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Reservoirs are primary water resources for many uses in the Mediterreanean region and need dedicated studies for understanding the complexity of their dynamics particularly vulnerable to local and global stressors. This study focused on phytoplankton variations in relation to seasonal environmental changes on a multiannual time scale (2006–2015) at a Mediterranean eutrophic reservoir (Bidighinzu Lake, Italy) belonging to the Italian, European and International Long Term Ecological Research networks. Phytoplankton cell density, volume and biomass and chlorophyllaconcentrations were analysed together with meteo-climatic, hydrological, physical and chemical variables to detect trends and correlations. The period under study was also compared with previous years to assess the presence of significant differences in the environmental and planktonic compartments. Multiannual changes were more pronounced in summer than in the other seasons during the decade under study. The most conspicuous environmental changes were a significant decrease in summer nutrient concentrations in the reservoir and a simultaneous anthropic pressure reduction in the watershed. In addition, the mixing zone and euphotic zone ratio also increased. Multiannual changes in summer phytoplankton composition consisted of an increased density of smaller Bacillariophyceae and Cyanophyceae, which replaced larger species of the same phytoplankton classes. This resulted in opposite trends of total phytoplankton cell density (increasing) and mean phytoplankton cell volume (decreasing) over the study years. The nutrient decrement was statistically the strongest environmental driver of the phytoplankton changes observed in the reservoir. However, the mixing zone and the euphotic zone ratio and water temperature also significantly affected the multiannual phytoplankton variations. Therefore, we conclude that the success of small cell-sized phytoplankton in Bidighinzu Lake was most probably due to the synergic interactions of more environmental forces related to changing anthropic pressures and climate variability. Our results highlight the importance of long-term monitoring of reservoirs in the Mediterranean basin, especially in semi-arid regions where the need and scarcity of high quality water will be further exacerbated due to the global climate change.

Seasonal dynamic of Utermohl fraction of phytoplankton (UFP, cell size > 3 μm) and picophytoplankton (Pico, cell size

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.

In Sardinia, Italy, karst springs are strategic water resources and potential hotspots of biodiversity; however, they are understudied, and their communities remain largely unknown. This study was conducted at Sa Vena spring (Su Gologone system) to characterize the diatom communities, to describe their relationships with environmental variables, and to evaluate the impact of an extreme flash flood. High species richness, diversity, and evenness were found both in epiphytic and epilithic assemblages. Statistical analyses showed significant differences between assemblages from the 2 substrates and in assemblages from the same substrate. Differences seem due to the stronger impact of seasonal water level variations and flash flood on macrophytes than on cobbles. Further, epilithic assemblages showed more stable behavior over time, both on an annual (higher resistence) and a multiannual (higher resilience) scale. Alkalinity (p = 0.002) and dissolved oxygen (p = 0.004) explained a significant amount of...

The thermo-mineral springs of Sardinia have historically been the object of several geochemical studies, whereas the biota and ecology have been totally neglected. The aim of this work is to contri...

One of the primary detrimental effects of eutrophication is the tendency of nuisance cyanobacterial species to increase in number and biomass in freshwater ecosystems. The aim of this study was to investigate possible management actions to control eutrophication and assure water use of a eutrophic deep Mediterranean climate reservoir, dominated by cyanobacteria. With this goal, we defined the trophic state of Lake Cedrino (Sardinia, Italy) and studied its phytoplankton, paying particular attention to cyanobacteria, and to seasonal variation of phytoplankton in relation to seasonal variation of environmental variables. The water samples were collected monthly from September 2010 to August 2011 at differing depths from the surface of the water to the bottom at a station located in the deeper portion of the reservoir. Physical, chemical, nutrient, qualitative and quantitative analyses of phytoplankton were performed, and the trophic state was evaluated based on the Trophic State Index and the OECD model. Abundance of nutrients and phytoplankton (cell density, biomass and chlorophyll a ) indicated a eutrophic condition of the reservoir. In summer, phytoplankton species composition was dominated by nuisance cyanobacteria, particularly Aphanizomenon flosaquae , thereby requiring management plans for harmful blooms. On the base of lake features, we propose management actions at different scales and levels to resolve eutrophication and to allow water use: from nutrient load reduction in the watershed (primarily from point-sources) to deep water aeration, to immediately face an attenuation of eutrophic effects. This study is the first explorative step in planning restoration of Lake Cedrino.

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 200–2000 cysts g −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.

Data from five sites of the International Long Term Ecological Research (ILTER) network in the North-Eastern Pacific, Western Arctic Ocean, Northern Baltic Sea, South-Eastern North Sea and in the Western Mediterranean Sea were analyzed by dynamic factor analysis (DFA) to trace common multi-year trends in abundance and composition of phytoplankton, benthic fauna and temperate reef fish. Multiannual trends were related to climate and environmental variables to study interactions. Two common trends in biological responses were detected, with temperature and climate indices as explanatory variables in four of the five LTER sites considered. Only one trend was observed at the fifth site, the Northern Baltic Sea, where no explanatory variables were identified. Our findings revealed quasi-synchronous biological shifts in the different marine ecosystems coincident with the 2000 climatic regime shift and provided evidence on a possible further biological shift around 2010. The observed biological modifications were coupled with abrupt or continuous increase in sea water and air temperature confirming the key-role of temperature in structuring marine communities.

