Spatial variability in habitat associations of pre- and post-settlement stages of coral reef fishes at Ishigaki Island,Japan

Successful settlement of pelagic fish larvae into benthic juvenile habitats may be enhanced by a shortened settlement period, since it limits larval exposure to predation in the new habitat. Because the spatial distribution of marine fish larvae immediately prior to settlement versus during settlement was unknown, field experiments were conducted at Ishigaki Island (Japan) using light trap sampling and underwater visual belt transect surveys to investigate the spatial distribution patterns of selected pre- and post-settlement fishes (Acanthuridae, Pomacentridae, Chaetodonidae and Lethrinidae) among four habitats (seagrass bed, coral rubble, branching coral and tabular coral). The results highlighted two patterns: patterns 1, pre- and post-settlement individuals showing a ubiquitous distribution among the four habitats (Acanthuridae) and pattern 2, pre-settlement individuals distributed in all habitats, but post-settlement individuals restricted to coral (most species of Pomacentridae and Chaetodontidae) or seagrass habitats (Lethrinidae). The first pattern minimizes the transition time between the larval pelagic stage and acquisition of a benthic reef habitat, the latter leading immediately to a juvenile lifestyle. In contrast, the second pattern is characterized by high settlement habitat selectivity by larvae and/or differential mortality immediately after settlement.     

Genetic differences in the production of male neonates in Daphnia magna exposed to juvenile hormone analogs

We studied the susceptibility of three genetically different strains of the cyclical parthenogen Daphnia magna (Cladocera, Crustacea) in producing male neonates following exposure to juvenile hormone analogs. In experiment 1, NIES, Clone A, and Belgium A strains were exposed to the insect growth regulators (IGRs) fenoxycarb or epofenonane in a 21-day reproduction experiment. Fenoxycarb exposure decreased the total number of neonates and increased production of male neonates in a concentration-dependent manner in the NIES strain. The decrease in the total number of neonates was so great in Clone A following fenoxycarb exposure that male neonates were not observed, even at the highest concentration, where the total number of neonates was only 2% of the control. In the Belgium A strain, male neonates were observed at a rate of about 20% following exposure to the highest fenoxycarb concentration, but the total number observed was small. Epofenonane did not decrease reproduction in the NIES and Belgium A strains as dramatically as did fenoxycarb, but the neonatal sex ratio changed in a concentration-dependent manner. Although the ratio of males was as low as about 10%, induction of male neonates was also observed in Clone A following epofenonane exposure. In experiment 2, gravid females were exposed to high concentrations (5 or 10 microg/l) of fenoxycarb or pyriproxyfen for 12h. These treatments induced the production of male neonates in all strains, with a small decrease in the total number of neonates. Although induction of male neonates by juvenile hormones and their analogs was universal among genetically different strains, care is needed in interpreting the results of the 21-day reproduction tests, because decreased numbers of neonates at higher concentrations could obscure the presence of male neonates.     

Large-scale evaluation of the current level of polybrominated diphenyl ethers (PBDEs) in breast milk from 13 regions of Japan

Polybrominated diphenyl ethers (PBDEs) were measured in 2004 in 105 breast milk samples collected from 13 regions of Japan (Hokkaido, Akita, Miyagi, Tokyo, Gifu, Fukui, Kyoto, Hyogo, Wakayama, Shimane, Yamaguchi, Kochi and Okinawa). Six congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154) were determined by gas chromatography /mass spectrometry (GC/MS). Total PBDE levels ranged from 0.01 to 23.0 ng/g lipid (geometric mean (GM), 1.34 ng/g lipid). BDE-47 (GM, 0.66 ng/g lipid, 59% of sigmaPBDE) was the most abundant congener present in breast milk and was detected in 99% of the samples. Total PBDE levels were higher in northern Japan than in other regions. We analyzed the effects of occupation, age, smoking status, alcohol consumption and number of deliveries on total PBDE levels. None of these factors were significantly associated with the level of PBDEs. The present study revealed that the current level of exposure to PBDEs in Japan is lower than that in the USA or Sweden. GMs (ng/g lipid) (GSD, geometric standard deviation) and medians (ng/g lipid) of PBDE levels in each district are as follows: Hokkaido 2.70 (1.70), 2.74; Akita 4.49 (2.19), 5.44; Miyagi 1.77 (4.37), 1.11; Tokyo 1.39 (2.09), 1.63, Gifu 2.83 (4.79), 2.23; Fukui 1.05 (2.34), 1.18; Kyoto 1.31 (2.95), 1.33; Hyogo 1.02 (2.69), 0.88; Wakayama 1.33 (3.80), 1.70; Shimane 0.83 (2.51), 0.66; Yamaguchi 1.74 (2.82), 1.76; Kochi 0.50 (2.69), 0.74 and Okinawa 1.91 (2.75), 1.22. This is the first large-scale study of current PBDE levels in breast milk in Japan.     

