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The Aquatina Lagoon (Southern Adriatic Sea, Mediterranean Ecoregion) is a transitional water ecosystem with great ecological and socio-economic interest. Anthropogenic activities around the lagoon (e.g., agriculture and tourism) and hydrology can affect the environmental quality and biodiversity of the lagoon. Herein, the dynamics and diversity of phytoplankton communities were studied before and after the opening of a new canal connecting the lagoon with the sea, by using different approaches based on an evaluation of the size and structure of the phytoplankton as well as the taxonomic analyses. The lagoon depicted time-related fluctuations in chemical-physical parameters. The phytoplankton trend was characterized by an increase in abundance and biomass in summer, when pico-sized autotrophs dominated. Generally, nano-sized phytoflagellates dominated the community, while micro-sized dinoflagellates and diatoms were less abundant. An increase in the phytoplankton taxa number was observed throughout the years. All the analyzed parameters were generally relatively homogeneous before the opening of the channel, while some quantitative differences among stations were observed in the second sampling period. Considering the statistical evidence, both environmental and biological parameters were affected by the “dilution” effect exerted by marine water inputs. This research supports the evidence that phytoplankton is a good indicator of the environmental status, and the obtained results contribute to the implementation of management strategies for the conservation of transitional water ecosystems.

Very few studies have investigated marine microbial colonization in polar regions, but climate-changing scenarios stress the importance of these investigations to protect life in such extremely vulnerable ecosystems. In two different coastal sites of the Ross Sea (Road and Tethys Bays, Antarctica) exposed to different stressors, the microbial biofilm colonizing the surface of plastic (polyvinyl chloride, PVC, and polyethylene, PE) panels left submerged in two experiments at different timescales (“short-term”: 3 months, and “long-term”: 9 and 12 months) was studied. The abundance and metabolic enzymatic activities [leucine aminopeptidase (LAP), beta-glucosidase (GLU) and alkaline phosphatase (AP)] of the prokaryotes and the microalgal abundance and species composition were analyzed, in parallel with the main environmental parameters. The prokaryotic community showed higher abundance and metabolic activities on PVC than on PE as opposed to microalgae. A peak in the microfouling prokaryotic abundance and metabolic functions was frequently recorded after 3 months of immersion, corresponding to the late austral summer period. LAP and AP were the most active enzymes, suggesting that microbial metabolic profiles were modulated by labile organic substrates. Our results suggest that the composition and function of microbial biofilm could be considered as sentinels of natural or anthropic-related disturbances.

The HR (High-Resolution) EO (Earth Observation) satellite systems Landsat 8 OLI and Sentinel 2 were tested for mapping the frequent phytoplankton blooms and Chl a distributions in the sea basin of the Mar Piccolo of Taranto (Ionian Sea, southern Italy), using the sea truth calibration data acquired in 2013. The data were atmospherically corrected for accounting of the aerosol load on optically complexes waters (case II). Various blue-green and additional spectral indices ratios, were then satisfyingly tested for mapping the distribution of Chl a and differently sized phytoplankton populations through PLS (Partial Least Square regression) models, regressive statistical models and bio-optical algorithms. The PLS models demonstrated higher robustness for assessing the distribution of all the phytoplankton and Chl a except for those related to sub-surface micro-phytoplankton. The distributions obtained via a bio-optical approach (OC3 algorithm and full physically based inversion) showed a general agreement with the previous ones produced by statistical methods. The reflectance signals, captured by OLI and Sentinel 2 sensors in the visible and shorter wavelengths once atmospherically corrected, were found to be useful to map the coastal variability at detailed scale of Chl a and different phytoplankton populations, in the optically complexes waters of the Mar Piccolo.

Microalgae are photosynthetic unicellular microorganisms that represent an extremely important component of the aquatic ecosystem productivity, diversity, and functioning [...]

