Date of Award

Fall 2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

Eileen E. Hofmann

Committee Member

Kendra Daly

Committee Member

Gail E. Dodge

Committee Member

Chester E. Grosch

Committee Member

John M. Klinck

Abstract

The western Antarctic Peninsula (wAP) continental shelf is characterized by large persistent populations of Antarctic krill ( Enphausia superba) and by regions of enhanced concentrations of marine mammals and other predators (hot spots). This study focused on understanding the role of ocean circulation in providing retention/connectivity of wAP Antarctic krill populations and in maintaining biological hot spot regions. Numerical Lagrangian particle tracking simulations obtained from the Regional Ocean Modeling System (ROMS) configured for the wAP region provided quantitative estimates of retention, immigration and emigration from the wAP continental shelf. Additional simulations with a one-dimensional temperature-dependent growth model for krill embryos and early larval stages allowed mapping of the Lagrangian trajectories into krill developmental stages. The simulated particle trajectories showed preferred sites for across-shelf transport, with Marguerite Trough being a primary pathway for movement into Marguerite Bay, Crystal Sound, and the inner shelf regions. Residence times for the biological hot spots were 18 to 27 days for Alexander Island and Crystal Sound and almost 35 days for Laubeuf Fjord (biological hot spot regions). Particles released in the Bellingshausen Sea (remote source) were transported to the wAP shelf with a time scale consistent with the time required for Antarctic krill embryos to develop into larvae (120 days). The trajectories of floats released along the wAP shelf inside the 500-in isobath (local source) showed retention times on the order of 3 months and low connectivity among different release sites on the mid to inner shelf, suggesting that local reproduction and development can be important contributors to wAP Antarctic krill populations. Successful completion of the descent-ascent cycle of Antarctic krill embryo-larvae occurred along the outer shelf and in shelf regions where bottom depths were greater than 500 m. Estimated residence times in these areas were 20–30 days, which suggests that krill spawned in the mid and inner shelf are retained in these regions through development to the first feeding stage (calyptopis I). These results suggest that wAP Antarctic krill populations along the outer and mid shelf may be dependent on inputs from upstream sources. Maintenance of populations confined to the inner shelf regions may be dependent on local processes. Simulated trajectories obtained for projected future environmental conditions suggested that the circulation would enhance advection of krill larvae to the shelf but that recruitment and reproduction may be altered, thereby impeding survival of Antarctic krill.

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DOI

10.25777/815e-9176

ISBN

9781267108944

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