An Ecological Imbalance Induced by a Non-Native Species: The Manila Clam in the Venice Lagoon

Economic costs of non-native species in Türkiye: A first national synthesis

Biological invasions are increasingly recognised as a major global change that erodes ecosystems, societal well-being, and economies. However, comprehensive analyses of their economic ramifications are missing for most national economies, despite rapidly escalating costs globally. Türkiye is highly vulnerable to biological invasions owing to its extensive transport network and trade connections as well as its unique transcontinental position at the interface of Europe and Asia. This study presents the first analysis of the reported economic costs caused by biological invasions in Türkiye. The InvaCost database which compiles invasive non-native species' monetary costs was used, complemented with cost searches specific to Türkiye, to describe the spatial and taxonomic attributes of costly invasive non-native species, the types of costs, and their temporal trends. The total economic cost attributed to invasive non-native species in Türkiye (from 202 cost reporting documents) amounted to US$ 4.1 billion from 1960 to 2022. However, cost data were only available for 87 out of 872 (10%) non-native species known for Türkiye. Costs were biased towards a few hyper-costly non-native taxa, such as jellyfish, stink bugs, and locusts. Among impacted sectors, agriculture bore the highest total cost, reaching US$ 2.85 billion, followed by the fishery sector with a total cost of US$ 1.20 billion. Management (i.e., control and eradication) costs were, against expectations, substantially higher than reported damage costs (US$ 2.89 billion vs. US$ 28.4 million). Yearly costs incurred by non-native species rose exponentially over time, reaching US$ 504 million per year in 2020-2022 and are predicted to increase further in the next 10 years. A large deficit of cost records compared to other countries was also shown, suggesting a larger monetary underestimate than is typically observed. These findings underscore the need for improved cost recording as well as preventative management strategies to reduce future post-invasion management costs and help inform decisions to manage the economic burdens posed by invasive non-native species. These insights further emphasise the crucial role of standardised data in accurately estimating the costs associated with invasive non-native species for prioritisation and communication purposes.

Multidisciplinary long-term survey of Manila clam grown in farming sites subjected to different environmental conditions

In recent years recurrent bivalve mass mortalities considerably increased around the world, causing the collapse of natural and farmed populations. Venice Lagoon has historically represented one of the major production areas of the Manila clam Ruditapes philippinarum in Europe. However, in the last 20 years a 75 % decrease in the annual production has been experienced. While climate change and anthropogenic interventions may have played a key role in natural and farmed stocks reductions, no studies investigated at multiple levels the environmental stressors affecting farmed Manila clam to date. In this work we carried out a long-term monitoring campaign on Manila clam reared in four farming sites located at different distances from the southern Venice Lagoon inlet, integrating (meta)genomic approaches (i.e. RNA-seq; microbiota characterization), biometric measurements and chemical-physical parameters. Our study allowed to characterize the molecular mechanisms adopted by this species to cope with the different environmental conditions characterizing farming sites and to propose hypotheses to explain mortality events observed in recent years. Among the most important findings, the disruption of clam's immune response, the spread of Vibrio spp., and the up-regulation of molecular pathways involved in xenobiotic metabolism suggested major environmental stressors affecting clams farmed in sites placed close to Chioggia's inlet, where highest mortality was also observed. Overall, our study provides knowledge-based tools for managing Manila clam farming on-growing areas. In addition, the collected data is a snapshot of the time immediately before the commissioning of MoSE, a system of mobile barriers aimed at protecting Venice from high tides, and will represent a baseline for future studies on the effects of MoSE on clams farming and more in general on the ecology of the Venice Lagoon.

