A comparative study of size-fractionated mesozooplankton biomass and grazing in the North East Atlantic

• Published in: Journal of plankton research Vol. 21; no. 12; pp. 2285 - 2308
• Main Authors: Head, R.N., Harris, R.P., Bonnet, D., Irigoien, X.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.12.1999; Oxford Publishing Limited (England)
• Subjects: Abundance; Animal and plant ecology; Animal, plant and microbial ecology; Atlantic Ocean; Biological and medical sciences; Biomass; Chlorophyll; Chlorophylls; Comparative studies; Drifting stations; Fundamental and applied biological sciences. Psychology; Grazing; Ingestion; Phytoplankton; Samples; Sea water ecosystems; Size; Synecology; Tracers; Zooplankton; East Atlantic; Atlantic Ocean; North Atlantic; ANE, Atlantic; Browsing; Environmental factor; Biological rhythm; Latitude; Biomass; Circadian rhythm; Crustacea; Marine environment; Arthropoda; Body size; Copepoda; Phytoplankton; Invertebrata; Zooplankton; Geographical variation
• ISSN: 0142-7873; 1464-3774; 1464-3774
• DOI: 10.1093/plankt/21.12.2285

Measurements of biomass and grazing for three size classes of mesozooplankton were carried out at two drifting stations: at 59°N, 20°W during a tracer release experiment, and at 37°N, 19°W at a conventional drifting station. Mesozooplankton biomass at 59°N did not vary between day and night (6.7 and 6.4 mg C m–3 for night and day samples, respectively). At 37°N, carbon biomass was much lower and in addition a diel cycle was observed (2.2 and 1.4 mg C m–3 for night and day samples, respectively). No one size fraction was the major contributor to biomass at either station. At 59°N, grazing was dominated by the small size fraction for both day and night samples, and at 37°N grazing was dominated by this size fraction during the day only. At 59°N, mean ingestion (57.1 and 91.1 mg C m–2 day–1 for day and night samples, respectively) was much higher than at 37°N (5.3 and 1.7 mg C m–2 day–1 for day and night samples, respectively). Consumption of the standing stock of phytoplankton (based on total chlorophyll a concentrations) was higher at the southern station where 8.9% and 2.6% day–1 of the standing stock was removed by night and day, respectively. Reverse diel consumption was observed at the northern station, where 1.5% (night) and 2.1% day–1 (day) of the standing stock was removed. Comparisons are made between the two time series, and the results are set in the context of a decade of investigations into the role of mesozooplankton in this region of the North Atlantic.