Development of microsatellite markers for the red tide‐forming harmful species Chattonella antiqua,C. marina,and C. ovata (Raphidophyceae)

We have developed 11 microsatellite markers that are specific to Chattonella antiqua, C. marina, and C. ovata, the red tide‐forming harmful phytoplanktons. The 11 loci were amplified in the three species. The number of alleles per locus ranged from 5 to 16. The three species shared most microsatellite regions, although the genetic differences in specific loci were detected among them. These markers of the Chattonella species will be beneficial for biogeographical, detailed taxonomic, studies.     

Relationships between dynamics of red tide-causing raphidophycean flagellates and algicidal micro-organisms in the coastal sea of Japan

Temporal fluctuations of algicidal micro-organisms against the red tide causing raphidophycean flagellates Chattonella antiqua (Hada) Ono and Heterosigma akashiwo (Hada) Hada ex Hara et Chihara were investigated using the microplate most probable number (MPN) method in northern Hiroshima Bay and Harima-Nada, the Seto Inland Sea, in 1992 and 1993. In Har-ima-Nada, both flagellates appeared at low levels (< 1 cell mL^?1), and killer micro-organisms against the two flagellates (C-killer for C. antiqua and H-killer for H. akashiwo) also appeared at low densities (< 2 mL^?1). In northern Hiroshima Bay, C. antiqua cells were scarce (< 1 cell mL^?1), and C-killers occurred at a low level (≤ 3.4 mL^?1). Conversely, red tides of H. akashiwo occurred there in June of both years. The dynamics of H-killers revealed a close relationship with that of H. akashiwo populations. H-killers followed the increase of H. akashiwo cells, reached a maximum level after the beginning of decline of H. akashiwo, maintained a high level for at least 1 week after the crash of bloom, and then decreased. C-killers consistently remained at low densities during the period of H. akashiwo red tides in both 1992 and 1993. Hence, algicidal micro-organisms specifically associated with the occurrence and crash of H. akashiwo red tides, and presumably contributed to the rapid termination of the red tides in the coastal seas such as northern Hiroshima Bay.     

ALGICIDAL BACTERIA ACTIVE AGAINST GYMNODINIUM BREVE (DINOPHYCEAE). I. BACTERIAL ISOLATION AND CHARACTERIZATION OF KILLING ACTIVITY1,3

Interactions between bacteria and species of harmful and/or toxic algae are potentially important factors affecting both the population dynamics and the toxicity of these algae. Recent reports of bacteria lethal to certain harmful algal bloom (HAB) species, coupled with a rapidly evolving interest in attempting to minimize the adverse effects of HABs through various prevention, control, and mitigation strategies, have focused attention on defining the role of algicidal bacteria in bloom termination. The aim of the present study was to determine whether algicidal bacteria active against Gymnodinium breve Davis, a dinoflagellate responsible for frequent and protracted red tides in the Gulf of Mexico, are present in the waters of the west Florida shelf. To date, we have isolated two bacterial strains from this region lethal to G. breve and have begun to characterize the algicidal activity of one of these strains, 41-DBG2. This bacterium, a yellow-pigmented, gram-negative rod, was isolated from waters containing no detectable G. breve cells, suggesting that such bacteria are part of the ambient microbial community and are not restricted to areas of high G. breve abundance. Strain 41-DBG2 produced a dissolved algicidal compound(s) that was released into the growth medium, and the algicide was effective against the four Gulf of Mexico G. breve isolates tested as well as a closely related HAB species that also occurs in this region, Gymnodinium mikimotoi Miyake et Kominami ex Oda. Nonetheless, data showing that a nontoxic isolate of Gymnodinium sanguineum Hirasaka from Florida Bay was not affected indicate that the algicidal activity of this bacterium does exhibit a degree of taxonomic specificity. Our efforts are currently being directed at resolving several critical issues, including the identity of the algicide(s), the mechanisms regulating its production and ability to discriminate between target algal species, and how the growth rate of 41-DBG2 is affected by the presence of G. breve cells. We have also proposed a conceptual model for interactions between algicidal bacteria and their target species to serve as a testable framework for ensuing field studies.     

