Alessandro Oggioni

Phytoplankton assemblage at equilibrium in large and deep subalpine lakes: a case study from Lago Maggiore (N. Italy)

In 1996, we studied the phytoplankton seasonal succession in Lago Maggiore (N. Italy) through weekly sampling. Such a frequency enabled us to evaluate the changes of the phytoplankton assemblage in the light of the equilibrium and non-equilibrium theories. The distinct phases of changing of the species composition were identified separating the samples by means of cluster analysis and non-metric multidimensional scaling (NMDS). We recognised well distinct phytoplankton associations, whose seasonal succession followed a clear cyclic path throughout the year, with spring and summer phases respectively characterised by a rapid turn-over of the assemblages and by a relative stability. Moreover, we observed an increase of species number and Shannon-Wiener diversity during the spring, followed by a summer decline of the diversity in spite of an unchanged species number. Because of the dominance of the same few species for about two months during summer, coupled with small fluctuations of the total biomass, we could identify the summer assemblage as a steady state assemblage. The aim of the present contribution, although describing the whole seasonal succession, is to draw the attention towards the species composition at the steady state, taking into account the functional properties of the species involved. The possible role of the metalimnetic niche in selecting a particular summer assemblage in deep and large lakes will be discussed.

Seasonal morphological plasticity of phytoplankton in Lago Maggiore (N. Italy)

During the year 2002, the size variability of most of the species found in Lago Maggiore was analysed in detail, measuring through image analysis the main morphological parameters (maximum linear dimension, surface, volume) of the algal cells. Many individuals belonging to the same species were measured sampling by sampling, collecting about 28,000 data.This data set allowed us to evaluate the morphological plasticity of many species across the seasonal succession: through multivariate statistical analysis we compared the changes of cell volume, cell surface, maximum linear dimension and surface-to-volume ratio to the fluctuations of the main physical and chemical parameters.The responses we observed were variable, depending on the different taxonomic groups or species as well as on the morphometric parameter considered. As a general pattern, a strong seasonality of the size changes was observed, mainly dependent on the gradients of nutrients and temperature.

Resource ratio and human impact: how diatom assemblages in Lake Maggiore responded to oligotrophication and climatic variability

Diatoms have been often used to track trophic changes from sedimentary records: recent studies demonstrated that these organisms can even be valuable indicators of climatic variability, although it is often difficult to discriminate the role of trophic and climatic drivers. Moving from the hypothesis that oligotrophication and climate affected the composition of the diatom assemblages by changing the resource ratio, we analysed the vernal diatoms succession in Lake Maggiore, between 1984 and 2007, using multivariate techniques (cluster analysis, canonical correspondence analysis, multivariate regression trees), in order to single out the oligotrophication effects from those attributable to climatic variability. Our results point out that Si, TP, temperature and wind emerged as key explanatory variables in species selection, with a stronger link between trophic and climatic drivers after the lake reached a stable oligotrophic status. Peculiar climate-driven events (deep mixing and floods) affected the in-lake Si:P ratio, giving an advantage to diatoms that are excellent P, but poor Si competitors. The classical role of Fragilaria and Tabellaria as early-warning indicators of eutrophication should be reconsidered, taking into account that both can be useful indicators of climate change, when links between their physiological resource needs and environmental data coming from robust limnological investigations can be established.

Phytoplankton production in Italian freshwater and marine ecosystems: State of the art and perspectives

The present work aims at evaluating the state of art of phytoplankton production research in Italy. We present a synthesis of the main results achieved in three ecosystems where primary production studies have been carried out most intensively: a large subalpine lake (Lago Maggiore, LM), a shallow marine ecosystem with strong fluvial influence (the Northern Adriatic Sea, NAS), and a coastal area of the Southern Tyrrhenian Sea (the Gulf of Naples, GoN). The present yearly production values are around 150 g C m−2 yr−1 in LM and GoN; this ranges between 80 (offshore) and 150 g C m−2 yr−1 (coast) in the NAS. The temporal and spatial variations of phytoplankton production appeared, in each ecosystem, in accordance with the trophic changes. Significant correlations between production, chlorophyll, and light were generally observed for LM and for GoN. On the contrary, these parameters were poorly correlated in the NAS, hampering the use of predictive models in this ecosystem. Discrepancies between primary production and the actual phytoplankton biomass changes were observed across trophic gradients: the largest part of the carbon that is photosynthetically produced does not seem to be transformed into new phytoplankton biomass, strongly affecting the interpretation of the production figures in the ecosystems.

RITMARE: Semantics-aware Harmonisation of Data in Italian Marine Research

Abstract RITMARE is a Flagship Project by the Italian Ministero dell’Istruzione, dell’Universita e della Ricerca (MIUR) and coordinated by the National Research Council (CNR). It aims at the interdisciplinary integration of national marine research. In pursuing a Linked Open Data (LOD) vocation, the RITMARE sub-project 7 is building the necessary domain-related data structures by leveraging existing RDF-based schemata and sources. These data structures are grounding semantics-aware profiling of end users, data providers, and resources. The goal is designing a flexible infrastructure that adapts to the audiences specificities.

