Grazing pressure by amphipods on microalgae in Nanakita river estuary (Gamo lagoon), Japan

Grazing pressure effects exerted by four species of amphipods on epiphytic microalgae were determined in Nakakita river estuary (Gamo lagoon) Japan, considering microalgal strength of adhesion to surfaces with regard to their susceptibility to grazing. Grazing effects were examined for three groups of diatoms, including naturally storongly-attached cells, moderately-attached cells and fairly-attached cells. Diatom species with filamentous forms or low adhesive strength were susceptible to grazing, while those with tighter adhesion were less affected by grazing pressure. Seasonal trends of both amphipods and microalgae found on the macroalgae Gracilaria vermiculophylla showed high densities of amphipods and low densities of microgae during warmer months (June to September) and vice versa in colder months (December to March). This immerse relationship between densities of amphipods and diatoms suggests a casual relationship and shows that effects grazing pressure by amhpipods on epiphytic diatom communities seem to be strong in Gamo lagoon. A manipulated experiment (feeding pressure experiment) revealed that Melosira sp. and Nitzchia sp. were mostly selected by tube-dwelling species (Corophium uenoi and Grandidierella japonica), whilst Gyrosigma sp. and Melosira sp. selected by free-living species (Eogammarus passjeticus and Melita setiflagella).Article信州大学山地水環境教育研究センター研究報告 2: 17-20(2004)departmental bulletin pape

Seasonal changes of carbon and nitrogen stable isotope ratios for dominant species: chironomid larvae, phytoplankton, and benthic diatom inhabiting strongly acidic Lake Katanuma

Lake Katanuma is a colcanic, strongly acidic lake (average pH of 2.2), located in Miyagi prefecture, Japan. Only a few spieccies are found in Katanuma; Chironomus acerbiphis larvae as benthic invertebrate, Pinnularia baunii as benthic diatom, and Chlamydomonas acidophila as phytoplnkton. We tried analyzing seasonal changes of carbon and nitrogen stable isotope raios foethese spicies in Lake Katanuma. Food souece analysis by isotope ratios clearly showed main food source for Chironomus acerbiphilus larvae was P.braunii (benthic diatom). δ1C values of P.braunii varied seasonally, while those of POM (mainly phytoplankton) remained fairly stable. The difference of stable isotope ratios in these orfanisms discussed.Article信州大学山地水環境教育研究センター研究報告 2: 25-28(2004)departmental bulletin pape

Environmental fluctuations of the Lake Chany complex in western Siberia based on NOAA images

The Lake Chany complex, located in Western Siberia, consists of the large shallow lakes with an average depth of about 2m. The lake area fluctuates according to water level that depends closely on the amount of inflow( snow-melt) and the evaporation, since the lake complex has no outflow river. Based on NOAA/AVHRR satellite normalized difference vegetation index (NDVI) data of the ice-free periods in 2000 and 2001, we evaluated the seasonal changes in the lake area and the surroundingu vegetations of the Lake Chany complex. In late April or early May, the maximum lake area was abserved and the lake area decreased drastically until late May or early June. Then, the lake area decreased gradually from early June to late August. The lake area in August was about 70% of the maximum. Then, the area tends to increase by early October. Compared with the ground truth in August 2001, the seasonally fluctuated areas on NOAA images corresponded to the vast vegetations with several km in width of reed (Phragmites communis) stands which seem to be influenced by the inflow of snow meltwater and the growth of reeds.Article信州大学山地水環境教育研究センター研究報告 2: 1-4(2004)departmental bulletin pape

Preliminary studies on carbon and nitrogen stable isotope ratios analysis of food web in Lake Chany of Western Siberia

Lake Chany is an inland moderately saline lake in Western Siberia. Itconsists of three lakes, Bolshye (Large) Chany, Malye (Small) Chany and Yarkul Pool. Field survey of Lake Chany was carried out at four parts of the lake with different salinity to analyze their food web structures using carbon and nitrogen stable isotope as natusral tracers. The intruding river rigion (St.1) and Malye Chany (St.2) wwkth low salinity (0.9%), the central part of Bolshye Chany (St.3) with salinity of 5.7% and the innermost part of Bolshye Chany (St.4) with the highest salinnity of 6.3% were selected as study sites. Comparison of the isotope ratios of benthis incertebrate (Chironomidae; Diptera) among the sampling sites showed the lowest δ13C and δ15N values at St.1 and highest values at St.4. The benthic invertebrates at St.3 showed similar δ13C and δ15N values to those of St.4 and St.1, respectively. Similar trends but different values of the isotope raions among the sampling stations were observed in zooplankton, POM and sediment samples, indicationg the initial substances of the food chains were different at different parts of the lake.Article信州大学山地水環境教育研究センター研究報告 2: 21-24(2004)departmental bulletin pape

Isotopic evidence for the spatial heterogeneity of the planktonic food webs in the transition zone between river and lake ecosystems

Resources and organisms in food webs are distributed patchily. The spatial structure of food webs is important and critical to understanding their overall structure. However, there is little available information about the small-scale spatial structure of food webs. We investigated the spatial structure of food webs in a lake ecosystem at the littoral transition zone between an inflowing river and a lake. We measured the carbon isotope ratios of zooplankton and particulate organic matter (POM; predominantly phytoplankton) in the littoral zone of a saline lake. Parallel changes in the δ 13C values of zooplankton and their respective POMs indicated that there is spatial heterogeneity of the food web in this study area. Lake ecosystems are usually classified at the landscape level as either pelagic or littoral habitats. However, we showed small-scale spatial heterogeneity among planktonic food webs along an environmental gradient. Stable isotope data is useful for detecting spatial heterogeneity of habitats, populations, communities, and ecosystems