Feeding by the newly described, nematocyst-bearing heterotrophic dinoflagellate Gyrodiniellum shiwhaense

We explored the feeding ecology of the newly described, nematocyst-bearing heterotrophic dinoflagellate Gyrodiniellum shiwhaense (GenBank accession number=FR720082). Using several different types of microscopes and high-resolution video-microscopy, we investigated feeding behavior and types of prey species that G. shiwhaense feeds upon. Additionally, we measured its growth and ingestion rates on its optimal algal prey, the cryptophyte Teleaulax sp. and the dinoflagellate Amphidinium carterae, as a function of prey concentration. These rates were measured for other edible prey at single prey concentrations at which the growth and ingestion rates of G. shiwhaense were saturated. After anchoring the prey with a tow filament, G. shiwhaense fed using a peduncle, ingesting small algal species with equivalent spherical diameters (ESDs) of <13 μm. However, it did not feed on larger algal species that had ESDs≥13 μm or the small diatom Skeletonema costatum. The specific growth rates for G. shiwhaense feeding upon Teleaulax sp. and A. carterae increased rapidly with increasing mean prey concentration before saturating at concentrations of ca. 180-430 ng C/ml. The maximum specific growth rate of G. shiwhaense on Teleaulax sp. and A. carterae were 1.05 and 0.82/d, respectively. However, Heterosigma akashiwo did not support positive growth of G. shiwhaense. The maximum ingestion rates of G. shiwhaense on Teleaulax sp. and A. carterae were 0.35 and 0.54 ng C/grazer/d, respectively. The calculated grazing coefficients attributable to G. shiwhaense on co-occurring cryptophytes and Amphidinium spp. were 0.01-1.87/d and 0.08-2.60/d, respectively. Our results suggest that G. shiwhaense can have a considerable grazing impact on algal populations.     

Feeding by the Pfiesteria-like heterotrophic dinoflagellate Luciella masanensis

To explore the feeding ecology of the Pfiesteria-like dinoflagellate (PLD) Luciella masanensis (GenBank Accession no. AM050344, previously Lucy), we investigated the feeding behavior and the kinds of prey species that L. masanensis fed on and determined its growth and ingestion rates of L. masanensis when it fed on the dinoflagellate Amphidinium carterae and an unidentified cryptophyte species (equivalent spherical diam., ESD=5.6 microm), which were the dominant phototrophic species when L. masanensis and similar small heterotrophic dinoflagellates were abundant in Masan Bay, Korea in 2005. Additionally, these parameters were also measured for L. masanensis fed on blood cells of the perch Lateolabrax japonicus and the raphidophyte Heterosigma akashiwo in the laboratory. Luciella masanensis fed on prey cells by using a peduncle after anchoring the prey with tow filament, and was able to feed on diverse prey such as cryptophytes, raphidophytes, diatoms, mixotrophic dinoflagellates, and the blood cells of fish and humans. Among the prey species tested in the present study, perch blood cells were observed to be the optimal prey for L. masanensis. Specific growth rates of L. masanensis feeding on perch blood cells, A. carterae, H. akashiwo, and the cryptophyte, either increased continuously or became saturated with increasing the mean prey concentration. The maximum specific growth rate of L. masanensis feeding on perch blood cells (1.46/day) was much greater than that of A. carterae (0.59/day), the cryptophyte (0.24/day), or H. akashiwo (0.20/day). The maximum ingestion rate of L. masanensis on perch blood cells (2.6 ng C/grazer/day) was also much higher than that of A. carterae (0.32 ng C/grazer/day), the cryptophyte (0.44 ng C/grazer/day), or H. akashiwo (0.16 ng C/grazer/day). The kinds of prey species which L. masanensis is able to feed on were the same as those of Pfiesteria piscicida, but very different from those of another PLD Stoeckeria algicida. However, the maximum growth and ingestion rates of L. masanensis on perch blood cells, A. carterae, H. akashiwo, and the cryptophyte were considerably lower than those of P. piscicida. Therefore, these three dinoflagellates may occupy different ecological niches in marine planktonic communities, even though they have a similar size and shape and the same feeding mechanisms.     

