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Along some Mediterranean coastal areas and other world regions, nutrient and chlorophyll concentrations often show gradient increases of up to one order of magnitude perpendicular to the coast. This nearshore stripe, extending a few hundred meters from the coast, is enriched by submarine groundwater discharges (SGD) containing elevated nutrient concentrations that may eventually sustain high biomass phytoplankton blooms. During a survey carried out in the summer of 2018, we examined the short-term (hours) variability of the phytoplankton biomass (measured as chlorophyll; Chl) in response to environmental changes associated with SGD and wind forcing in the nearshore waters of Palma Beach (Mediterranean Sea). Continuous CTD records revealed a general salinity decline indicative of SGD along the shoreline. Large and pulsed salinity fluctuations (i.e. 2-3 psu variations, 1-4 h) were observed each day that were consistent with offshore advection episodes of the lower salinity water retained in the nearshore (peak crosshore velocity 5-6 cm s -1 ). Chl near the shoreline was markedly higher than offshore (3.55 ± 1.29 and 0.68 ± 0.27 mg m -3 respectively) but recurrently fluctuated in the afternoon to up to >7 mg m -3 . Primary production estimations showed that despite the higher production in the nearshore (50.29 ± 10.98 μmol O 2 L -1 d -1 , 4-fold offshore values) productivity per unit chlorophyll did not significantly vary (p > 0.01) therefore suggesting that, at this time scales, high biomass episodes in the nearshore are driven by an accumulation mechanism. Statistical analysis (CCA) demonstrates that Chl variability is largely explained (93 %) by variations in wind and current velocity. Our results provide evidence that the dynamics of this nearshore environment are modulated by the interplay between the shoreward wind-induced flow and the offshore directed density flow. This mechanism could explain the occurrence and episodic nature of high biomass blooms in the nearshore, as well as be an important factor influencing the microbial community structure at the coastal zone., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Thecadinium is a morphologically heterogenous marine benthic genus. Its polyphyly has been discussed. After redefinition of the sensu stricto genus, sensu lato taxa now need reclassification. Heterotrophic, morphologically closely related species were studied in detail. Molecular phylogenetic data for three of the four known species (T. ornatum, T. acanthium, T. ovatum) and new morphological data were obtained, leading to an emended thecal plate pattern, including the presence of an apical pore complex and an additional hypothecal plate. The results confirm the close relationship of the species and justify the description of Carinadinium gen. nov., characterized by the tabulation APC 3/4' 1/0a 6″ 6c 5s 5‴ 2'‴, an epithecal plate of special morphology, an apical flange, a ventral pore, antapical appendages, a descending cingulum and lateral cell flattening. The genus can be separated into two sub-clades, one with a third precingular 'dimple'-plate, four apical and no anterior intercalary plates and the other with a 'multi-pimple'-plate as third precingular or its homolog plate, three apical and one anterior intercalary plate. Carinadinium is phylogenetically related to the planktonic genera Protoceratium, Pentaplacodinium, and Ceratocorys (family Protoceratiaceae), and clearly belongs into the order Gonyaulacales, but with uncertain family affiliation., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

Several planktonic dinoflagellates can produce lipophilic phycotoxins that represent a significant threat to public health as well as to shellfish and fish farming. Poisoning related to some of these toxins is categorised as diarrhetic shellfish poisoning. We analysed 975 shellfish samples from Tortoli in the central-eastern region of Sardinia (Italy) from January 2016 to March 2020, to investigate the prevalence of different lipophilic marine biotoxins in mollusc bivalves. The results highlighted the predominant presence of toxins belonging to the okadaic acid group in all samples with toxin concentrations exceeding legal limits, and revealed the new occurrence of pectenotoxins in oysters and clams with a winter seasonality in recent years. The origin of shellfish toxicity was associated with the same Dinophysis species, mainly D. acuminata . Based on both these results and other precedents, monitoring and recording systems are strongly recommended., Competing Interests: Conflict of interest: The authors declare no conflict of interest., (©Copyright: the Author(s).)

A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, and stated that: "The polyphyly [sic] of Alexandrium is solved with the split into four genera". However, these reintroduced taxa were not based on monophyletic groups. Therefore this work, if accepted, would result in replacing a single paraphyletic taxon with several non-monophyletic ones. The morphological data presented for genus characterization also do not convincingly support taxa delimitations. The combination of weak molecular phylogenetics and the lack of diagnostic traits (i.e., autapomorphies) render the applicability of the concept of limited use. The proposal to split the genus Alexandrium on the basis of our current knowledge is rejected herein. The aim here is not to present an alternative analysis and revision, but to maintain Alexandrium. A better constructed and more phylogenetically accurate revision can and should wait until more complete evidence becomes available and there is a strong reason to revise the genus Alexandrium. The reasons are explained in detail by a review of the available molecular and morphological data for species of the genera Alexandrium and Centrodinium. In addition, cyst morphology and chemotaxonomy are discussed, and the need for integrative taxonomy is highlighted., (Crown Copyright © 2020. Published by Elsevier B.V. All rights reserved.)

