Distribution and temporal changes of lead in the surface seawater in the western Pacific and adjacent seas derived from coral skeletons

We determined Pb contents together with Pb isotopic compositions in coral skeletons (Porites spp.) collected from the western Pacific and adjacent seas to examine distribution of Pb in sea surfaces. Temporal records of Pb were also investigated using coral skeletons from Hainan and Ogasawara Island, located in China and Japan, respectively. The spatial distribution of Pb showed a clear dilution pattern of Pb from Asian continent to the open ocean. Also the similar trend was found in the Java Sea from Jakarta to the offshore. In addition to the spatial distribution, Pb contents in Ogasawara coral have gradually increased during last 108 years. It may be attributed to Pb emission mainly from industrial activities in Asian countries. Hainan coral, which provided 10 years record of Pb, showed a remarkable decline around 1997 probably due to the partial introduction of unleaded gasoline in China.     

An exquisitely preserved troodontid theropod with new information on the palatal structure from the Upper Cretaceous of Mongolia

Troodontidae is a clade of small-bodied theropod dinosaurs. A new troodontid, Gobivenator mongoliensis gen. et sp. nov., is described based on the most complete skeleton of a Late Cretaceous member of this clade presently known, from the Campanian Djadokhta Formation in the central Gobi Desert. G. mongoliensis is different from other troodontids in possessing a pointed anterior end of the fused parietal and a fossa on the surangular in front of the posterior surangular foramen. The skull was superbly preserved in the specimen and provides detailed information of the entire configuration of the palate in Troodontidae. Overall morphology of the palate in Gobivenator resembles those of dromaeosaurids and Archaeopteryx, showing an apparent trend of elongation of the pterygoid process of the palatine and reduction of the pterygopalatine suture toward the basal Avialae. The palatal configuration suggests that the skull of Gobivenator would have been akinetic but had already acquired prerequisites for later evolution of cranial kinesis in birds, such as the loss of the epipterygoid and reduction in contact areas among bones.     

Do bumble bee queens choose nest sites to maximize foraging rate? Testing models of nest site selection

We proposed “foundress-max” hypothesis that a bumble bee foundress chooses her nest site to maximize her energy intake rate from nectar. To examine the hypothesis, we estimated the maximum energy intake rate at each site in the study area and compared the distribution of the maximum energy intake rates with those of actual nest sites. We also calculated rank correlations of the maximum energy intake rate with the number of nest-searching foundresses at 54 sites. The nest locations supported the foundress-max hypothesis, but the number of nest-searching foundresses did not. This could be attributed to the density of food sites: many food sites may attract many foundresses. Therefore, we subsequently proposed “foundress-sum” hypothesis that a foundress chooses her nest site to maximize the sum of energy intake rates. The nest locations supported the foundress-max hypothesis more than the foundress-sum hypothesis. A profitable food site would affect foundresses’ nest site selection.     

Determination of nonylphenol ethoxylates and octylphenol ethoxylates in environmental samples using 13C-labeled surrogate compounds

Alkylphenol polyethoxylates (APEOs) have been widely used as nonionic surfactants in a variety of industrial and commercial products. Typical compounds are nonylphenol polyethoxylates (NPEOs) and octylphenol polyethoxylates (OPEOs), which serve as precursors to nonylphenol (NP) and octylphenol (OP), respectively. NP and 4-t-OP are known to have endocrine disrupting effects on fish (medaka, Oryzias latipes), so it is important to know the concentrations of APEOs in the environment. Because the analytical characteristics of these compounds depend on the length of the ethoxy chain, it is necessary to use appropriate compounds as internal standards or surrogates. We synthesized two 13C-labeled surrogate compounds and used these compounds as internal standards to determine NPEOs and OPEOs by high-performance liquid chromatography (LC)-mass spectrometry. Method detection limits were 0.015 microg/L for NP (2)EO to 0.037 microg/L for NP(12)EO, and 0.011 microg/L for OP(3,6)EO to 0.024 microg/L for OP (4)EO. NPEO concentrations in water from a sewage treatment plant were less than 0.05-0.52 microg/L for final effluent and 1.2-15 microg/L for influent. OPEO concentrations were less than 0.05-0.15 microg/L for the final effluent and less than 0.05-1.1 microg/L for influent.     

