Distribution of PCDDs/PCDFs and Co-PCBs in human maternal blood, cord blood, placenta, milk, and adipose tissue: dioxins showing high toxic equivalency factor accumulate in the placenta

To assess levels of dioxin background contamination and transfer of dioxins from mothers to unborn children and infants, concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar-polychlorinated biphenyls (Co-PCBs) were measured in human samples from expectant and nursing mothers living in Nara, Japan. The average toxic equivalency quantities (TEQs) of PCDDs/PCDFs and Co-PCBs from circulating maternal blood, cord blood, placenta, milk taken 3-10 d after delivery, milk taken one month after delivery, and adipose tissue were 26 and 9.3, 15 and 2.3, 31 and 1.2, 16 and 5.4, 18 and 8.8, and 16 and 7.7 pg-TEQ/g-fat, respectively. Among the various PCDD/PCDF congeners, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF contributed most heavily to the TEQs of all maternal samples. Among the various Co-PCB congeners, 3,3',4,4',5-PeCB (#126), 2,3,3',4,4',5-HxCB (#156), and 2,3',4,4',5-PeCB (#118) contributed most heavily to the TEQs of all maternal samples. But, the concentrations and relative percentages of congeners differed among the various samples, suggesting that congeners showing high toxic equivalency factor accumulate in the placenta.     

Multiple colonizations of Lake Biwa by Sarcocheilichthys fishes and their population history

Rapid adaptation and speciation have not been well documented for organisms in Lake Biwa, Japan, the oldest ancient lake in East Asia. To examine these processes, we focused on the divergence of Sarcocheilichthys gudgeons and conducted phylogeographic and population genetic analyses using mitochondrial DNA sequences and microsatellite data. No remarkable genetic differentiation was found between two species, S. biwaensis and S. variegatus microoculus, both endemic to Lake Biwa, whereas this species group, including S. v. variegatus, was genetically divided into three major regional groups: the Lake Biwa, Ise Bay, and western groups. Divergent mtDNA haplotypes were included within the Lake Biwa and western groups, strongly suggesting secondary contacts among allopatrically isolated populations. Dating for mtDNA phylogeny using a geological constraint suggested the colonization of Lake Biwa by multiple Sarcocheilichthys lineages that diverged from each other in the early–middle Pleistocene. Coalescent-based population analyses indicated that the local populations colonized the rocky bottom habitat in Lake Biwa from other habitats after the Last Glacial Maximum, likely reflecting past environmental changes in the lake, including the disappearance of rocky areas during the glacial climate. Divergent morphological adaptation in Sarcocheilichthys associated with substrate type may have rapidly proceeded along with environmental changes.     

Seasonal characteristics of surface water fulvic acids from Lake Biwa and Lake Tankai in Japan

Seasonal characteristics of surface water fulvic acids (FAs) isolated from Japanese clear-water lakes were investigated. Qualitative changes in Lake Biwa and Lake Tankai FAs were determined and compared. Although the relative molecular weights determined by high-performance size-exclusion chromatography did not change remarkably, the elemental compositions, E₆₀₀^1% E_{600}^{1\% } values and ¹H- and ¹³C-NMR spectral properties varied with the season. Both the H/C and N/C ratios for Lake Biwa FAs tended to be higher than those for Lake Tankai FAs, but O/C ratios were lower and decreased from spring to winter. The E₆₀₀^1% E_{600}^{1\% } values suggested that Lake Biwa FAs contained lower levels of unsaturated structures than Lake Tankai FAs, and the amounts of these structures increased in winter. The ¹H and ¹³C NMR spectra indicated that Lake Biwa FAs are richer in saturated aliphatic chains, especially in spring. Overall, Lake Biwa FAs exhibited clearer seasonal changes in these characteristics than Lake Tankai FAs, suggesting that the seasonal variation may depend on changes in aquatic microbial activities.     

