Biological effects of palytoxin-like compounds from Ostreopsis cf. ovata: a multibiomarkers approach with mussels Mytilus galloprovincialis

Subcellular effects and lipid metabolism alterations in the gilthead seabream Sparus aurata fed on ovatoxins-contaminated mussels

The marine microalgae Ostreopsis cf. ovata are a well-known producer of palytoxin (PlTXs) analogues, i.e. ovatoxins (OVTXs) among others, which arouse concern for animal and human health. Both in field and laboratory studies, presence of OVTXs, detected in species directly feeding on O. cf. ovata, was frequently correlated with impairment on organisms' physiology, development and behaviour, while similar knowledge is still lacking for animals feeding on contaminated preys. In this study, transfer and toxicity of OVTXs were evaluated in an exposure experiment, in which gilthead seabream Sparus aurata was fed with bivalve mussel Mytilus galloprovincialis, contaminated by a toxic strain of O. cf. ovata. Mussels exposed to O. cf. ovata for 21 days accumulated meanly 188 ± 13 μg/kg OVTXs in the whole tissues. Seabreams fed with OVTX-contaminated mussels started to reject the food after 6 days of contaminated diet. Although no detectable levels of OVTXs were measured in muscle, liver, gills and gastro-intestinal tracts, the OVTX-enriched diet induced alterations of lipid metabolism in seabreams livers, displaying a decreased content of total lipid and fatty acid, together with overexpression of fatty acid biosynthetic genes, downregulation of β-oxidation genes and modulation of several genes related to lipid transport and regulation. Results from this study would suggest the hypothesis that OVTXs produced by O. cf. ovata may not be subject to bioaccumulation in fish fed on contaminated preys, being however responsible of significant biological effects, with important implications for human consumption of seafood products.

Molecular Phylogeny, Morphology, Growth and Toxicity of Three Benthic Dinoflagellates Ostreopsis sp. 9, Prorocentrum lima and Coolia monotis Developing in Strait of Gibraltar, Southwestern Mediterranean

Few works have been carried out on benthic harmful algal blooms (BHAB) species in the southern Mediterranean and no data are available for the highly dynamic Strait of Gibraltar (western Mediterranean waters). For the first time, Ostreopsis sp. 9, Prorocentrum lima and Coolia monotis were isolated in this key region in terms of exchanges between the Atlantic Ocean and the Mediterranean and subject to intense maritime traffic. Ribotyping confirmed the morphological identification of these three dinoflagellates species. Monoclonal cultures were established and the maximum growth rate and cell yield were measured at a temperature of 24 °C and an irradiance of 90 µmol photons m-2 s-1, for each species: 0.26 ± 0.02 d-1 (8.75 × 103 cell mL-1 after 28 days) for Ostreopsis sp. 9, 0.21 ± 0.01 d-1 (49 × 103 cell mL-1 after 145 days) for P. lima and 0.21 ± 0.01 d-1 (10.02 × 103 cell mL-1 after 28 days) for C. monotis. Only P. lima was toxic with concentrations of okadaic acid and dinophysistoxin-1 measured in optimal growth conditions ranging from 6.4 pg cell-1 to 26.97 pg cell-1 and from 5.19 to 25.27 pg cell-1, respectively. The toxin content of this species varied in function of the growth phase. Temperature influenced the growth and toxin content of P. lima. Results suggest that future warming of Mediterranean coastal waters may lead to higher growth rates and to increases in cellular toxin levels in P. lima. Nitrate and ammonia affected the toxin content of P. lima but no clear trend was noted. In further studies, we have to isolate other BHAB species and strains from Strait of Gibraltar waters to obtain more insight into their diversity and toxicity.

Environmental, human health and socioeconomic impacts of Ostreopsis spp. Blooms in the NW Mediterranean

This paper summarizes the research conducted by the partners of the EU co-funded CoCliME project to ascertain the ecological, human health and economic impacts of Ostreopsis (mainly O. cf. ovata) blooms in the NW Mediterranean coasts of France, Monaco and Spain. This knowledge is necessary to design strategies to prevent, mitigate and, if necessary, adapt to the impacts of these events in the future and in other regions. Ostreopsis proliferations in the Mediterranean have been related to massive mortalities of benthic organisms and to symptoms of respiratory and cutaneous irritation in humans. A six-year epidemiologic study in a Ostreopsis hot spot in Catalonia and the accumulated experience of the French Mediterranean National Ostreopsis Surveillance Network confirm the main effects of these blooms on human health in the NW Mediterranean. The impacts are associated to direct exposure to seawater with high Ostreopsis cell concentrations and to inhalation of aerosols containing unknown irritative chemicals produced under certain circumstances during the blooms. A series of mild acute symptoms, affecting the entire body as well as the ophthalmic, digestive, respiratory and dermatologic systems have been identified. A main remaining challenge is to ascertain the effects of the chronic exposure to toxic Ostreopsis blooms. Still, the mechanisms involved in the deletereous effects of Ostreopsis blooms are poorly understood. Characterizing the chemical nature of the harmful compounds synthesized by Ostreopsis as well as the role of the mucus by which cells attach to benthic surfaces, requires new technical approaches (e.g., metabolomics) and realistic and standardized ecotoxicology tests. It is also necessary to investigate how palytoxin analogues produced by O. cf. ovata could be transferred through the marine food webs, and to evaluate the real risk of seafood poisonings in the area. On the other hand, the implementation of beach monitoring and surveillance systems in the summer constitutes an effective strategy to prevent the impacts of Ostreopsis on human health. In spite of the confirmed noxious effects, a survey of tourists and residents in Nice and Monaco to ascertain the socioeconomic costs of Ostreopsis blooms indicated that the occurrence of these events and their impacts are poorly known by the general public. In relationship with a plausible near future increase of Ostreopsis blooms in the NW Mediterranean coast, this survey showed that a substantial part of the population might continue to go to the beaches during Ostreopsis proliferations and thus could be exposed to health risks. In contrast, some people would not visit the affected areas, with the potential subsequent negative impacts on coastal recreational and touristic activities. However, at this stage, it is too early to accurately assess all the economic impacts that a potentially increasing frequency and biogeographic expansion of the events might cause in the future.