The Straits of Messina (Southern Italy, Mediterranean Sea) are a very complex area: they connect two basins (Tyrrhenian and Ionian) with different hydrographic features and is characterised by upwelling and mixing phenomena. The aim of the study was to evaluate if and how the physical and chemical water conditions and hydrodynamics influenced the phytoplankton and bacterial patterns and the functioning of this ecosystem. During a late winter survey, size-fractionated phytoplankton (from 0.2 to 200 μm) biomass (chlorophyll a), cell densities and species composition as well as total picoplankton abundances, morphotype composition, and activity levels of the enzymes leucine aminopeptidase, β-glucosidase, and alkaline phosphatase were investigated. The obtained results showed a marked diversification among the water masses identified within the Straits area. The analyses of the phytoplankton diversity indices, particularly those based on phylogenetic relationships between species (indices of taxonomic diversity and distinctness), confirmed our findings. In conclusion, the patterns of phytoplankton and bacterial communities provide a suitable approach to evaluate how microbial communities respond to changing environmental scenarios. This tool could be applied to other temperate Mediterranean ecosystems.

A simulation of phytoplankton dynamics in the coastal shellfish farming site of Mar Piccolo in Taranto (Ionian, Mediterranean Sea) is here reported. This simulation is an element of a greater ecological model produced taking into account the System Approach Framework. The model represents a refinement of a previous phytoplankton tool aimed to better understand the complex mosaic of the ecosystem functioning by providing additional information to support mussel farming. In particular, throughout the years the increase of water temperature and intensive musselculture caused a phytoplankton size and biomass reduction. Results of our simulation evidenced that the phytoplankton tool reproduced the size-fractions (micro-, nano- and picophytoplankton) biomass growth and the mussel (Mytilus galloprovincialis) grazing with a good level of performance. This newly calibrated phytoplankton model aims to provide new insights on modelling scenarios for the sustainable production of mussels.

Harmful algal blooms (HABs) are extreme biological events representing a major issue in marine, brackish, and freshwater systems worldwide. Their proliferation is certainly a problem from both ecological and socioeconomic contexts, as harmful algae can affect human health and activities, the marine ecosystem functioning, and the economy of coastal areas. Once HABs establish, valuable and environmentally friendly control actions are needed to reduce their negative impacts. In this study, the influence exerted by the filter-feeding activity of the two sabellid polychaetes Branchiomma luctuosum (Grube) and Sabella spallanzanii (Gmelin) on a harmful dinoflagellate was investigated. Clearance rates (C) and retention efficiencies were estimated by employing the microalga Amphidinium carterae Hulburt. The Cmax was 1.15 ± 0.204 L h−1 g−1 DW for B. luctuosum and 0.936 ± 0.151 L h−1 g−1 DW for S. spallanzanii. The retention efficiency was 72% for B. luctuosum and 68% for S. spallanzanii. Maximum retention was recorded after 30 min for both species. The obtained results contribute to the knowledge of the two polychaetes’ filtration activity and to characterize the filtration process on harmful microalgae in light of the protection of water resources and human health. Both species, indeed, were extremely efficient in removing A. carterae from seawater, thus suggesting their employment as a new tool in mitigation technologies for the control of harmful algae in marine environments, as well as in the aquaculture facilities where HABs are one of the most critical threats.

Coccoid cyanobacteria produce a great variety of secondary metabolites, which may have useful properties, such as antibacterial, antiviral, anticoagulant or anticancer activities. These cyanobacterial metabolites have high ecological significance, and they could be considered responsible for the widespread occurrence of these microorganisms. Considering the great benefit derived from the identification of competent cyanobacteria for the extraction of bioactive compounds, two strains of picocyanobacteria (coccoid cyanobacteria < 3 µm) (Cyanobium sp. ITAC108 and Synechococcus sp. ITAC107) isolated from the Mediterranean sponge Petrosia ficiformis were analyzed. The biological effects of organic and aqueous extracts from these picocyanobacteria toward the nauplii of Artemia salina, sea urchin embryos and human cancer lines (HeLa cells) were evaluated. Methanolic and aqueous extracts from the two strains strongly inhibited larval development; on the contrary, in ethyl acetate and hexane extracts, the percentage of anomalous embryos was low. Moreover, all the extracts of the two strains inhibited HeLa cell proliferation, but methanol extracts exerted the highest activity. Gas chromatography–mass spectrometry analysis evidenced for the first time the presence of β-N-methylamino-l-alanine and microcystin in these picocyanobacteria. The strong cytotoxic activity observed for aqueous and methanolic extracts of these two cyanobacteria laid the foundation for the production of bioactive compounds of pharmacological interest.

