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Ye H, Zhao L, Ren X, Cai Y, Chi H. "Switch-Off-On" Detection of Fe 3+ and F - Ions Based on Fluorescence Silicon Nanoparticles and Their Application to Food Samples. NANOMATERIALS 2022; 12:nano12020213. [PMID: 35055232 PMCID: PMC8779261 DOI: 10.3390/nano12020213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/27/2021] [Accepted: 01/07/2022] [Indexed: 02/05/2023]
Abstract
An approach to the detection of F− ions in food samples was developed based on a “switch-off-on” fluorescence probe of silicon nanoparticles (SiNPs). The fluorescence of the synthetic SiNPs was gradually quenched in the presence of Fe3+ ion and slightly recovered with the addition of F− ion owing to the formation of a stable and colorless ferric fluoride. The fluorescence recovery exhibited a good linear relationship (R2 = 0.9992) as the concentration of F− ion increased from 0 to 100 μmol·L−1. The detection limit of the established method of F− ion was 0.05 μmol·L−1. The recovery experiments confirmed the accuracy and reliability of the proposed method. The ultraviolet–visible spectra, fluorescence decays, and zeta potentials evidenced the fluorescence quenching mechanism involving the electron transfer between the SiNPs and Fe3+ ion, while the fluorescence recovery resulted from the formation of ferric fluoride. Finally, SiNPs were successfully applied to detect F− ions in tap water, Antarctic krill, and Antarctic krill powder.
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Reproductive traits of common Euphausids in the south of Antarctic Polar Front. YING YONG SHENG TAI XUE BAO = THE JOURNAL OF APPLIED ECOLOGY 2021; 32:4156-4164. [PMID: 34898132 DOI: 10.13287/j.1001-9332.202111.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Euphausiids (krill) is a basic component of the Southern Ocean ecosystem, with a key role in the Antarctic marine food web. Krill may be the largest unexploited animal protein source for human beings. There is a great deal of interest in exploiting krill resources. Our understanding is poor about the biology of those species, particularly the reproductive traits of krill species, expect for Euphausia superba. Here, we reviewed related studies and revealed that different species of krill undergo similar physiological steps during ovary development. There are regional variations in the size of krill oocytes. The sexual maturity stages of female krill could be classified by observing the thelycum and ovarian morphology. There are latitudinal variations in spawning periods among species and regional variations within species. Most observations showed that krill samples are dominated by females. Future research should be conducted, i.e., (1) strengthening the study on the reproductive traits of krill, besides Euphausia superba, and further to explore the effects of seasonal and regional reproductive traits on the distribution of krill around Antarctica, (2) focusing on experimental biology in order to clarify the mechanism of spawning times of krill and further to calculate accurately the fecundity to evaluate the impacts of exploiting krill resource.
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Wang Y, Ma L, He J, Liu Z, Weng S, Wang L, He J, Guo C. Whole genome sequencing and comparative genomic analyses of Planococcus alpniumensis MSAK28401 T, a new species isolated from Antarctic krill. BMC Microbiol 2021; 21:288. [PMID: 34686131 PMCID: PMC8532331 DOI: 10.1186/s12866-021-02347-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 10/06/2021] [Indexed: 11/12/2022] Open
Abstract
Background Extremophiles have attracted much attention in the last few decades, as they possess different properties by producing certain useful metabolites. However, the secondary metabolism of the extremophiles of Antarctic krill has received little attention. Results In this study, a new bacterial strain MSAK28401T from Antarctic krill was isolated and identified. The results of analysis on phenotypic, chemotaxonomic, and genomic characteristics showed that the strain MSAK28401T belongs to the genus Planococcus. Cells of this strain were coccoid (0.89–1.05 μm) and aerobic. The majority of the fatty acid content was C15:0 anteiso (37.67 ± 0.90%) followed by C16:1 ω7c alcohol (10.37 ± 1.22%) and C16:0 iso (9.36 ± 0.71%). The calculated average nucleotide identity and DNA–DNA hybridization values between the strain MSAK28401T and type strains P. citreus DSM 20549T and P. rifietoensis M8T were lower than 91 and 70%, respectively. The strain MSAK28401T (=KCTC 43283T and MCCC 1k05448T) represented a new member of the genus Planococcus and was named P. alpniumensis sp. nov. Moreover, genes involved in the degradation of aromatic compounds (e.g., salicylate, gentisate, and quinate) were found in the genome, implying that strain MSAK28401T has an aromatic compound as its potential metabolite. This work will help us understand the genomic characteristics and potential metabolic pathway of Planococcus from Antarctic krill. Conclusions This study reported the genomic information and phenotypic characteristics of the new strain P. alpniumensis MSAK28401T isolated from Antarctic krill, and provided the genome information of Planococcus strains for further studying the function roles in aromatic compound metabolism. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-021-02347-3.
