Feeding by the heterotrophic dinoflagellate Oxyrrhis marina on the red-tide raphidophyte Heterosigma akashiwo: a potential biological method to control red tides using mass-cultured grazers

As part of the development of a method to control the outbreak and persistence of red tides using mass-cultured heterotrophic protist grazers, we measured the growth and ingestion rates of cultured Oxyrrhis marina (a heterotrophic dinoflagellate) on cultured Heterosigma akashiwo (a raphidophyte) in bottles in the laboratory and in mesocosms (ca. 60 liter) in nature, and those of the cultured grazer on natural populations of the red-tide organism in mesocosms set up in nature. In the bottle incubation, specific growth rates of O. marina increased rapidly with increasing concentration of cultured prey up to ca. 950 ng C ml(-1) (equivalent to 9,500 cells ml(-1)), but were saturated at higher concentrations. Maximum specific growth rate (mumax), KGR (prey concentration sustaining 0.5 mumax) and threshold prey concentration of O. marina on H. akashiwo were 1.43 d(-1), 104 ng C ml(-1), and 8.0 ng C ml(-1), respectively. Maximum ingestion and clearance rates of O. marina were 1.27 ng C grazer(-1) d(-1) and 0.3 microl grazer(-1) h(-1), respectively. Cultured O. marina grew well effectively reducing cultured and natural populations of H. akashiwo down to a very low concentration within 3 d in the mesocosms. The growth and ingestion rates of cultured O. marina on natural populations of H. akashiwo in the mesocosms were 39% and 40%, respectively, of those calculated based on the results from the bottle incubation in the laboratory, while growth and ingestion rates of cultured O. marina on cultured H. akashiwo in the mesocosms were 55% and 36%, respectively. Calculated grazing impact by O. marina on natural populations of H. akashiwo suggests that O. marina cultured on a large scale could be used for controlling red tides by H. akashiwo near aquaculture farms that are located in small ponds, lagoons, semi-enclosed bays, and large land-aqua tanks to which fresh seawater should be frequently supplied.     

Streptomyces neyagawaensis as a control for the hazardous biomass of Microcystis aeruginosa (Cyanobacteria) in eutrophic freshwaters

An aquatic bacterium capable of eliminating the cyanobacterium Microcystis aeruginosa was isolated from the sediment of an eutrophic lake (Lake Juam, Korea). On the basis of 16S rDNA sequences and biochemical and morphological characteristics, the isolate was determined to be Streptomyces neyagawaensis. It grew optimally at 40 °C and pH 7. In the presence of this bacterium, the biomass of cyanobacterium M. aeruginosa NIES-298 was strongly suppressed, by up to 84.5% in abundance compared to the control. The antialgal activity of S. neyagawaensis depended on the growth phase of the cyanobacterium, but not of the antialgal bacterium. The antialgal activity of S. neyagawaensis was effective against a wide range of algae, including the green alga Chlorella sp., the diatoms Aulacoseira granulata and Stephanodiscus hantzschii, and four cyanobacteria, M. aeruginosa NIES-44, Anabaena cylindrica, Anabaena flos-aquae, and Oscillatoria sancta. S. neyagawaensis indirectly attacked M. aeruginosa by secretion of extracellular antialgal substances that were localized in the bacterial periplasm and had a specific activity of 7.7 U/μg. These results suggest that indigenous bacteria isolated from sediments may have potential application in controlling harmful cyanobacterial blooms in freshwaters.     

Microginin FR1, a linear peptide from a water bloom of Microcystis species

A so far unknown structural variant, called microginin FR1, of cyanobacterial peptides of the microginin type was isolated from a water bloom of a German lake. The bloom consisted almost exclusively of Microcystis sp. cells. The structure of microginin FR1 was identified by amino acid analysis, determination of the relative molecular mass by electrospray mass spectrometry, and by NMR to be a linear pentapeptide with a relative molecular mass of 727 which contains a β-amino-α-hydroxy-decanoic acid (Ahda), alanine, N-methyl-leucine, and two tyrosine units (Ahda-Ala-N-Me-Leu-Tyr-Tyr). Microginin FR1 had angiotensin-converting enzyme inhibitory activity with half-maximal inhibition at 6×10⁻⁵ M microginin FR1.     

