Relationships of Antarctic krill (Euphausia superba Dana) variability with westerlies fluctuations and ozone depletion in the Antarctic Peninsula area

The assessment of environmental processes controlling variability of Antarctic krill (Euphausia superba) is an important subject to clarify the Antarctic marine ecosystem. We have assessed variability of krill recruitment and stock density with hypothesised environmental factors. We demonstrated long-term relationship between Antarctic krill recruitment in the Antarctic Peninsula area and sea-level pressure gradients across Drake Passage during 1982-1993. The years with high pressure gradients meaning strong westerly winds coincided with good levels of krill recruitment in 1981182 (austral summer season), 1987/88 and 1990/91, while the years of extremely low values meaning weak westerly winds coincided with the extremely poor krill recruitment in 1982/83, 1983/84, 1988/89, 1991192 and 1992/93. We also found significant correlations between krill stock density in the Antarctic Peninsula area and the Antarctic ozone depletion during 1977-1994 (e.g. ozone hole's area: r=-0.844, p=0.001). This implied that the mean of krill stock densities after the 1984/85 decreased drastically as compared with that before 1982/83 with abrupt ozone depletion. With a gentle-ascending gradient of ozone depletion, however, krill stock density seems to be slightly recovering year by year after 1990 indicated a minimum of it. The association of krill variability with westerlies and ozone depletion suggests that it is of critical importance to the function of the Antarctic Peninsula area ecosystem.