Picophytoplankton (Pico) seasonal dynamics and ecology were investigated in three eutrophic coastal lagoons (Calich, Santa Giusta, and Corru S’Ittiri) located in the same geographic region (Sardinia, Mediterranean Sea). Pico dynamics were examined to determine a relationship with variability in environmental conditions characterizing the three sites, and identify which parameters affected observed Pico dynamics. Results showed Pico density reached 108 cells L−1 and biomass values did not exceed 72.8 μg C L−1. Statistical analyses detected significant differences in hydrographic and nutrient conditions among lagoons, which were also characterized by variable Pico seasonal dynamics and composition. Calich and Santa Giusta were dominated all year around by picocyanobacteria. Maximum picocyanobacteria abundance was observed during summer in both lagoons, associated with the highest temperatures recorded. Picocyanobacteria abundance and nutrient concentrations showed a significant negative and positive correlation in Calich and Santa Giusta, respectively. In contrast, picoeukaryotes dominated Pico assemblages in Corru S’Ittiri, where the highest transparency and salinity and the lowest seasonal variation in salinity were recorded. In Corru S’Ittiri, the maximum Pico abundance was observed in autumn, when lower temperature and the highest nutrient concentrations were observed. Our study provides information on Pico assemblage ecology, which remains scarce in coastal and transitional environments, particularly in Mediterranean climate regimes.

Predicting the responses of organisms is a complex challenge especially when water temperature is expected to increase over the coming decades, as a result of global warming. In this work the effects of warming on phytoplankton communities were investigated. An indoor experiment was performed, where water from a Mediterranean lagoon was incubated at different temperatures. Three treatments were applied in triplicate incubation units: the control (11 °C), 3 °C increase (14 °C), and 6 °C increase (17 °C). Our results showed significant effects by warming on phytoplankton. The abundance of relatively smaller taxa (Chlorella sp. and Planktothrix agardhii–rubescens group) increased at 17 °C, whereas the abundance of relatively larger species (Cyclotella sp. and Thalassiosira sp.) decreased, compared with the control. This shift towards smaller taxa resulted in a higher total biomass but lower chlorophyll a concentrations at the highest temperature.

We investigated multiannual trends in phytoplankton in relation to several environmental drivers. We analyzed ecological data collected during the past two decades from three aquatic sites: an artificial lake, a coastal lagoon, and a marine coastal area. Hydrographic, nutrient, and phytoplankton data were statistically analyzed to detect trends and interactions. In all ecosystems, the chlorophyll a concentration decreased with increasing abundance of small-sized phytoplankton. Phytoplankton dynamics were related to decreased nutrient concentrations in the lake, to dynamics of phosphorus and decreased salinity in the lagoon, and probably to combined top-down and bottom-up processes in the marine gulf.

With many lakes and other inland water bodies worldwide being increasingly affected by eutrophication resulting from excess nutrient input, there is an urgent need for improved monitoring and prediction methods of nutrient load effects in such ecosystems. In this study, we adopted a catchment-based approach to identify and estimate the direct effect of external nutrient loads originating in the drainage basin on the trophic state of a Mediterranean reservoir. We also evaluated the trophic state variations related to the theoretical manipulation of nutrient inputs. The study was conducted on Lake Cedrino, a typical warm monomictic reservoir, between 2010 and 2011. We assessed the hypereutrophic condition of the reservoir by monthly samplings of the water column and compared these results with the amount of nutrient load originating from anthropic activities in the drainage basin [42.6 t P y−1 for total phosphorus (P) and 531 t N y−1 for total nitrogen (N)]. We verified how the predictive OECD management model could be confidently applied to predict the P concentration in the reservoir on the basis of estimated loads from the drainage basin (98.7 mg P m−3 assessed versus 101 mg P m−3 estimated, approximately 2.5% over). Different scenarios are presented showing how it is possible to reduce approximately 62% P and 43% N, altering the condition of the ecosystem to become more mesotrophic. We also propose some management strategies to improve water quality in this lake ecosystem.

Artificial lakes are strategic water resources in the Mediterranean region but are one of the most vulnerable areas to the impacts of climate change, particularly to the expected significant decrease in water resources; therefore, enhancing the ability of water management to improve water quality is crucial. This study contributes to the knowledge of the long-term ecological features of Mediterranean artificial lakes based on a case study of Bidighinzu Lake in Sardinia, Italy, a warm, monomitic and hypereutrophic reservoir mainly used for drinking water. Among the different restoration actions carried out in Bidighinzu Lake to improve water quality is the reduction of nutrient loads from the watershed. To study multiannual trends of the trophic state, a long-term series (1988–2012) of both environmental variables and phytoplankton was analysed. Mann-Kendall tests revealed increasing trends for total nitrogen to total phosphorus ratios (TN:TP; significant in spring, summer, and winter) and decreasing trends for ammonium (winter and autumn), TP (all seasons), orthophosphate (spring, summer, and winter), reactive silica (autumn), and pH (summer). Among phytoplankton, significant increasing trends were assessed in biomass of Bacillariophyceae, Chlorophyceae, Dinophyceae, and Chrysophyceae. Cyanobacteria did not show a clear trend, although at the order level, Chroococcales significantly increased in summer and decreased in winter. Despite these major tendencies, the lake did not show significant improvement in its eutrophic state, probably due to an inherent resistance and the insufficient and/or not well calibrated or applied recovery actions.

