MEPS 753:1-18 (2025)  -  DOI: https://doi.org/10.3354/meps14767

ABSTRACT: Plankton dynamics in temperate ecosystems have mainly been studied during productive seasons, with comparatively less research conducted during the winter, particularly on microplankton. We implemented plankton sampling during a regular fishery cruise to investigate North Sea micro- and mesozooplankton community composition, abundance, and size structure (55-2000 µm) during autumn (Buchan/Banks area) and winter (Downs area) between 2013 and 2019. Samples were analyzed using image-based techniques. Community diversity (broad taxa) was relatively similar across years in both areas, with diatoms and tripos taxa sets dominating the microplankton community and gastropods and copepods dominating the mesozooplankton group. The average micro- to mesozooplankton ratio (in abundance) was 90:1 for Buchan/Banks, resulting in an average (±SD) normalized abundance size spectra (NASS) slope of -1.45 ± 0.18. For Downs, the micro- to mesozooplankton ratio was 235:1 with a steeper NASS slope of -1.67 ± 0.20 due to fewer large organisms. Interannual changes in the planktonic community for each area and their potential environmental drivers were examined using redundancy analysis (including taxonomy and size) and correlation analysis using NASS slopes (size only). Both approaches highlighted the importance of water mass properties (e.g. salinity, temperature, turbidity) in shaping plankton dynamics, although the amount of explained variance differed between approaches (11 vs. 46%). Our results contribute to a better understanding of standing stocks of plankton and their environmental drivers. Specifically, novel insights were gained into microplankton dynamics, which play an important role in supporting the growth and survival of winter-spawned fish larvae in the North Sea.

KEY WORDS: Plankton dynamics · Microplankton · Mesozooplankton · Size spectra · Image-based analysis · FlowCAM · ZooSCAN

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Cite this article as: Börner G, Frelat R, Akimova A, van Damme C, Peck MA, Moyano M (2025) Autumn and winter plankton composition and size structure in the North Sea. Mar Ecol Prog Ser 753:1-18. https://doi.org/10.3354/meps14767 Export citation Share:    Facebook - - Bluesky - linkedIn