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     

Estimations of mesozooplankton biomass in a coastal upwelling area off NW Spain

The abundance and several estimators of mesozooplankton biomass(dry weight, ash-free dry weight, displacement volume, carbonand nitrogen) were measured in a coastal upwelling area offLa Coru*****na (NW Spain) at monthly intervals between 1990and 1995. Holoplanktonic copepods dominated in most of the samples,but meroplanktonwere also important near the coast, especiallyduring late spring and through summer. Gelatinous organisms(medusae, siphonophores and larvaceans) reached significantabundances (-10%) in shelf waters by late summer, but also nearthe coast in spring. Log-linear equations were computed betweendry weight, displacement volumeand the other biomass estimators,to allow for interconversion among different measurements. Toprevent the influence of meroplankton and gelatinous zooplanktonin the estimations of biomass, the equations were adjusted usingonly samples in which the abundance of each of these groupswas <10% of total individuals. Our equations produced carbonand ash-free dry weight estimates that are comparable to thoseobtained with the ratiosgiven in other studies in the region.However, the esti mations of mesozooplankton carbon from displacementvolume using the adjusted equation with our data are lower thanthose reported previously for the area, which werecomputed usingequations adjusted with data from a different ecosystem. Theuse of interconversion factors taken from the literature isdiscussed, along with the implications of the estimations ofmesozooplankton biomass in the computations of the flux of carbonthrough the ecosystem.     

Paralytic shellfish toxin profiles of different geographic populations of Gymnodinium catenatum (Dinophyceae) in Korean coastal waters

Paralytic shellfish poisoning toxin profiles of dinoflagellate cultures of Gymnodinium catenatum Graham from the Yellow and South Seas in Korea were investigated by high performance liquid chromatography fluorometric detection. Strains from the Yellow Sea had predominantly carbamate toxins, while strains from Sujeongri and Chindong in the South Sea contained the N‐sulfocarbamoyl toxins, Cl,2, as major components including the presence of GTX5 and dcSTX in some strains. Toxin profiles from St. Deukryang Bay strains (South Sea) showed both characteristics of those in the South Sea and those in the Yellow Sea. Thirty strains could be divided into three groups based on cluster analysis of toxin compositions. Group I (Yellow Sea strains) was distinguished from Group II (Sujeongri and Chindong strains) by the absence of GTX5 and dcSTX. Group III comprised Deukryang Bay strains. In conclusion, the Yellow Sea and the South Sea were found to have different dinoflagellate populations with different toxin compositions.     

Environmental fungal diversity in the upwelling ecosystem off central Chile and potential contribution to enzymatic hydrolysis of macromolecules in coastal ecotones

Even though occurrence of fungi in several marine environments has been documented, their inclusion within the marine microbial loop is not fully recognized. A major constraint is whether fungi in coastal waters are truly marine or represent transient microorganisms transported from terrestrial environments. We approached this issue by analyzing ambient fungal composition and hydrolytic activity of culturable fungi along a nearshore-offshore gradient in the upwelling ecosystem off central Chile, a region of high marine productivity strongly influenced by river discharges. We detected different communities of fungi in nearshore and offshore waters, with near estuary strains hydrolyzing proteins and carbohydrates faster than those from offshore sites. We conclude that coastal waters off central Chile comprise distinct fungal communities representative of offshore and nearshore environments, and provide new evidence for fungi processing organic matter in coastal ecotones, opening a fresh perspective for disappearance of organics carried by rivers in the coastal ocean.     