In this study, the field ecology of Kryptoperidinium sp. was examined in two Mediterranean shallow lagoons, Calich (CA) and Santa Giusta (SG) in Sardinia, Italy. Kryptoperidinium cell density and the environmental conditions were examined monthly from 2008 to 2015 in CA and from 2011 to 2016 in SG. Cell morphology was determined by observing specimens taken from the field and from cultures that were established by single-cell isolation from samples collected in the two lagoons. The molecular identity of strains from each lagoon was also ascertained. The growth rates of the strains were determined under three different temperature conditions and six salinity treatments. The two wild populations shared the same morphology and the cultured strains were morphologically and molecularly identical. The SSU and 5.8S phylogenies show the presence of two clusters within the available Kryptoperidinium sequences and the strains obtained in this study clustered with others from the Mediterranean and Baltic. The multiannual dynamics of Kryptoperidinium sp. in the field significantly differed in the two lagoons, showing much higher cell densities in CA than in SG. The presence of Kryptoperidinium sp. was detected throughout the year in CA, with recurrent blooms also affecting the adjacent coastal area. In contrast, Kryptoperidinium sp. was sporadically observed in SG. The variation in the environmental parameters was fairly wide during the presence and blooms of Kryptoperidinium sp., especially in CA. The application of Generalized Linear Models to the field data revealed a significant role of rainfall and dissolved inorganic nitrogen on the presence and blooms of the species. Although growth rates were similar between the two strains, significant differences were detected for the 10 and 40 salinity treatments. The results obtained in this study add to our knowledge about the ecology of a harmful species that is not well understood in transitional ecosystems such as Mediterranean lagoons., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Marine benthic dinoflagellates are interesting not only because some epiphytic genera can cause harmful algal blooms but also for understanding dinoflagellate evolution and diversification. Our understanding of their biodiversity is far from complete, and many thecate genera have unusual tabulation patterns that are difficult to relate to the diverse known phytoplankton taxa. A new sand-dwelling genus, Pachena gen. nov., is described based on morphological and DNA sequence data. Three species were discovered in distant locations and are circumscribed, namely, P. leibnizii sp. nov. from Canada, P. abriliae sp. nov. from Spain, and P. meriddae sp. nov. from Italy. All species are tiny (about 9-23 μm long) and heterotrophic. Species are characterized by their tabulation (APC 4' 3a 6'' 5c 5s 5''' 2''''), an apical hook covering the apical pore, an ascending cingulum, and a sulcus with central list. The first anterior intercalary plate is uniquely "sandwiched" between two plates. The species share these features and differ in the relative sizes and arrangements of their plates, especially on the epitheca. The ornamentation of thecal plates is species-specific. The new molecular phylogenies based on SSU and LSU rDNA sequences contribute to understanding the evolution of the planktonic relatives of Pachena, the Thoracosphaeraceae., (© 2020 The Authors. Journal of Phycology published by Wiley Periodicals, Inc. on behalf of Phycological Society of America.)

