Relationships between Antarctic krill (Euphausia superba) variability and westerly fluctuations and ozone depletion in the Antarctic Peninsula area

Abstract

An assessment of the environmental processes influencing variability in the recruitment and density of Antarctic krill (Euphausia superba) is important, as variability in krill stocks affects the Antarctic marine ecosystem as a whole. We have assessed variability in krill recruitment and density with hypothesized environmental factors, including strength of westerly winds (westerlies) determined from sea level pressure differences across the Drake Passage, sea ice cover, and ozone depletion. We found a significant positive correlation between krill recruitment in the Antarctic Peninsula area and the strength of westerlies during 1982–1998. Years with strong westerlies during the austral summer season resulted in high krill recruitment in 1987/1988, 1990/1991, and 1994/1995, while the years of weak westerlies resulted in low krill recruitment in 1982/1983, 1988/1989, 1992/1993, and 1996/1997. The strength of westerlies was significantly related to recruitment of 1‐year‐old krill (r = 0.57) and 2‐year‐old krill (r = 0.69) with a level of significance of 5%. In addition, the strength of westerlies also had a strong correlation with chlorophyll a (r = 0.63) and sea ice cover with a 1‐year time lag (r = 0.67). The strength of westerlies is considered to be a key environmental factor. We also found significant correlations between krill density in the Antarctic Peninsula area and the Antarctic ozone depletion parameters during 1977–1997 (e.g., total ozone in October at Faraday/Vernadsky Station of r = 0.76 with a level of significance of 1%). We suspect that ozone depletion impacts directly and/or indirectly on the variability in krill density.