Physico-chemical characterization of three permanent saline lakes from Oued Righ valley (Northern Sahara, North-East Algeria)

Les lacs Ayata, Mégarine et Témacine sont parmi les rares plans d’eaux salés et permanents du Sahara algérien. Il s’agit de dépressions de quelques hectares inondées par des puits artésiens creusés aux siècles derniers pour l’irrigation des palmeraies. Afin de les caractériser du point de vue physico-chimique, une analyse mensuelle de treize facteurs physico-chimiques (température, conductivité électrique, salinité, pH, oxygène dissous, NO2-, NO3-, HCO3--, Cl-, SO4-- , Na+, K+ et Ca++) a été effectuée entre août 2009 et mars 2010. Mégarine est le plus salé avec un maximum de 35,00 ± 0,28 g.L-1. Ayata et Témacine sont considérés comme saumâtres-salés. La température de l’eau est similaire dans les trois lacs et varie entre 15,70 et 34,25 °C. Le pH est alcalin et varie entre 7,23 et 8,05. L’oxygène dissous est faible avec un maximum de 4,52 mg.L-1, soit 50,51 % de saturation à Témacine. Les trois lacs sont fortement minéralisés avec une dominance des chlorures, des sulfates et du calcium. L’analyse de la matrice de corrélations linéaires de Pearson montre que la température est le principal facteur influençant les variations de la salinité, de la conductivité et de l’oxygène dissous. La salinité, plus élevée à Mégarine, est due principalement à deux sels KCl et NaCl, avec une dominance du premier. Les Cl-, SO4--, Na+ et K+ proviennent des évaporites des nappes souterraines et des sols adjacents, alors que les HCO3- proviennent de la calcite et/ou de la dolomite des nappes et des sols traversés, ainsi que d’une source biologique. Le Ca++ provient de la calcite et/ou de la dolomite. Globalement, le climat, les apports en eaux des nappes souterraines, les sols adjacents et les systèmes d’évacuation artificiels placés dans les lacs Ayata et Témacine sont les principaux facteurs contrôlant le fonctionnement physico-chimique de ces écosystèmes.Characterized by its richness in wetlands, Oued Righ valley is located in the northeast of Algerian Sahara, where most of the water resources originate from the groundwater of two aquifers: the intermediate continental (CI) and the terminal complex (CT). These wetlands are of major interest because they are considered important for food for waterbirds, and in the future, they might be potential sites for Saharan aquaculture. Little is known about the hydrology of these areas, the few existing physico-chemical investigations only concern drillings and Oued Righ channel. Here, for the first time we provide physico-chemical data of three permanent saline lakes in this region: Ayata, Mégarine and Témacine Lakes. In order to characterize them, a monthly analysis of thirteen factors (temperature, electrical conductivity, salinity, pH, dissolved oxygen, NO2-, NO3-, HCO3--, Cl-, SO4--, Na+, K+ and Ca++ ) was conducted between August 2009 and March 2010. The results show that Mégarine was the saltier with 35.00 ± 0.28 g.L-1. Ayata and Témacine are considered brackish and salty (11.56 ± 0.93 g.L-1 and 16.45 ± 0.35 g.L-1, respectively). Water temperature was similar in the three lakes and varied between 15.70 °C in winter and 34.25 °C in summer. Their pH was alkaline and between 7.23 and 8.05. Dissolved oxygen was low with a maximum of 4.52 mg.L-1 which corresponds to 50.51 % of saturation in Témacine. These lakes are highly mineralized; sulphate, chlorides and calcium were dominant. The analysis of Pearson’s linear correlation matrix shows that temperature was the main factor influencing the changes in salinity, conductivity and dissolved oxygen. The higher salinity in Mégarine was due to the two salts KCl and NaCl, with a dominance of the first. Cl-, SO4--, Na+ and K+ originated from groundwater and adjacent soil evaporates, whereas HCO3-- came from groundwater and adjacent soil calcite and /or dolomite, and from a biological source. The Ca ++ was from calcite and /or dolomite. Globally, climate, groundwater, the adjacent soils and artificial drainage systems in Ayata and Témacine were the main factors controlling the physico-chemical functioning of these ecosystems

Caractérisation physico-chimique de trois lacs salés permanents de la vallée d’Oued Righ (Sahara septentrional, Algérie Nord-Est)