Ecotoxicological Impact of the Marine Toxin Palytoxin on the Micro-Crustacean Artemia franciscana

Palytoxin (PLTX) is a highly toxic polyether identified in various marine organisms, such as Palythoa soft corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. In addition to adverse effects in humans, negative impacts on different marine organisms have been often described during Ostreopsis blooms and the concomitant presence of PLTX and its analogues. Considering the increasing frequency of Ostreopsis blooms due to global warming, PLTX was investigated for its effects on Artemia franciscana, a crustacean commonly used as a model organism for ecotoxicological studies. At concentrations comparable to those detected in culture media of O. cf. ovata (1.0–10.0 nM), PLTX significantly reduced cysts hatching and induced significant mortality of the organisms, both at larval and adult stages. Adults appeared to be the most sensitive developmental stage to PLTX: significant mortality was recorded after only 12 h of exposure to PLTX concentrations > 1.0 nM, with a 50% lethal concentration (LC50) of 2.3 nM (95% confidence interval = 1.2–4.7 nM). The toxic effects of PLTX toward A. franciscana adults seem to involve oxidative stress induction. Indeed, the toxin significantly increased ROS levels and altered the activity of the major antioxidant enzymes, in particular catalase and peroxidase, and marginally glutathione-S-transferase and superoxide dismutase. On the whole, these results indicate that environmentally relevant concentrations of PLTX could have a negative effect on Artemia franciscana population, suggesting its potential ecotoxicological impact at the marine level.

Effects of the toxic dinoflagellates Prorocentrum lima and Ostreopsis cf. ovata on immune responses of cultured oysters Crassostrea gasar

Oyster production in Brazil has been highlighted as an important economic activity and is directly impacted by the quality of the environment, which is largely the result of human interference and climate change. Harmful algal blooms occur in aquatic ecosystems worldwide, including coastal marine environments which have been increasing over the last decades as a result of global change and anthropogenic activities. In this study, the native oysters Crassostrea gasar from Northeast of Brazil were exposed to two toxic benthic dinoflagellate species, Prorocentrum lima and Ostreopsis cf. ovata. Their respective effects on C. gasar physiology and defense mechanisms were investigated. Oyster hemocytes were first exposed in vitro to different concentrations of both dinoflagellate species to assess their effects on hemocyte functions, such as phagocytosis, production of reactive oxygen species, as well as mortality. Results highlighted an alteration of hemocyte phagocytosis and viability in presence of O. cf. ovata, whereas P. lima did not affect the measured hemocyte functions. In a second experiment, oysters were exposed for 4 days in vivo to toxic culture of O. cf. ovata to assess its effects on hemocyte parameters, tissues damages and pathogenic Perkinsus spp. infection. An increase in hemocyte mortality was also observed in vivo, associated with a decrease of ROS production. Histopathological analyses demonstrated a thinning of the epithelium of the digestive tubules of the digestive gland, inflammatory reaction and a significant increase in the level of infection by Perkinsus spp. in oysters exposed to O. cf. ovata. These results indicate that oysters C. gasar seem to be pretty resilient to an exposure to P. lima and may be more susceptible to O. cf. ovata. Furthermore, the latter clearly impaired oyster physiology and defense mechanisms, thus highlighting that harmful algal blooms of O. cf. ovata could potentially lead to increased susceptibility of C. gasar oysters to parasite infections.

Toxin accumulation, detoxification and oxidative stress in bivalve (Anomalocardia flexuosa) exposed to the dinoflagellate Prorocentrum lima

Prorocentrum lima is a cosmopolitan benthic dinoflagellate capable of producing the diarrhetic shellfish toxins (DSTs) okadaic acid (OA) and dinophysistoxin (DTX). These compounds may cause oxidative stress and accumulate in bivalve tissues, which become vectors of intoxication to human consumers. We investigated DST accumulation, detoxification and oxidative stress biomarkers in clams (Anomalocardia flexuosa) experimentally exposed to P. lima cells or their compounds. Experimental diets consisted of 6000 cells mL-1 of the non-toxic chlorophyte Tetraselmis sp. (C; control condition), and combinations of C with 10 P. lima cells mL-1 (T10), 100 P. lima cells mL-1 (T100), or to a toxin concentration of ∼4 μg OA L-1 and ∼0.65 μg DTX-1 L-1 (T100d). Clams were exposed to these diets for 7 days (uptake phase), followed by a 7-day depuration period. No DSTs were detected in clams exposed to treatments C (control) nor to T100d (dissolved compounds) during either uptake or detoxification phase. Conversely, clams exposed to T10 or T100 accumulated, on average, up to 2.5 and 35 μg DST kg-1 in their whole bodies at the end of the uptake phase. These concentrations are ∼64 and ∼4.5 times lower than the regulatory level of 160 μg OA kg-1, respectively. Accumulated OA quotas were 12-22 times higher in the digestive gland (DG) than in remaining tissues over the uptake phase. Quick toxin transformation was indicated by the early detection of conjugated compounds - DTX-1 and OA esters - in the DG after 6 h of exposure, with OA-ester representing the main compound (30 - 100 %) in that tissue over the experiment. During the depuration period, detoxification rates represented 0.024 h-1, 0.04 h-1 and 0.052 h-1 for OA, DTX-1 and OA-ester, respectively. The activities of catalase, glutathione S-transferase, glutathione peroxidase and the levels of oxidative stress by lipoperoxidation varied similarly in the DG of A. flexuosa individuals subjected to T100, T100d and the control condition. However, contrasting antioxidant responses were measured in those exposed to T10. These findings indicate that no oxidative stress was primarily induced by DST-producing dinoflagellates in this clam species under laboratory conditions representative of toxic bloom situations. Even though, possible interactions should be considered under multistressor scenarios.

