Abstract

It is known that Microsetella norvegica feed on phytoplankton and provide an important link to higher trophic levels in Arctic fjords, such as fish sprat (Sprattus sprattus) and three-spined stickleback (Gasterosteus aculeatus). It has recently been suggested that M. norvegica may also contribute substantially to carbon flux attenuation during periods of high abundance. However, we still know very little about how seasonal variations in abundance and vertical distribution of M. norvegica impact the efficiency of the biological carbon pump in Arctic fjords. We investigated the role of Microsetella norvegica, a small harpacticoid copepod, for particulate organic carbon flux attenuation via aggregate feeding in a subarctic fjord. We quantified the vertical distribution and abundance of M. norvegica, phytoplankton, and marine snow simultaneously with a Digital Autonomous Video Plankton Recorder in Porsangerfjord, northern Norway, between August 2013 and November 2014. We estimated the highest abundance of M. norvegica as 4.86x10(6) individuals m(-2) in October. Our results suggest that M. norvegica preferred diatoms over both marine snow and the prymnesiophyte Phaeocystis pouchetii during euphotic bloom conditions. However, during oligotrophic conditions when phytoplankton were scarce, M. norvegica switched to marine snow as a food source. M. norvegica has the potential to explain 1.4% and 0.29% of the total carbon flux attenuation in October and November, respectively. These results suggest that small copepods feed on settling detritus when no alternative food is available. Detritus feeding by M. norvegica may have an ecological impact during the polar night, both via direct carbon flux attenuation, but also as secondary producers in periods with low primary production. Currently small copepods such as M. norvegica are not included in carbon budgets or large-scale modelling, but considering their potentially high abundance they may represent an important but overlooked pathway in both the carbon cycle and trophic level interactions.

Keywords

marine snow; aggregates; fjord ecology; vertical distribution; video plankton recorder; flux attenuation

Published in

Frontiers in marine science
2023, Volume: 10, article number: 996275
Publisher: FRONTIERS MEDIA SA

SLU Authors

• Mooney, Benjamin

  • Department of Aquatic Resources (SLU Aqua), Swedish University of Agricultural Sciences
    
  • UiT The Arctic University of Tromso

UKÄ Subject classification

Oceanography, Hydrology, Water Resources
Ecology


Publication identifier

DOI: https://doi.org/10.3389/fmars.2023.996275

Permanent link to this page (URI)

https://res.slu.se/id/publ/123441