Mariangela Ravaioli

Particle fluxes and biogeochemical processes in an area influenced by seasonal retreat of the ice margin (northwestern Ross Sea, Antarctica)

Abstract Fluxes of biogenic components were determined using time-series sediment trap samples collected at site B (74°01.50′S, 175°05.55′E) in the northern Joides Basin of the Ross Sea from December 1994 to January 1996. In most cases, a great part of the material collected by traps (200 and 540 m depth) was biogenic, opal being the most abundant constituent followed by organic matter. The composition of particles shows a seasonal pattern in the upper trap, which is much less evident at depth. Fluxes showed a marked seasonality due to the presence, in winter, of ice cover. During the sampling period, mass fluxes varied from 0.03 to 120 mg m −2 day −1 and from 24 to 393 mg m −2 day −1 at the upper and bottom level, respectively. Values of 0–64 mg m −2 day −1 of biogenic silica and 0–7.8 mg m −2 day −1 of organic carbon were obtained at 200 m depth. Near-bottom fluxes were almost always much higher: 11–141 and 1.5–19 mg m −2 day −1 , respectively. 210 Pb fluxes are lower than expected, and this means that particles sink rapidly without reaching an equilibrium with the radiotracer. A mechanism of focusing affects the bottom trap and much more, the seafloor. At site B, we measured particle fluxes that are much lower than those obtained at other locations in the Ross Sea. This can be due to low production and export during the sampling period, and underlies the necessity to further investigate the interannual variability of these processes.

Historical pattern and mass balance of trace metals in sediments of the northwestern Adriatic Sea Shelf

In view of the recent action in Marine Strategy Framework Directive, reconstructing the history of anthropogenic metal inputs and calculating the budgets for the northwestern part of the Italian Adriatic basin can provide a benchmark for comparison with new evidences and enlighten recent environmental changes. Among the metals, the attention was focused on Pb and Zn, as they provide the most significant anthropogenic signals. In 1988, areal distributions clearly identified the Po, Adige and Brenta rivers as the main sources of contaminants. The study area was divided in three compartments. The area in front of the Po delta represented a sink for metals but the accumulation of Zn and Pb integrated over the entire study area suggests an effective export throughout southern boundary. Most concentration-depth/year profiles in cores showed an upward increase from the Italian Unification (1861), with a still significant anthropogenic supply at the time of sampling.

Sedimentary process inferences from Humic substances analysis and deposition rates (Western Ross Sea, Antarctica)

The first 40 cm of sediment of three basins in the Ross Sea were sampled using a box corer. Site Y1 was located close to the coast in Terra Nova Bay; the sediment of site Y3 was collected in a more distal basin in the central sector of the Ross Sea; finally site Y5 was sampled in the deepest zone of the Joides Basin. Sediment cores were sliced and analysed with a depth resolution of 2–4.5 cm. The distribution of humic substances and their structural features along the cores were determined and related to the pattern of Total Organic Carbon (TOC) and sedimentological data. The grain size distribution and the 210Pb inventories allow the sediment of the study sites to be characterised. The humic substance content in the sediment decreases, with a change in slope between 23 and 26 cm at Y1, between 12 and 15 cm at Y3 and constant values with further depth. At Y5 the depth profile of humic substance content shows constant values in the upper 17 cm and values decrease with further depth. The pattern of humic substance yield is similar to that found for TOC. The analysis of the elemental composition of the humic acids extracted from different sediment depths shows an increasing C/N atomic ratio at sites Y1 and Y3 and constant values along the Y5 core. The depth profile of the C/N atomic ratio is confirmed by the changes observed in the structural characterisation and indicates a shift from the freshly deposited organic matter on the sediment surface to more humified material (humin). The results obtained highlight a different sedimentation rate at the three sites as deduced from sedimentological analysis.

Mg/Ca ratios in the planktonic foraminifer Neogloboquadrina pachyderma (sinistral) from plankton tows in the Ross Sea and the Pacific sector of the Southern Ocean (Antarctica): comparison of different methodological approaches

Mg/Ca ratios in living specimens of the planktonic foraminifer Neogloboquadrina pachyderma (sin.) have been investigated using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and ultracleaning procedures on ‘bulk’ foraminifera followed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES) analysis. Plankton tows were taken in the upper 250 m of the water column at different sites in the Ross Sea and at the Polar Front of the Pacific Ocean during 6 austral summers. We found high values of Mg/Ca ratios in N. pachyderma (s.) not previously reported in the literature. Our data suggest that at least two factors influence the results: (1) the presence of some protoplasm in the test of living specimens, which seems to control the actual Mg concentration and (2) the morphotype of the analysed specimens in term of test thickness.

Abyssal benthic foraminifera in the Polar Front region (Pacific sector): Faunal composition, standing stock and size structure

We have evaluated the quantitative composition of Rose Bengal-stained benthic foraminiferal assemblages of surface samples from two box cores (ANTA98-28 bc; ANTA01-01 bc) collected at the Polar Front in the Pacific sector of the Southern Ocean. Size structure, faunal composition and standing stock were analysed for living (Rose Bengal-stained) and dead foraminifera. The size fractions among 63–150, 150–250 and >250 µm were counted separately in order to study the foraminiferal size distribution and to compare our results with earlier Antarctic studies. The low organic carbon content of the sediment, and hence the limited food availability, is reflected by very low standing stocks and low diversity values. Calcareous taxa dominated dead foraminiferal assemblages that were more diverse than the stained assemblages. In the sediment samples of ANTA01-01 bc, the living fauna contained agglutinated taxa and soft-shelled monothalamous forms. Our data represent the southernmost record of benthic foraminiferal community (63° S) from the Polar Front region in the Pacific sector. These samples provide further evidence for the occurrence of meiofaunal foraminifera in extreme environments, like the Antarctic region, where the uncoupled annual variations in temperature and production cause strong effects on the structure of benthic communities.