Structural variation of potentially toxic epiphytic dinoflagellates on Thalassia testudinum from two coastal systems of Colombian Caribbean

Some benthic dinoflagellates produce toxins that can affect other organisms including humans, and their proliferation seems to be related to the environmental variability. For this reason, the present study aims to compare the structural variation of potentially toxic dinoflagellates associated with the seagrass Thalassia testudinum from two nearby systems, with different environmental characteristics in Colombian Caribbean, corresponding to a brackish water coastal lagoon and an adjacent bay. Between January 2014 and December 2015, leaves of T. testudinum were collected monthly to obtain the dinoflagellates. Salinity, temperature, dissolved oxygen, pH, nutrients and total suspended solids (TSS) were measured, and precipitation data and the Oceanic Niño Index (ONI) were obtained. Dinoflagellates were detached from the leaves, morphologically identified by analyzing their thecal plates arrangements, and quantified using a Sedgewick-Rafter chamber. The information was analyzed using standard statistics and regression models. Fourteen species of potentially toxic epiphytic dinoflagellate belonging to four genera were recorded, being Prorocentrum the most representative in number of species. The maximum density, dominated by P. lima, were found in Bahía Chengue during the rainy season of 2014 (18452 and 20109 cells g^-1 w.w.), with salinity of 35.50, high temperatures (>29.60 °C), dissolved oxygen >6 mg L^-1, pH close to 8 and TSS >85 mg L^-1. Densities at the Lagoon were lower than 80 cells g^-1 w.w. with the highest values of Prorocentrum sp.1 under different environmental conditions. With the statistical relationships between the most abundant species and the main environmental variables, fundamental niche models were proposed in which cells could proliferate. The degree of risk to human health due to the presence of these potentially toxic epiphytic dinoflagellates will not be resolved until their toxicity discarded.

Effects of palytoxins extracted from Ostreopsis ovata on the oxidative stress and immune responses in Pacific white shrimp Litopenaeus vannamei

Palytoxins (PLTXs) are a group of complex and poisonous marine natural products that are toxic to marine life and even human beings. In the present study, the oxidative stress and immune response in the hepatopancreas and gills of Litopenaeus vannamei were assessed for 72 h after injection with PLTX extracts. Chemical and physiological parameters, e.g., the respiratory burst (O₂^-), activities of antioxidant enzymes, oxidative damage to lipids, carbonylation of proteins, and immune gene mRNA expression levels, were analysed. The results showed that the PLTX extract was not fatal to the shrimp but could reduce their mobility. The O₂^- levels in the gills gradually increased after exposure to PLTX extracts and were significantly higher than those in the control from 6 to 72 h. The malondialdehyde content, lipid peroxidation, protein carbonyl levels, and total antioxidant capacity in the gills all peaked at 12 h. At the same time, the gills were loosely connected, there was a clear disintegration of the epithelial tissue, and the stratum corneum disappeared after 12 h. In addition, compared to those in the control group, the PLTX extract treatment increased the O₂^- content, malondialdehyde content, lipid peroxidation, and protein carbonyl levels from 12 to 72 h, 24-48 h, 12-24 h, and 12-72 h after injection in the hepatopancreas of the shrimp, respectively. Both the Crustin and Toll gene expression levels significantly increased in the hepatopancreas compared to those in the control 6-72 h after injection of the toxin. In parallel, the expression levels of the manganese superoxide dismutase gene gradually decreased from 6 to 48 h and returned to normal levels after 72 h. Interestingly, the total antioxidant capacity also significantly increased compared to that in the control from 6 to 72 h. Our results indicate that although PLTX extracts cause lipid peroxidation and carbonylation of proteins in hepatopancreatic cells, leading to their damage, they did not cause a decrease in the total antioxidant capacity of the hepatopancreas.

Biological Effects of the Azaspiracid-Producing Dinoflagellate Azadinium dexteroporum in Mytilus galloprovincialis from the Mediterranean Sea

Azaspiracids (AZAs) are marine biotoxins including a variety of analogues. Recently, novel AZAs produced by the Mediterranean dinoflagellate Azadinium dexteroporum were discovered (AZA-54, AZA-55, 3-epi-AZA-7, AZA-56, AZA-57 and AZA-58) and their biological effects have not been investigated yet. This study aimed to identify the biological responses (biomarkers) induced in mussels Mytilus galloprovincialis after the bioaccumulation of AZAs from A. dexteroporum. Organisms were fed with A. dexteroporum for 21 days and subsequently subjected to a recovery period (normal diet) of 21 days. Exposed organisms accumulated AZA-54, 3-epi-AZA-7 and AZA-55, predominantly in the digestive gland. Mussels' haemocytes showed inhibition of phagocytosis activity, modulation of the composition of haemocytic subpopulation and damage to lysosomal membranes; the digestive tissue displayed thinned tubule walls, consumption of storage lipids and accumulation of lipofuscin. Slight genotoxic damage was also observed. No clear occurrence of oxidative stress and alteration of nervous activity was detected in AZA-accumulating mussels. Most of the altered parameters returned to control levels after the recovery phase. The toxic effects detected in M. galloprovincialis demonstrate a clear biological impact of the AZAs produced by A. dexteroporum, and could be used as early indicators of contamination associated with the ingestion of seafood.