Physico-chemical characterization of three permanent saline lakes from Oued Righ valley (Northern Sahara, North-East Algeria) Characterized by its richness in wetlands, Oued Righ valley is located in the northeast of Algerian Sahara, where most of the water resources originate from the groundwater of two aquifers : the intermediate continental (CI) and the terminal complex (CT). These wetlands are of major interest because they are considered important for food for waterbirds, and in the future, they might be potential sites for Saharan aquaculture. Little is known about the hydrology of these areas, the few existing physico-chemical investigations only concern drillings and Oued Righ channel. Here, for the first time we provide physico-chemical data of three permanent saline lakes in this region : Ayata, Mégarine and Témacine Lakes. In order to characterize them, a monthly analysis of thirteen factors (temperature, electrical conductivity, salinity, pH, dissolved oxygen,NO2-, NO3-, HCO3--, Cl-, SO4--, Na+, K+ and Ca++) was conducted between August 2009 and March 2010. The results show that Mégarine was the saltier with 35.00 ± 0.28 g. L-1. Ayata and Témacine are considered brackish and salty (11.56 ± 0.93 g. L-1 and 16.45 ± 0.35 g. L-1, respectively). Water temperature was similar in the three lakes and varied between 15.70 ° C in winter and 34.25 ° C in summer. Their pH was alkaline and between 7.23 and 8.05. Dissolved oxygen was low with a maximum of 4.52 mg. L-1 which corresponds to 50.51 % of saturation in Témacine. These lakes are highly mineralized ; sulphate, chlorides and calcium were dominant. The analysis of Pearson’s linear correlation matrix shows that temperature was the main factor influencing the changes in salinity, conductivity and dissolved oxygen. The higher salinity in Mégarine was due to the two salts KCl and NaCl, with a dominance of the first. Cl-, SO4--, Na+ and K+ originated from groundwater and adjacent soil evaporates, whereas HCO3-- came from groundwater and adjacent soil calcite and / or dolomite, and from a biological source. The Ca ++ was from calcite and / or dolomite. Globally, climate, groundwater, the adjacent soils and artificial drainage systems in Ayata and Témacine were the main factors controlling the physico-chemical functioning of these ecosystems.Les lacs Ayata, Mégarine et Témacine sont parmi les rares plans d’eaux salés et permanents du Sahara algérien. Il s’agit de dépressions de quelques hectares inondées par des puits artésiens creusés aux siècles derniers pour l’irrigation des palmeraies. Afin de les caractériser du point de vue physico-chimique, une analyse mensuelle de treize facteurs physico-chimiques (température, conductivité électrique, salinité, pH, oxygène dissous, NO2-, NO3-, HCO3--, Cl-, SO4--, Na+, K+ and Ca++) a été effectuée entre août 2009 et mars 2010. Mégarine est le plus salé avec un maximum de 35,00 ± 0,28 g. L-1. Ayata et Témacine sont considérés comme saumâtres-salés. La température de l’eau est similaire dans les trois lacs et varie entre 15,70 et 34,25 ° C. Le pH est alcalin et varie entre 7,23 et 8,05. L’oxygène dissous est faible avec un maximum de 4,52 mg. L-1, soit 50,51 % de saturation à Témacine. Les trois lacs sont fortement minéralisés avec une dominance des chlorures, des sulfates et du calcium. L’analyse de la matrice de corrélations linéaires de Pearson montre que la température est le principal facteur influençant les variations de la salinité, de la conductivité et de l’oxygène dissous. La salinité, plus élevée à Mégarine, est due principalement à deux sels KCl et NaCl, avec une dominance du premier. Les Cl-, SO4--, Na+ et K+ proviennent des évaporites des nappes souterraines et des sols adjacents, alors que les HCO3- proviennent de la calcite et/ ou de la dolomite des nappes et des sols traversés, ainsi que d’une source biologique. Le Ca++ provient de la calcite et/ ou de la dolomite. Globalement, le climat, les apports en eaux des nappes souterraines, les sols adjacents et les systèmes d’évacuation artificiels placés dans les lacs Ayata et Témacine sont les principaux facteurs contrôlant le fonctionnement physico-chimique de ces écosystèmes.Gouasmia Ghouzala, Amarouayache Mounia, Frihi Hocine, Kara Mohamed Hichem. Caractérisation physico-chimique de trois lacs salés permanents de la vallée d’Oued Righ (Sahara septentrional, Algérie Nord-Est). In: Revue d'Écologie (La Terre et La Vie), tome 71, n°4, 2016. pp. 330-341