Global toxicology,ecophysiology and population relationships of the chainforming PST dinoflagellate Gymnodinium catenatum

Increasing scientific awareness since the 1980s of the chain-forming dinoflagellate Gymnodinium catenatum has led to this species being reported with increased frequency in a globally increasing number of countries (23 at present). G. catenatum exhibits little molecular genetic variation in rDNA over its global range, in contrast to RAPD fingerprinting which points to high genetic variation within regional populations even between estuaries 50 km apart. All Australian and New Zealand strains possess a thymine nucleotide (T-gene) near the start of the 5.8S rRNA whereas all other global populations examined to date possess cytosine-nucleotide (C-gene), except for southern Japan which harbours both C-gene and T-gene strains. Together with cyst and plankton evidence this strongly suggests that both Australian and New Zealand populations have derived from southern Japan. Global dinoflagellate populations and cultures exhibit an extraordinary variation in PST profiles (STX and 21 analogues), but consistent regional patterns are evident with regard to the production of C1,2; C3,4; B1,2; and neoSTX analogues. PST profiles of cyst-derived cultures are deemed unrepresentative. Distinct ecophysiological differences exist between tropical (21–32 °C) and warm-temperate ecotypes (12–18 °C), but these appear unrelated to ITS genotypes and PST toxin phenotypes. On current evidence, cyst germination appears to play a minimal role in the bloom dynamics of this species, while seasonal and inter-annual bloom variations result from the physical constraints (temperature and light) on the growth of the dinoflagellates in the water column. G. catenatum exhibits a capacity to utilize many forms of nitrogen. Its chain formation and strong motility allow it to undergo retrieval migrations to exploit light and nutrient resource gradients in both stratified and mixed environments. Subtle strain-level variations in micronutrient (Se, humics) requirements and interaction with associated bacterial flora may provide a partial explanation for the contrasting inshore (Tasmanian), and offshore (Spain, Mexico) bloom patterns by the same species in different geographic regions.     

Morphology,phylogeny and toxin profiles of Gymnodinium inusitatum sp. nov., Gymnodinium catenatum and Gymnodinium microreticulatum (Dinophyceae) from the Yellow Sea,China

Four Gymnodinium species have previously been reported to produce microreticulate cysts. Worldwide, Gymnodinium catenatum strains are conservative in terms of larger subunit (LSU) rDNA and internal transcribed spacer region (ITS) sequences, but only limited information on the molecular sequences of other species is available. In the present study, we explored the diversity of Gymnodinium by incubating microreticulate cysts collected from the Yellow Sea off China. A total of 18 strains of Gymnodinium, from three species, were established. Two of these were identified as Gymnodinium catenatum and Gymnodinium microreticulatum, and the third was described as a new species, Gymnodinium inusitatum. Motile cells of G. inusitatum are similar to those of Gymnodinium trapeziforme, but they only share 82.52% similarity in LSU sequences. Cysts of G. inusitatum are polygonal in shape, with its microreticulate wall composed of approximately 14 concave sections. G. microreticulatum strains differ from each other at 69 positions (88.00% similarity) in terms of ITS sequences, whereas all G. catenatum strains share identical ITS sequences and belonged to the global populations. Phylogenetic analyses, based on LSU sequences, revealed that Gymnodinium species that produce microreticulate cysts are monophyletic. Nevertheless, the genus as a whole appears to be polyphyletic. Paralytic shellfish toxins (PSTs) were found in all G. catenatum strains tested (dominated by 11-hydroxysulfate benzoate analogs and N-sulfocarmaboyl analogs) but not in any of the G. microreticulatum and G. inusitatum strains. Our results support the premise that cyst morphology is taxonomically informative and is a potential feature for subdividing the genus Gymnodinium.     

Hydrography and phytoplankton of the Ria de Vigo before and during a red tide of Gymnodinium catenatum Graham

At the end of summer 1986, hydrographic data and phytoplanktonsamples were collected on three occasions in the Ríade Vigo. The phytoplankton composition was studied in relationto the hydrography using principal component analysis and canonicalcorrelation analysis. Upwelling and the response of the planktoncommunity emerge as the main source of variation in the analysesWithin this framework, nutrient regeneration was observed, partlyattributable to ciliates and small flagellates. The second sourceof variation of the phytoplankton was the presence in the latersamples of a Gymnodinium catenatum red tide. Two other phytoplanktonpopulations were clearly differentiated One oceanic, dominatedby Erythropsis sp, Ceratium horridum and Stauroneis membranacea,which practically disappeared when the red Ode was established.The other, dominated by Solenicola setigera, dinoflagellatecysts and elongated diatoms, was a permanent population locatedbelow the populations which responded to upwelling. The penetrationof warm oceanic water into the ría during the secondday of observations altered the distributions of all the planktonicpopulations, isolating them in a downwelling zone. The energyof the oceanic intrusion could have been sufficient to removesediments from the interior of the ría and to stimulatethe formation of the red tide, by confining a water body inthe ría which lost little by mixing. It is likely thatthe resuspension of G.catenatum cysts provided the necessaryinoculum.     