Over the past decades, the occurrence, distribution and intensity of harmful algal blooms involving the dinoflagellate Alexandrium pacificum have increased in marine coastal areas disturbed by anthropogenic inputs. This invasive species produces saxitoxin, which causes the paralytic shellfish poisoning syndrome in humans upon consumption of contaminated seafood. Blooms of A. pacificum have been reported in metal-contaminated coastal ecosystems, suggesting some ability of these microorganisms to adapt to and/or resist in metal stress conditions. This study seeks to characterize the modifications in membrane proteomes (by 2-D electrophoresis coupled to LC-MS/MS), cell growth and morphometry (measured with an inverted microscope), in response to metal stress (addition of Zn 2+ , Pb 2+ , Cu 2+ and Cd 2+ ), in two Mediterranean A. pacificum strains: SG C10-3 and TAR C5-4F, respectively isolated from the Santa Giusta Lagoon (Sardinia, Italy) and from the Tarragona seaport (Spain), both metal-contaminated ecosystems. In the SG C10-3 cultures grown in a metal cocktail, cell growth was significantly delayed, and cell size increased (22% of 37.5 μm cells after 25 days of growth). Conversely, no substantial change was observed for cell growth or cell size in the TAR C5-4F cultures grown in a metal cocktail (P > 0.10), thus indicating intraspecific variability in the responses of A. pacificum strains to metal contamination. Regardless of the conditions tested, the total number of proteins constituting the membrane proteome was significantly higher for TAR C5-4F than for SG C10-3, which may help TAR C5-4F to thrive better in contaminated conditions. For both strains, the total number of proteins constituting the membrane proteomes was significantly lower in response to metal stress (29% decrease in the SG C10-3 proteome: 82 ± 12 proteins for controls, and 58 ± 12 in metal-contaminated cultures; 17% decrease in the TAR C5-4F proteome: 101 ± 8 proteins for controls, and 84 ± 5 in metal-contaminated cultures). Moreover, regardless of the strain, proteins with significantly modified expression in response to stress were mainly down-regulated (representing 45% of the proteome for SG C10-3 and 38% for TAR C5-4F), clearly showing the harmful effects of the metals. Protein down-regulation may affect cell transport (actin and phospholipid scramblase in SG C10-3), photosynthesis (RUBISCO in SG C10-3, light-harvesting protein in TAR C5-4F, and high-CO 2 -inducing periplasmic protein in both strains), and finally energy metabolism (ATP synthase in both strains). However, other modifications in protein expression may confer to these A. pacificum strains a capacity for adaptation and/or resistance to metal stress conditions, for example by (i) limiting the metal entry through the plasma membrane of the SG C10-3 cells (via the down-regulation of scramblase) and/or (ii) reducing the oxidative stress generated by metals in SG C10-3 and TAR C5-4F cells (due to down-regulation of ATP-synthase)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Amphidiniopsis is a diverse genus of thecate heterotrophic dinoflagellates within the benthic, sand-dwelling species, with more than 20 currently described. Although molecular information about members of this genus is still scarce, morphological heterogeneity suggests the genus is paraphyletic. We investigated the diversity of Amphidiniopsis species in the NW Mediterranean Sea by morphological and molecular approaches, which led to the description of three new species, A. bulla sp. nov., A. erinacea sp. nov., and A. selene sp. nov. Phylogenetic reconstructions based on SSU and LSU rDNA sequences obtained from individual cells and the observed morphological characters confirm, as previously suggested, the paraphyly of the genus and the existence of at least four phylogenetic subgroups, instead of the three main subgroups defined to date. We also morphologically characterized Herdmania litoralis, suggesting the existence of more than one species belonging to this monotypic genus. Herdmania is a sister taxon to Amphidiniopsis, both morphologically and phylogenetically, and given the paraphyly of the latter, it should be considered a member of the newly termed Amphidiniopsis genus complex. The finding of the three new species highlights that the Mediterranean harbors distinctive, sand-dwelling dinoflagellates and needs further investigations of its unexplored diversity., (© 2019 Phycological Society of America.)

In this article, the floristic lists and the seasonal mean cell volumes of phytoplankton taxa observed in three Mediterranean lagoons are reported. These datasets include 40 species, 67 other taxa identified at least at genus level, and further 13 taxa attributed only at order or class level. These data are associated with Pulina et al. "Seasonal variations of phytoplankton size structure in relation to environmental variables in three Mediterranean shallow coastal lagoons" (Pulina et al., 2018) [1], where phytoplankton taxa were included in two different cell size classes (Utermöhl fraction of phytoplankton, cell size > 3 µm; Picophytoplankton, cell size < 3 µm) and in which their seasonal variations were interpreted and discussed.

A first synoptic and trans-domain overview of plankton dynamics was conducted across the aquatic sites belonging to the Italian Long-Term Ecological Research Network (LTER-Italy). Based on published studies, checked and complemented with unpublished information, we investigated phytoplankton and zooplankton annual dynamics and long-term changes across domains: from the large subalpine lakes to mountain lakes and artificial lakes, from lagoons to marine coastal ecosystems. This study permitted identifying common and unique environmental drivers and ecological functional processes controlling seasonal and long-term temporal course. The most relevant patterns of plankton seasonal succession were revealed, showing that the driving factors were nutrient availability, stratification regime, and freshwater inflow. Phytoplankton and mesozooplankton displayed a wide interannual variability at most sites. Unidirectional or linear long-term trends were rarely detected but all sites were impacted across the years by at least one, but in many case several major stressor(s): nutrient inputs, meteo-climatic variability at the local and regional scale, and direct human activities at specific sites. Different climatic and anthropic forcings frequently co-occurred, whereby the responses of plankton communities were the result of this environmental complexity. Overall, the LTER investigations are providing an unparalleled framework of knowledge to evaluate changes in the aquatic pelagic systems and management options., (Copyright © 2018. Published by Elsevier B.V.)

