Peridiniopsis niei sp nov (Dinophyceae), a new species of freshwater red tide dinoflagellates from China

A new freshwater phototrophic species of the dinoflagellate genus Peridiniopsis, P. niei sp. nov., is described based on morphology. The new species appeared during spring with densities up to 1.48 x 10(7) cells L-1 in some tributaries and gullies of Three Gorge Reservoir and Lake Donghu, China, forming red tides. Peridiniopsis niei is a cyst-producing freshwater dinoflagellate that belongs to the group Penardii. The plate tabulation is po+x+4 '+0a+6 ''+5c+5s+5 '''+2 '''' and the plate pattern is symmetric. The cells of P. niei are pentagonal in ventral view, the epitheca is larger than the hypotheca, making up about 2/3 the length of the cell. Plate 3 ' is hexangular. The closest species to P. niei is P. penardii (Lemmermann) Bourrelly, but cells of the former are pentagonal, very compressed dorsoventrally, and the hypotheca is truncated with one transparent, robust spine on each antapical plate.

Positive effects of continuous low nitrate levels on growth and photosynthesis of Alexandrium tamarense (Gonyaulacales, Dinophyceae)

The growth and photosynthesis of Alexandrium tamarense (Lebour) Balech in different nutrient conditions were investigated. Low nitrate level (0.0882 mmol/L) resulted in the highest average growth rate from day 0 to day 10 (4.58 x 10(2) cells mL(-1) d(-1)), but the lowest cell yield (5420 cells mL(-1)) in three nitrate level cultures. High nitrate-grown cells showed lower levels of chlorophyll a-specific and cell-specific light-saturated photosynthetic rate (P-m(chl a) and P-m(cell)), dark respiration rate (R-d(chl a) and R-d(cell)) and chlorophyll a-specific apparent photosynthetic efficiency (alpha(chl a)) than was seen for low nitrate-grown cells; whereas the cells became light saturated at higher irradiance at low nitrate condition. When cultures at low nitrate were supplemented with nitrate at 0.7938 mmol/L in late exponential growth phase, or with nitrate at 0.7938 mmol/L and phosphate at 0.072 mmol/L in stationary growth phase, the cell yield was drastically enhanced, a 7-9 times increase compared with non-supplemented control culture, achieving 43 540 cells mL(-1) and 52 300 cells mL(-1), respectively; however, supplementation with nitrate in the stationary growth phase or with nitrate and phosphate in the late exponential growth phase increased the cell yield by no more than 2 times. The results suggested that continuous low level of nitrate with sufficient supply of phosphate may facilitate the growth of A. tamarense.

Phylogenetic position and morphology of thecae and cysts of Scrippsiella (Dinophyceae) species in the East China Sea

Resting cysts of the marine phytoplanktonic dinoflagellate Scrippsiella spp. are encountered in coastal habitats and shallow seas all over the world. Identification of Scrippsiella species requires information on cyst morphology because the plate pattern of the flagellated cell is conserved. Cysts from sediments of the East China Sea were identified based on traits from both the cysts and the thecal patterns of germinated cells. Calcareous cysts belonged predominantly to S. trochoidea (F. Stein) A. R. Loebl., S. rotunda J. Lewis, and S. precaria Montresor et Zingone. The former two species also produced smooth and noncalcified cysts in the field. A new species, S. donghaienis H. Gu sp. nov, was obtained from six noncalcified cysts with organic spines. These cysts are spherical, full of pale white and greenish granules with a mesoepicystal archeopyle. The vegetative cells consist of a conical epitheca and a round hypotheca with a plate formula of po, x, 4', 3a, 7 '', 6c (5c + t), 6 s, 5''', 2'''' and are morphologically indistinguishable from S. trochoidea. Results of internal transcribed spacer (ITS) sequence comparisons revealed that S. donghaienis was distinct from the S. trochoidea complex and appeared nested within the Calciodinellum/Calcigonellum clade. Culture experiments showed that the presence of a red body in the cyst and the shape of the archeopyle were constant within cell lines from one generation to the next, while the morphological features of the cyst wall, such as calcification and spine shape, appeared to be phenotypically plastic.