Community Structure of Bacteria Associated with Sheaths of Freshwater and Brackish Thioploca Species

Bacterial communities associated with sheaths of Thioploca spp. from two freshwater lakes (Lake Biwa, Japan, and Lake Constance, Germany) and one brackish lake (Lake Ogawara, Japan) were analyzed with denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The comparison between the DGGE band patterns of bulk sediment and Thioploca filaments of Lake Biwa suggested the presence of specific bacterial communities associated with Thioploca sheaths. As members of sheath-associated communities, bacteria belonging to Bacteroidetes were detected from the samples of both freshwater lakes. A DGGE band from Thioploca of Lake Biwa, belonging to candidate division OP8, was quite closely related to another DGGE band detected from that of Lake Constance. In contrast to the case of freshwater lakes, no bacterium of Bacteroidetes or OP8 was detected from Thioploca of Lake Ogawara. However, two DGGE bands from Lake Ogawara, belonging to Chloroflexi, were quite closely related to a DGGE band from Lake Constance. Two DGGE bands obtained from Lake Biwa were closely related to phylogenetically distant dissimilatory Fe(III)-reducing bacteria. Cloning analyses for a dissimilatory sulfite reductase gene were performed on the same samples used for DGGE analysis. The results of the analyses suggest that sheaths of freshwater/brackish Thioploca have little ecological significance for the majority of sulfate reducers.     

A bioassay to assess the potential effects of sediment resuspension on phytoplankton community composition

A laboratory assay (SAGA or Sediment Algal Growth Assay) was developed to assess the potential impact of sediment resuspension on the structure of phytoplankton communities, and to evaluate the effectiveness of various sediment treatments in decreasing the abundance of blue-green algae in the event of sediment resuspension during storms. In assays with sediment from eutrophic Akanoi Bay, Lake Biwa, Japan, 7–11 species of phytoplankton seeded from the sediments grew during the 3-week assay indicating that sediment resuspension has the potential to increase both phytoplankton biomass and species diversity. Treatment of sediments with Ca(NO3)2 substantially decreased phytoplankton biomass (measured as chlorophyll concentration) in assays with sediments from Akanoi Bay and the North Basin of Lake Biwa. Further, among various oxidation treatments of sediments, Ca(NO3)2 was most effective in decreasing or preventing filamentous blue-green algal growth in N- and P-replete media. In contrast, when sediments were added to P-limited phytoplankton dominated by green algae and diatoms, no growth of blue-green algae occurred regardless of sediment treatment. This revised version was published online in June 2006 with corrections to the Cover Date.     

Occurrence of the endangered species Nitellopsis obtusa (Charales,Charophyceae) in western Japan and the genetic differences within and among Japanese populations

Nitellopsis obtusa (Charales, Charophyceae) are widely distributed from Europe to Asia; however, this species has been recorded in only the five lakes in central Honshu in Japan. This species was thought to be extinct in Japan, but was rediscovered in limited areas of Lake Kawaguchi in central Honshu. More recently, we discovered more Japanese populations of N. obtusa in Lake Biwa in western Honshu, and it became clear that the species had a broader distribution in Japan than originally believed. In addition, although only male or female thalli have been collected at each lake, both male and female thalli were found from Lake Biwa. This is the first report of a potentially sexual population of N. obtusa in Japan. The DNA sequences of three chloroplast DNA markers, including both coding and non‐coding regions, were identical in all specimens from Lake Kawaguchi and Lake Nojiri (Central Honshu), and differed from those of Lake Biwa and German specimens. Although Japanese and German specimens were genetically similar, Japanese specimens displayed considerable genetic diversity according to locality.     

Mitochondrial DNA population structure of the white-spotted Charr (Salvelinus leucomaenis) in the Lake Biwa water system

A phylogeographic analysis of mitochondrial DNA sequences was performed in order to elucidate the origin, dispersal process, and genetic structure of white-spotted charr in the Lake Biwa water system. Two haplotypes were most common in the Lake Biwa water system, and were also common in the adjacent inlet rivers of the Sea of Japan. These results suggest that in the glacial periods of the Pleistocene, white-spotted charr dispersed into the northern inlet rivers of Lake Biwa from adjacent inlet rivers of the Sea of Japan by watershed exchanges, colonizing the whole of the Lake Biwa water system. Mitochondrial DNA diversity contrasted sharply between the western and eastern parts of the system, suggesting that the populations in the western part might be more reduced than those in the eastern part in relation to the smaller habitat size. The high overall FST estimate (0.50), together with pairwise comparisons of FST, indicated significant genetic divergence between populations due to isolation and small population size. Hierarchical analysis (AMOVA) also showed that genetic variation was more pronounced among regions (28.39%) and among populations within regions (47.24%) than within populations (24.37%). This suggests that each population in and around the Lake Biwa water system should be treated as a significant unit for conservation and management.     