Resolving the complex relationship between harmful algal blooms and environmental factors in the coastal waters adjacent to the Changjiang River estuary

The sea area adjacent to the Changjiang River estuary is the most notable region for harmful algal blooms (HABs¹) in China as both diatom and dinoflagellate blooms have been recorded in this region. Affected by the Changjiang diluted water (CDW²) and currents from the open ocean (i.e., Taiwan warm current, TWC³), the environmental conditions in the coastal waters adjacent to the Changjiang River estuary are quite complex. To obtain a better understanding of the mechanisms of HABs in this region, analyses based on field investigation data collected by the National Basic Research Priority Program (CEOHAB I⁴) were performed using principle component analysis (PCA⁵), multiple regression analysis (MRA⁶) and path analysis (PA⁷). The results suggested that phosphate and silicate are the major factors that directly affect the diatom bloom, while dissolved inorganic nitrogen (DIN⁸), temperature and turbidity are the factors that influence the dinoflagellate bloom. CDW and the TWC have different roles in affecting the two types of algal blooms. CDW, which has a high concentration of nitrate and silicate, is essential for the diatom bloom, while the intrusion of the TWC (mainly Kuroshio subsurface water that is rich in phosphate at the bottom) is critical for the maintenance of the dinoflagellate bloom. The results of this study offer a better understanding of the mechanisms of HABs in the East China Sea.     

A survey of Dinophysis spp. and their potential to cause diarrhetic shellfish poisoning in coastal waters of the United States

Multiple species of the genus Dinophysis produce diarrhetic shellfish toxins (okadaic acid and Dinophysis toxins, OA/DTXs analogs) and/or pectenotoxins (PTXs). Only since 2008 have DSP events (illnesses and/or shellfish harvesting closures) become recognized as a threat to human health in the United States. This study characterized 20 strains representing five species of Dinophysis spp. isolated from three US coastal regions that have experienced DSP events: the Northeast/Mid-Atlantic, the Gulf of Mexico, and the Pacific Northwest. Using a combination of morphometric and DNA-based evidence, seven Northeast/Mid-Atlantic isolates and four Pacific Northwest isolates were classified as D. acuminata, a total of four isolates from two coasts were classified as D. norvegica, two isolates from the Pacific Northwest coast were identified as D. fortii, and three isolates from the Gulf of Mexico were identified as D. ovum and D. caudata. Toxin profiles of D. acuminata and D. norvegica varied by their geographical origin within the United States. Cross-regional comparison of toxin profiles was not possible with the other three species; however, within each region, distinct species-conserved profiles for isolates of D. fortii, D. ovum, and D. caudata were observed. Historical and recent data from various State and Tribal monitoring programs were compiled and compared, including maximum recorded cell abundances of Dinophysis spp., maximum concentrations of OA/DTXs recorded in commercial shellfish species, and durations of harvesting closures, to provide perspective regarding potential for DSP impacts to regional public health and shellfish industry.     

EFFECTS OF WATER VELOCITY ON THE ARCHITECTURE AND EPIPHYTES OF CLADOPHORA GLOMERATA (CHLOROPHYTA)1

The architecture of the filamentous green alga Cladophora glomerata (L.) Kütz. and the composition of this alga's epiphytes [primarily the diatoms Epithemia turgida (Ehrenb.) Kütz., Epithemia sorex Kütz., and Cocconeis pediculus Ehrenb.] were examined in different velocity regimes. After transferring algal-bearing cobbles among velocities, the effects of changes in velocity were also examined. Cladophora branching pattern did not initially differ among slow, medium, and fast velocities, indicating that stable water velocities did not affect branching pattern. Two weeks after cobble transfer, Cladophora in fast velocity had fragmented more (i.e. had fewer filaments and fewer branch points per length of filament and had a higher percentage of unbranched filaments) than Cladophora in slow velocity. Fragmentation was greatest in tufts moved from slow velocity, suggesting velocity-associated differences in susceptibility to breakage. Epiphytic assemblage composition differed among slow, medium, and fast velocities and between locations on the filament (base and apex). Cocconeis pediculus dominated where exposure to high velocity was greater (filament apices in medium and fast velocities), whereas the Epithemia spp. dominated where lower velocities occurred (filament bases in all velocities and apices in slow velocity). Two weeks after the cobble transfer, the translocated diatom assemblages had changed and the original pattern of diatom distribution was restored.     