Modeling microzooplankton and macrozooplankton dynamics within a coastal upwelling system

A simple nutrient–phytoplankton–zooplankton (NPZ)pelagic ecosystem model coupled to a two-dimensional primitiveequation circulation model with explicit mixed-layer physicsis configured in a coastal setting to study the biological responseto idealized wind-driven upwelling conditions. Conventionalecosystem model parameterization, which assumes macrozooplanktonas the target grazers, leads to upwelling-induced phytoplanktonblooms that exhaust available nutrient supply and whose zonalscale increases with wind duration. Offshore zooplankton maximaresult from upwelled water with greater total nitrogen concentrationsthan initial ambient surface water. Substantial vertical mixingin the surface boundary layer sets the vertical scale of theproductivity. Phytoplankton sinking contributes to a nearshoreaccumulation of total nitrogen, and enhances the magnitude andduration of the phytoplankton bloom. The system responds differentlywhen the zooplankton are parameterized to represent microzooplankton.The phytoplankton and zooplankton maxima have more limited zonalextent, are more independent of the duration of wind forcing,and near-surface nutrient levels remain high over most of thedomain. When winds are relaxed, the diminished offshore transportreveals the underlying biological oscillations in the microzooplankton-parameterizedecosystem, and reduced vertical mixing decouples surface fromsubsurface dynamics. In contrast, the macrozooplankton systemrelaxes to a steady state supporting limited phytoplankton andlarge zooplankton levels in the upwelling region.     

Nanoheterotroph grazing on bacteria and cyanobacteria in oxic and suboxic waters in coastal upwelling areas off northern Chile

The vertical distribution and abundance of microbial assemblagesand the grazing of nanoheterotrophs upon prokaryotes in oxicand suboxic waters were examined in two coastal upwelling areasoff northern Chile where a shallow Oxygen Minimum Zone (OMZ)is characteristic. Prokaryotic prey included bacterioplanktonand cyanobacteria (Synechococcus); both displayed a bimodaldistribution, with abundance maxima above and within the upperOMZ. Flagellates numerically dominated the nanoplankton andwere mostly concentrated in the oxic layer. Mean ingestion ratesof cyanobacteria by nanoflagellates (vacuole content method)ranged from 0.2 to 1.1 cells flagellate^–1 h^–1 andmean consumption rates (34–160 cells mL^–1 h^–1)were four times higher in the oxic layer. With the selectiveinhibitors technique, specific grazing rates on bacteria werelow (<0.1 h^–1) and consumption did not control bacterialproduction in the surface layer but did so in the suboxic layer(accounting for >100% of bacterial production). With thesame method, the specific grazing rate on cyanobacteria rangedbetween zero and 0.23 h^–1 with no clear differences betweenoxygen conditions; prey growth and production were always higherthan the grazing pressure (accounting for <17% of cyanobacterialproduction). The impact of grazing by nanoheterotrophs in regulatingthe production of prokaryotes in oxic and suboxic waters inthis region is discussed.     

Environmental drivers of mussels flesh yield in a coastal upwelling system

Eastern boundary coastal upwelling ecosystems (EBUEs) are highly sensitive to climate variability, particularly to coastal wind change. Here, we test the response of the flesh yield of blue mussels cultured in the northern boundary of the Iberian–Canary current EBUE to climate-related variables. Significant relationships were found between the annual mean, seasonal build-up and phenology of the mussel flesh yield with meteorological variables such as continental runoff, intensity and direction of coastal winds, and solar radiation. Our analysis shows that better flesh yields occur during years characterised by dry winters, accompanied by early springs and followed by summers dominated by strong northerly winds that produce intense upwelling. Compared with other EBUEs, upwelling has weakened in the study area over the last fifty years, implying an overall decrease in mussel flesh yield. However, future climate scenarios suggest that coastal upwelling will intensify over the 21th century, particularly during the summer months, which would lead to a recovery of mussel flesh yield.     

