Search results for " phytoplankton"
showing 7 items of 37 documents
Prvi nalazi dinoflagelata roda Dicroerisma (Actiniscales, Dinophyceae) na Sredozemnom moru
2011
This study is the first to describe and illustrate the dinoflagellate genus Dicroerisma in the Mediterranean Sea. Twenty individuals ascribed to Dicroerisma psilonereiella were encountered. The highest abundance (12 cells L-1) was recorded in the Balearic Sea at 50 m depth. Other specimens were found in subsurface waters (>75 m depth, with some records at 250 m depth) in the Ionian and Levantine Basin. These findings suggest that Dicroerisma is a widespread genus and its presence has gone unnoticed due to its small size, deep water distribution and misidentification with other gymnodinioid cells.
Functional classifications in phytoplankton ecology: a comparative review of approaches and experiences
2013
Empirical models of phytoplankton groups and their recurrence in water bodies have traditionally made use of taxonomic classifications, implicitly or explicitly assuming that species classified together could share similar ecological properties. Nevertheless, the use of taxonomy in ecology has many drawbacks. From one side, many broader groups include species with very different ecological properties. From the other side, convergent evolution, the independent evolution of similar characters in different lineages, can explain why distantly phylogenetically related species can be linked together by close analogous ecological affinities. With the aim to obtain a better understanding of the fun…
Bacterial and phytoplankton responses to nutrient amendments in a boreal lake differ according to season and to taxonomic resolution
2011
Nutrient limitation and resource competition in bacterial and phytoplankton communities may appear different when considering different levels of taxonomic resolution. Nutrient amendment experiments conducted in a boreal lake on three occasions during one open water season revealed complex responses in overall bacterioplankton and phytoplankton abundance and biovolume. In general, bacteria were dominant in spring, while phytoplankton was clearly the predominant group in autumn. Seasonal differences in the community composition of bacteria and phytoplankton were mainly related to changes in observed taxa, while the differences across nutrient treatments within an experiment were due to chang…
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…
Living Coccolithophores from the Gulf of Sirte (Southern Mediterranean Sea) during the summer of 2008
2012
The Gulf of Sirte is a largely unexplored area in the southernmost Mediterranean Sea.We are presenting here 2008 summer data on the distribution pattern of living coccolithophores, a main phytoplankton calcifying group, in 105 samples from 20 stations. The survey includes coastal and offshore stations, enabling us to provide indications on the dynamics of phytoplankton productivity in relation to oceanographic processes. The total coccosphere concentrations show higher values in the offshore stations and lower ones for coastal sites. Umbellosphaera tenuis, Emiliania huxleyi, Florisphaera profunda, Syracosphaera pulchra HOL (Calyptrosphaera oblonga) and Rhabdosphaera spp. dominate the assemb…
Inferring phytoplankton community composition with a fatty acid mixing model
2015
Abstract. The taxon specificity of fatty acid composition in algal classes suggests that fatty acids could be used as chemotaxonomic markers for phytoplankton composition. The applicability of phospholipid-derived fatty acids as chemotaxonomic markers for phytoplankton composition was evaluated by using a Bayesian fatty acid-based mixing model. Fatty acid profiles from monocultures of chlorophytes, cyanobacteria, diatoms, euglenoids, dinoflagellates, raphidophyte, cryptophytes and chrysophytes were used as a reference library to infer phytoplankton community composition in five moderately humic, large boreal lakes in three different seasons (spring, summer and fall). The phytoplankton commu…