Asian great lakes, especially Lake Biwa

Synopsis The geological and biological history of Asian great lakes, especially Lake Biwa in Japan, are reviewed. The origins and affiliations of endemic flora and fauna are interpreted in light of current understanding of Lake Biwa. Recent historical changes in the lake, including detrimental impacts on native fauna and water quality are summarized. The social and cultural values associated with Asian lakes are reviewed, and contrasted to those of lakes elsewhere. In general Asian great lakes are smaller than those elsewhere, with the notable exception of Lake Baikal. Furthermore, Asian lakes are typically more eutrophic, with higher primary productivity. Societal values in China and other Asian countries have tended to favour nutrient enrichment and increased cultured fish production from lakes. Asian societies, however, have long attached important artistic, poetic and cultural values to their lakes.Paper from the Canadian Society of Zoologists symposium Great Lakes of the World, organized by David L.G. Noakes.     

Phylogeny and historical demography of endemic fishes in Lake Biwa: the ancient lake as a promoter of evolution and diversification of freshwater fishes in western Japan

To elucidate the origins of the endemic fish of Lake Biwa, an ancient lake in Japan, and the role of the lake in the diversification of freshwater fish in western Japan, we established a molecular phylogenetic framework with an absolute time scale and inferred the historical demography of a large set of fish species in and around the lake. We used mtDNA sequences obtained from a total of 190 specimens, including 11 endemic species of Lake Biwa and their related species, for phylogenetic analyses with divergence time estimations and from a total of 2319 specimens of 42 species (including 14 endemics) occurring in the lake for population genetic analyses. Phylogenetic analysis suggested that some of the endemic species diverged from their closest relatives earlier (1.3–13.0 Ma) than the period in which the present environmental characteristics of the lake started to develop (ca. 0.4 Ma), whereas others diverged more recently (after 0.4 Ma). In contrast, historical demographic parameters suggested that almost all species, including endemic and nonendemic ones, expanded their populations after the development of the present lake environment. In phylogeographic analyses, common or very close haplotypes of some species were obtained from Lake Biwa and other regions of western Japan. The phylogenetic and historical demographic evidence suggests that there was a time lag between phylogenetic divergence and population establishment and that phenotypic adaptation of some endemic species to the limnetic environment occurred much later than the divergences of those endemic lineages. Population structure and phylogeographic patterns suggest that Lake Biwa has functioned not only as the center of adaptive evolution but also as a reservoir for fish diversity in western Japan.     

Effects of the common cormorant,phalacrocorax carbo,on evergreen forests in two nest sites at Lake Biwa,Japan

The effects of the habitation of the common cormorant on vegetation were evaluated in two colonies in Lake Biwa, central Japan. The state of the vegetation of each colony was classified arbitrarily into the following three types according to the appearance of the tree, shrub and herb layers; dense tree layer (Type 1), sparse tree layer and herb layer (Type 2), and sparse tree layer with dense herb layer (Type 3). The density of cormorant nesting was almost similar among the three types, except for part of Type 2. Trees, especially large ones on which cormorants nested, were found to be heavily damaged, and there were few seedlings and saplings found under the canopy trees.Chamaecyparis obtusa andCryptomeria japonica were more heavily damaged than other evergreen and deciduous trees. In the herb layer, only a few species such asReynoutria japonica orPhytolacca americana were abundant. These results suggest that the habitation of cormorants could simplify the structure and the species composition of forests.     

The ZZ/ZW sex-determining mechanism originated twice and independently during evolution of the frog, Rana rugosa

The Japanese frog, Rana rugosa, has two distinct sex chromosome types, XX/XY and ZZ/ZW. These two types are found in localized groups, separated geographically by a boundary area predicted to lie somewhere around Lake Biwa in central Japan. To determine this precise boundary, the heterogametic sex of 18 populations around Lake Biwa was examined by genotyping sex-linked genes. Phylogenetic relationships between the populations were also analyzed using mitochondrial 12S rRNA gene. Results showed that the Suzuka-Kii mountain range located east of Lake Biwa separated the XX/XY populations from the ZZ/ZW populations. Unexpectedly, from a phylogenetic perspective, the ZZ/ZW populations around Lake Biwa belonged not to the main ZW group but to the XY group. The authors propose that the ZZ/ZW populations around Lake Biwa diverged secondarily from the XX/XY group through a change of heterogametic sex, eventually forming a new group. This group was thus named the 'Neo-ZW group'. As the main ZW group inhabiting northwestern Japan is known to have a different male heterogametic origin, this finding shows that change of heterogametic sex from male to female may have occurred twice, and independently, during the frog speciation.     

