Lake restoration by biomanipulation using piscivore and Daphnia stocking; results of the biomanipulation in Japan

Biomanipulation has been employed in numerous locations throughout the world as a means for reducing phytoplankton biomass; however, it has not been employed very often in Japan. A common approach involves the introduction of piscivorous fish to reduce the abundance of planktivorous fish. In our study, to first apply biomanipulation, we stocked Lake Shirakaba (a high-altitude, protected area in a park) in central Japan with rainbow trout fingerlings and cladoceran Daphnia (Daphnia galeata) in 2000. A “pre-biomanipulation” data set (1997–1999) and “a post-biomanipulation” data set (2000–2006) allowed us to evaluate the lake's response to biomanipulation. After the biomanipulation, zoo-planktivorous pond smelt disappeared and a large population of Daphnia had been established, which substantially reduced the number of the previously dominant small cladocerans and rotifers. Water transparency increased from about 2 m (before biomanipulation) to more than 4 m (after biomanipulation). Reductions in algal biomass and increased transparency led to expansion of the submerged macrophyte Elodea nuttallii. Total phosphorus concentrations declined as well over this time period. Based on these results, we concluded that biomanipulation using piscivore and Daphnia stocking succeeded in improving lake water quality by reducing algal abundance and providing favorable conditions for the establishment of rooted plants.     

Construction of a T-vector using an esterase reporter for direct cloning of PCR products

We constructed an efficient T vector pTQEST216T that employed an engineered esterase as an indicator for direct cloning of PCR products. After ligation of the XcmI-digested vector with PCR products, this cloning system could easily discriminate positive clones due to insertional inactivation of the esterase reporter. Additionally, PCR products were cloned into this vector efficiently without the gel purification steps, due to the well-designed multi-cloning site that was in-frame fused at the circularly permutated gap of the reporter.     

Targeted cowpea chlorotic mottle virus-based nanoparticles with tumor-homing peptide F3 for photothermal therapy

Our aim was to devise targeted drug delivery systems using genetically modified cowpea chlorotic mottle virus (CCMV) capsids by fusion expression with tumorhoming peptide F3 for efficient delivery of therapeutic substances into tumor cells. The RNA-binding domain at the N terminus (amino acid residues 1–25) of CCMV capsid protein (CP) was selectively deleted, and F3 was inserted for the expression in Pichia pastoris. After chromatographic purification, F3-CCMV capsids were obtained via selfassembly of the F3-CP fusion protein and then analyzed by transmission electron microscopy and dynamic light scattering analysis, which revealed spherical nanoparticles (NPs) ca. 18 nm in diameter with regular monodispersity. Near-infrared fluorescent dye IR780 iodide, which has been applied for cancer imaging, photodynamic therapy, and photothermal therapy, was encapsulated in F3-CCMV NPs. The resultant F3-CCMV-IR780 NPs showed excellent molecular targeting to nucleolin receptor overexpressed on the surface of MCF-7 tumor cells. Furthermore, the in vitro cellular uptake and cell viability assay proved a photothermal effect by a single dose of near-infrared laser irradiation. The present system may offer a programmable nanoscaffoldbased drug delivery system vehicle for fabrication of promising therapeutic substances for cancer therapy.     

Abstracts from the Japanese Journal of Limnology

The Japanese Journal of Limnology is another official publication of the Japanese Society of Limnology. The original papers in the journal were peer-reviewed by a few authorized referees, and appeared in Japanese with English abstracts.An erratum to this article can be found at     

Ecological niche separation in the Polynucleobacter subclusters linked to quality of dissolved organic matter: a demonstration using a high sensitivity cultivation-based approach

