Distribution, Patchiness, and Behavior of Antarctic Zooplankton, Assessed Using Multi-Frequency Acoustic Techniques

• Main Author: Lawson, Gareth L.
• Other Authors: MASSACHUSETTS INST OF TECH CAMBRIDGE JOINT PROGRAM IN APPLIED OCEAN SCIENCE AND ENGINEERING
• Format: Text
• Language: English
• Published: 2006
• Subjects: Biology; Ecology; Geography; Optics; *ACOUSTICS; *ECOLOGY; *ANTARCTIC REGIONS; *BIOMASS CONVERSION; *ZOOPLANKTON; MATHEMATICAL MODELS; SPATIAL DISTRIBUTION; MEASUREMENT; POSITION(LOCATION); TEMPERATURE; ENVIRONMENTS; DISTRIBUTION; REGIONS; BAYS; TARGET STRENGTH; LAND AREAS; FOOD; MIGRATION; DIES; CONTINENTAL SHELVES; AVAILABILITY; WINTER; VERTICAL ORIENTATION; SURVEYS; RESOURCES; Antarctic; Marguerite; Marguerite Bay; The Antarctic; Antarc*; Antarctic Krill; Euphausia superba
• Online Access: http://www.dtic.mil/docs/citations/ADA458552; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA458552

The physical and biological forces that drive zooplankton distribution and patchiness on the antarctic continental shelf were examined, with particular emphasis on the Antarctic krill, Euphausia superba. Acoustic, video, and environmental data were collected during fall and winter surveys of the Marguerite Bay region in 2001 and 2002. Improved parametenzation of a theoretical model of krill target strength was achieved through direct measurement of all model parameters. Methods were developed and verified for acoustically distinguishing krill aggregations from other zooplankton, and estimating krill length, abundance, and biomass. Application of these methods to multi-frequency survey data demonstrated strong seasonal, inter-annual, and spatial variability in the distribution of both krill and overall zooplankton biomass. Highest krill biomass was consistently associated with regions close to land where temperatures at depth were cool. The vertical position and density of individual krill aggregations varied with time of day, food availability, and the occurrence of predators, suggesting that aggregation and die vertical migration represent a balance between avoiding visual predators and accessing shallowly distributed food resources. These findings have important implications to the fields of zooplankton acoustics and Antarctic krill ecology, especially in relation to the interactions of the krill with its predators. The original document contains color images.