Long-range transport of heavy metals from the Asian continent contributes to surface sediments in Lakes Shinji and Nakaumi in western Japan

To evaluate the contribution of the long-range transport of heavy metals from the Asian continent to the enrichment of surface sediments in western Japan, heavy-metal (Cd, Cu, Pb, Sb, and Zn) concentrations were measured in sediment cores collected at three sites each in Lakes Shinji and Nakaumi. Sedimentation fluxes of these metals were calculated on the basis of their concentrations in excess of their background concentrations. Pb showed similar sedimentation fluxes in the sites, suggesting a predominant contribution of atmospheric deposition of Pb transported from the Asian continent to the input to the lakes. In contrast, the sedimentation fluxes of heavy metals other than Pb in the surface sediments were markedly high near the estuary of a principal river flowing into Lake Nakaumi. A highly positive correlation was observed between the Cd and Zn concentrations in the cores at each site (r ² = 0.84–0.97). The Cd/Zn ratios in the surface sediments (1990–2007) indicated that Lake Shinji sediments have ratios of 0.0067–0.0074, higher than those of Tokyo Bay sediments (0.0054 on average in 1990–2003), which have been polluted primarily by effluent discharges. In contrast, the ratios in Lake Nakaumi sediments (0.0053–0.0060) were close to those in Tokyo Bay sediments. Rainwater and aerosols, which were strongly affected by air pollutants from the Asian continent, have much higher Cd/Zn ratios of 0.014–0.016. This suggests that the Lake Shinji sediments with higher Cd/Zn ratios are less affected by effluent discharges. Hence, Lake Shinji sediments may be suitable for assessing the environmental impact of the long-range transport of heavy metals from the Asian continent.     

Chemical and thermal stratification in lakes

An index that shows chemical stratification strength [IC-i; i = water quality item such as chlorophyll-a (Chl.a) and soluble phosphorus (SP)] was proposed and compared with one of thermal stratification strength indices, Schmidt’s stability index (SSI), in Shiozu Bay and Lake Biwa, Japan. The proposed indices of IC-i can be easily calculated with at least one set of each water quality data in both the epilimnion and the hypolimnion. The SSI was shown to be consistent with the traditional thermocline index of thermocline strength index (TSI), but SSI is used as the stability index of the whole lake, whereas TSI is used as the stability index near the thermocline. Analyses showed that chemical stratification strength is determined largely by thermal stratification strength. Totally different characteristics of IC-Chl.a and IC-phosphate (PO₄) at high SSI in the main North Basin of Lake Biwa and in Shiozu Bay were possibly due to the difference in their volumes and hydrodynamic conditions. The proposed index and relationships are especially useful to roughly determine thermal and chemical stratification when only few water quality data are available.     

Environmental factors which influence the sink of silica in the limnetic system of the large monomictic Lake Biwa and its watershed in Japan

Dissolved silica (DSi) and its associated biological and physicochemical factors were measured in Lake Biwa, Japan and its watershed from 2002 to 2003 in order to clarify seasonal variations in the magnitude of the sink of silica and the factors that influence it within the limnetic system. Consequently, it is concluded that Lake Biwa is a noticeable body of water where a massive sink of silica is caused. Calculated silica sedimentation in Lake Biwa was 2.0 × 10⁷ kg Si year⁻¹ (7.1 × 10⁸ mol Si year⁻¹) which is equivalent to about 80% of the annual inflow discharge of DSi to Lake Biwa. The magnitude of the sink varies seasonally by increasing in the winter holomictic stirring period, since it is greatly affected by the species composition of phytoplankton, the load of phosphorus and the condition of stratification. It seems reasonable to suppose that the DSi in Lake Biwa is removed mainly by biological processes, i.e., the assimilation of DSi by large centric diatoms and its accumulation in their frustules. Such silica sinks occur naturally in deeper stagnant waters, providing extended water residence time and supplying a certain amount of nutrients. These findings indicate that an increase in nutrient loads and abundance of stagnant water due to the construction of large dams lead to an expansion in the magnitude of the silica sink in a limnetic system.     