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Zeb L, Teng X, Shafiq M, Wang S, Xiu Z, Su Z. Three-liquid-phase salting-out extraction of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)-rich oils from Euphausia superba. Eng Life Sci 2021; 21:666-682. [PMID: 34690637 PMCID: PMC8518559 DOI: 10.1002/elsc.202000098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/20/2021] [Accepted: 07/14/2021] [Indexed: 11/06/2022] Open
Abstract
The TLPSOES parameters were optimized by response surface methodology using Box-Behnken design, which were 16.5% w/w of ammonium citrate, 17.5% w/w of ethanol, and 46% w/w of n-hexane at 70 min of stirring time. Under optimized conditions the extraction efficiency attained was 90.91 ± 0.97% of EPA, 90.02 ± 1.04% of DHA, and 91.85 ± 1.11% of KO in the top n-hexane phase. The highest extraction efficiency of proteins and flavonoids, i.e. 88.34 ± 1.35% and 79.67 ± 1.13%, was recorded in the solid interface and ethanol phase, respectively. The KO extracted by TLPSOES system consisted of lowest fluoride level compared to the conventional method and whole wet krill biomass. The TLPSOES is a potential candidate for nutraceutical industry of KO extraction from wet krill biomass.
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Prado-Cabrero A, Nolan JM. Omega-3 nutraceuticals, climate change and threats to the environment: The cases of Antarctic krill and Calanus finmarchicus. AMBIO 2021; 50:1184-1199. [PMID: 33502683 PMCID: PMC8068752 DOI: 10.1007/s13280-020-01472-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 11/20/2020] [Accepted: 12/09/2020] [Indexed: 06/12/2023]
Abstract
The nutraceutical market for EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) is promoting fishing for Euphasia superba (Antarctic krill) in the Southern Ocean and Calanus finmarchicus in Norwegian waters. This industry argues that these species are underexploited, but they are essential in their ecosystems, and climate change is altering their geographical distribution. In this perspective, we advocate the cessation of fishing for these species to produce nutraceuticals with EPA and DHA. We argue that this is possible because, contrary to what this industry promotes, the benefits of these fatty acids only seem significant to specific population groups, and not for the general population. Next, we explain that this is desirable because there is evidence that these fisheries may interact with the impact of climate change. Greener sources of EPA and DHA are already available on the market, and their reasonable use would ease pressure on the Arctic and Antarctic ecosystems.
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Michael K, Suberg LA, Wessels W, Kawaguchi S, Meyer B. Facing Southern Ocean warming: Temperature effects on whole animal performance of Antarctic krill (Euphausia superba). ZOOLOGY 2021; 146:125910. [PMID: 33735797 DOI: 10.1016/j.zool.2021.125910] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 02/19/2021] [Accepted: 02/23/2021] [Indexed: 10/22/2022]
Abstract
The ongoing environmental changes in the Southern Ocean may cause a dramatic decrease in habitat quality. Due to its central position in the food web, Antarctic krill (Euphausia superba) is a key species of the marine Antarctic ecosystem. It is therefore crucial to understand how increasing water temperatures affect important krill life-cycle processes. Here, a long-term (August - March) laboratory acclimation experiment at different temperature scenarios (0.5 °C, 1.5 °C, 2.5 °C, 3.5 °C, 5 °C, 7 °C) was performed and the effects of elevated temperatures on whole animal parameters (O2 consumption, body length, length of the digestive gland) were analyzed. The response of krill oxygen consumption to different experimental temperatures differed between acute/short-term and long-term acclimation. After 8 months, krill oxygen consumption remained unchanged up to temperatures of 3.5 °C and was significantly higher at temperatures > 3.5 °C. Krill acclimated to temperatures ≥ 3.5 °C were significantly smaller at the end of the experiment. Limited food intake and/or conversion may have contributed to this effect, especially pronounced after the onset of the reproductive period. In addition, the seasonal growth pattern in males differed from that of females. Together, our findings indicate that warming Southern Ocean waters are likely to increase metabolic rate in krill, possibly altering the amount of energy available for other important life-cycle processes, a finding directly related to future population dynamics and fisheries management.
