Temperature and daylength regulate encystment in calcareous cyst-forming dinoflagellates

Abstract

We tested the effect of temperature (15, 20, and 25°C), daylength (8:16, 12:12 and 16:8 h light:dark cycles), and culture medium (K/5 and K/50) conditions on cyst production in batch cultures of 4 dinoflagellate species that form calcareous resting stages (Scrippsiella trochoidea var. aciculifera, Pentapharsodinium tyrrhenicum, Calciodinellum operosum and S. rotunda). The 4 species showed different encystment patterns at the temperature conditions tested; cyst production was inversely related to daylength conditions, and higher cyst yields were obtained with the less concentrated growth medium. Experiments with semi-continuous cultures of S. rotunda, in which nutrient concentration was kept within values comparable to in situ concentrations, were carried out with the aim of decoupling the effect of nutrient depletion on cyst production from that of daylength. Cyst production in this species, kept at a constant growth rate in non-depleted nutrient conditions, was only obtained at the shortest daylengths, thus supporting the role of short daylength in inducing the production of calcareous cysts. Our data suggest that encystment in the 4 species is regulated by a complex interplay of at least 3 factors: daylength, temperature and nutrient concentration. These results contribute to explain the timing of resting-stage production at sea, and point to the possible role of daylength as an environmental signal for the regulation of life cycles in dinoflagellates.

Encystment probability and encystment rate: new terms to quantitatively describe formation of resting cysts in planktonic microbial populations

“…In many cases special nutrientdeplete 'encystment media' have been used to produce resting cysts of dinoflagellates, but final encystment percentages remain modest, usually < 40% (Dale 1983, Anderson & Lindquist 1985, Binder & Anderson 1987, Lirdwitayaprasit et al 1990, Park & Hayashi 1993, Montresor & Marino 1996. Recently, cyst yields up to 100% have been reported (Sgrosso et al 2001, Olli & Anderson 2002. However, in the literature one can find more than 1 formula for calculating cyst yield (using data on vegetative cell population and cysts produced), and some authors do not report how they have calculated their data.…”

Dinoflagellate cysts production in the north-western Adriatic Sea

“…Cysts of Scrippsiella trochoidea are reported as dominant in almost all surveys of coastal areas over a broad latitudinal range (Giannakourou et al, 2005;Wang et al, 2007;Pitcher & Joyce, 2009;Shin et al, 2012). This could be explained considering that Scrippsiella trochoidea-like dinoflagellates are rather abundant in the plankton and that they have relatively high encystment rates (e.g., Sgrosso et al, 2001, Wang et. al., 2007.…”

“…However, field and laboratory studies could not always find a link between cyst production and nutrient limitation (Anderson et al, 1983;Zonneveld et al, 2009). Other factors, such as day length (Sgrosso et al, 2001), temperature shifts (Kremp et al, 2009), a combination of these factors (Pospelova et al, 2010) or, in heterotrophic species, food limitation (Nagai et al, 2002;Saito et al, 2007) might trigger or modulate the formation of resting cysts.…”

Effects of deposit-feeder gut passage and fecal pellet encapsulation on germination of dinoflagellate resting cysts

“…Anderson et al 1982, Binder & Anderson 1987, Blanco 1995, Rengefors & Anderson 1998, Nuzzo & Montresor 1999, Sgrosso et al 2001. The time interval in the sediment and the conditions experienced there by the cysts have received little attention with respect to possible effects on germination and seeding, although many dinoflagellates spend considerably more time as benthic resting cysts in the sediment than as planktonic cells in the water column.…”