Spread of alien species (AS) is a serious threat to marine habitats and analysis of principal descriptors of their occurrence is pivotal to set reliable conservation strategies. 2. In order to assess the susceptibility of marine habitats to biological invasions, a dataset was gathered of the occurrence of 3899 species from 29 phyla, taken from 93 marine sites located along the Italian coast in the period 2000-2012.

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.

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.

15 pages, 10 figures, 3 tables, supporting information https://dx.doi.org/10.1111/jpy.12546, 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, This research was supported by a Marie Skłodowska Curie International Outgoing Fellowship within the 7th European Community Framework Programme (Project CONPLANK, PIOF-GA-2011-302562). The Regione Sardegna funded Research Project “Master and Back” financed C. T. Satta’s work. The Zoumgest project provided the financial support required for the Corru S’Ittiri Lagoon sampling. Financial support was also provided by the project DEVOTES, funded by the 7th European Community Framework Programme, “The Ocean for Tomorrow” (GA-308392)

Chrysophaeum taylorii (Pelagophyceae) is an allochthonous benthic microalga recently recorded in the Mediterranean Sea. During summer, the occurrence of C. taylorii is usually visible to the naked eye due to the large amount of mucilage this species produces. Information on the spatio-temporal variability of this species and on the predictability of massive mucilage events is still scarce and requires to define ad hoc managing strategies of major bloom events. The aim of this work was to identify the relevant scales of variation in the abundance of C. taylorii abundance and to estimate the relative recurrence of its blooms, testing the hypothesis that mucilage was depend- ent on the cell density. The first approach was the identi- fication of the most appropriate sampling procedure to estimate benthic cell abundance of C. taylorii. The second one was the estimation of the magnitude of variation in C. taylorii cell abundance attributable to each of several spa- tial (areas, sites, zones and replicates) and temporal scales (fortnights and years) in the Marine Protected area of Tavolara Punta Coda Cavallo (Western Mediterranean Sea). The results indicate fortnight and year as the most relevant scales of variability in the cell abundance of C. taylorii and

Reservoirs are subject to severe fluctuations in the water level from seasonal and interannual climatic variations, as well as abstraction for irrigation, hydropower, and drinking water. This can affect the matter and energy transfer through the food web, of which zooplankton is of crucial importance. We traced seasonal changes in the carbon and nitrogen stable isotope signatures of suspended particulate matter and crustacean zooplankton from a small Mediterranean reservoir. The delta C-13 and delta N-15 isotopic baseline signature of the lake varied seasonally, becoming more C-13-depleted and N-15-enriched in winter and less C-13-depleted and N-15-enriched values in the drier summer months, when external water inputs were negligible. Seasonal changes in the delta C-13 and delta N-15 SPM isotopic signature were well reflected in the herbivorous cladocerans. delta N-15 of the calanoid and cyclopoid copepods were at least 3% greater than for the herbivorous cladocera, suggesting their potential use as a food resource. delta C-13 of predatory copepods were also consistent with seasonal fluctuations in the delta C-13 SPM baseline, except during the heavy rains in early spring, when they were observably rich in lipids with a higher C/N ratio, suggesting that they had entered dormancy and were not actively feeding in the water column. This indicates the importance of taking into account not only the seasonality, but the community dynamics and trophic level of zooplankton taxa when interpreting stable isotope studies.

This study focused on expanding existing knowledge about benthic diatoms and their use as indicators of biological quality and physical disturbance in six Mediterranean watercourses within the Rio Mannu di Porto Torres basin in northwestern Sardinia, Italy. Benthic diatoms were collected from 11 stations during a 1-year cycle from summer 2010 to summer 2011. The Eutrophication/Pollution Index – Diatom-based (EPI-D) was used to evaluate biological quality, and the Navicula Nitzschia Surirella Index (NNS’) was used to estimate the degree of physical disturbance at each station. In addition, physico-chemical variables and Escherichia coli were measured and analyzed each month. In total, 193 diatom taxa were identified, of which 157 belonging to 57 genera were present in the counts and were used to calculate the diatom indices. Five taxa were recorded for the first time for Sardinian watercourses; of which, Amphora paraveneta Lange-Bertalot, Cavacini, Tagliaventi & Alfinito, Fallacia pygmaea ssp. subpygmaea L...

