Mariapaola Moreno

Benthic ecology of Vibrio spp. and pathogenic Vibrio species in a coastal Mediterranean environment (La Spezia Gulf, Italy)

We carried out a 16-month in situ study to investigate the ecology of Vibrio spp. and pathogenic Vibrio species in coastal sediments of the Mediterranean Sea, employing multiple-regression analysis to reveal the major environmental factors controlling their occurrence in the benthic environment. In addition, association between vibrios and sediment-inhabiting meiofauna, which is a major component of benthic ecosystems, was investigated. Culturable and total Vibrio spp. estimates by most-probable-number technique coupled with standard polymerase chain reaction (PCR) and real-time PCR methods, respectively, were at least one order of magnitude higher in sediment than in seawater. In addition, potential human pathogenic species Vibrio cholerae, Vibrio vulnificus and Vibrio parahaemolyticus occurred in the sediment with V. parahaemolyticus being the most frequently found. In the pelagic environment, 60% of total variance in culturable Vibrio data was explained by sea surface temperature (40%), salinity (13%) and organic matter concentration (7%). In the benthic environment, sea surface temperature was the only factor that significantly affected culturable Vibrio occurrence although it explained only 25% of total variance, suggesting that additional unexplored factors may play a role as well. No correlation was found between culturable Vibrio spp. concentrations and the abundance of harpacticoid copepods in the sediment whilst a negative correlation was found between Vibrio spp. and nematode abundance which accounted for almost 90% of the total meiofaunal density. Taxonomic analysis revealed that selective bacterial feeders accounted for nearly 50% of the total nematode community and included genera such as Terschellingia, Molgolaimus and Halalaimus, suggesting that top-down control by nematode grazing may be an important factor affecting Vibrio occurrence in these sediments. It is concluded that the benthic marine environment may function as a reservoir of Vibrio spp. and potential pathogenic vibrios whose ecological features appeared substantially different from the ones recognised in the pelagic environment.

The Ligurian Sea: present status, problems and perspectives

The Ligurian Sea is a deep basin in the northernmost sector of the western Mediterranean which shows peculiar hydrodynamic and meteo-oceanographic features. The coasts of the Ligurian Sea are among the most urbanised and industrialised along the Italian coastline: the main causes of disturbance being littoral urban development and harbour activities, the building of littoral rail- and highways, and the presence of several polluted discharges. This review, by evaluating the huge scientific output published in the last three decades, describes and discusses the most important geological, hydrological and biological characteristics of the Ligurian Sea. We show that this regional sea has largely been investigated in terms of its geological and structural evolution, as well as in terms of the sedimentation dynamics of the littoral and deep bottoms, with particular attention to the sedimentation balance of the beaches and their erosive processes. We report that the prevalent hydrodynamic and meteo-oceanographic conditions favour a continuous exchange of coastal water masses, and that the seasonal and interannual dynamics of water masses can effects the local climate, with direct and indirect consequences on fish and benthic communities documented in the last decade. We stress that although recent studies offer good knowledge of the distribution of coastal benthic communities, only scant information is available for the whole continental shelf, the submarine canyons and the rocky bathyal bottoms. Our meta-analysis reveals that significant fishing activities are monitored, but also that certain sectors of the biological resource are suffering, and suggests the set up of appropriate management measures. The Ligurian Sea hosts a number of Marine Protected Areas (MPAs) of high relevance, while the institution of the Whale Sanctuary completes the protection policy of the Regione Liguria. Our meta-analysis points out the need for long-term studies, based primarily on the analysis of those areas of the Ligurian Sea that have been little investigated to date. Finally, only properly addressed studies, using experimental approaches and along appropriate spatial and temporal scales, might allow us to understand the functioning of the Ligurian marine ecosystems, evaluate their health conditions and the dynamics of the main variables that affect the distribution of the single species (including species of high economic value) and benthic communities.