Changes in bacterial populations during red tides caused by Mesodinium rubrum and Gymnodinium catenatum in North West Coast of Spain

Heterotrophic bacterial communities associated with four red tides caused by Mesodinium rubrum and Gymnodinium catenatum in two Galician Rias (North West Spain) were examined. Three of these were produced by the Mesodinium rubrum and the causative organism of a toxic bloom was Gymnodinium catenatum . In early stages of all the blooms, the diversity decreased but the total marine bacterial counts increased by one or two logs. Vibrio numbers were also incremented by two logs in two blooms of M. rubrum , while in the other bloom of this organism and in the red tide caused by G. catenatum a decrease in number of these bacteria was observed. A total of 116 bacterial strains were identified at the genus level and grouped into 12 phena. During the decomposition processes of two blooms of M. rubrum a zooplanktonic-type bacterial succession was observed ( Vibrio , pseudomonads and Moraxella-Acinetobacter ). On the other hand, during decomposition of the other red tide of M. rubrum and the bloom of G. catenatum , a typical phytoplanktonic-type succession occurred, as Pseudomonas and Moraxella groups became dominant for all the process. These results support the conflicting taxonomical position of M. rubrum . After the blooms, the changes in the community point towards the restablishment of the normal bacterial flora of the estuary (increase in diversity and decreases of bacterial numbers). Only the Vibrio strains, isolated from the non-toxic first and second red tides, displayed cytotoxic activities. A relationship among bacterial cytotoxicity and toxic effects of blooms cannot therefore be established.     

Changes in bacterial populations during red tides caused by Mesodinium rubrum and Gymnodinium catenatum in North West Coast of Spain

Heterotrophic bacterial communities associated with four red tides caused by Mesodinium rubrum and Gymnodinium catenatum in two Galician Rias (North West Spain) were examined. Three of these were produced by the Mesodinium rubrum and the causative organism of a toxic bloom was Gymnodinium catenatum. In early stages of all the blooms, the diversity decreased but the total marine bacterial counts increased by one or two logs. Vibrio numbers were also incremented by two logs in two blooms of M. rubrum, while in the other bloom of this organism and in the red tide caused by G. catenatum a decrease in number of these bacteria was observed. A total of 116 bacterial strains were identified at the genus level and grouped into 12 phena. During the decomposition processes of two blooms of M. rubrum a zooplanktonic-type bacterial succession was observed (Vibrio, pseudomonads and Moraxella-Acinetobacter). On the other hand, during decomposition of the other red tide of M. rubrum and the bloom of G. catenatum, a typical phytoplanktonic-type succession occurred, as Pseudomonas and Moraxella groups became dominant for all the process. These results support the conflicting taxonomical position of M. rubrum. After the blooms, the changes in the community point towards the restablishment of the normal bacterial flora of the estuary (increase in diversity and decreases of bacterial numbers). Only the Vibrio strains, isolated from the non-toxic first and second red tides, displayed cytotoxic activities. A relationship among bacterial cytotoxicity and toxic effects of blooms cannot therefore be established.     

The effects of temperature, growth medium and darkness on excystment and growth of the toxic dinoflagellate Gymnodinium catenatum from northwest Spain