Coastal marine ecosystems host complex microbial communities whose composition and metabolism are influenced by continental inputs and mesoscale properties of seawater masses. The identifying traits of the phytoplankton and bacteria such as biomass, size, shape and their metabolism related to organic matter production and degradation, recognized as indicators of the functioning of an ecosystem, were observed in the Gulf of Manfredonia (South Adriatic Sea, Italy) in late spring. This Gulf area is characterized by terrestrial inputs and mesoscale circulation influence such as coastal waters flowing southward from the North Adriatic and offshore waters interested by the Ionian Sea. Water samples were grouped in clusters (Coastal, Intermediate, Offshore and Deep Systems) according to the water column properties. Phytoplankton community biomass and composition, autotrophic and total prokaryotic abundances and microbial metabolism such as enzyme activity rates and prokaryotic heterotrophic production were analyzed to elucidate the trophic pathways with the objective to infer on the ecosystem status. As expected, size-fractionated phytoplankton biomass and production showed greater concentration in coastal waters with prevalence of the largest fractions (micro- and nano-) supported by the diatoms. Conversely, lower biomass and production were measured in all off-shore waters, mainly sustained by smallest fractions (nano-sized phytoflagellates and picophytoplankton). Total and autotrophic prokaryotic abundance decreased from coastal to offshore stations, inversely with respect to cell volume. Prokaryotic heterotrophic production was just below 50% compared to that of phytoplankton in all waters, evidencing an active biomass synthesis. High alkaline phosphatase and leucine aminopeptidase in coastal and offshore waters suggested the quick regeneration of Phosphorus and protein decomposition, respectively. Different levels of phytoplankton-bacteria association might provide a tool to define the ecological status of the studied system in the observed period; an approach to ecosystem assessment exportable to other coastal systems is proposed.

Marine cyanobacteria are a source of bioactive natural compounds, with a wide range of biotechnological applications. However, information on sponge-associated cyanobacteria are relatively scarce to date. In this paper, we carried out the morphological and molecular characterization of eight cyanobacterial strains, previously isolated from the Mediterranean sponge Petrosia ficiformis, and evaluated their biological activities on epithelial- and neuron-like cultured cells of human and murine origin. The new analysis allowed maintaining the assignment of three strains (Cyanobium sp., Leptolyngbya ectocarpi, and Synechococcus sp.), while two strains previously identified as Synechococcus sp. and Leptolyngbya sp. were assigned to Pseudanabaena spp. One strain, i.e., ITAC104, and the ITAC101 strain corresponding to Halomicronema metazoicum, shared extremely high sequence identity, practically representing two clones of the same species. Finally, for only one strain, i.e., ITAC105, assignment to a specific genus was not possible. Concerning bioactivity analyses, incubation of cyanobacterial aqueous cell supernatants induced variable responses in cultured cells, depending on cell type, with some of them showing toxic activity on human epithelial-like cells and no toxic effects on human and rat neuron-like cells. Future investigations will allow to better define the bioactive properties of these cyanobacteria strains and to understand if they can be useful for (a) therapeutic purpose(s).

In recent years seaweeds have increasingly attracted interest in the search for new drugs and have been shown to be a primary source of bioactive natural compounds and biomaterials. In the present investigation, the biochemical composition of the red seaweed Gracilaria gracilis, collected seasonally in the Lesina Lagoon (Southern Adriatic Sea, Lesina, Italy), was assayed by means of advanced analytical techniques, such as gas-chromatography coupled with mass spectrometry and spectrophotometric tests. In particular, analysis of lipids, fatty acids, sterols, proteins, phycobiliproteins and carbohydrates as well as phenolic content, antioxidant and radical scavenging activity were performed. In winter extracts of G. gracilis, a high content of R-phycoerythrin together with other valuable products such as arachidonic acid (PUFA ω-6), proteins and carbohydrates was observed. High antioxidant and radical scavenging activities were also detected in summer extracts of the seaweed together with a high content of total phenols. In conclusion, this study points out the possibility of using Gracilaria gracilis as a multi products source for biotechnological, nutraceutical and pharmaceutical applications even although more investigations are required for separating, purifying and characterizing these bioactive compounds.

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.