Low sulfur isotopic signatures (δ^<34>S) of macrozoobenthos from a brackish lagoon: contribution of microbially reduced sulfides

Stable sulfur isotope ratios (δ^S) of infaunal bivalves (Macoma contabulata, Nuttallia olivacea, and Ruditapes philippinarum) and polychaetes (Hediste spp.; consisted of H. atoka and H. diadroma) collected from two stations in the Gamo Lagoon (Japan) were determined to assess trophic pathways in highly reductive, estuarine soft-bottom habitats. The stations were characterized by distinctive sediment characteristics (Station A, sandy sediment with low sulfide content; Station B, muddy and sulfide-rich sediment). Soft tissues of the consumers exhibited much more depleted δ^S values (+3.2 to +12.1‰) than those of dissolved sulfate in the water column (+20.6 to +20.8‰). The value for each species was 1.6 to 5.3‰ lower at Station B than at Station A. These results suggest the assimilation of sulfides in the sediment (δ^S; -23.2 to -22.7‰) via microbial trophic pathways. In this lagoon, benthic microalgae and/or other microbes in the sediment are the most probable ^S-depleted food source for the consumers. Interspecies variations in δ^S values are explained by the different dietary contribution of the ^S-depleted diets versus ^S-enriched phytoplankton and are closely related to different feeding habits (i.e., surface-deposit feeding, facultative suspension feeding, and obligatory suspension feeding).論文Articl

ECOMICS: A Web-Based Toolkit for Investigating the Biomolecular Web in Ecosystems Using a Trans-omics Approach

Ecosystems can be conceptually thought of as interconnected environmental and metabolic systems, in which small molecules to macro-molecules interact through diverse networks. State-of-the-art technologies in post-genomic science offer ways to inspect and analyze this biomolecular web using omics-based approaches. Exploring useful genes and enzymes, as well as biomass resources responsible for anabolism and catabolism within ecosystems will contribute to a better understanding of environmental functions and their application to biotechnology. Here we present ECOMICS, a suite of web-based tools for ECosystem trans-OMICS investigation that target metagenomic, metatranscriptomic, and meta-metabolomic systems, including biomacromolecular mixtures derived from biomass. ECOMICS is made of four integrated webtools. E-class allows for the sequence-based taxonomic classification of eukaryotic and prokaryotic ribosomal data and the functional classification of selected enzymes. FT2B allows for the digital processing of NMR spectra for downstream metabolic or chemical phenotyping. Bm-Char allows for statistical assignment of specific compounds found in lignocellulose-based biomass, and HetMap is a data matrix generator and correlation calculator that can be applied to trans-omics datasets as analyzed by these and other web tools. This web suite is unique in that it allows for the monitoring of biomass metabolism in a particular environment, i.e., from macromolecular complexes (FT2DB and Bm-Char) to microbial composition and degradation (E-class), and makes possible the understanding of relationships between molecular and microbial elements (HetMap). This website is available to the public domain at: https://database.riken.jp/ecomics/

Anti-Siglec-15 antibody suppresses bone resorption by inhibiting osteoclast multinucleation without attenuating bone formation

Anti-resorptive drugs are widely used for the treatment of osteoporosis, but excessive inhibition of osteoclastogenesis can suppress bone turnover and cause the deterioration of bone quality. Sialic acid-binding immunoglobulin-like lectin 15 (Siglec-15) is a transmembrane protein expressed on osteoclast precursor cells and mature osteoclasts. Siglec-15 regulates proteins containing immunoreceptor tyrosine-based activation motif (ITAM) domains, which then induce nuclear factor of activated T-cells 1 (NFATc1), a master transcription factor of osteoclast differentiation. Anti-Siglec-15 antibody modulates ITAM signaling in osteoclast precursors and inhibits the maturation of osteoclasts in vitro. However, in situ pharmacological effects, particularly during postmenopausal osteoporosis, remain unclear. Here, we demonstrated that anti-Siglec-15 antibody treatment protected against ovariectomy-induced bone loss by specifically inhibiting the generation of multinucleated osteoclasts in vivo. Moreover, treatment with anti-Siglec-15 antibody maintained bone formation to a greater extent than with risedronate, the first-line treatment for osteoporosis. Intravital imaging revealed that anti-Siglec-15 antibody treatment did not cause a reduction in osteoclast motility, whereas osteoclast motility declined following risedronate treatment. We evaluated osteoclast activity using a pH-sensing probe and found that the bone resorptive ability of osteoclasts was lower following anti-Siglec-15 antibody treatment compared to after risedronate treatment. Our findings suggest that anti-Siglec-15 treatment may have potential as an anti-resorptive therapy for osteoporosis, which substantially inhibits the activity of osteoclasts while maintaining physiological bone coupling.Tsukazaki H., Kikuta J., Ao T., et al. Anti-Siglec-15 antibody suppresses bone resorption by inhibiting osteoclast multinucleation without attenuating bone formation. Bone 152, 116095 (2021); https://doi.org/10.1016/j.bone.2021.116095