The climatic characteristics of extreme precipitations for short-term intervals in the watershed of Lake Maggiore

Alpine and Mediterranean areas are undergoing a profound change in the typology and distribution of rainfall. In particular, there has been an increase in consecutive non-rainy days, and an escalation of extreme rainy events. The climatic characteristic of extreme precipitations over short-term intervals is an object of study in the watershed of Lake Maggiore, the second largest freshwater basin in Italy (located in the north-west of the country) and an important resource for tourism, fishing and commercial flower growing. The historical extreme rainfall series with high-resolution from 5 to 45 min and above: 1, 2, 3, 6, 12 and 24 h collected at different gauges located at representative sites in the watershed of Lake Maggiore, have been computed to perform regional frequency analysis of annual maxima precipitation based on the L-moments approach, and to produce growth curves for different return-period rainfall events. Because of different rainfall-generating mechanisms in the watershed of Lake Maggiore such as elevation, no single parent distribution could be found for the entire study area. This paper concerns an investigation designed to give a first view of the temporal change and evolution of annual maxima precipitation, focusing particularly on both heavy and extreme events recorded at time intervals ranging from few minutes to 24 h and also to create and develop an extreme storm precipitation database, starting from historical sub-daily precipitation series distributed over the territory. There have been two-part changes in extreme rainfall events occurrence in the last 23 years from 1987 to 2009. Little change is observed in 720 min and 24-h precipitations, but the change seen in 5, 10, 15, 20, 30, 45, 60, 120, 180 and 360 min events is significant. In fact, during the 2000s, growth curves have flattened and annual maxima have decreased.     

Architecture and recognition criteria of ancient shelf ridges; an example from Campanian Almond Formation in Hanna Basin,USA

Shelf ridges are sedimentary bodies formed on the continental shelf due to transgressive reworking (tidal or storm) of lowstand deposits. Common on modern shelves, they are under‐represented in the geological record due to a lack of recognition criteria and facies model. This article proposes a new facies and architectural model for shelf ridges, linked to their inception–evolution–abandonment cycle and the process regime of the basin. The model is mainly based on new outcrop data and interpretations from three sandstone bodies of the Almond Formation, an overall transgressive interval during the infill of the Campanian Western Interior Seaway. Building from the case study, and ancient and modern examples, six characteristics are proposed for the recognition of ancient shelf ridges. Shelf ridges: (i) are encased between thick marine mudstone intervals; (ii) have a basal unconformity that erodes into marine muds or into the remnants of a previous shoreline; (iii) have a non‐erosional upper boundary that transitions into marine muds; (iv) are characterized by clean and well‐sorted sandstones, often cross‐bedded; (v) contain fully marine ichnofauna; and (vi) present compound architectures with large accretion surfaces and lower order structures. Although shelf ridges have been described in previous studies as generated exclusively by either tidal or storm currents, it is clear, from modern examples and the case study, that these two processes can be recorded and preserved in a single shelf ridge. The stratigraphy of these sandstone bodies is therefore much more complex than previously recognized, bearing the signature of changing tidal and storm intensity through time. Because they are developed during transgressions, shelf ridges are commonly subject to strong changes in process regime as sea‐level changes can easily affect the oceanographic conditions and the morphology of the basin. For this reason, shelf ridges can provide the best record of shelf process variability during transgressions.     

Keratose-dominated sponge grounds from temperate mesophotic ecosystems (NW Mediterranean Sea)

Differently from the North Atlantic Ocean, only few examples of sponge grounds are known from the Mediterranean Sea, mainly thriving in the deep sea. In this study, a novel temperate mesophotic ecosystem dominated by massive keratose sponges is reported from the Ligurian deep continental shelf. An extensive Remotely Operated Vehicle (ROV) survey allowed to study the structure and large-scale distribution of this biocoenosis. The sponge grounds here described are highly fragmented, being formed by a large number of dense, discrete aggregations of Sarcotragus foetidus (up to 7.7 specimens/m²) and other sponges, including Spongia lamella and Axinella polypoides. They mainly occur on flat, patchy and highly silted hardgrounds between 40 and 70 m depth. These sponge-dominated ecosystems have an exceptionally wide spatial distribution, estimated to cover up to nearly 200 hectares, with the largest sponge grounds occurring along the westernmost part of the Ligurian coast, probably in relation to more suitable oceanographic conditions. The dominant sponge species reach considerable heights (up to 65 cm), greatly increasing the habitat three-dimensionality and acting as poles of attraction for a diverse sessile and vagile fauna. In addition, the high abundance of the keratose sponge grounds at mesophotic depths might represent a larval source for shallow-water populations that in the last decades have been stricken by several mass mortality events.     

