Publications
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Flo, Snorre; Bluhm, Bodil; Svensen, Camilla; Præbel, Kim & Vader, Anna
(2026).
Eukaryote diets in Arctic marine nematodes across seasons and shelf-to-basin gradients.
Polar Biology.
ISSN 0722-4060.
49(2).
doi:
10.1007/s00300-026-03475-0.
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Marine nematodes dominate the meiofauna of benthic sediments, but few have investigated their trophic roles. We studied the eukaryote diet composition of nematodes from sediments on the Arctic Barents Sea shelf, shelf break and adjacent Nansen Basin, during four seasons, using prey metabarcoding of the 18S ribosomal RNA gene. Monhysterida (n = 35 individuals), Chromadorida (34), Araeolaimida (27) and Enoplida (22) nematodes were most frequently observed across the study area, and diets were composed of diverse metazoan, fungal, and protist prey. In contrast to ambient sediment communities, prey followed a strong seasonal pattern, and ordination indicated two distinct seasonal prey clusters. In March and May prey were characterized by high relative abundances of fungi (42% and 48%, respectively). In comparison, August and December compositions had high relative abundances of arthropods (30% and 28%) and peritrich ciliates (11% and 9%, respectively). Notable protist prey included chlorophytes and dinoflagellates, whereas diatoms were highly abundant in the ambient sediment communities, but virtually absent as prey. Nematode taxonomy and buccal cavity morphology explained little of the variation in prey composition. Our results thus indicate that Arctic nematodes are generalists, which despite differences in morphology, can feed on a variety of eukaryotes. They further indicate that heterotrophs, such as fungi and arthropods, are important dietary items, although further studies need to determine the nature of interactions. Such dietary flexibility may enable nematodes to fuel continuous growth and reproduction in Arctic sediments where food items are seasonally varied.
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Flo, Snorre; Svensen, Camilla; Præbel, Kim; Bluhm, Bodil Annikki Ulla Barbro & Vader, Anna
(2024).
Dietary plasticity in small Arctic copepods as revealed with prey metabarcoding.
Journal of Plankton Research.
ISSN 0142-7873.
46(5),
p. 500–514.
doi:
10.1093/plankt/fbae042.
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Objectives: Small copepods (<2 mm) compose an important constituent of the Arctic marine food web, but their trophic interactions remain largely unexplored, partly due to methodological limitations. Methods: We here characterize the prey of the abundant cyclopoid Oithona similis, harpacticoid Microsetella norvegica and calanoid Microcalanus spp. from the Arctic Barents Sea and Nansen Basin during four seasons using brute force prey metabarcoding of the 18S rRNA gene. Key findings: Chaetognaths were unexpectedly the most consistently identified taxa and composed 47% of all prey reads. Some taxa were seasonally important, including diatoms in April–May (43%), dinoflagellates in December (15%) and March (17%), and urochordates in August (20%). Compositional differences among species were also discernible, and the M. norvegica diet was significantly different from both O. similis and Microcalanusspp. The diets varied nevertheless more with season than species despitethe inherenttrophictraitsthat distinguishthe ambushpredator O. similis, chemosensoric particle-chaser M. norvegica and current-feeding Microcalanus spp. Conclusions: Our results thus indicate that dietary plasticity is common in small Arctic copepods, regardless of their behaviors or strategies for finding sustenance. We further hypothesize that such plasticity is an important adaptation in systems where prey availability is highly seasonal.
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Flo, Snorre; Vader, Anna & Præbel, Kim
(2024).
Brute force prey metabarcoding to explore the diets of small invertebrates.
Ecology and Evolution.
14(5).
doi:
10.1002/ece3.11369.
