- Antarctic krill, Euphausia superba, are a highly abundant zooplankton species found in the Southern Ocean. They are a key food choice for higher trophic levels and are important consumers near the base of the food web. Changes to the environment of the Western Antarctic Peninsula (WAP), as a result of warming, are altering the marine pelagic ecosystem there. The size of the krill population in the region has decreased significantly over the past 90 years. Krill preferentially select diatoms over other phytoplankton species; however, diatoms are becoming less abundant and are being replaced by cryptophytes and primnesiophytes. Diatoms are an important source of polyunsaturated fatty acids that krill use for growth and development. I investigated whether changes in the abundance of diatoms (using the algal pigment, fucoxanthin, as a proxy) or in sea ice conditions (timing of advance and retreat) were related to the size (dry weight) and condition (caloric content standardized by weight) of juvenile krill. I found that there was a significant positive relationship between caloric content of juvenile krill and their dry weight. Further, my results indicated that juvenile krill caloric content and dry weight were positively correlated with a later sea ice advance and a higher abundance of diatoms. My results suggest that with continued increasing temperatures at the WAP and the predicted concurrent decline in diatom abundance, juvenile krill will be smaller and development may be delayed. This will negative implications for the krill population as a whole. This, coupled with increased harvesting of krill by humans, could negatively impact the entire Southern Ocean marine pelagic ecosystem.
- Key Words: Antarctic Krill, Western Antarctic Peninsula, sea ice duration, diatoms, Palmer LTER, caloric content.