Sorption of Methylene Blue by an Oscillatoria sp.–Dominated Cyanobacterial Mat

The ability of an Oscillatoria sp.–dominated cyanobacterial mat in sorbing methylene blue (MB), a cationic dye, was investigated using the batch contact method. The sorption of MB onto the powdered biomass was not significantly influenced by initial pH (2–10) and temperature (5–45°C) of the solution. MB sorption occurred slowly, requiring 1–8 h for the establishment of equilibrium. A slow attainment of equilibrium seems to be related with the large size of MB ions. The isotherm data of MB sorption by the mat biomass could effectively fit to Langmuir and Freundlich models. The maximum MB sorption capacity (q _max) of the test biomass was 78.43 mg g^?1, which changed little with variation in biomass concentration. Moreover, the test biomass could efficiently sorb MB from solution in presence of Na⁺, K⁺, and Ca²⁺, which usually occur at high concentrations in natural waters, and also in presence of Cd²⁺. These particular characteristics together with pH and temperature independence of the sorption process make the mat biomass an ideal MB sorbent.     

滇池优势水华蓝藻微囊藻的环肽成分

从滇池优势水华蓝藻微囊藻的干藻粉中分离出一环肽化合物,经光谱数据分析鉴定为Anabeanopeptin F（1）,其结构为cyclo（Phe-MeAla-Hty-Ile—Lys）-NH—CO—NH—Arg。     

Feeding by Heterotrophic Dinoflagellates and Ciliates on the Free‐living Dinoflagellate Symbiodinium sp. (Clade E)

To investigate heterotrophic protists grazing on Symbiodinium sp., we tested whether the common heterotrophic dinoflagellates Gyrodinium dominans, Gyrodinium moestrupii, Gyrodinium spirale, Oblea rotundata, Oxyrrhis marina, and Polykrikos kofoidii and the ciliates Balanion sp. and Parastrombidinopsis sp. preyed on the free‐living dinoflagellate Symbiodinium sp. (clade E). We measured the growth and ingestion rates of O. marina and G. dominans on Symbiodinium sp. as a function of prey concentration. Furthermore, we compared the results to those obtained for other algal prey species. In addition, we measured the growth and ingestion rates of other predators at single prey concentrations at which these rates of O. marina and G. dominans were saturated. All predators tested in the present study, except Balanion sp., preyed on Symbiodinium sp. The specific growth rates of O. marina and G. dominans on Symbiodinium sp. increased rapidly with increasing mean prey concentration < ca. 740–815 ng C/ml (7,400–8,150 cells/ml), but became saturated at higher concentrations. The maximum growth rates of O. marina and G. dominans on Symbiodinium sp. (0.87 and 0.61/d) were much higher than those of G. moestrupii and P. kofoidii (0.11 and 0.04/d). Symbiodinium sp. did not support positive growth of G. spirale, O. rotundata, and Parastrombidinopsis sp. However, the maximum ingestion rates of P. kofoidii and Parastrombidinopsis sp. (6.7–10.0 ng C/predator/d) were much higher than those of O. marina and G. dominans on Symbiodinium sp. (1.9–2.1 ng C/predator/d). The results of the present study suggest that Symbiodinium sp. may increase or maintain the populations of some predators.     

The use of benzyladenine in orchard fruit growing: a mini review.

Plant growth regulators (PGRs) can be well integrated into orchard production systems. Benzyladenine (BA) can be considered to be an endogenous-like compound which provides very little risk to the environment. A precondition of precocious bearing in young trees is the development of a canopy structure which has good cropping potential and this can be achieved by using BA. Fruit thinning with BA in mature trees can result in larger fruit size and increased return bloom the following year. However, the temperature dependence of the thinning response remains a problem to be resolved. The efficiency of PGRs is determined by the physiological age of trees, by the environmental conditions at application and by the application methods used.