Prokaryotic and phytoplankton interaction plays a key role in relevant processes such as carbon fluxes and nutrient regeneration (Zaccone et al., 2004). Sinking biogenic particles drive respiration in the ocean and related studies are important to determine the flow of organic matter along the water column (Martin et al., 1987; Karl et al., 1987). However, organic matter collected by sediment traps (Langone et al., 2000) or the studies of the disequilibrium 234Th/238U (Aliani et al., 2004) 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 (Azzaro et al., 2006). 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 prokaryotic and phytoplanktonic biomass and of microbial remineralization rates 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. The Kongsfjorden was affected by inflow of Atlantic water as well as glacier melt water runoff (Cottier et al., 2005). The experiment comprised 5 samplings performed during a 7 day period in MDI station. For each sampling, photosynthetically active radiation (PAR), temperature and conductivity (salinity) were recorded along the water column with a PNF-300 profiler and a SeaBird Electronics SBE-911 plus profiler, respectively . Water samples were taken at five different depths (surface, 5, 25, 50 and 100 m) to determine nutrients, particulate organic carbon, prokaryotes and phytoplankton biomass, and community respiration. In addition, prokaryotes sunk with the particulate matter were studied into the sediment trap positioned in the MDI during the period between June and September 2013. The latter assessment allowed us to determine the flow of prokaryotes, conveyed from organic matter sinking, throughout the summer. Due to melting of the glaciers in the surface water of the study site, there were sediment loads which strongly limited light penetration and low irradiance (~0.7% E0+) at 5 meters below the surface. Along the water column the intrusion of the salty and warm Atlantic water was visible in the study site and the warm core was at about 25 m depth. PO4 concentrations ranged between 0.43 (surface) and 1 µM (100 m) and in general the values increased from surface to bottom. NH4, NO2 and NO3 significantly changed along the vertical and with time and varied between 0.39 and 5.05µM, 0.01 and 0.67µM, 0.001 and 4.18µM, respectively. Prokaryotic abundances and cell volumes ranged between 5.6 and 15.9 E+05 cells ml-1 and 0.033 and 0.093 µm3, respectively. These latter parameters showed a peak at 25 m depth in the core of incoming Atlantic water. This evidence was not determined in chlorophyll a (range 0.034-1.102 mg m-3), where the highest values were determined at the surface and 5 m depth. Speculations will be made on the variability of the fluxes of carbon remineralization in the short time scale and the different role played by autotrophic and heterotrophic communities along the water column.

