Instrumented elephant seals reveal the seasonality in chlorophyll and light‐mixing regime in the iron‐fertilized Southern Ocean

Blain, S.; Renaut, Sophie; Xing, Xiaogang; Claustre, Hervé; Guinet, Christophe

doi:10.1002/2013gl058065

Cited by 33 publications

(30 citation statements)

References 42 publications

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“…In these regimes, the b bp :Chl a ratio remains constant regardless of the light intensity in both the productive and surface layers suggesting that phytoplankton photoacclimation is likely not an important driver of the variability in the b bp ‐to‐Chl a relationship. We note, however, that in the SO other factors may come into play, such as the light‐mixing regime or iron limitation (e.g., Blain et al, ; Boyd, ). On the opposite, in the subtropical regime, Chl a and b bp are decoupled in the surface layer as well as in the DCM layer.…”

Section: Discussionmentioning

confidence: 86%

Assessing the Variability in the Relationship Between the Particulate Backscattering Coefficient and the Chlorophyll a Concentration From a Global Biogeochemical‐Argo Database

et al. 2018

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Characterizing phytoplankton distribution and dynamics in the world's open oceans requires in situ observations over a broad range of space and time scales. In addition to temperature/salinity measurements, Biogeochemical‐Argo (BGC‐Argo) profiling floats are capable of autonomously observing at high‐frequency bio‐optical properties such as the chlorophyll fluorescence, a proxy of the chlorophyll a concentration (Chla), the particulate backscattering coefficient (bbp), a proxy of the stock of particulate organic carbon, and the light available for photosynthesis. We analyzed an unprecedented BGC‐Argo database of more than 8,500 multivariable profiles collected in various oceanic conditions, from subpolar waters to subtropical gyres. Our objective is to refine previously established Chla versus bbp relationships and gain insights into the sources of vertical, seasonal, and regional variability in this relationship. Despite some regional, seasonal and vertical variations, a general covariation occurs at a global scale. We distinguish two main contrasted situations: (1) concomitant changes in Chla and bbp that correspond to actual variations in phytoplankton biomass, e.g., in subpolar regimes; (2) a decoupling between the two variables attributed to photoacclimation or changes in the relative abundance of nonalgal particles, e.g., in subtropical regimes. The variability in the bbp:Chla ratio in the surface layer appears to be essentially influenced by the type of particles and by photoacclimation processes. The large BGC‐Argo database helps identifying the spatial and temporal scales at which this ratio is predominantly driven by one or the other of these two factors.

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Section: Discussionmentioning

confidence: 86%

Assessing the Variability in the Relationship Between the Particulate Backscattering Coefficient and the Chlorophyll a Concentration From a Global Biogeochemical‐Argo Database

et al. 2018

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“…They have contributed significantly to our current understanding on the spatio-temporal dynamics of phytoplankton (Cullen 1982;Boss and Behrenfeld 2010). To date, they have been integrated to every oceanographic research platform such as CTD rosettes (Cullen 1982), flow-through systems (Platt 1972), moored buoys (Kinkade et al 1999;Pettigrew and Roesler 2005), Bio-Argo floats (Boss et al 2008;Mignot et al 2014;Xing et al 2014), gliders (Niewiadomska et al 2008;Sackmann et al 2008;Cetinić et al 2009), and even elephant seals (Blain et al 2013;Guinet et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Correction of profiles of in‐situ chlorophyll fluorometry for the contribution of fluorescence originating from non‐algal matter

Xing

Claustre

Boss

et al. 2016

Limnology & Ocean Methods

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In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll‐a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio‐Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal “deep sea red fluorescence” features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio‐Argo floats), we show that the fluorescence signal measured by a humic‐like DOM fluorometer is highly correlated to the “deep sea red fluorescence.” Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non‐algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so‐called “deep‐offset correction”), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio‐Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality‐control and correction of chlorophyll a fluorescence originating from Bio‐Argo network.

