Southern Adriatic Research Articles

Eastward spreading of the invasive Rugulopteryx okamurae (Heterokontophyta, Dictyotales) in the Mediterranean: first record in the Adriatic Sea

The brown seaweed Rugulopteryx okamurae is currently included in the list of invasive alien species of European Union concern due to its rapid expansion that is causing both ecological and economic impacts. In this study, we report the first record of R. okamurae in the Southern Adriatic Sea, off the coast of Bari, Italy, currently representing the easternmost limit of its distribution in the Mediterranean Sea. Morphological observations combined with rbcL and psbA sequence analyses confirmed the taxonomic identification. Field surveys carried out between April 2023 and January 2024 highlighted the conspicuous occurrence of R. okamurae over a total surface of approximately 6.5 ha. Two main human-mediated pathways occurring near the sites of the first observation of the alien species may have been responsible for its introduction: the trade in living organisms for human consumption and maritime transport related to the proximity of the port of Bari to the invaded area. Future studies will aim to identify and implement practical, cost-effective management strategies to mitigate this alarming bioinvasion.

Kilometer‐Scale Assessment of the Adriatic Dense Water Multi‐Decadal Dynamics

AbstractThe North Adriatic Dense Water (NAddW)—the densest Mediterranean water generated by extreme cooling during wintertime hurricane‐strength winds—drives the thermohaline circulation, ventilates the deep layers, and changes the biogeochemical properties of the Adriatic Sea. However, modeling the dynamical properties of such dense water at the climate scale has been a challenge for decades due to the complex coastal geomorphology of the Adriatic basin not properly reproduced by existing climate models. To overcome these deficiencies, a 31‐year‐long simulation (1987–2017) of the Adriatic Sea and Coast (AdriSC) kilometer‐scale atmosphere‐ocean model is used to analyze the main NAddW dynamical phases (i.e., generation, spreading and accumulation). The study highlights four key results. First, during winter, the NAddW densities are higher in the shallow northern Adriatic shelf than in the deeper Kvarner Bay—where 25%–35% of the overall NAddW are found to be generated—due to a median bottom temperature difference of 2°C between the two generation sites. Second, the NAddW mass transported across most of the Adriatic peaks between February and May, except along the western side of the Otranto Strait. Third, for the accumulation sites, the bottom layer of the Kvarner Bay is found to be renewed annually while the renewal occurs every 1–3 years in the Jabuka Pit and every 5–10 years in the deep Southern Adriatic Pit. Fourth, the NAddW cascading and accumulation is more pronounced during basin‐wide high‐salinity conditions driven by circulation changes in the northern Ionian Sea.

Evaluation of the Adriatic Sea pollution using mesozooplankton as an environmental indicator

The Adriatic Sea is an enclosed basin threatened by marine pollution due to its hydrographic features and anthropogenic pressure. Although zooplankton has been worldwide regarded as an immediate warning signal of contamination, limited information is available on the contamination of these organisms at the Adriatic level. Hence, this study provides comprehensive data on the presence and levels of multiple pollutants in zooplankton collected from 46 locations. With regards to legacy contaminants, both PCB and DDT levels have declined since the 1980s. Specifically, most samples were characterized by low DDT contamination (average of 3 ± 2.7 ng g− 1 dry weight) and only few of these accumulated levels of concern for what concerns PCB, pointing out possible hotspots of contamination in the central-eastern Adriatic Sea. As regards metal(loid)s, the Metal Pollution Index identified areas of concern in the north Adriatic Sea (Gulf of Venice) with high levels of Co, Cu, Hg, Cr and Pb; in the Central Adriatic Sea (Tremiti islands) with high levels of Co, Ni, Hg, Cr and Pb; in the Southern Adriatic Sea (Taranto and offshore Corfu), with high levels of most metal(loid)s, especially Cr, Ni and Zn. Certain metal(loid)s (e.g. Cd, Pb and Hg) have declined over time and most of them are lower than well-known contaminated worldwide marine ecosystems. Only Cu appears to be particularly high in the Mediterranean zooplankton. Overall, this work suggests a general improvement of the status of contamination of the Adriatic Sea.

