scholarly journals Diel variability of heterotrophic bacterial production and UV doses in the South East Pacific

2008 ◽  
Vol 5 (1) ◽  
pp. 435-462 ◽  
Author(s):  
F. Van Wambeke ◽  
M. Tedetti ◽  
S. Duhamel ◽  
R. Sempéré
Keyword(s):  
Bacterial Production ◽  
Ultraviolet B ◽  
Optical Measurements ◽  
The South ◽  
Solar Ultraviolet Radiation ◽  
Dna Damages ◽  
East Pacific ◽  
Pyrimidine Dimers ◽  
Diel Variability ◽  
South Pacific Gyre

Abstract. Diel variability of heterotrophic bacterial production (BP) was investigated in the South East Pacific from October to December 2004 during the BIOSOPE cruise. Three sites differing by their trophic status were studied: Marquesas Islands (MAR; 08° S, 141° W), the centre of the South Pacific Gyre (SPG) (GYR; 26° S, 114° W) and the eastern part of the SPG (EGY; 32° S, 91° W). At the three sites, diel variability of BP ranged from 17 to 40% and from 13 to 22% for volumetric surface (5 m) and integrated (to Ze and Zm) data, respectively. The main feature we observed was at 5 m, an abrupt increase (×2 to ×4) in leucine activity during the afternoon-sunset period (12:00–18:00 at the site MAR and 15:00–21:00 at the site GYR) and lowest activities recorded between 10:00 and 14:00. To assess the potential influence of solar ultraviolet radiation (UVR: 280–400 nm) on this BP diel variability, we determined, from in situ optical measurements, the mean tri-hourly ultraviolet B (UVB, 305 nm) and ultraviolet A (UVA, 380 nm) doses (irradiances integrated over time) within the mixed layer (Hm(UVB) and Hm(UVA), respectively). The wavelengths 305 nm and 380 nm were used as biologically effective wavelengths for the induction of DNA damages (cyclobutane pyrimidine dimers: CPDs) and photoenzymatic repairs (PERs), respectively. In the SPG, daily Hm(UVB) and Hm(UVA) were 0.6 and 14 kJ m−2 nm−1, respectively. The latter were probably the highest daily doses ever measured in the marine environment. The Hm(UVB)/Hm(UVA) ratio (Q) increased by 58, 117 and 46% from 06:00–09:00 to 12:00–15:00, and decreased by 36, 26 and 16% from 12:00–15:00 to 15:00–18:00 at the sites MAR, GYR and EGY, respectively. The relationship between Q and BP suggested a significant influence of UVR on the diel variability of BP (BP decreased when Q increased) at the site GYR from the surface waters to Zm, likely in relation with its hyper-oligotrophic status. Therefore, possible alternance of CPD and PER periods attributed to Q ratio, as well as a strong lags between process of autotrophic production with their associated dissolved organic carbon (DOC) release and heterotrophic utilization of organic matter could explain such diel variations.

scholarly journals Heterotrophic bacterial production in the South East Pacific: longitudinal trends and coupling with primary production

2007 ◽  
Vol 4 (4) ◽  
pp. 2761-2791 ◽  
Author(s):  
F. Van Wambeke ◽  
I. Obernosterer ◽  
T. Moutin ◽  
S. Duhamel ◽  
O. Ulloa ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Primary Production ◽  
Bacterial Production ◽  
South Pacific ◽  
Leucine Incorporation ◽  
The South ◽  
Phytoplankton Primary Production ◽  
East Pacific ◽  
Wide Range ◽  
South Pacific Gyre

Abstract. Spatial variations of heterotrophic bacterial production and phytoplankton primary production were investigated across South East Pacific Ocean (–141° W, –8° S to –72° W, –35° S) in November–December 2004. Bacterial production (³H leucine incorporation) integrated over the euphotic zone encompassed a wide range of values, from 43 mg C m−2 d−1 in the hyper-oligotrophic South Pacific Gyre to 392 mg C m−2 d−1 in the upwelling off Chile. Within the gyre (120° W, 22° S) records of low phytoplankton biomass (7 mg TChla m−2) were obtained and in situ 14C based particulate primary production rates were as low as 153 mg C m−2 d−1, thus equal to the value considered as a limit for primary production under strong oligotrophic conditions. In the South Pacific gyre average rates of ³H leucine incorporation rates, and leucine incorporation rates per cell (5–21 pmol L−1 h−1 and 15–56×10−21 mol cell−1 h−1, respectively), were in the same range as those reported for other oligotrophic sub tropical and temperate waters. Rates of dark community respiration, determined at selected stations across the transect varied in a narrow range (42–97 mmol O2 m−2 d−1), except for one station in the upwelling off Chile (245 mmol O2 m−2 d−1). Bacterial growth efficiencies varied between 5 and 38% and bacterial carbon demand largely exceeded 14C particulate primary production across the South Pacific Ocean. Net community production also revealed negative values in the South Pacific Gyre (–13±20 to –37±40 mmol O2 m−2 d−1). Such imbalances being impossible in this area far from any external input, we discuss the techniques involved for determining the coupling between primary production and bacterial heterotrophic production.

