1,720,998 research outputs found
A phytoplankton time series in the Northwestern Adriatic Sea: Structure and dynamics of the assemblages in a coastal ecosystem
No full textPhytoplankton assemblage structure was analyzed based on time series data (2008–2019) together with environmental variables in two coastal sites in the Northwestern Adriatic Sea. The main component of phytoplankton assemblage was the diatom group. Distinct seasonal and inter annual variations in the presence of taxa were observed within the phytoplankton assemblage over the study period. Mainly four taxa showed a non-random pattern in the binary time series, such as three diatoms Skeletonema marinoi, Thalassionema nitzschioides and Dactyliosolen fragilissimus, and undetermined Dinophyceae. S. marinoi was more frequent in winter and early spring, whereas T. nitzschioides showed an opposite pattern, being more frequent in late spring and summer. In both cases, deviation from randomness was caused by a clear and almost stationary annual cycle. On the contrary, deviation from randomness depended on the long-term trend of D. fragilissimus time series, as this diatom showed an increasing frequency of occurrence since 2016. A clear phytoplankton assemblage structure affected
by seasonal and environmental factors was observed. This was very evident for representative specie (i.e., S. marinoi associated with colder and rich nutrient waters or Heterocapsa niei and T. nitzschioides associated with high temperature and low nutrient conditions) and other species associated with various environmental parameters. Furthermore, the analysis of the association among phytoplankton taxa showed a partial and varied pattern. Our results highlight that phytoplankton time series showed changes in assemblage structure exhibiting a regular 12-month period affected by environmental factors. The long time series observations are important to understand the phytoplankton assemblage structure in relation to environmental changes and human pressures, crucial to achieving the Good Environmental Status in compliance to environmental directive
Quantification of G6PD in small and large intestine of rat during aging.
No full textNumerous studies have demonstrated a decrease in glucose-6-phosphate dehydrogenase (G6PD) activity during aging in many cell types, including red blood cells, fibroblasts and lens cells. Moreover, the intracellular activity of G6PD has been shown to be regulated by binding to cell organelles. To investigate whether binding of G6PD to cell organelles is related with the decrease in its activity during aging, distribution patterns of G6PD activity and protein were assessed in small (SI) and large (LI) intestine of 3-month-old and 28-month-old rats. Enzyme activity, as measured spectrophotometrically, did not show any significant change with aging in SI or LI. Enzyme histochemistry, performed by subtracting activity staining of 6-phosphogluconate dehydrogenase (6PGD) from that of G6PD, showed a lower net G6PD activity in SI and LI epithelium of old rats in comparison with young rats. G6PD activity did not change significantly with aging in the muscularis externa of SI and LI. Immunoelectr..
RNA/DNA ratios as estimate of metabolic and functional traits in diatom species from the northwestern Adriatic Sea
No full textDifferent phytoplankton biomass estimations can provide information about abundance variation, but they are not able to describe the metabolic
activity of species or groups within assemblages. Conversely, molecular traits are key for the metabolic dynamics in pelagic ecosystems. To
investigate if the RNA/DNA and taxon-specific 18S ribosomal RNA (rRNA)/ribosomal DNA (rDNA) ratios could be used to assess and be
indicators of metabolic activity in marine phytoplankton species, two Adriatic diatom species, Chaetoceros socialis and Skeletonema marinoi, were
studied. Significant correlations between abundance, chlorophyll a, carbon content and proteins were found in individual and co-cultured growth
experiments (from rs = 0.570 to rs = 0.986, P < 0.001). The biomass trend followed a logistic curve without providing additional information
regarding diatom metabolic activity. In both experiments, the RNA/DNA and taxon-specific 18S rRNA/rDNA ratios of C. socialis and S. marinoi
showed maximum values at the beginning of the growth phase, i.e as 23.2 ± 1.5 and 15.3 ± 0.8, and 16.2 ± 1.6 and 30.1 ± 5.4 after 2 and
6 days, respectively, in individual cultures, with a subsequent significant decrease in these values for both species in individual and co-culture
experiments. Our results showedthatthese molecular rRNA/rDNA ratios expressed an activation of metabolism beforethe abundance increases,
even in the presence of interspecific interaction between C. socialis and S. marinoi
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Long-term dynamics of annual and seasonal physical and biogeochemical properties: Role of minor river discharges in the North-western Adriatic coast
