Virgilio Frezza

Benthic foraminifera from two coastal lakes of southern Latium (Italy). Preliminary evaluation of environmental quality

Benthic foraminifera and sediment texture were studied on a total of 37 samples, collected from two brackish-water coastal basins: Fogliano Lake and Lungo Lake (central Italy). The research was performed as a preliminary low-cost survey to highlight the degree of the environmental stress and to recognize a possible anthropogenic disturbance. The sedimentological and foraminiferal data were processed by bivariate and multivariate statistical analysis. Three distinct assemblages, referable to different environments were recognized for the Fogliano Lake: inner, intermediate and outer lagoon. Only the outer lagoon assemblage was found in the Lungo Lake. The distribution of foraminifera in the Fogliano Lake suggests a natural environmental stress probably due to the ecological instability typical of marginal environments, while the absence of the inner and intermediate lagoon assemblages in the Lungo Lake suggests an environmental disturbance possibly related to human activities. An interdisciplinary survey including geochemical analyses is recommended in order to deduce the nature and degree of pollution in the Lungo Lake.

Bathy-morphological setting of Terceira Island (Azores) after the FAIVI cruise

High-resolution morpho-bathymetric data at 1:200,000 scale obtained during the FAIVI cruise (2011) and the resulting geomorphologic map of the Terceira island offshore area (central Azores, Portugal) are presented for the first time. The uneven morphology around Terceira is primarily related to volcanic features, such as linear and cone-shaped eruptive centres and lava flows. Such features are mostly concentrated on volcanic ridges and are aligned along preferential axes, suggesting a strong interaction between tectonics and volcanic processes. The occurrence of active tectonics is also demonstrated by systems of faults cutting the seafloor to the north, east and south of the island. Mapped erosive-depositional features include an insular shelf located at < 150 m water depth (wd), small landslide headwalls, erosive scarps, channelized features and crescent-shaped bedforms. The presented map may represent the base for a first-order geo-hazard assessment.

Mixed carbonate-siliclastic sediments and benthic foraminiferal assemblages from Posidonia oceanica seagrass meadows of the central Tyrrhenian continental shelf (Latium, Italy)

Sedimentological and micropaleontological characterisation of bottom sediments from two Latium continental platform areas (central Tyrrhenian Sea) was carried out. The two studied areas are Santa Marinella in northern Latium and Ponza Island in southern Latium (Pontine Archipelago), characterised by the presence of Posidonia oceanica seagrass, but with different sediment inputs. In the Santa Marinella area, where seagrass ends at 15 m water depth, there are both siliciclastic sediments from fluvial run-off and carbonate lithoclasts originated by coastal erosion. In the Pontine Archipelago, in which P. oceanica meadows end at 35-40 mwd, terrigenous clasts originate only from coastal erosion and, consequently, carbonate production prevails. On the whole, grain size analysis shows a strong predominance of sandy fraction, whereas mud and gravel are subordinate. The very low frequencies of muddy fraction can be attributable to re-suspension processes and the lack of aragonitic components that produce mud-sized particles. The better sorting of Santa Marinella seagrass substrate with respect to Ponza Island is related to the origin of terrigenous sediments, which are mainly provided by rivers and so are previously sorted. Facies analysis was performed using component analyses, grain size percentage, sorting and carbonate content, complemented with the observations obtained from artificially-hardened sediments and, finally, tested with a Q-mode cluster analysis. Consequently, 4 sedimentary facies have been recognised. Facies F1, limited to the Santa Marinella area (7.5-13.5 mwd), is characterised by sand-sized wellsorted sediments, and dominated by the terrigenous fractions. Facies F2 represents the shallowest seagrass environment (5-7 mwd), and it is restricted to the Ponza area. In this environment the sedimentation is still dominated by terrigenous components, while the carbonate sediment contribution is due principally to red algae. Facies F3 has the widest water depth interval (8-34 mwd), and principally occurs in the Ponza site, while only two samples are from the Santa Marinella. The terrigenous fraction is conspicuous, however there is an increase of carbonate sediment produced mainly by the epiphytes (foraminifera, bryozoans) and, subordinately, by benthic organisms (foraminifera, molluscs). Facies F4, occurring in the Ponza site (17-29 mwd), is the most carbonate rich facies with a carbonate sediment produced by epiphytic (foraminifera, bryozoans, serpulids, red algae) as well as benthic (foraminifera, red algae, molluscs) biota. Q-mode cluster analysis performed on the most abundant benthic foraminiferal species led to the identification of 4 assemblages, dominated by epiphytic foraminifera. The A1 assemblage was found only in the Ponza site (5-12 mwd) and is dominated by Lobatula lobatula, Peneroplis pertusus and Miliolinella subrotunda. The A2 assemblage (10-34.5 mwd), characterised by L. lobatula and Rosalina bradyi, is mainly limited to Ponza Island, with only one sample from Santa Marinella. The B1 (7.5-9 mwd) and B2 (8-13.5 mwd) assemblages were found only in the Santa Marinella area and are dominated by L. lobatula, R. bradyi and Conorbella hexacamerata and by Asterigerinata mamilla and R. bradyi, respectively. The calculated diversity indices (α-Fisher and Shannon index) are very similar in both areas, whereas the dominance percentage is higher in the Santa Marinella site. The lack of the symbiont-bearing foraminifer P. pertusus in the Santa Marinella samples may be linked to less favourable environmental conditions. In this area, the prevalent siliciclastic sedimentation and the water turbidity, which decreases the light penetration, are the limiting factors also for the seagrass growth. The comparison between the foraminiferal assemblages of two areas may be used to estimate the health of present-day and fossil seagrass.

