Lake Shinji from 1635 up to the time of the widening of the Ohashi River, which was carried out from 1924 to 1933 (from the late Taisyo era to the early Syowa era) has been believed as a fresh water lake. This belief is based on previous reports on the damage from salt after the widening, or a diatom analysis of the core sediments of Lake Shinji. To confirm the validity of this belief, the salinity of Lake Shinji before the widening was investigated from various viewpoints from reports on fishery operation, fishery statistics, sediment analysis and a hydraulic study. From this investigation, we propose that Lake Shinji before the widening was an oligohaline lake, with intermittent saline water intrusion from the adjacent Lake Nakaumi depending on meteorological conditions. The intrusion of saline water was considered to increase in summer with a decrease in fresh water inflow, and made brackish water fishes migrate and inhabit Lake Shinji. In the case of a dry year, marine dinophyceae predominated, which was recorded in the core sediments of the lake. Our results strongly suggest that a single approach to reconstructing past environments can be easily misinterpreted, and that an interdisciplinary approach is indispensable for such purpose.
A fluidized bed reactor with polyvinyl alcohol (PVA) gel beads as a biomass carrier was used for the degradation of p-nitrophenol (PNP) in an artificial wastewater. PNP (200 mg·l-1) was completely degraded at a hydraulic retention time (HRT) of 6 hours in the presence of 10 mg·l-1 glucose. However, PNP degradation became unstable at 250 mg·l-1 PNP and did not recover, which suggests that the decrease in the activity of PNP-degrading bacteria is due to the presence of glucose. On the other hand, when only PNP was supplied to the reactor, PNP (360 mg·l-1) was almost completely degraded at an HRT of 6 hours, and the PNP removal rates per volume and total solids (TS) were determined as 54 mg·l-1·h-1 and 12.6 mg·g-1·h-1, respectively. From the PCR-DGGE result, two bacterial DNA sequences similar to those of Acidovorax and Arthrobacter, which are known for their PNP degrading ability, were determined in the biomass attached to the PVA gel beads; thus, we conclude that these bacteria mainly contribute to the PNP-degrading activity in the reactor.
There is growing awareness of the need to evaluate the long-term effects of wildlife populations, not only in terms of the level of short-term effects on individuals, but also in terms of much subtler, multigenerational effects particularly for long-term conservation of ecosystems. Here, we show population genetic structure of Pseudorasbora parva in the Kanto region and estimate the main stressors to influencing genetic variability and genotype. Genetic diversity within a population was significant among sampling sites, but no significant relationship was detected between genetic diversity and contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals, because of many types of stress effects and random genetic drift. On the other hand, cluster analysis of the fluorescence intensity of individual DNA fragment profiles measured by amplified fragment length polymorphism (AFLP) analysis identified five genotypes: two existed in many sites in the Kanto region, and three existed in only a few sites. Genetic diversity or genotype proportion in a population at the sites where these two genotypes was dominant were also significantly related to dissolved PAH, dissolved fluoranthene, dissolved benzo[k]fluoranthene and benzo[k]fluoranthene concentrations in sediments. Finally, the population genetic structure in eight sites along the Nogawa river was evaluated. These results showed genetic diversity and genotype proportion changed discontinuously in some sites, because of changes in PAH concentration and limited migration.
We surveyed the water quality of irrigation reservoirs in a tea field catchment. The study area was located in Shizuoka Prefecture, Japan. Water in some of the reservoirs showed alkalinity because of the photosynthesis of aquatic plants. On the other hand, water in one irrigation reservoir showed acidity because of nitrogen fertilizer. The NO3-N concentration increased how many times owing to large runoff from a watershed when rainfall was strong and heavy accumulation. The Changes in NO3-N concentration were small throughout the season when was light rainfall. The average of NO3-N concentration in the irrigation reservoirs was about 5 mg·l-1.
The long-term monitoring of vertical water quality has been continued using the common name “Imazuokichuo” in the northern basin of Lake Biwa since 1979. The results of the main monitored parameters such as water temperature, dissolved oxygen (%), and COD, T-N and T-P concentrations from 1979 to 2004 were investigated. Annual changes in the temperature of water at depths of 0.5 and 10 m showed a tendency to increase with atmospheric temperature. The tendency of the temperature of water at a depth 90 m to increase was low in terms of the annual average, but high in terms of the annual minimum. Annual changes in the dissolved oxygen (%) of water at a depth of 90 m showed a tendency to be nearly constant in terms of the annual average but showed no clear tendency in terms of the annual minimum. Annual changes in COD concentration showed tendencies to decrease in the period from 1980 to 1985 and increase in 1985 at all depth intervals. Annual changes in T-N concentration showed tendencies to increase gradually in the period from 1979 to 1999, decrease in 2000, to be nearly constant in 2001, and markedly decrease in 2002 at all depth intervals. Annual changes in T-P concentration showde a tendency to be nearly constant at all depth intervals except 90 m.