Foraging behavior of antarctic krill Euphausia superba on sea ice microalgae

Abstract

The feeding behavior of antarctic knll Euphausia superba on ice algae was observed in situ and in the laboratory. Field observations by divers confirm that knll uLhze natural sea ice microalgae for food. Laboratory investigations show that melting ice releases algae into the water column which induces area-intensive foraging behavior in M1. This behavior is characterized by high speed swimming and rapid turning, accompanied by rapid opening and closing of the thoracic appendages, also known as the feedmg basket. Presentation of increased concentrations of ice algae to laboratory populations of knll significantly increased euphausiid responsiveness which led to location of and direct grazing upon the undersurfaces of ice containing microalgae. Foraging behavior of krill on ice algae appears to be affected by the spatial patchiness of the algae withln the ice and on the rate of algal cell release from ice. We propose that sea ice algae is an abundant and predictable food resource for knll during austral winters, when phytoplankton food resources are depleted.

Recruitment of Antarctic krill Euphausia superba and possible causes for its variability

“…This is supported by the fact that krill have regularly been observed under the winter ice ever since this has been researched as a krill habitat (e.g. Spiridonov et al 1985, Kottmeier & Sullivan 1987, Marschall 1988, Stretch et al 1988, Bergstrom et al 1990). Interannual variation in stock size does occur in the Peninsula region but…”

“…Dense winter ice concentrations apparently promote early female gonadal development and spawning. Krill undergo a seasonal shift from phytoplankton feeding in spring and summer to grazing on ice algae in winter (Spiridonov et al 1985, Kottmeier & Sullivan 1987, Marschall 1988, Stretch et al 1988, Bergstrom et al 1990). During winters with low concentration and short duration of ice cover there may be insufficient food supplies for krill to satisfy their energy requirements and to initiate early gonadal development.…”

In situ net primary productivity of an Antarctic fast ice bottom algal community

“…Accumulation of sea ice algal biomass is not just a function of how much light it has received. We have shown here that under-ice current velocity and possibly oxygen build-up and grazing by amphipods and krill (Marshal1 1988, Stretch et al 1988, Daly 1990 influence biomass accumulation and photosynthetic rates. The amount of light received by the algae in this study was higher than that reported in most previous studies but cannot be considered rare.…”

Comparisons of Feeding Ecology of Euphausia pacifica from Korean Waters Using Lipid Composition

“…실제로, 남빙해의 Euphausia superba 는 극한 환경에서의 생존을 위하여 계절 및 서식 환경에 따라 해빙 생물상 (Stretch et al 1988;Daly 1990), 동물플 랑크톤 (Hopkins et al 1993;Huntley et al 1994), 유기 쇄 설물 (Kawaguchi et al 1986) 등 다양한 종류의 먹이원을 이용하고 있다. 또한, 북동 일본 연안에서 E. pacifica는 식물플랑크톤 대발생이 일어나는 시기에는 초식성향을 강 하게 갖지만, 그 외 계절에는 소형 동물플랑크톤을 섭식하 는 것으로 보고되고 있다 (Nakagawa et al 2003).…”