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Bergami E, Manno C, Cappello S, Vannuccini ML, Corsi I. Nanoplastics affect moulting and faecal pellet sinking in Antarctic krill (Euphausia superba) juveniles. ENVIRONMENT INTERNATIONAL 2020; 143:105999. [PMID: 32763632 DOI: 10.1016/j.envint.2020.105999] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 07/17/2020] [Accepted: 07/17/2020] [Indexed: 06/11/2023]
Abstract
Plastic debris has been identified as a potential threat to Antarctic marine ecosystems, however, the impact of nanoplastics (<1 μm) is currently unexplored. Antarctic krill (Euphausia superba) is a keystone species of Southern Ocean pelagic ecosystems, which plays a central role in the Antarctic food webs and carbon (C) cycle. Krill has been shown to rapidly fragment microplastic beads through the digestive system, releasing nanoplastics with unknown toxicological effects. Here we exposed krill juveniles to carboxylic (COOH, anionic) and amino- (NH2, cationic) polystyrene nanoparticles (PS NPs) and we investigated lethal and sub-lethal endpoints after 48 h. The analysis of PS NP suspensions in Antarctic sea water (SW) media showed that PS-COOH formed large agglomerates (1043 ± 121 nm), while PS-NH2 kept their nominal size (56.8 ± 3 nm) during the exposure time. After 48 h, no mortality was found but increase in exuviae production (12.6 ± 1.3%) and reduced swimming activity were observed in juveniles exposed to PS-NH2. The microbial community composition in SW supports the release of krill moults upon PS NP exposure and stimulates further research on the pivotal role of krill in shaping Southern Ocean bacterial assemblages. The presence of fluorescent signal in krill faecal pellets (FPs) confirmed the waterborne ingestion and egestion of PS-COOH at 48 h of exposure. Changes in FP structure and properties were also associated to the incorporation of PS NPs regardless of their surface charge. The effects of PS NPs on krill FP properties were compared to Control 0 h as a reference for full FPs (plastic vs food) and Control 48 h as a reference for more empty-like FPs (plastic vs lack of food). Exposure to PS NPs led to a FP sinking rate comparable to Control 48 h, but significantly lower than Control 0 h (58.40 ± 23.60 m/d and 51.23 ± 28.60 m/d for PS-COOH and PS-NH2; 168.80 ± 74.58 m/d for Control 0 h). Considering the important role played by krill in the food web and C export in the Southern Ocean, the present study provides cues about the potential impact of nanoplastics on Antarctic pelagic ecosystems and their biogeochemical cycles.
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Insight into Physicochemical, Rheological, and Antibacterial Properties of Chitosan Extracted from Antarctic krill: A Comparative Study. Molecules 2020; 25:molecules25184074. [PMID: 32906578 PMCID: PMC7571028 DOI: 10.3390/molecules25184074] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 08/16/2020] [Accepted: 08/21/2020] [Indexed: 11/17/2022] Open
Abstract
In this work, physicochemical, rheological, and antibacterial properties of chitosan (CS) extracted from white shrimp (WS), giant river prawn (GP), and Antarctic krill (AK) were investigated. The results demonstrated that molecular weight (MW) of commercial chitosan (CCS), WSCS, GPCS, and AKCS were 1175.8, 2130.4, 1293.3, and 1109.3 kDa with the degree of deacetylation (DDA) of 73.5, 74.1, 82.1, and 75.9%, respectively. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) were employed to study the structural differences of CS. Moreover, storage modulus (G′) and loss modulus (G″) of AKCS were lower than that of WSCS and GPCS, respectively, but higher than that of CCS. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) of CS against Escherichia coli and Staphylococcus aureus were investigated at concentration between 0.0125 and 1 mg/mL. These results highlighted that AKCS with low viscoelastic properties had a potential application in food and pharmaceutical application.
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Liu H, Zhu GP. [Spatial-temporal variation in hotspot and coldspot of Antarctic krill distribution in recent 100 years]. YING YONG SHENG TAI XUE BAO = THE JOURNAL OF APPLIED ECOLOGY 2020; 31:1015-1022. [PMID: 32537999 DOI: 10.13287/j.1001-9332.202003.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
To analyze the long-term variation in the spatial-temporal patterns of Antarctic krill (Euphausia superba) distribution, based on krill density data collected from 1926 to 2016, we analyzed the spatial and temporal variation of krill using the Getis-Ord Gi* statistic and the Triangulated Irregular Network (TIN) model. We compared the krill abundance, the percentage of krill abundance, and the size of hotspot/coldspot area. The results showed that there were one core hot-spot area, one sub-hotspot area and one edge hotspot area from 1926 to 1935 and from 1936 to 1945; one core hotspot area, one sub-hotspot area and one edge hotspot/coldspot area from 1976 to 1985; two core hotspot areas, two sub-hotspot areas, two edge hotspot areas, one sub-coldspot area and one coldspot area from 1986 to 1995; two core hotspot areas, two sub-hotspot/sub-coldspot areas and two edge hotspot/coldspot areas from 1996 to 2005; and from 2006 to 2016, there were two sub-hotspot areas, two edge hotspot areas, one sub-coldspot area and one edge coldspot area, respectively. Those hotspots/coldspots mostly occurred in the South Sandwich Islands, the Antarctic Peninsula, and the west of the Prydz Bay. From 1926 to 2016, krill abundance, the percentage of krill abundance in the hotspot area and the size of hotspot area had generally reduced, but the percentage of krill abundance in coldspot area and the size of coldspot area were increasing, while krill abundance in coldspot area decreased. It is a feasible approach to build an irregular triangle network to measure the size of hotspot/coldspot area and utilize hotspot analysis with 95% confidence to analyze the spatial-temporal pattern of krill distribution.
