Distribution of picophytoplankton communities from brackish to hypersaline waters in a South Australian coastal lagoon

Abstract

BackgroundPicophytoplankton (i.e. cyanobacteria and pico-eukaryotes) are abundant and ecologically critical components of the autotrophic communities in the pelagic realm. These micro-organisms colonized a variety of extreme environments including high salinity waters. However, the distribution of these organisms along strong salinity gradient has barely been investigated. The abundance and community structure of cyanobacteria and pico-eukaryotes were investigated along a natural continuous salinity gradient (1.8% to 15.5%) using flow cytometry.ResultsHighest picophytoplankton abundances were recorded under salinity conditions ranging between 8.0% and 11.0% (1.3 × 106 to 1.4 × 106 cells ml-1). Two populations of picocyanobacteria (likely Synechococcus and Prochlorococcus) and 5 distinct populations of pico-eukaryotes were identified along the salinity gradient. The picophytoplankton cytometric-richness decreased with salinity and the most cytometrically diversified community (4 to 7 populations) was observed in the brackish-marine part of the lagoon (i.e. salinity below 3.5%). One population of pico-eukaryote dominated the community throughout the salinity gradient and was responsible for the bloom observed between 8.0% and 11.0%. Finally only this halotolerant population and Prochlorococcus-like picocyanobacteria were identified in hypersaline waters (i.e. above 14.0%). Salinity was identified as the main factor structuring the distribution of picophytoplankton along the lagoon. However, nutritive conditions, viral lysis and microzooplankton grazing are also suggested as potentially important players in controlling the abundance and diversity of picophytoplankton along the lagoon.ConclusionsThe complex patterns described here represent the first observation of picophytoplankton dynamics along a continuous gradient where salinity increases from 1.8% to 15.5%. This result provides new insight into the distribution of pico-autotrophic organisms along strong salinity gradients and allows for a better understanding of the overall pelagic functioning in saline systems which is critical for the management of these precious and climatically-stress ecosystems.

Picophytoplankton predominance in hypersaline lakes (Transylvanian Basin, Romania)

“…In comparison, a picocyanobacterium strain isolated from the same lake had lower salinity tolerance (growing from 0% to 10% salinity with a maximum specific growth rate at 3% and a minimum at 8%) than Picocystis (Budinoff and Hollibaugh 2007). The higher salinity tolerance of EuPPP could explain their success in waters of higher salinity, as was observed in lagoon and solar saltern systems (Elloumi et al 2009;Schapira et al 2010), in agreement with the present study.…”

“…), where the salinity of the mixolimnion ranged between 19 and 21%, PPP was barely found. Similar results were obtained in a coastal lagoon system, where the environmental variable that best explained the picophytoplankton abundance pattern along the lagoon was salinity (Schapira et al 2010). According to Schapira et al (2010), CyPPP was mainly abundant below 3% salinity, while at salinities ranging from 4.5% to 14.0% the PPP was dominated by EuPPP.…”

“…Similar results were obtained in a coastal lagoon system, where the environmental variable that best explained the picophytoplankton abundance pattern along the lagoon was salinity (Schapira et al 2010). According to Schapira et al (2010), CyPPP was mainly abundant below 3% salinity, while at salinities ranging from 4.5% to 14.0% the PPP was dominated by EuPPP. However, at salinity values greater than 14.0%, the community shifted into a Prochlorococcus-like population (Schapira et al 2010).…”

“…According to Schapira et al (2010), CyPPP was mainly abundant below 3% salinity, while at salinities ranging from 4.5% to 14.0% the PPP was dominated by EuPPP. However, at salinity values greater than 14.0%, the community shifted into a Prochlorococcus-like population (Schapira et al 2010). In a solar saltern system (Tunesia), the PPP was exclusively composed of EuPPP with maximum abundances between 7.9 and 19% salinity (Elloumi et al 2009).…”

Light Absorption by Phytoplankton in the Upper Mixed Layer of the Black Sea: Seasonality and Parametrization

“…Cells were sized and its volumes were assessed using geometrical figures (sphere, ellipsoid or cylinder) corresponding to the cell shapes. Phytoplankton analysis was conducted only at selected stations in August 2011, September 2014and December 2014, 2015 In August 2011, September 2014 and December 2014, 2015 flow cytometric analysis was performed by flow cytometer Cytomics FC 500 (Beckman Coulter, USA) equipped with a single-phase argon laser (488 nm) (Marie et al, 1999;Schapira et al, 2010). For all detected particles phycoerythrin fluorescence emission (575 nm), and chlorophyll fluorescence emission (675 nm) were measured.…”