Relationships between environmental conditions and phytoplankton in the Mellah lagoon (South Western Mediterranean, Algeria), with an emphasis on HABs species

For the first time, a bi-monthly monitoring of environmental parameters (temperature, salinity, nutrients) and phytoplankton assemblages was conducted in the well-preserved Mellah lagoon ecosystem (South Western Mediterranean, Algeria). Sampling was performed at 3 stations in 2016. The objective was to study the evolution of the microphytoplankton community with a focus on HABs species in relation with the environmental characteristics. In total, 227 microphytoplankton species belonging mainly to Diatomophyceae (160 species) and Dinophyceae (53 species), were inventoried in the Mellah lagoon. There was a clear dominance of diatoms (63%), compared to dinoflagellates (37%). Proliferations of some potentially toxic species such as Prorocentrum micans (7 200 cells.l-1) and Gymnodinium sanguineum (6 000 cells.l-1), were observed in summer and autumn respectively. Other HABs species as Alexandrium tamarense/catenella (1 350 cells.l-1) and Alexandrium minutum (1 420 cells.l-1), were present in winter and spring respectively. Temporal differences in the qualitative composition and quantitative phytoplankton communities in the three stations are discussed in relation with environmental variables. Microphytoplankton populations in the Mellah show diversity and equitability indices of 3.04 bits.cell-1 and 0.94 respectively, showing a structured community during winter and spring. The rest of the year is characterized by unstable phytoplankton populations, where only opportunistic species develop

Relationships between environmental conditions and phytoplankton in the Mellah lagoon (south western Mediterranean, Algeria), with an emphasis on HAB species

peer reviewedA bi-weekly monitoring of environmental parameters and microphytoplankton assemblages was conducted in the well-preserved Mellah lagoon ecosystem (south western Mediterranean). Sampling was performed at 3 stations in 2016. We aimed to study the evolution of the phytoplankton community with a focus on harmful species in relation with the environmental characteristics. Phytoplankton of Mellah Lagoon was characterized by a mixture of marine, brackish-water and freshwater taxa. In all of the stations, 227 species of phytoplankton were identified (160 diatoms and 53 dinoflagellates). The overall mean phytoplankton abundance was higher at station A (2.24·105 cells l-1, early September) and B (2.98·105 cells l-1, early October) near of marine inputs, compared to station C (1.73·105 cells l-1, early June) located in the south of the lagoon. Diatoms dominated in spring and dinoflagellates developed in summer and early autumn in the Mellah. The dynamic of the phytoplankton in Mellah was influenced by temperature and salinity. For the first time, a number of potentially toxic species have been identified, including 2 diatom species: Pseudo-nitzschia delicatissima-group (max.: 2.52·103 cells l-1), Pseudo-nitzschia seriata-group (max.: 700 cells l-1) and 6 dinoflagellate species: Alexandrium minutum (max.: 1.42·103 cells l-1), Alexandrium tamarense/catenella (max.: 1.35·103 cells l-1), Dinophysis acuminata (max.: 180 cells l-1), Dinophysis sacculus (max.: 120 cells l-1), Akashiwo sanguinea (max.: 7.20·103 cells l-1), Prorocentrum lima (max.: 110 cells l-1). Even the abundances of the HABs species were relatively low in Mellah lagoon, they could potentially form blooms in the coming decades at the favor of warming and trophic status changes observed in Mediterranean marine systems. Monitoring program of HABs species must be established to gain more insight in the development of potentially toxic species and the toxins produce

Distribution of dinoflagellate cyst assemblages in recent sediments from a southern Mediterranean lagoon (Mellah, Algeria) with emphasis on toxic species

