1,721,141 research outputs found
Toxins in biofilms of lakes and rivers, an emerging threat for public health in a scenario of climate changes
Full text linkCyanobacteria constitute a health hazard in freshwater environments due to the ability to produce toxic metabolites. Animals and humans can be harmed upon exposure to water containing high levels of cyanotoxins that can occur during intense blooms. Toxin cyanobacteria blooms represent a relevant problem in many lakes and reservoirs worldwide and they are therefore routinely monitored by health/environmental authorities. Microcystins and anatoxins are the most common toxins produced by planktonic cyanobacteria. In the last years more and more reports are being published about the occurrence of toxic cyanobacteria in benthic mats (biofilms) growing on rocks, sediment, or macrophytes on the shores of lakes or rivers. The concentration of toxins in biofilm (especially of anatoxins) can reach very high levels, sufficient to cause the death of dogs and cattle. Differently from planktonic cyanobacteria, there is no regular monitoring of benthic cyanobacteria by authorities. It is therefore important to conduct more studies aimed at assessing the real relevance of this phenomenon in aquatic environments. Additionally, the impact of ongoing climate changes on the ecological aspects of these organisms are needed. Recent investigations conducted in the frame of local and international projects (i.e., Eco-AlpsWater project, financed by the EU-Interreg Alpine Space program) has offered the occasion of running a survey on some lakes and rivers in Europe, in particular in the Alpine region. Results have demonstrated that toxic cyanobacteria are present in biofilm collected from stones on the shores of some lakes. A comprehensive analytical effort was conducted by means of LC-MS/MS, which showed that anatoxins are the most relevant toxins in biofilms. In particular, two congeners were found to be the most represented: anatoxin-a and homoanatoxin-a. The toxin content in samples showed also a big spatial heterogeneity with up to two orders of magnitudes differences from samples taken meters away from each othe
Platinum complexes with one monodentate ligand (1-methylbenzimidazole or antiviral ribavirin) flanked by two cis-NMe2 groups: informative models for assessing interligand interactions
No full textMetabolic profiles of cyanobacteria isolated from Italian perialpine lakes
Full text linkA comparative profiling of the secondary metabolism of cyanobacteria isolated from Italian perialpine lakes
has been attempted. Cultures of Aphanizomenon flos-aquae, Dolichospermum lemmermannii, Microcystis aeruginosa,
Planktothrix rubescens, and Tychonema bourrellyi were obtained from lakes Garda, Idro, and Caldonazzo. LC-MS/MS
analysis were used for characterizing the strains’ extracts. A target analyis aimed at assessing the the toxic profile
(microcystins, nodularins, anatoxins, cylindrospermopsins, PSP) was performed; it revealed the production of toxic
peptides (microcystins) in M. aeruginosa and P. rubescens, of toxic alkaloids (anatoxin-a and possibly some paralytic
shellfish toxins) in T. Bourrellyi, and finally no production of toxins in Aph. flos-aquae and D. Lemmermannii. An
untargeted analysis aimed at comparing the capability of the cyanobacterial species to produce peptidic metabolites,
allowed the detection of over 300 different peptides, in a mass range between 400 and 2000 Da. The majority of
compounds with masses between 500 and 1200 Da (corresponding to many non-ribosomal peptides) was produced
by the two species M. aeruginosa and P. rubescens, which show a much higher capability of producing these
compounds compared to the others. Microcystins, aeruginosins and anabaenopeptins were the most represented
classes of compounds
Co-occurrence of anatoxin-a and microcystins in Lake Garda and other deep subalpine lakes
Full text linkCyanotoxins are a global concern in freshwaters and eutrophication and climate changes can have synergistic effects in exacerbating
the problem. The deep perialpine lakes are a group of lakes of huge economic and naturalistic importance located at the border of the
Alps. At the southern border of the Italian and Swiss Alps, the largest waterbodies include the lakes Garda, Iseo, Como, Lugano and
Maggiore (Deep Subalpine Lakes, DSL). Together with eutrophication (during the 1960s and 1970s) and re-oligotrophication (from
