Krill behaviour as recorded by acoustic doppler current profilers in the Gullmarsfjord

Liljebladh, Bengt; Thomasson, Maria A.

doi:10.1016/s0924-7963(00)00075-0

Cited by 29 publications

(23 citation statements)

References 31 publications

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“…Northern krill performs diel vertical migrations, from 100 m (in Scandinavian or Scottish fjords) to > 800 m (in the Mediterranean) (Liljebladh & Thomasson 2001. In sub-arctic waters, Meganyctiphanes norvegica is considered to be one of the most important vertical migrators (Roe & Griffiths 1993).…”

Section: Digestive Enzymesmentioning

confidence: 99%

Food utilization of two pelagic crustaceans in the Greenland Sea: Meganyctiphanes norvegica (Euphausiacea) and Hymenodora glacialis (Decapoda, Caridea)

Kreibich¹,

Hagen²,

Saborowski³

2010

Mar. Ecol. Prog. Ser.

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Large pelagic crustaceans from Greenland Sea waters, the northern krill Meganyctiphanes norvegica (Euphausiacea) and the decapod shrimp Hymenodora glacialis (Caridea), were captured in depths down to 1500 m and studied with respect to their physiological food utilization abilities. Both species showed distinct differences in the amount of total lipids (TLs), lipid class and fatty acid (FA) compositions as well as proteolytic enzyme activities. In M. norvegica, the overall amount of TLs and storage lipids was much lower than in H. glacialis, and triacylglycerols formed the major lipid fraction with a mean of 48% TLs. Major FAs comprised the trophic markers 20:1(n-9) and 22:1(n-11), indicating the ingestion of calanid copepods. Additionally, the FAs 22:6(n-3), 18:1(n-9) and 16:0 prevailed. In H. glacialis, TLs (mean = 44% dry mass) were about twice as high as in krill, with wax esters comprising up to 89% TLs. H. glacialis seems to accumulate these lipids as energy reserves to survive periods of food limitation. Moreover, high lipid levels, particularly wax esters, also help to maintain neutral buoyancy. The major FA in H. glacialis was 18:1(n-9); other dominant FAs were 20:1(n-9) and 22:1(n-11), typical of calanid copepods, as well as the diatom trophic marker 16:1(n-7). Both species showed omnivorous feeding behaviour with a strong tendency towards carnivory. Total proteolytic activities in midgut gland tissue were higher in M. norvegica than in H. glacialis. In M. norvegica, proteinases were dominated by serine proteinases, whereas cysteine proteinases formed the major group in H. glacialis. High proteolytic activity in M. norvegica indicates a high digestive potential for proteins and efficient utilization of prey. The presence of different proteinase classes in both species may be due to different group-specific enzyme expression patterns between euphausiids and caridean decapods. Both species follow highly deviating life strategies, as reflected by their specific lipid and enzymatic characteristics.

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Section: Digestive Enzymesmentioning

confidence: 99%

Food utilization of two pelagic crustaceans in the Greenland Sea: Meganyctiphanes norvegica (Euphausiacea) and Hymenodora glacialis (Decapoda, Caridea)

Kreibich¹,

Hagen²,

Saborowski³

2010

Mar. Ecol. Prog. Ser.

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“…Hypoxia may also play a role in affecting DVM in some shallow coastal areas, especially those suffering from eutrophication, such as the Gulf of Mexico and the Chesapeake Bay Pierson et al 2009). However, in deeper, offshore ocean waters where subsurface suboxic conditions occur (e.g., oxygen minimum or ''dead zones''), a suppression in zooplankton DVM has more often been observed (Smith et al 1998;Mincks et al 2000;Liljebladh and Thomasson 2001). These hypoxic zones are also often areas of lower transparency caused by increased particle accumulation or reduced particle degradation.…”

mentioning

confidence: 99%

Toward a more comprehensive theory of zooplankton diel vertical migration: Integrating ultraviolet radiation and water transparency into the biotic paradigm

