Annual and interannual variability in phytoplankton at a permanent station off Kerguelen Islands, Southern Ocean

Kopczyńska, Elżbieta E.; Fiala, Michel; Jeandel, Catherine

doi:10.1007/s003000050312

Cited by 47 publications

(28 citation statements)

References 27 publications

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“…Even if there are no available data to confirm it, a limitation by iron seems almost likely given the tenuity of the surface mixed layer (from 20 to 35 m), the high abundance of macronutrients and the low grazing pressure . At station R2 and TNS-1, the picophytoplankton contribution to chlorophyll biomass was higher (up to 20 %) than in the rest of the study area but relatively low by comparison to previous studies in HNLC waters (Kopczyńska et al, 1998;Gall et al, 2001). Similar results were reported for the HNLC station of the first cruise KEOPS1 (Uitz et al, 2009).…”

Section: Impact Of Natural Iron Enrichment On Chlorophyll a And Phytosupporting

confidence: 77%

Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean

et al. 2014

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Abstract. The particulate matter distribution and phytoplankton community structure of the iron-fertilized Kerguelen region were investigated in early austral spring (October-November 2011) during the KEOPS2 cruise. The iron-fertilized region was characterized by a complex mesoscale circulation resulting in a patchy distribution of particulate matter. Integrated concentrations over 200 m ranged from 72.2 to 317.7 mg m −2 for chlorophyll a 314 to 744 mmol m −2 for biogenic silica (BSi), 1106 to 2268 mmol m −2 for particulate organic carbon, 215 to 436 mmol m −2 for particulate organic nitrogen, and 29.3 to 39.0 mmol m −2 for particulate organic phosphorus. Three distinct high biomass areas were identified: the coastal waters of Kerguelen Islands, the easternmost part of the study area in the polar front zone, and the southeastern Kerguelen Plateau. As expected from previous artificial and natural iron-fertilization experiments, the iron-fertilized areas were characterized by the development of large diatoms revealed by BSi size-fractionation and high performance liquid chromatography (HPLC) pigment signatures, whereas the ironlimited reference area was associated with a low biomass dominated by a mixed (nanoflagellates and diatoms) phytoplankton assemblage. A major difference from most previous artificial iron fertilization studies was the observation of much higher Si : C, Si : N, and Si : P ratios (0.31 ± 0.16, 1.6 ± 0.7 and 20.5 ± 7.9, respectively) in the iron-fertilized areas compared to the iron-limited reference station (0.13, 1.1, and 5.8, respectively). A second difference is the patchy response of the elemental composition of phytoplankton communities to large scale natural iron fertilization. Comparison to the previous KEOPS1 cruise also allowed to address the seasonal dynamics of phytoplankton bloom over the southeastern plateau. From particulate organic carbon (POC), particulate organic nitrogen (PON), and BSi evolutions, we showed that the elemental composition of the particulate matter also varies at the seasonal scale. This temporal evolution followed changes of the phytoplankton community structure as well as major changes in the nutrient stocks progressively leading to silicic acid exhaustion at the end of the productive season.Our observations suggest that the specific response of phytoplankton communities under natural iron fertilization is much more diverse than what has been regularly observed in artificial iron fertilization experiments and that the elemental composition of the bulk particulate matter reflects phytoplankton taxonomic structure rather than being a direct consequence of iron availability.

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Section: Impact Of Natural Iron Enrichment On Chlorophyll a And Phytosupporting

confidence: 77%

Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean

et al. 2014

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“…In the South Pacific Ocean, the model produces large interannual variability of ±0.15 mg m −3 but SeaWiFS chl a cannot be used because of the high Southern latitude and low solar angle (Figure 4e). In the south Indian Ocean, a clear reduction in chl a of over 0.10 mg m −3 was observed during 1999, with an increase of 0.15 mg m −3 starting in the end of 1999 (Figure 4f) [ Kopczynska et al , 1998]. This variability corresponds to the passage of the warm phase of an ACW observed and reproduced by the model.…”

