Seasonal variations of phytoplankton community in relation to environmental factors in a protected meso-oligotrophic southern Mediterranean marine ecosystem (Mellah lagoon, Algeria) with an emphasis of HAB species.

The spatial and temporal variation of phytoplankton communities including HAB species in relation to the environmental characteristics was investigated in the protected meso-oligotrophic Mellah lagoon located in the South Western Mediterranean. During 2016, a biweekly monitoring of phytoplankton assemblages and the main abiotic factors were realized at three representative stations. Taxonomic composition, abundance, and diversity index were determined. In total, 227 phytoplankton species (160 diatoms and 53 dinoflagellates) were inventoried. There was a clear dominance of diatoms (62.9%) compared with dinoflagellates (36.8%). Diatoms dominated in spring and dinoflagellates developed in summer and early autumn in Mellah showing a marked seasonal trend. Data showed that the dynamic of the phytoplankton taxa evolving in the lagoon was mainly driven by temperature and salinity. For the first time, a number of potentially toxic species have been identified, including 2 diatoms (Pseudo-nitzschia group delicatissima, Pseudo-nitzschia group seriata) and 5 dinoflagellates (Alexandrium minutum, Alexandrium tamarense/catenella, Dinophysis acuminata, Dinophysis sacculus, Prorocentrum lima). These harmful species could threat the functioning of the Mellah lagoon and human health and require the establishment of a monitoring network. Finally, our study suggests that the observed decrease of the phytoplankton diversity between 2001 and 2016 could result from the reduction in water exchanges between the lagoon and the adjacent coast following the gradual clogging of the channel.

Early chemical and ecotoxicological responses of the Varano lagoon (SE Italy) to a flood event.

The effects on coastal lagoons of floods resulting from intense rainfall need to be assessed using a multidisciplinary approach, able to describe in real time the occurrence of changes in sediment quality, anticipating risk situations. In the present study the effectiveness as pre-screening tool of the MOT-test, an innovative bioassay that uses sperm motility as endpoint, has been evaluated; its response has been compared with the sediment chemical characterization, in order to determine the effects of a flood event occurred in the Varano lagoon, a poorly anthropized Mediterranean coastal lagoon. The MOT-test effect percentages ranged from 10% to 30%, fully reflecting data from chemical analyses. Organic pollutants showed concentrations always below the critical levels. The highest metal values were found in the south-eastern area; however, only for few metals (mainly Cd), and in few sites, they reached the limits defined by the sediment quality guidelines; consistently, these sites are located in the area where a higher stressors' impact was expected and the highest MOT-test effect percentages were recorded. In conclusion, even if results exclude the occurrence of serious contamination events as a consequence of the flood, the runoff resulting from the intense rainfall event has caused a pollutant load in the lagoon, consistent with the localization of the main anthropogenic activities in the catchment area. Moreover, preliminary data indicate the validity of the approach adopted for the post-flood quality assessment, proving the usefulness of the MOT-test as early-screening tool in the case of extreme events.

Trematode maturation patterns in a migratory snail host: What happens during upshore residency in a Mediterranean lagoon?

Maturation of trematode larval stages is expected to be temporally and spatially adapted to maximise the encounter with the adequate downstream host, i.e. the host, which will be infected by this parasite stage. Since studies on intramolluscan parasite maturation are scarce but important in the context of parasite transmission, the larval development inside sporocysts was monitored during upshore residency of the snail host Gibbula adansonii (Trochidae), i.e., from March to May (2011 and 2013), when these snails temporarily reside in the intertidal habitat of a Western Mediterranean lagoon (40° 37' 35″ N, 0° 44' 31″ E, Spain). Data on the relative quantity of different maturation stages of Cainocreadium labracis and Macvicaria obovata (Opecoelidae) parasitising the G. adansonii as well as on snail and sporocyst size were explored using linear models and linear mixed models. The effect of the trematodes on snail growth was shown to be species-specific, with snail and sporocyst size acting as proxies of the reproductive capacity of M. obovata but not that of C. labracis. The number of cercarial embryos and germinal balls did not show monthly variation in either parasite species, but a higher number of mature stages and the highest maturity index was found in April. Hence, during the snail's limited spawning-related presence in the upshore waters of the lagoon, continuous production and output of infectious cercariae was observed, which indicates a link between larval maturation and snail migration. The synchronization of snails, mature parasite transmission stages and downstream hosts in time and space guarantees a successful completion of the life cycle.

Seasonal variability of trace elements bioaccumulation in Pacific Oysters (Crassostrea gigas) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy).

