Search results for "plank"
showing 10 items of 578 documents
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…
STUDY OF LARGE PELAGIC FISH LIFE-HISTORY TRAITS IN THE CENTRAL MEDITERRANEAN SEA AND PROJECTION UNDER FUTURE CLIMATE CHANGE SCENARIOS
2022
One of the most sensitive life periods for each species is the first life stages (larval and juvenile). The survival rates of pelagic fish larvae in these phases are usually very low and subject to fluctuations, consequently affecting the recruitment of new generations. From historical Tuna landing data, the stock's abundance is fluctuating, especially for Atlantic Bluefin Tuna (ABT) (Thunnus thynnus, Linnaeus, 1758) Eastern stock. It is the largest Mediterranean Tuna and one of the most expensive species in the world. Some studies hypothesized that the fluctuations are dictated by environmental factors, particularly in the early life stages. Therefore, it appears necessary to better unders…
Unveiling the Relationship Between Sea Surface Hydrographic Patterns and Tuna Larval Distribution in the Central Mediterranean Sea
2021
Thunnus thynnus (Atlantic bluefin tuna, ABT) and other tuna species reproduce in the Mediterranean Sea during the summer period. Despite the Central Mediterranean Sea, the Strait of Sicily in particular, being a key spawning site for many tuna species, little is known on the effects of oceanographic variability on their larval distribution in this area. The abundance and presence-absence of larval specimens for three tuna species (ABT, bullet tuna and albacore) were modeled in order to examine their relationships with environmental factors, by analysing historical in situ information collected during seven annual surveys (2010–2016). The results revealed that most tuna larvae for the three …