The influence of salinity on the toxicity of remediated seawater

Mercury (Hg) is one of the most hazardous pollutants, due to its toxicity, biological magnification and worldwide persistence in aquatic systems. Thus, new efficient nanotechnologies (e.g. graphene oxide functionalized with polyethyleneimine (GO-PEI)) have been developed to remove this metal from the water. Aquatic environments, in particular transitional systems, are also subjected to disturbances resulting from climate change, such as salinity shifts. Salinity is one of the most relevant factors that influences the distribution and survival of aquatic species such as mussels. To our knowledge, no studies assessed the ecotoxicological impairments induced in marine organisms exposed to remediate seawater (RSW) under different salinity levels. For this, the focus of the present study was to evaluate the effects of seawater previously contaminated with Hg and remediated with GO-PEI, using the species Mytilus galloprovincialis, maintained at three different salinities (30, 20 and 40). The results obtained demonstrated similar histopathological and metabolic alterations, oxidative stress and neurotoxicity in mussels under RSW treatment at stressful salinity conditions (20 and 40) in comparison to control salinity (30). On the other hand, the present findings revealed toxicological effects including cellular damage and histopathological impairments in mussels exposed to Hg contaminated seawater in comparison to non-contaminated ones, at each salinity level. Overall, these results confirm the high efficiency of GO-PEI to sorb Hg from water with no noticeable toxic effects even under different salinities, leading to consider it a promising eco-friendly approach to remediate contaminated water.

Evidence for self-sustaining populations of Arcuatula senhousia in the UK and a review of this species' potential impacts within Europe

The invasive Asian date mussel (Arcuatula senhousia) inhabits diverse global coastal environments, in some circumstances posing significant ecological and economic risks. Recently recorded in the Greater North Sea ecoregion, an established population has not previously been confirmed. Combining historical and field data, we provided baseline information from the UK and recorded colonisation in a variety of habitats. Gonadal development was assessed using the gonadosomatic index (GSI) to determine if an intertidal soft-sediment population is self-sustaining. Arcuatula senhousia records from subtidal muddy/mixed-sediment within a major estuarine system from 2007 to 2016 were also analysed. First detected in 2011, spatial distribution was variable across the years within the subtidal, with individuals found at 4-9 out of 25 sites, and densities per site varying from 10 to 290 individuals per m². The intertidal population was, in part, associated with seagrass (Zostera spp.) and attached to bivalves. In marinas, individuals were attached to concrete tiles, associated with live Mytilus edulis, and to dead Ostrea edulis. Mean GSI from the intertidal population differed across months, peaking in July before declining in September/October, but with high inter-individual variability. Arcuatula senhousia is reproducing and maintaining viable populations. Using a natural capital approach, we identify the potential impacts on Europe's functionally important habitats, fisheries and aquaculture if its spread continues.

Invasive clams (Ruditapes philippinarum) are better equipped to deal with harmful algal blooms toxins than native species (R. decussatus): evidence of species-specific toxicokinetics and DNA vulnerability

This study aims to assess and compare the kinetics (accumulation/elimination) of the marine biotoxins okadaic acid (OA) and dinophysistoxin-1 (DTX1), between native (Ruditapes decussatus) and invasive (Ruditapes philippinarum) clam species, and their genotoxic effects and DNA recover capacity after, exposure to toxic dinoflagellates Prorocentrum lima. Clams were fed with P. lima for 5 days and then to non-toxic algae (post-exposure) during other 5 days. Toxin concentrations determined in clams by LC-MS/MS were related with DNA damage and repair assessment through the comet and base excision repair (BER) assays, respectively. Differential accumulation patterns were observed between the invasive and native species. The invasive species consistently and progressively accumulated the toxins during the first 24 h of exposure, while the native clams showed drastic variations in the toxin accumulation. Nevertheless, at the end of a 5 days of exposure period, the native clams presented higher toxin concentrations, nearly reaching the legal regulatory limit for human consumption. In addition, native clams were vastly affected by OA and DTX1, presenting an increment in the DNA damage since the first day, with a correspondent increase in the repair activity. On the other hand, invasive clams were not affected by the dinoflagellate toxins, exhibiting only some signs of the challenge, namely an increase in the DNA repair mechanisms in the post-exposure period. Invasive clams R. philippinarum are better adapted to cope with harmful algal blooms and OA-group toxins than native species. These results may increase farming interest and may lead to new introductions of the invasive clams. In sympatry sites, exposure to OA-group toxins may unbalance clams species biomass and distribution as exposure to toxic dinoflagellates affects the native clams from cellular to a population level, representing a significant threat to development and maintenance of R. decussatus populations.

