Winter Carnivory and Diapause Counteract the Reliance on Ice Algae by Barents Sea Zooplankton

The Barents Sea is a hotspot for environmental change due to its rapid warming, and information on dietary preferences of zooplankton is crucial to better understand the impacts of these changes on food-web dynamics. We combined lipid-based trophic marker approaches, namely analysis of fatty acids (FAs), highly branched isoprenoids (HBIs) and sterols, to compare late summer (August) and early winter (November/December) feeding of key Barents Sea zooplankters; the copepods Calanus glacialis, C. hyperboreus and C. finmarchicus and the amphipods Themisto libellula and T. abyssorum. Based on FAs, copepods showed a stronger reliance on a diatom-based diet. Phytosterols, produced mainly by diatoms, declined from summer to winter in C. glacialis and C. hyperboreus, indicating the strong direct linkage of their feeding to primary production. By contrast, C. finmarchicus showed evidence of year-round feeding, indicated by the higher winter carnivory FA ratios of 18:1(n-9)/18:1(n-7) than its larger congeners. This, plus differences in seasonal lipid dynamics, suggests varied overwintering strategies among the copepods; namely diapause in C. glacialis and C. hyperboreus and continued feeding activity in C. finmarchicus. Based on the absence of sea ice algae-associated HBIs (IP25 and IPSO25) in the three copepod species during both seasons, their carbon sources were likely primarily of pelagic origin. In both amphipods, increased FA carnivory ratios during winter indicated that they relied strongly on heterotrophic prey during the polar night. Both amphipod species contained sea ice algae-derived HBIs, present in broadly similar concentrations between species and seasons. Our results indicate that sea ice-derived carbon forms a supplementary food rather than a crucial dietary component for these two amphipod species in summer and winter, with carnivory potentially providing them with a degree of resilience to the rapid decline in Barents Sea (winter) sea-ice extent and thickness. The weak trophic link of both zooplankton taxa to sea ice-derived carbon in our study likely reflects the low abundance and quality of ice-associated carbon during late summer and the inaccessibility of algae trapped inside the ice during winter.

Download Full-text

Multiple Trophic Markers Trace Dietary Carbon Sources in Barents Sea Zooplankton During Late Summer

Frontiers in Marine Science ◽

10.3389/fmars.2020.610248 ◽

2021 ◽

Vol 7 ◽

Author(s):

Doreen Kohlbach ◽

Haakon Hop ◽

Anette Wold ◽

Katrin Schmidt ◽

Lukas Smik ◽

...

Keyword(s):

Sea Ice ◽

Food Web ◽

Barents Sea ◽

Carbon Sources ◽

Late Summer ◽

Mean Value ◽

Ice Algae ◽

Additional Indication ◽

Small Copepod ◽

Sea Ice Algae

We investigated diets of 24 Barents Sea zooplankton taxa to understand pelagic food-web processes during late summer, including the importance of sea ice algae-produced carbon. This was achieved by combining insights derived from multiple and complementary trophic marker approaches to construct individual aspects of feeding. Specifically, we determined proportions of algal-produced fatty acids (FAs) to reflect the reliance on diatom- versus dinoflagellate-derived carbon, highly branched isoprenoid (HBI) lipids that distinguish between ice-associated and pelagic carbon sources, and sterols to indicate the degree of carnivory. Copepods had the strongest diatom signal based on FAs, while a lack of sea ice algae-associated HBIs (IP25, IPSO25) suggested that they fed on pelagic rather than ice-associated diatoms. The amphipod Themisto libellula and the ctenophores Beroë cucumis and Mertensia ovum had a higher contribution of dinoflagellate-produced FAs. There was a high degree of carnivory in this food web, as indicated by the FA carnivory index 18:1(n−9)/18:1(n−7) (mean value < 1 only in the pteropod Clione limacina), the presence of copepod-associated FAs in most of the taxa, and the absence of algal-produced HBIs in small copepod taxa, such as Oithona similis and Pseudocalanus spp. The coherence between concentrations of HBIs and phytosterols within individuals suggested that phytosterols provide a good additional indication for algal ingestion. Sea ice algae-associated HBIs were detected in six zooplankton species (occurring in krill, amphipods, pteropods, and appendicularians), indicating an overall low to moderate contribution of ice-associated carbon from late-summer sea ice to pelagic consumption. The unexpected occurrence of ice-derived HBIs in pteropods and appendicularians, however, suggests an importance of sedimenting ice-derived material at least for filter feeders within the water column at this time of year.

Download Full-text

Sedimentation of 13C-rich organic matter from Antarctic sea-ice algae: A potential indicator of past sea-ice extent

Geology ◽

10.1130/0091-7613(1999)027<0331:socrom>2.3.co;2 ◽

1999 ◽

Vol 27 (4) ◽

pp. 331 ◽

Cited By ~ 74

Author(s):

John A E. Gibson ◽

Tom Trull ◽

Peter D. Nichols ◽

Roger E. Summons ◽

Andrew McMinn

Keyword(s):

Organic Matter ◽

Sea Ice ◽

Ice Algae ◽

Sea Ice Extent ◽

Sea Ice Algae ◽

Antarctic Sea Ice ◽

Potential Indicator

Download Full-text

Seasonal and latitudinal variations in sea ice algae deposition in the Northern Bering and Chukchi Seas determined by algal biomarkers

PLoS ONE ◽

10.1371/journal.pone.0231178 ◽

2020 ◽

Vol 15 (4) ◽

pp. e0231178 ◽

Cited By ~ 5

Author(s):

Chelsea Wegner Koch ◽

Lee W. Cooper ◽

Catherine Lalande ◽

Thomas A. Brown ◽

Karen E. Frey ◽

...