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Liu B, Pan S. Effect of chitosan coatings incorporated sodium phytate on the shelf-life of Antarctic krill (Euphausia superba). Int J Biol Macromol 2020; 151:62-65. [PMID: 32068063 DOI: 10.1016/j.ijbiomac.2020.02.148] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 02/07/2020] [Accepted: 02/14/2020] [Indexed: 11/19/2022]
Abstract
Chitosan is a preservative with potent antibacterial activity, and sodium phytate has antioxidant activity and potent ion chelating ability. The present work aimed to explore the effects of chitosan coating combined with sodium phytate (0.1% sodium phytate + 1% chitosan) on preserving Antarctic krill (Euphausia superba) during partially frozen storage. Treatment of chitosan coating combined with sodium phytate significantly suppressed microbial growth, the increases in pH value, total volatile basic nitrogen and sensory deterioration of Antarctic krill (E. superba) during partially frozen storage. Therefore, chitosan coating combined with sodium phytate may be a practical method to suppress quality deterioration of Antarctic krill and thus extend its shelf life.
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Gao R, Chen L, Zhang W, Zhang S, Rao J, Hu J. Effect of dietary Antarctic krill Euphausia superba on the growth performance and nonspecific immunity of red swamp crayfish Procambarus clarkia. FISH & SHELLFISH IMMUNOLOGY 2020; 96:122-125. [PMID: 31805411 DOI: 10.1016/j.fsi.2019.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/28/2019] [Accepted: 12/01/2019] [Indexed: 06/10/2023]
Abstract
This study aims to investigate the effects of replacing different proportions of fishmeal with Antarctic krill (AK) on the growth performance, body composition and nonspecific immunity index of red swamp crayfish Procambarus clarkia. AK was used to replace 0 (control), 25%, 50% and 100% of the fishmeal in the basic diet of crayfish to formulate four test feeds with basically equivalent nitrogen and lipid contents; these feeds were denoted AK0, AK25, AK50 and AK100, respectively. Compared with the control group, crayfish fed diets with AK replacement showed increased body weight gain; feed efficiency; survival rate; body protein content; phenoloxidase, superoxide dismutase and glutathione peroxidase activities; total haemocyte counts; number of hyaline, semigranular and granular cells; and disease resistance against Aeromonas hydrophila. Conversely, the body lipid level of these crayfish decreased relative to that of the control. However, a high AK level (AK100) does not show improvements in efficiency compared with a moderate AK level (AK50). Based on the efficiency of AK in enhancing the growth performance and nonspecific immunity of crayfish, the optimum replacement proportion of fishmeal with AK was 50%. These results confirm that AK can promote the growth of crayfish and improve their disease resistance.
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Mödinger Y, Schön C, Wilhelm M, Hals PA. Plasma Kinetics of Choline and Choline Metabolites After A Single Dose of Superba BoostTM Krill Oil or Choline Bitartrate in Healthy Volunteers. Nutrients 2019; 11:nu11102548. [PMID: 31652561 PMCID: PMC6835836 DOI: 10.3390/nu11102548] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 10/16/2019] [Accepted: 10/18/2019] [Indexed: 12/23/2022] Open
Abstract
As an essential nutrient, the organic water-soluble compound choline is important for human health. Choline is required for numerous biological processes, including the synthesis of neurotransmitters, and it is an important prerequisite for structural integrity and the functioning of cells. A choline-rich diet provides crucial choline sources, yet additional choline dietary supplements might be needed to fully meet the body’s requirements. Dependent on the structure of choline in different sources, absorption and metabolism may differ and strongly impact the bioavailability of circulating choline. This study in healthy volunteers aimed to compare the pharmacokinetics of free choline and of selected choline metabolites between the single dose intake of phosphatidylcholine, present in SuperbaBoostTM krill oil, and choline bitartrate salt. Results demonstrate that albeit free choline levels in plasma were comparable between both choline sources, peak choline concentration was reached significantly later upon intake of SuperbaBoostTM. Moreover, the occurrence of choline metabolites differed between the study products. Levels of the biologically important metabolites betaine and dimethylglycine (DMG) were higher, while levels of trimethylamine N-oxide (TMAO) were substantially lower upon intake of SuperbaBoostTM compared to choline bitartrate.
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Zerbini AN, Adams G, Best J, Clapham PJ, Jackson JA, Punt AE. Assessing the recovery of an Antarctic predator from historical exploitation. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190368. [PMID: 31824687 PMCID: PMC6837233 DOI: 10.1098/rsos.190368] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 09/23/2019] [Indexed: 06/01/2023]
Abstract
The recovery of whale populations from centuries of exploitation will have important management and ecological implications due to greater exposure to anthropogenic activities and increasing prey consumption. Here, a Bayesian population model integrates catch data, estimates of abundance, and information on genetics and biology to assess the recovery of western South Atlantic (WSA) humpback whales (Megaptera novaeangliae). Modelling scenarios evaluated the sensitivity of model outputs resulting from the use of different data, different model assumptions and uncertainty in catch allocation and in accounting for whales killed but not landed. A long period of exploitation drove WSA humpback whales to the brink of extinction. They declined from nearly 27 000 (95% PI = 22 800-33 000) individuals in 1830 to only 450 (95% PI = 200-1400) whales in the mid-1950s. Protection led to a strong recovery and the current population is estimated to be at 93% (95% PI = 73-100%) of its pre-exploitation size. The recovery of WSA humpback whales may result in large removals of their primary prey, the Antarctic krill (Euphausia superba), and has the potential to modify the community structure in their feeding grounds. Continued monitoring is needed to understand how these whales will respond to modern threats and to climate-driven changes to their habitats.
