Photosynthetic picoeukaryote community structure in the South East Pacific Ocean encompassing the most oligotrophic waters on Earth

In the present study we investigated spawning of the butterfly kingfish (Gasterochisma melampus), a Scombridae species distributed in circumpolar temperate waters of the Southern Hemisphere in the Atlantic, Indian and Pacific oceans. Using data from 25564 individuals collected by longline operations from 1987 to 1996, analysis of the gonadosomatic index, maturity based on oocyte size and the presence of hydrated eggs revealed that the spawning area was between longitude 85 and 130°W and latitude 28 and 41°S in the south-east Pacific Ocean, and that the spawning season was from mid-April to mid-July. Length–frequency data suggested that larger fish arrived and spawned earlier, whereas smaller fish did so later. The species has distinctive reproductive characteristics compared with other Scombridae: it produces large hydrated eggs 1.6mm in diameter, sea surface temperatures in the spawning area were as low as 14–18°C and more than 80% of fish were female. The south-east Pacific Ocean may be the only (and is at least the major) spawning area of the species. Butterfly kingfish is a single stock that migrates to the Atlantic, Indian and Pacific oceans to feed and returns to the south-east Pacific Ocean to spawn.

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Distribution of micro-organisms along a transect in the South-East Pacific Ocean (BIOSOPE cruise) from epifluorescence microscopy

Biogeosciences Discussions ◽

10.5194/bgd-4-2667-2007 ◽

2007 ◽

Vol 4 (4) ◽

pp. 2667-2697 ◽

Cited By ~ 8

Author(s):

S. Masquelier ◽

D. Vaulot

Keyword(s):

Pacific Ocean ◽

Epifluorescence Microscopy ◽

The South ◽

Dapi Staining ◽

Marquesas Islands ◽

East Pacific ◽

High Nutrient ◽

Ocean Gyre ◽

Micro Organisms ◽

East Pacific Ocean

Abstract. The distribution of selected groups of micro-organisms was analyzed along a South-East Pacific Ocean transect sampled during the BIOSOPE cruise in 2004. The transect could be divided into four regions of contrasted trophic status: a high Nutrient Low Chlorophyll (HNLC) region (mesotrophic) near the equator, the South-East Pacific Ocean gyre (hyper-oligotrophic), the transition region between the gyre and the coast of South America (moderately oligotrophic), and the Chile upwelling (eutrophic). The abundance of phycoerythrin containing picocyanobacteria, autotrophic and heterotrophic eukaryotes in different size ranges, dinoflagellates, and ciliates was determined by epifluorescence microscopy after DAPI staining. All populations reached a maximum in the Chile upwelling and a minimum near the centre of the gyre. Picocyanobacteria reached a maximum abundance of 70×10³ cell mL−1. In the HNLC zone, up to 50% of picocyanobacteria formed colonies. Autotrophic eukaryote and dinoflagellate abundance reached 24.5×10³ and 200 cell mL−1, respectively. We observed a shift in the size distribution of autotrophic eukaryotes from 2–5 μm in eutrophic and mesotrophic regions to less than 2 μm in the central region. The contribution of autotrophic eukaryotes to total eukaryotes was the lowest in the central gyre. Maximum concentration of ciliates (18 cell ml−1) also occurred in the Chile upwelling, but, in contrast to the other groups, their abundance was very low in the HNLC zone and near the Marquesas Islands.

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Distribution of micro-organisms along a transect in the South-East Pacific Ocean (BIOSOPE cruise) using epifluorescence microscopy

Biogeosciences ◽

10.5194/bg-5-311-2008 ◽

2008 ◽

Vol 5 (2) ◽

pp. 311-321 ◽

Cited By ~ 16

Author(s):

S. Masquelier ◽

D. Vaulot

Keyword(s):

Pacific Ocean ◽

Distribution Patterns ◽

Epifluorescence Microscopy ◽

The South ◽

Dapi Staining ◽

East Pacific ◽

Apparent Loss ◽

Ocean Gyre ◽

Micro Organisms ◽

East Pacific Ocean

Abstract. The distribution of selected groups of micro-organisms was analyzed along a South-East Pacific Ocean transect sampled during the BIOSOPE cruise in 2004. The transect could be divided into four regions of contrasted trophic status: a High Nutrient Low Chlorophyll (HNLC) region (mesotrophic) near the equator, the South-East Pacific Ocean gyre (hyper-oligotrophic), a transition region between the gyre and the coast of South America (moderately oligotrophic), and the Chile upwelling (eutrophic). The abundance of phycoerythrin containing picocyanobacteria (PE picocyanobacteria), autotrophic and heterotrophic eukaryotes (classified into different size ranges), dinoflagellates, and ciliates was determined by epifluorescence microscopy after DAPI staining. Despite some apparent loss of cells due to sample storage, distribution patterns were broadly similar to those obtained by flow cytometry for PE picocyanobacteria and picoeukaryotes. All populations reached a maximum in the Chile upwelling and a minimum near the centre of the gyre. The maximum abundance of PE picocyanobacteria was 70 103 cell mL−1. Abundance of autotrophic eukaryotes and dinoflagellates reached 24.5 103 and 20 cell mL−1, respectively. We observed a shift in the size distribution of autotrophic eukaryotes from 2–5 μm in eutrophic and mesotrophic regions to less than 2 μm in the central region. The contribution of autotrophic eukaryotes to total eukaryotes was the lowest in the central gyre. Maximum concentration of ciliates (18 cell mL−1) also occurred in the Chile upwelling, but, in contrast to the other groups, their abundance was very low in the HNLC zone and near the Marquesas Islands. Two key findings of this work that could not have been observed with other techniques are the high percentage of PE picocyanobacteria forming colonies in the HLNC region and the observation of numerous dinoflagellates with bright green autofluorescence.

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