于自然林郁密的树冠层的消失,引起环境因素明显变化,如太阳辐射的增强,气温变幅变大,同时由于风速增大,加大了蒸腾的需要量,造成空气相对湿度降低和土壤水分亏缺,特别是在干旱季节尤为显著。该林地中除被动适应这一生境的1年生草本外,尚有灌木桃金娘(Rhodomyrtus tomentosa)、三叉苦(Euodia     

Presence of Gymnodinium catenatum (Dinophyceae) in a coastal Mediterranean lagoon

The occurrence and abundance of the toxic, chain-forming dinoflagellateGymnodinium catenatum in a Tyrrhenian coastal lagoon, the Fusaro,during an annual sampling cycle are reported. Peak abundanceswere observed from late spring until early autumn Although veryhigh cell numbers were recorded, up to 1 5 x 10⁶ cells l^–1,no monospecific bloom of this species occurred. The first observationof G.catenatum in the Mediterranean occurred in the Fusaro andthe appearance of this species in a traditional shellfish farmingarea, where no shellfish intoxication has been reported to date,is discussed in relation to human interventions in the basin.In particular, intensive dredging in recent years with resuspensionof bottom sediments may have seeded the water body with cysts.A Gymnodinium n d species, illustrated using scanning electronmicroscopy, caused a monospecific bloom in concomitance withmaximum abundances of G.catenatum, apparently outcompeting thislatter species