Поиск по автору "Williams, R."
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Материал Identification of small-scale structure of plankton communities of the Black and Ionian Seas by their bioluminescence characteristics(1999) Tokarev, Yu. N.; Williams, R.; Piontkovski, S. A.Small-scale heterogeneity of bioluminescence intensity was studied in offshore regions of the Black and Ionian Seas in September/October, 1989. Bathyphotometric casts were deployed every 3 min over a period of several hours from a drifting vessel. Casts were accompanied by temperature profiles and zooplankton sampling. Taking into account the vessel drift, the sampling interval was equal to a spatial resolution from 15 to 25 m. Measurements were carried out during the day and night periods. From adaptive spectral analysis it was shown that the horizontal dimensions of the bioluminescent heterogeneities were between 75 and 1500 m in the Black Sea and 89–800 m in the Ionian Sea. The horizontal dimensions of the heterogeneities were 85–818 m and 85–500 m for zooplankton biomass and 80–1800 m and 85–600 m for the temperature field in the Black and Ionian Seas, respectively. Therefore, it is assumed that physical and dynamical factors dominate in the formation of small-scale spatial heterogeneity of the studied fields. Biological factors, such as diel vertical migrations, trophic interactions etc. will also contribute to the formation of patches at night.Материал Influence of seamounts at the Atlantic Ocean on modification of the bioluminescence and plankton characteristics(2003) Tokarev, Yu. N.; Bityukov, E. P.; Williams, R.The bioluminescence and plankton characteristics in the euphotic layer over 11 seamounts in the Atlantic Ocean were studied. Investigations were carried out along the axis of flow over the mounts. Bathyphotometric measurements (1606 casts) were taken from 2 m to 100 m depths at 87 stations over the various seamounts with a vertical resolution of 1 m. Plankton samples were taken with Juday nets and submersible electric pumps with 36 m 3•h -1 performance. The bioluminescence characteristics varied over seamounts with different geomorphologicalfeatures. The hydrodynamic gyres, created by the bottom elevations, and the upwelling of water with biogenic elements, also seem to have effects on the quantitative characteristics of the plankton. The largest changes in the structure and intensity of the bioluminescence field were observed in the regions of large geomorphological formations. For example, over mountains at greater depth in the North Atlantic Ocean (Slozhnaya, Mayskaya, Hecate sea mounts) changes were observed between 5 and 16 km from their peaks, while in the regions of comparatively shallow bank, such as Valdivia, changes were seen up to distances of 100 km. The influence of sharppicks sea mounts (Meteor and Irving, Udachnaya bank) on the bioluminescence field and distribution of plankton was not so evident. For example, the effects of the Meteor and Irving mountains were observed only over their peaks, with the intensity of bioluminescence exceeding the background levels by 1.5 to 3 times. The same effect was observed over the Udachnaya bank that was being characterised by higher productivity. In the region of Valdivia bank, which has a depth similar to the Meteor and Irving sea mounts (about 250 m) the bioluminescence intensity, in the upper 100 m layer increased over 20 times if compared with the open ocean.Материал Phytoplankton carbon to chlorophyll a ratio: response to light, temperature and nutrient limitation(2003) Finenko, Z. Z.; Hoepffner, N.; Williams, R.; Piontkovski, S. A.A review was carried out on the effects of light, temperature and nutrient limitation on the carbon to chlorophyll a ratios of 36 microalgae species from 7 taxonomic groups using the literature and our own experimental data. Under similar conditions the C:Chl a ratio for individual taxonomic groups increase in the order: Chlorophyceae < Bacillariophyceae, Prochlorococcus < Prymnesiophyceae < Cyanophyceae < Dinophyceae. At constant temperature, the C:Chl a ratio increases linearly as light increases and decreases exponentially as temperature grows at constant light level. The combined effect of irradiance and temperature on C:Chl a ratio is described using an equation with 3 coefficients. From the empirical equation a decrease in