scholarly journals Calcite production by Coccolithophores in the South East Pacific Ocean: from desert to jungle

2007 ◽  
Vol 4 (5) ◽  
pp. 3267-3299 ◽  
Author(s):  
L. Beaufort ◽  
M. Couapel ◽  
N. Buchet ◽  
H. Claustre
Keyword(s):  
Size Range ◽  
Digital Camera ◽  
Euphotic Zone ◽  
The South ◽  
Carbonate Ions ◽  
East Pacific ◽  
Standing Stocks ◽  
South Pacific Gyre ◽  
East Pacific Ocean ◽  
First Time

Abstract. BIOSOPE cruise achieved an oceanographic transect from the Marquise Islands to the Peru-Chili upwelling (PCU) via the centre of the South Pacific Gyre (SPG). Water samples from 6 depths in the euphotic zone were collected at 20 stations. The concentrations of suspended calcite particles, coccolithophores cells and detached coccoliths were estimated together with size and weight using an automatic polarizing microscope, a digital camera, and a collection of softwares performing morphometry and pattern recognition. Some of these softwares are new and described here for the first time. The coccolithophores standing stocks are usually low and reach maxima west of the PCU. The coccoliths of Emiliania huxleyi, Gephyrocapsa spp. and Crenalithus spp. (Order Isochrysidales) represent 50% of all the suspended calcite particles detected in the size range 0.1–46 μm (21% of PIC in term of the calcite weight). The latter species are found to grow preferentially in the Chlorophyll maximum zone. In the SPG their maximum concentrations was found to occur between 150 and 200 m, which is very deep for these taxa. The weight and size of coccoliths and coccospheres are correlated. Large and heavy coccoliths and coccospheres are found in the regions with relative higher fertility in the Marquises Island and in the PCU. Small and light coccoliths and coccospheres are found west of the PCU. This distribution may correspond to that of the concentration of calcium and carbonate ions.

scholarly journals Introduction to the special section Bio-optical and biogeochemical conditions in the South East Pacific in late 2004: the BIOSOPE program

2008 ◽  
Vol 5 (1) ◽  
pp. 605-640 ◽  
Author(s):  
H. Claustre ◽  
A. Sciandra ◽  
D. Vaulot
Keyword(s):  
Optical Properties ◽  
Special Section ◽  
Austral Summer ◽  
South Pacific ◽  
Special Issue ◽  
The South ◽  
North West ◽  
East Pacific ◽  
High Nutrient ◽  
South Pacific Gyre

Abstract. The objectives of the BIOSOPE (BIogeochemistry and Optics SOuth Pacific Experiment) project was to study, during the austral summer, the biological, biogeochemical and bio-optical properties of different trophic regimes in the South East Pacific: the eutrophic zone associated with the upwelling regime of the Chilean coast, he mesotrophic area associated with the plume of the Marquises Islands in the HNLC (High Nutrient Low Chlorophyll) waters of this subequatorial area, and the extremely oligotrophic area associated with the central part of the South Pacific Gyre (SPG). At the end of 2004, a 55-day international cruise with 32 scientists on board took place between Tahiti and Chile, crossing the SPG along a North-West South-East transect. This paper describes in detail the objective of the BIOSOPE project, the implementation plan of the cruise, the main hydrological entities encountered along the ~8000 km South East pacific transect and ends with a general overview of the papers published in this Biogeosciences special issue.

scholarly journals Heterotrophic bacterial production in the eastern South Pacific: longitudinal trends and coupling with primary production

2008 ◽  
Vol 5 (1) ◽  
pp. 157-169 ◽  
Author(s):  
F. Van Wambeke ◽  
I. Obernosterer ◽  
T. Moutin ◽  
S. Duhamel ◽  
O. Ulloa ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Primary Production ◽  
Bacterial Production ◽  
South Pacific ◽  
Leucine Incorporation ◽  
The South ◽  
Phytoplankton Primary Production ◽  
South Pacific Ocean ◽  
Wide Range ◽  
South Pacific Gyre