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Prey metabarcoding has become a popular tool in molecular ecology for resolving trophic interactions at high resolution, from various sample types and animals. To date, most predator–prey studies of small-sized animals (<1 mm) have met the problem of overabundant predator DNA in dietary samples by adding blocking primers/peptide nucleic acids. These primers aim to limit the PCR amplification and detection of the predator DNA but may introduce bias to the prey composition identified by interacting with sequences that are similar to those of the predator. Here we demonstrate the use of an alternative method to explore the prey of small marine copepods using whole-body DNA extracts and deep, brute force metabarcoding of an 18S rDNA fragment. After processing and curating raw data from two sequencing runs of varying depths (0.4 and 5.4 billion raw reads), we isolated 1.3 and 52.2 million prey reads, with average depths of ~15,900 and ~120,000 prey reads per copepod individual, respectively. While data from both sequencing runs were sufficient to distinguish dietary compositions from disparate seasons, locations, and copepod species, greater sequencing depth led to better separation of clusters. As computation and sequencing are becoming ever more powerful and affordable, we expect the brute force approach to become a general standard for prey metabarcoding, as it offers a simple and affordable solution to consumers that is impractical to dissect or unknown to science.
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Sharma, Amit Kumar; Nymark, Marianne; Flo, Snorre; Sparstad, Torfinn; Bones, Atle M. & Winge, Per
(2021).
Simultaneous knockout of multiple LHCF genes using single sgRNAs and engineering of a high-fidelity Cas9 for precise genome editing in marine algae.
Plant Biotechnology Journal.
ISSN 1467-7644.
19,
p. 1–12.
doi:
10.1111/pbi.13582.
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The CRISPR/Cas9 system is an RNA-guided sequence-specific genome editing tool, which has been adopted for single or multiple gene editing in a wide range of organisms. When working with gene families with functional redundancy, knocking out multiple genes within the same family may be required to generate a phenotype. In this study, we tested the possibility of exploiting the known tolerance of Cas9 for mismatches between the single-guide RNA (sgRNA) and target site to simultaneously introduce indels in multiple homologous genes in the marine diatom Phaeodactylum tricornutum. As a proof of concept, we designed two sgRNAs that could potentially target the same six light-harvesting complex (LHC) genes belonging to the LHCF subgroup. Mutations in up to five genes were achieved simultaneously using a previously established CRISPR/Cas9 system for P. tricornutum. A visible colour change was observed in knockout mutants with multiple LHCF lesions. A combination of pigment, LHCF protein and growth analyses was used to further investigate the phenotypic differences between the multiple LHCF mutants and WT. Furthermore, we used the two same sgRNAs in combination with a variant of the existing Cas9 where four amino acids substitutions had been introduced that previously have been shown to increase Cas9 specificity. A significant reduction of off-target editing events was observed, indicating that the altered Cas9 functioned as a high-fidelity (HiFi) Cas9 nuclease.
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Flo, Snorre; Svensen, Camilla; Præbel, Kim; Bluhm, Bodil Annikki Ulla Barbro & Vader, Anna
(2023).
Seasonal Prey Composition of Three Small Arctic Copepods Assessed by Metabarcoding.
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Flo, Snorre; Svensen, Camilla; Præbel, Kim; Bluhm, Bodil & Vader, Anna
(2023).
Seasonal prey composition of three small Arctic copepods assessed by metabarcoding.
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Although the small size-fraction of copepods (<1 mm) are important constituents of the Arctic food-web, their trophic interactions remain largely unexplored, partly due to methodological limitations. We here characterize the prey of the cyclopoid Oithona similis, harpacticoid Microsetella norvegica and calanoid Microcalanus spp. from the Arctic Barents Sea and Nansen Basin in March, April-May, August, and December using brute force prey metabarcoding of the 18S rRNA gene. Of the prey identified, chaetognaths were the most consistently identified taxa and composed 47% of all prey reads. Reads from diatoms (16%), dinoflagellates (11%) and urochordates (8%) were likewise abundant, but these taxa were more prevalent during specific seasons. Diatoms composed 43% of prey reads in April-May, dinoflagellates 15% in December and 17% in March, and urochordates 20% in August. Although some species differences were also discernible, we show that the dietary composition varied more among seasons than among species. This was observed despite the taxonomic and behavioural differences that distinguish the ambush-predator O. similis, chemosensoric particle-chaser M. norvegica and current-feeding Microcalanus spp. The results thus indicate that dietary plasticity is common in small Arctic copepods, regardless of their behaviours or strategies for finding food. We moreover hypothesize that such plasticity is an important adaptation in systems where prey availability is highly seasonal.
