Epiphytic diatom assemblages on reed (Phragmites australis) stems were analyzed. Fourteen samples from reed stems and one from Japanese eelgrass were collected in December 2006 and April/May 2007 from the Ohashi-Kensaki River network. This river network forms the connection between two large lagoonal lakes in west-central Japan, Lake Shinji and Lake Nakaumi. Seventy-six taxa were observed on reed stems in these rivers. We present taxonomical information and light microscope images of the 17 most common taxa present in these samples. The genus Tabularia was the dominant group. These observations suggest that diatom assemblages on reed stems are influenced by seasonality and current velocity. Salinity effects can also be seen in these samples, but they do not seem to be a major control on the reed stem assemblage.

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The aim of this work is the identification of the main factor affecting the monthly salinity variation in Lake Shinji, Japan. A strong correlation was observed between the mean daily flow rate of the Hii River, measured over 80 days at Kamishima, and the chlorinity in the central part of the lake. The fluctuation of chlorinity in Lake Shinji could be reproduced based on the flow rate at Kamishima. This result demonstrates that the salinity fluctuation of Lake Shinji significantly depends on the flow rate of the Hii River.

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Using a 150-cm lake bed core sample, the paleoenvironmental change during the past ~1,300 years in Lake Koyama-ike, Tottori Prefecture, western Japan, was reconstructed based on diatom fossil assemblages, electric conductivity, and radiocarbon ages. Consequently, the following points were clarified:
1) During the past 1,300 years, the surface water of Lake Koyama-ike has been a freshwater environment—freshwater pond or lake—because freshwater diatom species were dominant in the entire core. In contrast, due to salinity stratification, a brackish-to-marine environment has remained immediately above the lake bed.
2) The diatom fossil assemblages indicated the decrease in water salinity and depth after ~1,000 cal BP. Because a similar transition has been previously reported in studies conducted at other sites in Lake Koyama-ike, this environmental change is a common phenomenon in this lake.
3) A decrease in water salinity around 1,000 cal BP indicated that the channel connecting the Japan Sea and Lake Koyama-ike was filled by the blown sand. The shallowing of the lake around the same period was probably caused due to rapid deposition of riverine sediments and relative sea-level fall, which presumably induced the sand to actively blow in the coastal area.

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The objective of this study is to estimate the precision of water surface temperature (LST) in Japanese lakes using Landsat-8 TIRS data for the just after 1 year launched in February 2013. The satellite / observed data set in 2013 was collected in main lakes of our country such as Lake Shinji, Lake Nakaumi, Lake Biwa, Lake Kasumigaura, and Lake Ogawara. The following matters became clear. 1) The LST precision by the single band method was about 1.6 - 3.1 ºC. 2) The LST precision by two band method using TIRS band 10 and band 11 was about 0.9 ºC. 3) The LST precision by two-band method, which considered the effect of the solar zenith angle correction for water-vapor absorption, was 0.9 ºC. Therefore, The LST estimation by simple two-band method using TIRS band 10 and band 11 only was recommended by this research.

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Benthic fauna of Lake Nakaumi, including the Honjo area, was recorded in the summer of 2016. No benthic individuals were collected from 59 stations out of the total 133 stations. There were 42 stations where only polychaetes including Pectinaria okudai were collected. Benthic fauna was classified into five groups (Sakai, Bivalves, Nakaura, PP, Po) using nMDS analysis. Group Sakai had the most diverse fauna with higher values of dissolved oxygen concentrations. Group Bivalves consisted of the stations with shallower depth, resulting suitable habitats for bivalve species. Arcuatula senhousia was the predominant species both in number and wet weight. Approximately three fourth of the stations (101/133) of Lake Nakaumi had no individuals or contained only polychaetes, indicating that environmental conditions were severe in the summer of 2016.

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