Search results for "plankton"
showing 10 items of 549 documents
Rīgas līča un Baltijas jūras zooplanktona daudzgadīgā dinamika un to kontrolējošie vides faktori
2005
Promocijas darbs – publikāciju kopsavilkums
2009
ANOTACIJA Mezozooplanktona struktura un funkcionala loma Baltijas juras piekrastes ekosistema Solvita Strake Zooplanktonam ir „atslegas” loma pelagiskaja bariba kede nodrošinot organisko vielu apriti starp fotosintezejošu vienšunas algi un augstakajiem trofiskas kedes limeniem ka, piemeram, komercialajai zvejai svarigakajam pelagisko zivju sugam. Lai gan atseviškos Baltijas juras rajonos tiek veikti ilggadigi zooplanktona noverojumi un analizetas datu rindas, tradicionalie monitoringa noverojumi neatbild uz daudziem ar zooplanktona ekologiju saistitiem jautajumiem. Darba merkis ir noskaidrot maz petitus Baltijas juras mezozooplanktona ekologijas jautajumus, lai izprastu ta lomu ekosistemas …
Plekstes (Platichthys flesus L) agrīno attīstības stadiju bioloģiskais raksturojums Baltijas jūras centrālajā daļā
2014
ANOTĀCIJA Ustups, 2013. Plekstes (Platichthys flesus L.) agrīno attīstības stadiju bioloģiskais raksturojums Baltijas jūras centrālajā daļā. Plekstu ihtioplanktona daudzumu Baltijas jūras centrālajā daļā nosaka nārsta bara lielums un hidroloģiskie apstākļi. Plekstu mazuļu skaitu piekrastes zonā būtiski ietekmē ūdens temperatūra, mēnesis un vēja virziens. Strauja šāgadeņu augšana novērojama līdz septembrim, bet viengadniekiem no pavasara līdz novembrim. Irbes šauruma piekraste ir labvēlīga dzīvotne plekstu mazuļiem, ko nosaka smilšainās seklūdens zonas, daudzveidīgie barošanās objekti un ģeogrāfiskais novietojums attiecībā pret nārsta vietu. Plekstes mazuļu plašais barības spektrs samazina b…
Modelling the impact of higher temperature on the phytoplankton of a boreal lake
2014
We linked the models PROTECH and MyLake to test potential impacts of climate-changeinduced warming on the phytoplankton community of Pyhäjärvi, a lake in southwest Finland. First, we calibrated the models for the present conditions, which revealed an apparent high significance of internal nutrient loading for Pyhäjärvi. We then estimated the effect of two climate change scenarios on lake water temperatures and ice cover duration with MyLake. Finally, we used those outputs to drive PROTECH to predict the resultant phytoplankton community. It was evident that cyanobacteria will grow significantly better in warmer water, especially in the summer. Even if phosphorus and nitrogen loads to the la…
Long-term dynamics of water-borne nitrogen, phosphorus and suspended solids in the lower Don River basin (Russian Federation)
2011
A long-term study (1986–2002) of water-borne nutrient and suspended solids dynamics was undertaken on the lower Don River, which plays an extremely important role in the water supply of the Black Sea and Azov Sea basin. Suspended solids were greatest in spring and summer and were correlated to river discharge. Mean annual nitrogen concentrations increased from 1986 to 1995 and then decreased from 1996 to 2002. Unlike nitrogen, phosphorus concentrations (both phosphates and total phosphorus) gradually increased throughout the study period changing the river from an oligotrophic to upper mesotrophic status. If this trend continues phytoplankton could become nitrogen-limited leading to the dev…
Linking nutrient limitation and water chemistry in upland lakes to catchment characteristics
2003
The relationship between catchment characteristics and lake water chemistry, phytoplankton and periphyton biomass, and phytoplankton and periphyton nutrient limitation was investigated for 30 upland lakes in the U.K. These catchment characteristics included the proportion of different land cover categories in the catchment and some hydrological information. Multiple regression models could predict alkalinity, pH, total dissolved phosphorus, dissolved inorganic nitrogen, dissolved organic nitrogen, dissolved organic carbon and phytoplankton chlorophyll a from the proportional contribution of between two and six land cover categories within the catchment and explain between 42 and 73% of the …
Trophic Status of the South-Eastern Baltic Sea: A Comparison of Coastal and Open Areas
2001
Primary production, nutrient concentrations, phytoplankton biomass (incl. chlorophyll a) and water transparency (Secchi depth), are important indicators of eutrophication. Earlier basin-wide primary production estimates for the Baltic Sea, a shallow shelf sea, were based mainly on open-sea data, neglecting the fundamentally different conditions in the large river plumes, which might have substantially higher production. Mean values of the period 1993–1997 of nutrient concentrations (phosphate, nitrate, ammonium and silicate), phytoplankton biomass, chlorophyll a (chl a) concentration, turbidity and primary production were calculated in the plumes of the rivers Oder, Vistula and Daugava and …
Nutrient dependence of phytoplankton production in brown-water lakes with special reference to Lake Päijänne
1982
A method for predicting the mean seasonal chlorophyll a concentration, the mean seasonal in vitro phytoplankton primary productivity per unit volume, the maximum daily production per unit volume and the seasonal integral production in brown-water lakes is presented. The production values can be calculated when the mean annual concentration of total phosphorus and the mean annual colour of the water are known. This method has been developed especially for practical water pollution studies to permit rapid and inexpensive estimates of major biological consequences of changes in effluent loads. The method can be applied for brown-water lakes where phosphorus is the limiting nutrient for primary…
Towards the development of a biogeochemical model for addressing the eutrophication problems in the shallow hypertrophic lagoon of Albufera de Valenc…
2015
Abstract Our study presents a biogeochemical model that aims to reproduce the ecological processes shaping phytoplankton dynamics in the shallow hypertrophic lagoon of Albufera de Valencia (Spain). The model simulates two elemental cycles (N and P), two phytoplankton groups (cyanobacteria and non-cyanobacteria), and heterotrophic bacteria. First, we examine the capacity to reproduce the observed plankton patterns, while accommodating the uncertainty related to the external forcing factors of our model (hydraulic and nutrient loading, zooplankton grazing). Sensitivity analysis is also performed to identify the most influential parameters and therefore to shed light on the knowledge needed to…
Contributions of autochthonous and allochthonous sources to dissolved organic matter in a large, shallow, eutrophic lake with a highly calcareous cat…
2013
We traced the origin of dissolved organic matter (DOM) in the large, shallow, eutrophic Lake Vortsjarv in Estonia. Allochthonous DOM (Al-DOM) had higher δ13C values than autochthonous DOM (Au-DOM). The δ13C of inflow DOM varied from −28.2‰ to −25.4‰ (mean −26.7‰) and in-lake DOM varied from −28.4‰ to −26.1‰ (mean −27.2‰). Low stable isotope (SI) signatures of Au-DOM were caused by relatively 13C-depleted values of its precursors (mainly phytoplankton) with mean δ13C of −28.9‰. SI signatures of dissolved inorganic carbon (DIC) in the inflows and in the lake were also relatively low (from −15.1‰ to −3.28‰). SI values of DOM were lower during the active growing season from May to September and…