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  • 1
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-7-1)
    Abstract: Submesoscale structures, characterized by intense vertical and horizontal velocities, potentially play a crucial role in oceanographic dynamics and pelagic fluxes. Due to their small spatial scale and short temporal persistence, conditions for in situ measurements are challenging and thus the role of such structures for zooplankton distribution is still unclear. During RV Polarstern expedition PS107 to Arctic Fram Strait in July/August 2017, a submesoscale filament was detected, which initiated an ad hoc oceanographic and biological sampling campaign. To determine zooplankton taxonomic composition, horizontal and vertical distribution, abundance and biomass, vertical MultiNet hauls (depth intervals: 300–200–100–50–10–0 m) were taken at four stations across the filament. Zooplankton data were evaluated in context with the physical-oceanographic observations of the filament to assess submesoscale physical-biological interactions. Our data show that submesoscale features considerably impact zooplankton dynamics. While structuring the pelagial with distinct zooplankton communities in a vertical as well as horizontal dimension, they accumulate abundance and biomass of epipelagic species at the site of convergence. Further, high-velocity jets associated with such dynamics are possibly of major importance for species allocation and biological connectivity, accelerating for instance processes such as the ‘Atlantification’ of the Arctic. Thus, submesoscale features affect the surrounding ecosystem in multiple ways with consequences for higher trophic levels and biogeochemical cycles.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2757748-X
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  • 2
    Online Resource
    Online Resource
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-8-12)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-8-12)
    Abstract: The Arctic Ocean is rapidly changing. Air temperature is rising two to four times faster in the Arctic than the global average, with dramatic consequences for the ecosystems. Polar zooplankton species have to cope with those increasing temperatures, whilst simultaneously facing increasing competition by boreal-Atlantic sister species advected into the Arctic Ocean via a stronger Atlantic inflow. To assess the sensitivity of Arctic and Atlantic zooplankton to rising temperatures, respiration rates of dominant Arctic species ( Calanus hyperboreus , Calanus glacialis , Paraeuchaeta glacialis , Themisto libellula ) and their co-occurring Atlantic congeners ( Calanus finmarchicus , Paraeuchaeta norvegica , Themisto abyssorum ) were measured at ambient temperatures and simulated conditions of ocean warming from 0 to 10°C during three expeditions with RV Polarstern to the Arctic Fram Strait. Arctic zooplankton showed only slowly increasing respiration rates with increasing temperatures, also indicated by low Q 10 ratios. In contrast, boreal-Atlantic representatives responded to higher temperatures by a rapid and steeper increase in their respiration rates (higher Q 10 ), suggesting higher metabolic activity. These results imply that Arctic species are physiologically more tolerant to ocean warming than expected but might be outcompeted by their Atlantic congeners beyond a certain temperature threshold in areas of strong distribution overlap. Thus, the ‘Atlantification’ of the Arctic zooplankton community seems to be driven rather by ecological interactions than by physiological limitations. Changes in zooplankton community composition and biodiversity will have major consequences for trophodynamics and energy flux in Arctic ecosystems, since polar species tend to be larger than their southern counterparts and have a higher lipid content, providing more energy-rich food for higher trophic levels.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2757748-X
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  • 3
    Online Resource
    Online Resource
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 8 ( 2022-1-12)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2022-1-12)