18 pages, 6 figures, 6 tables, The present study identified and quantified dinoflagellate cysts in surface sediments from three Mediterranean lagoons. Sediment samples were recovered from 11 stations in May 2009 at Cabras Lagoon, eight stations in May 2010 at Corru S'Ittiri Lagoon, and five stations in May 2011 at Santa Giusta Lagoon. Fifty-three dinoflagellate cyst morphotypes were identified. Sixteen species are first reports for the lagoons, and two for the Mediterranean Sea. Moreover, a new Scrippsiella species was discovered in Cabras. Seven harmful algal species were identified, primarily belonging to the potentially toxic genus Alexandrium. Total cyst abundance, number of morphotypes, and assemblages varied among lagoons, and each lagoon showed a distinct morphotype composition. A degree of heterogeneity was also detected within lagoon. Cabras and Santa Giusta cyst assemblages were characterised by morphotypes belonging to the autotrophic genus Scrippsiella , whereas Corru S'Ittiri assemblages showed dominance of heterotrophic morphotypes, including Protoperidinium cf tricingulatum. Differentiation among lagoons was also evident according to environmental conditions. Salinity proved to be a fundamental variable in determining total cyst abundance, morphotype number, and composition. This study was among the first to examine dinoflagellate cyst composition in coastal lagoons, especially from the Mediterranean region, and contributed data that increased our knowledge of cyst-producing dinoflagellates in these environments., The Autonomous Region of Sardinia provided the principle financial support for the Cabras and Santa Giusta monitoring activities, and the Zoumgest project provided the financial support required for the Corru S'Ittiri Lagoon. The Autonomous Region of Sardinia funded Research Project – Master and Back financed C. T. Satta work. A Postdoctoral Grant from the Spanish Ministry of Economy and Competitiveness partially funded S. Anglès work

15 pages, 4 figures, 4 tables, The composition and assemblages of living dinoflagellate cysts from two estuarine bays (Alfacs and Fangar bays) in the northwestern Mediterranean Sea were investigated, focusing on the presence and distribution of harmful species. Sediment cores were taken from 10 stations in Alfacs Bay and from 6 stations in Fangar Bay. Sediment samples from the surface (the top 1 cm) and the subsurface profile (from 2 to 5 cm depth) in selected stations, were analyzed. Sixty-two morphotypes were recovered, some of which are new reports for the northwestern Mediterranean area. Few morphotypes dominated in terms of abundance and relative percentage (e.g. the Scrippsiella trochoidea complex was the dominant and most widely distributed morphotype in each bay, reaching maxima of 163 cysts cm−3 wet sediment (ws) and 102 cysts cm−3 ws in Alfacs and Fangar bays, respectively). The assemblage in Alfacs Bay was also characterized by the presence of Biecheleria cincta (maximum 116 cysts cm−3 ws), whereas the occurrence of Pentapharsodinium tyrrhenicum (maximum 37 cysts cm−3 ws) was greater in Fangar Bay. Twelve morphotypes belonging to potentially toxic or noxious species were detected, with the genus Alexandrium dominating. Among the harmful species, Gymnodinium litoralis and Vulcanodinium rugosum are reported for the first time from the study areas. Furthermore, cysts of the high biomass bloom-forming species Kryptoperidinium foliaceum are reported for the first time in the Mediterranean Sea. All the harmful species, with the exception of Alexandrium minutum, showed greatest abundances in subsurface samples. Profile analysis led to the description of a new cyst morphotype belonging to the Alexandrium genus (presumably A. insuetum). Our results provide information on the presence of harmful species in the studied bays, confirming the usefulness of cyst analysis in assessment of the potential risk of harmful blooms in aquaculture areas, Financial support was provided by the Agència Catalana de l’Aigua (Department de Medi Ambient, Generalitat de Catalunya) and the CSIC through the contract ‘Pla de vigila` ncia de fitoplàncton nociu i tòxic a la Costa Catalana’. The work of Cecilia T. Satta was supported by the Autonomous Region of Sardinia financed Research Project ‘‘Master and Back’’. The work of S. Angle` s was partially supported by a Postdoctoral Grant from the Spanish Ministry of Economy and Competitiveness

1. Spread of alien species (AS) is a serious threat to marine habitats and analysis of principal descriptors of their occurrence is pivotal to set reliable conservation strategies. 2. In order to assess the susceptibility of marine habitats to biological invasions, a dataset was gathered of the occurrence of 3899 species from 29 phyla, taken from 93 marine sites located along the Italian coast in the period 2000–2012. 3. In total, 61 AS belonging to 11 phyla have been recorded. Invertebrates were the most represented (63%). Alien species were found in all the habitats examined (EUNIS, level 2), although they showed highest abundance in benthic habitats. Most of the AS were associated with a single EUNIS habitat, while some of them were present in more than one habitat. Trans-habitat occurrence suggests the potential invasiveness of AS. 4. According to statistical analysis, AS recorded could have been more numerous, since some of the marine habitats seemed to be still unsaturated. The model that best describes the spread of AS takes account of both native species richness (Rn) and EUNIS habitat type as explanatory variables. The number of observed AS was directly related to Rn and it was highest in rocky circalittoral and infralittoral habitats. 5. The results of this macro-ecological study focus on the importance of performing large-scale studies, since adopting ecosystem approaches to marine invasion management seems especially fruitful. 6. The results, moreover, highlight the importance of AS monitoring of different habitats, from those subjected to anthropogenic pressure, historically considered to be hubs of introduction of AS, to the most biologically rich and diverse marine habitats. Indeed, it is necessary to set monitoring strategies to detect the introduction, the distribution and persistence of AS over time. These recommendations are especially significant in the light of the strategic plans currently under formulation in Mediterranean countries with regard to AS monitoring