Full text linkDynamics of the physical and biogeochemical properties in a temperate coastal area in the north-western Adriatic Sea were analyzed. Multi-year (1997-2019) continuous observations allowed assessing their trends at two sites directly influenced by the discharges of two minor rivers as well as by human activities and climate change. Statistical models were applied to investigate the temporal variability and trends of seawater temperature, salinity, chlorophyll a, nutrients, river discharges and precipitations. The analysis highlighted a role for the minor river inputs and for ecological processes on interannual and seasonal biogeochemical dynamics. We found a significant trend toward more oligotrophic conditions; in particular, chlorophyll a exhibited a long-term decline (-1.38% year(-1) and -1.5% year(-1) at the two Foglia and Metauro river transects, respectively) that was largely determined by low phosphate and nitrate seawater concentrations as a result of a significant reduction in the phosphate and nitrate loadings of the two minor rivers (respectively mean values of-4.65% year(-1) and-2.65% year(-1)). In contrast, salinity showed a long-term decrease of-0.24% year(-1) and-0.19% year(-1) at Foglia and Metauro, respectively, corresponding to a significant increase of the freshwater discharges of the two minor rivers (+1.86% and +1.57% year(-1) at Foglia and Metauro, respectively) possibly due to precipitations. Data analysis highlighted the conditions of temperate coastal areas affected by freshwater discharges. Nutrient load management and climate conditions such as precipitation regimes appear to be the main factors driving physical and biogeochemical dynamics in the north-western Adriatic Sea
Influenza di differenti forme chimiche di silice disciolta sulla crescita di diatomee marine
No full textPhysical interactions between marine phytoplankton and PET plastics in seawater.
Full text linkPlastics are the most abundant marine debris globally dispersed in the oceans and its production is rising
with documented negative impacts in marine ecosystems. However, the chemical-physical and biological
interactions occurring between plastic and planktonic communities of different types of microorganisms
are poorly understood. In these respects, it is of paramount importance to understand, on a molecular
level on the surface, what happens to plastic fragments when dispersed in the ocean and directly
interacting with phytoplankton assemblages. This study presents a computer-aided analysis of electron
paramagnetic resonance (EPR) spectra of selected spin probes able to enter the phyoplanktonic cell
interface and interact with the plastic surface. Two different marine phytoplankton species were
analyzed, such as the diatom Skeletonema marinoi and dinoflagellate Lingulodinium polyedrum, in absence
and presence of polyethylene terephthalate (PET) fragments in synthetic seawater (ASPM), in order to insitu
characterize the interactions occurring between the microalgal cells and plastic surfaces. The analysis
was performed at increasing incubation times. The cellular growth and adhesion rates of microalgae in
batch culture medium and on the plastic fragments were also evaluated. The data agreed with the EPR
results, which showed a significant difference in terms of surface properties between the diatom and
dinoflagellate species. Low-polar interactions of lipid aggregates with the plastic surface sites were mainly responsible for the cell-plastic adhesion by S. marinoi, which is exponentially growing on the
plastic surface over the incubation time
DNA barcoding and phylogenetic relationships in marine toxic dinoflagellate genus Ostreopsis based on mithocondrial genes
Full text linkThe marine dinoflagellate genus Ostreopsis includes species producing potent toxic compounds, such as palytoxin and palytoxin analogs, which cause toxic blooms in Mediterranean and tropical or other temperate areas. Phylogenetic and phylogeographical analyses based on ribosomal data set revealed the existence of distinct species and, within them, clades related to geographical distribution. Due to a high morphological variability, species belonging to this genus are very difficult to identify and cryptic species could be present. Thus, developing a standardized DNA barcode approach for this marine dinoflagellate can allow confirming known species and uncover hidden variability with consequent description of new species. These information, besides leading to a better understanding of species diversity in natural environment, could assist in identification and detection of different species directly in field sample. This study represents the first attempt to assess the suitability of mitochondrial COI (cytochrome c oxidase 1) and cob (cytochrome b) as an identification tool for Ostreopsis species. For this purpose, we designed specific primers to amplify and sequence mitochondrial COI and cob genes from several Ostreopsis spp. isolates from worldwide areas. Phylogenetic analyses of single and concatenated mtDNA genes within genus Ostreopsis, as well as their intra and inter-specific divergences, were compared to those based on nuclear ribosomal genes LSU and 5.8S-ITS regions. Phylogenetic analyses of the genus Ostreopsis using mtDNA genes resulted uninformative, being not able to distinguish different species. Moreover, the so called 'barcode gap' that is interspecific variation exceeding intraspecific variation, was detected only in ribosomal genes. Thus, our original goal to apply the mtDNA barcode to recognize species within this toxic marine dinoflagellate was not accomplishe
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