41 research outputs found
Short-term variation in benthic phosphorus transfer due to discontinuous aeration/oxygenation operation
Abiotic formation of amorphous carbonaceous particles by a HMX (cyclotetramethylenetetranitramine) explosion experiment: implication from organic matter and the quench effect
Poster P03 abrtract, HAYABUSA 2014: 2nd symposium of solar system materials (4-5 December 2014, Sagamihara, Japan
High spatial resolution analysis of the distribution of sulfate reduction and sulfide oxidation in hypoxic sediment in a eutrophic estuary
Bottom hypoxia and consequential hydrogen sulfide (H2S) release from sediment in eutrophic estuaries is a major global environmental issue. We investigated dissolved oxygen, pH and H2S concentration profiles with microsensors and by sectioning sediment 2 cores followed by colorimetric analysis. The results of these analyses were then compared with the physicochemical properties of the bottom water and sediment samples to determine their relationships with H2S production in sediment. High organic matter and fine particle composition of the sediment reduced the oxidation-reduction potential, stimulating H2S production. Use of a microsensor enabled measurement of H2S concentration profiles with submillimeter resolution, whereas the conventional sediment-sectioning method gave H2S measurements with a spatial resolution of 10 mm. Furthermore, microsensor measurements revealed H2S consumption occurring at the sediment surface in both the microbial mat and the sediment anoxic layer that were not observed with sectioning. This H2S consumption prevented H2S release into the overlying water. However, the microsensor measurements had the potential to underestimate H2S concentrations. We propose that a combination of several techniques to measure microbial activity and determine its relationships with physicochemical properties of the sediment is essential to understanding the sulfur cycle under hypoxic conditions in eutrophic sediments
Impact of improved bottom hypoxia on zooplankton community in shallow eutrophic lake
We followed changes in the abundance of meso- and microzooplankton after an existing
bottom hypoxia improved by the introduction of water with high oxygen content into the
bottom. Mesozooplankton, calanoid copepod Acartia hudsonica showed ten
times higher abundance under high oxygen condition at the bottom than under control where
there was less oxygen at the bottom. On the other hand, during summer when
microzooplankton such as rotifers and small cyclopoid species Oithona
spp. were dominant, no difference in their distribution pattern and abundance was
observed. Results have suggested that oxygen concentration at the bottom is one important
factor determining the abundance and distribution of mesozooplankton even in local-scale
probably by providing bottom refuge, but not for microzoooplankton. Since spring season is
important for recruitment of many commercial fish juveniles, the distribution of oxygen in
the lake seems very important for the fish stock in the lake
Impact of improved bottom hypoxia on zooplankton community in shallow eutrophic lake
We followed changes in the abundance of meso- and microzooplankton after an existing
bottom hypoxia improved by the introduction of water with high oxygen content into the
bottom. Mesozooplankton, calanoid copepod Acartia hudsonica showed ten
times higher abundance under high oxygen condition at the bottom than under control where
there was less oxygen at the bottom. On the other hand, during summer when
microzooplankton such as rotifers and small cyclopoid species Oithona
spp. were dominant, no difference in their distribution pattern and abundance was
observed. Results have suggested that oxygen concentration at the bottom is one important
factor determining the abundance and distribution of mesozooplankton even in local-scale
probably by providing bottom refuge, but not for microzoooplankton. Since spring season is
important for recruitment of many commercial fish juveniles, the distribution of oxygen in
the lake seems very important for the fish stock in the lake
Evaluation of origin place of corbicula japonica using fluorescence properties of samples by firing shells
High spatial resolution analysis of the distribution of sulfate reduction and sulfide oxidation in hypoxic sediment in a eutrophic estuary
Evaluation of Unified Algorithms for Remote Sensing of Chlorophyll-a and Turbidity in Lake Shinji and Lake Nakaumi of Japan and the Vaal Dam Reservoir of South Africa under Eutrophic and Ultra-Turbid Conditions
We evaluated unified algorithms for remote sensing of chlorophyll-a (Chla) and turbidity in eutrophic and ultra-turbid waters such as Japan’s Lake Shinji and Lake Nakaumi (SJNU) and the Vaal Dam Reservoir (VDR) in South Africa. To realize this objective, we used 38 remote sensing reflectance (Rrs), Chla and turbidity datasets collected in these waters between July 2016 and March 2017. As a result, we clarified the following items. As a unified Chla model, we obtained strong correlation (R2 = 0.7, RMSE = 2 mg m−3) using a two-band model (2-BM) and three-band model (3-BM), with Rrs(687)/Rrs(672) and [Rrs−1(687) − Rrs−1(672)] × Rrs (832). As a unified turbidity model, we obtained strong correlation (R2 = 0.7, RMSE = 260 NTU) using 2-BM and 3-BM, with Rrs(763)/Rrs(821) and Rrs(810) − [Rrs(730) + Rrs(770)]/2. When targeting the Sentinel-2 Multispectral Imager (MSI) frequency band, we focused on MSI Bands 4 and 5 (Rrs(740) and Rrs(775)) for the Chla algorithm. When optically separating SJNU and VDR data, it is effective to use the slopes of MSI Bands 3 and 4 (Rrs (560) and Rrs (665)) and the slopes of MSI Bands 7 and 9 (Rrs(775) and Rrs(865))