Report from cruise with KV "Senja" and KV "Andenes" to the Barents Sea, 1-24 April 1986 : (PRO MARE cruise no.7)

The purpose of the cruise was to investigate the plankton development in early spring. This report, which is mainly administrative, summarizes information on cruise participants, cruise tracks and stations, sampling and laboratory facilities. An overview of hydrographical conditions and phytoplankton development is also given. Melting of ice in Atlantic water had produced stratified conditions which favoured early bloom development. In terms of phytoplankton, the stations occupied ranged from late winter prebloom situation to an active spring bloom situation half way towards nutrients depletio

Species composition of three size fractions of zooplankton used in routine monitoring of the Barents Sea ecosystem

Size fractionation with 2000 and 1000 μm screens is used by the Institute of Marine Research in Norway in routine monitoring of zooplankton biomass. This study examines the separation of taxa by this procedure. For copepods and cladocerans, the fractionation separates individuals according to their size in a consistent and predictable manner. Individuals up to 0.4 mm in width are contained in the small fraction (2 mm). For Calanus finmarchicus, young copepodites CI–CIII are contained in the small fraction, while the older stages CV and adults are contained in the medium fraction. Small copepods (Oithona, Oncaea, Microcalanus, Pseudocalanus) are contained in the small fraction, as are most appendicularians and meroplanktonic invertebrate larvae. The large fraction includes large copepods, larger individuals of chaetognaths, krill and amphipods. The consistency of separation of taxa by size will help to interpret and improve the ecological relevance of results on size-fractioned zooplankton biomass in the Barents Sea as well as other high-latitude areas.publishedVersio

Zooplankton reproduction in the Barents Sea vertical distribution of eggs and nauplii of Calanus finmarchicus in relation to spring phytoplankton development

Variable influence of ice melting on water column stabilization causes a large variation in timing of the spring phytoplankton bloom in the central Barents Sea. During two cruises in April 1986 and May-June 1987 situations were encountered that ranged from early bloom stage in Atlantic water not influenced by ice to late bloom stage in meltwater regions. In the present paper we examine the reproduction of Ca/anus finmarchirns (Gunnerus) against the background of this large natural variation in the temporal and spatial distribution of phytoplankton food, with emphasis on the vertical distribution of spawning females, eggs, and nauplii. The vertical distribution of the females indicated a shift from shallow spawning at the early bloom stations to deeper spawning in the pycnocline region at the late bloom stations. The females were generally concentrated in the layers with high concentrations of phytoplankton. The vertical distribution of eggs at the bloom and late bloom stations showed the same pattern as chlorophyll, either uniformly distributed in the upper mixed layer or concentrated as a sharp maximum in the region of the pycnocline and the deep chlorophyll maximum. The distribution of nauplii corresponded closely to the distribution of the eggs at these stations, suggesting little or no sinking of the eggs and hatching of the nauplii at depths with a rich food supply. The eggs at the ea rly bloom stations had a deeper distribution, although spawning apparently took place in the shallow part of the water column. This suggests a high rate of sinking of the eggs. Nauplii hatching from them probably encountered low food concentrations at great depths. The success of early spawning is probably limited through this. The indicated high sinking rate at the ea rly bloom stations in contrast to the low rate of sinking at the bloom and late bloom stations could reflect a difference in egg density owing to different feeding conditions. Increased water viscosity caused by mucus from phytoplankton could also have contributed to the lower sinking rate at high phytoplankton concentrations. Wind-induced vertical mixing did not play a major role in governing egg distributions

Implementing the ecosystem approach: experiences from the North Sea, ICES, and the Institute of Marine Research, Norway

Journal homepage: http://www.int-res.com/journals/meps

Growth of capelin in relation to zooplankton biomass in the Barents Sea

Growth of capelin in the Barents Sea stock has been found to vary considerably both between years and between different parts of the distribution area. The aim of this paper is to compare such growth variations with measured abundance of zooplankton within the capelin feeding area. In the period 1979-1984 a north-south transect in the Barents Sea was studied one to four times during summer. A negative relationship between the plankton biomass and the density of capelin along the section was evident. During the summer feeding migration the largest capelin, primarily the oldest, but also the largest individuals of each age group, were found in the front of the northward migration. Here they form a capelin front, which can be seen as eating its way through the plankton distribution. Length and weight of capelin were positively correlated with plankton density along the section. From 1987 to 1994, zooplankton abundance has been recorded on several stations taken along the track of an acoustic survey for capelin during September. The mean annual individual growth in weight of capelin was found to be positively correlated with average zooplankton density. The strongest relationships were found between one year old capelin and the smallest zooplankton size fraction, and between three years old capelin and the largest size fraction of plankton. Capelin length, weight and condition factor were also to some degree correlated with plankton density, although significant results were found for only some combinations of capelin age group and zooplankton size fraction

Seasonal development of plankton in the Barents Sea: A conceptual model

Capelin (Mallotus villosus) is a small salmonid fish that forms the basis of one of the most important fisheries in the Barents Sea. Relatively large variations in growth of capelin prompted ecological investigations on the feeding conditions of capelin and these were initiated by the Institute of Marine Research in 1979. The studies were expanded in 1984 with the start of the Norwegian Research Program for Marine Arctic Ecology (PRO MARE). A conceptual model for the seasonal development of plankton has provided a framework for our studies in the Barents Sea. The model emphasizes the importance of the ice edge spring phytoplankton bloom for the spawning and development of zooplankton and for the northwards seasonal feeding migration of capelin. The model is reviewed in light of field observations and some remaining key questions for our further studies are pointed out. While the main elements of the model have in broad terms been verified, it will in the future be necessary to put more emphasis on large scale processes such as transport of plankton by dominant currents and the ecological feedback interactions such as predation by capelin and grazing by zooplankton