Enhancement of biodegradation of oil adsorbed on fine soils in a bioslurry reactor

Techniques for enhancing the biodegradation of oil-contaminated fine soils in a slurry-phase bioreactor were investigated. Using a model system consisting of kaolin particles containing adsorbed n-dodecane as a diesel fuel surrogate, we investigated how increasing the temperature and adding a surfactant and various hydrophobic support media affected the biodegradation rate of n-dodecane. Increasing the temperature from 25 to 35 degrees C decreased the time required for complete degradation of n-dodecane by 30%, from 110h to 80h. Addition of the surfactant polyethylene glycol p-1,1,3,3-tetramethylbutylphenyl ether decreased the degradation time to less than 48h at 35 degrees C, although a high concentration of the surfactant (3000mgl(-1)) was required. We suspect that the surfactant increased the degradation rate by solubilizing the n-dodecane into the solution phase in which the microorganisms were suspended. We tested five types of organic polymers as support media for the microorganisms and found that the biodegradation time could be reduced by approximately 50% with a support medium made from polyurethane; in the presence of this medium, only 36h was required for complete decomposition at 35 degrees C. The reduction in the degradation time was probably due to transfer of the n-dodecane from the soil to the support medium, which improved contact between the n-dodecane and the microorganisms. The polyurethane support medium bearing the microorganisms was stable and could be reused.     

Polychlorinated biphenyl (118) activates osteoclasts and induces bone resorption in goldfish

To analyze the effect of polychlorinated biphenyl (PCB) 118 on fish bone metabolism, we examined osteoclastic and osteoblastic activities, as well as plasma calcium levels, in the scales of PCB (118)-injected goldfish. In addition, effect of PCB (118) on osteoclasts and osteoblasts was investigated in vitro. Immature goldfish, in which the endogenous effects of sex steroids are negligible, were used. PCB (118) was solubilized in dimethyl sulfoxide at a concentration of 10 ppm. At 1 and 2 days after PCB (118) injection (100 ng/g body weight), both osteoclastic and osteoblastic activities, and plasma calcium levels were measured. In an in vitro study, then, both osteoclastic and osteoblastic activities as well as each marker mRNA expression were examined. At 2 days, scale osteoclastic activity in PCB (118)-injected goldfish increased significantly, while osteoblastic activity did not change significantly. Corresponding to osteoclastic activity, plasma calcium levels increased significantly at 2 days after PCB (118) administration. Osteoclastic activation also occurred in the marker enzyme activities and mRNA expressions in vitro. Thus, we conclude that PCB (118) disrupts bone metabolism in goldfish both in vivo and in vitro experiments.     

Respiratory uptake kinetics of neutral hydrophobic organic chemicals in a marine benthic fish, Pseudopleuronectes yokohamae

We investigated the respiratory uptake kinetics of polychlorinated biphenyls (PCBs), organohalogen pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and 2,2′,4,4′-tetrabrominated diphenyl ether (BDE #47) in a marine benthic fish, Pseudopleuronectes yokohamae. The respiratory uptake efficiencies (E_W) of the chemicals, of which there have been no reports for the majority of persistent organic pollutants (POPs), were obtained by measuring the respiratory uptake rate constants (k₁) and the oxygen consumption rates of fish. Fish were exposed to water in which these chemicals were dissolved at environmentally relevant concentrations for 28 d, followed by 168 d of depuration in clean seawater. The k₁ and E_W values for 99 compounds were obtained, and they ranged from 2000 to 42 000 L kg-lipid⁻¹ d⁻¹ and from 0.060 to 1.3, respectively. The E_W values of the chemicals, except for PAHs, tended to increase with increasing values of the log octanol–water partition coefficients (K_OW) of the chemicals up to a log K_OW of 5. For log K_OW in the range 3–5, the E_W values in this study were much lower than those in a published study (about one-third). As a result of analysis by a two-phase resistance model, the resistance of transport rates to the lipid phase in this study was lower than was the case in the published study. These findings indicate that the E_W predicted by the published study for log K_OW in the range 3–5 may differ among fish species and water temperature, and further study is needed.     

Occurrence of selected pharmaceuticals in river water in Japan and assessment of their environmental risk

The existence of pharmaceuticals in the water environment is thought to be a potential problem for aquatic organisms. In this study, we conducted a nationwide survey to clarify the occurrence of 24 selected pharmaceuticals in major Japanese rivers and evaluated their environmental risk to aquatic organisms. We found a total of 22 substances in river waters at concentrations from several nanograms per liter to several micrograms per liter. We found the highest, which was 2.4 μg/L of caffeine, followed by 1.5 μg/L of crotamiton and 1.4 μg/L of sulpiride. We conducted an environmental risk assessment of the 22 pharmaceuticals detected in river water, for which predicted no-effect concentration (PNEC) values for crustacea and algae had been obtained. The measured environmental concentration/PNEC values of four substances, caffeine, carbamazepine, clarithromycin, and ketoprofen, exceeded 0.1 with the maximum value of 9.0 for clarithromycin. As clarithromycin exhibits a high environmental risk to aquatic organisms, particular attention is required.