Why do zooplankton migrate between the sea surface and deeper waters?
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This project will focus on seasonal to daily changes in zooplankton migration, addressing the following questions: (1) How does the migratory behaviour change between winter (low phytoplankton production), spring (surface layer phytoplankton bloom) and summer (phytoplankton growth in the seasonal thermocline)? (2) Does the night-time migration consistently target particular features in the water column (e.g. the spring phytoplankton bloom in the surface layer, or the deep phytoplankton layer in the summer thermocline)? (3) What scales of patchiness are there in co-located zooplankton and phytoplankton distributions? (4) Is the alternative explanation for why daily migration is such a key feature of zooplankton life reasonable?
The work will take advantage of recently-acquired long time series of acoustic backscatter from moored Acoustic Doppler Current Profilers (ADCPs) in the Celtic Sea (1 year of data) and over the mid-Atlantic Ridge (8 months of data). While the ADCP backscatter signal provides a relative measure of zooplankton distribution, the data allow novel questions to be addressed because of the lengths of the time series and their vertical and temporal resolution. Alongside both ADCPs was a mooring measuring the vertical profile of temperature through the water column and surface biogeochemistry (chlorophyll and dissolved oxygen), providing the corresponding ocean structure to aid interpretation of the depths of migration. The project data are augmented by vessel-mounted ADCPs and collections of zooplankton samples during research cruises associated with deploying, servicing and recovering the moorings. Analysis will also include development of simple computer models of zooplankton migration within regions of vertical current shear, and the use of an existing computer model that tracks zooplankton “particles” in the upper ocean to test hypotheses on triggers for zooplankton migratory behaviour.
Competitive tuition fee, research costs and stipend (£14,056 tax free) from the NERC Doctoral Training Partnership “Understanding the Earth, Atmosphere and Ocean” (DTP website: http://www.liv.ac.uk/studentships-earth-atmosphere-ocean/) led by the University of Liverpool, the National Oceanographic Centre and the University of Manchester. The studentship is granted for a period of 42 months. Further details on eligibility, how to apply, deadlines for applications and interview dates can be found on the website. EU students are eligible for a fee-only award.
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La, H. S. et al. 2015. Acoustic backscatter observations with implications for seasonal and vertical migrations of zooplankton and nekton in the Amundsen shelf (Antarctica). Estuarine, Coastal and Shelf Science, 152, 124-133.
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