Non-indigenous macrozoobenthic species on hard substrata of selected harbours in the Adriatic Sea

The intense shipping traffic characterising the Adriatic Sea favours the spread of marine organisms. Yet, a study of 12 Adriatic ports (4 on the western side and 8 on the eastern side of the basin) found that non-indigenous species (NIS) accounted for only 4% of the benthic communities settled on hard substrates. The cirripeds Amphibalanus amphitrite and Balanus trigonus, found in 8 harbours, were the most common invaders followed by Amphibalanus eburneus, the ascidian Styela plicata, and the bivalve Magallana gigas. The highest percentage of NIS was recorded in Venice and Ploče, the harbours with the least rich native communities; the lowest percentage was retrieved in Trieste, Koper, Pula, and Rijeka, the harbours hosting the highest species diversity. In contrast, the ports of Bari and Ancona showed both high NIS percentages and highly diversified communities.

Intertidal clams exhibit population synchrony across spatial and temporal scales

Long-term datasets can be particularly useful for parsing out factors influencing populations, yet few studies have utilized continuous datasets to quantify population dynamics in bivalve molluscs. We used dynamic factor analysis on a clam biomass dataset spanning 28 yr and five distinct regions in the southern Salish Sea to determine (1) if native intertidal clam populations exhibit synchrony and (2) what environmental covariates may be correlated with these population trends. Once covariates were accounted for, the model with the most data support included three predominant trends to describe multidecadal change in clam biomass. Intraspecific synchrony was highest among Saxidomus gigantea and Leukoma staminea populations, with no clear evidence of covariance in Clinocardium nuttallii. Specifically, we quantified a pronounced decadal decline in L. staminea and an increase in S. gigantea biomass on most beaches. No beaches showed synchrony in trends across all three species, indicating that species-specific trends (regardless of location) were more common than beach-specific trends (regardless of species). Seven environmental covariates were evaluated in their capacity to explain variability in annual mean biomass. Of these, the North Pacific Gyre Oscillation lagged 4 yr prior to the observation year was most supported by the data in the best fitting model, implying that 4 yr old clam biomass is partially determined by oceanographic processes affecting larval clams. Although results suggest large-scale density-independent factors play a role in venerid clam population dynamics, it is also likely local factors account for variability not explained by our model.

Spatial distribution, bioaccumulation profiles and risk for consumption of edible bivalves: a comparison among razor clam, Manila clam and cockles in the Venice Lagoon

Despite their ecological and economical relevance, a lack of data is still occurring about the distribution, abundance, bioaccumulation and risks for consumption of some edible bivalves. The present study has been carried out in the Venice Lagoon taking into account three bivalve species to investigate i) the possible relationship among the biological features-distribution, abundance and bioaccumulation patterns- of razor clams (Solen marginatus Pulteney, 1799), Manila clams (Ruditapes philippinarum Adams and Reeve, 1850) and lagoon cockles (Cerastoderma glaucum Poiret, 1789) and the hydrological features, namely sediment physico-chemical characteristics and contamination; ii) their specific role as bioindicators of inorganic contamination; iii) the possible risks for human health associated with the consumption of these edible bivalves. Results showed that species distribution and abundance, especially for razor clams, was mainly influenced by environmental conditions and sediment granulometric composition, above metal(loid) contamination. The contamination patterns were different among species, as Manila clam generally showed higher bioaccumulation values for most of the metal(loid)s, whilst lagoon cockles preferentially accumulated Ni. Eventually, a serious concern exists for the human consumption, for all species and investigated sites regarding As. This study will raise attention on the effects of bioaccumulation of inorganic pollutants by edible bivalves and risks for consumers' safety, especially concerning razor clams and cockles, for which a critical lack of data on metal(loid) bioaccumulation occurs from the Northern Adriatic Sea.