Seasonal and diurnal presence of finless porpoises at a corridor to the ocean from their habitat

A number of local populations of finless porpoises (Neophocaena phocaenoides) are widely distributed throughout the warm coastal waters of Asia. The Omura Bay population, consisting of approximately 300 individuals, is the smallest of five populations inhabiting Japanese waters. It is a relatively new population that established after the global warming that took place approximately 9000 years ago. To observe whether these porpoises appear in the major corridor to the ocean from Omura Bay, we used acoustic monitoring to record occurrences of finless porpoises from November 2007 to May 2009. A stereo acoustic event recorder recorded the intensity and the sound source direction of biosonar signals, providing independent traces of sound sources corresponding to each detected animal. A total of 226 individuals were detected over the 1.5-year monitoring period, of which 76% occurred at night and 73% occurred during March and April. We compared the presence of porpoises to the Japanese anchovy catch in Omura Bay and the Hario Strait over the same period. Results suggested that possible reductions in anchovy resources in the bay could attract porpoises to the outside of their normal habitat. In total, 70% of the porpoise recordings took place when the tidal current was moving out of Omura Bay. Porpoises might follow the prey that are transported out of the bay due to the strong outbound current. The finless porpoises confined to the bay might extend their swimming area if prey is available.     

Relationship of PCDD/F and Co-PCB concentrations in breast milk with infant birthweights in Tokyo, Japan

OBJECTIVE: To observe how PCDD/F and Co-PCB concentrations in breast milk relate to infant birthweights in Tokyo, Japan. STUDY DESIGN: Breast milk samples were collected from 240 mothers (aged 25-34years old) residing in Tokyo to measure the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs; 14 congeners), polychlorinated dibenzofurans (PCDFs; 15 congeners), and coplanar polychlorinated biphenyls (Co-PCBs; 12 congeners) in the breast milk fat. Individual milk samples (about 50ml) were obtained 30days after delivery, between the months of June and September in 1999 and 2000. The relationship of the infant birthweights with the PCDD/F and Co-PCB concentrations was observed. RESULTS: The birthweights were negatively correlated the concentrations of many of the PCDD/F and Co-PCB congeners, with the mean toxic equivalent quantities (TEQs) of the Co-PCBs, and with the sum of the PCDD, PCDF and Co-PCBs, although their correlation coefficients were less than 0.200. Multiple regression analysis showed octachlorodioxin was statistically significant explanatory variate. CONCLUSIONS: There were slight relationship between the dioxins levels of breast milk and the birthweights of the infants.     

Combustible and incombustible speciation of Cl and S in various components of municipal solid waste

Chlorine (Cl) and sulfur (S) in municipal solid waste (MSW) are important reactive elements during combustion. They generate the acidic pollutants HCl and SOx, and, furthermore, produce and suppress organic chlorinated compounds. Nevertheless, few practical reports about Cl and S content in MSW have been published. In combustion and recycling processes, both combustible Cl and S, and incombustible Cl and S species are equally important. This paper presents the results of a comprehensive study about combustible and incombustible Cl and S in MSW components, including kitchen garbage, paper, textiles, wood and leaves, plastics and small chips. By integrating this collected data with data about MSW composition, not only the overall content of Cl and S in MSW, but also the origins of both combustible and incombustible Cl and S were estimated. The average Cl content in bulk MSW was 3.7 g/kg of raw MSW, of which 2.7 and 1.0 g/kg were combustible and incombustible, respectively. The Cl contribution from plastics was 76% and 27% with respect to combustible and incombustible states. The average S content in bulk MSW was 0.81 g/kg of raw MSW, of which 0.46 g/kg was combustible and 0.35 g/kg was incombustible. Combustible S was mainly due to synthetic textiles, while incombustible S was primarily from paper.     

