## 4 Discussion
### Key Environmental Factors of the Habitat of Krill and Their Impacts  
Antarctic krill play a pivotal role in the material cycling and energy flow of the Antarctic ecosystem. In this study, an integrated species distribution model was employed to analyze the impacts of various environmental factors and quantify the relative contributions of each factor to the distribution of krill habitats, thus providing a scientific basis for revealing the driving mechanisms of the habitats. Since krill fishing vessels operate in different sub-regions in some months, it is likely to cause errors in the suitable ranges of environmental factors. Therefore, the suitable ranges of environmental factors corresponding to the highly suitable habitats (HSI \(\geq\) 0.8) when operating solely in a specific sub-region were selected for discussion. As shown in Figures 3 and 4 and Table 1, GLD, as a key determinant of basicity and stability, plays an extremely important role in habitat suitability, with an average monthly contribution rate of approximately 34.9%. Moreover, the environmental response curves of GLD exhibit significant differences in different operating sub-regions. In sub-regions 48.1 and 48.3, the GLD values are at a relatively low level (GLD \(<\) 12 km), and the peak suitable range is 0.35-2.45 km, while the GLD values in sub-region 48.2 are relatively high (30-50 km), with a peak suitable range of 43.05-44.66 km. This phenomenon may be due to the fact that during the seasonal alternation, the distribution of krill will migrate back and forth according to the extension direction of the continental shelf [38; 39], or it is related to the fact that krill inhabit the ice edge zone and their distribution is affected by the expansion and retreat of sea ice. Some studies have shown that within the range of 0-50 km, the biomass of krill groups is more than twice that in waters beyond 200 km [40]. CHL is directly related to the food supply of krill. In spring and summer, the massive proliferation of phytoplankton is a key factor affecting the recruitment of krill populations near the Antarctic Peninsula, with an average monthly contribution rate of approximately 25.2%. When it is spring and summer (from September to February of the following year) and the CHL concentration is relatively high, the suitable range is 0.34-2.68 mg/m\({}^{3}\), and the peak suitable range is 1-2.13 mg/m\({}^{3}\). At this time, the environmental factor response curve of CHL shows a trend of rising first and then falling. It is worth noting that when choosing habitats, krill do not solely rely on areas with high CHL concentrations, because high-resource areas are often accompanied by more predators, resulting in a higher predation risk for krill. Therefore, krill may choose to inhabit areas with relatively less food resources but lower predation risks to balance resource acquisition and their own survival security, thereby ensuring the stability of the population [38]. In autumn and winter (from March to August), the CHL concentration is relatively low, with a suitable range of 0.19-2.6 mg/m\({}^{3}\) and a peak suitable range of 0.27-2.05 mg/m\({}^{3}\), and the corresponding environmental factor response curve shows an upward trend. This may be because food is relatively scarce in winter, and krill will tend to choose areas with relatively higher CHL concentrations for foraging activities in order to obtain sufficient food. Some studies have shown that the distribution of CHL in the Southern Ocean exhibits obvious spatiotemporal distribution characteristics, with higher CHL values near islands and in shelf waters [41], and the high aggregation areas of Antarctic krill are basically located in the inshore waters with relatively higher CHL concentrations [2; 42]. In this study, it was found that GLD and CHL interact with each other, and their comprehensive contribution rate exceeds 60%, jointly determining the habitat suitability and constituting the core environmental framework of habitat suitability, thus further confirming the above conclusions.