The chain-forming dinoflagellate Gynmodinium catenatum Grahamcauses recurrent outbreaks of paralytic shellfish poisoning(PSP) in the Galician Rias Bajas (northwest Spain). A sedimentsurvey in Ria de Vigo in April 1986 indicated that the highestconcentrations of cysts of this species were located in themiddle sections of the ria, with maximum abundance of 310 cystscm^–3. The effects of temperature, growth medium compositionand irradiance on the germination of laboratory-produced restingcysts were investigated. Newly formed cysts required very littletime for maturation, as excystment was possible within 2 weeksof encystment. Growth media did not affect germination success.In contrast, the excystment rate was retarded signifiantly indarkness. Germination was also strongly affected by temperature,with {small tilde}75% excystment success at 22–28°Cand little or no germination below 11°C after 1 month ofincubation. In culture, the optimum growth rate of vegetativecells was between 22 and 28°C, the highest rate being 0.53divisions day^–1 at 24°C. Growth did not occur at temperatures< 11°C or >30°C. These results are important withrespect to the different hypotheses proposed to explain theinitiation of G.catenatum blooms in the Galician Rias Bajasand Northern Portugal. The pattern of G.catenatum bloom developmentalong this coast has been related to seasonal upwelling in thearea, with major blooms occurring during the autumn as warmeroffshore surface water is transported towards the coast whenupwelling relaxes. The landward transport of established offshorepopulations of G.catenatum with the warm surface layer remainsa viable explanation for the observed blooms within the rias,but alternatively, our data suggest that cysts within the riascan provide the inoculum population at times conducive to growthand bloom formation. Even though newly formed G.catenatum cystshave a very short maturation time and can germinate in darknessacross a wide temperature range, bloom development will be significantonly during the late summer and early autumn, since in othermonths light levels at the sediment surface and temperaturesthroughout the water column are too low for significant germinationor growth.     

海南岛西北沿岸海域浮游桡足类的分布及群落特征

为了解昌江沿岸海域生态系统的现状, 探讨海域环境因素对浮游动物的生存环境造成的影响。本文根据2008年11月至2009年7月在海南西部昌江沿岸水域21个测站、4个季度月调查所获的浮游桡足类样品数据, 对该海域浮游桡足类群落结构、分布、季节变化及影响因素进行了分析。本调查共鉴定出桡足类44种, 隶属4目17科24属, 其中秋季25种, 冬季23种, 春季22种, 夏季23种。本次调查共发现优势种6种, 分别是微刺哲水蚤(Canthocalanus pauper)、亚强次真哲水蚤(Subeucalanus subcrassus)、锥形宽水蚤(Temora turbinata)、刺尾纺锤水蚤(Acartia spinicauda)、椭形长足水蚤(Calanopia elliptica)和精致真刺水蚤(Euchaeta concinna), 优势种以近岸暖水种居多。浮游桡足类丰度季节变化明显: 冬季最高, 达409 ind./m³; 秋季次之, 为144 ind./m³, 春季为55 ind./m³, 夏季最低仅为17 ind./m³。其丰度的平面分布显示: 秋、冬季节分别在海区中部和南部形成明显密集区, 春、夏季节则大致呈现由外海向近岸逐渐递减的趋势。浮游桡足类的多样性指数(H')表现为夏季>春季>秋季>冬季, 春、夏季的均匀度指数(J')明显高于秋、冬季。本调查反映出该海区的桡足类群落具有热带—亚热带区系特征, 种类组成季节更替明显, 桡足类种群受海域水温和硅藻的影响明显, 受盐度影响不明显。     

Biological activity in the wake of an island close to a coastal upwelling

Hydrodynamic forcing plays an important role in shaping the dynamics of marine organisms, in particular of plankton. In this work we study the planktonic biological activity in the wake of an island which is close to an upwelling region. Our research is based on numerical analysis of a kinematic flow mimicking the hydrodynamics in the wake, coupled to a three-component plankton model.We use parameter values relevant for the Canary wake, and the main results for a realistic range of parameters in this area are as follows: (a) Primary production is enhanced in the region of the wake opposite to the upwelling zone. (b) There is a strong dependence of the productivity on the inflow conditions of biological material entering the wake transported by the main current. Finally (c) we show that under certain conditions the interplay between wake structures and biological growth leads to plankton blooms inside mesoscale hydrodynamic vortices that act as incubators of primary production.     

