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The Temporal Dynamics of Coastal Phytoplankton and Bacterioplankton in the Eastern Mediterranean Sea.

Raveh O, David N, Rilov G, Rahav E - PLoS ONE (2015)

Bottom Line: Based on size fractionating, picophytoplankton was abundant during the summer, whereas nano-microphytoplankton predominated during the winter and early spring, which were also evident in the size-fractionated primary production rates.Autotrophic abundance and production correlated negatively with temperature, but did not correlate with inorganic nutrients.These findings have important ecological implications for food web dynamics and for biological carbon sequestration in this understudied region.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Oceanography, Israel Oceanographic and Limnological Research, Haifa, Israel.

ABSTRACT
This study considers variability in phytoplankton and heterotrophic bacterial abundances and production rates, in one of the most oligotrophic marine regions in the world-the Levantine Basin. The temporal dynamics of these planktonic groups were studied in the coastal waters of the southeastern Mediterranean Sea approximately every two weeks for a total of two years. Heterotrophic bacteria were abundant mostly during late summer and midwinter, and were positively correlated with bacterial production and with N2 fixation. Based on size fractionating, picophytoplankton was abundant during the summer, whereas nano-microphytoplankton predominated during the winter and early spring, which were also evident in the size-fractionated primary production rates. Autotrophic abundance and production correlated negatively with temperature, but did not correlate with inorganic nutrients. Furthermore, a comparison of our results with results from the open Levantine Basin demonstrates that autotrophic and heterotrophic production, as well as N2 fixation rates, are considerably higher in the coastal habitat than in the open sea, while nutrient levels or cell abundance are not different. These findings have important ecological implications for food web dynamics and for biological carbon sequestration in this understudied region.

No MeSH data available.


Comparison between the open and coastal Levantine Basin (eastern Mediterranean Sea) water.Box-plot distribution of NO2+NO3 (A), PO4 (B), Si(OH)4 (C), bacterial production, BP (D), primary production, PP (E) and N2 fixation (F) in the open Levantine Basin (euphotic zone, bottom depth of stations >1000 m) and in the coastal site (this study). Data for the open sea were compiled from Yogev et al., [35]; Kress et al., [3, 36], Rahav et al., [37, 38, 39]; Bonnet et al., [40], Ibello et al., [41] and Rahav et al., unpublished.
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pone.0140690.g006: Comparison between the open and coastal Levantine Basin (eastern Mediterranean Sea) water.Box-plot distribution of NO2+NO3 (A), PO4 (B), Si(OH)4 (C), bacterial production, BP (D), primary production, PP (E) and N2 fixation (F) in the open Levantine Basin (euphotic zone, bottom depth of stations >1000 m) and in the coastal site (this study). Data for the open sea were compiled from Yogev et al., [35]; Kress et al., [3, 36], Rahav et al., [37, 38, 39]; Bonnet et al., [40], Ibello et al., [41] and Rahav et al., unpublished.

Mentions: In order to better understand the spatial dynamics of inorganic nutrients, production and N2 fixation rates in the Levantine Basin, we compared the data available from different studies conducted in the open (non-coastal) eastern Mediterranean Sea [3, 35, 36, 37, 38, 39, 40, 41] to the results obtained in this study (coastal). While inorganic nutrient concentrations were similar in both the coastal and the open water environments (P> 0.05, Fig 6A, 6B and 6C), autotrophic and heterotrophic bacterial production, as well as N2 fixation were significantly (P< 0.001) higher by threefold to sevenfold in the coastal waters (Fig 6D, 6E and 6F). Furthermore, heterotrophic bacteria were present in the same order of magnitude in the coastal water as they were in the open Levantine (average 3.9x 105 cells mL-1), yet their averaged production rates were ~fourfold higher in the coastal (0.66 μg C L-1 d-1) relative to the open sea (0.17 μg C L-1 d-1, Fig 7A, Table 3) [42– 53]. This means that the average bacterial cell-specific activity (i.e. the bacterial production per bacterial cell) was ~50 pg C cell-1 d-1 in the open sea, whereas it was approximately twofold, in the coastal study site (106 pg C cell-1 d-1). Finally, the relationship between bacterial and primary production was examined in both water types [42– 53]. This relationship is a proxy for the flux of phytoplankton-derived carbon that passes through the microbial heterotrophic food web. While primary and bacterial production exhibited positive linear correlation in the open water of the Mediterranean Sea (p< 0.001), no such coupling was found in the coastal water (p = 0.114, Table 3, Fig 7B).