Nematode response to metal, PAHs and organic enrichment in tourist marinas of the mediterranean sea

The structure of nematode assemblages was investigated in the sediments of two different tourist marinas in the Mediterranean Sea and related to pollution variables. Nematode densities and generic compositions were determined, as were concentrations of heavy metals, PAHs and organic matter. Results showed different assemblages at the two marinas, with a dominance of the genera Paralongicyatholaimus and Daptonema. Significant correlations between nematodes and concentrations of environmental contaminants were found. In particular, Paralongicyatholaimus showed a significant negative correlation with Cu concentrations and was almost absent at the stations where higher Cu concentrations were found. The presence of sensitive/tolerant nematode genera represents a promising tool to identify areas subjected to a higher level of disturbance and to define the correct environmental management strategy for harbors.

Sediment organic matter and meiofauna community response to long-term fish-farm impact in the Ligurian Sea (Western Mediterranean)

Quantitative and qualitative changes in meiofauna community structure were investigated to assess the impact of a fish farm, which was operating continuously for 15 years (La Spezia Gulf, W Mediterranean). Sediment samples were collected in June, July, September, October 2000 and February 2001 for the analysis of phytopigments (chlorophyll-a and phaeopigments), the biochemical composition of organic matter (proteins, carbohydrates and lipids) and related to meiofaunal parameters. Sediment organic matter reached extremely high concentrations beneath the fish cages when compared to the control. Particularly lipids, carbohydrates and chlorophyll-a were significantly higher in fish-farm sediments. On a long-term basis meiofauna displayed adaptations in sediments beneath the cages resulting in an increase of density. Organic impact on meiofaunal community structure was evident in terms of an increase of the nematodes to copepods (Ne/Co) and nauplius to copepods (Na/Co) ratios in fish farm sediments. Cumaceans and kinorhynchs were encountered in control sediments, but disappeared in fish-farm samples. These data suggest that meiofauna is a sensitive tool for evaluating the effects of organic enrichment in fish farm impacted areas.

Sedimentary organic matter and bacterial community in microtidal mixed beaches of the Ligurian Sea (NW Mediterranean)

The quantity and quality of organic matter, and bacterial density and frequency of dividing cells were investigated in six microtidal mixed beaches of the Ligurian Sea (NW Mediterranean) to evaluate their main trophodynamic features. Concentrations of biopolymeric carbon (average 88.5 ± 89.0 µgC/g) and the protein:carbohydrate ratio (on average lower than 1) were very low and classified these beaches as highly oligotrophic. The study of biochemical composition highlighted the nature of organic matter as being mainly refractory; furthermore, the quantitative differences observed along the across-beach gradient together with the unchanged pattern in qualitative features suggest that the organic matter in Ligurian beaches is prevalently of marine origin. This implies a negligible contribution of allochtonous and anthropogenic terrestrial input or in situ autochthonous production. Bacterial density displayed values ranging from 0.1–9.0 cell × 108/g DW in the top 2 cm layer and showed a significant correlation with the quantity of organic matter. In addition, the frequency of dividing cells showed a positive correlation with the protein:carbohydrate ratio, suggesting that the biochemical composition of organic matter also has an influence on the active bacterial fraction. Because of the exposed nature, a strong coupling was found between the beach and the marine systems, and this seems to be of fundamental importance in terms of material and energy supply for the beach ecosystem. A shortage within this linkage was observed in summer owing to the strong environmental constrains leading to a sort of “beach desertification” and to a marked oligotrophy. Summer also has an effect of smoothing for spatial variability occurring within the biochemical and microbiological variables among the different beaches. The linkage observed between the sea and the land is the main factor controlling the origin and nature of sediment organic matter in these beaches also regulating bacterial abundances and the frequency of dividing cells.