Long-term exposure of Mytilus galloprovincialis to diclofenac, Ibuprofen and Ketoprofen: Insights into bioavailability, biomarkers and transcriptomic changes

Non-steroidal anti-inflammatory drugs (NSAIDs) represent a growing concern for marine ecosystems due to their ubiquitous occurrence and documented adverse effects on non-target organisms. Despite the remarkable efforts to elucidate bioaccumulation and ecotoxicological potential under short-term conditions, limited and fragmentary information is available for chronic exposures. In this study bioavailability, molecular and cellular effects of diclofenac (DIC), ibuprofen (IBU) and ketoprofen (KET) were investigated in mussels Mytilus galloprovincialis exposed to the realistic environmental concentration of 2.5 μg/L for up to 60 days. Results indicated a significant accumulation of DIC and IBU but without a clear time-dependent trend; on the other hand, KET concentrations were always below the detection limit. Analyses of a large panel of molecular, biochemical and cellular biomarkers highlighted that all investigated NSAIDs caused alterations of immunological parameters, genotoxic effects, modulation of lipid metabolism and changes in cellular turn-over. This study provided the evidence of long-term ecotoxicological potential of NSAIDs, further unraveling the possible hazard for wild marine organisms.

Accumulation and transformation of azaspiracids in scallops (Chlamys farreri) and mussels (Mytilus galloprovincialis) fed with Azadinium poporum, and response of antioxidant enzymes

Azaspiracid (AZA) producing microalgae have been reported internationally and could potentially impact a variety of seafood. Scallops (Chlamys farreri) and mussels (Mytilus galloprovincialis) from China were fed with the AZA2 producer, Azadinium poporum, to study uptake, metabolism and oxidative stress in the shellfish. LC-MS/MS showed significant accumulation and differential metabolism of AZA2 in the scallops and mussels. In mussels AZA2 was metabolized to AZA19, with subsequent decarboxylation to AZA6. In scallops no AZA19 or AZA6 was observed, however, a novel AZA metabolite was formed that is isobaric with AZA19 ([M+H]⁺, m/z 886), but elutes at a different retention time. In addition it was noted that the scallop metabolite was stable during heating, while AZA19 has been shown to decarboxylate. Concentrations of reactive oxygen species (ROS) and activities of antioxidant enzymes were monitored. ROS levels increased slightly in the meat of scallops and mussels due to starvation in the acclimation and depuration periods, but reduced in the feeding periods with non-toxic Isochrysis galbana or toxic A. poporum. No obvious variations were found in activities for a range of antioxidant enzymes. These results provide new insights on the potential for accumulation and metabolism of AZAs in bivalve species relevant to this area of China, which is of importance considering the recent finding of AZA producing microalgae in the region.

Minireview: algal natural compounds and extracts as antifoulants

Marine biofouling is a paramount phenomenon in the marine environment and causes serious problems to maritime industries worldwide. Marine algae are known to produce a wide variety of chemical compounds with antibacterial, antifungal, antialgal, and anti-macrofouling properties, inhibiting the settlement and growth of other marine fouling organisms. Significant investigations and progress have been made in this field in the last two decades and several antifouling extracts and compounds have been isolated from micro- and macroalgae. In this minireview, we have summarized and evaluated antifouling compounds isolated and identified from macroalgae and microalgae between January 2010 and June 2016. Future directions for their commercialization through metabolic engineering and industrial scale up have been discussed. Upon comparing biogeographical regions, investigations from Southeast Asian waters were found to be rather scarce. Thus, we have also discussed the need to conduct more chemical ecology based research in relatively less explored areas with high algal biodiversity like Southeast Asia.

Influence of environmental factors on the toxin production of Ostreopsis cf. ovata during bloom events

Intense blooms of the toxic dinoflagellate Ostreopsis have been a recurrent phenomenon along several Mediterranean coasts. Blooms have been associated with noxious effects on human health and mortality of marine organisms, due to the production of palytoxin-like compounds. We analyzed the toxin concentrations throughout an O. cf. ovata bloom to highlight their relationships with environmental parameters in the Conero Riviera, northern Adriatic Sea. High temperature and balanced nutrient conditions were the optimal environmental conditions to start and sustain blooms as well as to maximize toxin production. Ostreopsis showed a gradual decrease of toxin content throughout the bloom ascribed to the occurring of the same non-optimal conditions that led to the bloom decline. Moreover, our results suggest that toxin fraction released during bloom could be higher than that released in batch culture. Results from this study pointed out that the first bloom phase is potentially the most dangerous to human health.

Blue mussels (Mytilus edulis spp.) as sentinel organisms in coastal pollution monitoring: A review

The blue mussel (Mytilus spp.) is widely used as a bioindicator for monitoring of coastal water pollution (mussel watch programs). Herein we provide a review of this study field with emphasis on: the suitability of Mytilus spp. as environmental sentinels; uptake and bioaccumulation patterns of key pollutant classes; the use of Mytilus spp. in mussel watch programs; recent trends in Norwegian mussel monitoring; environmental quality standards and background concentrations of key contaminants; pollutant effect biomarkers; confounding factors; particulate contaminants (microplastics, engineered nanomaterials); climate change; harmonization of monitoring procedures; and the use of deployed mussels (transplant caging) in pollution monitoring. Lastly, the overall state of the art of blue mussel pollution monitoring is discussed and some important issues for future research and development are highlighted.