Seasonal and pluri-annual variability of sediment accumulation and organic matter fluxes in the Northwestern Adriatic shelf and its relationship with the frontal system

Twenty eight short sediment cores, collected along six transects in two areas influenced by the frontal system formed by the Po River, were analysed for Th and Cs in order to improve our knowledge on short time scale sediment deposition, accumulation and mixing. Sedimentological and mineralogical parameters were also analysed._ The decreasing Cs activities and C/N values in surface sediments indicate a decreasing input of terrestrial material during the study period. Furthermore, low excess thorium activities and inventories at some sites, together with low sedimentary organic matter concentrations in the southern area, suggest that the productivity in summer 1997 was lower than in 1996. Temporal and spatial shifts of the front exert a strong influence on short time scale deposition of particulate matter in the northern area, while the front position is more stable in the southern area, influencing both seasonal and interannual deposition._ The comparison between apparent seasonal and pluri-annual accumulation rates suggests, for the northern area, a sedimentation pattern characterized by temporal deposition of material on to the sea floor, with periodical resuspension. The net apparent accumulation is 0.1-0.4 r g r cm r yr. The same occurs for the southern area, where values are higher, probably due to the longer persistence of the frontal system in the same area over the years. Here, both seasonal and pluri-annual deposition showed the same pattern, but seasonal values were two to three times higher with a net apparent accumulation rate of 0.3-0.8 r g r cm r yr. Organic carbon and nitrogen concentrations are generally less than 1.3 and 0.2% d.w., with lower values in the southern area. By contrast, mass fluxes showed higher values in the southern area, while the rate of removal over a pluri-annual time scale is generally high.

The observation system of the Italian coastal zones

The study of the marine coastal areas is of great importance, for both the protection and management of the environment. Due to the always increasing anthropic pressure, the availability of real time and model data can be critical for decisions, expecially during emergencies In addition, the availability of time-series and of observation points is necessary for proper problem setting and tuning of models and knowledge-based systems. We present some experience of Real Time data transmission and handling from stations and platforms, aiming toward a better integration into an Observation System.

The role of the rivers in Chernobyl radiocesium delivery, distribution and accumulation in coastal sediments of the Northern Adriatic Sea

Abstract The fate of radiocesium transported by rivers to the Adriatic Sea and accumulated in sediments was investigated in the Northern Adriatic coastal area. Concentrations and inventories obtained for the areas of influence of the most important rivers (Tagliamento, Isonzo, Piave, Adige and Po) were compared. Radiocesium preferentially accumulates in the prodelta areas. In 1987 137 Cs maximum concentrations and inventories in these zones ranged between 200 and 300 Bq kg −1 and between 12 and 64 kBq m −2 , respectively. The temporal dynamics in selected zones was studied by sampling at the same site in different years. Temporal differences in the radionuclide inventories show that some areas are unstable on the time scale of one year due to sediment resuspension processes.

Morphobathymetry of Boka Kotorska Bay

Boka Kotorska Bay is an enclosed water body with a narrow and shallow connection to the Adriatic Sea; the shallowest point is only 37.6 m deep at present, limiting exchange of water with the Adriatic. The Bay is one of the most important transitional areas of the Adriatic from both an environmental and a socio-economic viewpoint. High resolution geophysical data collected during several scientific cruises carried out between 2008 and 2013 reveal unknown details of present-day morphology and sedimentary infilling geometry. Multibeam bathymetry combined with seismic reflection images suggests that the observed morphologies are due to the interaction at different timescales of climate, water circulation, sealevel changes, erosion, sedimentation and tectonics constrained by the geological and structural setting of the area. The Bay is composed by three major basins (Herceg Novi, Tivat and Morinj–Risan–Kotor), connected by two narrow straits (Kumbor and Verige) with a maximum depth of 67 m. It shows steep upper slopes and flat sub-basin central sectors lying at depths ranging from 35 to 45 m. Among the several morphological features shaping the seafloor, we note: deeply incised valleys and delta fans related to past sealevel falls; slope failures and mass wasting triggered by strong earthquakes; channels bounding the steep slopes of Kumbor and Verige narrow passages, and sediment wave fields in Verige Strait formed by strong bottom currents; and karst morphologies developing at seafloor with submarine siphons, springs and resurgences (pockmarks) fed by karst hydrology of Boka Kotorska Bay’s surroundings.

Operational use of continuous surface fluorescence measurements offshore Rimini to validate satellite-derived chlorophyll observations

ABSTRACT Continuous chlorophyll (Chl) measurements derived from lab-validated in situ fluorometry in the coastal Adriatic Sea are used as a matchup database to validate MODerate resolution Imaging Spectroradiometer MODIS/AQUA Chl. Daytime quenching reduces fluorescence with respect to the higher values measured in the samples taken to the lab which are well correlated with the maximum measurements recorded within the preceding 12 h. Comparison between remotely-sensed and in situ Chl indicates that the 27% of the matchups within 35% of the in situ data have a 0.97 correlation while the discrepancy of the remaining 63% is not linked to remotely-sensed data-quality flags.