Irrigation system and land use effect on surface water quality in river, at lake Dianchi, Yunnan, China

The surface water samples were collected in river Dahe and its tributaries, which flow into severely eutrophic lake Dianchi, Yunnan Province, China, in order to elucidate factors controlling water quality fluctuations. The temporal and spatial distribution of water quality tendency was observed. The water quality of each river is dependent on the hydrology effect such water gate and circulating irrigation system. We must consider the hydrology effect to accurately understand water quality variations of river in this study field. In river without highly circulating irrigation system or water gate effect, the downstream nitrate nitrogen (NO₃-N) concentration increase occurred in area dominated by open field cultivation, whereas the NO₃-N concentration was constant or decreased in area dominated by greenhouse land use. This result suggests that greenhouse covers the soil from precipitation, and nitrate load of greenhouse could be less than that of open field cultivation while the rainfall event. In the upper reaches of river, where is dominated by open field cultivation, there were no sharp increase dissolved molybdate reactive phosphorus and total phosphorus concentration, but P load was accumulated in the lower reaches of river, whose predominant land use is greenhouse. Although the P sources is unclear in this study, greenhouse area may have potential of P loads due to its high P content in greenhouse soil. Considering hydrology effect is necessary to determine what the major factor is influencing the water quality variation, especially in area with highly complicated irrigation system in this studying site.     

Longer visits on familiar plants?: testing a regular visitor’s tendency to probe more flowers than occasional visitors

An individual pollinator may tend to consecutively probe more flowers on a plant to which it returns at shorter intervals than other plants. In a large net cage, I let individually marked bumble bees forage on flowering heads of red clovers arranged in 37 bottles (plants), each of which was monitored by an observer to record every visit and probe for 2.5 h on each of 3 days. The data of collective visits by marked individuals revealed that the bees had their own foraging areas, in which they visited a set of plants frequently and others less often, i.e., the same individual bee repeatedly returned to certain plants as a regular visitor while sampling others as an occasional visitor. I further found that as a regular visitor, an individual bee tended to probe more flowering heads on familiar plants while probing fewer on unfamiliar plants as an occasional visitor. The mean number of consecutive probes by a bee was also positively correlated with its activity (the total number of plant visits made during the observation period). The fact that each bee behaves differently on different plants indicates that the same individual pollinator can exert different influence on the reproductive success of each plant: apparently, a pollinator likely reduces the potential for geitonogamous self-pollination when foraging as an occasional visitor. Attracting occasional visitors therefore may be beneficial for plants to avoid geitonogamy. This study thus emphasizes the importance of paying attention to pollinator individuality in pollination ecology.     

Improvement of production of lipopeptide antibiotic iturin A using fish protein

To enhance the production of lipopeptide antibiotic iturin A, nutrient contents of the culture mediums were investigated in both submerged and biofilm fermentations. As a carbon source maltose and as nitrogen source, fish protein was used. In submerged fermentation maltose uptake was found lower (12%) compared to biofilm fermentation (15%) that was associated with higher cellular growth in biofilm. However, requirement of nitrogen (fish protein) concentration was found similar in both submerged and biofilm fermentations. Production of iturin A in submerged fermentation with 12% maltose and 5% fish protein was 4450 mg/L, and in biofilm fermentation it was 5050 mg/L when 15% maltose and 5% fish protein was used.     

Isolation of antifungal bacteria from Japanese fermented soybeans,natto

An inhibitory effect of a traditional Japanese fermented food, natto, was found against plant pathogens such as Rhizoctonia solani and Fusarium oxysporum, and the bacteria which showed inhibition were isolated from the natto. Among isolated bacteria, BC-1 and GAc exhibited a strong antagonistic effect in vitro against plant pathogens on an agar medium. The supernatant of bacterial culture also showed strong activity against R. solani, which meant the antimicrobial substances were produced and secreted into the medium. Both of the bacteria were estimated as Bacillus amyloliquefaciens from a partial sequence of the 16s rRNA gene. High performance liquid chromatography analysis clearly showed the production of the lipopeptide antibiotic iturin A by BC-1 and GAc.     

Screening of endophytic bacteria against fungal plant pathogens

Bacterial endophytes were found from 6 plant leaves among 35 plant leaves screened. Two of the isolated bacteria showed antagonistic activity against fungal plant pathogens. An isolate named KL1 showed the clear inihibition against plant pathogens, Fusarium oxysporum and Rhizoctonia solani, on PDA as well as TSA plate. Supernatant of the bacterial culture also showed the clear inhibition against the fungal growth on the plate and the antibiotic substance was identified as iturin A by HPLC analysis. KL1 was identified as Bacillus sp. from the 16S rRNA gene analysis. Very thin hyphae of R. solani was miccroscopically observed when the fungus was co-cultivated with KL1.     

