Search results for "marine ecosystem"

showing 3 items of 103 documents

A stochastic reaction-diffusion-taxis model for picophytoplankton dynamics

2011

The dynamics of picophytoplankton communities in marine environment is studied by astochastic reaction-dìffusìon-taxis model, analyzing the time evolution of the biomass concentration along a water column. The model is based on two stochastic differentìal equations, where the random fluctuations of the environmental variables are considered by inserting two multiplicative noise terms. Specifically, the model describes the dynamics of diffusion of picophytoplankton biomass and nutrient concentrations. In the proposed model the marine environment is characterized by poorly mixed waters and picophytoplankton is subject to intraspecific competition for light and nutrients. By numerically solvin…

marine ecosystemSpatial ecologyrandom processeSpatial ecology; marine ecosystems; phytoplankton dynamics; deep chlorophyll maximum; random processes; stochastic differential equationsdeep chlorophyll maximumphytoplankton dynamicstochastic differential equationsSettore FIS/07 - Fisica Applicata(Beni Culturali Ambientali Biol.e Medicin)
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A stochastic reaction-diffusion-taxis model for two picophytoplankton populations

2012

In this work, the stationary distributions of two populations of picophytoplankton, i.e. picoeukaryotes and Prochlorococcus, are studied. This two groups account on average for 60% of the total chlorophyll a (chl a) and divinil chlorophyll a (divinil chl a) concentration in Mediterranean Sea. The interaction of these populations with the environment occurs through two factors that limit the growth of the aquatic microorganisms: light intensity and nutrient, i.e. phosphorus. The dynamics of the two picophytoplanktonic groups, distributed at different depth along a water column (one-dimensional spatial domain), is analyzed starting from a deterministic reaction-diffusion-taxis model. This con…

marine ecosystemspatial ecologyspatial ecology; marine ecosystems; phytoplankton dynamics; deep chlorophyll maximum; random processes; stochastic differential equationsrandom processedeep chlorophyll maximumphytoplankton dynamicstochastic differential equationsSettore FIS/07 - Fisica Applicata(Beni Culturali Ambientali Biol.e Medicin)
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Sediment quality of the ecoregion Engure, Gulf of Riga, assessed by using ecotoxicity tests and biomarker responses

2014

Pētījuma mērķis bija novērtēt Engures ekoreģiona (Rīgas līča rietumu piekrastes) sedimentu kvalitāti, izmantojot sedimentu ekotoksicitātes testus. Lai noteiktu bioloģiskās atbildes reakcijas uz dažāda veida stresoriem, kā testorganismi pielietotas sānpeldes Monoporeia affinis and Pontogammarus robustoides, un izvēlēti biomarķieri (AChE, GST, GR, CAT, MT), kas noteikti gliemenēs Macoma balthica. Engures ekoreģionu varētu uzskatīt par nepiesārņotu rajonu, jo tā sedimentus raksturo salīdzinoši zemas smago metālu koncentrācijas. Engures ekoreģiona sedimentu ekotoksicitātes testu rezultāti neuzrādīja statistiski būtisku (>20% mirstība) toksisko efektu. Testorganismu izdzīvotība bija robežās no 8…

molluscsecotoxicity testsgeographyMultidisciplinarygeography.geographical_feature_categoryEcologyScienceGulf of RigaamphipodsQbiomarkersSedimentSink (geography):NATURAL SCIENCES::Biology [Research Subject Categories]NutrientEcoregionEnvironmental scienceMarine ecosystemEcosystemgulf of rigaEcotoxicityOrganismProceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences.
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