Sensor metadata blueprints and computer-aided editing for disciplined SensorML

The need for continuous, accurate, and comprehensive environmental knowledge has led to an increase in sensor observation systems and networks. The Sensor Web Enablement (SWE) initiative has been promoted by the Open Geospatial Consortium (OGC) to foster interoperability among sensor systems. The provision of metadata according to the prescribed SensorML schema is a key component for achieving this and nevertheless availability of correct and exhaustive metadata cannot be taken for granted. On the one hand, it is awkward for users to provide sensor metadata because of the lack in user-oriented, dedicated tools. On the other, the specification of invariant information for a given sensor category or model (e.g., observed properties and units of measurement, manufacturer information, etc.), can be labor- and timeconsuming. Moreover, the provision of these details is error prone and subjective, i.e., may differ greatly across distinct descriptions for the same system. We provide a user-friendly, template-driven metadata authoring tool composed of a backend web service and an HTML5/javascript client. This results in a form-based user interface that conceals the high complexity of the underlying format. This tool also allows for plugging in external data sources providing authoritative definitions for the aforementioned invariant information. Leveraging these functionalities, we compiled a set of SensorML profiles, that is, sensor metadata blueprints allowing end users to focus only on the metadata items that are related to their specific deployment. The natural extension of this scenario is the involvement of end users and sensor manufacturers in the crowd-sourced evolution of this collection of prototypes. We describe the components and workflow of our framework for computer-aided management of sensor metadata.

A Holistic, Semantics-aware Approach to Spatial Data Infrastructures

We present a novel approach to the management of Spatial Data Infrastrutures that leverages semantics-aware context information to model the distinct aspects involved in the management of spatial data. RDF-based schemata are employed for encoding information on the user community, the terminologies in use in a specific research domain, gazetteer information representing the physical landscape hosting data and, last but not least, spatial resource metadata. The data structures are then interconnected to enable seamless exploitation for metadata creation and resource discovery, which we demonstrate through a worked-out example of SPARQL query on RDF graph data. The methodology is being applied by by the National Research Council (CNR) of Italy to support creation of a distributed infrastructure for marine data in the context of the RITMARE Flagship Project.

The RITMARE Starter Kit bottom-up capacity building for geospatial data providers

Capacity building by data providers is a fundamental task in the creation of a decentralized Spatial Data Infrastructure. This challenge has been tackled in the RITMARE Flagship Project by providing the Starter Kit, a comprehensive set of domain-oriented software components that exposes standard services for the management of geospatial information. We report on the characteristics of this toolkit, developed by the National Research Council of Italy (CNR), particularly with regard to the underlying service-oriented architecture and the novel semantics-aware methodology that is proposed for metadata editing.

Plankton dynamics across the freshwater, transitional and marine research sites of the LTER-Italy Network: patterns, fluctuations, drivers

A first synoptic and trans-domain overview of plankton dynamics was conducted across the aquatic sites belonging to the Italian Long-Term Ecological Research Network (LTER-Italy). Based on published studies, checked and complemented with unpublished information, we investigated phytoplankton and zooplankton annual dynamics and long-term changes across domains: from the large subalpine lakes to mountain lakes and artificial lakes, from lagoons to marine coastal ecosystems. This study permitted identifying common and unique environmental drivers and ecological functional processes controlling seasonal and long-term temporal course. The most relevant patterns of plankton seasonal succession were revealed, showing that the driving factors were nutrient availability, stratification regime, and freshwater inflow. Phytoplankton and mesozooplankton displayed a wide interannual variability at most sites. Unidirectional or linear long-term trends were rarely detected but all sites were impacted across the years by at least one, but in many case several major stressor(s): nutrient inputs, meteo-climatic variability at the local and regional scale, and direct human activities at specific sites. Different climatic and anthropic forcings frequently co-occurred, whereby the responses of plankton communities were the result of this environmental complexity. Overall, the LTER investigations are providing an unparalleled framework of knowledge to evaluate changes in the aquatic pelagic systems and management options.

Interoperable Sharing and Visualization of Geological Data and Instruments: A Proof of Concept.

Traditionally, maps and data were analyzed and created by desktop software tools. Today, thanks to World Wide Web, open source software tools and international standards, practitioners and researchers can share maps, data, and measures. Sharing can be done with different software tools, proprietary or open source, and with varying degrees of interoperability. Most geological maps and data collected by instruments are produced by governmental organizations and they are encoded in official languages and data schemas of their producers. Linguistic barrier, different visual representations and data schemas hinder the usefulness of online maps and data, obtained from different sources. In the present paper, we report a research aiming to overcome these aforementioned barriers. To this end, after having described their main characteristics, we exploited and summarized the main findings of using geoscience thesauri, international standards for web sharing, visual and data harmonization. We used GeoScience Markup Language (GeoSciML-Portayal) to harmonize geological maps collected in the context of a multidisciplinary study focused on a coastal area located in Southern Italy, (Costa Viola); Sensor Metadata Language (SensorML) to describe geological instruments; Observations and Measurements (O&M) to harmonize geological data collected by instruments. We used geoscience thesauri based on Simple Knowledge Organization System (SKOS) to enrich semantically the aforementioned geological maps, data and instruments. A distributed Spatial Data Infrastructure (SDI), implemented using free and open source software for geospatial (FOSS4G), was provided taking advantage on Open Geospatial Consortium (OGC) standards to share data and information in an interoperable, harmonized and semantically enriched way.