BACKGROUND: Metals pollution is a worldwide environmental issue due to their persistence in the ecosystems, non-degradability, and bioaccumulation in marine biota. Pacific Oysters (Crassostrea gigas) are highly nutritious bivalve representing an important dietary constituent but may accumulate metals through feeding on suspended sediments from surrounding water, then represent a suitable tool for biomonitoring. MATERIALS AND METHODS: The occurrence of trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Se, Sn, V, Zn) was investigated in Pacific Oysters (Cassostrea gigas) collected from Calich Lagoon in each season of 2019. Samples were homogenized and subjected to microwave acid digestion before being analyzed by inductively coupled plasma-mass spectrometer (ICP-MS). RESULTS: The results showed a significant seasonal variation for temperature, dissolved oxygen, chlorophyll, and pH. Moreover, high significant seasonal variation in concentrations of Cd, Mn, Ni, and V was recorded. The highest values were found for Fe (128 mg kg⁻1 w.w.), and Al (112 mg kg⁻1 w.w.) in October, for Zn (113 mg kg⁻1 w.w.) in March and May. CONCLUSIONS: Pacific Oysters were confirmed as suitable bioindicators of the health status of coastal lagoons; trace elements concentrations were highly affected by season of collection, and according to literature the highest values were recorded in autumn and summer. The EU legal limits for Cd and Pb were not exceeded, then the farmed oysters were safe to consumers.

Integrating culture-based and molecular methods provides an improved assessment of microbial quality in a coastal lagoon.

Faecal pollution in aquatic environments is a worldwide public health concern, yet the reliability and comprehensiveness of the methods used to assess faecal contamination are still debated. We compared three approaches, namely a culture-based method to enumerate Faecal Indicator Bacteria (FIB), a FIB-targeting qPCR assay, and High-Throughput Sequencing (HTS) to detect faeces- and sewage-associated taxa in water and sediment samples of an impacted model lagoon and its adjacent sea across one year. Despite at different levels, all approaches agreed in showing a higher contamination in the lagoon than in the sea, and higher in sediments than water. FIB significantly correlated when considering separately sediment and water, and when using both cultivation and qPCR. Similarly, FIB correlated between cultivation and qPCR, but qPCR provided consistently higher estimates of FIB. Faeces-associated bacteria positively correlated with cultivated FIB in both compartments, whereas sewage-associated bacteria did only in water. Considering their benefits and limitations, we conclude that, in our study site, improved quali-quantitative information on contamination is provided when at least two approaches are combined (e.g., cultivation and qPCR or HTS data). Our results provide insights to move beyond the use of FIB to improve faecal pollution management in aquatic environments and to incorporate HTS analysis into routine monitoring.

Multiple approach for assessing lagoon environmental status based on water bodies quality indices and microplastics accumulation.

Lagoon environments, like all the marine-coastal areas, offer a wide variety of ecosystem services, but at the same time are affected by pressing human activities that lead to deterioration of the environmental quality, loss of biodiversity, habitat destruction and pollution. Since the well-being of population and local economy depend on the environmental status of these ecosystems, it is essential to adopt long-term management tools to achieve the Good Environmental Status sensu European Marine Strategy Framework Directive and Water Framework Directive. A Nature 2000 site (Lesina lagoon, south Italy) was assessed within a project aimed at protecting and restoring biodiversity and lagoon habitat through integrated monitoring, suitable management, and good practices. Here we provide an assessment of the lagoon integrity based on a multi-metrics approach, highlighting match/mismatch among environmental quality indicators and microplastics (MP) pollution. Some environmental quality indices based on ecosystem components as vegetation, macroinvertebrates and water trophic variables were applied together with an accurate evaluation of MPs abundance, distribution, and composition to assess the ecological status of Lesina lagoon before and after cleaning actions with litter removal. Overall, all the ecological descriptors outlined a clear lagoon spatial gradient, with a western saltier and organic-enriched area characterized by the absence of vegetation, macrozoobenthos with lower diversity and richness and high MPs occurrence. The focus on macrozoobenthos, considered as a key component of the lagoon ecosystem, identified much more sites in "poor" status than the other indicators here considered. Moreover, it was found a negative relationship between the Multivariate Marine Biotic Index and MPs items in sediment, suggesting that MP pollution has a negative impact on macrobenthic fauna, concurring to the deterioration of the benthic ecological status.

Determination of phytoplankton in water samples, algal biotoxins, microbiological parameters and microplastics in Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy).