Williamson

Fischer

Bollens

et al. 2011

Limnology & Oceanography

190

202

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The current prevailing theory of diel vertical migration (DVM) of zooplankton is focused largely on two biotic drivers: food and predation. Yet recent evidence suggests that abiotic drivers such as damaging ultraviolet (UV) radiation and temperature are also important. Here we integrate current knowledge on the effects of abiotic factors on DVM with the current biologically based paradigm to develop a more comprehensive framework for understanding DVM in zooplankton. We focus on ''normal'' (down during the day, up at night) DVM of holoplanktonic, primarily herbivorous zooplankton. This new transparency-regulator hypothesis differentiates between structural drivers, such as temperature and food, that vary little over a 24-h period and dynamic drivers, such as damaging UV radiation and visual predation, that show strong variation over a 24-h period. This hypothesis emphasizes the central role of water transparency in regulating these major drivers of DVM. In less transparent systems, temperature and food are often optimal in the surface waters, visual predators are abundant, and UV radiation levels are low. In contrast, in more transparent systems, vertical thermal gradients tend to be more gradual, food quality and quantity are higher in deeper waters, and visual predator abundance is often lower and damaging UV radiation higher in the surface waters. This transparency-regulator hypothesis provides a more versatile theoretical framework to explain variation in DVM across waters of differing transparency. This hypothesis also enables clearer predictions of how the wide range of ongoing transparency-altering local, regional, and global environmental changes can be expected to influence DVM patterns in both inland and oceanic waters of the world.Diel vertical migrations (DVM) of zooplankton in the world's lakes and oceans comprise some of the most widespread and massive migrations of animals on Earth. These striking migrations across strong vertical habitat gradients have inspired numerous ecological and evolutionary studies addressing mechanisms of habitat selection and consequences for species interactions. These migrations also have important implications for water quality and fisheries production as well as biogeochemical cycling. Natural and anthropogenic environmental changes, such as shifting local land use patterns and regional to global climate change, are altering water transparency and have the potential to affect DVM in lakes and oceans worldwide. The purpose of this article is to provide a common theoretical framework for understanding variation in the drivers of DVM across transparency gradients with a particular emphasis on recent advances in our understanding of the role of ultraviolet radiation (UV).Many environmental factors are recognized as providing both important proximate cues as well as ultimate consequences of adaptive significance for DVM, including light, temperature, food availability, and predation pressures (Table 1; Lampert 1989;Ringelberg 1993;Hays 2003). In spite of the wides...

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“…In contrast to bottom dwelling prey, krill appear to have been eaten around dawn and in the afternoon and early evening hours. Krill migrate towards the surface at night while daylight hours are spent in the lower pelagic or demersal layers (Onsrud & Kaartvedt 1998, Tarling et al 2000, Liljebladh & Thomasson 2001. The ascent to the pelagic appears to take place around 1 h after sunset, whereas the descent occurs at dawn (Liljebladh & Thomasson 2001) and this was reflected in the intake of this prey (dawn to some hours after dusk).…”

Section: Discussionmentioning

confidence: 99%

“…Variation in the contribution of copepods, amphipods, isopods and unidentified crustaceans to the group of 'other crustaceans' may lead to great differences in the diel pattern as their behaviour differs markedly (Ansell et al 1999, Bergström 2000, Liljebladh & Thomasson 2001. It is therefore not surprising that no common diel pattern in the occurrence of this prey group was found.…”

Section: Dabmentioning

confidence: 99%

“…Generally speaking, food intake reflects a combination of prey preferences of the predator and encounter rate with the different prey (Manly et al 1972, Chesson 1978, Bres 1989, Buckel & Stoner 2000. Encounter rate is likely to change through the diel cycle as a number of prey species exhibit diel changes in behaviour (Ansell et al 1999, Bergström 2000, Liljebladh & Thomasson 2001. Diel changes in total food intake have been examined by combining observations of total stomach content with digestion models (Hall et al 1995) while changes in food composition have been examined by investigating the amount or occurrence of different prey in stomachs round the clock (Albert 1995, Pillar & Barange 1997.…”

Section: Introductionmentioning

confidence: 99%

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Diel feeding pattern of whiting in the North Sea

Rindorf¹

2003

Mar. Ecol. Prog. Ser.

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Though numerous studies have analysed the feeding periodicity of North Sea gadoids, no general diel pattern has been found. The lack of agreement between studies may be related to differences in prey composition and behaviour, but it has not been attempted to link the diel intake pattern directly to intake of individual prey. This study presents an analysis of the round the clock occurrence of several prey types in the stomachs of whiting Merlangius merlangus, a major predator on fish and crustaceans in the North Sea. Generalised linear models were used to determine if the occurrence of different prey varied significantly with time of day and whether this diel pattern differed between locations and predator size groups. The results show that the occurrence of bottom dwelling prey increased significantly during the night at 4 of 5 locations. In contrast, free swimming prey and prey migrating towards the demersal layer during the day were eaten mainly in the daylight hours. No diel pattern in the presence of larger fish prey could be found, presumably due to their longer digestion time. A general diel pattern in catch rates of the predator could not be detected and the analyses did not appear to be biased by vertical migration of the predator. The results have important implications for the understanding of prey selection by wild predators, as this is, in effect, a choice between temporally co-occurring prey.

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Krill behaviour as recorded by acoustic doppler current profilers in the Gullmarsfjord

Cited by 29 publications

References 31 publications

Food utilization of two pelagic crustaceans in the Greenland Sea: Meganyctiphanes norvegica (Euphausiacea) and Hymenodora glacialis (Decapoda, Caridea)

Food utilization of two pelagic crustaceans in the Greenland Sea: Meganyctiphanes norvegica (Euphausiacea) and Hymenodora glacialis (Decapoda, Caridea)

Toward a more comprehensive theory of zooplankton diel vertical migration: Integrating ultraviolet radiation and water transparency into the biotic paradigm

Diel feeding pattern of whiting in the North Sea

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