Benthic foraminiferal assemblages of the imperial harbor of Claudius (Rome): Further paleoenvironmental and geoarcheological evidences

This paper presents a paleoenvironmental reconstruction of historical development in the area of the ancient harbor of Claudius based on micropaleontological and sedimentological data. Benthic foraminifera are reliable tools for this kind of research because they are sensitive to short-time environmental changes induced by both natural and anthropogenic events. By studying eight sediment cores collected from different sections of the harbor, it was possible to reconstruct a comprehensive picture of the harbor complex. Qualitative and quantitative analysis of foraminiferal associations and sedimentological data, along with radiocarbon dating, were useful to identify three key intervals in the history of the coastal area where the harbor developed. The first interval, located at the bottom of all cores, is characterized by a brackish water environment, corresponding to the formation of the first deltaic cusp of the Tiber River. The second interval is characterized by the harbor activities that developed after a general increase in water depth due to a diversion of the Tiber River mouth. The third interval marks the final phase of harbor activities and the subsequent filling of Claudius’ basin. However, a link with the inner Trajanus’ basin was maintained via the central part of the basin, which remained submerged longer, until the early Middle Ages.

Recent foraminiferal assemblages from mixed carbonate-siliciclastic sediments of southern Somalia and eastern Kenya

A total of 256 recent benthic foraminiferal species belonging to 111 genera is identified from 73 carbonate-siliciclastic sedimen samples collected along the coast of southern Somalia (Burgao channel) and eastern Kenya (Lamu Archipelago). This represents the first survey of recent foraminifers in this region of East Africa. The sediment samples are representative of different environments (e.g., mangrove flats, tidal channels, restricted shelf, and open shelf), water depths (0-60 m), and salinities (strongly brackish to normal marine conditions). Q-mode Hierarchical Cluster Analysis reveals that nine assemblages can be distinguished; for each assemblage, faunal composition and distribution, diversity indices and dominance are assessed. As predicted by ecological models, there is an overall trend of increasing species diversity from the backwater zone within channels to open marine conditions, and from intertidal to subtidal settings. Salinity, suspended sediment, nutrient levels, and tidal exposure are the most influential factors in determining benthic foraminiferal distribution patterns. An interesting feature is the nearshore contraction of the depth gradient determining the shallower distribution of several larger foraminiferal species, as evidenced by the depth ranges of five species of Amphistegina

Benthic foraminiferal assemblages from shallow-water environments of northeastern Sardinia (Italy, Mediterranean Sea)