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Havermans C, Auel H, Hagen W, Held C, Ensor NS, A Tarling G. Predatory zooplankton on the move: Themisto amphipods in high-latitude marine pelagic food webs. ADVANCES IN MARINE BIOLOGY 2019; 82:51-92. [PMID: 31229150 DOI: 10.1016/bs.amb.2019.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Hyperiid amphipods are predatory pelagic crustaceans that are particularly prevalent in high-latitude oceans. Many species are likely to have co-evolved with soft-bodied zooplankton groups such as salps and medusae, using them as substrate, for food, shelter or reproduction. Compared to other pelagic groups, such as fish, euphausiids and soft-bodied zooplankton, hyperiid amphipods are poorly studied especially in terms of their distribution and ecology. Hyperiids of the genus Themisto, comprising seven distinct species, are key players in temperate and cold-water pelagic ecosystems where they reach enormous levels of biomass. In these areas, they are important components of marine food webs, and they are major prey for many commercially important fish and squid stocks. In northern parts of the Southern Ocean, Themisto are so prevalent that they are considered to take on the role that Antarctic krill play further south. Nevertheless, although they are around the same size as krill, and may also occur in swarms, their feeding behaviour and mode of reproduction are completely different, hence their respective impacts on ecosystem structure differ. Themisto are major predators of meso- and macrozooplankton in several major oceanic regions covering shelves to open ocean from the polar regions to the subtropics. Based on a combination of published and unpublished occurrence data, we plot out the distributions of the seven species of Themisto. Further, we consider the different predators that rely on Themisto for a large fraction of their diet, demonstrating their major importance for higher trophic levels such as fish, seabirds and mammals. For instance, T. gaudichaudii in the Southern Ocean comprises a major part of the diets of around 80 different species of squid, fish, seabirds and marine mammals, while T. libellula in the Bering Sea and Greenland waters is a main prey item for commercially exploited fish species. We also consider the ongoing and predicted range expansions of Themisto species in light of environmental changes. In northern high latitudes, sub-Arctic Themisto species are replacing truly Arctic, ice-bound, species. In the Southern Ocean, a range expansion of T. gaudichaudii is expected as water masses warm, impacting higher trophic levels and biogeochemical cycles. We identify the many knowlegde gaps that must be filled in order to evaluate, monitor and predict the ecological shifts that will result from the changing patterns of distribution and abundance of this important pelagic group.
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Clarke LJ, Suter L, King R, Bissett A, Deagle BE. Antarctic Krill Are Reservoirs for Distinct Southern Ocean Microbial Communities. Front Microbiol 2019; 9:3226. [PMID: 30697197 PMCID: PMC6340936 DOI: 10.3389/fmicb.2018.03226] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 12/11/2018] [Indexed: 11/13/2022] Open
Abstract
Host-associated bacterial communities have received limited attention in polar habitats, but are likely to represent distinct nutrient-rich niches compared to the surrounding environment. Antarctic krill (Euphausia superba) are a super-abundant species with a circumpolar distribution, and the krill microbiome may make a substantial contribution to marine bacterial diversity in the Southern Ocean. We used high-throughput sequencing of the bacterial 16S ribosomal RNA gene to characterize bacterial diversity in seawater and krill tissue samples from four locations south of the Kerguelen Plateau, one of the most productive regions in the Indian Sector of the Southern Ocean. Krill-associated bacterial communities were distinct from those of the surrounding seawater, with different communities inhabiting the moults, digestive tract and faecal pellets, including several phyla not detected in the surrounding seawater. Digestive tissues from many individuals contained a potential gut symbiont (order: Mycoplasmoidales) shown to improve survival on a low quality diet in other crustaceans. Antarctic krill swarms thus influence Southern Ocean microbial communities not only through top-down grazing of eukaryotic cells and release of nutrients into the water column, but also by transporting distinct microbial assemblages horizontally via migration and vertically via sinking faecal pellets and moulted exuviae. Changes to Antarctic krill demographics or distribution through fishing pressure or climate-induced range shifts will also influence the composition and dispersal of Southern Ocean microbial communities.
