Search results for "plankton"

Nitrogen sedimentation in a lake affected by massive nitrogen inputs: autochthonous versus allochthonous effects

2006

12 pages, and tables statics, and figures

Nutrient dynamics in water and sediment of Mediterranean ponds across a wide hydroperiod gradient

2012

Abstract In Mediterranean ponds, summer drought enhances seasonality whose intensity varies along topographic and climatic gradients. The alternation of wet and dry periods in rain dependent ponds affects their biogeochemistry and differentiates them from ponds fed by more stable water sources, such as groundwater springs. Superimposed onto this, land use is also a very strong factor of variability. In this study we compared nutrients and organic matter concentrations, in water and in sediment, among different types of Mediterranean ponds based on the source of water, hydroperiod and land use. Forty-three ponds were sampled in Eastern Spain corresponding to five pond types: (1) permanent sp…

Water-level fluctuations in Mediterranean reservoirs: Setting a dewatering threshold as a management tool to improve water quality

2005

Water-level fluctuations, often linked to seasonal climatic trends, are a natural phenomenon which occur in almost all aquatic ecosystems. In some climatic regions, as the Mediterranean one, they are particularly wide due to the occurrence of two well separated periods: the rainy winter and the almost completely dry summer. Precipitation is concentrated in the first period, whereas in the second strong evaporation losses take place. According to these climatic features, and to ensure a continuous supply of water throughout the year, man-made lakes store water during winter and are subjected to dewatering during summer to compensate the lack of precipitation. These ecosystems are thus charac…

The role of inorganic and organic nutrients on the development of phytoplankton along a transect from the Daugava River mouth to the Open Baltic, in …

2003

Abstract The importance of dissolved silicate (DSi), dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), phosphate and dissolved organic phosphorus (DOP) on algal growth is analysed for the Gulf of Riga and the adjacent open Baltic Sea. The results of three cruises (May, June, and July, 1999) along a transect across the Gulf of Riga from the entrance to the Daugava River to the open Baltic are presented. Nutrient-limitation was identified on the basis of available nutrient concentrations and stoichiometric analysis. In spring, phosphate appeared to be the algal-growth-potential-limiting nutrient at the entrance of the Daugava River, DSi in the central Gulf, and DIN at the …

Preface: Biogeography and spatial patterns of biodiversity of freshwater phytoplankton

2016

Long-Term Consequences of Water Pumping on the Ecosystem Functioning of Lake Sekšu, Latvia

2020

Cultural eutrophication, the process by which pollution due to human activity speeds up natural eutrophication, is a widespread and consequential issue. Here, we present the 85-year history of a small, initially Lobelia&ndash

Performance of surface and subsurface flow constructed wetlands treating eutrophic waters

2017

[EN] Three medium size constructed wetlands (CWs) with a total surface of 90 ha are working since 2009 in the Albufera de Valencia Natural Park (Spain). Two of them are fed with eutrophic waters from l'Albufera Lake. Their objectives are both reduce the phytoplankton biomass and increase the biodiversity; consequently, improved water quality is returned to the lake. A "science based governance" of these CWs is ongoing inside the LIFE + 12 Albufera Project to demonstrate the environmental benefits of these features. In this paper, results and relationships among hydraulic operation, physicochemical variables and plankton in two different CWs typologies, five free water surface CW (FWSCW) and…

Ilzas Geraņimovas ezera izpētes vēsture, kā arī planktona, it īpaši Ceratium hirundinella, rādītāji atkarībā no ezera posma un antropogēnās ietekmes …

2018

Ilzas Geraņimovas ezerā novērojamas ilgtermiņa ekosistēmas izmaiņas, kuru rezultātā, piemēram, kopš 1952. gada par ~ 4,5 ⁰C pakāpeniski paaugstinājusies hipolimnija temperatūra un par 15 mg/l pieaugusi kalcija koncentrācija. Ezers arī cieš no intensīva antropogēna punktveida un difūzā piesārņojuma. Tomēr, neskatoties uz novērotu tā ietekmi uz makrozoobentosu ūdenstilpes ZA galā, šī darba rezultāti neliecina par konkrētās ezera daļas planktona organismu galveno grupu negatīvu atbildi uz piesārņojumu, tomēr tajā vērojama, piemēram, trīs līdz piecas reizes zemāka zarūsaiņu koncentrācija. Līdzīgi, netika konstatēta arī fizikāli – ķīmisko mērījumu norāde uz potenciāli negatīviem dzīvotnes apstāk…

Calibration of in situ chlorophyll fluorometers for organic matter

2019

AbstractOrganic matter (OM) other than living phytoplankton is known to affect fluorometric in situ assessments of chlorophyll in lakes. For this reason, calibrating fluorometric measurements for OM error is important. In this study, chlorophyll (Chl) fluorescence was measured in situ in multiple Finnish lakes using two sondes equipped with Chl fluorometers (ex.470/em.650–700 nm). OM absorbance (A420) was measured from water samples, and one of the two sondes was also equipped with in situ fluorometer for OM (ex.350/em.430 nm). The sonde with Chl and OM fluorometers was also deployed continuously on an automated water quality monitoring station on Lake Konnevesi. For data from multiple lake…

Convergence and divergence in organization of phytoplankton communities under various regimes of physical and biological control

2010

The hypothesis that physical constraints may be as important, if not more important, than biological ones in shaping the structure of phytoplankton assemblage was tested by analyzing longterm (11–29 years) phytoplankton series in eight lakes and nine sites located along a latitudinal gradient in the Northern hemisphere. Phytoplankton biomass was used and similarity of assemblages in same months of the annual data sets was then calculated by subtracting the Bray–Curtis dissimilarity index from 1. The extent of biological and physical forcing was partly based on ‘‘expert evaluation’’: the importance of four physical (light availability, temperature, conductivity, and sediment stirring up) and…