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The Ross Sea is one of the most productive areas of the Southern Ocean and includes several functionally different marine ecosystems. With the aim of identifying signs and patterns of microbial response to current climate change, seawater microbial populations were sampled at different depths, from surface to the bottom, at two Ross Sea mooring areas southeast of Victoria Land in Antarctica. This oceanographic experiment, the XX Italian Antarctic Expedition, 2004-05, was carried out in the framework of the ABIOCLEAR project as part of LTER-Italy. Here, microbial biogeochemical rates of respiration, carbon dioxide production, total community heterotrophic energy production, prokaryotic heterotrophic activity, production (by3H-leucine uptake) and prokaryotic biomass (by image analysis) were determined throughout the water column. As ancillary parameters, chlorophylla, adenosine-triphosphate concentrations, temperature and salinity were measured and reported. Microbial metabolism was highly variable amongst stations and depths. In epi- and mesopelagic zones, respiratory rates varied between 52.4–437.0 and 6.3–271.5 nanol O2l-1h-1; prokaryotic heterotrophic production varied between 0.46–29.5 and 0.3–6.11 nanog C l-1h-1; and prokaryotic biomass varied between 0.8–24.5 and 1.1–9.0 µg C l-1, respectively. The average heterotrophic energy production ranged between 570 and 103 mJ l-1h-1in upper and deeper layers, respectively. In the epipelagic layer, the Prokaryotic Carbon Demand and Prokaryotic Growth Efficiency averaged 9 times higher and 2 times lower, respectively, than in the mesopelagic one. The distribution of plankton metabolism and organic matter degradation was mainly related to the different hydrological and trophic conditions. In comparison with previous research, the Ross Sea results, here, evidenced a relatively impoverished oligotrophic microbial community, throughout the water column.

During summer 2014, three hypersaline brines were discovered in two frozen lakes of Boulder Clay (Northern Victoria Valley, Antarctica). Ongoing research seeks to gain novel insights on the microbial ecology of such environments, in order to further the understanding of life adaptation to extreme conditions. To this aim, the abundance of prokaryotic cells (including cell morphologies and size for biomass conversion), the amount of viable cells (in terms of membrane-intact cells and respiring cells), the viral count, the physiological profiles at community level and the main microbial enzymatic activities were described. The brines differed each other in terms of prokaryotic cells' abundance, size, and viability as well as viral abundance. Cell morphotypes and metabolic responses also varied among the brine samples. Underground interconnections were likely to occur, with the microbial community becoming more abundant and structured to better exploit the limited resource availability. Overall, complex interactions among multiple environmental factors, including marine water origin, depth horizon, isolation time of the brines, and climatic variations, reflected on the microbial community distribution patterns and highlighted the need to preserve these niches of extreme life.

Different polar environments (lakes and glaciers), also in Antarctica, encapsulate brine pools characterized by a unique combination of extreme conditions, mainly in terms of high salinity and low temperature. Since 2014, we have been focusing our attention on the microbiology of brine pockets from three lakes in the Northern Victoria Land (NVL), lying in the Tarn Flat (TF) and Boulder Clay (BC) areas. The microbial communities have been analyzed for community structure by next generation sequencing, extracellular enzyme activities, metabolic potentials, and microbial abundances. In this study, we aim at reconsidering all available data to analyze the influence exerted by environmental parameters on the community composition and activities. Additionally, the prediction of metabolic functions was attempted by the phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) tool, highlighting that prokaryotic communities were presumably involved in methane metabolism, aromatic compound biodegradation, and organic compound (proteins, polysaccharides, and phosphates) decomposition. The analyzed cryoenvironments were different in terms of prokaryotic diversity, abundance, and retrieved metabolic pathways. By the analysis of DNA sequences, common operational taxonomic units ranged from 2.2% to 22.0%. The bacterial community was dominated by Bacteroidetes. In both BC and TF brines, sequences of the most thermally tolerant and methanogenic Archaea were detected, some of them related to hyperthermophiles.