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Liu Y, Cong P, Li B, Song Y, Liu Y, Xu J, Xue C. Effect of thermal processing towards lipid oxidation and non-enzymatic browning reactions of Antarctic krill (Euphausia superba) meal. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2018; 98:5257-5268. [PMID: 29652437 DOI: 10.1002/jsfa.9064] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 03/13/2018] [Accepted: 04/01/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Antarctic krill is a huge source of biomass and prospective high-quality lipid source. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), nutritionally important lipid components with poor oxidative stability, were used as markers of oxidation during thermal processing of Antarctic krill (Euphausia superba) meal by evaluating the lipolysis, lipid oxidation, and non-enzymatic browning reactions. RESULT Liquid chromatography-mass spectrometry of the phospholipids and the main oxidation products of free fatty acids and phosphatidylcholine (PC) was effective for evaluating the oxidation of EPA and DHA. During boiling, oxidation of EPA and DHA in the free fatty acid and PC fractions and hydrolysis of the fatty acids at the sn-2 position of the phospholipids were predominant. The changes in PC during drying were mainly attributed to the oxidation of EPA and DHA. Heat treatment increased the oxidation products and concentration of hydrophobic pyrrole owing to pyrrolization between phosphatidylethanolamine and the lipid oxidation products. CONCLUSION The lipid oxidation level of Antarctic krill increased after drying, owing to prolonged heating under the severe conditions. © 2018 Society of Chemical Industry.
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Qi X, Liao E, Zhao K, Regenstein JM, Mao X. Multi-stage countercurrent process for extracting protein from Antarctic Krill ( Euphausia superba). JOURNAL OF FOOD SCIENCE AND TECHNOLOGY 2018; 55:4450-4457. [PMID: 30333641 PMCID: PMC6170336 DOI: 10.1007/s13197-018-3368-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 09/18/2017] [Accepted: 07/30/2018] [Indexed: 10/28/2022]
Abstract
To systematically study multi-stage countercurrent process for Antarctic krill protein extracting and to optimize the multi-stage countercurrent technology, the solubility of Antarctic krill proteins after multi-step dissolution was explored firstly; multi-step extraction was investigated; and then multi-stage countercurrent system for protein extraction was carried out. In single step extraction, krill-to-water ratio and pH were chosen as 1:10 and 12.5 respectively, in order to extract more protein. In the multi-step dissolution process, the protein solubility of aqueous solution at pH 12.5 was 33.0 ± 0.8 mg/mL. Multi-step cross-flow processing testified the feasibility of multi-stage countercurrent assumption. Three-stage countercurrent method using krill-to-water ratio 1:10 extracted, 95.1 ± 0.6% protein from krill, where almost the same water as previous works. The total recovery yield of 67.9 ± 1.6% was achieved after precipitation at pH 4.5.
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Bjørndal B, Bruheim I, Lysne V, Ramsvik MS, Ueland PM, Nordrehaug JE, Nygård OK, Berge RK. Plasma choline, homocysteine and vitamin status in healthy adults supplemented with krill oil: a pilot study. Scandinavian Journal of Clinical and Laboratory Investigation 2018; 78:527-532. [PMID: 30261756 DOI: 10.1080/00365513.2018.1512716] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Plasma concentrations of metabolites along the choline oxidation and tryptophan degradation pathways have been linked to lifestyle diseases and dietary habits. This study aimed to investigate how krill oil, a source of ω-3 polyunsaturated fatty acids (PUFAs) with a high phosphatidylcholine content, affected these parameters. The pilot study was conducted as a 28 days intervention in 17 healthy volunteers (18-36 years), who received a supplement of 4.5 g krill oil per day, providing 833 mg ω-3 PUFAs, and 1750 mg phosphatidylcholine. Krill oil supplementation increased fasting plasma choline (+28.4%, p < .001), betaine (+26.6%, p < .001), dimethylglycine (+33.7%, p < .001) and sarcosine (+16.8%, p < .001), whereas no statistically significant changes were seen for plasma glycine, serine, methionine, total homocysteine, cysteine, cystathionine, methionine sulfoxide, folate, cobalamin, B2-, B3-, and B6 vitamers, tryptophan, kynurenines, nicotinamide, vitamin A and vitamin E. In summary, krill oil supplementation influenced choline metabolite levels, but not plasma metabolites of the tryptophan-kynurenine-nicotinamide pathways and vitamins. These observations should be confirmed in a placebo-controlled trial, including an ω-3 PUFA supplement without phospholipids to explore the potential additive effects of the different active ingredients.