Thirteen samples were collected from three coastal bays of northeastern Sardinia (Gallura). Bays are areas of mixed siliciclastic-carbonate sedimentation. Seagrasses and algae, widely distributed in the shallow-water environments, contribute to the carbonate factory. Near-shore benthic foraminifers (111 species, 50 genera), occurring in the shallower water areas of Posidonia oceanica, were taxonomically identified and the assemblages were investigated by statistical analysis to determine if any groups of samples or species correlate with a specific sub-environment. Dominant taxa are phytophilous and three main assemblages were identified: the Lobatula lobatula/Elphidium crispum assemblage and Lobatula lobatula/Peneroplis pertusus assemblage are linked to the distribution of P. oceanica, whereas the Peneroplis/Quinqueloculina assemblage reflects oligotrophic conditions and a mixed algal/Posidonia substrate. Taxonomic abundance and diversity appear to be mainly controlled by the type of phytal substrate.

Benthic foraminiferal assemblages in active volcanic area of the Azores Islands (North Atlantic Ocean)

The present study shows the preliminary micropalaeontological results obtained from surface samples collected during an Eurofleet marine geological survey in the Terceira offshore (Azores Archipelago, Portugal) carried out in September 2011.Benthic foraminiferal assemblages were studied in order to obtain a sea-floor ecological characterisation in natural stressed environments like active volcanic area of the Azores Islands. Sediments were collected at water depths ranging between 260 and 410 m and consist of blackish, sand-sized glass shards, in which highly vesicularto scoriaceous clasts prevail on fluidal striated fragments. All samples were stained with Rose Bengal to determine living and dead assemblages.The dominance of living specimens suggests that the first generation of foraminiferal colonisers was found. Diversity index (α-Fisher index), Faunal density and Foraminiferal Abnormality Index (FAI) were calculated to assess the structure of the assemblage and the degree of environmental stress. Living and dead assemblages are verysimilar; they are very scarce but sufficiently diversified. The living benthic assemblage is dominated by epi/shallow infaunal species Angulogerina angulosa and typical infaunal taxa like Bolivina spp.Subordinately other epifaunal (Ehrenbergina bradyi, Lenticulina spp., Quinqueloculina seminula, Stomatorbina concentrica) and agglutinated species (Ammoglobigerina globigeriniformis, Eggerelloides scabrus, Haplophragmoides canariensis, Spiroplectinella wrightii, Textularia spp.) are also recorded. Significant frequencies of specimens showing signs of test decalcification were found. These test alterations could be due to hydrothermal fluids, since similar features were recorded in foraminiferal specimens coming from other volcanic substrates in the Aeolian Arc (Tyrrhenian Sea). The dominance of living and dead A. angulosa specimens allows us to consider this species as opportunistic pioneer taxon able to colonise stressed environments. This is confirmed also by the highest values of FAI (>2%), recorded in most of the samples, indicating a persisting environmental stress. Angulogerina angulosa and Bolivina spp. are the species showing more abundant deformed specimens (irregular development of chambers and aberrant tests). On the basis of our observations, the recolonisation process and the spatial distribution patterns are strongly influenced by the sea bottom high hydrodynamic regime which is responsible for volcanic deposit transport and depositional events. These conditions may be reflected on the relationship between benthic foraminifers and substrate features, which are mainly restricted to grain size, morphology and texture of volcanic shards.

Environmental changes by mean the foraminiferal assemblages in the Late Quaternary deposits of Terracina basin (Central Tyrrhenian Sea, Italy).

Micropaleontological analysis, from three cores collected on the Tyrrhenian continental shelf in the Terracina basin allowed to highlight a transgressive trend related to the Holocene sea-level rise (Versilian transgression). Four distinct environments identified by ten benthic foraminiferal assemblages were recognised. The oldest ones is related to lagoon-barrier system or brackish-water environment and is dominated by the euryaline species Ammonia tepida . The progress of transgressive trend have resulted in the replacement of the paleo-lagoon ( Ammonia tepida assemblage) with a sandy beach environment ( Ammonia spp. and Elphidium spp. assemblage), locally interested by vegetated cover (marked by the dominance of epiphytic taxa). Finally the presence of taxa typical of circalittoral zone ( Melonis pompilioides , Reussella spinulosa , Globocassidulina subglobosa , Gavelinopsis praegeri and Asterigerinata adriatica ) marked the sea-level stabilisation and the recent foraminiferal distribution.