    Abstract: The northern Humboldt Current upwelling system (HCS) belongs to the most productive marine ecosystems, providing five to eight times higher fisheries landings per unit area than other coastal upwelling systems. To solve this “Peruvian puzzle”, to elucidate the pelagic food-web structure and to better understand trophic interactions in the HCS, a combined stable isotope and fatty acid trophic biomarker approach was adopted for key zooplankton taxa and higher trophic positions with an extensive spatial coverage from 8.5 to 16°S and a vertical range down to 1,000 m depth. A pronounced regional shift by up to ∼5‰ in the δ 15 N baseline of the food web occurred from North to South. Besides regional shifts, δ 15 N ratios of particulate organic matter (POM) also tended to increase with depth, with differences of up to 3.8‰ between surface waters and the oxygen minimum zone. In consequence, suspension-feeding zooplankton permanently residing at depth had up to ∼6‰ higher δ 15 N signals than surface-living species or diel vertical migrants. The comprehensive data set covered over 20 zooplankton taxa and indicated that three crustacean species usually are key in the zooplankton community, i.e., the copepods Calanus chilensis at the surface and Eucalanus inermis in the pronounced OMZ and the krill Euphausia mucronata , resulting in an overall low number of major trophic pathways toward anchovies. In addition, the semi-pelagic squat lobster Pleuroncodes monodon appears to play a key role in the benthic-pelagic coupling, as indicated by highest δ 13 C’ ratios of −14.7‰. If feeding on benthic resources and by diel vertical migration, they provide a unique pathway for returning carbon and energy from the seafloor to the epipelagic layer, increasing the food supply for pelagic fish. Overall, these mechanisms result in a very efficient food chain, channeling energy toward higher trophic positions and partially explaining the “Peruvian puzzle” of enormous fish production in the HCS.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
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  • 4
    In: Global Ecology and Biogeography, Wiley, Vol. 29, No. 6 ( 2020-06), p. 1008-1019
    Abstract: Biodiversity dynamics comprise evolutionary and ecological changes on multiple temporal scales from millions of years to decades, but they are often interpreted within a single time frame. Planktonic foraminifera communities offer a unique opportunity for analysing the dynamics of marine biodiversity over different temporal scales. Our study aims to provide a baseline for assessments of biodiversity patterns over multiple time‐scales, which is urgently needed to interpret biodiversity responses to increasing anthropogenic pressure. Location Global (26 sites). Time period Five time‐scales: multi‐million‐year (0–7 Myr), million‐year (0–0.5 Myr), multi‐millennial (0–15 thousand years), millennial (0–1,100 years) and decadal (0–32 years). Major taxa studied Planktonic foraminifera. Methods We analysed community composition of planktonic foraminifera at five time‐scales, combining measures of standing diversity (richness and effective number of species, ENS) with measures of temporal community turnover (presence–absence‐based, dominance‐based). Observed biodiversity patterns were compared with the outcome of a neutral model to separate the effects of sampling resolution (the highest in the shortest time series) from biological responses. Results Richness and ENS decreased from multi‐million‐year to millennial time‐scales, but higher standing diversity was observed on the decadal scale. As predicted by the neutral model, turnover in species identity and dominance was strongest at the multi‐million‐year time‐scale and decreased towards the millennial scale. However, contrary to the model predictions, modern time series show rapid decadal variation in the dominance structure of foraminifera communities, which is of comparable magnitude as over much longer time periods. Community turnover was significantly correlated with global temperature change, but not on the shortest time‐scale. Main conclusions Biodiversity patterns can be to some degree predicted from the scaling effects related to different durations of time series, but changes in the dominance structure observed over the last few decades reach higher magnitude, probably forced by anthropogenic effects, than those observed over much longer durations.
