Regime shift triggered by an extreme climatic event in an oligotrophic mountain lake

Presenta: Isabella Bertani ( LifeWatch-Ita, Centro Tematico Interazioni, CNR-IBAF, Monterotondo Scalo )

Climatic extremes, especially heatwaves and droughts, have increased in frequency, duration and magnitude in many regions of the world as a result of climate change, and this trend is predicted to continue, thereby raising urgent questions regarding their ecosystem-scale consequences on freshwater systems. We explored the impacts of a summer heatwave on a small, stratifying lake that is part of the Italian LTER Network. A sudden transition from a phytoplankton- to a macrophyte-dominated regime occurred during the heatwave. We investigated candidate mechanisms driving the switch from pelagic to benthic control of primary production, and we examined physico-chemical and biological time series to identify the major ecosystem-level consequences of the switch. Our results provide evidence of abrupt and extensive ecological changes that are indicative of a regime shift. We show that ecological implications of the shift propagate across multiple trophic levels and determine marked changes in community structure that persist long after the climatic anomaly.

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Moss bags per il monitoraggio dei micro-inquinanti nelle acque continentali

Presenta: Mattia Cesa (Università di Trieste)

Disporre di bio-accumulatori per il monitoraggio chimico dei corpi idrici e per l'analisi delle tendenze temporali è un'esigenza ormai pressante nell'attuale contesto normativo. I muschi acquatici offrono una sorprendente combinazione di sensibilità, resistenza e versatilità nell'implementazione di monitoraggi ed indagini ambientali.
L'Università di Trieste ha investito 10 anni di studio, sperimentazione ed applicazione della tecnica dei 'moss bags' per il monitoraggio degli elementi in tracce in svariati contesti. Presto saranno pubblicate dall'ISPRA le linee guida per l'utilizzo di questo metodo, che potrebbe essere impiegato anche per il monitoraggio di sostanze prioritarie e contaminanti emergenti.

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Evaluation of bioaccumulation processes of
Brominated Flame Retardants (BFRs) in biotic matrices

Presenta: Giulia Poma ( CNR-IRSA, Brugherio )

The global reduction in the use of PBDEs and HBCD as flame retardants has opened the way for the introduction of “novel” BFRs (nBFRs) in place of the banned formulations, indicating those BFRs that are new in the market or newly/recently observed in the environment in respect to PBDEs and HBCD. Consequently, consumption and production of these nBFRs will keep rising, and increasing environmental levels of these chemicals are expected in the near future.
In Italy, previous studies showed high concentrations of PBDEs in the Varese province due to the presence of a great number of textile and plastic industries, and particularly in the sediments of Lake Maggiore. For these reasons, the present work aimed to evaluate the presence, and the potential bioaccumulation and biomagnification processes of six different classes of BFRs (PBDEs, HBCD, DBDPE, BTBPE, HBB and PBEB) in the Lake Maggiore ecosystem, with particular regard to abiotic (lake and river sediments) and biotic (zebra mussels, zooplankton, and three fish species) matrices.

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Ecosistemi di acque arsenico ferruginose:
indagini preliminari in Valle Anzasca

Presenta: Nicoletta Guerrieri ( CNR-ISE, Verbania )

La Valle Anzasca è una delle valli dell’Ossola, situata nella parte Nord Occidentale del Piemonte, nelle Alpi Pennine. La Valle si sviluppa dal massiccio del Monte Rosa, dove nasce il torrente Anza, fino alla sua confluenza con il Toce. A metà Valle Anzasca si trova un affluente particolare del torrente Anza, il Rio Rosso, caratterizzato da acque arsenico ferruginose. Il torrente nasce nell’antica miniera dei Cani, una miniera aurifera non più attiva, nel Comune di Vanzone con San Carlo. Le acque che fuoriescono dalla miniera, note per il loro possibile impiego terapeutico termale, scorrono lungo il versante tra San Carlo e Vanzone formando una spettacolare cascata, attraversano il paese e raggiungono il torrente Anza.
L’aspetto di queste acque è decisamente particolare, essendo molto ricche in ferro e tutte le superfici toccate dall’acqua sono ricoperte da una patina rosso-ocracea. La loro composizione chimica è insolita e determina la peculiarità di questo sito, in cui si trovano poche forme di vita, molto interessanti per la loro capacità di adattamento a condizioni estreme. Indagini preliminari sulla chimica delle acque e la concentrazione dei metalli, sulla componente fitobentonica e sui macroinvertebrati dell’alveo sono state condotte nel 2013 dal CNR ISE VB in collaborazione con la sede di Pisa, l’Università degli Studi di Milano e l’Università del Piemonte Orientale. Tali indagini dimostrano come l’ambiente oggetto dello studio presenti caratteristiche rilevanti meritevoli dell’azione di programmi di ricerca.

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Giornata di Studio
con CNRS Francia

Sedimentary archives to infer ecosystem response to disturbance

10.30-11.00
Michel MAGNY, and LAMA Members

North-south palaeohydrological contrasts in the central Mediterranean during the Holocene: tentative synthesis and working hypotheses

On the basis of a multi-proxy approach and a strategy combining lacustrine and marine records along a north-south transect, data collected in the Central Mediterranean within the framework of a collaborative project have led to reconstruction of high-resolution and well-dated palaeohydrological records and to assessment of their spatial and temporal coherency. Data give evidence of contrasting palaeohydrological patterns operated throughout the Holocene, both on millennial and centennial scales. Comparison between available palaeohydrological data for the whole Mediterranean suggests possible influences of forcing factors and general atmospheric circulation patterns.

11.00-11.30
Laurent MILLET

Subfossil chironomids in paleolimnology: from the inference of temperature changes to the reconstruction of lake functioning history

In lakes, chironomid larvae (Insecta Diptera) are benthic organisms that produce chitinous remains (head capsules) during their development. Past changes in communities are reconstructed after extraction and identification of head capsules preserved in the sediment. Chironomid assemblages are potentially affected by a variety of environmental conditions interacting in complex ecological processes. Inferring temperature changes from a chironomid sequence using a transfer function assumes that the chironomid assemblages respond, directly or indirectly, to temperature. We will present temperature reconstructions for the last 1500 years derived from chironomid records of three neighboring lakes in the Northern French Alps. In addition to temperature, the most commonly recognized influencing factors are trophic status, oxygen conditions and organic matter in the sediment. In the bottom of deep stratified lakes, the sensitivity of the bottom community to changes in oxygen availability derives from the differential behavioural and/or physiological adaptations of the taxa to survive under hypoxia of variable degree. As a last example, we will present the results from the multiproxy study (IPER-RETRO project) carried out at Lake Annecy (French Alps).

11.30-12.00
Simon BELLE

Current states and ecological trajectories of lakes over the last 1500 years: the study of the biological and biogeochemical responses to disturbances

The evolution of lake is determined by “natural” (climate, lake ontogeny) and “anthropic” (agricultural development, fish introduction, pollutants…) factors (Leavitt et al., 2009). Because monitoring records exist since the early XX° century for only a few lakes, paleolimnological studies are key approaches to understand the response of ecosystems to disturbance. We conducted a multi-proxy paleolimnological investigation to understand: (i) the biological response (Chironomid assemblages) and (ii) the changes in carbon cycle (in particular methanogenesis). 15 lakes, belonging to different typologies and presenting different stories in land use and occupation, have been studied from Jura Mountains to Greenland

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