Spiculosiphon oceana (Foraminifera) a new bio-indicator of acidic environments related to fluid emissions of the Zannone Hydrothermal Field (central Tyrrhenian Sea)

The new record of a shallow-water submarine hydrothermal field (<150 m w.d.) in the western Mediterranean Sea (Tyrrhenian Sea, Italy) allows us to study CO2 fluid impact on benthic foraminifers. Benthic foraminifers calcification process is sensitive to ocean acidification and to local chemical and physical parameters of seawater and pore water. Thus, foraminifers can record specific environmental conditions related to hydrothermal fluids, but at present their response to such activity is poorly defined. The major outcome of this study is the finding of a very uncommon taxon for the Mediterranean Sea, i.e., the Spiculosiphon oceana, a giant foraminifer agglutinating spicules of sponges. This evidence, along with the strong decrease of calcareous tests in the foraminiferal assemblages associated to hydrothermal activity, provides new insights on the meiofauna living in natural stressed environment. In particular, observations obtained from this study allow us to consider S. oceana a potential tolerant species of high CO2 concentrations (about 2-4 times higher than the normal marine values) and a proxy of acidic environments as well as of recent ocean acidification processes.

Foraminiferal assemblages in active volcanic areas: two study cases from Azores Archipelago (Atlantic Ocean) and Pantelleria Island (Mediterranean Sea)

Lucchi, Renata G. ... et. al.-- 87° Congresso della Societa Geologica Italiana e 90° Congresso della Societa Italiana di Mineralogia e Petrologia, The Future of the Italian Geosciences - The Italian Geosciences of the Future, 10-12 September 2014, Milan, Italy.-- 1 pageThe Montellina Spring (370 m a.s.l.) represents an example of groundwater resource in mountain region. It is a significant source of drinking water located in the right side of the Dora Baltea Valley (Northwestern Italy), SW of Quincinetto town. This spring shows a morphological location along a ridge, 400 m from the Renanchio Torrent in the lower sector of the slope. The spring was investigated using various methodologies as geological survey, supported by photo interpretation, structural reconstruction, NaCl and fluorescent tracer tests, discharge measurements. This multidisciplinary approach, necessary due to the complex geological setting, is required for the importance of the Montellina Spring. It is interesting in the hydrogeological context of Western Alps for its high discharge, relatively constant over time (average 150 l/s), and for its location outside a fluvial incision and suspended about 40 m above the Dora Baltea valley floor (Lasagna et al. 2013). According to the geological setting, the hydrogeological reconstruction of the area suggests that the large amount of groundwater in the basin is essentially favoured by a highly fractured bedrock, covered by wide and thick bodies of glacial and gravitational sediments. The emergence of the water along the slope, in the Montellina Spring, is essentially due to a change of permeability between the deep bedrock and the shallow bedrock and/or surficial sediments. The deep bedrock, showing closed fractures and/or fractures filled by glacial deposits, is slightly permeable. The shallow bedrock, strongly loosened as result of gravitational phenomena, and the local gravitational sediments are, on the contrary, highly permeable. The concentration of water at the spring is due to several reasons. a) The spring is immediately downward a detachment niche, dipping towards the spring, that essentially drains the water connected to the change of permeability in the bedrock. b) It is along an important fracture, that carries a part of the losses of the Renanchio Torrent. c) Finally, it is favored by the visible and buried morphology. Although it is located along a ridge, the spring occurs in a small depression between a moraine and a landslide body. It also can be favored by the likely concave trend of buried base of the landslide. At last, tracer tests of the Renanchio Torrent water with fluorescent tracer are performed, with a continuous monitoring in the Montellina Spring. The surveys permit to verify and quantify the spring and torrent hydrogeological relationship, suggesting that only a small fraction of stream losses feeds the spring.