Search results for " SEA"

Meiofauna and benthic microbial biomass in a semi-enclosed mediterranean marine system (Stagnone di Marsala, Italy)

2004

Microbial and meiofaunal dynamics and their relationships with the biochemical composition of the sedimentary organic matter were investigated in a semi-enclosed marine system (Marsala lagoon, Western Sicily, Mediterranean Sea). Sediment samples were collected on a monthly basis from March 1996 to February 1997 in four stations located along a N–S transect characterized by different hydrodynamic regimes. Total sedimentary organic matter concentration ranged from 5.681.11 to 156.2812.63 mg g1, while the biopolymeric fraction of organic carbon (BPC, measured as sum of the lipids, carbohydrates and proteins) accounted for only a small fraction (24%) of total organic matter. Total meiofaunal de…

Holothuria tubulosa Gmelin 1791 (Holothuroidea, Echinodermata) enhances organic matter recycling in Posidonia oceanica meadows

2014

Abstract The role of Holothuria tubulosa in organic matter recycling of Posidonia oceanica detritus was estimated in a laboratory feeding experiment. The individual mean ingestion rate of seagrass detritus by holothurians was evaluated and carbon and nitrogen stable isotopes, carbon and nitrogen content and C:N ratio analyzed in H. tubulosa , P. oceanica detritus and surface sediment. Results showed that H. tubulosa is capable of ingesting from 30% to 100% of the detritus produced by P. oceanica meadows, depending on the holothurian density. Stable isotope analysis provided evidence for the assimilation of seagrass detritus by H. tubulosa as their signatures were compatible with 1 trophic l…

Speciation of trialkyltin(IV) cations in natural fluids

2004

The hydrolysis of (CH(3))(3)Sn(+), (C(2)H(5))(3)Sn(+) and (C(3)H(7))(3)Sn(+) has been studied in a Synthetic Seawater (SSW) ionic medium simulating the major composition of natural seawater, at different salinities (5 less than or equal to S less than or equal to 45), and at t = 25 degreesC. Interactions with anionic components of SSW, considered as single sea salt, are determined by means of a complex formation model. By potentiometric measurements (ISE-H(+) and ISE-F(-) electrodes), the model has been extended to also consider interactions of organotins with carbonate and fluoride ions, which are other important components of seawater. Literature and new values of hydrolysis constants in …

Paleoenvironmental and climatic changes during the last 25 ky along a W-E transect across the Mediterranean Sea.

2012

Quantitative identification, distribution and source apportionment of anthropogenic trace metals in marine sediment of Milazzo gulf (N-E Sicily): pre…

2009

Mediterranean coccolith ecobiostratigraphy since the penultimate Glacial (the last 145,000years) and ecobioevent traceability

2015

The Mediterranean Sea is a miniature ocean ideal to test the response of marine ecosystems to amplified orbital and suborbital climate changes. Here we present coccolith data from a Sardinia Channel gravity core (Arcose C_33) analysed over the last 145,000 years, with a mean resolution of about 900 years. The study highlights that regional phytoplankton assemblages underwent significant modifications between the penultimate glacial and the last interglacial, as well as between the last glacial and the Holocene. The N ratio palaeoproductivity index suggests reduced productivity levels and the development of a deep nutricline during the last interglacial and the Holocene. Within the last glac…

Risposte agli stress ambientali in CYSTOSEIRA (C. AGARDH): effetti della temperatura sul contenuto dei composti fenolici

2012

Phenolic compounds are secondary metabolites involved in different protection mechanisms as, for example, against grazers, epiphytes and UV radiation. Seasonal variations of phenolic content in C. amentacea were analysed and laboratory experiments, in which C. amentacea was exposed to an increase of temperature (258C and 308C), were performed. Total phenolic content (TPC) was determined colorimetrically with the Folin–Ciocalteu reagent. In C. amentacea, a seasonal pattern in TPC was observed, with a maximum value in winter-spring. C. amentacea responded significantly to the temperature treatments with a consistent decrease in TPC after 48 h.

The land bridge between Europe and Sicily over the past 40 kyrs: Timing of emersion and implications for the migration of Homo sapiens

2012

The submerged Sill in the Messina Strait, which is located at a depth of -81 m m.s.l., represents the only possibile connection between Calabria and Sicily during the last lowstand, when the sea level was at about -126 m m.s.l. This multidisciplinary research aim at documenting times and modes the bridge between Calabria and Sicily was emerged, during the last 40 ka BP. The analysis carried out on morphobathymetric, lithological and relative sea level change (both isostatic and tectonic) data allow to hypothesize the continental bridge emerged at least between 21.5 ka and 20 ka cal BP. Moreover, considering erosion processes due to very strong marine currents, it could be emerged for a long…

A beam search algorithm for minimizing crane times in premarshalling problems

2022

The premarshalling problem consists of sorting the containers placed in a bay of the container yard so that they can be retrieved in the order in which they will be required. We study the premarshalling problem with crane time minimization objective and develop a beam search algorithm, with some new elements adapted to the characteristics of the problem, to solve it. We propose various evaluation criteria, depending on the type of container movement, for its local evaluation; a new heuristic algorithm including local search for blue its global evaluation; and several new dominance rules. The computational study shows the contribution of each new element. The performance of the complete algo…

How do university students’ web search behavior, website characteristics, and the interaction of both influence students’ critical online reasoning?

2020

The Internet has become one of the main sources of information for university students’ learning. Since anyone can disseminate content online, however, the Internet is full of irrelevant, biased, or even false information. Thus, students’ ability to use online information in a critical-reflective manner is of crucial importance. In our study, we used a framework for the assessment of students’ critical online reasoning (COR) to measure university students’ ability to critically use information from online sources and to reason on contentious issues based on online information. In addition to analyzing students’ COR by evaluating their open-ended short answers, we also investigated the stude…