Distribution of freshwater macroinvertebrates in streams with dams and associated reservoirs on a subtropical oceanic island off southern Japan

The conservation of endemic fauna in freshwater ecosystems is a topical issue on small oceanic islands. Because these endemics have limited distributions, they are more vulnerable to extinction. This study is the first to clarify the distribution of freshwater macroinvertebrates including endemic and alien species in streams with dams and associated reservoirs on the Ogasawara Islands in the northwestern Pacific Ocean. In 2007, we conducted a field survey in streams and reservoirs of the Yatsuse River system and collected 22 taxonomic groups from 13 stations. Hierarchal cluster analysis and non-metric multi-dimensional scaling (NMDS) were performed for the presence/absence data of the macroinvertebrates, and the results indicated that (1) most of endemic species were present in inlet streams of dam reservoirs, (2) these endemic species were absent in the bottom sediments of the reservoirs because of oxygen depletion and (3) dams may be barriers to the migration of some species of amphidromous crustaceans. Because human modifications, such as dams and associated reservoirs, on a small oceanic island can rapidly result in fragmentation or loss of freshwater habitats of endemic species, the remaining habitat of these species, such as headwater streams, must be protected and preserved to avoid species extinction.     

Toxin and molecular analysis of Gymnodinium catenatum (Dinophyceae) strains from Galicia (NW Spain) and Andalucia (S Spain)

Nineteen strains of Gymnodinium catenatum were isolated fromone bloom in Andalucía (S Spain) and from different bloomsin Galicia (NW Spain). The PSP toxin profiles of 16 of the strainswere analyzed, and although the saxitoxin was exclusive to theGalician strains, the corresponding dendogram showed no clusteringof the isolates from this location. However, nine out of elevenAndalusian strains were included in the same cluster. In orderto compare toxin with molecular analysis, a fragment of thelarge subunit ribosomal (LSU) RNA gene was partially sequencedfor all of the strains and fully sequenced for the five strainsthat had shown most different growth curves. Since all the strainswere identical in the LSU sequenced region, another fragmentcomprising the internal transcribed spacer 1 (ITS 1), 5.8S rRNAgene and ITS 2, was sequenced and compared among all the strains.Although this region has been used before for the detectionof intraspecific variability, it was similar in all our strains.Finally, to detect molecular differences in the strains, a randomamplified polymorphic DNA (RAPD) analysis was performed. Thecorresponding cluster analysis grouped the strains in threeclusters: one of them comprised all the Galician strains plusthree from Andalucía, another one included eight Andalusianstrains, and the last one, more separated from the two previous,was constituted by two Andalucía isolates. Although theresults of the toxin and RAPD analysis were different, sevenAndalusian strains were clustered together in both dendograms.Since neither the toxin nor the RAPD analysis brought out aclear geographic signal, we can conclude that differences intoxin content and RAPD profile between the isolates of G. catenatumare probably not linked to the location in which the strainswere collected.     

Effects of the toxic dinoflagellate, Gymnodinium catenatum on hydrolytic and antioxidant enzymes, in tissues of the giant lions-paw scallop Nodipecten subnodosus

This study documents effects of the toxic dinoflagellate Gymnodinium catenatum, a producer of paralytic shellfish poison, on juvenile farmed (5.9+/-0.39 cm) giant lions-paw scallop Nodipecten subnodosus. Scallops were fed bloom concentrations of toxic dinoflagellate G. catenatum for 7 h. The effect of the toxic dinoflagellate in different tissues was determined by analysis of antioxidant enzymes (catalase, superoxide dismutase, gluthathione peroxidase), thiobarbituric acid reactive substances (lipid peroxidation), and hydrolytic enzymes (proteases, glycosidases, phosphatases, lipases, and esterases). Histopathological photos record the effects of the toxic dinoflagellate in various tissues. The results show that juvenile lions-paw scallops produce pseudo-feces, partially close their shell, increase melanization, and aggregate hemocytes. Several enzymes were affected and could serve as biological markers. In general, the adductor muscle was not affected. In the digestive gland, some enzymes could be the result of defensive and digestive processes. Gills and mantle tissue were markedly affected because these sites respond first to toxic dinoflagellates, leading to the idea that proteolytic cascades could be involved.