    Type of Medium: Online Resource
    ISSN: 1466-822X , 1466-8238
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 1479787-2
    detail.hit.zdb_id: 2021283-5
    SSG: 12
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  • 5
    In: Progress in Oceanography, Elsevier BV, Vol. 193 ( 2021-04), p. 102551-
    Type of Medium: Online Resource
    ISSN: 0079-6611
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 1497436-8
    detail.hit.zdb_id: 4062-9
    SSG: 21,3
    SSG: 14
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  • 6
    In: Journal of Plankton Research, Oxford University Press (OUP), Vol. 45, No. 1 ( 2023-02-01), p. 110-128
    Abstract: Small copepod genera play an important role in marine food webs and biogeochemical fluxes but have been neglected in many studies. This is the first study determining biomass, carbon consumption and egestion rates of small- ( & lt;1 mm prosome length, PL), medium- (1–1.5 mm PL) and large-sized ( & gt;2 mm PL) copepods along a cross-shelf transect in the southern Benguela upwelling system. Calanoids contributed on average 55 ± 19% to total copepod abundance and 82 ± 13% to total copepod biomass. Small-sized Oithona spp. (114–119 mg C m−2 d−1) and Clausocalanidae/Paracalanidae (87–263 mg C m−2 d−1) as well as large-sized Calanoides natalis (47–193 mg C m−2 d−1) were the dominant consumers at the most inshore stations. Small- and medium-sized copepodite stages of Metridia lucens were also important, especially towards the continental slope. At offshore stations, Clausocalanidae/Paracalanidae, Oithona spp., Pleuromamma spp., Calanus agulhensis, Acartia spp., C. natalis and M. lucens were dominant consumers. Hence, usually small- and medium-sized copepods dominated total copepod ingestion and egestion, emphasizing that inadequate representation of small copepods will lead to significant underestimations and misinterpretations of the functioning of zooplankton communities and finally to inadequate biogeochemical models.
    Type of Medium: Online Resource
    ISSN: 0142-7873 , 1464-3774
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 756271-8
    detail.hit.zdb_id: 1474909-9
    SSG: 12
    SSG: 21,3
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  • 7
    In: Molecular Ecology Resources, Wiley, Vol. 23, No. 2 ( 2023-02), p. 382-395
    Abstract: Species identification is pivotal in biodiversity assessments and proteomic fingerprinting by MALDI‐TOF mass spectrometry has already been shown to reliably identify calanoid copepods to species level. However, MALDI‐TOF data may contain more information beyond mere species identification. In this study, we investigated different ontogenetic stages (copepodids C1–C6 females) of three co‐occurring Calanus species from the Arctic Fram Strait, which cannot be identified to species level based on morphological characters alone. Differentiation of the three species based on mass spectrometry data was without any error. In addition, a clear stage‐specific signal was detected in all species, supported by clustering approaches as well as machine learning using Random Forest. More complex mass spectra in later ontogenetic stages as well as relative intensities of certain mass peaks were found as the main drivers of stage distinction in these species. Through a dilution series, we were able to show that this did not result from the higher amount of biomass that was used in tissue processing of the larger stages. Finally, the data were tested in a simulation for application in a real biodiversity assessment by using Random Forest for stage classification of specimens absent from the training data. This resulted in a successful stage‐identification rate of almost 90%, making proteomic fingerprinting a promising tool to investigate polewards shifts of Atlantic Calanus species and, in general, to assess stage compositions in biodiversity assessments of Calanoida, which can be notoriously difficult using conventional identification methods.
    Type of Medium: Online Resource
    ISSN: 1755-098X , 1755-0998
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2406833-0
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    Frontiers Media SA ; 2024
    In:  Frontiers in Marine Science Vol. 11 ( 2024-3-21)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 11 ( 2024-3-21)
