Lead contamination in surface soil on roads from used lead–acid battery recycling in Dong Mai,Northern Vietnam

Used lead–acid battery (ULAB) recycling has caused numerous health and environmental issues in developing countries. Surface soil pollution from ULAB recycling activities has been linked with elevated levels of lead in human blood. We measured surface soil lead in and surrounding the ULAB recycling village of Hung Yen in northern Vietnam in 2011, 2013, and 2014. The data were analyzed statistically and discussed with respect to distance from the contamination source, year of measurement, contamination pathway, and countermeasures against the contamination. Transportation routes from the smelter or collection site displayed the greatest concentration of surface soil lead (median 6400–10,000 mg/kg). Surface soil lead decreased significantly with distance along the road from the ULAB recycling site, although such a decrease was not observed for rice fields, agricultural roads, or garden soil. Re-suspension and adherence by traffic were identified as key pollution pathways. Distance from the source, covering of the surface of roads, construction of walls, and position relative to the source were shown to be the most effective factors in the reduction of surface soil lead pollution. Application of a combination of these measures should result in improvement in the health of residents.     

Properties of a Poly(3-hydroxybutyrate) Depolymerase from Penicillium funiculosum

A poly(3-hydroxybutyrate) (PHB) depolymerase was purified from a fungus, Penicillium funiculosum (IFO6345), with phenyl-Toyopearl and its properties were compared with those of other PHB depolymerases. The molecular mass of the purified enzyme was estimated at about 33 kDa by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. The pH optimum and pI were 6.5 and 6.5, respectively. The purified protein showed affinity to Con A-Sepharose, indicating that it is a glycoprotein. Diisopropylfluorophosphate and dithiothreitol inhibited the depolymerase activity completely. The N-terminal amino acid sequence of the purified enzyme was TALPAFNVNPNSVSVSGLSSGGYMAAQL, which contained a lipase box sequence. This purified enzyme is one of the extracellular PHB depolymerase which belong to serine esterase. The purified enzyme showed relatively strong hydrolytic activity against 3-hydroxybutyrate oligomers compared with its PHB-degrading activity. PHB-binding experiments showed that P. funiculosum depolymerase has the weakest affinity for PHB of all the depolymerases examined.     

Size structure of phytoplankton biomass and photosynthesis in subtropical Hawaiian waters

In a subtropical Hawaiian ecosystem, phytoplanton size structure analyses (November–December, 1980) showed that ultraplankton (>3μm), nanoplankton (>20μm) and netplankton (>20μm) accounted for ca. 80, 98, and 2% of total chlorophyll standing stock, respectively, on the basis of chlorophyll. Similar trends were evident, for other biomass indices (e.g. cell numbers, total cell volume, ATP, particulate organic carbon, particulate organic nitrogen). The ultraplankton fraction consisted primarily of small flagellates (1 to 3 μm diam) and coccoid cells (?1 μm diam); the 3 to 20 μm fraction was represented by dinoflagellates, coccolithophores, diatoms, and chrysophytes; and the netplankton fraction consisted principally of dinoflagellates and centric diatoms. Community photosynthesis had a size distribution similar to that of biomass. Sinking rates for the 3 μm, 3 to 20 μm, and >20 μm fractions averaged 0.0, 0.09, and 0.29m d^?1, respectively. The absence of measurable sinking rates for the ultraplankton, together with the relative abundance of biomass in this fraction, result in very small phytoplankton losses due to sinking in such subtropical surface waters.     

A mechanism of “red-tide” formation

Three semi-continuous culture experiments were conducted by using natural algal populations [dominants: Skeletonema costatum, Thalassiosira sp., Gymnodinium sp., Heterosigma sp. (formerly called Olisthodiscus luteus) and Eutreptiella sp.] collected from Tanigawa Harbor, Japan, where red-tides occurred occasionally. The effects of macro- and micro-nutrients onto the growth of different species of algae were specifically evaluated by a dialysis bag culture technique. Two types of responses for nutrients were clearly observed; macro- and micro-nutrient dependency. The former group includes S. costatum, Thalassiosira sp. and Eutreptiella sp. which mainly stimulated their growth by macro-nutrients. Heterosigma sp. was in the latter group which was stimulated by micronutrients. Gymnodinium sp. showed an intermediate type. A red-tide of Heterosigma sp. formed during the experiment in the harbor and is discussed with the results of the present culture experiments and some field observations.     

Seasonal changes in abundance and development of<Emphasis Type="Italic"> Calanus pacificus</Emphasis> (Crustacea: Copepoda) in the Oyashio–Kuroshio Mixed Region

Seasonal changes in abundance and development of Calanus pacificus Brodsky were investigated by analyzing samples of different depth strata (0–150 m and 0–1000 m) collected monthly in the Oyashio–Kuroshio Mixed Region. Copepodite stage 5 (C5) emerged from dormancy and matured in early summer. A new generation appeared in July and developed into C5 during summer to autumn. Some of the summer generation arrested development at C5 and persisted below 150 m depth until the following early summer. Although the remainder matured and reproduced in October, a new generation was not observed at the surface during winter. These results suggest that C. pacificus shows two different life-cycle patterns, i.e. one generation annually, with overwintering C5 in deep waters, and two generations annually, with surface development during autumn to winter. The complex life-cycle patterns may be an adaptation to the highly fluctuating surface environment in the Oyashio–Kuroshio Mixed Region.Communicated by T. Ikeda, Hakodate     

