Search results for "plankton"
showing 10 items of 549 documents
Saukas ezera fitoplanktona raksturojums
2022
Bakalaura darbs tika veikts saskaņā ar projekta “Latvijas upju baseinu apsaimniekošanas plānu ieviešana laba virszemes ūdens stāvokļa sasniegšanai” (LIFE GoodWater IP, 23 Nr. LIFE18IPE/LV/000014) ietvaros. Pētījuma mērķis bija izvērtēt Saukas ezera ekoloģisko stāvokli 2020. un 2021. gada vasarā pēc fitoplanktona kvantitatīvajiem un kvalitatīvajiem rādītājiem. 2020. gada fitoplanktona paraugos Saukas ezerā tika konstatētās 84 fitoplanktona sugas no septiņiem aļģu nodalījumiem. Jūlijā konstatētas augstākās fitoplanktona biomasas pateicoties kramaļģēm un zilaļģēm. 2021. gadā tika konstatētas 63 fitoplanktona sugas no astoņiem fitoplanktona nodalījumiem. Apsekotajās paraugošanas stacijās dominē…
Planktivorous vendace (Coregonus albula) utilise algae-derived fatty acids for biomass increase and lipid deposition
2018
Spatial and seasonal variation in the abundance and composition of phytoplankton and other basal resources (bacteria, terrestrial detritus) influence the availability of essen-tial polyunsaturated fatty acids (PUFA) for upper trophic levels in lake food webs. We studied accumulation, composition and content of fatty acids in planktivorous ven-dace (Coregonus albula) muscle tissue during the summer feeding period (May to late September) in six boreal lakes. Vendace muscle fatty acid content increased from ~17.7 mg/g DW to ~28.1 mg/g DW from spring to summer, corresponding to a ~59% increase in total fatty acids. PUFA accounted for 45%–65% of all fatty acids, and the most abundant fatty acid …
Differing Daphnia magna assimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids
2014
There is considerable interest in the pathways by which carbon and growthlimiting elemental and biochemical nutrients are supplied to upper trophic levels. Fatty acids and sterols are among the most important molecules transferred across the plant–animal interface of food webs. In lake ecosystems, in addition to phytoplankton, bacteria and terrestrial organic matter are potential trophic resources for zooplankton, especially in those receiving high terrestrial organic matter inputs. We therefore tested carbon, nitrogen, and fatty acid assimilation by the crustacean Daphnia magna when consuming these resources. We fed Daphnia with monospecific diets of high-quality (Cryptomonas marssonii) an…
Early Paleocene Paleoceanography and Export Productivity in the Chicxulub Crater
2021
The Chicxulub impact caused a crash in productivity in the world''s oceans which contributed to the extinction of ~75% of marine species. In the immediate aftermath of the extinction, export productivity was locally highly variable, with some sites, including the Chicxulub crater, recording elevated export production. The long-term transition back to more stable export productivity regimes has been poorly documented. Here, we present elemental abundances, foraminifer and calcareous nannoplankton assemblage counts, total organic carbon, and bulk carbonate carbon isotope data from the Chicxulub crater to reconstruct changes in export productivity during the first 3 Myr of the Paleocene. We sh…
Response of a shallow Mediterranean lake to nutrient diversion: does it follow similar patterns as in northern shallow lakes?
2005
Summary 1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long-term limnological data set to document changes in the food-web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L−1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents …
Food sources and lipid retention of zooplankton in subarctic ponds
2011
SUMMARY 1. Subarctic ponds are seasonal aquatic habitats subject to short summers but often have surprisingly numerous planktonic consumers relative to phytoplankton productivity. Because subarctic ponds have low pelagic productivity but a high biomass of benthic algae, we hypothesised that benthic mats provide a complementary and important food source for the zooplankton. To test this, we used a combination of fatty acid and stable isotope analyses to evaluate the nutritional content of benthic and pelagic food and their contributions to the diets of crustacean zooplankton in 10 Finnish subarctic ponds. 2. Benthic mats and seston differed significantly in total lipids, with seston (62.5 l …
A quantitative review of the lifestyle, habitat and trophic diversity of dinoflagellates (Dinoflagellata, Alveolata)
2012
This study reviews the trends in the lifestyle, habitat distribution and trophic diversity of the 2377 described species of dinoflagellates (Dinophyceae). Most of the dinoflagellates inhabit marine waters, whereas 17% of the total species have colonized continental waters. Dinoflagellates are dominated by planktonic species, while benthic forms represented 8% of the species. From the total number of species, 49% are heterotrophic (devoid of plastids), while 51% of the species have been reported with plastids (that does not strictly imply autotrophy). All the basal dinoflagellates (ellobiopsids, Duboscquodinida, Syndiniales) are heterotrophic, with the exception of a few Noctilucales (Spatul…
Seasonality of coastal phytoplankton in the Baltic Sea: Influence of salinity and eutrophication
2005
Abstract In this study long-term (1984–2001) phytoplankton and physico-chemical monitoring data representing different salinity regimes of the Baltic Sea were compiled from HELCOM, national and regional databases. The aim was to define seasonal succession patterns of phytoplankton in seven different areas of the Baltic sea, characterised by different salinity, climate, and trophic conditions and to delineate a set of phytoplankton community indicators that are independent of season and salinity, but indicative of trophic status of different coastal areas. The cluster analysis of the combined data set resulted in eight phytoplankton community types, common for all locations, and characterise…
Lipid-rich zooplankton subsidise the winter diet of benthivorous Arctic charr (Salvelinus alpinus) in a subarctic lake
2013
Summary Generalist fish species commonly act as important links between littoral and pelagic habitats and food-web compartments in lakes. However, diet and habitat links may depend significantly on seasonal availability of, and qualitative differences between, littoral and pelagic prey and on fish size. Despite increasing interest in food-web dynamics, little is known about the seasonal changes in, or qualitative differences between, littoral and pelagic trophic pathways supporting generalist fish species in high-latitude lakes. We used stomach contents together with analyses of stable carbon and nitrogen isotopes and fatty acids to study the winter and summer diet of generalist Arctic char…
A simple model relating habitat features to a diapause egg bank
2006
As a way to escape from adverse conditions, many zooplankton populations produce diapausing eggs that accumulate in the sediments and hatch when suitable environmental conditions are restored. While buried in the sediment, diapausing eggs may be affected by several processes (i.e., production, hatching, deterioration, and loss). We present a simple mathematical model for the dynamics of diapausing eggs in the sediment. We were mainly inspired by the model organism Brachionus plicatilis, a cyclical parthenogen rotifer, but the model is applicable to other zooplankters. Three diapausing egg categories are used as variables in our model: (1) healthy-looking eggs, assumed to represent the fract…