    Abstract: Hyperiid amphipods of the genus Themisto are a key polar zooplankton group in terms of biomass and play an important role as prey for higher trophic levels. They are prone to undergo changes in abundance and distribution in the course of the ongoing environmental changes. In the Southern Ocean, Themisto gaudichaudii is predicted to expand its distribution poleward. In the Arctic, the boreal-Atlantic T. abyssorum increases in abundance, resulting in an increased competition with a genuine polar congener. It is not known, however, whether T. gaudichaudii and T. abyssorum have the potential to efficiently adapt to changing water temperatures at their current distribution range or whether they will be shifting their ranges poleward. Methods We exposed the two Themisto species from different geographic populations to temperature-change experiments, a cold treatment and a heat-shock treatment. After that, we carried out transcriptome sequencing to compare gene expression patterns in the different treatments and species. Results We show that under similar heat conditions, T. gaudichaudii differentially expressed more genes (26-fold change) than T. abyssorum . Furthermore, we observed qualitative differences between genetic clusters in T. gaudichaudii . Discussion The differences observed between genetic clusters in T. gaudichaudii suggest that evolutionary divergence can be linked to changes in the regulatory pathways involved in temperature stress. These could influence the capacity of each genetic cluster to cope differently with temperature changes. In contrast to its congeneric species, T. abyssorum showed a pronounced adaptive flexibility to thermal stress; it appears to have the ability to continue its poleward expansion but may also cope with increasing temperatures in its current environments. Our findings contribute to understand the response of two range-shifting Themisto species to thermal stress in view of the environmental gradients they encounter throughout their current or future distribution ranges.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2024
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2020
    In:  Biologie in unserer Zeit Vol. 50, No. 1 ( 2020-02), p. 28-35
    In: Biologie in unserer Zeit, Wiley, Vol. 50, No. 1 ( 2020-02), p. 28-35
    Abstract: Polar plankton Climatic changes such as the rise in temperature and ocean acidification have already severely impacted the planktonic life of the Southern Ocean. Our studies demonstrate that Antarctic plankton is changing. Large diatoms contribute most to primary production in the current Southern Ocean, whereas in the future small flagellates could become more abundant. Also zooplankton is impacted. Recent studies reveal a shift from a krill‐ to a salp‐dominated food web in the Southern Ocean and the replacement of polar cold‐water species by warm‐tolerant species of adjacent regions.
    Type of Medium: Online Resource
    ISSN: 0045-205X , 1521-415X
    URL: Issue
    RVK:
    Language: German
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 120079-3
    detail.hit.zdb_id: 2006653-3
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-8-26)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-8-26)
    Abstract: Life strategies, ecophysiological performances and diel vertical migration (DVM) of zooplankton key species affect the efficiency and strength of the biological carbon pump (BCP). However, it is unclear to what extent different functional groups affect the BCP. Depth-stratified day and night samples (0-800 m) from the subtropical South Atlantic were analyzed focusing on the calanoid copepod community. Calanoid abundance, biomass distribution and species-specific impact on the passive (fecal pellets) and active (via DVM) vertical flux of carbon were determined. Species were assigned to different migrant groups where, their contributions were estimated by using the proportion of the migratory community instead of simple day-night differences in biomass. This novel approach leads to more robust flux estimates, particularly for small sample sizes. According to migration ranges and day/night residence depth, functional groups were characterized, i.e. small- and large-scale epipelagic and mesopelagic migrants. Epipelagic small-scale migrants transported respiratory (1.5 mg C m -2 d -1 ) and fecal pellet (1.1 mg C m -2 d -1 ) carbon from the upper to the lower epipelagic zone, where the latter can fuel the microbial loop, and thus deep chlorophyll maxima, or be ingested by other zooplankton. Large-scale migrants actively transported up to 10.5 mg C m -2 d -1 of respiratory carbon from the epipelagic layer into the twilight zone. The majority was transported by Pleuromamma borealis (5.7 mg C m -2 d -1 ) into the upper mesopelagic. In addition, up to 8.0 mg C m -2 d -1 was potentially egested as fecal material by large-scale zone shifters. Mesopelagic migrants transported respiratory (0.2 mg C m -2 d -1 ) and fecal pellet carbon (0.1 mg C m -2 d -1 ) even deeper into the ocean. Community consumption of migrants in the epipelagic layer during the night was 98 mg C m -2 d -1 , while non-migrants consumed 98-208 mg C m -2 d -1 in the epipelagic zone, with a potential subsequent egestion of 29-62 mg C m -2 d -1 . This carbon may fuel omnivorous-detritivorous feeding, the microbial loop and/or may sink as fecal pellets. This case study shows how calanoid functional groups mediate carbon fluxes in the subtropical South Atlantic Ocean and demonstrates how detailed community analyses can elucidate the complexity of pelagic carbon budgets.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2757748-X
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