Primary production and carbon uptake dynamics in the vicinity of South Georgia-balancing carbon fixation and removal

Gilpin, Linda; Priddle, J.; Whitehouse, M. J.; Savidge, Graham; Atkinson, Angus

doi:10.3354/meps242051

Cited by 20 publications

(13 citation statements)

References 59 publications

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“…Regressions between all parameters were highly significant (p < 0.001) with R 2 values ≥ 87%. This relationship concurs with previous measurements in this area (see Gilpin et al 2002 in showing a good correlation between surface data and those collected within the top 50 m of the water column. Table 1.…”

Section: Surface Data Compared To the Top 50 M Of The Water Columnsupporting

confidence: 81%

Role of krill versus bottom-up factors in controlling phytoplankton biomass in the northern Antarctic waters of South Georgia

Whitehouse

Atkinson²,

Ward³

et al. 2009

Mar. Ecol. Prog. Ser.

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The extent to which Antarctic phytoplankton stocks are controlled by 'bottom-up' and/or 'top-down' factors is highly variable. Here we consider data collected at South Georgia during 3 summer surveys that recorded substantial hydrographic variability. A suite of bottom-up and top-down controlling factors were measured simultaneously at the mesoscale. Sea surface temperature varied by > 2°C, macronutrients ranged from near-winter concentrations to near-depleted, while mean densities of a major grazer, krill Euphausia superba, varied between near-zero and > 400 g wet mass m -2 . A general linear model was used to identify the main factors implicated in the observed differences in phytoplankton biomass. Despite east-to-west and on-to off-shelf temperature gradients, temperature per se was not implicated in phytoplankton variability. Also, while there was an abundance of NO 3 -N in surface waters, NH 4 -N was the key nutrient throughout. A domed relationship between phytoplankton and krill peaked between 2 and 4 mg chlorophyll a m -3 and 6 and 30 g krill m -2 . The positive side of this dome was represented by the west off-shelf region downstream of South Georgia. Here, an ample supply of micro-and macronutrients promoted high primary production, and low densities of krill presumably had little grazing effect. This positive relationship between krill and phytoplankton biomasses was interpreted as krill accumulating in areas of good feeding conditions. The negative side of the dome was typified by the east off-shelf region, where macronutrients remained high, primary production rates were low, and krill densities were very high. The grazing rates calculated here suggested that krill affect their food stocks severely, and the negative krill-phytoplankton relationship in this region may reflect locally high krill densities driving down their food supply.

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Section: Surface Data Compared To the Top 50 M Of The Water Columnsupporting

confidence: 81%

Role of krill versus bottom-up factors in controlling phytoplankton biomass in the northern Antarctic waters of South Georgia

Whitehouse

Atkinson²,

Ward³

et al. 2009

Mar. Ecol. Prog. Ser.

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“…Its absence around SG may be related to elevated chlorophyll-a concentrations usually present in the area (GILPIN et al, 2002;ATKINSON et al, 2001). High phytoplankton concentrations can cause the clogging of the salps' filter feeding system (HARBISON; MCALISTER, 1979) which may lead to the inability to feed.…”

Section: Discussionmentioning

confidence: 99%

“…The high chlorophyll-a concentrations frequently recorded in the area around SG (GILPIN et al, 2002;ATKINSON et al, 2001) may be related to the high concentrations of nutrients introduced from the east, via the SACCF (KORB et al 2004) and may be associated with the remarkably high density and frequency of pteropod species, especially L. helicina and L. Retrovers, to the south of SG. These phytoplankton blooms support a high biomass of filter-feeding zooplankton such as krill, copepods and pteropods, which may, in their turn, support high densities of predators like E. hamata and S. gazellae.…”

Section: Discussionmentioning

confidence: 99%

“…Many studies have highlighted the high biological productivity around the South Georgia Islands (WARD et al, 2002(WARD et al, , 2003GILPIN et al, 2002;ATKINSON et al, 2001;WHITEHOUSE et al, 1996;ATKINSON;PECK, 1988) and, to a lesser extent, the South Orkney Islands (SIGLEO et al, 2000). Research has been focused mainly on euphausiids (particularly Euphausia superba) and copepods, (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Distribution patterns of chaetognata, polychaeta, pteropoda and salpidae off south georgia and south orkney islands