Growth and reproductive biology of the small penaeid shrimp Trachysalambria curvirostris in Tokyo Bay

We investigated the growth and reproductive biology of the penaeid shrimp Trachysalambria curvirostris in Tokyo Bay, Japan, by monthly bottom-trawl surveys from May 2002 to December 2004. We also examined oogenesis in T. curvirostris by histological observation of the ovary. Females grew faster and attained a larger body size for age than males. The growth rate was high in summer and low in winter and was likely to be associated with seasonal changes in water temperature. The carapace length (CL) at which 50% of females contained vitellogenic oocytes was estimated to be 17.0 mm. The reproductive season extended from May to October. Young-of-the-year appeared in October and could be traced across the months on CL histograms to the following September or October, indicating a 1-year life cycle. This extended reproductive season, together with our observation of asynchronous development of oocytes in the ovary, suggests that multiple spawning by individual females may occur during the reproductive season. Postovulated oocytes were not found among the samples we collected during the daytime, suggesting that final oocyte maturation and spawning occur at night. Cortical crypts in the cytoplasm of the oocyte, considered to be a general feature of oogenesis in penaeid shrimps, were not found in T. curvirostris, even in oocytes undergoing germinal vesicle breakdown. This result implies that the cortical reaction after spawning of T. curvirostris may be different from that of other penaeid shrimps.     

Comparative analysis on the genetic population structures of the deep-sea whelks <Emphasis Type="Italic">Buccinum tsubai</Emphasis> and <Emphasis Type="Italic">Neptunea constricta</Emphasis> in the Sea of Japan

The population structures of Buccinum tsubai and Neptunea constricta were compared using partial sequences of the mitochondrial COI gene. B. tsubai included four genetically distinguishable subpopulations (Hokkaido, Yamagata-Toyama, Yamato Bank, and San’in), which is consistent with the results of our previous study using mitochondrial 16SrRNA sequences. The genetic structure of N. constricta was also clear, but the lineage sorting corresponding to the geographical distribution was not as clear as that of B. tsubai. The difference between the genetic structures of these two species might be due to a difference in either their dispersal abilities or the historic distribution patterns in the Sea of Japan. The fossil record and nested clade analyses support the latter alternative. The four subpopulations of B. tsubai are estimated to have diverged 0.42–1.46 million years ago, providing support for the existence of intermediate water of normal salinity and oxygen concentration capable of sustaining B. tsubai between the low-salinity surface water and anoxic deep water during the Pleistocene glacial periods. The genetic diversity of the Yamato Bank subpopulation of B. tsubai was lower than that of the other subpopulations, which is likely attributable to the small size of the Yamato Bank subpopulation.     

Exploring the linkages between river water chemistry and watershed characteristics using GIS-based catchment and locality analyses

A typology of land characteristics for the Humber catchment in central/eastern England is identified in relation to land use, hydrology and demographic, topographic and geological characteristics, using GIS and statistical analyses. Empirical relationships between land characteristics and water quality were examined in relation to the spatial variability in water quality across the Humber catchment. Analyses of relationships between land characteristics and water quality were undertaken at two hierarchical scales: (1) individual catchments and (2) localities of 10 km radius draining to each sampling site. The importance of urban and agricultural sources was identified, together with a hydrological component linked to dilution of point source inputs and mobilisation of specific sediment-associated contaminants in higher-energy (higher-flow) environments. High-solubility (dissolved) chemical determinands (such as B, Cl and SO₄), which undergo conservative transport through the river network, show the strongest linkages with land characteristics at the catchment scale. Cr, Zn and Ca show stronger correlations with land characteristics at the locality rather than the catchment scale, indicating that the concentrations of these determinands are more closely linked to the availability of localised sources. This work provides a starting point for investigating how changes in land use and management of drainage basins might impact river water quality at the regional scale and fluxes to the coastal zone, by providing a mechanism for examining linkages between regional-scale land characteristics and river water quality. The next step requires development of the approach within a more rigorous statistical framework and the extension of the regional analysis within a wider national and international context. Electronic Publication     

Impact of calcium and magnesium on growth and morphological acclimations of Nitella: implications for calcification and nutrient dynamics

The impact of calcium (Ca) and magnesium (Mg) on the growth and morphology of a Charophyte, Nitella pseudoflabellata, and the influence of Mg on calcification and phosphorous (P) speciation were studied in laboratory experiments for variable concentrations (≤q120 mg · L^?1) of Ca and Mg. It was clearly identified that Mg aided shoot elongation. An increase in Ca concentrations produced intensified shoot elongation also, but at a lesser rate than the equivalent levels of Mg. Depending on the availability of Ca and Mg, the morphological appearance differed significantly, suggesting significant levels of ecoplasticity. Furthermore, Mg was observed to produce less calcite encrustation. Plant P-speciation suggested a higher Mg concentration corresponding to a more water-soluble and less carbonate-bound P fraction. This indicates that upon senescence and decomposition, a large fraction of P is supplied to the water column; ultimately behaving similar to a typical vascular plant.