Eco-fingerprinting of the dinoflagellate Borghiella dodgei: experimental evidence of a specific environmental niche

Abstract

In Lake Tovel, an oligotrophic and weakly stratified lake, the dinoflagellate Borghiella dodgei Moestrup, Hansen et Daugbjerg, showed a peculiar spatial-temporal pattern with highest abundances in the bottom of the shallow side bay (4 m) along with remarkable abundance variations fromyear to year. We investigated B. dodgei's growth in laboratory cultures and related results to their implication for bloom formation. B. dodgei was cultivated under different temperature, nutrient and light conditions. Growth rates, cell biovolume, cyst formation and pigment and mycosporine-like amino acids (MAAs) concentrations were determined. Experiments showed that this alga (i) had higher growth rates at low temperatures (\7°C) and high irradiance levels (*250 lmol m -2 s -1 ), (ii) produced higher yields with organic supplements such as peptone, (iii) did not grow in the dark even with organic supplements, (iv) survived for long periods without a light source, (v) synthesised MAAs, (vi) showed an increase in cell volume with nutrient shortage and increasing temperatures ([7°C) and (vii) had high encystment rates with temperatures [7°C. These laboratory fingerprints allowed us to construct a theoretical model defining the species' niche. Borghiella needed a mixture of low temperatures, high irradiance levels and sufficient quantities of dissolved organic nitrogen to form blooms. Such a strict combination was probably a transient situation and occurred in oligotrophic Lake Tovel only in early summers followed by heavy spring rains.

Spatial and temporal variations of Dinophyceae in subtropical reservoirs in southern Brazil

“…Furthermore, the lake has low dissolved organic carbon (DOC) concentrations (\1 mg l -1 ), and any additional organic input could be an important factor for growth. In the presence of organic nitrogen sources, blooms occurring in rainy springs supported the hypothesis that organic nitrogen triggered bloom formation (Flaim et al, 2010). Indeed, the diversity and biomass found in this study were inversely correlated to turbidity and nitrogen, respectively, but P. umbonatum var.…”

“…In shallow lakes (eight) and wetlands (four) in the subtropical part of Brazil, 11 taxa were identified (Cardoso & Torgan, 2007). Researches focused on strategies involved in bloom formation such as life cycle characteristics and production of secondary metabolites as conducted by Flaim et al (2010), where experiments were combined with a monitoring program. This could point to specific environmental (physical and chemical, hydrological, and land use) and/or biotic factors driving the distribution of dinoflagellates.…”

“…During 2003-2005, a large multidisciplinary project was initiated, which focused on the causes of the disappearance of the reddening of Lake Tovel (Hansen & Flaim, 2007), almost 40 years after the ending of blooms. Detailed taxonomic studies of the dinoflagellates had never been made in this region before, and it turned out to represent at least three different species which in the past promoted blooms mistakenly attributed to G. sanguineum (Moestrup et al, 2006;Hansen & Flaim, 2007;Flaim et al, 2010).…”

“…Their life strategies may correlate with a certain degree of heterotrophy and the development of defense mechanisms against grazers or predators (Margalef, 1978). Mixotrophy is a common strategy in oligotrophic environments, and in Lake Tovel, some dinoflagellates also have phagotrophic mixotrophic feeding mechanisms representing an ecological advantage by integrating photo-autotrophic growth (Flaim et al, 2010). Furthermore, the lake has low dissolved organic carbon (DOC) concentrations (\1 mg l -1 ), and any additional organic input could be an important factor for growth.…”

Blowing in the wind: how many roads can a phytoplanktont walk down? A synthesis on phytoplankton biogeography and spatial processes

“…As reviewed by Padisák et al (this volume), genetic tools or analyses of secondary metabolites of different strains of the same species may help to disclose migration patterns, especially when there is a lack of reliable historical floristic records. Exploring physiological fingerprints of peculiar species, for example, Borghiella dodgei Moestrup, Hansen et Daugbjerg, has been a great help in understanding geographic distributions (Flaim et al, 2010). Indeed, some lakes, like Lake Tovel in the southern high Alps (Cellamare et al, this volume) seem to be a collector of rare species with remarkable geographic distributions and physiological adaptations.…”