DOI: 10.17595/20221118.001
title: 琵琶湖南湖の底生動物調査にて得られた生態的・環境的変量
title: Ecological and environmental variables measured in the benthos survey in the south basin of Lake Biwa

description: This dataset describes (1) the numerical composition of macrobenthos collected from bottom sediments, (2) ∂13C and ∂15N contents of fish, benthic organisms, macrophytes, and organic substances, and (3) environmenatal conditions at the time of macrobenthos collection in the south basin of Lake Biwa. The study purpose is to compare the macrobenthos fauna between the zone of benthic cyanobacteria and that of submerged macrophytes and know whether the cyanobacterial production is utilized by macrobenthos and other animals.
description: (1) Benthic macroinvertebrates (macrobenthos) were collected twice from the bottom sediments with an Ekman-Birge grab sampler (15 cm square in mouth) at each of six sites on eight dates from June 2017 to June 2019. Sites 17, 26, and 35 were in the benthic cyanobacterial zone and sites 16, 27, and 36 were in the submerged macrophyte zone. Site numbers are referred to Ishikawa et al. (doi: 10.1007/s10201-018-0566-y). At these sites, the bottom was mostly muddy, and the bottom sediment collected to a depth of approximately 5 cm was sieved with a NGG40 nylon mesh (470 µm opening) bag from a boat on the water. The remains were brought back to the laboratory on ice. Macrobenthos specimens were sorted from the remains with the naked eye and/or under a digital microscope (Leica DMS1000) of up to 60-fold magnification while being kept on ice. Macrobenthos specimens were morphologically identified to the seven groups. Species-level identification by molecular species delimitation and DNA barcoding is available only for 5 June 2017 and the results will be reported in a scientific paper.
description: (2) This dataset was collected to determine if the organic carbon produced by benthic cyanobacteria Microseira wollei is taken directly by benthic animals and indirectly by fish and other higher consumer animals. Bottom plant debris was sieved from grab samples of bottom sediment. Bottom surface sediment was scooped from the the surface 1-cm layer of the grab samples. The isotope analysis was made with a DELTA V Advantage mass spectrometer connected with a Flash EA 1112 elemental analyzer (Thermo Fisher Scientific) at =&lt; 0.1‰ precision. The analysis was made for each specimen individual for crustacean, chironomid, leech, and fish. Carbonate contents were removed from particulate organic matter (POM) in water, bottom plant debris, and bottom surface sediment with washing or fumigating with hydrochloric acid. Non-dietary carbonate of crustaceans was removed from a part of asellid samples. Fatty acids poor in nitrogen were removed from fish samples by washing with methanol-chloroform mixture. Macrophytes and M. wollei samples were lightly washed, but a slight amount of epiphytes was likely to remain.
description: (3) The measurements in the water column were made with a water-quality profiler (AAQ-RINKO126, JFE Advantech Co.). Mud temperature was measured in two Ekman grab samples of bottom sediment and averaged. Oxygen redox potential of the bottom sediment was measured with HORIBA portable ORP meter D-75 at the depth of 1-2 cm of two Ekman grab samples and averaged. "nd" indicates no data measured. Amounts of organic substances sieved were measured for two grab samples at each station and shown in a cell, being separated by "/".