Karst springs are considered among the most vulnerable groundwater-dependent ecosystems. Despite their ecological value and importance as strategic water sources, Mediterranean karst springs are still poorly investigated. The aim of this study was to analyse the epilithic diatom assemblages and to test their usefulness as indicators of environmental quality on the Su Gologone spring (central-eastern Sardinia, Italy), a biotope of great natural value and a precious source of drinking water. A total of 89 diatom taxa were found with 25 new records for Sardinian running waters. Species richness, Shannon-Wiener and Pielou indices showed good biotic integrity. The dominant taxa were alkaliphilous, halophobous-oligohalobous exigent, xeno- oligosaprobic and characteristic of oligotrophic waters. The eutrophication/pollution index − diatom based (EPI-D) and the Navicula Nitzschia Surirella indices indicated respectively an excellent/good biological water quality and a low physical disturbance. However, the biological and chemical oxygen demand, and the microbiological variables (E. coli, fecal and total coliforms) revealed an organic contamination of the water, although moderate. The judgment provided by the EPI-D should be verified after updating of the index. In fact, 10 taxa found in this study are not currently considered by the EPI-D method.

Chattonella species in a Mediterranean lagoon (Santa Giusta Lagoon, Sardinia, Italy) were identified by applying a molecular approach to fixed natural phytoplankton samples collected over the last two decades. Like the other raphidophytes, Chattonella cells are naked and lose their shape when fixed, making species identification difficult on the basis of their morphological characteristics. Employing species-specific primers (oBTG-005-F, oBTG-027-R, oBTG-028-R) for the amplification of the ITS-5.8S rDNA region, we established the occurrence of C. subsalsa in fixed natural phytoplankton samples collected in coincidence with fish death events. Additionally, we established the presence of the recently discovered C. cf. subsalsa Adriatic genotype by analysing cellular cultures obtained from the same lagoon in 2013. This is the second worldwide record of C. cf. subsalsa Adriatic genotype. Our results revealed that the species-specific primers oBTG-005-F and oBTG-028-R distinguished this new genotype only when present singularly. This study provides valuable data that increase knowledge of C. subsalsa genotypes and of the long-term occurrence of Chattonella blooms in a transitional ecosystem through the use of samples up to 20 years old. Se identificaron especies de Chattonella mediante la aplicación de técnicas moleculares en muestras naturales de fitoplancton. Las muestras fueron recogidas y fijadas durante las últimas dos décadas en una laguna litoral mediterránea (Laguna de Santa Giusta, Cerdeña, Italia). Al igual que otras rafidoficeas, las células de Chattonella no poseen teca y, por lo tanto, pierden su forma cuando se fijan lo que dificulta la identificación basada en características morfológicas. Con el uso de cebadores específicos a nivel de especie (OBTG-005-F, OBTG-027-R, OBTG-028-R) diseñados para la amplificación de la región ITS- 5.8S rDNA, se detectó la presencia de C. subsalsa en las muestras recogidas en periodos coincidentes con eventos de muerte de peces. A través del análisis de los cultivos celulares obtenidos de la misma laguna en el año 2013, se identificó la presencia, por segunda vez a nivel mundial, del recientemente descubierto genotipo Adriático de C. cf. subsalsa. Los resultados revelaron que los cebadores oBTG-005-F y oBTG-028-R amplifican este nuevo genotipo sólo cuando está presente individualmente. En este estudio se presentan datos relevantes para el conocimiento de los genotipos de C. subsalsa y sobre la presencia recurrente de proliferaciones de especies de Chatonella en un ecosistema de transición a través de la utilización de muestras recogidas durante los últimos veinte años y analizadas hoy en día.

Stable isotope analysis of carbon (C) and nitrogen (N) was used to study the nature and origin of the suspended particulate matter (SPM) in a small Mediterranean reservoir, Lake Sos Canales (SC). The δ13 C and δ15 N isotopic ratios, physical-chemical parameters, nutrients and phytoplankton were analyzed ca. monthly over a hydrological year on the vertical profile at two stations (lacustrine and riverine). SPM quantity and composition were related to the hydrological annual dynamic. In Mediterranean reservoirs, water-level fluctuation is one of the most important stressors, largely dependent on the strong seasonality of climate and water exploitation for human uses. Mediterranean reservoirs show different phases during a hydrological year, alternating empty and low water level (summer–autumn), re-filling (winter–spring) and high water (spring–summer) phases. Isotopic ratios of C and N were similar on the vertical profile and at the two stations during the low water phase, but differed during the re-filling and high water phases. Significant correlations were found between δ15 N and water level, and between δ13 C and temperature in the surface layer at the lacustrine station. An unusual δ13 C distribution along the water column during the re-filling phase was interpreted on the basis of phytoplankton species composition, mainly due by Gymnodinium uberrimum .

