Search results for "bloom"
showing 10 items of 65 documents
Spatial distribution of phytoplankton in the Gulf of Riga during spring and summer stages
1999
Distribution patterns of chlorophyll a, phytoplankton species and biomass were studied in the Gulf of Riga, one of the most eutrophicated areas of the Baltic Sea. Quasi-synoptic measurements were carried out during four seasonal stages (spring bloom 1995, early-summer stage 1994, cyanobacterial bloom 1994, and late summer stage 1993). For each stage, common factor analysis was used to simplify the highly correlated patterns of nutrients, salinity, temperature and the depth of mixed layer. Obtained latent variables were used to explain spatial distribution of phytoplankton. Generally, the distribution of phytoplankton variables followed closely the patterns of nutrient rich fresh water. Duri…
Distribution and seasonal dynamics of Cryptomonads in Sicilian water bodies
2003
Several species with a relevant ecological importance belong to Cryptophyta. Nevertheless, species-level identification from microscopic observations is problematic, lacking recent taxonomic keys. In this study we report our observations on distribution and seasonal dynamics of Cryptomonads in 33 Sicilian water bodies, as well as the main taxonomical problems we encountered. Species of the genera Cryptomonas and Plagioselmis are the most common in the examined water bodies. Their biomass seasonal trends usually show a peak in late winter and early spring. In advanced spring, and also in summer, due to the higher grazing pressure, the Cryptomonads biomass reaches its lowest values. Moreover,…
Konsolidācija Aktīvu pārvaldīšanas nozarē un ietekme uz darbības procesiem
2018
Finanšu pakalpojumu vide neapšaubāmi ir ļoti mainīga un tuvākajos gados Aktīvu Pārvaldes nozarē būs nopietnas radikālās izmaiņas. Regulatori un tehnoloģijas attīstība veicina finansiālu sistēmu uz lielajām pārmaiņām. Pēdējos gados palielinājās ieguldījumu plūsma kompānijām, kas izmanto vienīgu apstrādes programmu, ar apkopoto datu analīzi. Tajā mākslīgais intelekts palīdz interpretēt finansiālo informāciju. Ar minētajām izmaiņām aktīvu pārvaldes dalībniekiem būs jāveido virkne jaunu analītisko rīku, jo cilvēki nebūs spējīgi apstrādāt visus datus patstāvīgi. Esošais cilvēka un mašīnas līdzsvars, turpinās noliekties vairāk un vairāk uz mašīnas pusēs, kamēr cilvēks gandrīz pilnīgi būs aizvieto…
The role of native flower visitors in pollinating Opuntia ficus-indica (L.) Mill., naturalized in Sicily
2011
Abstract The role of insects in pollination and consequently in fruit set and quality was assessed in two commercial orchards of the cactus pear, Opuntia ficus-indica (L.) Mill., in Agrigento Province, Sicily. In 1997, insects visiting flowers were sampled during May–June (the first bloom) and July (the second bloom, induced by the “scozzolatura” practise). More than 50 insect species belonging to 10 orders were collected in May–June, while only five species of Hymenoptera Apoidea were collected in July. The quality of fruits arising from the second bloom showed that Hymenoptera alone were able to guarantee effective pollination. To verify the role of insects in pollination in 1996 (during …
Influence of climate on phytoplankton dynamics in Mediterranean water bodies
2011
Climate is among the factors that influence the hydrology of water bodies and their mixing/stratification patterns. As a consequence, it may affect the ecomorphological selection of phytoplankton. Global climatic patterns, driven by Sun’s magnetic field, were shown to promote cyclic cyanobacteria bloom during the years of drought caused by El Niño. Cyclic droughts, with a periodicity of about 11 years, also occur in the Mediterranean Basin where they produce analogous responses in phytoplankton composition. Some evidences exist that climate change can promote pseudo-eutrophication events and, by altering the hydraulic balance in shallow lakes, cause a shift between a clear macrophyte-domina…
Salinity effects on asexual reproduction of Carybdea sp. (Cnidaria: Cubozoa)
2014
6 pages, 2 figures, 1 table, supplementary data http://plankt.oxfordjournals.org/content/36/2/585/suppl/DC1
Classification et chronologie de bas fourneaux de réduction du fer à usage unique au sud-ouest du Niger
2016
In southwestern Niger, near Niamey, several thousand single-use bloomery furnaces have been mapped and identified. The archaeological study of approximately 30 furnaces and their slag reveals the existence of four methods for iron smelting: three types of pit furnace and one slag-tapping type. The slag pit furnaces are clearly differentiated by the form and volume of their pits. All slag-tapping furnaces drain off slag through small openings. The slag is tapped either vertically or laterally. According to radiocarbon dates, the smelting activity developed in the 2 nd century AD and intensified through to the 14 th century. It continued to evolve until the middle of the 20 th century. The lo…
Warmer climates boost cyanobacterial dominance in shallow lakes
2011
Dominance by cyanobacteria hampers human use of lakes and reservoirs worldwide. Previous studies indicate that excessive nutrient loading and warmer conditions promote dominance by cyanobacteria, but evidence from global scale field data has so far been scarce. Our analysis, based on a study of 143 lakes along a latitudinal transect ranging from subarctic Europe to southern South America, shows that although warmer climates do not result in higher overall phytoplankton biomass, the percentage of the total phytoplankton biovolume attributable to cyanobacteria increases steeply with temperature. Our results also reveal that the percent cyanobacteria is greater in lakes with high rates of ligh…
Diatom stratigraphy and long-term dissolved silica concentrations in the Baltic Sea
2008
Abstract In many parts of the world coastal waters with anthropogenic eutrophication have experienced a gradual depletion of dissolved silica (DSi) stocks. This could put pressure on spring bloom diatom populations, e.g. by limiting the intensity of blooms or by causing shifts in species composition. In addition, eutrophication driven enhanced diatom growth is responsible for the redistribution of DSi from the water phase to the sediments, and changes in the growth conditions may be reflected in the sediment diatom stratigraphy. To test for changes in diatom communities we have analyzed four sediment cores from the Baltic Sea covering approximately the last 100 years. The sediment cores ori…
A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins
2018
Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The Europea…