Extreme rainfall events: evaluation with different instruments and measurement reliability

With regard to extreme events, it is well documented that an intensity of about 1 mm/min already represents an extreme intensity. Under alpine conditions, a precipitation event with an intensity of 3 mm/min has occurred. Therefore, the rain gauges in this region have to be able to measure in this and even in higher intensity ranges. This study deals with basic automated tipping-bucket rain (TBR) gauge and Bulk precipitation samplers, which are able to hold more than 95 % of the cumulative rainfall, that are verified within the space of the week without losses during the extreme events and with minimal evaporation loss. Bulk samplers collected more rainfall than TBR gauges in 110 of 221 extreme events analysed over the past 10 years. In 17 extreme events, an underestimation greater than 10 % was evaluated. The objective was to single out the counting errors associated with TBR gauge, during extreme events, so as to help the understanding of the measured differences between instruments in the field. We want to determine whether the automated precipitation gauge can provide a reliable and precise measurement of precipitation with particular interest regarding heavy and extreme events.     

The coral assemblages of an off‐shore deep Mediterranean rocky bank (NW Sicily,Italy)

In this study we characterized the deep assemblages dwelling at 200–250 m depth on a large shoal off Capo St. Vito Promontory (Northwestern coast of Sicily, South Tyrrhenian Sea) by means of ROV‐imaging. Two assemblages of suspension feeders, dominated by the gorgonian Callogorgia verticillata and by the black coral Leiopathes glaberrima, together with a tanatocoenosis of the colonial yellow scleractinian coral Dendrophyllia cornigera, were examined. The three main species were significatively distributed into two areas corresponding to different habitat preferences: a more elevated hardground hosting black corals and a gently sloping, silted rocky bottom hosting the other coral species. The study area is subjected to a heavy pressure from the professional fishery, resulting in the mechanical damage of numerous colonies, some of which are then overgrown by various epibionts including a parasitic bioluminescent zoanthid, new for the Mediterranean fauna, and tentatively identified as Isozoanthus primoidus. In the Mediterranean Sea, these deep off‐shore rocky banks are widely known among recreational and professional fishermen due to their rich fish fauna. However, there has been still little effort into quantifying and characterizing the extent of the impact and its consequences on the benthic communities, which may represent, as in this case, only a partial picture of their original structure and extent.     

Over 10 years of variation in Mediterranean reef benthic communities

During the last several decades, the Mediterranean littoral shallow water benthic communities have suffered significant changes in their structure and taxa composition. Despite numerous studies conducted to characterize these changes at various levels, it has always been very difficult to disentangle the effects of natural factors from anthropic ones. The main purpose of this work was to evaluate possible changes, over a 10‐year scale, in diversity and abundance of the most representative species of the benthic communities considered to be primarily and potentially affected by natural stressors in a highly protected area. Sets of macro‐photographs were taken in 2002–2003 of three sites inside a small bay called Ca’ dell'Oro, which is the “no entry—no take” zone of the Marine Protected Area of Portofino, in order to analyse the structure of the benthic communities at different depths over a short time scale. The same sampling was repeated 10 years later in 2013. In the 10‐year span, a significant change in the macroalgal coverage and composition was observed, while the overall richness and coverage of species remained almost unchanged. This process resulted in a significant reduction of the habitat complexity of the three‐dimensional algal components. Likewise, a remarkable change in terms of presence and abundance occurred among all zoobenthic components. The benthic communities seem to have suffered from detrimental effects probably caused by climatic events that have been occurring in recent years in the Ligurian Sea.     