Keyword(s):

Sea Ice ◽

Ice Algae ◽

Sea Ice Algae ◽

Latitudinal Variations

Download Full-text

Climate-driven benthic invertebrate activity and biogeochemical functioning across the Barents Sea polar front

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2019.0365 ◽

2020 ◽

Vol 378 (2181) ◽

pp. 20190365 ◽

Cited By ~ 3

Author(s):

Martin Solan ◽

Ellie R. Ward ◽

Christina L. Wood ◽

Adam J. Reed ◽

Laura J. Grange ◽

...

Keyword(s):

Sea Ice ◽

Ecosystem Functioning ◽

Barents Sea ◽

Benthic Invertebrate ◽

Polar Front ◽

The Arctic ◽

Nutrient Concentrations ◽

Sea Ice Extent ◽

Biological Communities ◽

The Barents Sea

Arctic marine ecosystems are undergoing rapid correction in response to multiple expressions of climate change, but the consequences of altered biodiversity for the sequestration, transformation and storage of nutrients are poorly constrained. Here, we determine the bioturbation activity of sediment-dwelling invertebrate communities over two consecutive summers that contrasted in sea-ice extent along a transect intersecting the polar front. We find a clear separation in community composition at the polar front that marks a transition in the type and amount of bioturbation activity, and associated nutrient concentrations, sufficient to distinguish a southern high from a northern low. While patterns in community structure reflect proximity to arctic versus boreal conditions, our observations strongly suggest that faunal activity is moderated by seasonal variations in sea ice extent that influence food supply to the benthos. Our observations help visualize how a climate-driven reorganization of the Barents Sea benthic ecosystem may be expressed, and emphasize the rapidity with which an entire region could experience a functional transformation. As strong benthic-pelagic coupling is typical across most parts of the Arctic shelf, the response of these ecosystems to a changing climate will have important ramifications for ecosystem functioning and the trophic structure of the entire food web. This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.

Download Full-text

Preliminary investigation of Okhotsk Sea ice algae; taxonomic composition and photosynthetic activity

Polar Biology ◽

10.1007/s00300-008-0433-0 ◽

2008 ◽

Vol 31 (8) ◽

pp. 1011-1015 ◽

Cited By ~ 22

Author(s):

A. McMinn ◽

H. Hattori ◽

T. Hirawake ◽

A. Iwamoto

Keyword(s):

Sea Ice ◽

Photosynthetic Activity ◽

Preliminary Investigation ◽

Taxonomic Composition ◽

Ice Algae ◽

Okhotsk Sea ◽

Sea Ice Algae

Download Full-text

Multi-aspect Assessment of CMIP6 Models for Arctic Sea Ice Simulation

Journal of Climate ◽

10.1175/jcli-d-20-0522.1 ◽

2020 ◽

pp. 1-37

Author(s):

Mengyuan Long ◽

Lujun Zhang ◽

Siyu Hu ◽

Shimeng Qian

Keyword(s):

Sea Ice ◽

Temporal Variation ◽

Spatial Patterns ◽

Barents Sea ◽

Linear Trend ◽

Arctic Sea Ice ◽

Sea Ice Concentration ◽

Sea Ice Extent ◽

East Greenland ◽

Arctic Sea

AbstractThis paper evaluates the ability of 35 models from the 6th phase of the Coupled Model Intercomparison Project (CMIP6) to simulate Arctic sea ice by comparing simulated results with observation from the aspects of spatial patterns and temporal variation. The simulation ability of each model is also quantified by Taylor score and e score from these two aspects. Results show that biases between observed and simulated Arctic sea ice concentration (SIC) are mainly located in the East Greenland, Barents, Bering Sea and Sea of Okhotsk. The largest difference between the observed and simulated SIC spatial patterns occurs in September. Since the beginning of the 21st century, the ability of most models to simulate summer SIC spatial patterns has decreased. We also find that models with Sea Ice Simulator (SIS) sea-ice component in CMIP6 show a consistent larger positive simulation biases of SIC in the East Greenland and Barents Sea. In addition, for most models, the higher the model resolution is, the better the match between the simulated and observed spatial patterns of winter Arctic SIC is. Furthermore, this paper makes a detailed assessment for temporal variation of Arctic sea ice extent (SIE) with regard to climatological average, seasonal SIE, multi-year linear trend and detrended standard deviation of SIE. The sensitivity of September Arctic SIE to a given change of Arctic surface air temperature (SAT) over 1979-2014 in each model has also been investigated. Most models simulate a smaller loss of September Arctic SIE per degree of warming than observed (1.37×106 km2 K-1).

Download Full-text