43 research outputs found
Quantitative relationship among phytoplankton body size classes and production processes in the North Adriatic Frontal region
No full textSeasonal characteristics of size-fractionated phytoplankton community and fate of photosynthesized carbon in a sub-antarctic area (Straits of Magellan)
No full textPhytoplankton community size drives the rates of biogenic carbon and the overall structure and dynamics of the marine pelagic food web. The Straits of Magellan, an inland passage between the Pacific and Atlantic Oceans, can be separated in three main sub-basin: the western-Pacific, the V-shaped central zone, and the eastern-Atlantic. To provide insights on the food structure of the phytoplankton community, size-fractionated chlorophyll a concentration and primary production rates were measured across the three sectors of the Magellan Straits in four periods between 1989 and 1995 in the Straits. Phytoplanktonic biomass and production ratios provided ecological insights on the food web structure, including the relevance of grazing on its largest fraction.
The micro-phytoplanktonic fraction (>10 μm) in the western-Pacific sub-basin is significantly less abundant than in the Central and Atlantic ones. Conversely, the lowest abundance of the pico- fraction (< 2.0 μm) is encountered in the Atlantic sub-basin. The observed patterns agree with the diffusion of smaller-size fractions from the western towards the easternmost sector of the Straits, and suggest that the largest phytoplankton tend to accumulate in the inner stretch of the Straits, being constrained by a clockwise gyre generated by tidal phases or partialy spilling out into the Atlantic sector. The most active grazing activities occur in the central arm during the spring bloom and last even in summer.
Our results pinpoint also that the basic levels of the planktonic food web rely on the nano-phytoplankton (10-2 μm) fraction, which is the main contributor to the continuum multivorous food web. When nutrient pulses from land freshwater and water mixing enter the system, the structure of the plankton in the Straits shifts towards the herbivorous food web and is characterized by the presence of large-size diatoms. The complex dynamics of the plankton comuunities in the Straits keep it in a persistent mesotrophic state, featuring a lower trophic status of than the Antarctic coastal waters but a much higher one than oligotrophic temperate areas
I SEGRETI DEL CLIMA NEI FONDALI DEL TIRRENO
No full textLe recenti campagne oceanografiche fotografano il fenomeno di tropicalizzazione in atto nel Mediterraneo e i rischi per la biodiversità delle montagne sommers
Dicer inactivation causes heterochronic retinogenesis in Xenopus laevis
No full textMaturation of miRNAs by dicer is required in vertebrates for normal neural development. Here we report that dicer inactivation in Xenopus affects cell cycle progression, survival and timing of the generation of retinal cells, resulting in small retinas with lamination defects. In particular, dicer inactivation delays the exit from the cell cycle and the translation of key genes of late neurogenesis, highlighting a crucial role of miRNAs in retinal development
Biochemical processes, trophic status and water mass chracteristics in the Gulf of Manfredonia (Southern Adriatic Sea)
No full textThe dark portion of the Mediterranean Sea is a bioreactor of organic matter cycling
No full textTotal prokaryotic abundance, prokaryotic heterotrophic production and enzymatic activities were investigated in epi-, meso- and bathypelagic waters along a longitudinal transect covering the entire Mediterranean Sea. The prokaryotic production and enzymatic activities in deep waters were among the highest reported worldwide at similar depths, indicating that the peculiar physico-chemical characteristics of the Mediterranean Sea, characterized by warm temperatures (typically 13°C also at abyssal depths), support high rates of organic carbon degradation and incorporation by prokaryotic assemblages. The higher trophic conditions in the epipelagic waters of the Western basin resulted in significantly higher prokaryotic production and enzymatic activities rates than in the Central-Eastern basin. While all of the variables decreased significantly from epi- to meso- and bathypelagic waters, cell-specific hydrolytic activity and cell-specific carbon production significantly increased. In addition, the deep-water layers were characterised by low half-saturation constants (Km) of all enzymatic activities. These findings suggest that prokaryotic assemblages inhabiting the dark portion of the Mediterranean Sea are able to channel degraded carbon into biomass in a very efficient way, and that prokaryotic assemblages of the deep Mediterranean waters work as a “bioreactor” of organic matter cycling. Since prokaryotic production and enzymatic activities in deep water masses were inversely related with oxygen concentration, we hypothesise a tight link between prokaryotic metabolism and oxygen consumption. As climate change is increasing deep-water temperatures, the predicted positive response of prokaryotic metabolism to temperature increases may accelerate oxygen depletion of deep Mediterranean waters, with cascade consequences on carbon cycling and biogeochemical processes on the entire deep basin
Group in front of the Kootenay Hotel
No full textBack, from left: Rizieri Matteucci, Aladino Fianini, Primo Fantin, Antonio Magliani, C. Giannini (Mia), S. Paolone (Baboletta). Middle: G Cristofoli (Tita), F. Decembrini), Gino Nutini, Guilio Nutini, R. Cecconi. Front: Battista DePaolis, Pietro Gianni, Slim, Armando Vellutini. Kids: Nick Decembrini, John Decembrini, Bruno Vanell
Assessment of the ecological status of transitional waters in Sicily (Italy): First characterisation and classification according to a multiparametric approach
No full textA 1-year cycle of observations was performed in four Sicilian transitional water systems (Oliveri-Tindari,
Cape Peloro, Vendicari and Marsala) to characterise their ecological status. A panel of variables among
which trophic and microbial (enzyme activities, abundance of hetetrophic bacteria and of bacterial pollution
indicators) parameters, were selected. Particulate organic carbon (POC) and nitrogen (PON) and
chlorophyll-a (Chl-a) contents defined the trophic state, while microbial hydrolysis rates and abundance
gave insights on microbial community efficiency in organic matter transformation and on allochthonous
inputs. To classify the trophic state of examined waters, the synthetic trophic state index (TRIX) was calculated.
Microbial hydrolysis rates correlated positively with POC and Chl-a, which increased along the eutrophication
gradient. The significant relationships among TRIX, trophic and microbial parameters suggested
the use of leucine aminopeptidase, alkaline phosphatase and POC as suitable parameters to implement
the Water Framework Directive when assessing the ecological status of transitional water systems
Penetration of solar radiation into waters of Messina Strait (Italy)
No full textThe optical properties of the waters of five different stations, three located in the Messina Strait and two near the Strait (open sea), were analysed. Direct spectral measurements of the downward solar irradiance (290 - 800 nm) at different depths (0.5 m, 7 m, 10 m, 13 m, 20 m) were made using a cosine sensor connected to a spectroradiometer. Water samples were collected in the surface layer and their absorption spectra were analysed. The natural fluorescence profiles, along the water column, were determined using a fluorometer (SBE 911 plus - Sea Teach). The spectral attenuation coefficient (K-lambda), the variation of K-lambda in different wavelength ranges (Delta K-Delta lambda), the wavelength corresponding to minimum value of K-lambda, the spectral depths of penetration of both 1% and 10% of the sub-surface irradiance values (P-lambda), the depths of 1% of penetration of UVB, UVA and PAR, the depth ranges of the maxim concentration of Chl a and superficial CDOM were measured at each station. The maximum solar UVB penetration was about 65% of the photic zone and the maximum UVA penetration was nearly 100% (data of the Ionic sea station). Thus, a large part of the photic zone was exposed to UV radiation sufficient to cause a possible reduction in the photosynthetic activity of phytoplankton. The spectral penetration of solar radiation, especially UVB radiation, was significantly different in the three stations of the Strait with respect to the two stations studied in the open sea. This shows that variations in the spectral attenuation along the water column can be used as an indicator of properties of the water body