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Flo, Snorre; Svensen, Camilla; Bluhm, Bodil; Præbel, Kim & Vader, Anna
(2022).
Small Arctic copepods – picky eaters or opportunistic generalists?
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Flo, Snorre; Vader, Anna; Bluhm, Bodil; Præbel, Kim & Svensen, Camilla
(2021).
DNA deep sequencing for exploring the diets of small Arctic copepods: take-home messages from a pilot study.
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Small copepods (<1 mm) are numerous and important components of the Arctic pelagic foodweb, but central biological aspects, such as diet preferences, remain largely unexplored. The recent maturation of dietary metabarcoding has made such studies possible. To enable detection of ingested prey DNA within the predator, blocking primers are often applied to limit detection of the predator’s own DNA. However, these primers may also introduce bias by blocking other sources. This study aims to develop a method that avoids this primer bias, while simultaneously examining the diets of three small and abundant copepods (Oithona similis, Microsetella norvegica and Microcalanus spp.) in the northern Barents Sea. Conceptually, we wanted to test if sequencing at greater depth could detect sufficient prey DNA, even though most of the DNA stem from the predator itself. From pilot sequencing, 314 million high-quality DNA reads and 72 628 zero-radius OTUs (zOTUs) were obtained from 75 copepods sampled in August and December 2019. Removal of zOTUs assigned to non-prey taxa (copepods, symbionts and contaminants), led to a putative prey dataset containing ~1.3 million reads and 1950 zOTUs. Notable prey items shared by all predators include ciliates, diatoms, dinoflagellates, chaetognaths, tunicates and marine fungi. Whereas early analyses indicate little interspecific variation in prey, there seems to be spatiotemporal differences within species (O. similis, M. norvegica).We show that sufficient prey can be detected without blocking primers. The seasonality of diets indicates potential for dietary plasticity, which could help explain continued activity in winter. Further work will include samples from spring, and to compare diets with in situ community profiles.
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Vader, Anna; Marquardt, Miriam; Summers, Natalie Maria; Flo, Snorre & Assmy, Philipp
(2022).
Chlorophyll A and phaeopigments Nansen Legacy cruise 2021704.
Norwegian Marine Data Centre.
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Ludvigsen, Martin; Assmy, Philipp; Adams, Matthew James Samuel; Arumi, Marti A.; Mo-Bjørkelund, Tore & Bodur, Yasemin V.
[Show all 36 contributors for this article]
(2022).
Seasonal cruise Q2 2021: Cruise Report.
Septentrio Academic Publishing.
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The spring season was the target for the Nansen Legacy cruise organized in late April and first half of May 2021 following the transect defined for this series of cruises to capture the variations of the year sampling physical, biological and chemical conditions in the ice and the sea. The transect went through both open water and ice. Seven process stations were visited (P1 through P7) together with smaller NLEG stations according to the program for the seasonal investigations. The first station (P1) was in open waters, while the remaining six main station had ice coverage of varying degree. Each of the process stations lasted 24 hours or more to allow a full diurnal cycle. Sampling included ice physics, ice samples, phytoplankton, zooplankton, marine chemistry and eco toxicology using acoustic, optical and robotics methods together with lab analyses of physical samples. Remote sensing data were also matched with in situ observations of both sea and ice conditions.
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Published
Mar. 19, 2026 2:02 PM
- Last modified
Mar. 19, 2026 2:06 PM