Accumulation of paralytic shellfish poisoning toxins in planktonic copepods during a bloom of the toxic dinoflagellate<Emphasis Type="Italic"> Alexandrium tamarense</Emphasis> in Hiroshima Bay,western Japan

Concentrations of paralytic shellfish poisoning (PSP) toxins in toxic dinoflagellate cells and in marine planktonic copepods were monitored during the bloom of Alexandrium tamarense in Hiroshima Bay, western Japan. Concentration of the toxins retained by copepods was a function of the ambient toxin concentration, i.e. the product of A. tamarense cell density and cellular toxicity. The toxin concentration in copepods increased with the increase of toxicants in the seawater then leveled off, but decreased significantly at higher concentrations. In the field, the maximum toxin concentration was 1.2 pmol ind^-1, whereas in the laboratory, the copepod Acartia omorii accumulated a much higher concentration of PSP toxins (24 pmol ind^-1). Feeding avoidance against Alexandrium tamarense and a shift to alternative food sources such as diatoms in the field might keep their toxin levels lower than their potentially maximum level. The copepod toxin levels in the field were not so high as to cause an instantaneous lethal effect on their predator fishes but may reach possibly lethal levels after a few days' continuous feeding. Overall toxin retention by copepods after 12 h feeding and 2 h starvation was only 2.5% of total ingested toxins, which suggested that a significant amount of toxins was released into the seawater. Measurements of toxin reduction and gut evacuation suggested that the toxins were removed through both fecal evacuation and metabolism (e.g. excretion, decomposition and transformation). The results, as a whole, imply that copepods can be a link for PSP toxin flux in both pelagic and benthic food webs and can also be a sink for toxins by metabolizing and removing them from the environment.Communicated by T. Ikeda, Hakodate     

Vertical distribution,population structure and life cycles of four oncaeid copepods in the Oyashio region,western subarctic Pacific

Vertical distribution and population structure of four dominant oncaeid copepods (Triconia borealis, Triconia canadensis, Oncaea grossa and Oncaea parila) were investigated in the Oyashio region, western subarctic Pacific. Seasonal samples were collected with 0.06 mm mesh nets from five discrete layers between the surface and 2,000 m depth at seven occasions (March, May, June, August and October 2002, December 2003 and February 2004). The depth of occurrence of major populations of each species differed by species; the surface–250 m for T. borealis, 250–1,000 m for T. canadensis, 250–500 m for O. grossa and 500–1,000 m for O. parila. The ontogenetic vertical migration characterized by deeper occurrence of early and late copepodid stages, and shallower occurrence of middle copepodid stages was observed in T. canadensis and O. parila. Of the four oncaeid copepods, almost all copepodid stages occurred throughout the study period, suggesting that their reproduction continues throughout the year in the region. Nevertheless, a clear developmental sequence of stage-to-stage was traced for T. canadensis and O. grossa copepodids, implying their generation time to be 1 year. For T. borealis and O. parila copepodids, no clear seasonal succession was observed thus estimation of their generation time was uncertain. The present comprehensive results of vertical distribution and life cycle features for T. borealis, T. canadensis, O. grossa and O. parila are compared with the few published data on oncaeid species distributing in high latitude seas.     

Photosynthetic characteristics of marine Synechococcus spp. with special reference to light environments near the bottom of the euphotic zone of the open ocean

The present study aimed to resolve the question why marine Synechococcus spp. abundantly occur even at the bottom of the euphotic zone in the Kuroshio are. Photosynthesis under such conditions was examined using simulated blue-green model light (BGL). Results indicated that photosynthesis of marine Synechococcus spp. under BGL is as active enough to support growth of these organisms. Examination of light-harvesting under BGL indicated that active photosynthesis is permitted by an unusually high abundance of phycoerythrin (PE), which is the main light-harvesting pigment for photosystem II (PSII), due to a phycobilisome (PBS) structure which is different from ordinary hemidiscoidals. Although the absorption maximum of PE is located at longer wavelengths than the energy maximum of BGL, PE was found to absorb BGL significantly. Thus, BGL cannot be a typical photosystem I (PSI) light. PSII is also significantly excited by BGL. Carotenoids, which largely absorb BGL, were found to be effective in light-harvesting for PSI. Based on the results obtained, possible reasons why marine Synechococcus spp. commonly occur in warm waters were discussed. Two strains of Synechococcus spp. isolated from the Gulf Stream in 1981 and from Kuroshio, Japan in 1983 were used in the present study.     

Beneficial utilization of a tuna processing by-product as fish-feed additive

During tuna processing for human consumption, the fish are initially boiled in water, creating ~7000 tons of wastewater a year in Tosashimizu City, Japan. The wastewater (tuna broth; TB) is rich in free amino acids and peptides; therefore, we investigated two methods of utilizing it beneficially. In experiment 1, crude TB was used as a growth enhancer for two farmed species, juvenile yellowtail (Seriola quinqueradiata) and red sea bream (Pagrus major). Juveniles of both species, fed commercial extruded pellets mixed with 300 mL TB, showed significantly better growth than the unsupplemented control group. In experiment 2, concentrated TB was used as a dietary ingredient for juvenile yellowtail to improve palatability and growth. Dietary preferences and growth were rated as follows: fish meal diet > soy protein concentrate (SPC) + TB diet > SPC + krill meal diet > SPC diet. The beneficial effects of TB as a dietary supplement were evident. Crude TB enhanced juvenile growth at minimal cost. Concentrated TB requires processing, with associated costs; however, it proved to be a valuable fish-feed supplement because of its high palatability and growth-promoting effect. The utilization of TB also contributes to reducing the environmental impact of fish wastewater.