The free-living, cosmopolitan, freshwater betaproteobacterial bacterioplankton genus Polynucleobacter was detected in different years in 11 lakes of varying types and a river using the size-exclusion assay method (SEAM). Of the 350 strains isolated, 228 (65.1%) were affiliated with the Polynucleobacter subclusters PnecC (30.0%) and PnecD (35.1%). Significant positive correlations between fluorescence in situ hybridization and SEAM data were observed in the relative abundance of PnecC and PnecD bacteria to Polynucleobacter communities (PnecC?+?PnecD). Isolates were mainly PnecC bacteria in the samples with a high specific UV absorbance at 254?nm (SUVA(254) ), and a low total hydrolysable neutral carbohydrate and amino acid (THneutralCH?+?THAA) content of the dissolved organic matter (DOM) fraction, which is known to be correlated with a high humic content. In contrast, the PnecD bacteria were abundant in samples with high chlorophyll a and/or THneutralCH?+?THAA concentrations, indicative of primary productivity. With few exceptions, differences in the relative abundance of PnecC and PnecD in each sample, determined using a high-sensitivity cultivation-based approach, were due to DOM quality. These results suggest that the major DOM component in the field, which is allochthonously or autochthonously derived, is a key factor for ecological niche separation between PnecC and PnecD subclusters.     

ROLE OF ENCYSTMENT AND EXCYSTMENT OF PERIDINIUM BIPES F. OCCULATUM (DINOPHYCEAE) IN FRESH WATER RED TIDES IN LAKE KIZAKI,JAPAN1

The encystment flux of Peridinium bipes f. occulatum (Dinophyceae) was investigated with sediment traps from 1968 to 1990 in Lake Kazki. Cysts of P. bipes were formed throughout the blooms, Encystment flux of P. bipes in the pelagic zone was usually lower than those at shallow sites, and the density of P. bipes cysts in lake sediment was higher in the shallow region than in the pelagic zone. However, in the shallower region, The concentration of P. bipes cysts varied widely, possibly due to high rates of encystment and excystment. Peridinium bipes encystment occurred between 15° and 25° C in the laboratory, with very little cyst formation below 10°C. Though cyst formation was observed in continous darkness, the rate increased with irradiance. Under continuous darkness, no excystment was observed at any temperature from 5° to 25° C. Eighty-one percent of the cysts illuminated at 105 μE m^?2 s^?1 excysted after 13 days incubation at 15° C, and lower irradiances decreased germination success. Results from laboratory experiments suggest that light is a critical factor in the germination of P. bipes cysts. Bottom depth thus can have a significant effect on germination because cysts only can excyst from depths where light is sufficient. The shallow region of the lake is thus very important as a seed bed for P. bipes during early spring. Cyst deposited in deeper waters may not ever germinate unless they are resuspended and transported to shallow areas where light reaches the bottom.     

Accumulation and depuration of microcystin produced by the cyanobacterium <Emphasis Type="Italic">Microcystis</Emphasis> in a freshwater snail

Seasonal changes in microcystin concentrations in a resident snail (Sinotaia histrica) and an edible clam (Corbicula sandai) in Lake Biwa were surveyed. To clarify both the accumulation and depuration of microcystins, experimental studies with microcystin were also carried out on the snail. In the field investigation, microcystin was detected from the hepatopancreas and intestine of S. histrica (up to 3.2µgg^–1 dry weight and 19.5µgg^–1 dry weight, respectively); however, no microcystin was detected in the hepatopancreas of C. sandai. In the laboratory experiment, the microcystin-LR concentration in the hepatopancreas of S. histrica reached a value of 436µgg^–1 dry weight on day 10 of 15 days of uptake, and a high value persisted despite a depuration period of 15 days. The depuration rate constant of microcystin and its biological half-life were 0.0828 day^–1 and 8.4 days, respectively. These results indicate that S. histrica has a high ability to accumulate microcystin in its tissue. Because S. histrica is predated by fish and water fowl, it is likely to play an important role as a vector for microcystin in lakes with dense blooms of toxic cyanobacteria.     

Effects of light conditions on growth and defense compound contents of Datura inoxia and D. stramonium

Journal of Plant Research - We examined the effects of light conditions on plant growth and production of defense compounds in the toxic species Datura inoxia and D. stramonium. Specifically, we...