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Weinstein BG, Irvine L, Friedlaender AS. Capturing foraging and resting behavior using nested multivariate Markov models in an air-breathing marine vertebrate. MOVEMENT ECOLOGY 2018; 6:16. [PMID: 30250739 PMCID: PMC6146519 DOI: 10.1186/s40462-018-0134-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/16/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Matching animal movement with the behaviors that shape life history requires a rigorous connection between the observed patterns of space use and inferred behavioral states. As animal-borne dataloggers capture a greater diversity and frequency of three dimensional movements, we can increase the complexity of movement models describing animal behavior. One challenge in combining data streams is the different spatial and temporal frequency of observations. Nested movement models provide a flexible framework for gleaning data from long-duration, but temporally sparse, data sources. RESULTS Using a two-layer nested model, we combined geographic and vertical movement to infer traveling, foraging and resting behaviors of Humpback whales off the West Antarctic Peninsula. This approach refined previous work using only geographic data to delineate coarser behavioral states. Our results showed increased intensity in foraging activity in late season animals as the whales prepared to migrate north to tropical calving grounds. Our model also suggests strong diel variation in movement states, likely linked to daily changes in prey distribution. CONCLUSIONS Using a combination of two-dimensional and three-dimensional movement data, we highlight the connection between whale movement and krill availability, as well as the complex spatial pattern of whale foraging in productive polar waters.
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Chen LF, Zhu GP. [Analysis of influence on spatial distribution of fishing ground for Antarctic krill fishery in the northern South Shetland Islands based on GWR model]. YING YONG SHENG TAI XUE BAO = THE JOURNAL OF APPLIED ECOLOGY 2018; 29:938-944. [PMID: 29722238 DOI: 10.13287/j.1001-9332.201803.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Based on Antarctic krill fishery and marine environmental data collected by scientific observers, using geographically weighted regression (GWR) model, we analyzed the effects of the factors with spatial attributes, i.e., depth of krill swarm (DKS) and distance from fishing position to shore (DTS), and sea surface temperature (SST), on the spatial distribution of fishing ground in the northern South Shetland Islands. The results showed that there was no significant aggregation in spatial distribution of catch per unit fishing effort (CPUE). Spatial autocorrelations (positive) among three factors were observed in 2010 and 2013, but were not in 2012 and 2016. Results from GWR model showed that the extent for the impacts on spatial distribution of CPUEs varied among those three factors, following the order DKS>SST>DTS. Compared to the DKS and DTS, the impact of SST on the spatial distribution of CPUEs presented adverse trend in the eastern and western parts of the South Shetland Islands. Negative correlations occurred for the spatial effects of DKS and DTS on distribution of CPUEs, though with inter-annual and regional variation. Our results provide metho-dological reference for researches on the underlying mechanism for fishing ground formation for Antarctic krill fishery.
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Tarroux A, Lydersen C, Trathan PN, Kovacs KM. Temporal variation in trophic relationships among three congeneric penguin species breeding in sympatry. Ecol Evol 2018; 8:3660-3674. [PMID: 29686847 PMCID: PMC5901183 DOI: 10.1002/ece3.3937] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 01/12/2018] [Accepted: 01/27/2018] [Indexed: 11/08/2022] Open
Abstract
Penguins are a monophyletic group in which many species are found breeding sympatrically, raising questions regarding how these species coexist successfully. Here, the isotopic niche of three sympatric pygoscelid penguin species was investigated at Powell Island, South Orkney Islands, during two breeding seasons (austral summers 2013–2014 and 2015–2016). Measurements of carbon (δ13C) and nitrogen (δ15N) stable isotope ratios were obtained from blood (adults) or feather (chicks) samples collected from Adélie Pygoscelis adeliae, chinstrap P. antarctica, and gentoo P. papua penguins. Isotopic niche regions (a proxy for the realized trophic niches) were computed to provide estimates of the trophic niche width of the studied species during the breeding season. The isotopic niche regions of adults of all three species were similar, but gentoo chicks had noticeably wider isotopic niches than the chicks of the other two species. Moderate to strong overlap in isotopic niche among species was found during each breeding season and for both age groups, suggesting that the potential for competition for shared food sources was similar during the two study years, although the actual level of competition could not be determined owing to the lack of data on resource abundance. Clear interannual shifts in isotopic niche were seen in all three species, though of lower amplitude for adult chinstrap penguins. These shifts were due to variation in carbon, but not nitrogen, isotopic ratios, which could indicate either a change in isotopic signature of their prey or a switch to an alternative food web. The main conclusions of this study are that (1) there is a partial overlap in the isotopic niches of these three congeneric species and that (2) they responded similarly to changes that likely occurred at the base of their food chain between the 2 years of the study.