Response of growth and photosynthesis of marine red tide alga Heterosigma akashiwo to iron and iron stress condition

Heterosigma akashiwo, a red tide alga, was grown in Fe-deficient and Fe-replete batch cultures. Cell final yields and the growth rate were limited when Fe was below 10 nM and alleviated with 100 nM Fe. By comparison with the results under Fe-replete conditions, chlorophyll a-specific and cell-specific light saturated net photosynthetic capacity (P_m ^{chl a} and P_m ^cell), dark respiration rate (R_d ^{chl a} and R_d ^cell) and apparent photosynthetic efficiency (^{chl a} and ^cell) decreased proportionately, whereas the cells became light saturated at higher irradiance under Fe stress (Fe-limited conditions).     

中国赤潮的发生趋势和研究进展

通过对中国沿海赤潮发生历史的回顾以及主要赤潮事件的分析,阐明了中国沿海赤潮发生所呈现的趋势,即频率增加,规模扩大,新的赤潮藻种不断出现,有毒赤潮种比例上升,以及有害赤潮危害程度日益增加,且初步分析了赤潮频发的内因和外因,综述了我国科学家在赤潮生消过程监测,赤潮灌的培养生物学和分类学,赤潮藻类的营养动力学及生理生态学特性,赤潮藻类的生活史,赤潮藻类毒素,赤潮的模型和赤潮防治及国际合作等方面工作的进展,指出了研究还存在的不足之处,并对未来赤潮研究和管理提出了建议。     

Occurrence of the polyamines caldopentamine and homocaldopentamine in axenic cultures of the red tide flagellates Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae)

The polyamines caldopentamine and homocaldopentamine were detected in axenic strains of Chattonella antiqua and Heterosigma akashiwo ( Raphidophyceae ), respectively, as well as spermidine, the most abundant polyamine in both phytoplankton species. Trace amounts of putrescine, diaminopropane and norspermine were also detected in both species. Spermine was detected only from C. antiqua . These long linear polyamines are characteristic components of thermophilic bacteria. The detection from two species of Raphidophyceae indicates that the occurrence of long linear polyamines is not restricted to thermophilic microorganisms.     

Epiphytes on the rocky intertidal red alga RhodomelaLarix (Turner) C. Agardh: Negative effects on the host and food for herbivores?

The diversity of epiflora and fauna associated with a dominant turf-forming alga was examined in intertidal communities on the central Oregon coast. Epiphytes associated with the red alga, Rhodomelalarix (Turner) C. Agardh, were examined by surveying intertidal areas for the presence of epiphytes, and by following changes in epiphyte cover in marked quadrats of R. larix. The alga is host for at least 17 species of sessile plants and animals. To determine the role of some of the larger epiphytes in the community, Rhodomela plants were marked and monitored and herbivore feeding was examined. Data suggest that epiphytes decrease the growth rate of their host, increase the probability of axis breakage and decrease reproductive output. Epiphytes provide food for littorine snails and gammarid amphipods that live in the beds of the plant. Amphipods were found to decrease epiphyte cover on R. larix in laboratory tanks, suggesting that these herbivores may have beneficial effects on the host plant.     

Extracellular organic compounds from the ichthyotoxic red tide alga Heterosigma akashiwo elevate cytosolic calcium and induce apoptosis in Sf9 cells

