Modelling the early life cycle of Antarctic krill: circumpolar success and sensitivity
Sally Thorpe, Eugene Murphy & Geraint Tarling
British Antarctic Survey, Natural Environment Research Council, UK
Antarctic krill is a central species of the Southern Ocean ecosystem, being the key prey for many higher predators and having an important role in the biogeochemical cycle. Antarctic krill has a circumpolar but asymmetric distribution, with areas such as the Scotia Sea containing a significant proportion of the biomass. What determines this distribution is a fundamental question in krill ecology, with impacts for the wider food web and its management.
Work towards a full life cycle model of Antarctic krill, linked to key environmental variables, is progressing. Here we will describe results from a coupled physical-biological model of the early stages of the life cycle of Antarctic krill, encompassing embryo development to the final larval stage. The model is run for the circumpolar Southern Ocean, employing time-varying depth-resolved temperature and density output from the 1/6 degree Southern Ocean State Estimation (SOSE) together with satellite-derived sea ice concentration data. SOSE is a numerical ocean model of the Southern Ocean that uses an adjoint method to assimilate hydrographic observations, thereby providing a physically realistic estimate of the ocean.
Results from the krill model allow us to identify areas of successful habitat for this particular part of the krill life cycle and the sensitivity of these areas to varying environmental conditions. Typical time scales in the model for development to the final larval stage of krill are upwards of three months. Over these periods, advection of the larval krill will move them through different physical regions. Sea ice is an important habitat for overwintering larval krill, providing both food and refuge from predators. By ascertaining the likely destination of larval krill in relation to sea ice cover as they go into winter, we can determine which source regions are likely to lead to successful overwintering for the young krill and assess their vulnerability to environmental change.
We will discuss these results in the context of our ongoing goal of an end-to-end model for the Southern Ocean pelagic ecosystem.