The Temporal Dynamics of Coastal Phytoplankton and Bacterioplankton in the Eastern Mediterranean Sea.

Raveh O, David N, Rilov G, Rahav E - PLoS ONE (2015)

Comparison between the open and coastal Levantine Basin (eastern Mediterranean Sea) water.Box-plot distribution of NO2+NO3 (A), PO4 (B), Si(OH)4 (C), bacterial production, BP (D), primary production, PP (E) and N2 fixation (F) in the open Levantine Basin (euphotic zone, bottom depth of stations >1000 m) and in the coastal site (this study). Data for the open sea were compiled from Yogev et al., [35]; Kress et al., [3, 36], Rahav et al., [37, 38, 39]; Bonnet et al., [40], Ibello et al., [41] and Rahav et al., unpublished.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4608699&req=5

pone.0140690.g006: Comparison between the open and coastal Levantine Basin (eastern Mediterranean Sea) water.Box-plot distribution of NO2+NO3 (A), PO4 (B), Si(OH)4 (C), bacterial production, BP (D), primary production, PP (E) and N2 fixation (F) in the open Levantine Basin (euphotic zone, bottom depth of stations >1000 m) and in the coastal site (this study). Data for the open sea were compiled from Yogev et al., [35]; Kress et al., [3, 36], Rahav et al., [37, 38, 39]; Bonnet et al., [40], Ibello et al., [41] and Rahav et al., unpublished.
Mentions: In order to better understand the spatial dynamics of inorganic nutrients, production and N2 fixation rates in the Levantine Basin, we compared the data available from different studies conducted in the open (non-coastal) eastern Mediterranean Sea [3, 35, 36, 37, 38, 39, 40, 41] to the results obtained in this study (coastal). While inorganic nutrient concentrations were similar in both the coastal and the open water environments (P> 0.05, Fig 6A, 6B and 6C), autotrophic and heterotrophic bacterial production, as well as N2 fixation were significantly (P< 0.001) higher by threefold to sevenfold in the coastal waters (Fig 6D, 6E and 6F). Furthermore, heterotrophic bacteria were present in the same order of magnitude in the coastal water as they were in the open Levantine (average 3.9x 105 cells mL-1), yet their averaged production rates were ~fourfold higher in the coastal (0.66 μg C L-1 d-1) relative to the open sea (0.17 μg C L-1 d-1, Fig 7A, Table 3) [42– 53]. This means that the average bacterial cell-specific activity (i.e. the bacterial production per bacterial cell) was ~50 pg C cell-1 d-1 in the open sea, whereas it was approximately twofold, in the coastal study site (106 pg C cell-1 d-1). Finally, the relationship between bacterial and primary production was examined in both water types [42– 53]. This relationship is a proxy for the flux of phytoplankton-derived carbon that passes through the microbial heterotrophic food web. While primary and bacterial production exhibited positive linear correlation in the open water of the Mediterranean Sea (p< 0.001), no such coupling was found in the coastal water (p = 0.114, Table 3, Fig 7B).

Bottom Line: Based on size fractionating, picophytoplankton was abundant during the summer, whereas nano-microphytoplankton predominated during the winter and early spring, which were also evident in the size-fractionated primary production rates.Autotrophic abundance and production correlated negatively with temperature, but did not correlate with inorganic nutrients.These findings have important ecological implications for food web dynamics and for biological carbon sequestration in this understudied region.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Oceanography, Israel Oceanographic and Limnological Research, Haifa, Israel.

ABSTRACT
This study considers variability in phytoplankton and heterotrophic bacterial abundances and production rates, in one of the most oligotrophic marine regions in the world-the Levantine Basin. The temporal dynamics of these planktonic groups were studied in the coastal waters of the southeastern Mediterranean Sea approximately every two weeks for a total of two years. Heterotrophic bacteria were abundant mostly during late summer and midwinter, and were positively correlated with bacterial production and with N2 fixation. Based on size fractionating, picophytoplankton was abundant during the summer, whereas nano-microphytoplankton predominated during the winter and early spring, which were also evident in the size-fractionated primary production rates. Autotrophic abundance and production correlated negatively with temperature, but did not correlate with inorganic nutrients. Furthermore, a comparison of our results with results from the open Levantine Basin demonstrates that autotrophic and heterotrophic production, as well as N2 fixation rates, are considerably higher in the coastal habitat than in the open sea, while nutrient levels or cell abundance are not different. These findings have important ecological implications for food web dynamics and for biological carbon sequestration in this understudied region.

No MeSH data available.