A new perspective on lakes: Kawanabe's latest achievements

In October 1996 the Lake Biwa Museum opened in Oroshimo, Japan after 10 years of planing and construction. It is a most ambitious concept and a very impressive facility. By June of 1997 it had attracted almost 800 000 visitors – almost twice the at tendance predicted for the entire first year of operation.The founding Director General of the Lake Biwa Museum is Hiroya Kawanabe. After a distinguished career as professor of ecology at Kyoto University, Hiroya Kawanabe founded the Centre for Ecological Research at Otsu. After retirement from the university he moved to his new position at the Lake Biwa Museum. Kawanabe-san is internationally recognized for his pioneering and collaborative research on the ayu, Pleoglossus altivelis, Lake Biwa and the ecology of Lake Tanganyika fishes (Kawanabe 1996, Kawanabe et al. 1997). The Lake Biwa Museum is not only the pinnacle of his personal and professional achievements, but also the physical embodiment of his philosophy of science and life.     

Taxonomic revision of three species of the genus Genarchopsis (Digenea: Hemiuroidea: Derogenidae) in Japan by molecular phylogenetic analyses

The taxonomic status of three nominal species of Genarchopsis (G. goppo Ozaki, 1925; G. gigi Yamaguti 1939; and G. fellicola Shimazu, 1995) (Digenea: Hemiuroidea: Derogenidae) was investigated by molecular phylogenetic analyses using partial sequences of the genomic ITS-1 region and the mitochondrial COI. The analyzed samples were divided into four groups: Lake Biwa, West Japan, Central Japan and G. fellicola. The Lake Biwa group, a sister taxon to the other three groups, was interpreted as G. gigi, so we concluded that G. gigi is valid; thus, this species is resurrected taxonomically. The specimens from the type host caught near the type locality of G. goppo were included in the West Japan group, so this group was regarded as G. goppo sensu stricto. Because the phylogenetic position of the Central Japan group could not be confirmed, it was identified tentatively as G. goppo, even though this species thus becomes paraphyletic. The taxonomic validity of G. fellicola was reconfirmed. The divergence time of G. gigi is discussed in relation to the geological history of Lake Biwa and the origin of host species.     

Management-Induced Reproductive Failure and Breeding Dispersal in Double-Crested Cormorants on Lake Champlain

ABSTRACT We studied breeding dispersal of double-crested cormorants (Phalacrocorax auritus) associated with management practices that suppressed their reproduction on Lake Champlain in the northeastern United States. We implemented an experiment on one colony by spraying corn oil on cormorant eggs in portions of the colony and leaving other portions untreated. Gulls (Larus spp.) consumed cormorant eggs during the oiling process, but we reduced and then eliminated predation levels after the first year of the study. We used mark-recapture techniques within the experimental framework to measure rates of breeding dispersal for cormorants from the experimental colony and an unmanaged colony in Lake Champlain. Egg oiling increased the movement rate to the unmanaged colony by 3% during the year with no egg predation by gulls. When gulls depredated cormorant eggs at high rates during egg oiling, movement to the unmanaged colony increased by 20%. When cormorants are managed to reduce population sizes, methods that limit dispersal away from the managed colony may be most effective. Such methods would mitigate effects to nontarget populations and allow for a greater portion of the metapopulation to be managed.     

Effects of orally administered insecticides and polychlorinated biphenyls on the parasite fauna of two species of piscivorous birds

A study was initiated to determine the effects of various levels of ingested DDT and its metabolites and polychlorinated biphenyls on young double-crested cormorants, Phalacrocorax a. auritus, and white pelicans, Pelencanus erythrorhynchos. One phase of this research was concerned with the effects of ingested insecticides and polychlorinated biphenyls on the parasite fauna of these birds. Statistical analysis indicated a decrease in the numbers of ectoparasites on the feathers of cormorants as dosage of insecticides and as residue levels on the feathers increased. Similar results were noted with ectoparasites and gular lice of white pelicans receiving a daily dosage of either polychlorinated biphenyls or a mixture of DDT, DDD, and DDE. There were no significant differences in the numbers of endoparasites between the control and treated birds in either the cormorants or pelicans.