Transcriptional and biochemical analysis of antioxidant enzymes in the mussel Mytilus galloprovincialis during experimental exposures to the toxic dinoflagellate Prorocentrum lima

The genotoxic and cytotoxic effects of Diarrhetic Shellfish Poisoning (DSP) toxins have been widely investigated in bivalve molluscs, representing the main vectors of these compounds in the Atlantic coast of Europe. DSP toxins are produced by Harmful Algal Blooms (HABs) of Dinophysis and Prorocentrum dinoflagellates, being subsequently accumulated by marine organisms and biomagnified throughout trophic webs. Yet, bivalves display increased resistance to the harmful effects of these toxins during HAB episodes. While previous reports have suggested that such resilience might be the result of an increased activity in the bivalve antioxidant system, very little is still known about the specific mechanism underlying the protective effect observed in these organisms. The present work aims to fill this gap by studying transcriptional expression levels and biochemical activities of antioxidant enzymes in different tissues the mussel Mytilus galloprovincialis during experimental exposures to DSP toxins produced by the dinoflagellate Prorocentrum lima. Results are consistent with the presence of a compensatory mechanism involving a down-regulation in the expression of specific genes encoding antioxidant enzymes [i.e., SuperOxide Dismutase (SOD) and CATalase (CAT)] which is counterbalanced by the up-regulation of other antioxidant genes such as Glutathione S-Transferase pi-1 (GST-pi) and Selenium-dependent Glutathione PeroXidase (Se-GPx), respectively. Enzymatic activity analyses mirror gene expression results, revealing high antioxidant activity levels (consistent with a protective role for the antioxidant system) along with reduced lipid peroxidation (increasing the defense against oxidative stress).

Ostreopsis fattorussoi sp. nov. (Dinophyceae), a new benthic toxic Ostreopsis species from the eastern Mediterranean Sea

The new benthic toxic dinoflagellate, Ostreopsis fattorussoi sp. nov., is described from the Eastern Mediterranean Sea, Lebanon and Cyprus coasts, and is supported by morphological and molecular data. The plate formula, Po, 3', 7″, 6c, 7s, 5‴, 2'''', is typical for the Ostreopsis genus. It differs from all other Ostreopsis species in that (i) the curved suture between plates 1' and 3' makes them approximately hexagonal, (ii) the 1' plate lies in the left half of the epitheca and is obliquely orientated leading to a characteristic shape of plate 6″. The round thecal pores are bigger than the other two Mediterranean species (O. cf. ovata and O. cf. siamensis). O. fattorussoi is among the smallest species of the genus (DV: 60.07 ± 5.63 μm, AP: 25.66 ± 2.97 μm, W: 39.81 ± 5.05 μm) along with O. ovata. Phylogenetic analyses based on the LSU and internal transcribed spacer rDNA shows that O. fattorussoi belongs to the Atlantic/Mediterranean Ostreopsis spp. clade separated from the other Ostreopsis species. Ostreopsis fattorussoi produces OVTX-a and structural isomers OVTX-d and -e, O. cf. ovata is the only other species of this genus known to produce these toxins. The Lebanese O. fattorussoi did not produce the new palytoxin-like compounds (ovatoxin-i, ovatoxin-j₁ , ovatoxin-j₂ , and ovatoxin-k) that were previously found in O. fattorussoi from Cyprus. The toxin content was in the range of 0.28-0.94 pg · cell^-1 . On the Lebanon coast, O. fattorussoi was recorded throughout the year 2015 (temperature range 18°C-31.5°C), with peaks in June and August.

Transcriptional and cellular effects of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) in experimentally exposed mussels, Mytilus galloprovincialis

The aim of the present investigation was to provide new insights on accumulation and possible adverse effects of various non-steroidal anti-inflammatory drugs (NSAIDs) in mussels, Mytilus galloprovincialis, exposed to an environmentally realistic concentration (0.5μg/L) of individual compounds, Acetaminophen (AMP), Diclofenac (DIC), Ibuprofen (IBU), Ketoprofen (KET) or Nimesulide (NIM). The measurement of drugs in mussel tissues was integrated with both functional alterations at cellular level and transcriptomic responses. Results indicated the capability of mussels to accumulate DIC and NIM, while AMP, IBU and KET were always below detection limit. A large panel of ecotoxicological biomarkers revealed the early onset of alterations induced by tested NSAIDs on immunological responses, lipid metabolism and DNA integrity. The gene transcription analysis through DNA microarrays, supported cellular biomarker results, with clear modulation of a large number of genes involved in the arachidonic acid and lipid metabolism, immune responses, cell cycle and DNA repair. The overall results indicated an ecotoxicological concern for pharmaceuticals in M. galloprovincialis, with transcriptional responses appearing as sensitive exposure biomarkers at low levels of exposure: such changes, however, are not always paralleled by corresponding functional effects, suggesting caution when interpreting observed effects in terms of perturbed cellular pathways. Fascinating similarities can also be proposed in the mode of action of NSAIDs between bivalves and vertebrate species.

Effects of the harmful dinoflagellate Ostreopsis cf. ovata on different life cycle stages of the common moon jellyfish Aurelia sp

The frequency and geographic extension of microalgae and gelatinous zooplankton blooms seem to have been increasing worldwide over recent decades. In particular, the harmful dinoflagellate Ostreopsis cf. ovata and the Schyphozoan jellyfish Aurelia sp. are two of the most frequent and long lasting species forming blooms in the Mediterranean Sea. A kind of interaction among any of their life cycle stages (i.e. planula-polyp-ephyrae vs Ostreopsis cells) can likely occur, although in this area there are no data available on the co-occurrence of these species. The aim of this study was to investigate, for the first time, the potential noxious effect of O. cf. ovata on different life stages of Aurelia sp. (polyps and ephyrae), testing several concentrations of whole algal culture. Rsults of toxicity bioassay highlighted that ephyrae, but not polyps, are affected by this harmful dinoflagellate and comparisons among other model organisms show that Aurelia sp. ephyrae are the most sensitive model organism tested so far (EC_50-24h=10.5cells/mL). These findings suggest an interesting scenario on the interaction of these two bloom forming species in the natural marine environment.

