Seasonal variations in population dynamics of Calanus finmarchicus in relation to environmental conditions in the southwestern Norwegian Sea

Inga Kristiansen, Sigrún H. Jónasdóttir, Eilif Gaard, Sólvá K. Eliasen, Hjálmar Hátun

Research output: Contribution to specialist publicationArticle

Abstract

A seasonal study of the life cycle and reproductive biology of the copepod Calanus finmarchicus – the dominant
zooplankton species and a key link between the lower and higher trophic levels within the southwestern Norwegian Sea - is presented. C. finmarchicus reproduces, feeds and accumulates lipids during spring and summer
within surface waters, which enables it to survive overwintering at depth until the following spring. An inflow of
warm and saline Atlantic Water (AW) enters from the southwest and meets the cold and less saline subarctic
waters (SAW) flowing from the north and west. This confluence establishes the dynamic Iceland Faroe Front. The
study includes seven cruises, conducted from July 2013 to July 2014. Ascent occurred earlier and over a prolonged period in AW compared to the SAW. The peak egg production per capita occurred in April (43 eggs
female− 1 d− 1
) and May (13 eggs female− 1 d− 1
) in SAW and AW, respectively. The higher productivity in SAW can
be explained by larger female size, increased lipid content and better feeding conditions. The increased egg
production rates in May in AW were not reflected in an increased abundance of young copepodite stages in June,
potentially due to a decoupling between early ascent and the late onset of the bloom. Descent, largely comprised
by the pre-adult stages, to overwintering depths was already initiated in June in both regions. This coincides with
increased lipid content, being significantly higher at depth compared to the surface in late summer. A smaller
portion of individuals remained within the upper layers to spawn a second generation in August in both regions,
increasing the abundance and biomass. The reproductive phenology and stage development of C. finmarchicus
likely influence feeding and competition between herring and mackerel and the duration of their stay in Faroese
waters
Original languageEnglish
Volume171
Specialist publicationDeep sea research part 1: oceanographic research papers
Publication statusPublished - 2021

Fingerprint

Dive into the research topics of 'Seasonal variations in population dynamics of Calanus finmarchicus in relation to environmental conditions in the southwestern Norwegian Sea'. Together they form a unique fingerprint.

Cite this