Distribution, production, and ecophysiology of Picocystis strain ML in Mono Lake, California

Abstract

A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California, occupies a niche that spans two environments: the upper oxic mixolimnion and the deeper anoxic and highly reducing monimolimnion. This organism, Picocystis sp. strain ML, accounts for nearly 25% of the primary production during the winter bloom and more than 50% at other times of the year. In incubations, it is heavily grazed by the brine shrimp, Artemia monica. We assessed growth and photosynthetic parameters over broad ranges of irradiance, salinity, and pH and under oxic and anoxic conditions. Picocystis appears to be particularly adapted to low irradiance; we observed an order of magnitude increase in the cellular pigment concentrations, as well as marked increases in cellspecific photosynthetic parameters for cells acclimated to low-growth irradiance. Growth rates of 0.3-1.5 d Ϫ1 were observed over a salinity range of 0-260‰ and a pH range of 4-12, with maximal growth at ϳ50 mol photons m Ϫ2 s Ϫ1 , 40‰, and pH 6-10. Growth and oxygenic photosynthesis were observed under anoxic conditions at rates comparable to those measured under oxic conditions. The ability of the organism to acclimate and grow under such a broad range of environmental conditions makes it an important component of the Mono Lake ecosystem and likely contributes to its dominance of the monimolimnion/mixolimnion interface.Phototrophic microorganisms exhibit a remarkable capability for adaptation and acclimation that allows them to inhabit niches representing temporally varying biological extremes of light, salinity, pH, and water potential (Gorbushina and Krumbein 1999). In aquatic environments, phytoplankton undergo large increases in cellular pigment concentra-1 To whom correspondence should be addressed. Present address: Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine 04575 (croesler@bigelow.org).2 Present address: District Office, USGS, Augusta, Maine 04330. AcknowledgmentsThe authors thank Jennifer Simeon for culturing assistance, Victor Paganelli (USGS Menlo Park) for processing the total dissolved inorganic carbon samples, and members of the Sierra Nevada Aquatic Research Laboratory for collecting water samples from Mono Lake. The University of Connecticut supported C.S.R. and S.M.E.; the USGS National Research Program supported C.W.C., L.G.M., and R.S.O.; and NSF supported R.P.K. (OCE-9907471).

Diversity and oceanic distribution of prasinophytes clade VII, the dominant group of green algae in oceanic waters

“…A and B are clearly marine lineages with sequences and strains recovered only from marine environments. On the other hand, lineage C (encompassing the only formally described species Picocystis salinarum) has been found in inland saline lakes (Hollibaugh et al, 2001;Roesler et al, 2002;Krienitz et al, 2012) or ponds (Lewin et al, 2000) where it was originally isolated. Thus, Picocystis seems to be a prasinophyte typical Diversity and distribution of oceanic prasinophytes A Lopes dos Santos et al of inland saline waters rather than marine with a very restricted ecological range of habitats, as evidenced by the absence of similar sequences in the Tara and OSD data sets.…”

“…Prasinophytes clade VII are naked coccoid cells ranging in size from 2 to 5 μm with no specific morphological feature and remain without formal description, despite the fact that they have been in culture since 1965 (Potter et al, 1997). Previous phylogenetic analysis of the 18S rRNA gene divided this group into three wellsupported lineage, A, B and C , the latter formed by Picocystis salinarum only, a small species found in saline lakes (Lewin et al, 2000;Roesler et al, 2002;Krienitz et al, 2012). Strains from lineages A and B harbor very similar set of photosynthetic pigments in contrast with those from lineage C (Lewin et al, 2000;Lopes dos Santos et al, 2016).…”

Spatial and temporal variability of prokaryotes, viruses, and viral infections of prokaryotes in an alkaline, hypersaline lake

“…Artemia monica are not generally found in the anoxic waters (Lenz et al 1986), which allows the unicellular alga Picocystis sp. strain ML (Roesler et al 2002) -capable of growth under anoxic or oxic conditions -to persist in the monimolimnion during the summer. Decline of A. monica at the end of summer is then followed by a fall bloom of phytoplankton ).…”

Ecophysiology of a Mono Lake picocyanobacterium

“…Phytoplankton productivity is high (350 to .1,000 g C m 22 yr 21 ) with marked seasonal cycles of abundance Melack 1988, 1993a;Roesler et al 2002). Eukaryotic algae are abundant throughout the winter, and their biomass increases substantially in spring as the thermocline stabilizes.…”