Swarming and Behaviour in Antarctic Krill

Tarling, Geraint A.; Fielding, Sophie

doi:10.1007/978-3-319-29279-3_8

Cited by 44 publications

(32 citation statements)

References 134 publications

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“…Even though all krill are much larger than many planktonic species, they are often regarded as plankton, however the strong swimming abilities of adult krill are a characteristic feature of nekton 130 . Krill form some of the largest monospecific aggregations (swarms) in the animal kingdom 131 , making them a critical food item for whales, seals and seabirds, and the target of the Southern Ocean's largest fishery. E. superba themselves are a major grazer of primary production in the Southern Ocean 68 .…”

Section: Krill and Biogeochemical Cyclesmentioning

confidence: 99%

The importance of Antarctic krill in biogeochemical cycles

et al. 2019

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Antarctic krill (Euphausia superba) are swarming, oceanic crustaceans, up to two inches long, and best known as prey for whales and penguinsbut they have another important role. With their large size, high biomass and daily vertical migrations they transport and transform essential nutrients, stimulate primary productivity and influence the carbon sink. Antarctic krill are also fished by the Southern Ocean's largest fishery. Yet how krill fishing impacts nutrient fertilisation and the carbon sink in the Southern Ocean is poorly understood. Our synthesis shows fishery management should consider the influential biogeochemical role of both adult and larval Antarctic krill. O cean biogeochemical cycles are paramount in regulating atmospheric carbon dioxide (CO 2) levels and in governing the nutrients available for phytoplankton growth 1. As phytoplankton are essential in most marine food webs, biogeochemistry is also important in fuelling fishery production 2. The role of phytoplankton in atmospheric CO 2 drawdown and fish production has been the central focus of many biogeochemical studies (e.g., refs. 3,4). However, despite evidence of their potential importance, higher organisms (metazoa) such as zooplankton (e.g., copepods and salps), nekton (e.g., adult krill and fish), seabirds and mammals 5-12 , have received less attention concerning their roles in the global biogeochemical cycles. One of the main mechanisms by which metazoa can influence biogeochemical cycles is through the biological pump 1 (Fig. 1). The biological pump describes a suite of biological processes that ultimately sequester atmospheric CO 2 into the deep ocean on long timescales. During photosynthesis in the surface, ocean phytoplankton produce organic matter and a fraction (< 40 %) sinks to deeper waters 13. It is estimated that 5-12 Gt C is exported from the global surface ocean annually 14 , with herbivorous metazoa contributing to the biological pump by releasing fast-sinking faecal pellets, respiring carbon at depth originally assimilated in the surface ocean and by excreting nutrients near the surface promoting further phytoplankton

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Section: Krill and Biogeochemical Cyclesmentioning

confidence: 99%

The importance of Antarctic krill in biogeochemical cycles

et al. 2019

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“…In addition to the seasonal shift , we also observed daily shifts in krill distributions and movement behaviors. In particular, we noted vertical distribution patterns akin to diel vertical migration (DVM) in both seasons, with maximum abundances of krill found shallower at night than during the day; in late autumn, we also observed evidence of DVM at one station monitored over 13 h. Krill in the Southern Ocean exhibit DVM throughout the year, although DVM is highly variable and in some studies not detected (Godlewska ; Siegel ; Siegel and Watkins ; Tarling and Fielding ). Remarkably, while we observed shifts in vertical distributions in the late autumn associated with changes in light, krill were found at depths generally considered beyond krill eye sensory capacity for light perception (Hiller‐Adams and Case ).…”

Section: Discussionmentioning

confidence: 62%

Krill motion in the Southern Ocean: quantifying in situ krill movement behaviors and distributions during the late austral autumn and spring

Kane

Yopak

Roman

et al. 2018

Limnology & Oceanography

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Krill movement behaviors and vertical distributions were measured in spring and autumn using a profiling stereo‐camera and environmental sensor system to quantify seasonal changes in the role of krill in Southern Ocean food webs. Krill were observed in May–June 2013 and December 2014 in 3 bays in the Western Antarctic Peninsula. Krill abundances and movement behaviors were determined from in situ image sequences collected for up to 10 min throughout the water column, up to 625 m deep; 3,345 individual krill tracks were collected. Seasonal changes in individual krill behaviors coincided with seasonal shifts in krill vertical distributions. During late spring, net upward swimming direction (0.9 ± 2.1° from horizontal) and vertical velocity (0.3 ± 0.2 body lengths [BL] s−1) resulted in shallower maximum abundances of krill within the water column proximate to near‐surface phytoplankton distributions. During late autumn, krill swimming patterns tended downward, including swimming direction (−5.2 ± 0.8° from horizontal) and vertical velocity (−0.1 ± 0.0 BL s−1), leading to deeper distributions proximate to the benthos. Individual krill motility was greater in spring than autumn, as evidenced by an increase in swimming speeds (5.4 ± 0.2 vs. 2.8 ± 0.0 BL s−1) and turning rates (120 ± 5 vs. 107 ± 2° s−1). Remarkably, krill in autumn were capable of swimming as quickly as krill in spring. These results suggest seasonal shifts in krill movement behaviors have direct ramifications for krill distributions, proximity to food sources, and impacts on biogeochemical cycling in coastal Antarctic waters.

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“…Accurate measurements of krill FP egestion rates are not easy to obtain due to the complex behaviour of krill and the difficulty in replicating natural conditions Tarling and Fielding 2016). We did not directly measure krill FP egestion rates which increase the uncertainty in our calculated b FPP .…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…However, the patchy distribution of krill swarms and the highly variable composition and sinking velocities of the FP Atkinson et al 2012) mean that their contribution to flux can be episodic and, therefore, difficult to sample. In addition, the complex behaviour of krill makes it difficult to replicate natural conditions in the laboratory (Gibbons et al 1999;Tarling and Fielding 2016). Overall, this potentially large flux of POC to the mesopelagic of the Southern Ocean is poorly quantified and it is not yet clear from previous studies whether krill FP are transferred efficiently through the upper mesopelagic.…”

Section: Introductionmentioning

confidence: 99%

The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring

et al. 2017

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) and attenuation to estimates of krill FP production based on previous measurements of krill density and literature FP egestion rates, and estimated net krill FP attenuation rates in the upper mesopelagic. Calculated attenuation rates are sensitive to krill densities in the overlying water column but suggest that krill FP could be transferred efficiently through the upper mesopelagic, and, in agreement with our MSC attenuation estimates, could make large contributions to bathypelagic POC fluxes. Our study contrasts with some others which suggest rapid FP attenuation, highlighting the need for further work to constrain attenuation rates and assess how important the contribution of Antarctic krill FP could be to the Southern Ocean biological carbon pump.

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Swarming and Behaviour in Antarctic Krill

Cited by 44 publications

References 134 publications

The importance of Antarctic krill in biogeochemical cycles

The importance of Antarctic krill in biogeochemical cycles

Krill motion in the Southern Ocean: quantifying in situ krill movement behaviors and distributions during the late austral autumn and spring

The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring

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