Effects of the bloom of harmful benthic dinoflagellate Ostreopsis cf. ovata on the microphytobenthos community in the northern Adriatic Sea

Composition and temporal variation of the microphytobenthos communities of the Conero Riviera (northern Adriatic Sea) were investigated in the course of an annual cycle, focusing on their relationships with blooms of the benthic dinoflagellate Ostreopsis cf. ovata. Sampling was carried out from March 2009 to March 2010 on undisturbed benthic substrata (macroalgae and pebbles). Samples for the study of microphytobenthos were collected with a monthly frequency, while those for the study of Ostreopsis bloom weekly. Benthic diatoms dominated the microphytobenthos communities for most of the annual cycle (except the summer), both in terms of abundance and biomass. In summer, cyanobacteria were dominant (54.04±9.18 and 24.29±11.11% of total abundance and biomass, respectively), while benthic dinoflagellates were an important component of the community in terms of biomass only at the peak of the Ostreopsis bloom in late summer (up to 91% of the total biomass). Among diatoms, the most abundant forms throughout the year were motile species (77.5±3.71% of the population), while erect diatoms formed the majority of the biomass in winter and spring (48.66±16.66 and 48.05±5.56% of total population, respectively). Diatoms were mainly affected by DIN availability, while the patterns of biomass of O. cf. ovata and cyanobacteria were related to salinity and temperature. The biomass of Ostreopsis was also affected by the availability of phosphorus. The results of this study suggest that the proliferation of Ostreopsis affected the structure of the benthic diatom community: motile diatoms were significantly more abundant during the Ostreopsis bloom peak than during the rest of summer, probably because they benefited from the abundant mucilaginous mat covering the benthic substrata. In the course of the O. cf. ovata bloom the diversity of the microphytobenthos was significantly lower than during the rest of the year, suggesting an influence of both the shading produced by the mucous mat and allelopathic compounds possibly produced by O. cf. ovata.

Phylogenetic structure of bacterial assemblages co-occurring with Ostreopsis cf. ovata bloom

Extensive blooms of the toxic epiphytic/benthic dinoflagellate Ostreopsis cf. ovata are being reported with increasing frequency and spatial distribution in temperate coastal regions including the Mediterranean. These blooms are of human and environmental health concern due to the production of isobaric palytoxin and a wide range of ovatoxins by Ostreopsis cf. ovata. Bacterial-microalgal interactions are important regulators in algal bloom dynamics and potentially toxin dynamics. This study investigated the bacterial assemblages co-occurring with O. cf. ovata (OA) and from ambient seawaters (SW) during the early and peak phases of bloom development in NW Adriatic Sea. Fractions of the bacterial assemblages co-occurring with O. cf. ovata (OA) and more closely associated to the mucilage layer (LA) embedding O. cf. ovata cells were also reported. In total, 14 bacterial phyla were detected by targeted 454 pyrosequencing of the 16S rRNA gene. The dominant bacterial phyla in the OA assemblages were Proteobacteria and Bacteroidetes; while at the class level, Alphaproteobacteria were the most abundant (83 and 66%, relative abundance, early and peak bloom phases), followed by Flavobacteria (7 and 19%, early and peak phases). Actinobacteria and Cyanobacteria were of minor importance (<5% of the relative bacterial abundance each). Gammaproteobacteria showed a notably presence in OA assemblage only at the early phase of the bloom (genus Haliea, 13%). The Alphaproteobacteria were predominately composed by the genera Ruegeria, Jannaschia and Erythrobacter which represented about half of the total phylotypes' contribution of OA at both early and peak phases of the O. cf. ovata bloom, suggesting interactions between this consortium and the microalga. Moreover, the highest contribution of Ruegeria (30% of the total phylotypes) was observed at the early phase of the bloom in LA assemblage. Microbial assemblages associated with the ambient seawaters while being also dominated by Alphaproteobacteria and Flavobacteria were partially distinct from those associated with O. cf. ovata due to the presence of genera almost not retrieved in the latter assemblages.

Effects of N and P availability on carbon allocation in the toxic dinoflagellate Ostreopsis cf. ovata

Blooms of the toxic dinoflagellate Ostreopsis cf. ovata are usually associated with shallow and calm coastal waters, characterized by low nutrient concentrations. The algal cells typically cover the benthic substrates, such as the macroalgal and invertebrate communities and rocks, forming a mucilaginous film. Data reported on O. cf. ovata toxin production observed under both field and culture conditions show high variability in terms of toxic profile and cellular content; little is known about the environmental and physiological aspects which regulate the toxin dynamics. In this study, O. cf. ovata physiology was investigated using batch cultures supplied with nutrient concentrations similar to those found in the Adriatic Sea during the recurrent blooms and the observed cellular dynamics were compared with those found in a culture grown under optimal conditions, used as a reference. Data on the cellular C, N and P content during the growth highlighted a possible important role of the cellular nutritional status in regulating the toxin production that resulted to be promoted under specific intervals of the C:N and C:P ratios. The variable toxicity found for O. cf. ovata in various geographic areas could be related to the different in situ prevalent environmental conditions (e.g., nutrient concentrations) which affect the cellular elemental composition and carbon allocation. The obtained results strongly suggest that in the environment toxin production is steadily sustained by a low and constant nutrient supply, able to maintain appropriate cellular C:N (>12) or C:P (>170) ratios for a long period. These results explain to some extent the variability in toxicity and growth dynamics observed in blooms occurring in the different coastal areas.