Abstract. Spatial variation of heterotrophic bacterial production and phytoplankton primary production were investigated across the eastern South Pacific Ocean (−141° W, −8° S to −72° W, −35° S) in November–December 2004. Bacterial production (3H leucine incorporation) integrated over the euphotic zone encompassed a wide range of values, from 43 mg C m−2 d−1 in the hyper-oligotrophic South Pacific Gyre to 392 mg C m−2 d−1 in the upwelling off Chile. In the gyre (120° W, 22° S) records of low phytoplankton biomass (7 mg Total Chla m−2) were obtained and fluxes of in situ 14C-based particulate primary production were as low as 153 mg C m−2 d−1, thus equal to the value considered as a limit for primary production under strong oligotrophic conditions. Average rates of 3H leucine incorporation rates, and leucine incorporation rates per cell (5–21 pmol l−1 h−1 and 15–56×10−21 mol cell−1 h−1, respectively) determined in the South Pacific gyre, were in the same range as those reported for other oligotrophic subtropical and temperate waters. Fluxes of dark community respiration, determined at selected stations across the transect varied in a narrow range (42–97 mmol O2 m−2 d−1), except for one station in the upwelling off Chile (245 mmol O2 m−2 d−1). Bacterial growth efficiencies varied between 5 and 38%. Bacterial carbon demand largely exceeded 14C particulate primary production across the South Pacific Ocean, but was lower or equal to gross community production.

scholarly journals Introduction to the special section bio-optical and biogeochemical conditions in the South East Pacific in late 2004: the BIOSOPE program

2008 ◽  
Vol 5 (3) ◽  
pp. 679-691 ◽  
Author(s):  
H. Claustre ◽  
A. Sciandra ◽  
D. Vaulot
Keyword(s):  
Optical Properties ◽  
Special Section ◽  
Austral Summer ◽  
South Pacific ◽  
Special Issue ◽  
The South ◽  
North West ◽  
East Pacific ◽  
High Nutrient ◽  
South Pacific Gyre

Abstract. The objectives of the BIOSOPE (BIogeochemistry and Optics SOuth Pacific Experiment) project was to study, during the austral summer, the biological, biogeochemical and bio-optical properties of different trophic regimes in the South East Pacific: the eutrophic zone associated with the upwelling regime off the Chilean coast, the mesotrophic area associated with the plume of the Marquises Islands in the HNLC (High Nutrient Low Chlorophyll) waters of this subequatorial area, and the extremely oligotrophic area associated with the central part of the South Pacific Gyre (SPG). At the end of 2004, a 55-day international cruise with 32 scientists on board took place between Tahiti and Chile, crossing the SPG along a North-West South-East transect. This paper describes in detail the objectives of the BIOSOPE project, the implementation plan of the cruise, the main hydrological entities encountered along the ~8000 km South East Pacific transect, and ends with a general overview of the 32 other papers published in this special issue.

scholarly journals Calcite production by coccolithophores in the south east Pacific Ocean

2008 ◽  
Vol 5 (4) ◽  
pp. 1101-1117 ◽  
Author(s):  
L. Beaufort ◽  
M. Couapel ◽  
N. Buchet ◽  
H. Claustre ◽  
C. Goyet
Keyword(s):  
Size Range ◽  
Digital Camera ◽  
Euphotic Zone ◽  
High Fertility ◽  
The South ◽  
East Pacific ◽  
Maximum Cell ◽  
South Pacific Gyre ◽  
East Pacific Ocean ◽  
First Time

Abstract. BIOSOPE cruise covered an oceanographic transect through the centre of the South Pacific Gyre (SPG) from the Marquesas archipelago to the Peru-Chile upwelling (PCU). Water samples from 6 depths in the euphotic zone were collected at 20 stations. The concentrations of suspended calcite particles, coccolithophores cells and detached coccoliths were estimated together with size and weight using an automatic polarizing microscope, a digital camera, and a collection of softwares performing morphometry and pattern recognition. Some of these softwares are new and described here for the first time. The coccolithophores standing stocks were usually low and reached maxima west of the PCU. The coccoliths of Emiliania huxleyi, Gephyrocapsa spp. and Crenalithus spp. (Order Isochrysidales) represented more than 30% of all the suspended calcite particles detected in the size range 0.1–46 μm (22% of PIC in term of calcite weight). These species grew preferentially in the Chlorophyll maximum zone. In the SPG their maximum cell concentrations were recorded between depth of 150 and 200 m, which is unusually deep for these taxa. The weight of coccoliths and coccospheres were correlated to their size. Large and heavy coccoliths and coccospheres were found in regions with relatively high fertility in the Marquises Island and in the PCU. Small and light coccoliths and coccospheres were found west of the PCU. This distribution is strongly related to ocean chemistry in particular to alkalinity and to carbonate ions concentration. The biotic (coccolithophores production) influence on calcification is mainly driven at the local scale (depth) whereas the abiotic (carbonate chemistry) plays its most important role at the regional (horizontal) level. Here 94% of the variability of coccolith and coccosphere weight can be explained by a change in 7 environmental variables.