In Mediterranean lagoons, macrophytes often surpass phytoplankton as the most important primary producers. Less frequently, phytoplankton dominates throughout the year, thus knowledge of its dynamics is relatively limited and scattered. In this study, we assessed over two years the dynamics of phytoplankton assemblages, including potential harmful algal species (HAS), in relation to environmental changes in the phytoplankton-dominated Cabras Lagoon (Sardinia, Italy). The lagoon was characterised by uniform spatial conditions, wide temporal variations in salinity (40 PSU) and high nutrient availability. Phosphorus was highest in summer, possibly recycled within the system, while dissolved inorganic nitrogen increased in winter and spring due to watershed discharge. Chlorophyll a, positively correlated with nutrients and rainfall, showed a typical bimodal pattern with summer-winter blooms. Modifications in phytoplankton composition strongly correlated with extreme weather events, such as intense rainfall. This generated an abrupt salinity decrease that, combined with high nutrient availability, favoured the dominance of Cyanophyceae of reduced cell size, such as Cyanobium and Rhabdoderma species. We suggest that the prolonged and intense dominance of Cyanophyceae, added to other HAS, has a negative impact on the primary economic activities of the lagoon, such as fishery, and generally on the whole lagoon functioning.

Population structure of the sea urchin Paracentrotus lividus seems to vary depending on the habitat, as, on average, urchin density is higher on rocks, and size is larger in Posidonia oceanica seagrass. Here, we tested the hypothesis that P. lividus would choose P. oceanica rather than rocky habitat due to the greater availability of shelter and food in the seagrass. We conducted 2 experiments by using aquaria divided into 2 equal sections, each containing an array of 2 habitats: natural P. oceanica (P) and rocks (R) in the first experiment and natural (NP) and artificial (AP) P. oceanica in the second (to highlight the reason for preference). Each experiment included 2 experimental stages of no-choice (Stage 1) and choice (Stage 2): in the 2 no-choice treatments, sections were filled with the same habitat, and in the 2 choice treatments, sections were filled with P and R in Expt 1 and NP and AP in Expt 2. Under the null hypothesis that preference of habitat is random, the expected numbers of sea urchins that were distributed in the 2 sections of the habitat after 24 h were estimated by using formulae derived from maximal likelihood estimates. The results evidenced a preference by P. lividus for P. oceanica habitat rather than rocky habitat in the first experiment and for natural P. oceanica rather than artificial seagrass in the second experiment, thus suggesting that P. lividus individuals searched for a well-structured habitat where they could find both shelter and food.

The temporal variations in phytoplankton abundance and diversity were analysed from 1999 to 2009 in Cabras Lagoon, a shallow eutrophic Mediterranean lagoon (west coast of Sardinia). It is one of the aquatic ecosystems listed in the “Marine Ecosystems of Sardinia” by the Italian Network of Long-Term Ecological Research (LTER Italy). The objectives of this work were to assess the general features of phytoplankton succession and its dynamics in relation to environmental factors along the decade 1999–2009, and to identify the main forces driving phytoplankton variability in terms of the general trends in Mediterranean transitional waters. Our results highlight several important aspects: a shift in the annual peak density from the summer–autumn season, observed in 1999–2002, to the winter–spring season in subsequent years; simultaneous reductions in chlorophyll a concentrations and cell size from 1999 to 2008; and the modification of the structure of the phytoplankton assemblages, from a more differen...

The aim of our study was to evaluate the abundance of cyanobacteria and microcystins in four Sardinian reservoirs (Italy) characterised by different trophic status to define a reference picture for future changes. Increasing levels of eutrophication and the abundance of cyanobacteria are expected to occur due to climate change, especially in the southern Mediterranean. Consequently, an in-depth study of the occurrence of harmful cyanobacteria is important to develop appropriate management strategies for water resources at a local scale. Monthly samples were collected at one station in each reservoir over an 18-month period. The Analysis of similarity indicated that cyanobacterial abundance and species composition differed significantly among the reservoirs. The Redundancy analysis highlighted their relationship to trophic, hydrological and seasonal patterns. Spearman’s analysis indicated that there were significant correlations among the most important species (Planktothrix agardhii–rubescens group, Aphanizomenon flos-aquae and Dolichospermum planctonicum), nutrients and microcystins. We highlighted that the species composition during periods of maximum microcystin concentrations differed from those typically reported for other Mediterranean sites. We found new potential microcystin producers (Aphanizomenon klebahnii, Dolichospermum macrosporum and Dolichospermum viguieri), which emphasised the high diversity of cyanobacteria in the Mediterranean area and the need for detailed research at the local scale.