Section: Model Results and Evaluationmentioning

confidence: 90%

Propagation of climatic events on ocean stratification, marine biology, and CO₂: Case studies over the 1979–1999 period

et al. 2003

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[1] We investigate the propagation of climatic events on ocean stratification, marine biology, and CO 2 using a large-scale ocean general circulation model coupled to a simple biogeochemical model of plankton dynamics and the carbon cycle. The model was forced with satellite and reanalysis fields during 1979-1999. We focus on three climatic events: (1) the North Atlantic Oscillation, (2) El Niño events, and (3) the Antarctic Circumpolar Wave. Such climatic events caused variability in ocean stratification, approximated by the mixing depth (MD), from ±20 m in the subtropics to ±100 s of meters at high latitudes. In the subtropics, deepening of the MD resupplied nutrient-impoverished surface waters and increased marine biomass by 20-100%. In contrast, at high latitudes, shoaling of the MD lengthened the growing season (i.e., the length of time that light is available for plankton growth) and increased marine biomass by 10-20%. Variability in marine biology reached global peak-to-peak values of ±0.01 mg m À3 for surface chl a, ±3.4 Pg C yr À1 for primary production, and ±0.3 Pg C yr À1 for export production and its contribution to CO 2 fluxes. Our model results suggest that changes in ocean stratification driven by short-term climatic events could be used to understand and quantify the feedbacks from marine biology to CO 2 and climate.

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“…By contrast, the highest d ML values (200 ‐ 500 µm) were observed in summer during high POC, microplankton‐dominated phytoplankton blooms. These blooms are generally composed of a mixture of chain forming (chain length >100 µm) small diatoms ( Pseudo‐Nitzschia , Chaetoceros Hyalochaete, Odontella ), large diatoms such as Corethron pennatum (200 µm), Proboscia and Rhizosolenia (200–500 µm), large dinoflagellates ( Protoperidinium , Gyrodinium ∼100 µm) and even the giant diatom Thalassiothrix (>1,000 µm length) (Armand et al, ; Kopczyńska et al, ; Lasbleiz et al, ; Rembauville et al, ). Interestingly, the late summer nanoplankton‐dominated bloom North of Crozet was not associated with any increase in d ML that remained <50 µm (float 036b, January–March 2016, Figure b).…”

Section: Resultsmentioning

confidence: 99%

Plankton Assemblage Estimated with BGC‐Argo Floats in the Southern Ocean: Implications for Seasonal Successions and Particle Export

et al. 2017

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The Southern Ocean (SO) hosts plankton communities that impact the biogeochemical cycles of the global ocean. However, weather conditions in the SO restrict mainly in situ observations of plankton communities to spring and summer, preventing the description of biological successions at an annual scale. Here, we use shipboard observations collected in the Indian sector of the SO to develop a multivariate relationship between physical and bio‐optical data, and, the composition and carbon content of the plankton community. Then we apply this multivariate relationship to five biogeochemical Argo (BGC‐Argo) floats deployed within the same bio‐geographical zone as the ship‐board observations to describe spatial and seasonal changes in plankton assemblage. The floats reveal a high contribution of bacteria below the mixed layer, an overall low abundance of picoplankton and a seasonal succession from nano‐ to microplankton during the spring bloom. Both naturally iron‐fertilized waters downstream of the Crozet and Kerguelen Plateaus show elevated phytoplankton biomass in spring and summer but they differ by a nano‐ or microplankton dominance at Crozet and Kerguelen, respectively. The estimated plankton group successions appear consistent with independent estimations of particle diameter based on the optical signals. Furthermore, the comparison of the plankton community composition in the surface layer with the presence of large mesopelagic particles diagnosed by spikes of optical signals provides insight into the nature and temporal changes of ecological vectors that drive particle export. This study emphasizes the power of BGC‐Argo floats for investigating important biogeochemical processes at high temporal and spatial resolution.

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Annual and interannual variability in phytoplankton at a permanent station off Kerguelen Islands, Southern Ocean

Cited by 47 publications

References 27 publications

Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean

Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean

Propagation of climatic events on ocean stratification, marine biology, and CO₂: Case studies over the 1979–1999 period

Plankton Assemblage Estimated with BGC‐Argo Floats in the Southern Ocean: Implications for Seasonal Successions and Particle Export

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Annual and interannual variability in phytoplankton at a permanent station off Kerguelen Islands, Southern Ocean

Cited by 47 publications

References 27 publications

Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean

Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean

Propagation of climatic events on ocean stratification, marine biology, and CO2: Case studies over the 1979–1999 period

Plankton Assemblage Estimated with BGC‐Argo Floats in the Southern Ocean: Implications for Seasonal Successions and Particle Export

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Propagation of climatic events on ocean stratification, marine biology, and CO₂: Case studies over the 1979–1999 period