the light levels causes a decrease in the effect of temperature on the C:Chl a ratio. In all algae groups studied different light levels increases the C:Chl a ratio in the same way under nutrient limitation. Taking into account, the taxonomy of the phytoplankton, nutrient limitation of phytoplankton growth rate, temperature and light intensity the C:Chl a ratio within the mixed layer in the oligo-, meso- and eutrophic waters of the tropical Atlantic Ocean was 145, 96 and 37 gC gChl a-1 respectively. Near the base of the euphotic zone the ratio was 30 gC gChl a-1. From the developed equation the C:Chl a ratios in phytoplankton under different environment conditions can be described.Материал Spatial heterogeneity of the bioluminescent field of the tropical Atlantic Ocean and its relationship with internal waves(1997) Kushnir, V. M.; Tokarev, Yu. N.; Williams, R.; Piontkovski, S. A.; Evstigneev, P. V.Материал Spatial heterogeneity, biomass and size structure of plankton of the Indian Ocean: some general trends(1995) Piontkovski, S. A.; Williams, R.; Melnik, T. A.Data from surveys carried out in 1982 and 1990 in the Arabian Sea, and the South and North Sub-equatorial Divergence regions of the Indian Ocean were used to analyse the spatial distribution and the size spectra of zooplankton in relation to primary production and hydrophysical dynamics on a scale of hundreds of kilometres. Spatial heterogeneity of biomass distributions increased with the size of organisms from phytoplankton to macrozooplankton The zooplankton abundance spectra changed with hydrodynamic regimes of water dynamics (cyclonic, anticyclonic eddies, frontal zones) and could be approximated by linear regressions in logarithmic scale. From values of the normalised spatial variance of plankton biomass components (phyto-, meso-, macroplankton) it is concluded that heterogeneous 'fields' of predators exist on more uniform 'fields' of prey. Biomass ratios of phytoplankton (chlorophyll a), microzoo-, mesozoo- and macrozooplankton form an inverted pyramid of biomass in the studied regions. Maximal slopes for zooplankton abundance size spectra have been observed in regions of maximum pnmary production, i.e in regions of high primary production the smallest zooplankton dominate the total zooplankton. This is also true for regions of high phytoplankton turnover. The ratio of primary production to herbivore production indicates that the highest efficiency of transfer from autotrophs to heterotrophs is carried out by the smaller zooplankton. The ratio of pnmary production to zooplankton biomass increases as the spectrum slope of the zooplankton abundance increases. This means that the ratio increases when small mesoplanktonic organisms become more dominant amongst the mesoplankton size range. Both types of relationships can be approximated by diminishing non-linear equations. The values of these 2 ratios can change an order of magnitude on a scale of hundreds of kilometres.Материал The Bioluminescence Field as an Indicator of the Spatial Structure and Physiological State of the Plankton Community at the Mediterranean Sea Basin(1999) Tokarev, Yu. N.; Bitukov, E. P.; Williams, R.; Vasilenko, V. I.; Piontkovski, S. A.; Sokolov, B. G.Материал The Bioluminescent field of the Atlantic Ocean(1997) Piontkovski, S. A.; Tokarev, Yu. N.; Bitukov, E. P.; Williams, R.; Kiefer, D. A.Материал Динамика характеристик поля биолюминесценции и планктона в восточной Атлантике в зимний период(2003) Токарев, Ю. Н.; Битюков, Э. П.; Василенко, В. И.; Вильямс, Р.; Слипецкий, Д. Я.; Соколов, Б. Г.Исследовано влияние гидрологических параметров водных масс, видового состава и обилия планктона на пространственную изменчивость амплитудных характеристик поля биолюминесценции вдоль 20° з.д. в Атлантическом океане. Показано, что вертикальное распределение интенсивности поля биолюминесценции коррелирует с количественным развитием фито- и зоопланктона, распределение которых обусловлено концентрацией биогенных элементов и вертикальной структурированностью основных гидрофизических характеристик. Предложено использовать результаты анализа пространственной структуры и амплитудно-временной изменчивости биолюминесценции в различных климатических зонах восточной части Атлантического океана для визуализации вертикальной структуры планктонного сообщества и проведения экспресс-типизации водных масс.