Svalbard archipelago is experiencing the effects of climate changes (i.e., glaciers' thickness reduction and glacier front retreat), but how ice melting affects water biogeochemistry is still unknown. Microbial communities often act as environmental sentinels, modulating their distribution and activity in response to environmental variability. To assess microbial response to climate warming, within the ARctic: present Climatic change and pAst extreme events (ARCA) project, a survey was carried out along a transect in Konsfjorden from off-shore stations towards the Kronebreen glacier. Total bacterial abundance and the fraction of actively respiring cells (labelled by cyanotetrazolium chloride, CTC), cultivable heterotrophic bacterial abundance, and extracellular enzymatic activities (leucine aminopeptidase (LAP), beta-glucosidase (GLU), and alkaline phosphatase (AP)) were measured. In addition, water temperature, salinity, dissolved oxygen, turbidity, total suspended matter (TSM), particulate and chromophoric dissolved organic matter (CDOM), chlorophyll-a (Chl-a), and inorganic compounds were determined, in order to evaluate whether variations in microbial abundance and metabolism were related with changes in environmental variables. Colder waters at surface (3.5&ndash, 5 m) depths and increased turbidity, TSM, and inorganic compounds found at some hydrological stations close to the glacier were signals of ice melting. CDOM absorption slope values (275&ndash, 295 nm) varied from 0.0077 to 0.0109 nm&minus, 1, and total bacterial cell count and cultivable heterotrophic bacterial abundance were in the order of 106 cells/mL and 103 colony forming units/mL, respectively. Enzymatic rates &lt, 1.78, 1.25, and 0.25 nmol/l/h were recorded for AP, LAP, and GLU, respectively. Inorganic compounds, TSM, and turbidity correlated inversely with temperature, AP was significantly related with CDOM absorption spectra and heterotrophic bacteria (r = 0.59, 0.71, P &lt, 0.05), and LAP with Chl-a, Particulate Organic Carbon (POC) and Particulate Organic Nitrogen (PON) (0.97, 0.780, 0.734, P &lt, 0.01), suggesting that fresh material from ice melting stimulated the metabolism of the cultivable fraction.

The peculiar biotechnological applications of Oleispira spp. in the natural cleansing of oil-polluted marine systems stimulated the study of the phenotypic characteristics of the Oleispira antarctica RB-8(T) strain and modifications of these characteristics in relation to different growth conditions. Bacterial abundance, cell size and morphology variations (by image analysis) and hydrocarbon degradation (by gas chromatography with flame ionization detection, GC-FID) were analysed in different cultures of O. antarctica RB-8(T). The effects of six different hydrocarbon mixtures (diesel, engine oil, naval oil waste, bilge water, jet fuel and oil) used as a single carbon source combined with two different growth temperatures (4° and 15 °C) were analysed (for 22 days). The data obtained showed that the mean cell volume decreased with increasing experimental temperature. Three morphological bacterial shapes were identified: spirals, rods and cocci. Morphological transition from spiral to rod and coccoid shapes in relation to the different substrates (oil mixtures) and/or growth temperatures was observed, except for one experimental condition (naval oil waste) in which spiral bacteria were mostly dominant. Phenotypic traits and physiological status of hydrocarbon-degrading bacteria showed important modifications in relation to culture conditions. These findings suggest interesting potential for strain RB-8(T) for ecological and applicative purposes.

Several Italian and Chinese temperate lakes with soluble reactive phosphorus concentrations 20 ?g C L-1h-1) and could favor the release of inorganic phosphorus. High extracellular enzyme activities and phosphorus solubilizing bacteria abundance in sediments accelerated nutrient regeneration. In these conditions, the positive GLU-AP relationship suggested the coupling of carbon and phosphorus regeneration; an efficient phosphorus regeneration and high nitrogen levels (up to 0.067 and 0.059 mg L-1 NH4 and NO3 in Italy; 0.631 and 1.496 mg L-1 NH4 and NO3 in China) led to chlorophyll a peaks of 14.9 and 258.4 µg L-1 in Italy and China, respectively, and a typical algal composition. Conversely, in the oligo-mesotrophic lakes, very low nitrogen levels (in Italy, 0.001 and 0.005 mg L-1 NH4, and NO3, respectively, versus 0.053 and 0.371 mg L-1 in China) induced high LAP, while low phosphorus (33.6 and 46.3 µg L-1 total P in Italy and China, respectively) led to high AP. In these lakes nitrogen and phosphorus regeneration were coupled, as shown by positive LAP-AP relationship; however the nutrient demand could not be completely met without the supply from sediments, due to low enzymatic activity and phosphorus solubilizing bacteria found in this compartment.

The effects of climate change-induced ice melting on the microbial communities in different glacial-fed aquatic systems have been reported, but seasonal dynamics remain poorly investigated. In this study, the structural and functional traits of the aquatic microbial community were assessed along with the hydrological and biogeochemical variation patterns of the Arctic Pasvik River under riverine and brackish conditions at the beginning (May = Ice-melt (−)) and during the ice-melting season (July = Ice-melt (+)). The microbial abundance and morphometric analysis showed a spatial diversification between the riverine and brackish stations. Results highlighted different levels of microbial respiration and activities with different carbon and phosphorous utilization pathways, thus suggesting an active biogeochemical cycling along the river especially at the beginning of the ice-melting period. At Ice-melt (−), Gammaproteobacteria and Alphaproteobacteria were dominant in riverine and brackish stations, respectively. Conversely, at Ice-melt (+), the microbial community composition was more homogeneously distributed along the river (Gammaproteobacteria &gt, Alphaproteobacteria &gt, Bacteroidetes). Our findings provide evidence on how riverine microbial communities adapt and respond to seasonal ice melting in glacial-fed aquatic ecosystems.

Victoria Land permafrost harbours a potentially large pool of cold-affected microorganisms whose metabolic potential still remains underestimated. Three cores (BC1,-2 and -3) drilled at different depths in Boulder Clay (Northern Victoria Land) and one sample (DY) collected from a core in the Dry Valleys (Upper Victoria Valley) were analysed to assess the prokaryotic abundance, viability, physiological profiles and potential metabolic rates. The cores drilled at Boulder Clay were a template of different ecological conditions (different temperature regime, ice content, exchanges with atmosphere and with liquid water) in the same small basin while the Dry Valleys site was very similar to BC-2 conditions but with a complete different geological history and ground ice type. Image-analysis was adopted to determine cell abundance, size and shape as well as to quantify the potential viable and respiring cells by Live/Dead and 5-Cyano-2,3-ditolyl-tetrazolium chloride staining, respectively. Sub-population recognition by apparent nucleic acid contents was obtained by flow-cytometry. Moreover, the physiological profiles at community level by Biolog- Ecoplate(TM) as well as the ectoenzymatic potential rates on proteinaceous (leucine-aminopeptidase) and glucidic (ß glucosidase) organic matter and on organic phosphates (alkaline-phosphatase) by fluorogenic substrates were tested. The adopted methodological approach gave useful information regarding viability and metabolic performances of microbial community in permafrost. The occurrence of a multifaceted prokaryotic community in the Victoria Land permafrost and a large number of potentially viable and respiring cells (in the order of 10+4-10+5) were recognized. Sub populations with a different apparent DNA content within the different samples were observed. The physiological profiles stressed various potential metabolic pathways among the samples and intense utilization rates of polymeric carbon compounds and carbohydrates, mainly in deep samples. The measured enzymatic activity rates suggested the potential capability of the microbial community to decompose proteins and polysaccharides. The microbial community seems to be appropriate to contribute to biogeochemical cycling in this extreme environment.

The retrieval of a polystyrene macro-plastic piece stranded on the shores in King George Island (South Shetlands, Antarctica) gave the opportunity to explore the associated bacterial flora. A total of 27 bacterial isolates were identified by molecular 16s rRNA gene sequencing and 7 strains were selected and screened for their ability to produce biofilm and antibiotic susceptibility profiles. All the bacterial isolates were able to produce biofilm. The Kirby-Bauer disk diffusion susceptibility test to 34 antibiotics showed multiple antibiotic resistances against the molecules cefuroxime and cefazolin (belonging to cephalosporins), cinoxacin (belonging to quinolones) and ampicillin, amoxicillin + clavulanic acid, carbenicillin and mezlocillin (belonging to beta-lactams). The obtained results suggest that plastics can serve as vectors for the spread of multiple resistances to antibiotics across Antarctic marine environments and underline the relevance of future studies on this topic.

Relazione dell'attività svolta nell'ambito della Short Term Mobility (AMMCNT. CNR prot. n. 0070784/2019 del 15/10/2019) presso il CNPq, nell'Istituto di Biologia dell'Università Federale di Rio de Janeiro (UFRJ) (Brasile)

In coastal lakes the role of microorganisms in driving nutrients regeneration at different water depths and in sediments is not yet fully understood. The dynamics of microbial (algal and bacterial) abundance and bacterial activities involved in organic matter transformation were measured, together with nutrient concentrations, through a microcosm experiment set up using the oligotrophic Faro lake as a study model over a total period of 15 days and with a four-day frequency. Water column at different depths (surface, middle and bottom) and interstitial water obtained by sediment centrifugation were used in appropriate ratios (mixed 1:1 with surface waters) to fill 21-Litre plastic aquaria in order to simulate processes occurring in natural conditions. At early experimental period, the sharp decrease of dissolved organic nutrients and the abundant production of leucine aminopeptidase (LAP) and alkaline phosphatase (AP) in correspondence with high phytoplankton abundance in bottom and interstitial water reflected the relevance of organic nutrients for inorganic nutrients regeneration and phytoplankton growth. Size fractionation of LAP and AP as well as the positive relationship between microbial compartments suggested that bacteria and phytoplankton worked in close reciprocal synergy, and coupling of nitrogen and phosphorus regeneration, especially in bottom and interstitial waters, was observed. At later experimental period, the change in bacterial community, especially the increase of filamentous shaped cells, together with a simultaneous increase of protozoan abundance indicated that nutrient replenishment made the microbial loop structure more competitive. In oligotrophic conditions, such as those in Faro lake, organic nutrient enrichment of bottom and interstitial waters was associated with changes in the bacterial community, with consequent stimulation of extracellular enzymes to support phytoplankton growth. Nutrient availability from microbial regeneration resulted in an increased complexity of the microbial loop structure, with bacteria and phytoplankton adopting specific strategies to respond to the changing environment.

