Filippo Azzaro

Dynamics of extracellular enzymatic activities in a shallow Mediterranean ecosystem (Tindari ponds, Sicily)

Three microbial extracellular enzymes, leucine aminopeptidase (LAP), β-glucosidase (β-glu) and alkaline phosphatase (AP), were studied in six small Mediterranean littoral ponds, to evaluate the diversity of microbial activities relative to prevailing environmental conditions. The marked diversification of the trophic states, ranging from oligotrophy to eutrophy, in the ponds was reflected in a range of enzyme patterns at different spatial and temporal scales. There were higher levels and greater variability of microbial activity in the oldest and most ‘confined’ ponds (ranges: 0.55–4360.00 nm h−1, 0.15–76.44 nm h−1, 1.29–1600.00 nm h−1 for LAP, β-glu and AP respectively) compared with the youngest and most seaward ponds (ranges: 22.64–612.0 nm h−1, 0.06–48.89 nm h−1, 0.32–744.0 nm h−1 for LAP, β-glu and AP respectively). The close relationship of the degradative potential with chlorophyll-a and particulate organic carbon could be a consequence of the stimulating effect of phytoplankton-released polymeric compounds (organic matter) and/or a response of the microbial community to warm temperatures, which were recorded from July to September. Within an area less than 1 km2, different aquatic ecosystems coexist and maintain their distinctive properties in terms of microbial biogeochemical processes.

Microbial assemblages for environmental quality assessment: Knowledge, gaps and usefulness in the European Marine Strategy Framework Directive

Abstract 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. This 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. Thus, we recommend the inclusion of these components in future implementations of the MSFD.

Assessment of the ecological status of transitional waters in Sicily (Italy): First characterisation and classification according to a multiparametric approach

A 1-year cycle of observations was performed in four Sicilian transitional water systems (Oliveri-Tindari, Cape Peloro, Vendicari and Marsala) to characterise their ecological status. A panel of variables among which trophic and microbial (enzyme activities, abundance of hetetrophic bacteria and of bacterial pollution indicators) parameters, were selected. Particulate organic carbon (POC) and nitrogen (PON) and chlorophyll-a (Chl-a) contents defined the trophic state, while microbial hydrolysis rates and abundance gave insights on microbial community efficiency in organic matter transformation and on allochthonous inputs. To classify the trophic state of examined waters, the synthetic trophic state index (TRIX) was calculated. Microbial hydrolysis rates correlated positively with POC and Chl-a, which increased along the eutrophication gradient. The significant relationships among TRIX, trophic and microbial parameters suggested the use of leucine aminopeptidase, alkaline phosphatase and POC as suitable parameters to implement the Water Framework Directive when assessing the ecological status of transitional water systems.

Prokaryotic activities and abundance in pelagic areas of the Ionian Sea

The Ionian Sea represents a suitable basin for studying the biogeochemical processes mediated by microbial activities. Because of its characteristics as a crossing region between the western and eastern Mediterranean Sea, it is one of the sites most affected by changes in water mass composition and dynamics, caused by the Eastern Mediterranean Transient (EMT). To date, relatively few data exist on microbial activities in pelagic areas of the Ionian Sea. From 1998 to 2004, during different research cruises, prokaryotic parameters (abundance, extracellular enzyme activities leucine aminopeptidase, β-glucosidase, alkaline phosphatase, bacterial production and respiration) were measured together with culturable bacteria and the main physical, chemical and trophic parameters (temperature, salinity, nutrients, particulated organic matter). The aim of the study was to describe the spatial and temporal variability in microbial activities involved in the carbon and phosphorus cycles, in different layers. Results showed that organic matter transformation mediated by the microbial community displayed a significant increase in autumn, highlighting the occurrence of significant changes at meso- and bathypelagic depths. Unlike the dark ocean, bacterial growth efficiency in the Ionian Sea, which increased with depth, seemed to vary from being a source of carbon in the epipelagic layer to a sink in the meso- and bathypelagic layers. The mechanism of phosphatase regulation showed a weak inverse correlation between specific phosphatase and inorganic P in all seasons except autumn. It is worth mentioning that the reported results constitute, to the best of our knowledge, one of the available datasets giving information about microbial activities in the Ionian Sea.

A new generation of coastal monitoring platforms

The need for new instruments and systems for environment monitoring encouraged the development of a network of coastal platforms combining a high versatility with ease of use and affordability. Almost every instrument can be fitted on the platforms, thanks to the large amount of available power provided by both solar panels and wind generators. All the platforms host a pumping system that pumps water from five depths into a measurement chamber where a multiparametric probe is fitted and from where other devices (e.g. samplers or analysers) can draw samples. In situ temperature measurements are provided at the same pumping depths. A colorimetric nutrient analyser and a meteorological station complete the basic equipment. On one of the platforms, a remotely controlled water sampler and an ADCP are also fitted. The data-acquisition and transmission system enables the platform to be controlled remotely using a special macro-commands set. Several examples of use are presented.

