Ecology of krill in Icelandic waters

• Main Author: Silva, Teresa Sofia Giesta da
• Other Authors: Ástþór Gíslason, Guðrún Marteinsdóttir and Ólafur S. Ástþórsson, Líf- og umhverfisvísindadeild (HÍ), Faculty of Life and Environmental Sciences (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Iceland, School of Engineering and Natural Sciences, Faculty of Life and Environmental Sciences 2018
• Subjects: Krill; Icelandic waters; Ecology; Biology; Long-term changes; Phytoplankton spring bloom dynamics; Onset of the phytoplankton spring bloom; Distribution; Climate change; Ljósáta; Sjávarvistfræði; Vistkerfi; Líffræði; Loftslagsbreytingar; Doktorsritgerðir; Iceland; Meganyctiphanes norvegica; North Atlantic; Thysanoessa inermis
• Online Access: https://hdl.handle.net/20.500.11815/982

Krill are an important component of the Icelandic marine ecosystem. Given their important ecological niche, as conveyors of biological production between phytoplankton and higher trophic levels, fluctuations in krill abundance can have large impacts on the dynamics of species at higher trophic levels. For this reason, understanding their population dynamics is of great importance. This thesis aims to contribute new insights into the biology of krill and their ecological role in the Icelandic marine ecosystem. The thesis is based on four scientific publications, three of which are published. One manuscript examines seasonal and long-term changes of krill in the North Atlantic (Paper I). The results show a significant decreasing trend in annual mean abundance of krill from 1958 to 2007 in the oceanic waters south and southwest of Iceland. It is hypothesized that a weakened temporal synchrony between the development of young euphausiids and the phytoplankton bloom influenced by recent climate warming may have led to the observed decrease in krill abundance. Two manuscripts assess krill abundance, distribution and development, in relation to environmental variables and phytoplankton spring bloom dynamics around Iceland (Papers II and III). Krill abundance was closely associated with abiotic factors (mainly temperature, salinity and bottom depth) and biotic factors (phytoplankton concentration and the onset of the phytoplankton bloom). Hydrographic conditions are important for growth and development. For instance, krill eggs and larvae were much more abundant in the warmer waters south of Iceland than in the colder waters off the north coast in May 2013. Adults were also most abundant in the warm water. Meganyctiphanes norvegica dominated in the Atlantic water in south and west of Iceland, whereas Thysanoessa inermis was found more evenly distributed around the island, while the highest values were also observed in the southwest for this species. The fourth paper evaluates the effect of temperature on physiological ...