The seasonal development of the zooplankton community in a British Columbia (Canada) fjord during two years with different spring bloom timing

Abstract

Variability in phytoplankton and zooplankton dynamics were studied during spring and early summer of 2006 and 2007 in Rivers Inlet, a fjord on the central coast of British Columbia, Canada. The onset of the spring bloom was shifted by 3 weeks in 2007 (26 April) compared to 2006 (7 April). The later 2007 bloom was accompanied by a later and lower zooplankton biomass peak and a different zooplankton composition. Mean spring–summer total zooplankton biomass was 57 and 27 mg m⁻³ in 2006 and 2007, respectively. This was explained by reduced juvenile densities and changes in dominance of most abundant zooplankton taxa in the fjord. Between 2006 and 2007 mean densities of copepod nauplii and calanoid copepodites decreased from 224.3 to 95.8 and from 197.7 to 35.9 ind. m⁻³, respectively. Adult Calanoidae and Metridinidae decreased in abundance while densities of Acartiidae and Ectinosomatidae increased. We postulate that the later bloom delayed the seasonal increase in zooplankton biomass by inhibiting the survival of early developing stages of certain zooplankton species through a mismatch between their appearance and the spring bloom. This study provides the first baseline observation on the temporal scale of zooplankton phenological changes in the region.

Keywords:

• Zooplankton
• phenology
• spring bloom
• community structure
• fjord
• British Columbia

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

This research was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Tula Foundation. We thank Lora Pakhomova and Chris Payne for performing nutrient samples analysis; Tom and Laurie Ainsworth, Krystal Bachan, Kyla Burrill, Karen Magnuson-Ford, Amy McConnell and Laleh Sandrei for help with field data collection; Ron Tanasichuk, John Reynolds and Susan Allen for reviewing earlier drafts and helpful discussions; and the Bachen family and Salmon King Lodge for providing accommodation and assistance with field logistics. This project would not have been possible without the support of the Oweekeno First Nation, particularly the Western Bounty crew.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark