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Onset of the spring bloom in the northwestern Mediterranean Sea: influence of environmental pulse events on the in situ hourly-scale dynamics of the phytoplankton community structure.

Thyssen M, Grégori GJ, Grisoni JM, Pedrotti ML, Mousseau L, Artigas LF, Marro S, Garcia N, Passafiume O, Denis MJ - Front Microbiol (2014)

Bottom Line: The third abundance pulse could be considered as the spring bloom commonly observed in the area.The high frequency data-set made it possible to study the phytoplankton cell cycle based on daily cycles of forward scatter and abundance.The combination of daily cell cycle, abundance trends and environmental pulses will open the way to the study of phytoplankton short-term reactivity to environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: CNRS/INSU, IRD, Mediterranean Institute of Oceanography, Aix Marseille Université Marseille, France.

ABSTRACT
Most of phytoplankton influence is barely understood at the sub meso scale and daily scale because of the lack of means to simultaneously assess phytoplankton functionality, dynamics and community structure. For a few years now, it has been possible to address this objective with an automated in situ high frequency sampling strategy. In order to study the influence of environmental short-term events (nutrients, wind speed, precipitation, solar radiation, temperature, and salinity) on the onset of the phytoplankton bloom in the oligotrophic Bay of Villefranche-sur-Mer (NW Mediterranean Sea), a fully remotely controlled automated flow cytometer (CytoSense) was deployed on a solar-powered platform (EOL buoy, CNRS-Mobilis). The CytoSense carried out single-cell analyses on particles (1-800 μm in width, up to several mm in length), recording optical pulse shapes when analyzing several cm(3). Samples were taken every 2 h in the surface waters during 2 months. Up to 6 phytoplankton clusters were resolved based on their optical properties (PicoFLO, Picoeukaryotes, Nanophytoplankton, Microphytoplankton, HighSWS, HighFLO). Three main abundance pulses involving the 6 phytoplankton groups monitored indicated that the spring bloom not only depends on light and water column stability, but also on short-term events such as wind events and precipitation followed by nutrient pulses. Wind and precipitation were also determinant in the collapse of the clusters' abundances. These events occurred within a couple of days, and phytoplankton abundance reacted within days. The third abundance pulse could be considered as the spring bloom commonly observed in the area. The high frequency data-set made it possible to study the phytoplankton cell cycle based on daily cycles of forward scatter and abundance. The combination of daily cell cycle, abundance trends and environmental pulses will open the way to the study of phytoplankton short-term reactivity to environmental conditions.

No MeSH data available.


Related in: MedlinePlus

Weekly surface water chlorophyll concentration (μg.dm−3) at Point B throughout the experiment.
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Figure 10: Weekly surface water chlorophyll concentration (μg.dm−3) at Point B throughout the experiment.

Mentions: The second pulse in phytoplankton abundance started in relation with the precipitation event of March 5 (Figures 2E, 5, 7, Table 1). This pulse also involved all the clusters resolved with the CytoSense, but the increase in picoeukaryotes abundance was much weaker than the previous one (picoeukaryotes abundance only increased 3-fold; Figures 5B, 7). The other clusters reached higher abundances compared with the first pulse, especially microphytoplankton cells, which reached their maximum abundance values (Figure 7). This pulse was not evidenced by the FACSCalibur data-set (Figure 6). A slight surge in NO−3 + NO−2, PO3−4 and Si(OH)4 concentrations was recorded on March 2 (Figures 2A–C). Clusters' abundance reacted within 3 days to this PO3−4 concentration rise (Figure 2B, Table 1). The precipitation event occurred later, suggesting that the second abundance pulse was driven by the nutrients (Table 1). This short abundance pulse was probably terminated by the wind event observed on March 9 (Figure 2D), which coincided with a NO−3 + NO−2 pulse (Figure 2A) and a temperature decrease (Figure 2G). Conversely, this wind event would have induced the third phytoplankton abundance pulse (after March 9), together with the elevation in surface water temperature (Figure 2G) and augmentation of solar radiance (Figure 2F). High correlations with a lag of 4.6–7.2 days were observed between NO−3 + NO2 and all phytoplankton clusters (Table 1). The lag recorded after the precipitation event was longer (i.e. 9.8–10.7 days), suggesting that this event (certainly in association with wind) was conducive to the NO−3 + NO2 concentration surge. This third pulse was the longest and the most intense we observed during the sampling period, and it could be related to the spring phytoplankton bloom usually observed in this area (Gomez and Gorsky, 2003; Vandromme et al., 2011). This bloom also corresponded to the maximum chlorophyll concentration recorded at Point B during the weekly SOMLIT survey (Figure 10). The last wind event observed, on March 19, blowing at a speed >6 m.s−1, could have triggered the sudden cell abundance collapse recorded in nearly all the phytoplankton clusters. This phenomenon was also observed with easterly wind events (Warembourg, 2005), although these were not particularly marked.


Onset of the spring bloom in the northwestern Mediterranean Sea: influence of environmental pulse events on the in situ hourly-scale dynamics of the phytoplankton community structure.

Thyssen M, Grégori GJ, Grisoni JM, Pedrotti ML, Mousseau L, Artigas LF, Marro S, Garcia N, Passafiume O, Denis MJ - Front Microbiol (2014)

Weekly surface water chlorophyll concentration (μg.dm−3) at Point B throughout the experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4129916&req=5

Figure 10: Weekly surface water chlorophyll concentration (μg.dm−3) at Point B throughout the experiment.
Mentions: The second pulse in phytoplankton abundance started in relation with the precipitation event of March 5 (Figures 2E, 5, 7, Table 1). This pulse also involved all the clusters resolved with the CytoSense, but the increase in picoeukaryotes abundance was much weaker than the previous one (picoeukaryotes abundance only increased 3-fold; Figures 5B, 7). The other clusters reached higher abundances compared with the first pulse, especially microphytoplankton cells, which reached their maximum abundance values (Figure 7). This pulse was not evidenced by the FACSCalibur data-set (Figure 6). A slight surge in NO−3 + NO−2, PO3−4 and Si(OH)4 concentrations was recorded on March 2 (Figures 2A–C). Clusters' abundance reacted within 3 days to this PO3−4 concentration rise (Figure 2B, Table 1). The precipitation event occurred later, suggesting that the second abundance pulse was driven by the nutrients (Table 1). This short abundance pulse was probably terminated by the wind event observed on March 9 (Figure 2D), which coincided with a NO−3 + NO−2 pulse (Figure 2A) and a temperature decrease (Figure 2G). Conversely, this wind event would have induced the third phytoplankton abundance pulse (after March 9), together with the elevation in surface water temperature (Figure 2G) and augmentation of solar radiance (Figure 2F). High correlations with a lag of 4.6–7.2 days were observed between NO−3 + NO2 and all phytoplankton clusters (Table 1). The lag recorded after the precipitation event was longer (i.e. 9.8–10.7 days), suggesting that this event (certainly in association with wind) was conducive to the NO−3 + NO2 concentration surge. This third pulse was the longest and the most intense we observed during the sampling period, and it could be related to the spring phytoplankton bloom usually observed in this area (Gomez and Gorsky, 2003; Vandromme et al., 2011). This bloom also corresponded to the maximum chlorophyll concentration recorded at Point B during the weekly SOMLIT survey (Figure 10). The last wind event observed, on March 19, blowing at a speed >6 m.s−1, could have triggered the sudden cell abundance collapse recorded in nearly all the phytoplankton clusters. This phenomenon was also observed with easterly wind events (Warembourg, 2005), although these were not particularly marked.

Bottom Line: The third abundance pulse could be considered as the spring bloom commonly observed in the area.The high frequency data-set made it possible to study the phytoplankton cell cycle based on daily cycles of forward scatter and abundance.The combination of daily cell cycle, abundance trends and environmental pulses will open the way to the study of phytoplankton short-term reactivity to environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: CNRS/INSU, IRD, Mediterranean Institute of Oceanography, Aix Marseille Université Marseille, France.

ABSTRACT
Most of phytoplankton influence is barely understood at the sub meso scale and daily scale because of the lack of means to simultaneously assess phytoplankton functionality, dynamics and community structure. For a few years now, it has been possible to address this objective with an automated in situ high frequency sampling strategy. In order to study the influence of environmental short-term events (nutrients, wind speed, precipitation, solar radiation, temperature, and salinity) on the onset of the phytoplankton bloom in the oligotrophic Bay of Villefranche-sur-Mer (NW Mediterranean Sea), a fully remotely controlled automated flow cytometer (CytoSense) was deployed on a solar-powered platform (EOL buoy, CNRS-Mobilis). The CytoSense carried out single-cell analyses on particles (1-800 μm in width, up to several mm in length), recording optical pulse shapes when analyzing several cm(3). Samples were taken every 2 h in the surface waters during 2 months. Up to 6 phytoplankton clusters were resolved based on their optical properties (PicoFLO, Picoeukaryotes, Nanophytoplankton, Microphytoplankton, HighSWS, HighFLO). Three main abundance pulses involving the 6 phytoplankton groups monitored indicated that the spring bloom not only depends on light and water column stability, but also on short-term events such as wind events and precipitation followed by nutrient pulses. Wind and precipitation were also determinant in the collapse of the clusters' abundances. These events occurred within a couple of days, and phytoplankton abundance reacted within days. The third abundance pulse could be considered as the spring bloom commonly observed in the area. The high frequency data-set made it possible to study the phytoplankton cell cycle based on daily cycles of forward scatter and abundance. The combination of daily cell cycle, abundance trends and environmental pulses will open the way to the study of phytoplankton short-term reactivity to environmental conditions.

No MeSH data available.


Related in: MedlinePlus