Inter-annual sea-ice dynamics and micro-algal biomass in winter pack ice of Marguerite Bay, Antarctica

Fritsen, Christian H.; Memmott, Jeramie; Stewart, Frank J.

doi:10.1016/j.dsr2.2008.04.034

Cited by 36 publications

(29 citation statements)

References 36 publications

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“…Concentrations of chl a within the sea ice and water column in the pack-ice zone found during our study were consistent with previous data from the Weddell Sea and other regions of the Southern Ocean in winter (western Antarctic Peninsula region, northwestern Weddell Sea, Lazarev Sea, East Antarctica) 8,[13][14][15][23][24][25][26] . Previous larval krill winter studies in the western Antarctic Peninsula region demonstrate significantly different growth rates between years, at the same time and location, due to variable chl a concentration in the water column.…”

Section: Nature Ecology and Evolutionsupporting

confidence: 92%

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

et al. 2017

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A ntarctic krill Euphausia superba, a key species in Southern Ocean food webs 1 , plays a central role in ecosystem processes and community dynamics of apex predators, and is the target of a commercial fishery 2 . Krill spawn in late spring and their larvae develop during summer, autumn and under the ice in winter to emerge as juveniles in the following spring. The newly spawned eggs sink from the surface to up to 1,000 m depth where they hatch and the developing larvae actively swim upwards to feed in the upper water column 1 . Larval Antarctic krill have low lipid reserves, which are insufficient to support long periods of starvation. Therefore, winter, when primary production is minimal, is assumed to be a critical bottleneck for larval krill development and hence recruitment to the adult population 3,4 . Present hypotheses suggest that high algal biomass in winter sea ice enhances larval krill winter-feeding conditions and growth [5][6][7][8] . This implies that larvae have access to this high algal biomass within the sea ice. However, recent observations 9,10 indicate that the linkage between sea ice and krill recruitment success is not as direct as has been suggested. The timing of ice-edge advance and annual ice-season duration is highly variable, and does not necessarily show a clear link to krill recruitment in the following year ( Supplementary Figs. 1 and 2). Along the Antarctic Peninsula, adult krill have a five to six year population cycle with oscillations in biomass exceeding an order of magnitude 9 . According to bioenergetics models, part of the variability is due to interannual variation in reproductive output 11 as well as autumn blooms that may govern the possible overwinter survival rate of larvae 11,12 . In the Bransfield Strait, three krill winter surveys have shown that krill abundance is an order of magnitude higher than in summer, regardless of concurrent sea-ice conditions 10 A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protection from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.

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Section: Nature Ecology and Evolutionsupporting

confidence: 92%

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

et al. 2017

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“…However, the ongoing warming trend at the WAP region has caused a more frequent miss-match in timing of the occurrence of high phytoplankton concentrations in the water column and the start of sea ice formation . Sea ice formation in the WAP region in April resulted in a tenfold higher Chl a content of the sea ice compared with late formation end of June (Fritsen et al 2008). Furthermore, the shorter the sea ice duration during winter, the thinner and more un-deformed is the ice.…”

Section: Annual Life Cycle In Changing Southern Ocean Environmentmentioning

confidence: 93%

“…Large lipid stores at the onset of winter might also promote external maturation (thelycum development) during winter and internal maturation (early ovarian development) in early spring, even in years when phytoplankton bloom is delayed . In autumn, timing of sea ice formation is crucial, since the earlier sea ice forms, the more algal biomass are usually incorporated (Fritsen et al 2008). Moreover, earlier ice formation means greater total light availability for the ice algae to grow before mid-winter (when light levels are mostly too low for primary production) Fritsen et al 2011).…”

Section: Annual Life Cycle In Changing Southern Ocean Environmentmentioning

confidence: 99%

The overwintering of Antarctic krill, Euphausia superba, from an ecophysiological perspective

2011

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A major aim of this review is to determine which physiological functions are adopted by adults and larvae to survive the winter season with low food supply and their relative importance. A second aim is to clarify the extent to which seasonal variation in larval and adult krill physiology is mediated by environmental factors with a strong seasonality, such as food supply or day light. Experimental studies on adult krill have demonstrated that speciWc physiological adaptations during autumn and winter, such as reduced metabolic rates and feeding activity, are not caused simply by the scarcity of food, as was previously assumed. These adaptations appear to be inXuenced by the local light regime. The physiological functions that larval krill adopt during winter (reduced metabolism, delayed development, lipid utilisation, and variable growth rates) are, in contrast to the adults, under direct control by the available food supply. During winter, the adults often seem to have little association with sea ice (at least until early spring). The larvae, however, feed within sea ice but mainly on the grazers of the ice algal community rather than on the algae themselves. In this respect, a miss-match in timing of the occurrence of the last phytoplankton blooms in autumn and the start of the sea ice formation, as has been increasingly observed in the west Antarctic Peninsula (WAP) region, will impact larval krill development during winter in terms of food supply and consequently the krill stock in this region.

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“…Generally, in 2002 the ice cores contained an order of magnitude more chlorophyll a than in 2001 (Fritsen et al, 2008), leading us to suggest that more food was available to larval krill in 2002 than 2001. The median pigment content and in situ growth rates were also higher in larval krill in 2002 than in 2001.…”

Section: Contrast Two Yearsmentioning

confidence: 99%

“…In fact, the ability to do simultaneous sampling both from the topside and underside of the ice fl oes made for effi cient sampling and better linkage between data sets. During ice camps on two winter cruises for Southern Ocean GLOBEC west of the Antarctic peninsula in 2001 and 2002 (methods and results described in Quetin et al, 2007), total integrated chlorophyll a in multiple ice cores (Fritsen et al, 2008) was measured on the same ice fl oes where larval krill were collected by scuba divers. The amount of chlorophyll a in the ice cores was used as a proxy for the SIMCOs available as food to the larval krill living on the underside of the pack ice.…”

Section: Ice Campsmentioning

confidence: 99%

Life Under Antarctic Pack Ice: A Krill Perspective

Quetin¹,

Ross²

2009

Smithsonian at the Poles : Contributions to International Polar Year Science

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Inter-annual sea-ice dynamics and micro-algal biomass in winter pack ice of Marguerite Bay, Antarctica

Cited by 36 publications

References 36 publications

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

The overwintering of Antarctic krill, Euphausia superba, from an ecophysiological perspective

Life Under Antarctic Pack Ice: A Krill Perspective

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