Toxin(s) from the ichthyotoxic red tide alga Heterosigma akashiwo have been responsible for the destruction of millions of dollars of finfish aquaculture around the globe. Mechanisms of toxicity may include the production of reactive oxygen species (ROS) or organic toxins. The purpose of this study was to investigate the bioactivity of extracellular organic compounds from cultures of H. akashiwo. Cytosolic free calcium levels ([Ca²⁺]_i) in Spodoptera frugiperda (Sf9) insect cells infected with baculoviruses encoding the M1 muscarinic receptor were monitored.Exposure of cells to Heterosigma organics increased [Ca²⁺]_i up to 120 nM above basal levels (two-fold increase). Within minutes following exposure of the cells to the organics, the increase in [Ca²⁺]_i peaked and was followed by a slightly reduced, yet sustained plateau. This plateau was maintained for the duration of an experiment (>15 min) and was inhibitable by lanthanum. Furthermore, stimulation of Ca²⁺ release from intracellular stores by carbachol (muscarinic agonist) or thapsigargin (sarco-endoplasmic reticulum Ca²⁺-ATPases, SERCA inhibitor) potentiated the [Ca²⁺]_i response induced by the organics resulting in a maximal increase of >250 nM above basal levels (three-fold increase). However, the [Ca²⁺]_i response to Heterosigma organics was strictly dependent on the presence of extracellular calcium. Flow cytometric analyses revealed that these organics induced apoptosis of these same cells. Collectively, our data indicate that extracellular organics from cultures of H. akashiwo acutely increase [Ca²⁺]_i in cells by inhibiting the plasma membrane Ca²⁺-ATPase transporter and ultimately induce apoptotic cell death. These organics may play a significant role in the ichthyotoxic and allelopathic behaviour of this alga.     

Preliminary studies on eutrophication and red tide problems in Bohai Bay

A study was carried out in 1978–1981 on the relationship between eutrophication and the occurrence of red tides in Bohai Bay.An assessment method using a single parameter as well as the multiparameter Trophic State Index was adopted. DIN, DIP, COD loadings and concentrations and phytoplankton community (species composition, diversity index, standing crop, chlorophyll a and primary productivity) were used as parameters. The western part of the bay and two sewage outfall sites showed the highest values of chlorophyll a, nitrate, phosphate, standing crop, primary productivity and the greatest population instability. Therefore, Bohai Bay, can be regarded as mesotrophic, but its estuary eutrophic. Anthropogenic factors are mainly responsible for its eutrophication. A relationship between environmental factors and red tide species was found. Noctiluca miliaris, Prorocentrum minimum and Skeletonema costatum have their bloom periods from July to September and are the most significant species.     

Seasonal variation in the interactions between piscivorous fish,planktivorous fish and zooplankton in a shallow eutrophic lake

The interactions between the higher trophic levels in a shallow eutrophic lake were studied during the course of a year. Three fish species determined the main pathways of organic matter flow within the system: the predominantly planktivorous bream (Abramis brama), the obligate planktivorous smelt (Osmerus eperlanus), and the piscivorous pikeperch (Stizostedion lucioperca). Of the thirteen common zooplankton taxa Daphnia hyalina and cyclopoid copepods were utilized most by the planktivorous fish, while the large production of small cladocerans is almost left unutilized.The seasonal variations of production and consumption are large. This is mainly affected by seasonal variation of the water temperature. The production of O + smelt is efficiently utilized by the pikeperch. Being the most important zooplankton consumer, as well as the most important prey group, O + fish plays a key role in the Tjeukemeer food web.     

Algicidal activity of the seaweed Corallina pilulifera against red tide microalgae

Extracts of seaweeds from the coast of Korea have been tested in vitro for algicidal activity against the growth of the toxic microalga Cochlodinium polykrikoides. Blooms of C. polykrikoides and the ensuing mass mortalities of farmed fish and shellfish are an escalating and worrisome trend. Cell growth of C. polykrikoides was inhibited by the addition to the culture medium of several seaweed extracts. Inhibition of growth resulted from methanol-soluble extracts of the seaweeds Corallina pilulifera, Ulva pertusa, Ishige foliacea and Endarachne binghamiae. Growth inhibition also resulted from the water-soluble extract of C. pilulifera. Powder and dry tissue from the seaweed C. pilulifera also inhibited cell growth of C. polykrikoides. The active algicidal products of C. pilulifera showed stable activity when boiled, exposed to light, or when treated under alkaline condition. Corallina pilulifera had no regional and seasonal variations in this algicidal activity. A powder of the seaweed C. pilulifera, the most potent species, showed algicidal activity against several red tide microalgae, especially C. polykrikoides, Gymnodiniummikimotoi, G. sanguineum, Heterosigma akashiwo, Prorocentrum triestinum and Pyraminonas sp. This revised version was published online in August 2006 with corrections to the Cover Date.