Attempts to merge marine food webs and marine biogeochemical research have recently been developed in response to the need to understand how global change will impact marine ecosystems and resources (Salihoglu et al., 2013; Painting, et al., 2013). Among the multiple drivers that influence ecosystem dynamics, Link et al. (2012) focused on three main processes that affect marine fish productivity: biophysical (environmental), exploitative (fisheries), and trophodynamic (species interactions) factors. Previous paper underlined the relationships among microbial parameters and physical and chemical conditions of waters (Zaccone et al., 2012). With the aim of providing an ecosystem approach to fisheries management, the monitoring of biological and environmental variables was carried out in the frame of the Bansic12 cruise performed in the Sicily Channel (Ibleo-Maltese platform) during July 2012. The Sicily Channel is a spawning area of Engraulis encrasicolus (Linnaeus, 1758), a pelagic species of commercial interest (Basilone et al., 2013). As a consequence, fish eggs and larvae together with microbial assemblages (virio-, autotrophic and heterotrophic pico-, nano- and microplankton) were quantified in terms of abundance and biomass (Andrade et al., 2003; Caroppo et al., 2010; Fonda Umani et al., 2010; La Ferla et al., 2012). To give a more comprehensive picture of microbial role in supporting the flux of biogeochemical elements in the study area, rates of microbial metabolic processes (primary and secondary production, enzymatic hydrolysis of dissolved and particulate matter, and community respiration) were also quantified (La Ferla et al., 2005; La Ferla et al., 2010; Caruso et al., 2014). In addition, the hydrology, the trophic parameters and correlated indices were analyzed to contribute to the understanding of plankton communities dynamism (Leonardi et al., 2009). The euphotic layer was characterized by the presence of the typically oligotrophic MAW (Modified Atlantic Water), flowing eastward along the Sicilian coast. Low nutrient concentrations were recorded, particularly regarding the phosphorus, whose values were close to the detection limit. The diffuse oligotrophy of the area was confirmed by high N/P ratios as well as by low Chl-a values. Particulate Organic Carbon (POC) concentrations were low, as well as those of Particulate Nitrogen (PN). Peaks of POC and PN were recorded at the Deep Chlorophyll Maximum (DCM) or below the thermocline (Leonardi et al., 2014). As regards biological parameters, virus counts were low with a mean value of 1.68E+05 ± 7.0E+04 VPL ml-1 and prokaryotic biomass ranged between 24.9 and 113.0 µg C L-1, mainly composed by curved rods and coccobacilli (range size: 0.160 – 0.459 µm3). Low nucleic acid cells (LNA) prevails over high nucleic acid cells (HNA) with a HNA/LNA mean ratio of 0.56, similar to that occurring in surface layer of several pelagic Mediterranean areas (La Ferla et al., 2012). The picophytoplanktonic biomass (range 0.29–26 µg C L-1), was mostly due to the presence of coccoid cyanobacteria, belonging to the genus Synechococcus. Total nanoplankton biomass (range 0.11-1.71 µg C L-1) showed the highest values at the DCM or below the thermocline. Nanoplankton was represented, among the others, by the dinoflagellates Amphidinium carterae and Heterocapsa niei. The coccolithophorid Emiliania huxleyi and flagellates of uncertain taxonomic identification were also abundant. Microphytoplankton abundance ranged between 6.1 and 40.5 E+03 cells L-1, while biomass between 0.28 and 2.43 µg C L-1. Diatoms and dinoflagellates were the main components of the community, composed by 24 and 30 species, respectively. Concerning microzooplankton, eggs, nauplia and metazoan larval stages prevailed in terms of biomass in almost all samples. Heterotrophic dinoflagellates were the second more relevant group while aloricate Ciliates and Tintinnids did not significantly contribute to the total biomass. Biomass maxima were generally observed at the surface or at the DCM, but never exceeded 16.0 µg C L-1. Finally, anchovy eggs and larvae mainly occurred in the 0-10/0-25 m depth intervals, with highest densities of 4.2 eggs m-3 and 2.6 larvae m-3. The rates of production, hydrolysis and degradation activities were quite low, in agreement with the general oligotrophy of the area and in agreement with this findings, picophytoplankton contribution to total production amounted to over than 65%. In terms of metabolic activities, different spatial distributions were observed between the autotrophic and heterotrophic components. In particular, heterotrophic metabolism showed high values in the layer located below the thermocline and above the DCM. Concerning the enzymatic activities, total leucine aminopeptidase activity showed the highest rates, followed by alkaline phosphatase and beta-Glucosidase (Caruso et al., 2014). Distribution of the dissolved enzymatic activities acting on proteins varied widely along the column, accounting for 5 to 90% of the total enzymatic activity and always prevailed on dissolved b-GLU. Total enzymatic activity rates were comparable to those obtained in the oligotrophic zones of Ionian and Mediterranean Sea (Zaccone et al., 2012), while the analysis of the dissolved fraction was the first report for the Mediterranean. In conclusion, the multidisciplinary scientific approach used in this study depicted a complex picture of the study area evidencing a high heterogeneity and dynamism of plankton communities, probably associated to peculiar hydrology of this ecosystem. On the whole, the study area appeared to be characterized by a relatively efficient microbial food web. However, low trophic conditions were stressed by all the biological and biochemical patterns, suggesting an important role of heterotrophic processes in this area in the examined summer period. Consequently, how and how much the microbial web sustains fish reproduction and larval survival need a more comprehensive analysis and will be focused in further research.

Mar Piccolo of Taranto is an estuarine basin heavily exploited for commercial mussel (Mytilus galloprovincialis L.) farming. The historical renown of the Taranto mussels has suffered over the last decade following policy decisions to expand the mussel farms and to relocate a portion of the urban sewage to an outfall outside of Mar Piccolo. The resulting decline in mussel quality and the quandary of how to restore stability to Taranto mussel production became the focal issue for our application of the systems approach framework (SAF). We simulated the ecological, economic, and social interactions that affect mussel production. Stakeholders and mussel farmers contributed by participating in meetings during the entire exercise. Our simulation analysis provided them with a means for understanding the effects of policy scenarios on the system. We present three aspects from our initial results that demonstrate the value of the SAF, as: (1) an operational model to monitor and better research the status of the ecosystem, (2) a management tool to evaluate sustainable mussel farming strategies, and (3) an opportunity for improved communication with and engagement of stakeholders, policy, and the public. The application has also raised important questions about how the food chain is controlled, what could be changed to stabilize the ecosystem to a higher level of productivity, and what role the public and policy could play in promoting sustainable development.