Functional traits of a native and an invasive clam of the genus Ruditapes occurring in sympatry in a coastal lagoon

The main objective of this study was to evaluate the functional traits regarding bioturbation activity and its influence in the nutrient cycling of the native clam species Ruditapes decussatus and the invasive species Ruditapes philippinarum in Ria de Aveiro lagoon. Presently, these species live in sympatry and the impact of the invasive species was evaluated under controlled microcosmos setting, through combined/manipulated ratios of both species, including monospecific scenarios and a control without bivalves. Bioturbation intensity was measured by maximum, median and mean mix depth of particle redistribution, as well as by Surface Boundary Roughness (SBR), using time-lapse fluorescent sediment profile imaging (f-SPI) analysis, through the use of luminophores. Water nutrient concentrations (NH₄-N, NO_x-N and PO₄-P) were also evaluated. This study showed that there were no significant differences in the maximum, median and mean mix depth of particle redistribution, SBR and water nutrient concentrations between the different ratios of clam species tested. Significant differences were only recorded between the control treatment (no bivalves) and those with bivalves. Thus, according to the present work, in a scenario of potential replacement of the native species by the invasive species, no significant differences are anticipated in short- and long-term regarding the tested functional traits.

3,3'-dichlorobiphenyl (non-Aroclor PCB-11) as a marker of non-legacy PCB contamination in marine species: comparison between Antarctic and Mediterranean bivalves

In this study the accumulation of the 3,3'-dichlorobiphenyl (PCB-11) in monitoring organisms from the Antarctic and Mediterranean coastal environments has been investigated. This lesser-known PCB congener, unrelated to the industrial use of commercial mixtures, continues to be generated and released into the environment mainly as an unintentional by-product of pigment manufacturing. Specimens of the filter-feeders Adamussium colbecki from Terra Nova Bay and of Mytilus galloprovincialis and Ruditapes philippinarum from the north-western Adriatic coasts were collected and analyzed for PCB-11 by Gas Chromatography coupled both to Low-Resolution and High-Resolution Mass Spectrometry (LRMS, HRMS). In order to assess the influence of PCB-11 with respect to the legacy contamination, 126 PCB congeners related to the Aroclor commercial mixtures were simultaneously analyzed. PCB-11 was detected in all the samples, regardless of the species and of the geographical area, representing on average 17.6% and 15.6% of the total PCBs (n = 127) in Antarctic and Mediterranean samples, respectively. In the Adriatic area the highest concentrations were related to the influence of industrial activities or ship traffic, while the highest value found in Antarctic specimens, namely those collected in the austral summer 1997-1998, was ascribed to a local anthropogenic source. The occurrence of PCB-11 in the other samples from Terra Nova Bay may be related to Long-Range Atmospheric Transport (LRAT), facilitated by the higher volatility of the analyte compared to the heavier PCB congeners. Nevertheless, more in-depth studies are needed in order to evaluate the relative contribution of local and distant sources.

Native and introduced clams biochemical responses to salinity and pH changes

By the end of year 2100 physiological and biochemical performance of aquatic organisms are expected to become strongly affected by salinity and pH shifts, which in turn may favor the conditions for introduced species to invade new ecosystem areas. Given this, we evaluated the effects of salinity and pH changes in native Ruditapes decussatus and introduced Ruditapes philippinarum clams, by measuring different biomarkers related to oxidative stress, metabolic activity and osmoregulation capacity. Results showed that extreme salinities induced mortality in both species, while all clams survived under low pH (7.3). Both species mobilized glycogen as a source of energy towards cells protection mechanisms under extreme salinities. The native species presented higher lipid peroxidation levels while the introduced species was able to prevent oxidative damages through the induction of antioxidant enzymes at most extreme salinities. R. philippinarum also induced CA activity to balance the ion homeostasis at extreme salinities. In contrast, low pH induced oxidative damages, an increase of antioxidant (catalase), detoxification (glutathione S-transferases) and osmoregulation (carbonic anhydrase) mechanisms in R. philippinarum compared to the native clams. Overall, salinity and pH changes can alter physiological and biochemical status of native and introduced clam species.

