Seasonal and spatial distributions of dinoflagellates in relation to environmental factors along the north and south coasts of Sfax (Tunisia, Eastern Mediterranean Sea)

Abstract

Objective:To compare the spatial and seasonal distribution of dinoflagellates in relation to environmental factors in north (restored) and south (not yet restored) coasts of Sfax. Methods: The present study was conducted during the year of 2010 and 2011 at 12 stations for evaluation of the spatial and seasonal distribution of dinoflagellates and abiotic parameters. Results: Results revealed a striking difference between the two coasts regarding pH with strong acidification of seawater in the south, which may be caused by industrial activity. Suspended matter was more in the north than in the south, which may be reasonably attributed to the recently added soil that has not yet fully stabilised. Inverted microscopy analysis of dinoflagellates showed 35 and 28 taxa in the north and south coasts of Sfax, respectively. Dinoflagellates developed in association with an important proliferation of common species like Gymnodinium sp., Prorocentrum lima and Prorocentrum micans. Two distinct associations of dinoflagellates species were identified: a north association involving an important abundance of Peridinium sp. and Protoperidinium sp., and a south assemblage concerning mainly Prorocentum triestinum. Chlorophyll a concentrations on the north [(2.48 ± 2.12) mg/L] and south [(4.95 ± 6.60) mg/L] coasts of Sfax were not correlated with dinoflagellates abundance, probably explained by the fact that an important number of dinoflagellates species are deprived of chloroplasts. The highest heterotrophic dinoflagellates mean abundance was recorded in south Sfax coast (1.64 × 10 2 cells/L) during summer. Conclusions: This study shows that environmental variables were in relation with the dinoflagellates community composition which exhibited clear variations over the study area.

Spatial and seasonal changes in microphytoplankton and ciliate communities in a stressed area of the southeastern Mediterranean coast (Tunisia)

“…Dinoflagellates were positively correlated to pH, TN and N/P ratio in autumn. The important abundance of dinoflagellates in autumn may be explained by their cell motility allowing them to explore different depths (Rekik et al ., 2017 a ). The abundance of dinoflagellates in such polluted situation (low pH, high nutrients) agrees with their cosmopolitan and less demanding character in terms of environmental conditions compared with other groups (Ben Salem et al ., 2015).…”

“…Several studies have been undertaken in the southern coast of Sfax regarding the spatial distribution of plankton assemblages (Rekik et al ., 2013 a , 2015 a , 2016 a , 2016 b ; Ben Salem et al ., 2015, 2016; Drira et al ., 2016) to compare the spatial and seasonal distribution of dinoflagellates and diatoms along Sfax northern and southern coasts (Rekik et al ., 2017 a , 2017 b ). The present study is the first examining the distribution of microphytoplankton and ciliates assemblage through sampling these communities simultaneously at high spatial resolution sampling in the shallow coastal waters south of Sfax during four seasons.…”

Identification of a Shewanella halifaxensis Strain with Algicidal Effects on Red Tide Dinoflagellate Prorocentrum triestinum in Culture

“…High Biomass Harmful Algal Blooms (HBHAB) are driven by a combination of abiotic and biotic factors, which creates optimal conditions for the rapid growth and/or accumulation of a particular species. Climate change may affect some of these factors, leading to increased seawater temperature and stratification and related changes in light intensity, turbulence and nutrients availability and composition [ 3 , 4 , 5 ].…”