Are prokaryotic cell shape and size suitable to ecosystem characterization

Estimation of microbial biomass depends on cell shape and size determinations, and thus, there is a wide biovolume variability among morphotypes. Nevertheless, data on morphology and morphometry of prokaryotic cells under different trophic status are seldom published, due to the methodological difficulties of cell measurements. The main question addressed in this paper concerns the suitability of prokaryotic size and shape for environmental characterization. Microbial biovolumes were compared among different ecosystems, located in temperate and tropical regions. Samples were taken from fresh, brackish, mixohaline, and estuarine waters that were classified as oligo-, meso-, eu-, and hypertrophic by comparing synoptically different trophic indices. Prokaryotic cell abundance and volume were quantified by Image Analysis, used to calculate biomass, and correlated to environmental variables. Some samples were analyzed by flow cytometry also, and data from sub-populations with a different apparent DNA content were available. Prokaryotic abundances generally increased from oligo- to hypertrophic waters while cell volumes increased from oligotrophic to eutrophic waters. Although significant correlations between cell volumes and environmental variables were detected (positive with salinity and negative with Chlorophyll-a), different morphotypes dominated each studied regions. Our results sustain the hypothesis that prokaryotic cell size and shape could be useful to ecosystem characterization.

Microbial Biomass and Respiratory Activity Related to the Ice-Melting Upper Layers in the Ross Sea (Antarctica)

In late austral spring 1994, a study was carried out in the Ross Sea, with sampling in the ice-free, ice-covered and marginal ice zones. Samples were taken along two transverse transects, to determine spatial variations in some microbiological parameters. Some stations were repeatedly sampled to study the temporal development of microbial components. Microbial biomass was measured as fractionated ATP in the following size categories: micro- (250–10µm), nano- (10–2µm) and picoplankton (2–0.2µm); bacterial biomass was estimated on the basis of lipopolisac-charide concentration and microbial respiratory rate was estimated by the Electron Transport System activity of organisms <200 µm.

Microbiological characterization of a semi-enclosed sub-Antarctic environment: the Straits of Magellan

Among sub-Antarctic ecosystems, the microbiology of the Straits of Magellan has been poorly documented due to the scarcity of observations. In this context, the spatial distribution of microbiological parameters, both in terms of abundance (total picoplankton and picophytoplankton, cultivable heterotrophic bacteria) and biochemical assays (adenosine triphosphate and lipolysaccharide estimations, as well as electron transport system activity), was investigated in the epipelagic layer along the Straits during late summer 1991 and early autumn 1995. The microbial dynamics showed significant variations along the Straits, with increasing values generally determined eastward both in 1991 and 1995. Microbiological results were additionally correlated with available data on the physico-chemical and biological properties of the analyzed water masses. Taking into consideration the whole dataset, the principal component analysis led to the identification of three main macro-areas along the Straits of Magellan (Paso Largo, Paso Ancho and Angostura/Isla Isabel) with different trophic features. This held true when the two cruises were individually considered, as well as when comparing each macro-area between the two cruises. Additionally, a first attempt to quantify the carbon flux through the microbial compartment within the main identified macro-areas was made. The present work will allow the gaining of further understanding of the microbiology of this under-investigated sub-Antarctic marine ecosystem.

Biochemical and dynamical characteristics of the Messina Straits water by means of hyperspectral data

The Straits of Messina was surveyed on September the 25th 1999, at 14:15 local time, by means of the 4 spectrometers of Multispectral Infrared Visible Imaging Spectrometer instrument, recording 102 channels from Visible to Thermal Infrared along four southwards oriented flight lines. The first flight line was recorded from an altitudes of 1500 m a.s.1. (nadir pixel size of 3 m), while the others have been acquired from an altitudes of 4000 m a.s.1. (nadir pixel size of 8 m). In the Straits of Messina the strong tidal currents as well as the morphological features determine the upwelling of deep waters to the photic layer. Traditional oceanographic surveys, based on period punctual sampling, are sometimes inadequate to deeply investigate the areas subjected to high variability altering in space and in time the distribution of abiotic and biotic parameters. The effect of tidal currents on the upwelling of the Straits of Messina was measured by using the MIVIS hyperspectral sensor and through the continuous survey of some tracer parameters from sailing vessel. The collected hyperspectral data sets, once calibrated to reflectance (by using atmospheric model and fields spectra collected during the campaign) and geometrically corrected, were used to develop preliminary local bio-optical algorithms derived from in situ (ground and sea) measurements and to obtain suitable mapping of the chlorophyll distribution and of the Sea Surface Temperature of the investigated area.

Late Summer Phytoplankton Blooms in the Changing Polar Environment of the Kongsfjorden (Svalbard, Arctic)

Abstract Kongsfjorden (Spitsbergen, Svalbard) is an inlet treated as a model site for studies on the impact of climate change in the Arctic due to its hydrological features. In this research, seven-days monitoring was carried out to evaluate the effects of hydrological variability on phytoplankton biomass and diversity in the late summer period. Temperature, salinity, nutrients, total suspended matter, phytoplankton abundance and biomass were determined for each sample. The thermo-haline properties of the column water seemed to affect phytoplankton communities. Their abundances and biomass were correlated with the amount of the total suspended matter. Moreover, species composition and biomass dramatically changed throughout the study period. Cold-water and Atlantic species were replaced by temperatewarm water dinoflagellates, including harmful species. An increase in phytoplankton biomass as well as the presence of dinoflagellate aggregations, mainly composed of Prorocentrum cf. gracile, were detected. This kind of algal accumulation is a new phenomenon in the Arctic and was probably related to the mobilization of sediment-rich glacial meltwaters. These findings, even if preliminary, suggest the need to study how additional biomass pulses and the increase of harmful species may alter the food web structure and the biogeochemical cycles, leading to major ecosystem changes.