Influence of Nutrient Stress on the Relationships between PAM Measurements and Carbon Incorporation in Four Phytoplankton Species

International audienc

Study of dynamics of phytoplankton and photosynthetic parameters using opportunity ships in the western English Channel

International audienc

¹³C incorporation (P^Chl in mmolC mg Chl <i>a</i> h⁻¹) plotted against the electron transport rate (ETR^Chl in mmol electrons mg Chl <i>a</i> h⁻¹).

<p>(A) <i>Pseudo-nitzschia pungens</i>, (B) <i>Asterionellopsis glacialis</i>, (C) <i>Heterocapsa sp</i> and (D) <i>Karenia mikimotoï</i>. The red line represents the linear regression performed on all data, the black line the linear regression performed on control treatment data (solid circles), the dotted line the linear regression performed on N-lim treatment data (empty circles), the dashed line the linear regression performed on P-lim treatment data (dark triangles pointing down) and the dashed-dotted line the linear regression performed on Si-lim treatment data (white triangles pointing up). Logarithmic regressions performed for <i>Asterionellopsis glacilais</i> on N and P-lim treatments are represented by the blue dotted and dashed lines.</p

Dynamics of phytoplankton diversity structure and primary productivity in the English Channel

The dynamics of the phytoplankton assemblage, the physical, chemical and biological parameters, and primary productivity and production were monitored in the central English Channel along a transect between Ouistreham and Portsmouth from January to December 2010. The spatial patterns of the phytoplankton assemblage were controlled by the hydrological characteristics of the water masses, and the annual structure of the phytoplankton assemblage was characteristic of the central English Channel and was controlled by seasonality. The spring bloom was dominated by a single species, Chaetoceros socialis, and associated with low microphytoplankton evenness and Shannon-Wiener indices, whereas the evenness index was high from late spring to winter and associated with the proliferation of pico- and nanophytoplankton cells. We identified 2 species responsible for harmful algal blooms, Phaeocystis globosa, which dominated the community in the northern part of the Seine Bay in May, and Lepidodinium chlorophorum, which dominated the community near the French coast in September. We examined the relationship between microphytoplankton diversity and maximum primary production and productivity. We found a negative parabolic relationship between the diversity indices (evenness and Shannon-Wiener) and maximum primary production, and a positive parabolic relationship between the number of taxa (richness) and maximum primary production. However, we found no relationship between maximum productivity and the evenness or richness indices. High levels of productivity were measured during the increasing abundance of pico and nanophytoplankton cells, highlighting the importance of taking the dominant functional group into account, rather than the degree of diversity, when explaining the level of productivity

Nutrient concentrations and nutrient ratios in each treatment.

<p>Nutrient concentrations are in µmol L⁻¹.</p

Mean of biological and photosynthetic parameters for each species and treatments.

<p>Mean ± standard deviation (a≠b≠c, P<0.001) for <i>Pseudo-nitzschia pungens</i>, <i>Asterionellopsis glacialis</i>, <i>Heterocapsa sp</i> and <i>Karenia mikimotoï</i> under the control, N-lim, P-lim and Si-lim treatments of (A) the chlorophyll <i>a</i> concentration in µg Chl <i>a</i> L⁻¹, (B) quantum efficiency of the PSII (F_v/F_m), (C) the chlorophyll-specific absorption cross section (a*) in m² mg Chl <i>a</i>⁻¹, (D) the carbon/Chl <i>a</i> ratio in µg C µg Chl <i>a</i>⁻¹, (E) the maximum electron transport rate (ETR^Car_max) in mmol electron mol C⁻¹ h⁻¹ and (F) the maximum carbon incorporation (P^Car_max) in mol C mol C⁻¹ h⁻¹.</p

Values of the slope (Φ_C.e) of the linear regressions performed between the carbon incorporation (P^Chl) and ETR^Chl.

<p>Values are in mol C mol electron⁻¹. Values with an asterisk (*) are significantly different from the control (P<0.05).</p

Effect of filtration rate on coal-sand dual-media filter performances for microalgae removal

International audienc

Spatiotemporal dynamics of physicochemical and photosynthetic parameters in the central English Channel

International audienc

Light:dark (12:12 h) quantification of carbohydrate fluxes in Crocosphaera watsonii

International audienc