Impact of coseismic uplifting on relative sea level change in the Southern Adriatic during the past 4.500 years – New evidence from Dubrovnik epicentral area based on analysis of algal rims and tidal notches

The Southern Adriatic is recognized as one of the most seismically active regions of the Central Mediterranean. It hosted the strongest historically known and instrumentally recorded earthquakes in Croatia and Montenegro. We conducted a detailed study of algal rims and tidal notches along the Dubrovnik–Konavle coastal area, aimed to contribute in reconstruction of relative sea level (RSL) change, palaeoearthquakes and neotectonics during the last 4500 years. The RSL reconstruction based on high-resolution geochronology showed that the spatial variability of RSL change is largely controlled by local tectonics, leading generally to an alternation of periods of RSL rise and rapid falls caused by coseismic uplift events. During the interseismic periods RSL rose at rates from 1.03 to 0.7 mm/yr before AD, followed by a slowdown to ~0.43 mm/yr, and reaching ~1.3 mm/yr after 1850s. The only exception relates to a period of slow RSL drop probably related to the 3.2 ka cold event. Rapid RSL falls caused by coseismic uplift indicate the occurrence of several large-scale events during the 4th–6th centuries AD, the 800–1360 cal AD period, and in 1395, with hints of earlier events between 1395 cal BC and 565 cal AD. These instances correspond to either unknown or insufficiently documented earthquakes. Conversely, the earthquakes in 1520 and 1667 have been clearly identified. The most compelling evidence of coseismic uplift is associated with the 1667 Dubrovnik earthquake, with an estimated uplift of 40–60 ± 15 cm documented along 40 km of coastline. Analyses of multiple sites with the same high-resolution marker show that Holocene tectonic deformations vary along different fault segments with minimum uplift rates ranging from ~0.3 to ~0.9 mm/yr over ~1.5 ka. The main seismogenic source responsible for coseismic uplifts is attributed to the Dalmatian unit basal thrust and its NE-dipping splays at the Adria-Dinarides boundary.

Coastal Eukaryotic Plankton Diversity of the Southern Adriatic as Revealed by Metabarcoding

Plankton studies serve as a basis for marine ecosystem research, but knowledge of marine plankton is still incomplete due to its extreme taxonomic and functional complexity. The application of metabarcoding is very valuable for the characterisation of the plankton community. The plankton community of the Southern Adriatic is subject to strong environmental fluctuations and changes, which underlines the need for frequent, reliable and comprehensive characterisation of the plankton. The aim of this study was to determine the taxonomic composition and seasonal distribution of eukaryotic plankton in the Southern Adriatic. Plankton samples were collected monthly for one year at the coastal station of the Southern Adriatic and metabarcoding was used for taxonomic identification. The results showed a high taxonomic diversity and dynamic seasonal distribution patterns for both the protist and metazoan plankton communities. Metabarcoding revealed both the core, year-round plankton community and previously unrecorded plankton organisms in the Southern Adriatic. The results provide for the first time a comprehensive overview of the plankton community in this area by metabarcoding. The identified seasonal patterns of plankton genera and species in the Southern Adriatic will contribute to the understanding of plankton interactions and future changes in community diversity characterisation.

The freshwater discharge into the Adriatic Sea revisited

The present study reconstructs the river discharge climatology and its respective historical series for all rivers of the Adriatic Sea with averaged climatological daily river discharge above 1 m3s−1, to reach a better representation of the Adriatic rivers in hydrodynamic models and, consequently, to develop a more realistic freshwater balance in the different regions of the hydrographic basin. Based on the European Flood Awareness System (EFAS) data set, a careful method of identification and selection of the Adriatic rivers, followed by a rigorous assessment against observational data, was developed to evaluate the current state of the Adriatic river discharges and their respective trends throughout several climate indicators from 1991 to 2022. Observational data are limited to 85% of the identified rivers, totaling 98% of the overall freshwater input into the Adriatic Sea. The results confirm that the Shallow Northern Adriatic receives the largest freshwater inputs with a daily average exceeding 2,400 m3s−1, which amounts to 61% of the overall Adriatic discharges. Consequently, this region guides the freshwater seasonal cycle of the Adriatic Sea, which presents a well-defined pattern of two flood peaks in late autumn and late spring, separated by a minimum discharge period at mid-summer. From the Central to the Southern Adriatic subregions, the absence of snow-melting effects prevents the secondary flood peak during the spring, shaping the seasonal cycle of river discharges from a single flood peak in late autumn to a drought period in August. The 32 years of continuous river discharge data reveal a negligible trend in the overall Adriatic Sea but a negative trend for the last decade (2013–2022). This decadal decrease is driven by the extreme drought that drastically pounded the northern Adriatic in 2022.