Caffeine impacts in the clam Ruditapes philippinarum: Alterations on energy reserves, metabolic activity and oxidative stress biomarkers

Caffeine is known to be one of the most consumed psychoactive drugs. For this reason, caffeine is continuously released into the environment with potential impacts on inhabiting organisms. The current study evaluated the biochemical alterations induced in the clam species Ruditapes philippinarum after exposure for 28 days to caffeine (0.5, 3.0 and 18.0 μg/L). The results obtained showed that, with the increasing caffeine concentrations, an increase in clams defense mechanisms (such as antioxidant and biotransformation enzymes activity) was induced which was accompanied by an increase in protein content. Nevertheless, although an increase on defense mechanisms was observed, clams were not able to prevent cells from lipid peroxidation that increased with the increase of caffeine concentration. Furthermore, with the increase of exposure concentrations, clams increased their metabolic activity (measured by electron transport activity), reducing their energy reserves (glycogen content), to fight against oxidative stress. Overall, the present study demonstrated that caffeine may impact bivalves, even at environmentally relevant concentrations, inducing oxidative stress in organisms. The present study is an important contribution to address knowledge gaps regarding the impacts of long-term exposures to pharmaceuticals since most of the studies assessed the effects after acute exposures, most of them up to 96 h.

Combined effects of seawater acidification and salinity changes in Ruditapes philippinarum

Due to human activities, predictions for the coming years indicate increasing frequency and intensity of extreme weather events (rainy and drought periods) and pollution levels, leading to salinity shifts and ocean acidification. Therefore, several authors have assessed the effects of seawater salinity shifts and pH decrease on marine bivalves, but most of these studies evaluated the impacts of both factors independently. Since pH and salinity may act together in the environment, and their impacts may differ from their effects when acting alone, there is an urgent need to increase our knowledge when these environmental changes act in combination. Thus, the present study assessed the effects of seawater acidification and salinity changes, both acting alone and in combination, on the physiological (condition index, Na and K concentrations) and biochemical (oxidative stress related biomarkers) performance of Ruditapes philippinarum. For that, specimens of R. philippinarum were exposed for 28days to the combination of different pH levels (7.8 and 7.3) and salinities (14, 28 and 35). The results obtained showed that under control pH (7.8) and low salinity (14) the physiological status and biochemical performance of clams was negatively affected, revealing oxidative stress. However, under the same pH and at salinities 28 and 35 clams were able to maintain/regulate their physiological status and biochemical performance. Moreover, our findings showed that clams under low pH (7.3) and different salinities were able to maintain their physiological status and biochemical performance, suggesting that the low pH tested may mask the negative effects of salinity. Our results further demonstrated that, in general, at each salinity, similar physiological and biochemical responses were found in clams under both tested pH levels. Also, individuals under low pH (salinities 14, 28 and 25) and exposed to pH 7.8 and salinity 28 (control) tend to present a similar response pattern. These results indicate that pH may have a lower impact on clams than salinity. Thus, our findings point out that the predicted increase of CO2 in seawater and consequent seawater acidification will have fewer impacts on physiological and biochemical performance of R. philippinarum clams than salinity shifts.

Assessing the geographic scale of genetic population management with microsatellites and introns in the clam Ruditapes decussatus

The clam Ruditapes decussatus is commercially important in southwestern Europe, suffering from population decline and hybridization with exotic Manila clam (R. philippinarum). Previous studies with intronic markers showed a genetic subdivision of the species in three races (Atlantic, West Mediterranean, and Adriatic-Aegean). However, detailed population genetic studies to help management of the main production areas in the southwest of Europe are missing. We have analyzed eight Atlantic and two Mediterranean populations from the Spanish coasts using 14 microsatellites and six intronic markers. Microsatellites confirmed the Atlantic and West Mediterranean races detected with introns and showed that genetic variability was higher in Mediterranean than in Atlantic populations. Both marker types showed that genetic differentiation of Atlantic populations was low and indicated that populations could be managed at the regional level in the case of Cantabrian and Gulf of Cadiz areas, but not in the case of Rias Baixas and the Mediterranean. This study shows the interest of including different types of markers in studies of genetic population structure of marine organisms.

Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX

A combination of historical bivalve surveys spanning 30–50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration.

Oxidative effects of the pharmaceutical drug paracetamol on the edible clam Ruditapes philippinarum under different salinities

Paracetamol, a drug with analgesic and antipyretic properties, is one of the most used substances in human therapeutics, being also frequently detected in aquatic environments. Recent studies report its toxicity towards aquatic species, but the overall amount of data concerning its effects is still scarce. Global changes, likely alterations in abiotic conditions, including salinity, can modulate the interactions of contaminants with biota, conditioning the toxicological responses elicited also by pharmaceuticals. The present article describes the oxidative toxic effects posed by paracetamol on the clam species Ruditapes philippinarum under different salinity conditions. The results demonstrated the establishment of an oxidative-based effect, with significant alteration of several parameters, such as superoxide dismutase (SOD) and the ratio of reduced/oxidized glutathione (GSH/GSSG). Water salinity influenced the response of clams exposed to different paracetamol concentrations, showing the importance of studying physiological traits under realistic test conditions, which are likely to vary in great extent as a result of climate change.

Insights into the establishment of the Manila clam on a tidal flat at the southern end of an introduced range in Southern California, USA

Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam's post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e.g., riprap, boulders). We measured likely environmental influences (e.g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range.

Natural recovery and planned intervention in coastal wetlands: Venice Lagoon (northern Adriatic Sea, Italy) as a case study

The goals of conservation and sustainable use of environmental ecosystems have increased the need for detailed knowledge of ecological evolution and responses to both anthropogenic pressures and recovery measures. The present study shows the effects of natural processes and planned intervention in terms of reducing nutrient inputs in a highly exploited coastal lagoon, describing its evolution over a 16-year period from the late 1980s (when eutrophication was at its peak) until 2003. Changes in nutrient and carbon concentrations in the top layer of sediments were investigated in parallel with macroalgal and seagrass biomass in the most anthropized basin of Venice Lagoon in four surveys conducted in accordance with the same protocols in 1987, 1993, 1998, and 2003. A pronounced reduction in trophic state (mainly total nitrogen, organic phosphorus, and organic carbon concentrations) and macroalgal biomass was recorded, together with the progressive expansion of seagrass meadows. General considerations are also made on the effects of Manila clam farming and the shift from illegal to managed clam farming.

Linking food web functioning and habitat diversity for an ecosystem based management: a Mediterranean lagoon case-study

We propose a modelling approach relating the functioning of a transitional ecosystem with the spatial extension of its habitats. A test case is presented for the lagoon of Venice, discussing the results in the context of the application of current EU directives. The effects on food web functioning due to changes related to manageable and unmanageable drivers were investigated. The modelling procedure involved the use of steady-state food web models and network analysis, respectively applied to estimate the fluxes of energy associated with trophic interactions, and to compute indices of food web functioning. On the long term (hundred years) temporal scale, the model indicated that the expected loss of salt marshes will produce further changes at the system level, with a lagoon showing a decrease in the energy processing efficiency. On the short term scale, simulation results indicated that fishery management accompanied by seagrass restoration measures would produce a slight transition towards a more healthy system, with higher energy cycling, and maintaining a good balance between processing efficiency and resilience. Scenarios presented suggest that the effectiveness of short term management strategies can be better evaluated when contextualized in the long term trends of evolution of a system. We also remark the need for further studying the relationship between habitat diversity and indicators of food web functioning.