Planktonic communities hold a relevant role within the EU Marine Strategy Framework Directive (MSFD). In view of reaching the Good Environmental Status of marine ecosystems, within this Directive the phyto- and zooplanktonic communities have received great attention, while Prokaryotes (Bacteria, Archaea, and Cyanobacteria) have been neglected. Indeed, the relevance of microbes (particularly of the faecal pollution indicators) as water quality indicators, the role that microorganisms play within the biogeochemical fluxes and in the whole ecosystem functioning, are all important features that deserve to be focused within the MSFD. The present study aims at reviewing the main issues where prokaryotic variables find useful application as descriptors of environmental status, trying to develop a panel of prokaryotic indicators suitable for the environmental quality assessment. From a survey of scientific literature and on field datasets, prokaryotic abundance and activities (enzymatic hydrolysis, prokaryotic production, and respiratory rates) are here chosen as early warning sentinels to detect changes in environmental quality, using an integrated approach with trophic (chlorophyll-a, particulate and dissolved organic matter) measurements.

This study was aimed at gaining insights on the prokaryotic community (in terms of both taxonomic composition and activities) inhabiting the active layer at Edmonson Point, an ice-free area on the eastern slope at the foot of Mount Melbourne (Northern Victoria Land, Antarctica). Samples were collected during the thawing period, when microbial physiological activities are restored to utilize previously frozen organic substrates. Despite the very small cell sizes (600 daltons) substrates, as indicated also by the obtained rates of enzymatic hydrolytic activities over proteolytic, glycolitic and phosphoric compounds. Taxonomical composition showed that Proteobacteria, Actinobacteria and Firmicutes dominated the prokaryotic community, with most of their members playing crucial roles in organic matter turnover, as well as nitrogen cycling, or entering a viable but not cultivable state to cope with continuously changing environmental conditions, such as in the case of the active layer. Finally, non-autochthonous bacteria (mainly of marine origin) were detected and they probably contribute to the organic matter turnover within such cold terrestrial habitat. This research provides the first comprehensive account of the prokaryotic communities inhabiting the Antarctic permafrost and contributes to existing information on the response of their abundance and metabolism in a permafrost area that undergoes to seasonal changes (e.g. in terms of temperature, water availability and ice presence).

Plastic pollution is an emerging threat with severe implications on animals' and environmental health. Nevertheless, interactions of plastic particles with both microbial structure and metabolism are a new research challenge that needs to be elucidated yet. To improve knowledge on the effects played by microplastics on free-living and fish gut-associated microbial community in aquatic environments, a 90 days-study was performed in three replicated mesocosms (control-CTRL, native polyvinyl chloride-MPV and weathered polyvinyl chloride-MPI), where sea bass specimens were hosted. In CTRL mesocosms, fish were fed with no-plastic-added food, while in MPV and MPI food was supplemented with native or exposed to polluted waters polyvinylchloride pellets, respectively. Particulate Organic Carbon (POC) and Nitrogen, total and culturable bacteria, extracellular enzymatic activities, and microbial community substrate utilization profiles were analyzed. POC values were lower in MPI than MPV and CRTL mesocosms. Microplastics did not affect severely bacterial metabolism, although enzymatic activities decreased and microbes utilized a lower number of carbon substrates in MPI than MPV and CTRL. No shifts in the bacterial community composition of fish gut microflora were observed by Denaturing Gradient Gel Electrophoresis fingerprinting analysis.

The Ross Sea, one of the most productive seas of the South Ocean, includes polynyas, marginal ice zones, coastal areas and open sea that contribute differently to biological processes. To identifying responses of plankton compartment to climate change, an oceanographic PNRA campaign (P-ROSE Project) was here carried out in January-February 2017. Two polynyas occurred, a small near the Terra Nova Bay (TNB) and a larger one between the Ross Ice Shelf and Cape Adare. The variability of extracellular enzymatic activity (a proxy of organic matter degradation) in relation to environmental conditions (temperature, salinity and total phytoplankton biomass) was studied along longitudinal and latitudinal transects. Hydrolysis rates of aminopeptidase (LAP), beta-glucosidase (GLU) and alkaline phosphatase (AP) and -for the first time in this area- the corrispective free enzymes (dissolved in waters) were determined. Results showed decreasing trends in the TNB from coastal to off-shore stations and from surface to depth for LAP, that were related positively to temperature (T) and negatively to salinity (S) and depth (p

