(26 - 27 of 27)
- Oceanic circumpolar habitats of Antarctic krill,
- Surveys of Euphausia superba often target localised shelves and ice edges where their growth rates and predation losses are atypically high. Emphasis on these areas has led to the current view that krill require high food concentrations, with a distribution often linked to shelves. For a wider, circumpolar perspective, we compiled all available net-based density data on postlarvae from 8137 mainly summer stations from 1926 to 2004. Unlike Antarctic zooplankton, the distribution of E. superba is highly uneven, with 70 % of the total stock concentrated between longitudes 0° and 90° W. Within this Atlantic sector, krill are abundant over both continental shelf and ocean. At the Antarctic Peninsula they are found mainly over the inner shelf, whereas in the Indian-Pacific sectors krill prevail in the ocean within 200 to 300 km of the shelf break. Overall, 87% of the total stock lives over deep oceanic water (>2000 m), and krill occupy regions with moderate food concentrations (0.5 to 1.0 mg chl am -3). Advection models suggest some northwards loss from these regions and into the low chlorophyll belts of the Antarctic Circumpolar Current (ACC). We found possible evidence for a compensating southwards migration, with an increasing proportion of krill found south of the ACC as the season progresses. The retention of krill in moderately productive oceanic habitats is a key factor in their high total production. While growth rates are lower than over shelves, the ocean provides a refuge from shelf-based predators. The unusual circumpolar distribution of krill thus reflects a balance between advection, migration, top-down and bottom-up processes. © Inter-Research 2008., Cited By (since 1996):76, CODEN: MESED, , , Downloaded from: www.int-res.com/articles/feature/m362p001.pdf (13 June 2014).
- Atkinson, Siegel, Pakhomov, Rothery, Loeb, Ross, Quetin, Schmidt, Fretwell, Murphy, Tarling, Fleming
- Krill space: A comparative assessment of mesoscale structuring in polar and temperate marine ecosystems
- The spatial organization, mesoscale variability, and habitat associations of krill within portions of the Antarctic Peninsula and California Current marine ecosystems are compared. Using a decade of acoustic observations and remotely sensed oceanography (20002009), the hypothesis that mesoscale spatial organization of krill in both systems closely relates to geospatial variability of the shelf break and is non-linearly related to geostrophic flow and positively related to chlorophyll a (Chl a) is tested. Directional-dependence analysis to measure spatial variability of krill is used along with spatially explicit generalized additive models to quantify and compare the spatial relationships among krill and habitat characteristics in both systems. The results suggest the following aspects of krill spatial organization: (i) areas of dense aggregation, i.e. hot spots, are present in both systems and are orientated in the direction of the shelf break, (ii) moderate levels of eddy kinetic energy seem to concentrate krill in favourable habitats and lessen the likelihood of advection away from the system, and (iii) variable responses to surface Chl a concentration suggest that real-time Chl a values may not be useful as a global predictor of important krill habitat. The results provide valuable reference points for marine spatial management of krill and for refining ecosystem and foodweb models., Cited By (since 1996):5, CODEN: ICESE
- Santora, Sydeman, Schroeder, Reiss, Wells, Field, Cossio, Loeb