Tolerance of Venerupis philippinarum to salinity: osmotic and metabolic aspects

In the last few decades, attention has been focused on the impacts of contamination in marine benthic populations, while the responses of aquatic organisms to natural alterations, namely changes in salinity, have received little attention. In fact, salinity is one of the dominant environmental factors affecting marine bivalves. The ebb and flood of the tide, combined with fresh water inputs from rivers or heavy rainy events, and with extremely dry and hot seasons, can dramatically alter water salinity. Therefore, the salinity of a certain environment can restrict the spatial distribution of a given population, which is especially important when assessing the spread of an invasive species into a new environment. In the present study, the main objective was to understand how clam Venerupis philippinarum copes with salinity changes and, hence biochemical and metabolomic alterations, taking place in individuals submitted to a wide range of salinities were investigated. The results showed that V. philippinarum presented high mortality at lower salinities (0 and 7 g/L) but tolerated high salinities (35 and 42 g/L). The quantification of ionic content revealed that, clams had the capacity to maintain ionic homeostasis along the salinity gradient, mainly changing the concentration of Na, but also with the influence of Mg and Ca. The results showed a decrease in protein content at lower salinities (0 to 21 g/L). Glycogen and glucose increased with increasing salinity gradient. (1)H Nuclear Magnetic Resonance (NMR) spectra of clam aqueous extracts revealed different metabolite profiles at 7, 28 and 42 g/L salinities, thus enabling metabolite changes to be measured in relation to salinity.

Vulnerability of artisanal fisheries to climate change in the Venice Lagoon

Within the context of global warming, the western coast of the northern Adriatic Sea can be regarded as an extremely vulnerable area. Owing to the local geographic features, this area has been described as the Venetian lacuna, where Mediterranean Sea climatic conditions are replaced by Atlantic Ocean ones, supporting the presence of glacial relicts, such as sprat Sprattus sprattus, flounder Platichthys flesus and brown shrimp Crangon crangon. Nektonic assemblage therefore represents a good candidate in terms of an early proxy for thermal regime alterations. It represents a dynamic component of the lagoon ecosystem, changing in space and time, actively moving through the entire system, and dynamically exchanging with the open sea. Here, the first signals of the change have been already detected, such as the presence of alien thermophilic species. Within this context, since the beginning of the century, sampling of the nektonic assemblage has been carried out, integrating them with landings data from the fish market. Vulnerabilities to thermal regime changes have been tested by (1) categorizing species according to the mean distribution area in terms of latitudinal range (over 45°, 30°-45° and below 30°), and (2) analysing both spatial and temporal variations within fishing grounds. Results indicated a high potential vulnerability of the artisanal fishery to climate change, as the commercial catch is entirely composed of species from cold (>45° N) and temperate (between 45° and 30° N) latitudes. At present no alien thermophilic species have been recorded within the lagoon, which is possibly a sign of good resilience of the assemblage. Finally, abundance of species from cold latitudes has decreased during the past decade. All of this has been discussed in the context of the mean annual temperature trend.

Biochemical effects of acetaminophen in aquatic species: edible clams Venerupis decussata and Venerupis philippinarum

Acetaminophen (paracetamol) is one of the most used pharmaceutical drugs, due to its antipyretic and analgesic properties that turn it into a primary choice in varied pathologies and conditions. However, and despite its massive use, acetaminophen is not exempt of adverse effects, especially when administered in over dosage, which are related to the formation of toxic metabolites by oxidative pathways. It is thus possible to observe that toxicity caused by acetaminophen is usually mediated by reactive oxygen species and can result in multiple effects, ranging from protein denaturation to lipid peroxidation and DNA damage. The occurrence of acetaminophen has been reported in the aquatic environment, being important to address the potential exertion of toxic effects on nontarget environmentally exposed organisms. The present study intended to characterize the effects of acute acetaminophen exposure on physiological traits (antioxidant defense, oxidative damage) of two species of bivalves, namely, the edible clams Venerupis decussata and Venerupis philippinarum. Results showed a significant increase in all oxidative stress biomarkers, evidencing the bioactivation of acetaminophen into a deleterious prooxidant, triggering the onset of deleterious effects. Furthermore, strong interspecific differences were observed among responses of the two tested species, which was a major issue due to intrinsic ecological implications when one considers that both species share the same habitat.