In the Ross Sea, warm Circumpolar Deep Water (CDW) intrudes onto the continental shelf preferably on the western sector and flows into the ice shelf cavities, affecting the ice shelf melting rates. In fact, the intrusion of the warm CDW onto the Antarctic shelf area is one of the recognized drivers of ice shelf melting. Moreover, this water mass is the primary source of heat, salt, nutrients and iron (Fe) onto the Antarctic continental shelves playing an important role on the shelf physical and biological processes. An oceanographic cruise was performed in the framework of the CELEBeR (CDW effects on glacial melting and on bulk of Fe in the Western Ross Sea) project (funded by Italian National Research Programme in Antarctica) in January - February 2017 aboard of R/V Italica, addressed to study microbial community level physiological profiles (by Biolog ecoplate) and extracellular enzymatic activities (EEA) of leucine-aminopeptidase, beta-glucosidase and alkaline phosphatase in the intruding CDW of the Western Ross Sea. The investigated areas covered: a) the Antarctic continental shelf break area near Cape Adare (North Victoria Land); b) the coastal area near the edge of the Mariner and Aviator glaciers; c) the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya. The functional diversity (catabolic potential) was assessed using the Average Well Color Development (AWCD). Moreover, Richness (R) and Shannon-Weaver index (H), analysis of variance (ANOVA) and principal component analysis (PCA) were used to depict the differences of the microbial functional diversity in the studied areas. Differences in potential metabolic pathways were detected in the different sampling areas. The measured enzymatic activity rates suggested the potential ability of the microbial community to decompose proteins, carbohydrates and organic phosphates. Different levels of EEA were measured as a function of the CDW proximity - or not - to the glaciers and the trophism of the investigated area.

Studies in coastal areas of Terra Nova Bay (TNB) highlighted the sudden variability of planktonic biomass with ecological implications on the heterotrophic microbial community and the fate of the organic substance on a seasonal scale. With the aim to monitoring the evolution of the prokaryotic and viral abundance and the hydrolysis of organic matter, in the frame of the CEFA project (Italian PNRA) two fixed stations (Faranda Field - FF; Michaud Pier - MP), were repeatedly sampled. In FF, a sea ice covered station, the prokaryotic and viral abundances were monitored from the 9th of November 2015 to the 19th of January 2016 with Image Analysis (IA) and Cytofluorimetry (FC). Starting from the 4th of January 2016 the potential enzymatic activities on proteins, carbohydrates and organic phosphates were determined. Moreover, the MP station was monitored from the 12th of January to the 8th of February 2016. The prokaryotic abundance in FF station varied in the ranges 0.73-3.38 and 0.26-1.85cellsx105ml-1 by IA and FC, respectively. Cells with high nucleic acid content (HNA) accounted from 32 to 84% of the total FC cells. Virus like particles by FC ranged between 8.08 and 22.3VPLx105ml-1 and V1 group accounted for the 64-94% of the total. The main activity in all samples taken from FF station (under ice) was the phosphatase with the highest values at the beginning of the sampling and showing a decreasing trend when the station was defrosted. This enzyme can be produced in surface water by both bacteria and phytoplankton. The glucosidase activity, showed lower values than phosphatase with a similar trend. The peptidase activities instead increased in the sampling at the end of January in correspondence of the ice absence. In the MP station, the prokaryotic abundance varied in the ranges 1.00-12.3 and 1.03-4.07cellsx105ml-1 by IA and FC, respectively. Cells with high nucleic acid content (HNA) accounted from 47 to 84% of the total FC cells. Virus like particles by FC resulted to be below the detection limits. High variability of enzymatic activities was observed with time in this station. Generally phosphatase prevailed on other activities with the maximum values on the 13rd and 22nd of January; thereafter it decreased with the ice melting. ?-glucosidase, showed peaks on January 16th and from 24th to 29th of January (bay covered by ice), then it decreased. The amino-peptidase showed variable values with peaks on the 12th and 17th of January.

Two distinct pressurized hypersaline brine pockets (named TF4 and TF5), separated by a thin ice layer, were detected below an ice-sealed Antarctic lake. Prokaryotic (bacterial and archaeal) diversity, abundances (including virus-like particles) and metabolic profiles were investigated by an integrated approach, including traditional and new-generation methods. Although similar diversity indices were computed for both Bacteria and Archaea, distinct bacterial and archaeal assemblages were observed. Bacteroidetes and Gammaproteobacteria were more abundant in the shallowest brine pocket, TF4, and Deltaproteobacteria, mainly represented by versatile sulphate-reducing bacteria, dominated in the deepest, TF5. The detection of sulphate-reducing bacteria and methanogenic Archaea likely reflects the presence of a distinct synthrophic consortium in TF5. Surprisingly, members assigned to hyperthermophilic Crenarchaeota and Euryarchaeota were common to both brines, indicating that these cold habitats host the most thermally tolerant Archaea. The patterns of microbial communities were different, coherently with the observed microbiological diversity between TF4 and TF5 brines. Both the influence exerted by upward movement of saline brines from a sub-surface anoxic system and the possible occurrence of an ancient ice remnant from the Ross Ice Shelf were the likely main factors shaping the microbial communities.