The aims of this paper were to collect and analyse preliminary data of phytoplankton in the water, biotoxins, Escherichia coli, Salmonella spp., Vibrio spp. and microplastic eventually present in farmed mussels, and to acquire information about the production capability from an experimental pilot farm of the Calich Lagoon. Two sampling sessions were carried out, in February and in May 2019, also monitoring the water condition (pH, temperature, salinity, dissolved oxygen, chlorophyll a). No potentially toxic algae were detected, and moreover no biotoxins (Paralytic Shellfish Poison, Diarrheic Shellfish Poison, Amnesic Shellfish Poison) were found in mussels. E.coli was present with the highest concentration in February (16000 MPN/100g e.p.). Salmonella and Vibrio spp. have not been detected. Almost a microplastic per grams was found, mainly fiber of different colours. Further studies, carried out for several months, will allow to better understand the possible problems related to the production of mussels in a lagoon not yet classified as a shellfish production area.

Occurrence of trace elements in Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy).

The present study aimed to determine trace elements in Mediterranean mussels (Mytilus galloprovincialis) from an experimental pilot farm of the Calich Lagoon, a typical Sardinian brackish area (Italy). Two sampling sessions were scheduled in February and May 2019 and the occurrence of 24 metals (Hg, Ag, Al, As, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sn, Ti, V, Zn) in bivalves was considered. Environmental conditions of water (temperature, salinity, pH, dissolved oxygen, and chlorophyll a) were also measured in situ. A high significant (P<0.001) difference was reported for temperature, pH, and dissolved oxygen. Our results showed a significant sessional variation of Mo (P<0.001); Cd, V (P<0.01); Ni, Pb and Co (P<0.05) in examined M. galloprovincialis samples; as all values were higher in February than those for May session samples, meanwhile the highest levels were reported for Mg (mean±s.d. 1151±263 mg kg-1 wet weight), Al (mean±s.d. 341±192 mg kg-1 w.w.), and Fe (mean±s.d. 212 ±75 mg kg-1 w.w.) in February samples. The European Union uppermost values (EC Reg. 1881/2006) for Cd, Hg, and Pb were never overpassed. The results confirmed the role of M. galloprovincialis as one of the most appropriate biological indexes to track the presence of trace elements in brackish environments. It could be concluded that the current ecology of the Calich Lagoon suggests that compatibly with the transitional ecosystem, the classification as a bivalves' production area and the implementation of extensive shellfish farming can improve its production capacities. The knowledge of the lagoon ecology is an essential tool for its sustainable exploitation, preserving biodiversity, and mitigating the effects of anthropogenic activities on public health.

Occurrence of the protozoan parasites Toxoplasma gondii and Cyclospora cayetanensis in the invasive Atlantic blue crab Callinectes sapidus from the Lesina Lagoon (SE Italy).

The occurrence of the protozoan parasites Toxoplasma gondii and Cyclospora cayetanensis was molecularly investigated in the hemolymph, gills, stomach, hepatopancreas and gonads of the eleven invasive Atlantic blue crab Callinectes sapidus from the Lesina Lagoon (Mediterranean Sea). Out of 11 blue crabs, 6 (54.5%) and 4 (36.4%) were found positive to T. gondii and C. cayetanenis, respectively; parasites were found only in the six females analysed, while the remaining five males resulted negative. Moreover, out of 55 tissues samples, 7 (12.7%) and 8 (14.5%) were positive to T. gondii and C. cayetanensis, respectively with hemolymph and gills being the most infected tissues. This is the first report of the presence of protozoan pathogens in wild crab species collected from a Mediterranean lagoon. The present results may provide a baseline reference on microbial infection in the species for invaded Mediterranean waters, and on the potential health risks related with its consumption if eaten raw.

Bacterial and Viral Investigations Combined with Determination of Phytoplankton and Algal Biotoxins in Mussels and Water from a Mediterranean Coastal Lagoon (Sardinia, Italy).

Calich Lagoon is a Mediterranean coastal lagoon located along the northwestern coast of Sardinia (Italy). The connection to marine and fresh water determines the high productivity of this coastal lagoon. Despite its great potential and the presence of natural beds of bivalve mollusks (Mytilus galloprovincialis), the lagoon has not yet been classified for shellfish production. In this study, through a multidisciplinary approach, the presence of several bacterial pathogens (Escherichia coli, Salmonella spp., and Vibrio spp.) and viral pathogens (hepatitis A virus and norovirus genogroups I and II) was evaluated from March 2017 to February 2018. In addition, phytoplankton composition in lagoon waters and associated algal biotoxins (paralytic and diarrhetic shellfish poisoning) in mussels were also monitored. The aim of this study was to provide useful data to improve knowledge about their seasonal presence and to assess the potential risk for public health, as well as to provide input for future conservation and management strategies. In mussels, Salmonella spp. were found in spring, along with E. coli, but Salmonella spp. were not found in autumn or winter, even though E. coli was detected in these seasons. Vibrio parahaemolyticus was found in autumn and winter, but not in spring. Norovirus genogroups I and II were found in winter samples. None of the bacteria were found in summer. Algal biotoxins have never been detected in mussel samples. Among potentially harmful phytoplankton, only Pseudo-nitzschia spp. were present, mainly in summer. The results showed that a possible bacterial and viral contamination, together with the presence of potentially toxic microalgae, is a real problem. Therefore, the development of natural resource management strategies is necessary to ensure the good quality of waters and guarantee the protection of consumers.