Interrelationships of bacteria, meiofauna and macrofauna in a Mediterranean sedimentary beach (Maremma Park, NW Italy)

Collelungo beach (Maremma Park, NW Italy), was sampled quantitatively for macrofauna, meiofauna and bacteria in May 2003; several physicochemical variables and variables associated with food availability and sediment structure were also measured. Replicated samples were collected from three sites representing natural conditions, an erosion regime, and the influence of the Ombrone River, respectively, as well as from four stations each located in the surf and sublittoral zones. Both uni- and multivariate techniques were used to assess the benthic community structure and the associated environmental variables. Different diversity indices revealed no pattern; in contrast, multivariate techniques applied on the macrobenthic fauna and the polychaete taxocommunity distinguished between the sites located in natural and eroding conditions from the one located nearby the discharges of the Ombrone river. Τhe community patterns deriving from meio- and macrofauna are clearly divergent. The overall benthic faunal community appears to be influenced by both groups of organisms. The patterns of the meio- and macrofaunal communities seem to be affected synergistically by a number of environmental variables, in accordance with the multicausal environmental severity hypothesis. Meiofaunal patterns are more often correlated with bacteria and the protein concentration than are macrofaunal patterns, indicating a potential utilization of bacteria as a food source by the meiofaunal organisms. Total bacterial numbers are associated with the macrofaunal pattern under the erosion regime, probably as a consequence of competition for food between macrofauna and meiofauna.

Influence of large-spectrum environmental contamination on the micro–meiobenthic assemblages in harbour sediments of the ligurian sea (W Mediterranean)

The concentration of a large spectrum of environmental contaminants (PCBs, PAHs, pesticides and metals) was assessed in surface sediments of two Ligurian harbours (Sanremo and Alassio, NW Mediterranean Sea, Italy) and their relative impact on micro–meiobenthic assemblages was analysed. Concentration, distribution and relative importance of the different contaminants varied considerably between harbours in relation to the different anthropic activities and contamination sources. Results from Principal Component Analysis indicated that high levels of contaminants were typically correlated with low micro–meiobenthic abundance in the sediment. Heavy metals and the organic enrichment were the main factors affecting the distribution and abundance of the bacterial and meiofaunal assemblages in Alassio harbour, whereas hydrocarbons and pesticides played a major role in Sanremo sediments. Neither the bacteria density nor the meiofauna abundance were dependent on sediment grain size, suggesting that micro–meiobenthic parameters may be under the influence of other variables. Our results suggest that high concentrations of contaminants independently from their source or typology are responsible for the impact observed on micro–meiobenthic assemblages in these harbours.

Molecular ecology of marine sediments: determination of Real-Time PCR efficiency for quantifying microbial cells

Polymerase chain reaction (PCR) efficiency is the rate at which a PCR amplicon is generated. More efficient amplification of the DNA fragment (amplicon) will generate more products in fewer cycles, thus improving accuracy and sensitivity of quantitative PCR. The efficiency of Real-Time PCR to detect and quantify microbial cells was compared in marine sediment samples of different origin and chemical composition, and in standard samples. Real-Time PCR efficiencies of marine sediment samples ranged from 1.48±0.1 to 1.83±0.1 and were significantly different from those of standard samples, most probably due to different concentrations of PCR inhibitors. The Real-Time PCR efficiency was higher using species-specific primers (>1.7), and lower using universal primers (<1.7). Generally, when the PCR efficiency was higher, its detection limit was lower. In addition, the sensitivity of the Real-Time capillary assay over the traditional assay was generally greater. We suggest that for quantifying microbial cells in marine sediment samples using Real-Time PCR, standard curves should be constructed for both the standard and sediment samples, and a correction factor should be applied. For qualitative PCR a real-time capillary assay should be used for the detection of small quantities of DNA.

Swash zone interstitial water is a reservoir of fungal micro-organisms on a Mediterranean beach (Genoa City, Italy)

The swash zone interstitial water (SZIW) which occupies interstices, or spaces between the sand grains at the shoreline is suspected of accumulating microbes and thus of posing a health risk for beach users. In this study we examined the presence and concentrations of filamentous fungi and yeasts in SZIW and compared the results to the fungal densities found in the beach sand at three sampling locations along a Mediterranean beach (Sturla Beach, Genoa City, Italy). Unexpectedly SZIW had the highest counts of total filamentous fungi and yeasts while sand samples always displayed lower counts. SZIW also harboured a high fungal diversity with 10 genera and 74 different strains isolated from this matrix while only 8 genera and 47 different strains were isolated from the beach sand samples. Overall data from this study suggest that SZIW may constitute an important reservoir of fungal microorganisms in the beach environment.