The response of both microbial activities and prokaryotic abundances to environmental variability was studied in a transitional Mediterranean system (Oliveri–Tindari, Italy) during two yearly surveys (1997–'98 and 2005–'06). The total enzymatic (leucine aminopeptidase, β-glucosidase, alkaline phosphatase) and respiratory activity rates as well as of the abundances of total prokaryotes, culturable heterotrophic bacteria, faecal coliforms and enterococci were measured in surface waters of four brackish ponds, together with temperature, salinity, dissolved oxygen, pH, inorganic nutrients, chlorophyll- a and particulate organic carbon and particulate nitrogen determinations. The seasonal and interannual patterns of microbial parameters were investigated in relation to environmental variations. Both the microbial activities and the abundances of culturable heterotrophic bacteria, faecal coliforms and enterococci varied significantly among the ponds, reflecting their haline and trophic variability. Significant seasonal and interannual variations were found in the patterns of microbial activity, but not in total prokaryotic abundance, in response to temperature, dissolved oxygen and trophic changes. Microbial parameters showed a different response to environmental variability in the two examined periods: during 1997–'98, increases in the microbial activity rates and culturable bacterial counts were positively related with the trophic changes, while during 2005–'06 the patterns of leucine aminopeptidase, alkaline phosphatase and respiratory activities and of total prokaryotic and culturable bacteria abundances were uncoupled with those of temperature, salinity, dissolved oxygen, particulate organic carbon and chlorophyll- a . Changes in the relative importance of environmental and trophic variables between the two considered periods explain this discrepancy.

Relazione dell'attività svolta durante la Short Term Mobility (AMMCNT. CNR prot. N. 0061011 del 14/09/2016) presso l'Università Federale di Rio de janeiro

The distribution of the prokaryotic biomass (from both abundance and cell volume measurements) and microbial community respiration (by ETS activity) in the main water masses of the Southern Tyrrhenian Sea were studied. The data were collected from surface to the bottom depth (max 3600 m) in July and December 2005. Prokaryotic abundance and microbial respiration were higher in summer than late-autumn and decreased with depth in accordance with the water masses. The opposite was found for the prokaryotic cell volumes that increased with depth and were higher in December. The cell carbon content varied within the water masses and study periods (range 9–34 fg C cell−1) and overestimations and underestimations of biomass there would have been by using the routinely adopted conversion factor (20 fg C cell−1). The depth-integrated respiratory rates resulted comparable in the photic and aphotic layers. In July, 210 and 225 mg C m−2 day−1 in the euphotic and aphotic zones, respectively, were remineralized while in December, 112 and 134 mg C m−2 day−1, respectively, were. Speculations to quantify the carbon flow mediated by microbial community suggested the occurrence of different microbial behavior within the different water masses.

In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C ⁄N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH4 ,N O 2, NO3 ,P O4]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes.

Sinking biogenic particles drive respiration in the ocean interior, help to maintain the ocean's strong vertical gradient of inorganic carbon and related studies are important to determine the flow of organic matter along the water column. Sediment trap studies have shown that a low percentage of the surface primary production reaches the bottom. However, organic matter collected by sediment traps does not take into account the entire pool of oxidable organic matter, which includes the dissolved organic matter present in the seawater. The study of microbial respiration rates instead fills this gap, since respiration includes oxidation of both dissolved and particulate organic mater, providing an integrated estimate of the carbon utilization in the sea. In this context, a study on an Arctic fjord (Kongsfyorden, Svalbard) was done in late summer 2013, with the purpose of knowing the variability of microbial remineralization rates in relation to particulate organic matter over short time scales in a coastal station (water depth ~105 m), where a mooring (Mooring Dirigibile Italia, MDI: 78° 54 .859'N; 12° 15. 411' E) is positioned. A high variability of carbon dioxide production rates was recorded during the sampling days and this result was related to several factors. Useful information may be deducted for modelling studies of carbon flux in similar areas.

Microbial respiratory activity in several sites of the Ross sea was studied in the framework of the Italian National Research Programme in Antarctica (PNRA), with the aim of evaluating the biological pump efficiency and the carbon flux transported by microbes throughout the water column. Recent studies have demonstrated that dissolved organic carbon (DOC) is an important component of the biological pump that assumed in the deep waters a key role as main organic fuel of microbial respiration. Such evidence seem overturned in the Southern Ocean where DOC pool accounted for < 10 % of the remineralization in deep waters. Moreover the euphotic zone of the Ross Sea yielded only a small portion of primary production as DOC (11 %), so that DOC removal by deep convection could be not an important export term due to the small quantity of DOC that accumulates there. The purpose of this study was to investigate the supply and utilization of organic carbon in the aphotic zone of Ross Sea by evaluation of microplankton respiratory activity and to compare the vertical carbon balance with different estimates of export production from the same area and other oceanic regions.