Besides protection, the variability of assemblages in a marine reserve can result from the geographical features of the locations. Islands present within a marine protected area (MPA) offer an extremely valuable system to test the hypotheses of large-scale spatial patterns in assemblages, particularly when patterns on the islands were contrasted with those of the mainland. In fact, besides the natural causes of variability, insular locations are generally less accessible to humans than those on the mainland, with changing levels of accessibility, on the basis of the distance from the coast. This study examined the interactive effect of protection and geographical siting at Tavolara–Punta Coda Cavallo MPA in Sardinia, Italy, on gastropod species subjected to human harvest. Rocky-shore gastropod assemblages were sampled at locations with different level combinations of protection and accessibility. Results highlighted that assemblages in the MPA have been more significantly influenced by the geogra...

Predicting community susceptibility to invasion has become a priority for preserving biodiversity. We tested the hypothesis that the occurrence and abundance of the seaweed Caulerpa racemosa in the north-western (NW) Mediterranean would increase with increasing levels of human disturbance. Data from a survey encompassing areas subjected to different human influences (i.e. from urbanized to protected areas) were fitted by means of generalized linear mixed models, including descriptors of habitats and communities. The incidence of occurrence of C. racemosa was greater on urban than extra-urban or protected reefs, along the coast of Tuscany and NW Sardinia, respectively. Within the Marine Protected Area of Capraia Island (Tuscan Archipelago), the probability of detecting C. racemosa did not vary according to the degree of protection (partial versus total). Human influence was, however, a poor predictor of the seaweed cover. At the seascape level, C. racemosa was more widely spread within degraded (i.e. Posidonia oceanica dead matte or algal turfs) than in better preserved habitats (i.e. canopy-forming macroalgae or P. oceanica seagrass meadows). At a smaller spatial scale, the presence of the seaweed was positively correlated to the diversity of macroalgae and negatively to that of sessile invertebrates. These results suggest that C. racemosa can take advantage of habitat degradation. Thus, predicting invasion scenarios requires a thorough knowledge of ecosystem structure, at a hierarchy of levels of biological organization (from the landscape to the assemblage) and detailed information on the nature and intensity of sources of disturbance and spatial scales at which they operate.

An intense proliferation of cyanobacteria in Cabras Lagoon was investigated over a period of two years (July 2007 to June 2009). The influence of environmental and meteorological parameters in the lagoon on temporal variations in cyanobacteria orders was assessed. For 17 months, Chroococcales was the only cyanobacterial order observed in the lagoon. Cyanobium-type cells (Reynolds functional group Z) were the most abundant phytoplankton taxon during this period. In the following months, drastic changes in the cyanobacteria assemblages occurred simultaneously with constant, intense rainfall that led to a sudden drop in the lagoon’s salinity. The succession of autumn–winter Oscillatoriales (Planktothrix sp. and Pseudanabaena catenata; Reynolds functional group S1) and late spring growth of Nostocales (Aphanizomenon gracile, Aphanizomenon aphanizomenoides, and Anabaenopsis circularis; Reynolds functional group H1) was monitored. Canonical Correspondence Analysis was carried out to quantify the influence of environmental variables, and indicated strong relationships between Chroococcales and salinity, Oscillatoriales and higher values of SRP and the DIN/SRP ratio, and Nostocales and lower nutrient concentrations, the DIN/SRP ratio and salinity. Durante dos años (julio 2007-junio 2009) se monitoreó una proliferación intensa de cianobacterias en la laguna de Cabras, así como los parámetros ambientales y climáticos que determinaron sus variaciones temporales. Durante 17 meses, Chroococcales fue el único orden de cianobacterias en la laguna, del cual células similares a Cyanobium (grupo funcional Z según Reynolds) fueron las más importantes en cuanto a abundancia. En los meses siguientes, las cianobacterias sufrieron cambios drásticos, que ocurrieron simultáneamente con lluvia constante e intensa que dio lugar a una caída brusca de la salinidad de la laguna. Se monitoreó también la sucesión de Oscillatoriales en otoño-invierno (Planktothrix sp. and Pseudanabaena catenata; grupo funcional S1 según Reynolds) y el crecimiento en primavera de Nostocales (Aphanizomenon gracile, Aphanizomenon aphanizomenoides, y Anabaenopsis circularis; grupo funcional H1 según Reynolds). Análisis de Correspondencia Canónica permitieron cuantificar la influencia de las variables ambientales, indicando una estrecha relación entre Chroococcales y salinidad, Oscillatoriales y altos niveles de SRP y proporción DIN/SRP, y Nostocales y bajos niveles de nutrientes, proporción DIN/SRP y salinidad.