Antioxidant responses of triangle sail mussel Hyriopsis cumingii exposed to harmful algae Microcystis aeruginosa and hypoxia

Bloom forming algae and hypoxia are considered to be two main co-occurred stressors associated with eutrophication. The aim of this study was to evaluate the interactive effects of harmful algae Microcystis aeruginosa and hypoxia on an ecologically important mussel species inhabiting lakes and reservoirs, the triangle sail mussel Hyriopsis cumingii, which is generally considered as a bio-management tool for eutrophication. A set of antioxidant enzymes involved in immune defence mechanisms and detoxification processes, i.e. glutathione-S-transferases (GST), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), lysozyme (LZM) in mussel haemolymph were analyzed during 14days exposure along with 7days depuration duration period. GST, GSH, SOD, GPX and LZM were elevated by toxic M. aeruginosa exposure, while CAT activities were inhibited by such exposure. Hypoxia influenced the immune mechanisms through the activation of GSH and GPX, and the inhibition of SOD, CAT, and LZM activities. Meanwhile, some interactive effects of M. aeruginosa, hypoxia and time were observed. Independently of the presence or absence of hypoxia, toxic algal exposure generally increased the five tested enzyme activities of haemolymph, except CAT. Although half of microcystin could be eliminated after 7days depuration, toxic M. aeruginosa or hypoxia exposure history showed some latent effects on most parameters. These results revealed that toxic algae play an important role on haemolymph parameters alterations and its toxic effects could be affected by hypoxia. Although the microcystin depuration rate of H. cumingii is quick, toxic M. aeruginosa and/or hypoxia exposure history influenced its immunological mechanism recovery.

Monitoring toxic Ostreopsis cf. ovata in recreational waters using a qPCR based assay

Ostreopsis sp. is a toxic marine benthic dinoflagellate that causes high biomass blooms, posing a threat to human health, marine biota and aquaculture activities, and negatively impacting coastal seawater quality. Species-specific identification and enumeration is fundamental because it can allow the implementation of all the necessary preventive measures to properly manage Ostreopsis spp. bloom events in recreational waters and aquaculture farms. The aim of this study was to apply a rapid and sensitive qPCR method to quantify Ostreopsis cf. ovata abundance in environmental samples collected from Mediterranean coastal sites and to develop site-specific environmental standard curves. Similar PCR efficiencies of plasmid and environmental standard curves allowed us to estimate the LSU rDNA copy number per cell. Moreover, we assessed the effectiveness of mitochondrial COI and cob genes as alternative molecular markers to ribosomal genes in qPCR assays for Ostreopsis spp. quantification.

An exploratory investigation of various modes of action and potential adverse outcomes of fluoxetine in marine mussels

The present study investigated possible adverse outcome pathways (AOPs) of the antidepressant fluoxetine (FX) in the marine mussel Mytilus galloprovincialis. An evaluation of molecular endpoints involved in modes of action (MOAs) of FX and biomarkers for sub-lethal toxicity were explored in mussels after a 7-day administration of nominal FX concentrations encompassing a range of environmentally relevant values (0.03-300ng/L). FX bioaccumulated in mussel tissues after treatment with 30 and 300ng/L FX, resulting in bioconcentration factor (BCF) values ranging from 200 to 800, which were higher than expected based solely on hydrophobic partitioning models. Because FX acts as a selective serotonin (5-HT) re-uptake inhibitor increasing serotonergic neurotransmission at mammalian synapses, cell signaling alterations triggered by 5-HT receptor occupations were assessed. cAMP levels and PKA activities were decreased in digestive gland and mantle/gonads of FX-treated mussels, consistent with an increased occupation of 5-HT1 receptors negatively coupled to the cAMP/PKA pathway. mRNA levels of a ABCB gene encoding the P-glycoprotein were also significantly down-regulated. This membrane transporter acts in detoxification towards xenobiotics and in altering pharmacokinetics of antidepressants; moreover, it is under a cAMP/PKA transcriptional regulation in mussels. Potential stress effects of FX were investigated using a battery of biomarkers for mussel health status that included lysosomal parameters, antioxidant enzyme activities, lipid peroxidation, and acetylcholinesterase activity. FX reduced the health status of mussels and induced lysosomal alterations, as suggested by reduction of lysosomal membrane stability in haemocytes and by lysosomal accumulation of neutral lipids in digestive gland. No clear antioxidant responses to FX were detected in digestive gland, while gills displayed significant increases of catalase and glutathione-s-transferase activities and a significant decrease of acetylcholinesterase activity. Though AOPs associated with mammalian therapeutic MOAs remain important during assessments of pharmaceutical hazards in the environment, this study highlights the importance of considering additional MOAs and AOPs for FX, particularly in marine mussels.

A multidisciplinary weight of evidence approach for environmental risk assessment at the Costa Concordia wreck: Integrative indices from Mussel Watch

A complex framework of chemical, biological and oceanographic activities was immediately activated after the Costa Concordia shipwreck, to assess possible contamination events and the environmental impact during both emergency and wreck removal operations. In the present paper, we describe the results obtained with caged mussels, Mytilus galloprovincialis, chosen as bioindicator organisms to detect variations of bioavailability and the early onset of molecular and cellular effects (biomarkers). Seven translocation experiments were carried out during the first year from the incident, with organisms deployed at 2 depths in 3 different sites. After 4-6 weeks, tissue concentrations were measured for the main classes of potentially released chemicals (trace metals, polycyclic aromatic hydrocarbons, volatile and aliphatic hydrocarbons, polychlorinated biphenyls, halogenated pesticides, organotin compounds, brominated flame retardants, anionic surfactants); a wide battery of biomarkers covered responses indicative of exposure, detoxification, oxidative stress, cell damage and genotoxic effects. Results excluded serious contamination events or a consistent increase of environmental pollution although some episodic spills with reversible effects were detected. Data were elaborated within a quantitative weight of evidence (WOE) model which provided synthetic hazard indices for each typology of data, before their overall integration in an environmental risk index, which generally ranged from slight to moderate. The proposed WOE model was confirmed a useful tool to summarize large datasets of complex data in integrative indices, and to simplify the interpretation for stakeholders and decision makers, thus supporting a more comprehensive process of "site-oriented" management decisions.