First Survey of the Sponge Community of a Semi-Submerged Marine Cave along the Adriatic Apulian Coast

Mediterranean marine caves have been categorized as both biodiversity reservoirs and vulnerable habitats. However, only a few studies have focused on Porifera assemblages within marine caves along the Adriatic Apulian coast (southern Italy). In this study, the sponge fauna of the Rondinella cave, a semi-submerged marine cave along the coast of Bari (Southern Adriatic Sea), was investigated for the first time. The use of advanced image analysis in combination with targeted sampling has made it possible to determine the spatial distribution and diversity of Porifera along a transect from the entrance to the end of the cave. Data analysis clustered the stations into two groups, separated according to the distance from the entrance and corresponding to the cave entrance and the semi-dark zone. Sponges were found at all stations covering a considerable part of the substrate, with the highest cover values occurring in the semi-dark zone. A total of 54 sponge taxa were identified: 49 Demospongiae, 3 Homoscleromorpha, and 2 Calcarea. Six species are new records for the Apulian marine caves, one species represents a new record for marine caves, and two species are new findings for the southern Adriatic Sea.

Spatio-temporal patterns of whiting (Merlangius merlangus) in the Adriatic Sea under environmental forcing.

Understanding how environmental factors affect species distribution is crucial for the conservation and management of marine organisms, especially in the face of global changes. Whiting (Merlangius merlangus) is a demersal cold-temperate fish, considered a 'relict species' in the Adriatic Sea. Despite its significance to commercial fisheries in the region, the specific drivers behind its spatial and temporal patterns have not been thoroughly examined. Here, we fitted a set of Generalized Linear Mixed Effects Models to data collected in the Northern and Central Adriatic from 1999 to 2019 during the Mediterranean International Trawl Survey to investigate the potential influence of depth, seafloor temperature and seafloor dissolved oxygen on the annual biomass density and spatial distribution of whiting in the spring-summer season. Our results showed that depth, and to a lesser degree temperature and oxygen, are important predictors of whiting distribution in this period, with preferences for depths of ~ 45 m, temperature of ~ 15.4°C and dissolved oxygen > 5.5 ml L-1. We predicted a persistent core area of distribution in front of the Po River Delta, in the Northern Adriatic Sea, while the density progressively declined towards the Central and Southern Adriatic Sea along the Italian coast. Additionally, the temporal trend exhibited high fluctuations over the years, occurring in cycles of 3 to 4 years. Finally, by comparing the biomass density estimates obtained under optimal conditions with those derived from the actual values for each variable, our analysis revealed that temperature had a pronounced and general impact on biomass density in the northern survey area (predictions revealed a density reduction of approximately two-thirds), while oxygen displayed a minor and more localized influence. This work deepens the current knowledge about the ecology of whiting in the Adriatic Sea and provides support for the conservation and management of this species.

The coastal ichthyofauna of the Mediterranean coral reef: the case of Mljet National Park (Croatia, southern Adriatic Sea)

The authors studied the structure of the coastal fish assemblage in a temperate coral reef within a marine protected area in order to provide a baseline information on the occurrence and temporal distribution of fish and to highlight the importance of the coral reef to ichthyofauna. The coastal fish assemblage was investigated at two sites in Veliko jezero (Mljet National Park) in the southern Adriatic Sea with a non-destructive SCUBA visual technique in the period from 2013 to 2021. Altogether, 38 fish taxa were recorded on the right bank (coral reef) and 36 species on the left bank. The presence of the coral reef at a depth range between 9 m to 12 m is the main factor differentiating the fish fauna in these two areas, which are otherwise governed by the same environmental factors. At the coral reef a decrease in fish diversity was discovered with a steady regression from 2013 to 2021.

Influence of hydraulic clam dredging and seasonal environmental changes on macro-benthic communities in the Southern Adriatic (Central Mediterranean Sea)