We test the suitability of microbial parameters to assess environmental pressures, and investigate the abundance and phenotypic traits of prokaryotic cells in an Antarctic area. During two oceanographic cruises, carried out in 2001 and 2005, seawater samples were collected in two mooring stations of the Ross Sea. As ancillary parameters, determinations of lipopolysaccharides, chlorophyll a, and/or fractionated adenosine-tri-phosphate were done. Furthermore, in the 2005 survey, six more stations were sampled. Results show that prokaryotic cells--in terms of abundance, shape, and size-- change in relation with environmental changes. Prokaryotic abundance was high, where a strong condition of eutrophication was detected. Sizes of cells showed the prevalence of very small forms ([0.1 lm3), but larger morphotypes were observed in high trophic conditions (till 0.4 lm3). In Antarctic marine systems, such prokaryotic parameters can be used to evaluate environment status.

Relazione dell'attività svolta dalla Dott.ssa R. La Ferla del CNR_IAMC_Messina nell'ambito della Short Term Mobility (AMMCNT. CNR prot. N. 0058167 del 02/09/2015) presso L'Università Federale di Rio de Janeiro

During the last century, the global increase in fossil fuels consumption together with the reduced capacity to remove CO2 due to deforestation, have caused a dramatic input of carbon dioxide into the atmosphere. The resulting enhancement of the natural Greenhouse Effect is partially balanced by sequestration of CO2 in the deep oceanic waters. In fact, topical studies have supported the significant role of the oceanic biological pump with respect to atmospheric CO2 build-up. In the marine ecosystem the biological pump controls the export of biogenic carbon from the surface layers down to the deep. In brief, this mechanism transforms in the euphotic zone, through photosynthesis processes, carbon dioxide into organic matter; the latter sinks to the waters below and at the same time is consumed by respiration with the production of metabolic CO2. However, during the formation of dense waters, a significant quantity of organic products is conveyed from the surface within the water mass and remineralized inside it, thereby altering the normal flow of the biological pump. In this study the evolution of carbon dioxide production rates (ETS activity) in a deep convection site of Eastern Mediterranean Sea (the Southern Adriatic Pit) in the period from 1993 to 2014 is reported in relation to climatic change.

La comunità microbica costituisce l'anello di sutura tra componenti biotiche e abiotiche dell'ecosistema marino e contribuisce ai processi di base della pompa biologica del carbonio. Infatti, mediante i suoi comparti etero ed autotrofici, essa è strettamente collegata sia con le catene trofiche. Il link tra ecologia microbica e risorse ittiche nasce dalla consapevolezza che i fattori biofisici (ambientali) e le dinamiche trofodinamiche (interazioni tra specie) - insieme ai processi di sfruttamento delle risorse biologiche (pesca) - sono le principali forzanti che influenzano la produttività ittica. Di conseguenza, una corretta politica di gestione ecocompatibile del patrimonio naturale non può prescindere dal monitoraggio delle condizioni ambientali e delle dinamiche trofiche che regolano la funzionalità degli ecosistemi. Urge inoltre approfondire le conoscenze sulle relazioni tra il cambiamento globale e risorse marine, attraverso lo studio delle relazioni tra le reti trofiche e la biogeochimica negli oceani. La problematica diviene particolarmente importante nelle aree costiere e di transizione che subiscono contemporaneamente l'impatto di pressioni antropiche e naturali. Nel Mar Mediterraneo, diversi documenti hanno sottolineato i rapporti tra i parametri microbici e le condizioni chimico fisiche delle acque, così come tra le masse d'acqua. E' anche noto che tenui cambiamenti nelle variabili ambientali possono drasticamente modificare l'abbondanza, la distribuzione e la disponibilità delle popolazioni ittiche e dei loro prodotti di riproduzione. Inoltre, nelle zone di produzione ittica, i processi di trasferimento del carbonio organico attraverso le catene trofiche microbiche hanno un'importanza fondamentale e nei mari oligotrofici, quale è il Canale di Sicilia, la scarsa funzionalità nei primi livelli trofici si potrebbe tradurre in un disequilibrio ecosistemico con implicazioni sui consumatori secondari e terziari, in termini di produttività e biodiversità. In tale ottica, gli obiettivi di ricerca di SP2-WP1-AZ2-UO05 sono stati quelli di approfondire le conoscenze sui popolamenti microbici in un'area di spawning e di verificare l'esistenza o meno di interrelazioni tra la rete trofica microbica e lo sviluppo di uova e larve di Engraulis encrasicolus - specie ittica pelagica di interesse commerciale. Gli scopi della ricerca sono stati quindi molto articolati ed hanno affrontato tre principali tematiche: 1) lo studio quantitativo delle biomasse (nelle frazioni dimensionali: pico-, nano- e micro-plantoniche); 2) lo studio delle popolazioni produttive e degradative della sostanza organica svolto dalle popolazioni auto- ed eterotrofiche; 3) il flusso biogeochimico del carbonio nell'area di studio. E' stato inoltre valutato - per la prima volta in un'area oligotrofica del Mediterraneo - il contributo dell'attività enzimatica libera (non aggregata a cellule microbiche).

