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

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

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