CyanoNews (Vol. 10, No. 1, February 1994)

CyanoNews was a newsletter that served the cyanobacteriological community from 1985 to 2003, with content provided by readers (sort of a blog before there were blogs). The newsletter reported new findings from the lab, summaries of recent meetings (often provided by graduate students and post-docs entering the field), positions sought or available, life transitions, a compendium of recent cyanobacteria-related articles, and other items of interest to those who study cyanobacteria

CyanoNews (Vol. 12, No. 1, January 1996)

CyanoNews was a newsletter that served the cyanobacteriological community from 1985 to 2003, with content provided by readers (sort of a blog before there were blogs). The newsletter reported new findings from the lab, summaries of recent meetings (often provided by graduate students and post-docs entering the field), positions sought or available, life transitions, a compendium of recent cyanobacteria-related articles, and other items of interest to those who study cyanobacteria

Simulating Behavioral Microcystin Impairment in Fish

Fish experiencing blooms of the cyanobacteria genera Microcystis and Anabaena acquire microcystin and saxitoxin through ingestion of contaminated food and absorption of dissolved toxin. Even low chronic doses induce sensory and motor impairment—the impact of which is unquantified in wild populations. Here, I introduce Lagrangian particle models for cyanobacteria and fish which test the hypotheses that impairment symptoms suppress movement and growth. This is implemented within the Finite-Volume Coastal Ocean Model (FVCOM). Cyanobacteria particles move vertically according to mixing and buoyancy (a function of cellular reservoirs). Fish navigate the horizontal domain, foraging in high growth areas, and fleeing when toxin increases. The framework is demonstrated here for the case of juvenile fish encountering Microcystis aeruginosa in an idealized Louisiana estuary. Self-shading reduces bloom growth, and causes algae to collect at the surface. Turbulent diffusivity is insufficient to break up this layer, so dissolved toxin becomes surface-intensified. Fish seek high growth areas in this environment, and dietary uptake increases. This triggers flight and swimming impairment. As cyanobacteria excrete microcystin, absorption forces fish to become intoxicated even in areas of lower toxic risk. Repeated flight means fish spend more time in suboptimal areas, with final growth reduced up to 6.6%. In vivo, this would be exacerbated by physiological stress and the metabolic cost of toxin removal. Collective movement (group diffusivity) is suppressed nearly 50% during wide-spread intoxication. Simulations show that within a certain parameter space, both movement and growth are suppressed relative to the control case as expected. However, additional experiments resulted in higher growth, indicating the methods are sensitive to model parameterization. Ultimately, these are sandbox cases, which will require carefully-designed lab and field experiments before predictive capability can be assumed

\u3ci\u3eTrichodesmium\u3c/i\u3e spp.: Numerical Studies of Resource Competition, Carbohydrate Ballasting, and Remote-Sensing Reflectance

In recent years, a new appreciation for the role of diazotrophy in the oceans has emerged. This dissertation reports on three modeling studies designed to investigate ecological processes associated with Trichodesmium spp., the most conspicuous marine diazotroph: (1) characterization of a generalized model Trichodesmium and issues of macronutrient resource competition; (2) carbohydrate ballasting by Trchodesmium and implications for the formation of surface accumulations; and (3) the vertical distribution of Trichodesmium and implications for detection from space. The first study focuses on issues of nitrogen and phosphorus competition and ecosystem structure. It utilizes a simple ecosystem model that includes dissolved nitrogen and phosphorus plus two classes each of primary producers, grazers, and particulate detritus. In a monoculture submodel, the Trichodesmium biomass is most sensitive to the nitrogen: phosphorus compositional ratio and the senescence and gross growth rates. In the competitive model, Trichodesmium is adversely affected by competitors for model phosphorus, while the contribution of diazotrophy to fueling non-diazotrophy new production is limited by the concomitant lack of other nutrients. This model\u27s outcome is most sensitive to the Trichodesmium gross growth and senescence rates. Experimental studies that would be particularly useful in this context include determination of the Trichodesmium half-saturation coefficient for phosphate, as well as quantitative co-occurrence data for Trichodesmium and Macrosetella gracilis. In the second study, an individual-based Lagrangian model is used to explore carbohydrate ballasting and its implications for Trichodesmium vertical distribution in quiescent waters. The model results indicate that mean population depth is controlled primarily by environmental conditions (incident irradiance and its vertical attenuation) and physiological rate parameters for ballast processes. Morphologic parameters have a greater effect on the amplitude of ballast-driven oscillations. Post-mixing quiescence, high incident irradiance, and high water clarity all encourage the formation of surface accumulations. Post-mixing quiescence produces a depth-segregated population, with the proportion ascending to the surface increasing as a function of water-column turbidity. This study provides insight into environmental and biological conditions that encourage Trichodesmium accumulation at the marine boundary layer and identifies key processes for further study. In the third study, a radiative transfer model is used to quantify the effects of Trichodesmium vertical distribution on remote-sensing reflectance, Rrs(λ). For the detection thresholds employed here, the model results indicate that surface accumulations of Trichodesmium can be detected when chlorophyll ≥1.5 mg m−3. For near-surface populations, R rs is most sensitive to chlorophyll concentration. For populations at 10–20 m depth, Rrs is most sensitive to population depth. Populations deeper than 20 m are not detected. These results, in conjunction with recent field surveys, indicate a detection rate of approximately 25%. These results have implications for ocean-color sensor and algorithm development and may have direct application to satellite estimations of N2-fixation. In summary, these three modeling studies confirm the importance of Trichodesmium in marine ecosystems. Moreover, these studies identify critical areas in which future research is required for illumination of the role of Trichodesmium in elemental cycling and marine ecosystems

ビワコ ニ オケル アオコ オ ケイセイスル ランソウルイ ノ ドウタイ

京都大学0048新制・論文博士博士(農学)乙第11065号論農博第2447号新制||農||857(附属図書館)学位論文||H14||N3734(農学部図書室)UT51-2003-B427(主査)教授 中原 紘之, 教授 坂本 亘, 教授 内田 有恆学位規則第4条第2項該当Doctor of Agricultural ScienceKyoto UniversityDFA