Could molecular effects of Caulerpa racemosa metabolites modulate the impact on fish populations of Diplodus sargus?

The green alga Caulerpa racemosa is a non-native, invasive species in the Mediterranean, and an important stressor for several native organisms. The algal capacity to produce secondary metabolites has been suggested to modulate success of the C. racemosa invasion, although many of potentially involved biological pathways still remain unexplored. In this respect, the aim of the present study was to investigate some molecular and cellular effects in the white seabream Diplodus sargus, an ecologically key species, which included the alien C. racemosa in its diet. Organisms were sampled in 2 seasonal periods from 3 locations of Southern Italy, each characterized by different levels of algal abundance. The level of caulerpin, one of the main secondary algal metabolites, in fish tissues has been used as an indicator of the trophic exposure to the seaweed and related with molecular and cellular responses. Chemical analyses indicated that fish from invaded sites can accumulate caulerpin, with liver concentrations ranging from a few up to hundreds of μg/g. Biomarkers analyses revealed only limited alterations of the main antioxidant defences, such as glutathione reductase and levels of glutathione; on the other hand, increased enzymatic activities of cytochrome P450, glutathione S-transferases and acyl CoA oxidase, as well as enhanced gene transcription for peroxisome proliferator-activated receptor alpha, cytochrome P4501A and vitellogenin 1 were observed in fish more exposed to C. racemosa as indicated by liver concentrations of caulerpin higher than 50 μg/g. Despite a direct molecular relationship with this algal metabolite could not be established, our results suggest that a C. racemosa enriched diet can modulate biotransformation and fatty acids metabolism of D. sargus. Assessing whether similar effects represent short- or long-term effects will be of crucial importance to understand consequences on the general health status and reproductive performance of exposed key fish species in the Mediterranean region.

Cephalopods as vectors of harmful algal bloom toxins in marine food webs

Here we summarize the current knowledge on the transfer and accumulation of harmful algal bloom (HAB)-related toxins in cephalopods (octopods, cuttlefishes and squids). These mollusks have been reported to accumulate several HAB-toxins, namely domoic acid (DA, and its isomers), saxitoxin (and its derivatives) and palytoxin (and palytoxin-like compounds) and, therefore, act as HAB-toxin vectors in marine food webs. Coastal octopods and cuttlefishes store considerably high levels of DA (amnesic shellfish toxin) in several tissues, but mainly in the digestive gland (DG)--the primary site of digestive absorption and intracellular digestion. Studies on the sub-cellular partitioning of DA in the soluble and insoluble fractions showed that nearly all DA (92.6%) is found in the cytosol. This favors the trophic transfer of the toxins since cytosolic substances can be absorbed by predators with greater efficiency. The available information on the accumulation and tissue distribution of DA in squids (e.g., in stranded Humboldt squids, Dosidicus gigas) is scarcer than in other cephalopod groups. Regarding paralytic shellfish toxins (PSTs), these organisms accumulate them at the greatest extent in DG >> kidneys > stomach > branchial hearts > posterior salivary glands > gills. Palytoxins are among the most toxic molecules identified and stranded octopods revealed high contamination levels, with ovatoxin (a palytoxin analogue) reaching 971 μg kg⁻¹ and palytoxin reaching 115 μg kg⁻¹ (the regulatory limit for PlTXs is 30 μg kg⁻¹ in shellfish). Although the impacts of HAB-toxins in cephalopod physiology are not as well understood as in fish species, similar effects are expected since they possess a complex nervous system and highly developed brain comparable to that of the vertebrates. Compared to bivalves, cephalopods represent a lower risk of shellfish poisoning in humans, since they are usually consumed eviscerated, with exception of traditional dishes from the Mediterranean area.

Effects of harmful dinoflagellate Ostreopsis cf. ovata exposure on immunological, histological and oxidative responses of mussels Mytilus galloprovincialis

In the last decade massive blooms of the Ostreopsis cf. ovata have occurred in the Mediterranean basin, posing great concern to both environmental and human health. Biotoxicological and chemical studies demonstrated that O. cf. ovata produces palytoxin and ovatoxins; besides direct respiratory effects on humans due to inhalation of marine toxic aerosols, O. cf. ovata blooms can cause adverse effects on benthic invertebrates. The main aim of this study was to highlight the role of immunological, cellular and oxidative mechanisms in modulating the toxicity induced by O. cf. ovata in mussels Mytilus galloprovincialis. Organisms were exposed in laboratory condition to O. cf. ovata and analysed after 7 and 14 days of exposure. Obtained results demonstrated a clear involvement of the immune system with a significant decrement of granulocytes respect to the hyalinocytes type cells, a diminished phagocytosis activity and a reduced lysosomal membrane stability in haemocytes, after both 7 and 14 days of exposure. Histological analyses showed a decrease of the digestive gland wall thickness, dilatation of the tubules, haemocytes infiltration into the digestive gland and a decrement of neutral lipid levels in exposed mussels; similar results suggest a possible inhibition of the feeding activity, with a consequent induction of authophagic phenomena and utilization of stored reserve products such as neutral lipids. Antioxidant parameters revealed a limited role of O. cf. ovata to induce oxidative stress in mussels exposed under laboratory conditions excepting for a certain increase of catalase, glutathione reductase and glutathione peroxidases activities, and a significantly higher capability to neutralize peroxyl radicals in mussels exposed for 14 days. Although the obtained results suggest a non-specific response of mussels to the O. cf. ovata exposure, observed effects on the general health status of exposed mussels should be adequately considered when assessing the ecological relevance of these algal blooms.