the 1990s onward) these lakes have been experiencing warming and increase of the water column stability. These changes had a strong
impact on the phytoplankton (including cyanobacteria) community. Four DSL (lakes Garda, Iseo, Como and Lugano) have been
studied with the aim of comparing their toxic potential. For one of them (Lake Garda) an 8 years survey was conducted, allowing a
long-term trend analysis. Toxin analysis was conducted on a monthly basis by targeted LC-MS/MS. A screening for anatoxins,
cylindrospermopsins, saxitoxins, microcystins (MCs) and nodularins was carried out. Among all the listed toxins, only one anatoxin
and five MCs were detected in the lakes. In particular, the alkaloid anatoxin-a (ATX) was found dominant in lakes Garda, Iseo and
Como, and absent in Lake Lugano; the MC-[D-Asp3]RR was found as the most abundant MC in all four lakes. Four other less abundant
MCs were also found. The two major toxins are produced by two different cyanobacteria, Tychonema bourrellyi (J.W.G. Lund)
Anagnostidis & Komárek and Planktothrix rubescens (De Candolle ex Gomont) Anagnostidis & Komárek, which share however a
number of ecological traits. Peaks of these toxins occurred in warmer months (typically between May and September) in the thermocline
layer (around 20 m, in the considered lakes). In summer 2016, the highest concentrations of ATX and total MCs were registered in
Lake Iseo (1100 and 430 ng L–1, respectively), while in the other lakes values were approximately twice lower. In the lakes where it
was present, ATX peak levels were much higher than MCs, thus highlighting the necessity of including ATX in the procedures of risk
assessment. The importance of ATX is expected to further grow in the future with respect to MCs, as demonstrated by the long-term
trend analysis carried out in Lake Garda that showed a clear decline for MCs from 2009 till 2016 and a relative constancy of ATX
Toxins of freshwater microorganisms: from bio- to chemodiversity
No full textCyanobacteria are prokaryotic microorganisms that are present in all freshwater environments. A certain number of cyanobacterial species have the ability of producing toxic secondary metabolites. The massive growth (or bloom) of toxigenic cyanobacteria can lead to high concentrations of toxins in the water, thus posing a threat to human health. Eutrophication is the main driver of cyanobacterial blooms, but ongoing climate changes can exacerbate the problem. Cyanobacterial toxins (cyanotoxins) are secondary metabolites with a huge chemical diversity due to the high flexibility of their biosynthetic pathways.1 Research conducted in the last fifteen years at Fondazione Edmund Mach has revealed that the biosynthetic pathways are common to all toxigenic cyanobacteria, but that the resultant toxic molecules are very dependent on the species.2 For instance, the cyanobacteria Planktothrix rubescens and Microcystis aeruginosa (among the most frequent responsible of toxic blooms around the world) both have the same gene cluster of the hepatotoxic microcystins (MC), but they synthetize different variants of MC. Moreover, the same set of MC are produced in different ratios by different strains of P. rubescens. These examples show how an integrated biological and chemical approach can be very effective in studying toxigenic cyanobacteria. This approach has demonstrated to be very useful in addressing the toxic potential of populations of cyanobacteria in different natural lakes.3 The presence of cyanotoxins in freshwaters is a matter that is taken into consideration by legislation in most countries and specific monitoring programs are routinely carried out by sanitary/environmental agencies. An emerging issue that is not yet considered by legislation is the presence of toxic cyanobacteria attached to different types of substrates (rocks, stones, vegetation) on the shores of lakes and rivers. Our recent studies revealed that some potent neurotoxins (anatoxins) can be produced in very high quantities by cyanobacteria growing in these environments. Such “biofilms” can constitute a relevant sanitary problem, considered that they can be easily accessed by people and animals walking on the shores
Inter-year and inter-season variability of zooplankton of a mountain lake with a special emphasis on under-ice communities
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Disentangling cyanobacterial diversity in a large perialpine lake using highthroughput sequencing and culture dependent approaches