et al. 2010

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The distribution pattern, frequency and density (ind./1000 m) of different mesozooplankton species from the South Georgia Islands, South Orkney Islands and the Weddell-Scotia Confluence were analyzed using data obtained in 1994. The maximum densities of the species found were: Eukrohnia hamata (5330), Sagitta gazellae (1052), Clione limacina antarctica (450), Spongiobranchaea australis (375), Clio sulcata (100), Limacina helicina (4076 x 10³), Limacina retroversa (71 x 10(4)), Pelagobia longicirrata (29170), Rhynchonereella bongraini (117), Tomopteris carpenterii (26), Tomopteris planktonis (498), Tomopteris septentrionales (498) and Salpa thompsoni (189). Species density and frequency decreased from South Georgia to the South Orkney Islands, recording intermediate values at the Weddell-Scotia Confluence. Species density in the South Orkney area seemed to be limited by variations in temperature and salinity. The southern area around South Georgia showed the highest density of species, probably due to the influence of the Southern Front of the Antarctic Circumpolar Current. The presence of species characteristic of sub-Antarctic waters such as L. retroversa in the Confluence area could be related to the southward movements of eddies that originate in the Polar Front.
Foram analisados os padrões de distribuição, freqüência e densidade (ind. 1000 m) de diferentes espécies de mesozooplâncton encontradas em torno das ilhas Georgias e Orcadas del Sur no verão de 1994. As densidades máximas apresentadas pelas espécies principais foram: Eukrohnia hamata (5330), Sagitta gazellae (1052), Clione limacina antarctica (450), Spongiobranchaea australis (375), Clio sulcata (100), Limacina helicina (4076 x 10³), Limacina retroversa (71 x 10(4)); Pelagobia longicirrata (29170), Rhynchonereella bongraini (117), Tomopteris carpenterii (26), Tomopteris planktonis (498), Tomopteris septentrionales (498) y Salpa thompsoni (189). A densidade e freqüência das espécies diminuíram das ilhas Georgias em direção às Orcadas, registrando-se valores médios na confluência Weddell-Scotia. A densidade de espécies nas Orcadas parece estar limitada pelas variações na temperatura e salinidade. Nas Georgias, a área sul mostrou a maior densidade de espécies, e isto poderia ser devido a influência da Frente sul da Corrente Circumpolar Antártica. A presença de espécies características de águas sub-antárticas (Ex. L. helicina) na confluência Weddel-Scotia poderia estar relacionada com o movimento dos vórtices da Frente Polar em direção Sul

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“…This study is the first to apply stable isotopic analyses to the study of the food webs of Antarctic soil ecosystems, although analogous studies have been successfully applied to Antarctic marine food webs (Kaehler et al 2000;Gilpin et al 2002;Jacob et al 2006). This study had the primary aim of obtaining a better understanding of dietary selection in the most abundant isotomid springtail and oribatid mite of this region.…”

Section: Food Choice Of Antarctic Soil Arthropodsmentioning

confidence: 99%

Food choice of Antarctic soil arthropods clarified by stable isotope signatures

et al. 2007

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Antarctic soil ecosystems are amongst the most simplified on Earth and include only few soil arthropod species, generally believed to be opportunistic omnivorous feeders. Using stable isotopic analyses, we investigated the food choice of two common and widely distributed Antarctic soil arthropod species using natural abundances of 13 C and 15 N and an isotope labelling study. In the laboratory we fed the isotomid springtail Cryptopygus antarcticus six potential food sources (one algal species, two lichens and three mosses). Our results showed a clear preference for algae and lichens rather than mosses. These results were corroborated by field data comparing stable isotope signatures from the most dominant cryptogams and soil arthropods (C. antarcticus and the oribatid mite Alaskozetes antarcticus). Thus, for the first time in an Antarctic study, we present clear evidence that these soil arthropods show selectivity in their choice of food and have a preference for algae and lichens above mosses.

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Primary production and carbon uptake dynamics in the vicinity of South Georgia-balancing carbon fixation and removal

Cited by 20 publications

References 59 publications

Role of krill versus bottom-up factors in controlling phytoplankton biomass in the northern Antarctic waters of South Georgia

Role of krill versus bottom-up factors in controlling phytoplankton biomass in the northern Antarctic waters of South Georgia

Distribution patterns of chaetognata, polychaeta, pteropoda and salpidae off south georgia and south orkney islands

Food choice of Antarctic soil arthropods clarified by stable isotope signatures

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