Search results for "Plankton"

Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments

2022

Light availability is the main regulator of primary production, shaping photosynthetic communities and their production of ecologically important biomolecules. In freshwater ecosystems, increasing dissolved organic carbon concentrations, commonly known as browning, leads to lower light availability and the proliferation of mixotrophic phytoplankton. Here, a mixotrophic algal species (Cryptomonas sp.) was grown under five increasing dissolved organic carbon concentrations to uncover the plastic responses behind the success of mixotrophs in browning environments and their effect in the availability of nutritionally important biomolecules. In addition to the browning treatments, phototrophic, …

Mikrozooplanktona biomasas izmaiņas atkarībā no vides faktoru sezonālās mainības un lokalizācijas Rīgas līcī

2019

Mikrozooplanktons ir nozīmīgs pelaģiskās barības ķēdes posms, jo tas savieno mikrobiālo barības ķēdi ar klasisko barības ķēdi. Tomēr tas nav ietverts jūras monitoringa programmā, un līdz ar to apsekots tiek periodiski, projektu un atsevišķu, nesaistītu pētījumu veidā. Kā rezultātā iztrūkst informācija par mikrozooplanktona populācijas sezonālo dinamiku, kā arī sugu sastāvu. Ekoloģiskie pētījumi saistībā ar vides faktoriem ir veikti atklātās Baltijas jūras rajonos un Rīgas līcī veikti 1980 un 1990 gados, tomēr sugu sastāvs Baltijas jūra aplūkots un aplūkots Baltijas jūras zooplanktona atlasā. Šī darba mērķis ir noskaidrot mikrozooplanktona biomasas izmaiņas Rīgas līcī pavasara, vasaras un ru…

Pohjaeläinten ravinnonkäyttö keskisuomalaisessa luusuakoskessa isotooppianalyysin avulla arvioituna

2009

Modelling phytoplankton in boreal lakes

2014

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…

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…

The influence of bacteria-dominated diets on Daphnia magna somatic growth, reproduction, and lipid composition

2012

We explored how dietary bacteria affect the life history traits and biochemical composition of Daphnia magna, using three bacteria taxa with very different lipid composition. Our objectives were to (1) examine whether and how bacteria-dominated diets affect Daphnia survival, growth, and fecundity, (2) see whether bacteria-specific fatty acid (FA) biomarkers accrued in Daphnia lipids, and (3) explore the quantitative relationship between bacteria availability in Daphnia diets and the amounts of bacterial FA in their lipids. Daphnia were fed monospecific and mixed diets of heterotrophic (Micrococcus luteus) or methanotrophic bacteria (Methylomonas methanica and Methylosinus trichosporium) and…

Distribution patterns of phytoplankton functional groups in connected/isolated reservoirs in an urban drinking water system

2015

Eighteen reservoirs belonging to an urban drinking water system (Zhuhai city, South China) were investigated in the dry and flood seasons of 2013 to evaluate how hydrological connectivity may affect the specie richness and functional composition of phytoplankton. Eleven among the studied water bodies are connected through pipelines and seven are isolated. Twenty one phytoplankton functional groups were identified in the studied reservoirs. Cluster analysis showed that phytoplankton similarity is higher among connected reservoirs than among isolated ones. The average α-diversity is high in the connected reservoirs, but the average β-diversity is much higher in the isolated reservoirs. The hi…

Variation in developmental mode and its effects on divergence and maintenance of populations

2012

Ravinteiden vaikutus vesikirpun (Daphnia longispina) loisintaan Mekkojärvellä

2010

Voimakkaasti humuksisessa Mekkojärvessä Daphnia longispina hallitsee järven eläinplanktonia läpi kesän. Daphnioiden kasvu hidastuu loppukesää kohti kasviplanktonin määrän vähetessä, ja ravinnosta jopa 73 % koostuu bakteeriplanktonista, jonka katsotaan olevan heikompi ravinnonlähde Daphnioille. Isännän ravitsemuksen laadulla voi olla joko positiivisia tai negatiivisia vaikutuksia vesikirpun loisintaan ja sen runsauteen. Lammin Mekkojärvellä selvitettiin ravinnelisäyksen välillistä vaikutusta vesikirppujen loisintaan kuuden viikon mittaisessa ravinnemanipulaatiokokeessa kuudessa mesokosmoksessa kesällä 2008. Kolme mesokosmosta sai viikottaisen epäorgaanisen typpi- ja fosforilisäyksen ja kolme…