The sea urchin Paracentrotus lividus is common in the Mediterranean Sea in shallow subtidal rocky habitats, and it is intensely harvested for commercial and recreational purposes. This study is aimed at investigating whether the effects of harvest restrictions of P. lividus in rocky reef habitats interact with the accessibility of locations in structuring sea urchin population (total and commercial-sized individuals). These results are important for generating hypotheses about the influence of human harvesting on P. lividus and for addressing suitable measures of conservation. Paracentrotus lividus was sampled after the end of the sea urchin harvesting period (May–July 2007) within the Gulf of Alghero (North West Sardinia), where the Capo Caccia–Isola Piana Marine Protected Area (MPA) was established since 2002. Paracentrotus lividus was sampled at sixteen locations and attributed in groups of four to 4 combinations of harvest restrictions (Restricted Harvest, RH, vs. Unlimited Harvest, UH) and accessibility (Boat vs. Car), which correspond to a gradient of potential human activity on P. lividus in the ranked order of very low (RHBoatfar), low (RHBoatclose), moderate (RHCar) and high (UHCar). At each location, two depth ranges of 3–7 and 8–12 m were considered. At each of these depths, two areas of about 100-m2 size were chosen. The density of P. lividus was assessed in ten quadrats of 1 × 1 m, and the size of 100 individuals (test diameter) was considered. Human activity has been found to significantly affect population structure of P. lividus influencing the proportion of individuals larger than 50 mm. Although harvest was restricted by MPA regulations, a significantly lower abundance of large individuals was found at sites accessible by car. This result highlights that there is an effect of harvest restrictions in relation to accessibility and emphasizes the need to carefully address the enforcement of the MPA toward easily accessible sites. Thus, surveillance and investment in enforcement of marine reserves seem crucial points that may provide the greatest return on maintaining the ecological benefits to the fishery activities.

A new epilithic Sellaphora (Bacillariophyceae) species from a karst spring of Sardinia is described based on light and scanning electron microscopic observations. Sellaphora gologonica sp. nov. shares similarities with small-celled Sellaphora previously described from Europe and particularly with S. atomoides , S. hafnearae and S. seminulum . Sellaphora gologonica seems to be related to S. seminulum based on the striae patterns and valve ultrastructure, as well as the sinuous raphe system. The main differences between S. gologonica and S. seminulum lies in its valve shape (small, elliptic to oval), not presenting capitated nor protracted apices, as in the later taxon. Sellaphora gologonica was discovered in freshwater habitats with slightly alkaline and oligotrophic waters presenting medium hardness and mineralization, at the smaller water emergence of karst spring system Su Gologone (Sardinia).

In this study, the Land-Ocean Interactions in the Coastal Zone (LOICZ) budgeting procedure was used to evaluate the main nutrient pathways and ecosystem functions within Cabras Lagoon (Central-Western Sardinia, Italy) in 2004. The results of a simple one-box and one-layer model showed that nutrient accumulation prevailed over mobilisation for both dissolved inorganic phosphorus (annual mean of 675.69 mol d -1 ) and dissolved inorganic nitrogen (mean of 6120.05 mol d -1 ). Net ecosystem metabolism (NEM) was always positive, implying that production predominated over respiration throughout the year (mean of 3.3 mmol C m -2 d -1 ). Estimates obtained from the model also highlighted the fact that nitrogen fixation prevailed over denitrification (mean of 0.14 mmol m -2 d -1 ). Finally, extended water-residence times (mean of 192 days) were observed in the lagoon, particularly in the summer. An approach based on the improvement of water exchange with the sea would provide a relatively simple and short-term interim strategy, until more comprehensive actions aimed at reducing the anthropogenic nutrient loads in the watershed can be implemented.

In the Mediterranean region, herbivory appears to be a factor controlling the production of the endemic species Posidonia oceanica, which is mainly due to two main macroherbivores: the sea urchin Paracentrotus lividus, and the sparid fish Sarpa salpa. In this context the present study is a contribution in clarifying herbivory on P. oceanica by testing: 1) whether the abundance of grazing marks of the two herbivores is variable across different spatial scales, 2) whether spatial variation of P. lividus grazing marks and its density is consistent, 3) whether there is a dependence of the number of P. lividus grazing marks on its density, 4) whether the grazing of both macroherbivores, P. lividus and S. salpa, involves the entire leaf length, and 5) whether there is a dependence of the number of P. lividus grazing marks on the number of S. salpa grazing bites. With this aim, the density of Paracentrotus lividus was estimated at six different locations around the Gulf of Alghero (Northwestern Sardinia, Italy). At each location, two areas were considered and within each area the number of P. lividus individuals was counted in 10 plots of dimensions 1 × 1 m each. The abundance of P. lividus and Sarpa salpa grazing marks was estimated on two shoots harvested at random in each plot. The number of P. lividus individuals varied greatly among the locations and between areas within each location. A sigmoid function was found to better describe the relation between P. lividus density and the number of its grazing marks. The distance class-frequency distribution of P. lividus grazing marks from the leaf base showed that this herbivore affected the length of the Posidonia oceanica leaf for about 700 mm, and that the attacks were concentrated at the lower portion of the leaf near the base. Conversely, a larger number of the S. salpa grazing bites were more frequently seen on the higher portions of the leaves, although attacks were found along the entire length. The reported data suggest that the two herbivores share the seagrass by partitioning the portions of the leaf they consume.