Reconstructing the palaeoenvironments of the early Pleistocene mammal faunas from the pollen preserved on fossil bones

We carried out a systematic investigation on the pollen content of sediment adhering to skeletal elements of large mammals which originate from the long lacustrine record of Leffe (Early Pleistocene of the Italian Alps). Three local faunas were discovered during mining activities along the intermediate part (spanning from 1.5 to 0.95 Ma) of the basin succession. The excellent pollen preservation allowed testing the reproducibility of the pollen signal from single skeletons. A clear palaeoenvironmental patterning, consistent with the ecological preferences of the considered mammal species, emerged from the canonical correspondence analysis of pollen types diagnostic for vegetation communities. Edaphic factors related to seasonal river activity changes and to the development of swamp forests in the riverbanks are significantly associated to the occurrences of Hippopotamus cf. antiquus, whereas finds of Mammuthus meridionalis belong to fully forested landscapes dominated by conifer or mixed forests of oceanic, warm to cool-temperate climate. Rhinoceros habitats include variable forest cover under different climate states. Distinct cool-temperate, partially open vegetation could be recognized for large deer included Cervalces cf carnutorum.A palynostratigraphic correlation between individual spectra and a reference palynostratigraphic record allowed assignment of many fossil remains to a precise stratigraphic position. This procedure also shown that the Leffe local faunas include specimens accumulated under different environmental and climate states, as a consequence of high-frequency climate changes characterizing the Late Villafranchian Early Pleistocene.     

Mud‐rich delta‐scale compound clinoforms in the Triassic shelf of northern Pangea (Havert Formation,south‐western Barents Sea)

In recent years it has become clear that many shallow‐marine heterolithic and mudstone‐dominated successions are deposited as mud belts forming part of subaqueous deltas that are related to major fluvial sources either upstream or along shore. Here the Havert Formation is presented as an ancient example of this kind of system. The Havert Formation in the south‐western Barents Sea represents shelf margin clinoforms consisting predominantly of heterolithic deposits. Sediments were mainly derived from the east (Ural Mountains), but a smaller system prograded northward from Fennoscandia. The Havert Formation holds a lot of interest due to: (i) its stratigraphic position, directly above the Permo–Triassic boundary and contemporaneous to the emplacement of the Siberian Traps; (ii) the fact that it represents the first siliciclastic input in the south‐western Barents Sea and it shows interaction between Uralian‐derived and Fennoscandian‐derived sediments; and (iii) its hydrocarbon potential. This study is focused on a detailed sedimentological analysis of cored intervals of the (Ural‐derived) Havert Formation, in combination with seismic interpretation, well‐log correlations and palynological analysis of the Havert and overlying Klappmyss formations. The cored intervals belong to the shelf environment of the Havert shelf‐margin clinoforms (300 to 500 m thick). This sedimentological analysis distinguishes six facies associations, spanning from tidally‐influenced channels at the shoreline to mud‐rich subaqueous platform and foresets of the subaqueous delta. Seismic lines and well‐log correlations show the larger‐scale evolution of the Ural‐derived Havert Formation, characterized by episodes of low‐accommodation and high‐accommodation. The palynological analyses provide the first detailed study of the Havert Formation in the Nordkapp Basin, revising its depositional age in the region as Induan to early Olenekian (Smithian). Furthermore, they strengthen the environmental interpretation; palynofacies present on the shelf record flora of tidally‐influenced coastal plains, whereas the palynofacies in the deep‐water slope contain only amorphous organic matter.     

Long‐term comparison of structure and dynamics of the red coral metapopulation of the Portofino Promontory (Ligurian Sea): a case‐study for a Marine Protected Area in the Mediterranean Sea

A large amount of data on the precious coral Corallium rubrum has attested to a dramatic shift in the size structure of its over‐harvested Mediterranean populations in recent decades. One of the main problems for the conservation of this species is the substantial lack of data concerning the time span necessary for a population subjected to pluri‐decennial harvesting pressure to return to its pristine status. Here, we present a multi‐annual data set gathered from the Marine Protected Area (MPA) of Portofino, which hosts the most important shallow‐water coral populations in the Ligurian Sea and was subjected to strong harvesting pressure from the 1950s to the early 1970s. Quantitative comparison of the population structure data recorded in 1964, 1990 and 2012 indicated a strong size increase of the colonies (from 3 to 8 g mean weight), resulting in an increase in colony biomass from 300 to the current 1500 g·m^?2. As a consequence, over the same span of time, the density of colonies has slightly decreased. The role of mass mortality phenomena, like that occurred in this area during 1999, as possible biological features triggering the switch of red coral populations from a ‘grass plain‐like’ towards a ‘forest‐like’ structure, is discussed. All these data indicate that the instigation of MPAs is a winning strategy in the conservation of this precious species and similar management plans should also be evaluated for the protection of the deep benthic communities thriving on off‐shore banks.