Harmful algal blooms represent a severe issue worldwide. They affect ecosystem functions and related services and goods, with consequences on human health and socio-economic activities. This study reports new data on paralytic shellfish toxins (PSTs) from Sardinia and Sicily (Italy), the largest Mediterranean islands where toxic events, mainly caused by Alexandrium species (Dinophyceae), have been ascertained in mussel farms since the 2000s. The toxicity of the A. minutum, A. tamarense and A. pacificum strains, established from the isolation of vegetative cells and resting cysts, was determined by high performance liquid chromatography (HPLC). The analyses indicated the highest toxicity for A. pacificum strains (total PSTs up to 17.811 fmol cell-1). The PSTs were also assessed in a strain of A. tamarense. The results encourage further investigation to increase the knowledge of toxic species still debated in the Mediterranean. This study also reports new data on microcystins (MCs) and β-N-methylamino-L-alanine (BMAA) from a Sardinian artificial lake (Lake Bidighinzu). The presence of MCs and BMAA was assessed in natural samples and in cell cultures by enzyme-linked immunosorbent assay (ELISA). BMAA positives were found in all the analysed samples with a maximum of 17.84 µg L-1. The obtained results added further information on cyanotoxins in Mediterranean reservoirs, particularly BMAA, which have not yet been thoroughly investigated.

Bysmatrum subsalsum is a cosmopolitan dinoflagellate species that inhabits marine and transitional habitats. Despite its wide distribution, information on the morphological variability, phylogeny and ecology of B. subsalsum is scarce. In this study, we provide morphological and molecular data on B. subsalsum strains and wild cells from different locations in the Mediterranean Basin. The dynamics of cell abundances and the associated environmental conditions during a field bloom are also described. Genetic sequences of B. subsalsum obtained in this study showed large intraspecific differences, clustering in two well-differentiated clades. Despite a certain degree of variation with respect to cell size, apical pore complex (APC) morphology and size, and cingulum displacement, cells from the two clades showed similar morphological traits. These findings indicated the occurrence of cryptic species. Comparisons of the morphology of our B. subsalsum specimens with the few descriptions available in the literature revealed larger than previously known intraspecific morphological variability. Phylogenetic trees inferred from the concatenated SSU, 5.8S-ITS, and LSU rRNA and the individual 5.8S-ITS regions suggested the inclusion of Bysmatrum in the Peridiniales and a close phylogenetic relationship with Peridinium sensu stricto. However, the low statistical support prevented the assignment of Bysmatrum to a particular family of Peridiniales. Ecological data obtained from a bloom in La Pletera salt marshes (Catalan Coast, Spain) suggested the species reaches high cell abundances at water temperatures >20°C and salinity levels >30. Our results add new information regarding the morphology, phylogeny, and ecology of B. subsalsum., (© 2017 Phycological Society of America.)

Recurrent blooms of Chattonella subsalsa (Raphidophyceae) were associated with fish kills in Santa Giusta Lagoon (Mediterranean Sea). This study investigated the population dynamics of C. subsalsa and its relationship with environmental and meteorological conditions, using multiannual ecological data (1990-2016). In addition, for the first time, this study examined the presence of C. subsalsa cysts in lagoon sediments. The species was first detected in Santa Giusta Lagoon in July 1994. Bloom events coinciding with fish kills were recorded in 1994, 1998, 1999, and 2010. The timing and dynamics of C. subsalsa blooms and fish kills varied over the examined period. Presence of C. subsalsa was strongly influenced by temperature, especially in the early years of the series (1990-2002). Temperature control may have been lesser important in the more recent years, when higher temperature may have generated continuative suitable conditions for C. subsalsa affirmation, especially in July. Thus, the variations in the availability of food (via autotrophy and/or mixotrophy) could be one of the control keys on the proliferation of this species in the future in SG. Cysts of C. subsalsa were present in lagoon sediments at abundances ranging 200-2000cystsg -1 wet sediment. This study is among a few that have examined C. subsalsa population dynamics and bloom events in the field over a long time period. Findings from this study contribute to a better understanding of C. subsalsa bloom development, by identifying environmental and meteorological variables that may promote blooms of this species in the Santa Giusta Lagoon., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this study, the geographical distribution and multiannual trends of potentially toxic harmful algal species (HAS) were analysed at 18 mussel farms in Sardinia (Italy, North-Western Mediterranean Sea) using data derived from the Sardinian Regional Monitoring Programme (1988-2012). The results showed an increasing number of potentially toxic microalgae over the study period. Alexandrium catenella and Alexandrium minutum were the most harmful species detected. From 2002 to 2009, these species caused eight paralytic shellfish poisoning-positive events which temporarily stopped commercial trade of mussels. The statistical analysis indicated that some taxa exhibited temporal increasing trends in their abundance (e.g. Pseudo-nitzschia spp.), significant decrements (e.g. Dinophysis sp.), or both increasing and decreasing significant trends (e.g. A. minutum) at different sites, indicating the necessity of further in-depth studies, especially on certain taxa. Overall, the statistical elaboration of the long-term data provided useful signals for early detection of shellfish contamination by different potentially toxic HAS in defined sites. These signals can be used to develop best management practices.