How useful are geochemical and mineralogical indicators in assessing trace metal contamination and bioavailability in a post-restoration Mediterranean lagoon?

Tunis's Lake North (LNT), located on the Mediterranean Sea, and Tunisia's most important lagoon due to its economic value and its strategic position within the city, has recently undergone a vast sanitation project. To study the lagoon's level of metal pollution, three sediment cores were taken and the sediments were analyzed for trace and major elements, acid volatile sulfides (AVS), total organic carbon (TOC), and minerals. Results showed that TOC concentrations (0.2-3.1%) decreased following the lagoon's restoration. In addition, in comparison to historical data, concentrations of Cu (16-69.5 µg g-1), Zn (60.6-191.4 µg g-1), and Pb (13-100.9 µg g-1) also decreased. Enrichment factor calculation with respect to the crust and local background showed that the sediment had long been contaminated by human pollution and especially by Pb, Zn, and Cu. The AVS to simultaneously extracted metal (SEM) ratio revealed values generally less than 1 indicating no sediment toxicity risks. Statistics revealed a detrital origin for certain metals and a diagenetic origin for FeS2 and carbonate minerals.

Assessing ultraphytoplankton and heterotrophic prokaryote composition by flow cytometry in a Mediterranean lagoon.

In the eutrophic Ghar El Melh Lagoon (GML, Tunisia), the distribution of heterotrophic prokaryotes, pico- and nanophytoplankton was studied at five stations in November 2012 at the single cell level, along with environmental factors. Flow cytometry analysis of ultraplankton (<10 µm) resolved (i) two heterotrophic prokaryote groups, low and high nucleic acid contents (LNA and HNA, respectively), and (ii) eight to nine ultraphytoplankton groups (cryptophyte-like cells, two nanoeukaryote subgroups, two picoeukaryote subgroups and three Synechococcus-like cells subgroups). Prochlorococcus was not detected. According to redundancy analysis (RDA), a significant difference was found in the distribution of the ultraplankton between stations (F = 2.61, p < 0.05); maximum proliferations of heterotrophic prokaryotes were observed in the inner parts of the lagoon at stations 3, 4 and 5 affected by urban, agricultural and industrial discharges. Ultraphytoplankton concentrations were the highest near the outlet of the lagoon at stations 1 and 2 influenced by freshwater outflow and oligotrophic Mediterranean water inflow, respectively. At station 1, the large ultraphytoplankton concentration derives from the high abundance of cryptophyte-like cells favoured by the freshwater outflow whereas at station 2, the input of oligotrophic Mediterranean water enhanced the abundance of Synechococcus and picoeukaryotes at the expense of nanoeukaryotes. Two trophic regimes were thus differentiated in GML.

Distribution of resting cysts of the potentially toxic dinoflagellate Alexandrium pseudogonyaulax in recently-deposited sediment within Bizerte Lagoon (Mediterranean coast, Tunisia).

This study investigated the spatial distribution of Alexandrium pseudogonyaulax resting cysts in recently-deposited sediment of Bizerte lagoon (South-Western Mediterranean, Tunisia). This lagoon is the subject of many anthropogenic impacts, such as holding important fishing and aquaculture activities. A. pseudogonyaulax has been shown to produce Goniodomin A, which is a biologically-active compound. We showed that this dinoflagellate produces two types of resting cysts, which could be distinguished by the presence or the absence of a paratabulate wall. The average cyst density across the whole lagoon was rather high, reaching 639 cysts g(-1) of dry sediment (DS). Cyst densities varied widely among the sampled stations, with the highest density of 1685 cyst g(-1)DS being recorded at station 51 near a mussel farm. With respect to sediment characteristics, the highest cyst densities were found within silty sediments with high water content values. The distribution of A. pseudongoyaulax cysts in Bizerte lagoon appears to be related to hydrodynamic factors.