Macro-benthic communities on the shallowest soft bottoms are impacted by hydraulic dredgers used for the harvesting of the striped venus clam (Chamelea gallina). Changes in macro-benthic assemblages were analysed across four areas in the Southern Adriatic Sea (Central Mediterranean Sea) during the winter and summer 2022 (low and high fishing pressures, respectively). Two sampling surveys were carried out collecting abundance data (N/100m2) of 69 species. Diversity indices (Shannon–Weiner and Equitability) were calculated and differences between seasons and areas were tested using non-parametric tests. Changes in the assemblage and feeding habits were explored by adopting permutational multivariate analysis of variance on 34 species. Moreover, environmental conditions of all areas in the two seasons were characterized by a set of 8 variables. Seasonal changes in diversity were only detected for the Shannon–Weiner index, with values significantly higher in winter than summer. Macro-benthic assemblages differed between the two seasons, and the winter assemblages were well-distinct in each area. In contrast, a high overlap was shown in the summer assemblages of the four areas. Changes in feeding habits showed an increase in filter feeding polychaetes and opportunistic/scavenger species during the summer. Temperature, Salinity and primary production were positively correlated to summer stations indicating potential thermic stress on the assemblages. The results provide information on the benthic community impacted by dredge disturbance and seasonal changes driven by environmental conditions, stressing the need to integrate these aspects in assessments on the health status of marine ecosystems required by European directives and fishery management plans.

Primary production research in the Adriatic Sea

Primary production in the Adriatic Sea has been investigated for many years, however, a comprehensive systematic review of the literature is lacking. This paper aims to fill this gap by providing a thorough overview of all conducted studies, emphasising the methodologies employed, and comparing representative values. The first section introduces the history of primary production measurements and gives insights into the Adriatic basin’s hydrography and its impact on primary producers and their rates of production. The second section provides an overview of productivity across the geographical regions of the Adriatic Sea. The Middle Adriatic Sea stands out as one of the rare locations in the world where in situ measurements of primary production have been systematically conducted since the 1960s and are ongoing. This data has only recently been synthesised and corrected for overestimates using a modelling approach. The final section is an overview of all primary production studies supported with comprehensive summarising tables. Most of the data concerns phytoplanktonprimary production estimated by 14C method. Annual primary production in the Northern and Middle Adriatic ranges between 87.4–260.0 g C m-2 y-1, and 70.0–177.4 g C m-2 y-1, respectively. Southern Adriatic Sea is the least investigated, and only daily estimates are available (236–374 mg C m-2 d-1). The purpose of this review is to highlight the significance of measuring primary production in the Adriatic Sea and the need for future research that will contribute to a more comprehensive understanding of the basin’s productivity.

Urban mobility sustainable plans: Tools and transport policies

This paper provides indications on how to develop a Sustainable Urban Mobility Plan (SUMP) in small and medium-sized cities, bringing the case study of an Italian town located in southern Italy, Brindisi. The guidelines are part of the output of the SuMo (Sustainable Mobility in the Port Cities of the Southern Adriatic) project with the aim of specifically improving the sustainability of transport in Brindisi and, in particular, in the port area. The drafting of this paper is based on the dimensional element of the city which allows adopting a path adhering to the needs of the generators and users of a medium-sized city such as Brindisi in order to make the implementation action effective the adoption of the plan follows. The time frame is short-medium term, however, once the sustainability objectives have been pursued, the repercussions are also long-term. The paper anticipates possible solutions and interventions for the Brindisi port area to provide useful ideas in the subsequent phase of drafting and implementing the SUMP itself. In general terms it will be necessary: to improve accessibility for all, regardless of income and social status; to improve the quality of life and the attractiveness of the urban environment; to improve road safety and public health; to reduce air and noise pollution, greenhouse gases, emissions, and energy consumption by limiting individual motorized mobility; to ensure social equity.

Rockfall Susceptibility Assessment and Landscape Evolution of San Nicola Island (Tremiti Islands, Southern Adriatic Sea, Italy)

San Nicola Island, pertaining to the Tremiti Archipelago (Southern Adriatic Sea, Italy), is widely affected by cliff retreat and gravitational phenomena which severely threaten its monumental historical and natural value. In this study, geomorphological features of the area were derived following a stepwise approach, combining multitemporal stereoscopic aerial photo interpretations with morphometric analyses and detailed field surveys. A rockfall susceptibility map was created following a heuristic approach based on morphometric and geothematic parameters, accounting for slope, slope aspect, outcropping lithologies, structural discontinuities density, distance from landslide scarps, and presence of anthropic caves. Cliff sectors set on dolomitic limestones feature the highest susceptibility values, especially along the southeastern sector; medium values, instead, are found along the island flanks and along scarps located within the inner sectors; and the lowest values are detected on summit tabular surfaces. The achieved results were compared with historical maps and seismic data derived from local and national archives and catalogues, respectively. These analyses allowed us to define the role played by litho-structural and tectonic features on landslide occurrence and distribution, and their interplay in driving landscape evolution over centuries. Finally, this work represents a valuable scientific tool to support geomorphological studies for landslide hazard assessment and proper territorial planning in any other small insular areas, showing similar geological–geomorphological features and landscape values.