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“…The eastern part of the Kerguelen Plateau sustains one of the most important local foraging areas for land-based marine predators (birds, penguins, seals and elephant seals) and for whales (Hindell et al, 2011;Blain et al, 2013). Satellitebased chlorophyll images of this region highlight the intensive seasonal Kerguelen bloom and its south-east extension off the archipelago (Schlitzer, 2002;Thomalla et al, 2011;Blain et al, 2013;Trull et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Satellitebased chlorophyll images of this region highlight the intensive seasonal Kerguelen bloom and its south-east extension off the archipelago (Schlitzer, 2002;Thomalla et al, 2011;Blain et al, 2013;Trull et al, 2015). During the KEOPS1 survey (KErguelen Ocean and Plateau compared Study), the origin and fate of the elevated phytoplankton biomass over the Kerguelen Plateau were addressed (Blain et al, 2008), with a focus on the mechanisms supplying the surface waters with iron.…”

Section: Introductionmentioning

confidence: 99%

“…1). The PF flow on the shelf induces entrainment and mixing of Feenriched shelf waters from plateau sediments in the oceanic upper layer in the area east of Kerguelen, and is a driver of relatively high phytoplankton bloom concentrations, with a strong increase from October to December (Blain et al, 2007(Blain et al, , 2013, initially dominated by diatoms of high growth rates (Quéguiner, 2013) contrasting with the generally highnutrient low-chlorophyll (HNLC) surface oceanic waters of the Southern Ocean. This enhanced biological productivity in the eastern area fuels the trophic level of zooplankton and micronekton, which are potential prey of fish and squid forage required to meet the demand of top predators.…”

Section: Introductionmentioning

confidence: 99%

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Mesozooplankton structure and functioning during the onset of the Kerguelen phytoplankton bloom during the KEOPS2 survey

et al. 2015

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Abstract. This paper presents results on the spatial and temporal distribution patterns of mesozooplankton in the naturally fertilized region to the east of the Kerguelen Islands (Southern Ocean) visited at early bloom stage during the KEOPS2 survey (15 October to 20 November 2011). The aim of this study was to compare the zooplankton response in contrasted environments localized over the Kerguelen Plateau in waters of the east shelf and shelf edge and in productive oceanic deep waters characterized by conditions of complex circulation and rapidly changing phytoplankton biomass.The mesozooplankton community responded to the spring bloom earlier on the plateau than in the oceanic waters, where complex mesoscale circulation stimulated initial more or less ephemeral blooms before a broader bloom extension. Taxonomic compositions showed a high degree of similarity across the whole region, and the populations initially responded to spring bloom with a large production of larval forms increasing abundances, without biomass changes. Taxonomic composition and stable isotope ratios of sizefractionated zooplankton indicated the strong domination of herbivores, and the total zooplankton biomass values over the survey presented a significant correlation with the integrated chlorophyll concentrations in the mixed layer.The biomass stocks observed at the beginning of the KEOPS2 cruise were around 1.7 g C m −2 above the plateau and 1.2 g C m −2 in oceanic waters. Zooplankton biomass in oceanic waters remained on average below 2 g C m −2 over the study period, except for one station in the Polar Front zone (F-L), whereas zooplankton biomasses were around 4 g C m −2 on the plateau at the end of the survey. The most remarkable feature during the sampling period was the stronger increase in abundance in the oceanic waters (25 × 10 3 to 160 × 10 3 ind m −2 ) than on the plateau (25 × 10 3 to 90 × 10 3 ind m −2 ). The size structure and taxonomic distribution patterns revealed a cumulative contribution of various larval stages of dominant copepods and euphausiids particularly in the oceanic waters, with clearly identifiable stages of progress during a Lagrangian time series survey. The reproduction and early stage development of dominant species were sustained by mesoscale-related initial ephemeral blooms in oceanic waters, but growth was still food-limited and zooplankton biomass stagnated. In contrast, zooplankton abundance and biomass on the shelf were both in a growing phase, at slightly different rates, due to growth under sub-optimal conditions. Combined with our observations during the KEOPS1 survey (January-February 2005), the present results deliver a consistent understanding of patterns in mesozooplankton abundance and biomass from early spring to summer in the poorly documented oceanic region east of the Kerguelen Islands.

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Instrumented elephant seals reveal the seasonality in chlorophyll and light‐mixing regime in the iron‐fertilized Southern Ocean

Cited by 33 publications

References 42 publications

Assessing the Variability in the Relationship Between the Particulate Backscattering Coefficient and the Chlorophyll a Concentration From a Global Biogeochemical‐Argo Database

Assessing the Variability in the Relationship Between the Particulate Backscattering Coefficient and the Chlorophyll a Concentration From a Global Biogeochemical‐Argo Database

Correction of profiles of in‐situ chlorophyll fluorometry for the contribution of fluorescence originating from non‐algal matter

Mesozooplankton structure and functioning during the onset of the Kerguelen phytoplankton bloom during the KEOPS2 survey

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