Assessing the significance of Ruditapes philippinarum as a sentinel for sediment pollution: bioaccumulation and biomarker responses

The present study assessed whether the bivalve Ruditapes philippinarum may be appropriately deployed as a bioindicator in monitoring transitional environments, in terms of bioaccumulation potential and biomarker responses. The concentrations of trace metals, PAHs and PCBs were determined in sediments and clam tissue, and biomarkers were estimated at various levels of biological complexity (i.e. metallothioneins, lipofuscins, survival-in-air and reburrowing behaviour). Sediments and clams were collected biannually in 2004 and 2005 at eight sites within Venice lagoon, which were influenced differently by natural and anthropogenic impacts. Results highlighted that the broad variations of pollutant concentrations in sediments were not consistent either with the body residuals or with the biomarker responses. Consequently, on the basis of the observed weak responsiveness and sensitivity to anthropogenic stressors we suggest a more cautious use for R. philippinarum as sentinel organism, at least in estuarine sediments in the north Adriatic transitional areas.

Ruditapes decussatus and Ruditapes philippinarum exposed to cadmium: toxicological effects and bioaccumulation patterns

Since differences in metal accumulation may exist between bivalve species, the aim of this study was to assess the impact of cadmium (Cd) on Ruditapes decussatus and Ruditapes philippinarum. For this, the Cd accumulation, mortality rates and biochemical responses were analysed in the two species after 5days of exposure, under laboratory-controlled conditions. The concentration of Cd that caused 50% of mortality on clams was two-times higher in R. decussatus than in R. philippinarum. For both species, higher percentage (84.5-98.2%) of the Cd was in the insoluble fraction, but the Cd concentration in solution was 3 to 8 times higher in R. decussatus. Nevertheless, R. philippinarum presented higher oxidative stress and higher CAT activity. The paradox observed between the two clams can be explained by the higher capacity of R. decussatus to increase the expression of MTs when exposed to Cd.

Overview of ecotoxicological studies performed in the Venice Lagoon (Italy)

This work reports on the state of the art of the bioindicators used to assess environmental quality (regarding chemical pollutant impacts) in the Venice lagoon. After a brief description of the roles, advantages and limitations of bioindicators in marine and transitional environments and a summary of the Venice lagoon characteristics, the ecotoxicological methods used during scientific studies and research projects in the Lagoon are reported. Since not all data are available and no database can be formulated, the main evidence from toxicity bioassays, biomarkers and bioaccumulation analyses since the end of the 1970s is spatially synthesized using maps and discussed according to the four Venice lagoon basins. The majority of indicators showed that the Lido basin (north-central lagoon), affected by the presence of the industrial area and the city of Venice, is the one most highly impacted (particularly in the sites located within or in front of the industrial area, which showed very high sediment toxicity and high levels of DNA damage). The Malamocco basin (south-central lagoon) seems to be the least problematic. The southern basin (Chioggia basin) was shown to be impacted by urban contaminants from the town of Chioggia. The northern basin (Treporti basin) presented both impacted sites (high toxicity and high bioaccumulation factor) and relatively unpolluted sites (absence of toxicity, absence of imposex and low levels of bioaccumulation). This review can serve as a basis on which to select pragmatic, cost-effective biomonitoring techniques for environmental effects in lagoon ecosystems.

Application of biotic indices and relationship with structural and functional features of macrobenthic community in the lagoon of Venice: an example over a long time series of data

In the context of the application of WFD, a scientific debate is growing about the applicability of biotic indices in coastal and transitional waters. In the present work, the question about the discriminating power of different biotic indices and the relationships with the structure and functioning of the macrobenthic community in a transitional environment is discussed. A time series of samples collected during the last 70 years in the lagoon of Venice, reflecting different environmental conditions (a sort of 'pristine state' in 1935, the distrophic crisis in 1988 and subsequent modifications in 1990, the invasion by an alien species and the developing of high impacting fishery in 1999) has been used. The comparison of results obtained by applying different biotic indices, such as AMBI, Bentix and BOPA, shows differences in the discriminating power of indices and a general overestimation of environmental conditions. Discrepancies between environmental status as indicated by biotic indices and the structure and functioning of the benthic community have been highlighted.