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[en] In this paper a model with two independent distributed delays is proposed to describe a population of microorganism feeding on a limiting nutrient which is supplied at a constant rate and is recycled after the death of the species by decomposer action. We obtain sufficient conditions for local and global stability of the positive equilibrium of the model. A fairly general function for nutrient uptake is considered. Stability changes of the positive equilibrium as the nutrient supply increases are studied by the Hopf bifurcation theorem
[en] An oil from Pacific krill (Euphausia pacifica) has a high content of PUFAs and phospholipids. The sediment was formed with homogenization of krill oil and maltodextrin (MD; dextrose equivalent (DE) = 19) solution using sodium caseinate, gum arabic, hydrolyzed whey protein or modified starch as a surfactant. Quillaja saponin could form the emulsion without the sediment. MD (28.5 wt%) was solubilized with distiller water (50 wt%) and mixed with krill oil (20wt%) and Quillaja saponin (1.5 wt%). The homogenized solution was spray-dried using Okawara-L8 spray dryer with a centrifugal atomizer. Spray-dried powder was evaluated in the oil-droplet size and surface-oil content. (Author)
[en] Highlights: • The size and profile of the International Seagrass Biology Workshop is increasing. • The rising profile of the workshop is in line with increase in attention for seagrass in the scientific community and media. • The next iteration of the workshop should consider more social science content. - Abstract: This conference report describes the programme of the 12th International Seagrass Biology Workshop, its highlights, areas of growth for the workshop, and potential future directions for the workshop series. The report is written with an eye toward where it fits within the field of seagrass research.
[en] This study was conducted to develop Korean seaweed soup as a space food and to evaluate the hygienic safety and storage stability of the irradiated dried seaweed soup. The values of pH and acidity of the gamma-irradiated seaweed soup less than 10 kGy were not changed. However, the redness (a value) and the yellowness (b value) of the freeze-dried seaweed soup increased as irradiation dose increased, while the Hunter's color of the samples irradiated less than 10 kGy was not significantly different (p>0.05). The hardness of seaweed irradiated over 10 kGy decreased as irradiation dose increased. The sensory evaluation result showed that the preference scores in all the sensory properties decreased when it was irradiated over 10 kGy, but sensory score of less than 10 kGy samples was similar in all terms. Therefore, it was considered that gamma irradiation at 10 kGy was enough to sterilize the freeze-dried seaweed soup without deterioration of sensory quality. Mutagenicity of the freeze-dried seaweed soup irradiated at 30 kGy, which is triple times of the optimum sterilization dose, was not observed. And, quality characteristics of the freeze-dried seaweed soup irradiated at 10 kGy were not significantly changed during the storage at various temperatures for 90 days (p>0.05)
[en] Thermal properties of brown seaweeds (Saccharina latissima) were determined using DSC technique in the temperature range between -150.0 and 50.0 °C. The following phase transitions were detected: glass transitions, incipient point of ice melting and freezing point. The ice content and amount of unfrozen water was detected by analysis of the melting peak. The ice content reduction in the product was predicted for different moisture contents and temperatures for atmospheric freeze-drying process. (Author)
[en] Highlights: • Degradation of seagrass ecosystems can reverse rapidly when conditions improve. • In other cases, seagrass loss is recalcitrant, or persists for many decades. • Ecosystem trajectory depends on timescales of disturbance, resistance and recovery. • Resistance and recovery capacity are quantified and compared for 12 seagrass genera. - Abstract: Seagrass ecosystems are inherently dynamic, responding to environmental change across a range of scales. Habitat requirements of seagrass are well defined, but less is known about their ability to resist disturbance. Specific means of recovery after loss are particularly difficult to quantify. Here we assess the resistance and recovery capacity of 12 seagrass genera. We document four classic trajectories of degradation and recovery for seagrass ecosystems, illustrated with examples from around the world. Recovery can be rapid once conditions improve, but seagrass absence at landscape scales may persist for many decades, perpetuated by feedbacks and/or lack of seed or plant propagules to initiate recovery. It can be difficult to distinguish between slow recovery, recalcitrant degradation, and the need for a window of opportunity to trigger recovery. We propose a framework synthesizing how the spatial and temporal scales of both disturbance and seagrass response affect ecosystem trajectory and hence resilience.
[en] The experimental Kislogubskaija Tidal power (KTP) was constructed in Russia near Murmansk in 1963-68. It began to produce electricity in 1974 and the water exchange between the bay and the open sea declined drastically. As a result, the upper 15 m layer of water was less saline, and the deeper 20 m of water contained hydrogen sulphide. The normal marine ecosystem was destroyed completely. Beginning in 1984 the water exchange with the open sea increased up to 30-40 %, which corresponds to the project regime. Marine ecosystems began slowly to be restored. In 1992-93 we did not find considerable differences in species composition.. The KTP case study helps to expose the most strong impact of TP on marine ecosystems, which probably could be avoided on big TP stations. (authors)
[en] At present, we are investigating the sorption of potentially toxic trace elements by phytoplankton under controlled laboratory conditions. Continuous culture techniques were used to study the mechanism of the sorption of the trace elements by unialgal diatom populations and the factors influencing this sorption. Continuous culture methodology has been used extensively to study bacterial kinetics. It is an excellent technique for obtaining a known physiological state of phytoplankton populations. An automated method for the synthesis of continuous culture medium for use in these experiments is described
[en] The effects of heat on the radiosensitivity of primordial germ cells at the quiescent stage in the fish Oryzias latipes were studied. The results show: (1) heat preceding but not following irradiation induced radioresistance which was reflected by improved survival; (2) its magnitude was a function of the heating time before irradiation; (3) improved germ-cell survival did not change with time for up to at least 4 hours after heat treatment at 410C for 30 min; (4) this resistance was more prominently expressed in the subsequent course of proliferation of female germ cells than in the non-proliferating male germ cells. In conclusion, heat induced radiation resistance in primordial germ cells of the female at the quiescent stage; this probably allows the cells subsequently to escape reproductive death. (author)