남극 북서대서양 해역에서의 일차생산력과 그것이 가지는 의미

Abstract

According to Atkinson et al. (2004), the productive southwest Atlantic sector contains >50% of Southern Ocean krill stocks, but here their density has declined since the 1970s. Spatially, within their habitat, summer krill density correlates positively with chlorophyll concentration. The large-scale circumpolar pattern of principal krill concentrations aligns with the Southern Boundary (Tynan, 1998). Temporally, within the southwest Atlantic, summer krill densities correlate positively with sea-ice extent in the previous winter (Loeb et al., 1997; Atkinson et al., 2004). Food supply and shelter are the key factors that determine the krill density in the southwest Atlantic Ocean. Therefore, accurate estimation of primary production and assessment of its variability is important in understanding the dynamics of krill populations. Various approaches have been made to assess the temporal and spatial variability of primary productivity in the Southern Ocean. Estimates of primary production from recent studies range 35 ~ 100 Gt C yr-1 for the global ocean, and 3 ~ 5 Gt C yr-1 for the Southern Ocean. Estimates from remote sensing data are ~3 times higher than estimates based on in situ data. Certainly, refinement of primary productivity assessment is necessary. In this respect, we conducted five cruises in the region circumscribed by 52 ~ 66°S and 70 ~ 46°W which includes the Drake Passage, south-western Scotia Sea, and north-eastern Bellingshausen Sea during austral summer in 2001 ~ 2005. We directly measured bio-optical variables including photoadaptation parameters and assimilation number of primary production using C-14 method at 64 stations.Here, we attempt to elucidate how primary production can be linked to krill biomass and distribution in the study area and we also make suggestions for further studies to assess the impact of changing primary productivity on the Antarctic ecosystems.