Size-dependent distribution of metal(loid)s in recent marine sediments of the Adriatic sea

This paper investigates occurrence of metal(loid)s, and size-dependent changes in their concentration in recent marine sediments from coastal and open-sea environments in the eastern Adriatic. Size fractionation of sediments was performed after removal of organic matter (OM), and the individual fractions, comprising particles below 8 μm, 4 μm, 2 μm, 1 μm and 0.45 μm, were analysed using HR ICP-MS. The concentrations of most elements increased with decreasing particle size, as a result of accumulation of clay minerals and Fe and Mn (oxyhydr)oxides. A decrease in concentrations was observed for Ba, Sr, Ti and U, due to lowering of the carbonate content and presence in the coarse-grained and heavy mineral fraction. The highest element concentrations were determined in the fraction comprising particles below 1 μm. Occasionally, depending on the sedimentological environment and/or the element in question, the peak concentrations occurred in the <2 μm or <0.45 μm fraction. The lowest size-dependent enrichment was observed for elements associated with aluminosilicates (Al, Be, Cs, Co, Fe, K, Li, Rb). A different size-dependent behaviour of the elements was observed between deep-sea areas and shallow environments under greater coastal influence, mainly due to differences in sediment sorting, and between the northern and central vs. southern Adriatic due to the different catchment geologies. The Fe and Mn (oxyhydr)oxides, abundant in the deep-sea sediments, played an important role in the geochemical cycle of As, Cd, Co, Mo, Sb and V.

Prostorno i vremensko širenje kirnji u istočnom Jadranskom moru (Hrvatska) dokumentirano istraživanjem lokalnog ekološkog znanja rekreacijskih ribolovaca

Groupers are important predator marine fish species, and also economically important to commercial and recreational fisheries, but threatened by overfishing worldwide. The dusky grouper (Epinephelus marginatus) is the most common species that historically occurred in the southern and central Eastern Adriatic, while other species were mostly restricted to the southern part of the region or were not recorded in the Adriatic Sea. However, the warming of the sea caused by recent climate change has caused some grouper species in the Eastern Adriatic to expand northward. This spread has been poorly documented, largely because rocky coastal habitats, which are less accessible to conventional research methods that often rely on specific fishing gears, have received far less attention than other more accessible habitats i.e. soft bottoms. Reports of recent grouper expansion are primarily anecdotal and mainly based on the extensive observations of recreational fishermen who mainly utilize rocky coastal habitats. In order to gain insight into this phenomenon, we conducted a survey to investigate the distribution of groupers along the Croatian coast of the eastern Adriatic using the Local Ecological Knowledge methodology. Semi-structured interviews were carried out to record fishers' knowledge and perceptions of changes in their catches, as well as personal observations. The data collected provided information on the spatial and temporal expansion of groupers in the eastern Adriatic over the last 60 years, as perceived by local recreational fishermen.

Deep-Water Dynamics along the 2012–2020 Observations on the Continental Margin of the Southern Adriatic Sea (Mediterranean Sea)

This work presents the results of long-term deep-water observations carried out in the southwestern Adriatic margin. Hydrodynamics and thermohaline measurements were carried out in the last 100 m of the water column using two long-term moorings placed at two different locations along the western sector of the Adriatic continental margin (open slope vs. submarine canyon). The observations, carried out over a period of almost 10 years, made it possible to define the intra- and interannual deep-water dynamics, which are mainly influenced by the passage of cold, dense water. The hydrodynamic field is influenced by seasonal behavior and varies from year to year, with no clear temporal trend or periodicity. Thermohaline properties follow hydrodynamics but also show a climatological trend toward higher temperatures and salinity. The combination and variability of preconditioning factors explains the interannual variability in dense water passage at the mooring sites triggering the formation of dense water in the northern Adriatic. The impulsive nature of the dense water flow, which is difficult to capture with sporadic oceanographic surveys, and its linkage with the large-scale atmospheric circulation make continuous monitoring essential to answer open questions about cascading processes and deep-water dynamics under a global change scenario.