scholarly journals Effect of solar ultraviolet radiation (280–400 nm) on the eggs and larvae of Atlantic cod (Gadus morhua)

1999 ◽  
Vol 56 (6) ◽  
pp. 1058-1067 ◽  
Author(s):  
France Béland ◽  
Howard I Browman ◽  
Carolina Alonso Rodriguez ◽  
Jean-François St-Pierre
Keyword(s):  
Water Column ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Outdoor Exposure ◽  
Ultraviolet B ◽  
Solar Ultraviolet Radiation ◽  
Mortality Effect ◽  
Eggs And Larvae ◽  
Very High ◽  
Solar Ultraviolet

In the Gulf of St. Lawrence, Canada, solar ultraviolet B radiation (UV-B, 280-320 nm) penetrates a significant percentage of the summer mixed-layer water column: organisms residing in this layer, such as the eggs of Atlantic cod (Gadus morhua), are exposed to UV-B. In outdoor exposure experiments, Atlantic cod eggs were incubated in the presence versus the absence of UV-B and (or) UV-A (320-400 nm). We tested two hypotheses: H1, UV-B induces mortality in Atlantic cod eggs, and H2, UV-A either exacerbates or mitigates any such UV-B-induced mortality. Hypothesis H1 was supported: there was a significant mortality effect on Atlantic cod eggs exposed to UV-B at the surface and at a depth of 50 cm. Hypothesis H2 was not supported: there was no effect of UV-A. These experiments indicate that Atlantic cod eggs present in the first metre of the water column (likely only a small percentage of the total egg population) are susceptible to UV-B. However, UV-B must be viewed as only one among many environmental factors that produce the very high levels of mortality typically observed in the planktonic early life stages of marine fishes.

Photoinhibition of natural phytoplankton assemblages in Lake Erie exposed to solar ultraviolet radiation

2000 ◽  
Vol 57 (2) ◽  
pp. 371-379 ◽  
Author(s):  
Christopher A Marwood ◽  
Ralph EH Smith ◽  
John A Furgal ◽  
Murray N Charlton ◽  
Keith R Solomon ◽  
...  
Keyword(s):  
Lake Erie ◽  
Pulse Amplitude ◽  
Ultraviolet B ◽  
Surface Radiation ◽  
Low Light ◽  
Solar Ultraviolet Radiation ◽  
Phytoplankton Assemblages ◽  
Photosystem Ii Efficiency ◽  
Kinetics Of ◽  
Modulated Chlorophyll Fluorescence

Photoinhibition was examined in natural assemblages of phytoplankton from Lake Erie exposed to ambient solar radiation. The impacts on photosynthesis of photosynthetically active radiation (400-700 nm) (PAR), ultraviolet-A radiation (320-400 nm) (UVA), and ultraviolet-B radiation (295-320 nm) (UVB) were assessed at three sites on the lake using pulse amplitude modulated chlorophyll fluorescence. Short exposures (<= 30 min) to sunlight containing UVB (1.8-4.4 mmol·m-2) resulted in the rapid loss of up to 60% of photosystem II efficiency (in the dark-adapted state) (Fv/Fm) and quantum yield (in the light-adapted state) (ΔF/F'm). Exposure to UVA (46-105 mmol·m-2) generally diminished Fv/Fm and, to a lesser extent, ΔF/F'm. Short exposures to PAR (733-1588 mmol·m-2) had no significant effects on electron transport. Recovery from UVA- or UVB-induced photoinhibition was complete for Fv/Fm and 90% complete for ΔF/F'm after 2 h in low light. The results indicate that exposures of phytoplankton to surface radiation need only be short in duration to cause substantial UV inhibition of photosynthesis. However, depending on the kinetics of mixing of the water column, recovery of photosynthesis is possible if there is sufficient time for repair of UV damage. Future elevated levels of solar UVB due to ozone depletion could significantly inhibit primary production in mesotrophic lakes such as Lake Erie.

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