Krill ( Euphausia superba ) density, proportional and absolute recruitment and biomass in the Elephant Island region (Antarctic Peninsula) during the period 1977 to 1997

Siegel, Volker; Loeb, Valerie J.; Gröger, Joachim Paul

doi:10.1007/s003000050264

Cited by 79 publications

(51 citation statements)

References 8 publications

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“…Systematic gaps due to missing age classes in krill population structure have been reported for the King George Island (Fraser & Trivelpiece 1995a,b) and Elephant Island ( Fig. 1; and Siegel et al 1998and Siegel et al , 2002 regions. These gaps also show a pattern of episodic recruitment every 4 to 5 yr, including intervening years in which age 1+ krill are rare or completely absent.…”

Section: Krill Population Size-age Structurementioning

confidence: 73%

“…This is implicit in the systematic increase in krill size classes as ice cycles progressed annually through an approximately 4 to 5 yr period. Because multiple age classes would buffer the population from exhibiting these systematic changes , Siegel et al 1998, Reid et al 1999a, Murphy & Reid 2001, however, a key implication is that strong age classes exhibited a common pattern of rare occurrence during the time series integrated by the analyses. The concordance in periodicities between years of extensive winter sea ice in the WAP (Fig.…”

Section: Krill Population Size-age Structurementioning

confidence: 99%

“…For example, the lowest krill abundances in the Elephant Island time series were recorded in 1990 (Table 5); biomass and density anomalies also changed from predominantly positive before 1985 to negative after 1987 through 1995 (Siegel et al 1998). Based on data of Woehler et al (2001), Adélie penguin populations at 2 WAP localities (Palmer Station and King George Island) and in the South Orkney Islands (Signy Island) to the east were stable or increasing through the late 1980s and have decreased significantly post-1990.…”

Section: Implications: Krill Longevity Climate Warming and Ecosystemmentioning

confidence: 99%

“…However, given the essential role of krill in this ecosystem, and the rate at which climate is warming the region, lifespan may also be viewed as the 'weak link' in the mechanistic processes maintaining ecosystem structure and function. This is because multiple age classes buffer the population from rapid changes in abundance (Siegel et al 1998), yet the trend since the early 1980s signals a transition towards populations in which age class structure is dominated by single, strong cohorts (e.g. Table 3).…”

Section: Implications: Krill Longevity Climate Warming and Ecosystemmentioning

confidence: 99%

See 3 more Smart Citations

A predator's perspective on causal links between climate change, physical forcing and ecosystem response

Fraser¹,

Hofmann²

2003

Mar. Ecol. Prog. Ser.

231

242

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ABSTRACT:The mechanisms by which variability in sea ice cover and its effects on the demography of the Antarctic krill Euphausia superba cascade to other ecosystem components such as apex predators remain poorly understood at all spatial and temporal scales, yet these interactions are essential for understanding causal links between climate change, ecosystem response and resource monitoring and management in the Southern Ocean. To address some of these issues, we examined the longterm foraging responses of Adélie penguins Pygoscelis adeliae near Palmer Station, western Antarctic Peninsula, in relation to ice-induced changes in krill recruitment and availability. Our results suggest that (1) there is a direct, causal relationship between variability in ice cover, krill recruitment, prey availability and predator foraging ecology, (2) regional patterns and trends detected in this study are consistent with similar observations in areas as far north as South Georgia, and (3) largescale forcing associated with the Antarctic Circumpolar Wave may be governing ecological interactions between ice, krill and their predators in the western Antarctic Peninsula and Scotia Sea regions. Another implication of our analyses is that during the last 2 decades in particular, krill populations have been sustained by strong age classes that emerge episodically every 4 to 5 yr. This raises the possibility that cohort senescence has become an additional ecosystem stressor in an environment where ice conditions conducive to good krill recruitment are deteriorating due to climate warming. In exploring these interactions, our results suggest that at least 1 'senescence event' has already occurred in the western Antarctic Peninsula region, and it accounts for significant coherent decreases in krill abundance, predator populations and predator foraging and breeding performance. We propose that krill longevity should be incorporated into models that seek to identify and understand causal links between climate change, physical forcing and ecosystem response in the western Antarctic Peninsula region.

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Section: Krill Population Size-age Structurementioning

confidence: 73%

Section: Krill Population Size-age Structurementioning

confidence: 99%

Section: Implications: Krill Longevity Climate Warming and Ecosystemmentioning

confidence: 99%

Section: Implications: Krill Longevity Climate Warming and Ecosystemmentioning

confidence: 99%

See 2 more Smart Citations

A predator's perspective on causal links between climate change, physical forcing and ecosystem response

Fraser¹,

Hofmann²

2003

Mar. Ecol. Prog. Ser.

231

242

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“…1(a)] has been linked to recruitment failure of different year classes (Siegel and Loeb, 1995). It has been proposed that this variability is related to sea-ice extent and duration (Marr, 1962;Loeb et al, 1997;Siegel et al, 1998). Research at Bird Island, just west of South Georgia [ Fig.…”

Section: Introductionmentioning

confidence: 99%

Variability of the southern Antarctic Circumpolar Current front north of South Georgia

Thorpe

Heywood

Brandon

et al. 2002

Journal of Marine Systems

113

108

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South Georgia ( f 54jS, 37jW) is an island in the eastern Scotia Sea, South Atlantic that lies in the path of the Antarctic Circumpolar Current (ACC). The southern ACC front (SACCF), one of three major fronts associated with the ACC, wraps anticyclonically around South Georgia and then retroflects north of the island. This paper investigates temporal variability in the position of the SACCF north of South Georgia that is likely to have an effect on the South Georgia ecosystem by contributing to the variability in local krill abundance.A meridional hydrographic section that crossed the SACCF three times demonstrates that the SACCF is associated with a geopotential anomaly of 4.5 J kg À 1 in the eastern Scotia Sea. A high resolution (1/4j Â 1/4j) map of historical geopotential anomaly shows the mean position of the SACCF retroflection north of South Georgia to be at 36jW, 400 km further east than in previous work. It also reveals temporal variability associated with the SACCF in the South Georgia region. A near-surface drifter provides evidence for variability in the western extent of the SACCF north of South Georgia and for the presence of eddies in the region. Output from a 3-year (1993 -1995) high frequency wind forced run of the eddy-permitting Ocean Circulation and Climate Advanced Modelling project (OCCAM) model, used to investigate the frontal variability, shows two periods of anomalous westward extent of the SACCF north of South Georgia and associated eddy-shedding. The SACCF variability affects the near-surface transport of passive drifters into the region with implications for the South Georgia ecosystem. D

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Management of Krill Fisheries in the Southern Ocean

Miller¹,

Agnew²

2000

Krill

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Krill ( Euphausia superba ) density, proportional and absolute recruitment and biomass in the Elephant Island region (Antarctic Peninsula) during the period 1977 to 1997

Cited by 79 publications

References 8 publications

A predator's perspective on causal links between climate change, physical forcing and ecosystem response

A predator's perspective on causal links between climate change, physical forcing and ecosystem response

Variability of the southern Antarctic Circumpolar Current front north of South Georgia

Management of Krill Fisheries in the Southern Ocean

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