Towards sustainable marine spatial planning of aquaculture

An efficient and adaptive strategy within the EU Marine Spatial Planning Directive has to manage the existing and increasing conflicts between human uses and habitat conservation in coastal-marine areas. Among the different human activities developed along the coasts, aquaculture occupies a primary role. In this context, the aims of this research have been: (1) to propose a conceptual model suitable for aquaculture marine spatial planning; (2) to collect and integrate indicators useful for the characterization of the study area in terms of socio-ecological-economic sensitivities and pressures; and (3) to identify and map the most suitable areas for the development of new fish and shellfish farms. The study area is the Apulia Region (Southern Italy) with a coastline of about 1,000 km, in the Adriatic and Ionian Seas, and characterized by several economic activities within a high value natural context. The evaluation of area’s suitability for fish and shellfish farms have been carried out through the ecological characterization of the coastal areas, the identification of the socio-economic, ecological, cultural, and legal-military constraints and the estimate of the “Suitability Index” that, through a Weighted Linear Combination, integrates environmental variables and allows to classify areas as “Highly Suitable”, “Suitable” or “Unsuitable”. The “highly suitable areas” for new fish and shellfish farms are mainly located in northernmost of the Southern Adriatic Sea along the Gargano coast and in the Gulf of Manfredonia, whilst concerning the Northern Ionian Sea they are at a mean distance of 5 Km from the shoreline. The suitability maps have shown that existing fish farms are in line with their suitable areas but, surprisingly, this has seemed not to be true for shellfish farms. This can be explained by the fact that these aquaculture activities have traditionally been present in some areas (e.g., Taranto Seas), currently strongly impacted by human activities. This research has highlighted that despite aquaculture is generally conceived as an environmental impacting activity, it could be also impacted by other environmental and/or anthropic stressors (i.e., industrial ports, sewage discharges). Considering all these elements, the present research addresses decision-makers, providing information and tools necessary to plan in a more aware way, and also stakeholders interested in investing in the aquaculture sector, who could benefit from the proposed suitability maps for fish and shellfish farms for a sustainable development of this sector.

Seasonal variation in the nutrient composition of mussels (Mytilus galloprovincialis) from farms in Boka Kotorska Bay, Southern Adriatic Sea

The aim of this study was to investigated the seasonal variation in the nutrient composition of Mytilus galloprovincialis, cultivated in Boka Kotorska Bay, Montenegro, during all seasons in one year. Biometric parameters, meat yield, condition index, proximate composition, minerals, and the lipid and fatty acid compositions of mussels were analyzed. The most significant factors determining these parameters were temperature, food amount and gametogenesis The biometric parameters showed no significant differences during the sampling period. In the spring, meat yields and mussel condition index increased at substantial levels. Low values od meat yield and condition index during cold months have resulted from food shortage and reproductive cycle, when mussels use carbohydrates and protein reserves. The highest amount of protein was detected in mussels harvested in August (10.76%), while the highest amount of lipids was recorded in the winter months (2.11%). Docosahexaenoic acid and eicosapentaenoic acid were the most abundant PUFA. The concentration of metals found in mussels from the study area is within the range of mean values reported in the literature. Our results indicate that the best period for mussels harvesting was during the spring and summer (April and August), opposite the winter months when the mussels were not favorable for harvesting.

First data on the effect of Aluminium intake in Chamelea gallina of exploited stocks in the Southern Adriatic Sea (Central Mediterranean Sea)

The striped venus clam Chamelea gallina is an important shellfish resource in coastal area of Mediterranean Basin, playing a fundamental role in the ecosystems. In the last two decades there has been a reduction in the stocks of this bivalve with several mortality events along Adriatic Sea due to pollutants. Aiming to evaluate the effects on clams of the anthropogenic increase of some metals in the sea, we focused on aluminium. In particular, we tested whether Al could affect mucus secretion, since mucins are involved in protection from pathogens and toxicants and transport of alimentary particles and pseudofeces. Aluminium was administered in the form of aluminium chloride at concentrations of 25, 50 and 200 μM. Histochemical and lectin-histochemical - analyses were used to evaluate in situ qualitative and quantitative variation of the muciparous secretions produced by both the gills and foot epithelia. Treatments resulted in quali-quantitative alterations in the secretions of both gills and foot epithelia, in particular reduction of glycosylation resulting in a general decrease of acidic residuals and of mannosylated, glycosaminylated and fucosylated chains. This can result in a decrease of acidity and viscosity of mucus and thus it could affect its functionality and the survival of the animals.

Phytoplankton Size Structure and Diversity in the Transitional System of the Aquatina Lagoon (Southern Adriatic Sea, Mediterranean).

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.