Frontal Zones, Chlorophyll and Primary Production Patterns in the Surface Waters of the Southern Ocean South of Cape Town

Lütjeharms, J. R. E.; Allanson, B. R.; Parker, L.

doi:10.1016/s0422-9894(08)71041-9

Cited by 12 publications

(5 citation statements)

References 24 publications

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“…In late summer (February) chlorophyll a did not increase at the front and populations were dominated by nanophytoplankton (1-20 \xm). Earlier work south of South Africa also found that phytoplankton biomass (> 1.5 mg irr 3 ) and primary productivity (> 15 mg C m~3 li" 1 ) can be enhanced near the STC in summer (Lutjeharms et al 1986). Later work in the STC region in summer (January 1993 and1995) shows that biomass may also be lower (0.2-0.6 mg nf~3) and not necessarily enhanced in the STC relative to waters north and south unlike the winter situation (June 1993) where biomass was enhanced in the STC (Froneman et al 1996).…”

Section: Comparisonsmentioning

confidence: 80%

Size‐fractionated phytoplankton standing stocks and primary production during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand

Bradford‐Grieve

Chang

Gall

et al. 1997

New Zealand Journal of Marine and Freshwater Research

100

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Size-fractionated phytoplankton standing stocks and potential primary production (PPP) off the west and east coasts of South Island, New Zealand, were evaluated in austral winter and spring 1993. These are the first size-fractionated primary production data to be reported from the southern Subtropical Convergence (STC) and in oceanic New Zealand waters. Picophytoplankton (< 2 µm) formed > 30% of integrated chlorophyll a and daily PPP in most water types and seasons, except when the 20-200 µm size class dominated in west coast waters in spring and in the STC in winter and spring. In subtropical and STC waters, PPP was 30% higher than at similar latitudes in the North Atlantic Ocean. Interpretation of whether or not there was accumulation of chlorophyll a in the various water types and seasons depends on microzooplankton grazing, M96055 because mesozooplankton grazing and the proportion of chlorophyllous particulate matter sinking out of the upper water column was low. In the STC in spring, phytoplankton growth was slowing down (potential doubling times were at most 1.01 per day at 10 m and PPP per unit biomass was lower than in water masses to the north and south), probably because of decreasing concentrations of dissolved reactive silica. A sedimentation event of diatoms is postulated to have occurred in the STC soon after our spring sampling dates. The balance between algal growth and loss factors in the south-west Pacific depends on the unique combination of physical and chemical environmental conditions experienced there. The implications of the distribution of phytoplankton biomass and primary production by size-fraction for carbon export is discussed.

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Section: Comparisonsmentioning

confidence: 80%

Size‐fractionated phytoplankton standing stocks and primary production during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand

Bradford‐Grieve

Chang

Gall

et al. 1997

New Zealand Journal of Marine and Freshwater Research

100

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“…eastward at a latitude of about 408S in the South Indian Ocean Current (Stramma, 1992) leading to meso-scale meanders of the surface expression of the sub-tropical convergence (Froneman et al, 2007). The first two stations visited on our transit lie within this zone of intense mixing; a zone generally typified by high primary productivity of 1000 mg C m 22 day 21 (Lutjeharms et al, 1986;Machu et al, 2005) and punctuated by episodic plankton blooms with life spans of 2 -6 weeks that appear particularly in the austral spring and summer (Llido et al, 2005). The bloom and post-bloom characteristics observed on our western-most stations are consistent with this intermittent productivity scenario; both stations have similar high biomass (13.3 and 14.2 g C m 22), but very different primary production (1144 and 297 mg C m 22 day 21 ) and bacterial productions rates (40 and 155 mg C m 22 day 21 ).…”

Section: Discussionmentioning

confidence: 99%

Oceanography and the base of the pelagic food web in the southern Indian Ocean

Visser

Nielsen

Middelboe

et al. 2015

Journal of Plankton Research

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Processes governing productivity at the base of the pelagic food web of the southern Indian Ocean are influenced primarily by physical -chemical conditions with implications for the structure and function of the entire pelagic food web. Here, we report observations along a great circle transect from Cape Town, South Africa, to Broome in north western Australia. Primary production was tightly linked to water column stability and nutrient availability, with high productivity (1144 mg C m 22 day 21 ) in the sub-tropical convergence zone, and falling off by an order of magnitude in the sub-tropical gyre and tropical waters off northwest Australia. Primary production was largely confined to the GF/F fraction (GF/F .75% of total production and usually much higher) and the photosynthetic parameters showed adaption to the prevailing light levels. Bacterial production ranged from 19 to 155 mg C m 22 day 21 . No relationships were found between bacterial production and primary production or phytoplankton biomass and bacterial production seem more related to the state of the phytoplankton community as high bacterial production was observed in a post-bloom situation. The average BP:PP ratio was 31% (range 3.5-71%).

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“…, which coincides with a semi-permanent northward bulge in the Subtropical Convergence (Weeks & Shillington 1996), exhibiting enhanced concentrations of phytoplankton and of higher trophic levels (Lutjeharms et al 1986, Barange et al 1998). On the other hand, no enhanced biological activities were observed in the area at about 34°S, 35°E where 'Nemi' circled for 3 mo.…”

Section: Mesoscale Eddiesmentioning

confidence: 92%

Influence of ocean currents on long-distance movement of leatherback sea turtles in the Southwest Indian Ocean

Lambardi¹,

Lütjeharms²,

Mencacci³

et al. 2008

Mar. Ecol. Prog. Ser.

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Leatherback turtles Dermochelys coriacea spend most of their life in oceanic environments, whose physical and biological characteristics are primarily forged by sea current circulation. Water mass movements can mechanically act on swimming turtles, thus determining their routes, and can differentially distribute their planktonic prey. By integrating satellite tracking data with contemporaneous remote-sensing information, we analysed the post-nesting journeys of 9 leatherbacks with respect to oceanographic surface conditions. Tracked turtles showed large variations in migration routes and in final destinations, apparently without heading for specific foraging areas. Their complex tracks spread over wide regions around South Africa. Leatherbacks were greatly influenced by the currents encountered during their movements, with their trajectories displaying curves or revolutions in the presence of (and in accordance with) rotating water masses. An impressive similarity was observed between large parts of the turtle routes and those of surface drifters tracked in the same regions. Finally, leatherbacks remained associated for long periods with specific oceanographic features, which most probably offered them profitable foraging opportunities. These results agree with previous findings in showing a strong influence of oceanic currents and mesoscale features on the movements of South African leatherbacks, and additionally identify the role of current-related features in causing the observed route variability and in determining high-quality foraging hotspots for leatherbacks moving in the ocean.

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Frontal Zones, Chlorophyll and Primary Production Patterns in the Surface Waters of the Southern Ocean South of Cape Town

Cited by 12 publications

References 24 publications

Size‐fractionated phytoplankton standing stocks and primary production during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand

Size‐fractionated phytoplankton standing stocks and primary production during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand

Oceanography and the base of the pelagic food web in the southern Indian Ocean

Influence of ocean currents on long-distance movement of leatherback sea turtles in the Southwest Indian Ocean

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