Remineralization in the Northern Adriatic Sea has been examined by studying the respiratory rates, through electron transport system activity, in four systems identified on the basis of different salinities, caused by riverine outflows, and different productivity regimes measured by apparent oxygen utilization. The sea waters influenced by river discharges were characterized by high respiratory activity while in fully marine waters respiration fell close to the typical value for the surface pelagic Mediterranean waters. A speculative approach to quantify the trophic balance in the examined sub-systems was adopted and the following ratios were computed: Primary Production/Respiration (PP/R); Primary Production/(Bacterial Production + Respiration) [PP/(BP + R)]; (Dissolved Organic Carbon + Particulate Organic Carbon)/Respiration [(DOC + POC)/R], using the data generated at the same time from the same multidisciplinary cruises. High variability of these metabolic ratios in the described subsystems occurred, so that shifting autotrophy and heterotrophy patterns through summer-winter and cross-productivity front trends occurred. Episodic heterotrophy has been found to happen in the North Adriatic Sea, although this is normally considered a productive ecosystem.

SUMMARY: A synthesis of published metabolic CO 2 production rates determined in the water column of the Eastern Mediterranean Sea from 1993 to 1999 is reported with the aim of furnishing an overall picture of the remineralization processes occurring in the basin. The trends of the remineralization are also interpreted with respect to the so-called Eastern Mediterranean Transient (EMT) event. This study augments the sparse data set of respiration measurements, from oceanographic surveys, and highlights the tight coupling between biological processes and circulation patterns. In the photic zone, the rates decreased from West to East as well as from North to South. In the aphotic zone, the C remineralization trend followed the traditional routes of intermediate and deep waters in the Eastern Mediterranean Basin, and underwent the important modifications into the depths as a consequence of the EMT impact.

The carbon transfer through the microbial community in two areas of the Northern Adriatic Sea was estimated by proteolytic and respiratory activities during four oceanographic surveys carried out in June, 1996, 1997 and February, 1997, 1998. In front of the Po Delta (area A), the mean rates of proteolytic activity range from 4.9 to 9.9 r µg r C r h r l; near Ancona (area B), they range from 3.1 to 7.6 r µg r C r h r l. Respiratory rates vary between 0.19 and 2.29 and between 0.24 and 1.40 r µg r C r h r l in areas A and B, respectively. In general, high rates occur in the surface layers, within the first 10 r m of depth. In area A, proteolytic and respiratory rates undergo seasonal course, with high activity in warm periods. In area B, respiration and bacterioplankton abundance increase from the first to the second year, whilst proteolytic activity decreases. The sequence of metabolic steps in the carbon transfer within the bacteria, from the biotic vs . the abiotic compartment, was drawn in order to defi...

The EU Marine Strategy Framework Directive 2008/56/EC (MSFD) defines a framework for Community actions in the field of marine environmental policy in order to achieve and/or maintain the Good Environmental Status (GES) of the European seas by 2020. Microbial assemblages (from viruses to microbial-sized metazoa) provide a major contribution to global biodiversity and play a crucial role in the functioning of marine ecosystems, but are largely ignored by the MSFD. Prokaryotes are only seen as "microbial pathogens", without defining their role in GES indicators. However, structural or functional prokaryotic variables (abundance, biodiversity and metabolism) can be easily incorporated into several MSFD Descriptors (i.e. D1. Biodiversity, D4. Food webs, D5. Eutrophication, D8. Contaminants and D9. Contaminants in seafood) with beneficial effects. The present review provides a critical analysis of the current MSFD descriptors and illustrates the reliability and advantages of the potential incorporation of some prokaryotic variables within the set of indicators of marine environmental quality. Following a cost/benefit analysis against scientific and economic criteria, we conclude that marine microbial components, and particularly prokaryotes, are highly effective for detecting the effects of anthropogenic pressures on marine environments and for assessing changes in the environmental health status. We thus recommend the inclusion of these components in future implementations of the MSFD.