Shedding of gametes in the compound ascidian Botryllus primigenus

The shedding of gametes of Botryllus primigenus Oka occurs in the natural environment early in the morning, about 1 h after dawn. The shedding of the sperm from a testis is completed within a few seconds. All the spermatozoa in a testis are released at once. Ovulation begins about 10 min after shedding of sperm and is completed in about 1 min. In general, combinative testes, i.e., testes accompanied by egg follicles, macure first, followed by egg follicles, solitary testes located on the left side of the zooid, and finally those on the right side, in that order. As a result, a population of zooids of the same generation in a colony sheds sperm on 2 or 3 successive days. Illumination preceded by darkness effectively induces shedding of gametes experimentally. The required minimum dark-adaptation period is 40 min; the required minimum illumination period is dependent on light-intensity, 8, 4 and 1 min being required at 70, 200 and 3,000 lux, respectively; the latent period is temperature-dependent, 100 to 130, 70 to 90 and 50 to 60 min being required at 21^o, 26^o and 27.5°C, respectively. An experiment in which only part of the colony was illuminated clearly indicated that each zooid responds to light-stimulus independently.Contribution No. 306 from the Shimoda Marine Research Center, University of Tsukuba, Japan.     

The acute toxicity of arsenobetaine

The acute toxicity of arsenobetaine was studied in male mice. No deaths were observed with oral administration of 10 g/kg of arsenobetaine. Therefore the LD₅₀ value was higher than 10 g/kg. This compound was found in urine in the non-metabolized form. No particular toxic symptoms were observed following administration. These results suggest that arsenobetaine has low toxicity and is not metabolized in mice.     

The flame retardant tetrabromobisphenol-A and its metabolite found in river and marine sediments in Japan

Tetrabromobisphenol-A (TBBP), used as a flame retardant, was detected in river sediments collected in Osaka, Japan, at a concentration range from 22 to 140 μg/kg (ppb), as determined on a dry weight basis. TBBP was also found in marine sediments collected at Osaka Bay, though the TBBP levels of these samples were much lower than those from river sediments. Dimethyl ether derivative of TBBP (TBBP-DM), thought to be a decomposition product from microbial methylation, was found in the river sediments but in none of the marine sediments. TBBP-DM residues were about one-hundredth of the TBBP levels.     

A simple and convenient empirical survey method with a soil electrical conductivity meter for incineration residue-derived soil contamination

To facilitate field surveys for identifying areas of incineration residue-derived soil contamination, a simple and convenient method with a soil electrical conductivity meter was examined. First, the leaching test specified by Notification No. 13 of the Ministry of the Environment, 1973, was conducted on 506 samples of 11 types of wastes and compost, and the relationship between the concentrations of toxic elements [total Hg (T-Hg), Cd, Pb, Cr⁶⁺, and As] and values of electrical conductivity (EC) was examined. The results showed that bottom ash and fly ash were wastes with high EC values and that these wastes indicated higher levels of toxic elements. Second, an estimation method for the soil EC value of contaminated soil (ECc) was proposed based on the EC values of noncontaminated soil, and its usefulness was examined. The results of field surveys conducted at sites whose soils were suspected of contamination by dioxins and other pollutants derived from incineration residues showed that the contaminated spots and areas were identified by using ECc values. Moreover, comparison of the elemental contents of soils in terms of Cr, Ni, Zn, Na, K, Ca, Fe, Mn, and others, in addition to the above-mentioned toxic elements (excluding Cr⁶⁺), with those of the potential sources of pollution was verified to be effective for identifying the source of soil contamination.