Variability patterns of epibenthic microalgae in eastern Tunisian coasts

Abstract

Summary: Epiphytic microalgae were monitored on various substrates of seagrass and macroalgae and in the water column for one year (from March 2013 to March 2014) in Oued Lafrann along the eastern coast of Chebba (Tunisia) with a focus on the distribution patterns of the epibenthic toxic dinoflagellates Ostreopsis cf. ovata, Prorocentrum lima and Coolia monotis. Microalgae assemblages were dominated by diatoms and dinoflagellates both in the water column and on vegetation. High concentrations of epiphytic toxic and potentially toxic dinoflagellates were preferentially hosted by Posidonia leaves, mainly in the apical and middle regions of the leaves, and P. lima was the dominant species. A significant positive correlation was found between P. lima concentrations on Posidonia and in the water column, suggesting that macrophytes should be sampled in the framework of harmful algal species monitoring. Ostreopsis cf. ovata, exhibited low concentrations and was mainly present on the inner surface of the Posidonia leaf, whereas P. lima was mainly present on the outer surface of the leaf, suggesting a likely space competition.Keywords: Prorocentrum lima; Ostreopsis cf. ovata; Coolia monotis; Prorocentrum micans; magnoliophytes; macroalgae. Patrones de variabilidad de las microalgas epibentónicas en la costa este tunecinaResumen: Las microalgas epifitas fueron monitorizadas en varios sustratos de praderas marinas, macroalgas y en la columna de agua durante un año (de marzo 2013 hasta marzo 2014) en Oued Lafrann, en la costa este de Chebba (Túnez), con especial atención a la distribución de dinoflagelados tóxicos epibénicos, como Ostreopsis cf. ovata, Prorocentrum lima y Coolia monotis. Las comunidades de microalgas estaban dominadas por diatomeas y dinoflagelados, tanto en la columna de agua como en la vegetación. Se encontraron elevadas concentraciones de dinoflagelados epífitos tóxicos preferentemente en las hojas de Posidonia, principalmente en las regiones apicales y media y Prorocentrum lima fue la especie epífita dominante. Se observó una correlación positiva significativa entre las concentraciones de P. lima en Posidonia y en la columna de agua, lo que sugiere el muestreo de esta macrófita como parte de la monitorización de especies nocivas. Las células de Ostreopsis cf. ovata mostraron concentraciones bajas y se encontraron principalmente en la superficie interior de la hoja de Posidonia contrariamente a la distribución de P. lima presente principalmente en la superficie exterior de la lámina. Este hecho probablemente sugiere una competencia espacial entre los dos microalgas tóxicas.

Characterization of Coolia spp. (Gonyaucales, Dinophyceae) from Southern Tunisia: first record of Coolia malayensis in the Mediterranean Sea

“…In our study area, the Gulf of Gabès (Fig. 1), located in the South-eastern Mediterranean Sea (Southeast of Tunisia) and sheltering Kerkennah and Djerba islands and Boughrara and El Bibane lagoons, C. monotis has been recorded in the water column (Abdennadher et al 2020), attached to the sediment and the adjacent water "biofilm" (Loukil-Baklouti et al 2018) and on various substrates (magnoliophytes and macroalgae) (Moncer et al 2017).…”

Multiannual trends of toxic and potentially toxic microalgae (Ostreopsis cf. ovata, Prorocentrum lima, and Coolia monotis) in Sfax coasts (North of Gabes Gulf, Tunisia)

“…The movement of the water can thus cause a stirring of the leaves allowing the displacement of the epiphyte species in the water column and that can explain their frequent observations in REPHY samples. (Moncer et al, 2017) reported that concentrations of P. lima on Posidonia oceanica leaves and in water column were significantly correlated. (Richlen & Lobel, 2011) suggested that the species, being a swimming dinoflagellate that can even be affected by low water motion conditions, might move from one compartment to another.…”

“…ovata, P. lima, and C. monotis in the north of Sfax coasts (Chebba) in different compartments (seagrasses, macroalgae, and water column). A significant resuspension of these species from macrophytes to water column was noted (Boisnoir et al, 2019;Mangialajo et al, 2017;Moncer et al, 2017). Otherwise, (Loukil et al, 2017) showed that the presence of potentially toxic species within the shellfish could originate from the sediment or the biofilm.…”

Factors regulating primary producers' assemblages in Posidonia oceanica (L.) Delile ecosystems over the past 1800 years

“…In general, modern macroalgal species are characteristically composed mainly of calcareous Rhodophyta and non-calcified Ochrophyta, whereas microalgal epiphytes usually include diatoms, dinoflagellates and cyanobacteria in declining relative abundance (Piazzi et al, 2016;Agawin et al, 2017). Similarly, the modern phytoplankton assemblages are mainly composed of diatoms and dinoflagellates (Moncer et al, 2017), while the water column near Cabrera is known to harbour a great abundance of pico and nanoplankton, dinoflagellates, coccolitophorids and diatoms (Vives, 1993). We suggest that seagrass, possibly in association with rhodophytes, is the main source of the couplet lutein-zeaxanthin, as it is the most abundant carotenoid in live P. oceanica tissues (Casazza & Mazella, 2002).…”