Composition and dynamics of potentially toxic dinoflagellates in a shallow Mediterranean lagoon

Abstract

The population dynamics of harmful microalgae was investigated in the semi-enclosed shallow lagoon, Tunis northern lagoon (South Mediterranean), during a 1-year period from January to December 2007. A total number of 16 potentially toxic dinoflagellates were identified. Density of each species was analyzed in time and space and in relation to environmental parameters. Some species such as Alexandrium catenella, A. pseudogonyaulax, A. tamarense concavum were detected in this coastal ecosystem, but they were rare or appeared in very low densities.Densities of the most abundant species were closely associated with spring and summer conditions, being positively correlated with water temperature and salinity. These species performed well in this lagoon, but the specific species-dependent affinity to each of the environment factors determined which organisms proliferated. The spatial distribution of the abundant species exhibited a marked increase towards the western and southern parts of the lagoon represented by sites C, D and E. Examination of the temporal distribution revealed that the species more prone to bloom are those with extensive spatial distribution and frequent presence throughout the year such as D. sacculus.Statistical analysis of D. sacculus density dynamics showed a significant difference between summer and winter assemblages. It presented a positive correlation with water temperature and salinity, but it seems to be tolerant to all levels of nutrients.

Influence of Phosphorus-Contaminated Sediments in the Abundance of Potentially Toxic Phytoplankton Along the Sfax Coasts (Gulf of Gabes, Tunisia)

“…Thus, the effect of salinity on toxic species might not be a direct cause-and-effect relationship but might involve temperature as the main driving parameter. Similar results were also found in Tunisian waters (Aissaoui et al, 2014;Armi et al, 2012) and in other Mediterranean and northeast Atlantic ecosystems, for instance, along the Greek coast (Aligizaki et al, 2009) and the French Atlantic and English Channel coasts (Husson et al, 2016).…”

“…Similar findings on the correlation with the temperature were found in Bizerte lagoon (Sahraoui et al, 2013), in the Gulf of Tunis (Aissaouiet al, 2014) and in the western Adriatic (Ingarao et al, 2009). Furthermore, P. lima was reported in several Mediterranean ecosystems during August in the Gulf of Tunis (Turki, 2005) and in the Tunis northern lagoon during spring and summer seasons (Armi et al, 2012).…”

Effects of N and P availability on carbon allocation in the toxic dinoflagellate Ostreopsis cf. ovata

“…Field and laboratory studies on the toxic dinoflagellate Ostreopsis cf. ovata have increased substantially in the last years, concomitantly to the spread of its blooms (Zina et al, 2012;Cohu et al, 2013;Casabianca et al, 2014;Escalera et al, 2014;Selina et al, 2014;Accoroni et al, 2015;Brissard et al, 2015). Attention has been posed to the development of rapid and valuable methods for the detection of toxins produced by this species (Ciminiello et al, 2010;Ciminiello et al, 2015;Garcı `a Altares et al, 2015), named isobaric palytoxin (isoPLTX) and ovatoxins (OVTXs), leading to the on going identification of new analogs in algal extracts (Brissard et al, 2015;Garcı `a Altares et al, 2015).…”

Inorganic nitrogen addition in a semi-intensive turbot larval aquaculture system: effects on phytoplankton and zooplankton composition

“…Interactive effects of temperature, salinity, water column stability and nutrient availability determine presence of dinoflagellates (Anderson et al . ; Glibert, Burkholder & Kana ; Zina, Elbahri, Souad, Naceur & Ezzeddine ), which develop well under such conditions (Yoo ), whereas some species occasionally form toxic blooms.…”

“…Different species can tolerate and grow at different pH levels (Hansen, Lundholm & Rost 2007;Berge, Daugbjerg & Hansen 2012), and pH is a driver in the phytoplankton species succession (Hansen 2002;Rost, Richter, Riebesell & Hansen 2006). Interactive effects of temperature, salinity, water column stability and nutrient availability determine presence of dinoflagellates (Anderson et al 2002;Glibert, Burkholder & Kana 2012;Zina, Elbahri, Souad, Naceur & Ezzeddine 2012), which develop well under such conditions (Yoo 1991), whereas some species occasionally form toxic blooms.…”