Full text linkBiomonitoring survey of the hydrographical network in a MAB UNESCO Biosphere Reserve
Full text linkThe knowledge of microbial biodiversity (bacteria and protists) in aquatic ecosystems is far from complete. This is mainly due to the inadequacy of conventional taxonomic identifications, which are based on the discrimination of diacritical morphological traits. Further, investigations are mainly focused on specific lake and river typologies that are usually also of interest for economic exploitation, often disregarding the small and/or ephemeral water bodies. Nevertheless, due to their physiographical complexity and temporal dynamics, these neglected hydrographical elements can host a vast microbial diversity. In order to fill the gap in the biodiversity estimates in the Alpine region, we carried out a survey using high throughput sequencing (HTS) of 16S and 18S rDNA markers from water and sediments collected in the MAB UNESCO Alpi Ledrensi and Judicaria Biosphere Reserve (Project Acqua Viva). The study sites are located between Lake Garda and the Brenta Dolomites, and include natural environments in a semi- anthropized Alpine context with agricultural and tourist vocation. The survey was carried out during the summer 2019, covering 20 sites of different sizes and characteristics, including lakes, alpine pasture ponds and wetlands. The results allowed disclosing a high number of amplicon sequence variants (ASVs) belonging to a wide variety of bacterial and protists groups, and significant differences linked to lake and sample typologies. Despite a wide presence of potentially toxigenic cyanobacteria, microcystins and anatoxin-a were detected only in a few water bodies, including Lake Ledro, which showed the presence of both Planktothrix rubescens and Tychonema bourrellyi in the pelagic samples
La gestione dei grandi laghi europei: un'esperienza multidisciplinare nell'ambito del progetto EULAKES (Central Europe)
No full textLa gestione corretta di un lago prevede la formulazione di piani per lo
sfruttamento della risorsa idrica (p.es. irrigazione, acqua potabile, attività ricreative)
che tengano conto dei specifici tratti ecologici e delle specifiche vulnerabilità del lago e
che siano, quindi, “sostenibili”. I fattori che maggiormente mettono a rischio la qualità
dell’ambiente lacustre e quindi il suo utilizzo sono l’impatto antropico e il
cambiamento climatico. Se gli effetti dell’impatto antropico (inquinamento,
denaturalizzazione, iper-sfruttamento) sono abbastanza noti e “controllabili”, gli effetti
dei cambiamenti climatici sono meno conosciuti e più difficili da prevedere. Inoltre,
alcuni effetti dei cambiamenti climatici, quali l’innalzamento della temperatura
dell’acqua e la maggiore frequenza di eventi atmosferici estremi, oltre a modificare
l’ecosistema in modo diretto, possono avere un effetto sinergico con i fattori antropici,
causando ad esempio un aumento della concentrazione di inquinanti e nutrienti
nell’acqua. Nei piani di gestione del lago occorre quindi tenere conto degli impatti
antropici già presenti, di quelli possibili in futuro, di quali sono i cambiamenti in atto o
futuri dovuti al clima, in modo da permettere l’adozione di adeguate strategie che
consentano una mitigazione degli effetti negativi o un efficace adattamento del
sistema alle nuove condizioni.
Negli anni passati, il gruppo di Idrobiologia della Fondazione Edmund Mach, ha
partecipato ad un progetto finanziato dal “Central Europe Program” avente come
obiettivo la definizione di linee guida transnazionali per una gestione sostenibile dei
laghi. Il progetto (acronimo EULAKES) ha riguardato quattro laghi dell’Europa Centrale
- Lago di Garda (Italia), Lago Balaton (Ungheria), Lago Charzykowskie (Polonia) e Lago
Neusiedl (Austria) - ed ha messo attorno ad un tavolo scienziati, autorità locali e stakeholders,
con l’obiettivo di definire strategie di sviluppo sostenibile dei laghi basate sulle
più recenti acquisizioni della ricerca scientifica in campo limnologico. Il progetto ha
riguardato sia aspetti strettamente ambientali, sia economici e socio-culturali. In tre
anni di attività, sono state condotte attività di ricerca volte a definire lo “stato di
salute” dei laghi e le condizioni di riferimento antecedenti il maggiore impatto
antropico, e a migliorare le conoscenze sulle vulnerabilità e sui rischi futuri in un
contesto di crescente impatto antropico e cambiamento climatico
- …