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Corsolini S, Ademollo N, Martellini T, Randazzo D, Vacchi M, Cincinelli A. Legacy persistent organic pollutants including PBDEs in the trophic web of the Ross Sea (Antarctica). CHEMOSPHERE 2017; 185:699-708. [PMID: 28732330 DOI: 10.1016/j.chemosphere.2017.07.054] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 06/29/2017] [Accepted: 07/11/2017] [Indexed: 05/22/2023]
Abstract
The ecological features of the Ross Sea trophic web are peculiar and different from other polar food webs, with respect to the use of habitat and species interactions; due to its ecosystem integrity, it is the world's largest Marine Protected Area, established in 2016. Polar organisms are reported to bioaccumulate lipophilic contaminant, viz persistent organic pollutants (POPs). Legacy POPs and flame retardants (polybrominated diphenyl ethers, PBDEs) were studied in key species of the Ross Sea (Euphausia superba, Pleuragramma antarctica) and their predators (Dissostichus mawsoni, Pygoscelis adeliae, Aptenodytes forsteri, Catharacta maccormicki, Leptonychotes weddellii). Gaschromatography revealed the presence of PCBs, HCB, DDTs, PBDEs in most of the samples; HCHs, dieldrin, Eldrin, non-ortho PCBs, PCDDs, PCDFs were detected only in some species. The average ∑PBDEs was 0.19-1.35 pg/g wet wt in the key-species and one-two order of magnitude higher in the predators. Penguins and skuas from an area where a long-term field camp is located showed higher BDE concentrations. The ΣDDTs was higher in the Antarctic toothfish (20 ± 6.73 ng/g wet wt) and in the South Polar skua (5.911 ± 3.425 ng/g wet wt). The TEQs were evaluated and the highest concentration was found in the Weddell seal, due to PCB169, 1,2,3,4,7,8-HxCDF, and 2,3,4,6,7,8-HxCDF. There was no significant relationship between the trophic level and the POP concentrations. Although low concentrations, organisms of the Ross Sea trophic web should be further studied: lack of information on some ecotoxicological features and human impacts including global change may distress the ecosystem with unpredictable effects.
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A novel calcium-binding peptide from Antarctic krill protein hydrolysates and identification of binding sites of calcium-peptide complex. Food Chem 2017; 243:389-395. [PMID: 29146354 DOI: 10.1016/j.foodchem.2017.09.152] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 09/27/2017] [Accepted: 09/29/2017] [Indexed: 11/22/2022]
Abstract
Trypsin was used for preparing peptides with high calcium-binding capacity from Antarctic krill. Hydroxyapatite chromatography (HAC), size-exclusion chromatography (SEC), and reversed phase high performance liquid chromatography (RP-HPLC) were used to capture and purify calcium-binding peptides. The peptide sequence was determined to be VLGYIQIR (N- to C-terminal, MW = 960.58 Da), using LTQ Orbitrap XL. According to the results of FTIR and mass spectrometry, chelating site of calcium ions may possibly involve the carbonal or amino groups of Gln, Ile and Arg residues. Molecular dynamic simulation showed the conformation of peptide was markedly varied, and the distance between calcium ion and Gln and Ile residues was changing all the time. However, the distance between calcium ion and carboxyl oxygen of arginine residues was not changed significantly from 2 ns to 100 ns. Identified peptide can be used as a novel calcium supplement.
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Dynamic foraging of a top predator in a seasonal polar marine environment. Oecologia 2017; 185:427-435. [PMID: 28914358 DOI: 10.1007/s00442-017-3949-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 08/30/2017] [Indexed: 02/05/2023]
Abstract
The seasonal movement of animals at broad spatial scales provides insight into life-history, ecology and conservation. By combining high-resolution satellite-tagged data with hierarchical Bayesian movement models, we can associate spatial patterns of movement with marine animal behavior. We used a multi-state mixture model to describe humpback whale traveling and area-restricted search states as they forage along the West Antarctic Peninsula. We estimated the change in the geography, composition and characteristics of these behavioral states through time. We show that whales later in the austral fall spent more time in movements associated with foraging, traveled at lower speeds between foraging areas, and shifted their distribution northward and inshore. Seasonal changes in movement are likely due to a combination of sea ice advance and regional shifts in the primary prey source. Our study is a step towards dynamic movement models in the marine environment at broad scales.
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The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring. Polar Biol 2017; 40:2001-2013. [PMID: 32009725 PMCID: PMC6961482 DOI: 10.1007/s00300-017-2118-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Revised: 03/24/2017] [Accepted: 03/26/2017] [Indexed: 11/23/2022]
Abstract
Antarctic krill (Euphausia superba) play a central role in the food web of the Southern Ocean, forming a link between primary production and large predators. Krill produce large, faecal pellets (FP) which can form a large component of mesopelagic particulate organic carbon (POC) fluxes. However, the patchy distribution of krill swarms, highly variable pellet composition, and variable sinking and attenuation rates means that these episodic, but potentially large, carbon fluxes are difficult to sample or model. We measured particle flux and type using Marine Snow Catchers (MSC) in the marginal ice zone near the South Orkneys, Antarctica. Krill FP were the dominant component of the POC flux in the upper 200 m (typically 60–85%). FP sinking velocities measured onboard were highly variable (15–507 m d−1) but overall high, with mean equivalent velocities of 172, 267, and 161 m d−1 at our three stations. The high numbers of krill FP sinking through the mesopelagic suggest that krill FP can be transferred efficiently and/or that rates of krill FP production are high. We compared our direct MSC-derived estimates of krill FP POC flux (33–154 mg C m−2 d−1) 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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