Place: Heidelberg Publisher: Springer Heidelberg WOS:000529493300024This is the first study on the dinoflagellate cysts in Algerian waters and in Mellah Lagoon (South Western Mediterranean), located within a protected reserve. In total, 42 species of dinocysts belonging to 7 orders, 12 families and 23 genera, were identified in the 26 superficial sediment samples from Mellah Lagoon. The distribution of dinocysts in the sediment of this lagoon is heterogeneous. Indeed, their abundance oscillates between 1 and 315 cysts g(-1) dry sediment (DS). Cyst morphotype assemblages were dominated by a few numbers of species: Alexandrium minutum (15.87%), Gonyaulax verior (9.81%), Protoperidinium spp. (7.74%), Alexandrium affine (7.05%), Scrippsiella trochoidea (6.67%), and Alexandrium pseudogonyaulax (6.19%). There is a positive correlation between the density of cysts and the depth (r = 0.61; p \textless 0.05), organic matter (r = 0.70; p \textless 0.05), water content (r = 0.71; p \textless 0.05), and the fine fraction of sediment (r = 0.74; p \textless 0.05). Surprisingly, although the Mellah Lagoon is almost semi-closed, it holds an important specific richness in dinocysts (42 species) higher than others observed in Mediterranean lagoons. However, cyst abundances are low compared to other lagoons in the Mediterranean Sea. Finally, the presence of dinocysts of Alexandrium catenella/tamarense, A. minutum, and Gymnodinium catenatum associated to paralytic shellfish toxins, A. pseudogonyaulax which produces goniodomin A, also Protoceratium reticulatum and Gonyaulax spinifera complex which produce yessotoxins, needs to implement a monitoring program to prevent a potential human intoxication due to the consumption of contaminated sea products by these potent neurotoxins

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.LAGUNOTOX research projec

Insights into the species diversity of the genus Sargassum (Phaeophyceae) in the Mediterranean Sea, with a focus on a previously unnoticed taxon from Algeria

International audienceNine currently accepted species of the genus Sargassum (Phaeophyceae) have been recorded from the Mediterranean Sea: S. acinarium, S. desfontainesii, S. flavifolium, S. furcatum, S. hornschuchii, S. muticum, S. ramentaceum, S. trichocarpum and S. vulgare. Two of them, S. desfontainesii and S. furcatum, are Atlantic species, the Mediterranean range of which is restricted to the Alboran Sea, close to the Strait of Gibraltar. Three species, S. hornschuchii, S. ramentaceum and S. trichocarpum are endemic to the Mediterranean. The presence of S. flavifolium in the Mediterranean, a north-eastern Atlantic species, is at least in part based upon a misidentification and therefore requires confirmation. A taxon collected near Algiers and Annaba (Algeria), here referred to as ‘Sargassum sp. from Algeria’, although sharing most characters with S. flavifolium, also presents some distinctive characters. In the absence of genetic data, confirming or not its taxonomic value, and in the lack of studies on the herbaria containing the types of many species currently considered as synonyms of S. flavifolium, but which are possible candidates for accommodating the Algerian specimens, the authors prefer a conservative approach. They do not describe a new species, which would be premature, but draw attention to a taxon which may be more widely distributed in the Mediterranean rather than solely along the Algerian coasts

Unsuspected intraspecific variability in the toxin production, growth and morphology of the dinoflagellate Alexandrium pacificum R.W. Litaker (Group IV) blooming in a South Western Mediterranean marine ecosystem, Annaba Bay (Algeria)

Physiological plasticity gives HABs species the ability to respond to variations in the surrounding environment. The aim of this study was to examine morphological and physiological variability in Alexandrium pacificum R.W. Litaker (Group IV) (former Alexandrium catenella) blooming in Annaba bay, Algeria. Monoclonal cultures of up to 30 strains of this neurotoxic dinoflagellate were established by the germination of single resting cysts from the surface sediment of this southern Mediterranean marine ecosystem. Ribotyping confirmed formally for the first time that A. pacificum is developing in Eastern Algerian waters. Toxin analyses of A. pacificum strains revealed substantial intraspecific variability in both the profile and toxin amount. However, the toxin profile of most strains is characterized by the dominance of GTX6 (up to 96 mol %) which is the less toxic paralytic molecule. The toxin concentrations in the isolated strains varied widely between 3.8 and 30.82 fmol cell−1. We observed an important variation in the growth rate of the studied A. pacificum strains with values ranging from 0.05 to 0.33 d−1. The lag time of the studied strains varied widely and ranged from 4 to 20 days. The intraspecific diversity could be a response to the selection pressure which may be exerted by different environmental conditions over time and which can be genetically and in turn physiologically expressed. This study highlights, for the first time, that the sediment of a limited area holds an important diversity of A. pacificum cysts which give when germinate populations with noticeable physiological plasticity. Consequently, this diversified natural populations allow an exceptional adaptation to specific environmental conditions to outcompete local microalgae and to establish HABs which could explain why this dinoflagellate is successful and expanding worldwide