Two PhD Positions in Soft-Sediment Ecology
Date Posted: 30 September 2009

The Marine Ecology Research Group of Canterbury University and the National Institute of Water & Atmospheric Research are jointly seeking TWO PhD students to work in a new program entitled “After the outfall: recovery from eutrophication in degraded New Zealand estuaries”. Applicants must have completed a thesis as part of a BSc Honours or MSc degree (preferred), and achieved excellent grades.

Initial contact outlining your background, interests and (unofficial) record should be made either to Professor David Schiel (david.schiel@canterbury.ac.nz) or Dr John Zeldis (j.zeldis@niwa.co.nz). We intend to start the student program as quickly as possible, but it is expected that candidates will apply for scholarship support in the next scholarship round at the University of Canterbury (deadline: 15 October 2009). Information on University scholarships can be found at http://www.canterbury.ac.nz/scholarships/ucschols/uc_doctoral.shtml (for NZ students), and http://www.canterbury.ac.nz/scholarships/ucschols/uc_intl_doc.shtml (international students).

The intended PhD programs and specific qualifications required are outlined below.

Overview
This project will provide new information on the processes and time scales of change in coastal ecosystems that have been severely impacted by excess nutrients but are subject to rehabilitation following nutrient reduction. To do this we will take advantage of the unique event provided by the wastewater diversion from the Avon-Heathcote estuarine system in Christchurch into an ocean outfall, one of the largest and most expensive such diversions ever done in NZ, that will begin late in 2009. This will result in a 90% reduction in the nutrient loading to this area that has caused wide-scale degradation for the past 50 years. This project will allow spatially and temporally explicit assessments to be made of gradients and thresholds of recovery of key ecosystem processes following this event.

1. PhD: Benthic invertebrate food webs relating to thresholds in sediment changes
On soft-sediment flats, increases in the supply of organic matter due to eutrophication (i.e., more food) may enhance faunal biomass, though sediment anoxia and smothering by macroalgal detritus may detrimentally affect fauna. This will likely create mosaic-like spatial and temporal patterns when eutrophication is remediated. This project will test responses of key macrofauna (richness, diversity, abundance and biomass) to significantly reduced nutrient inputs using spatio-temporal sampling techniques within and across ecotypes, as they change post-diversion. Cohort-based growth modelling for abundant indicator species (e.g., cockles, mudsnails) will be done along with multivariate community analyses to track change. Isotopic analysis will be used to further pinpoint faunal food sources and trophic positions, to understand significance of diversion-driven changes on food resources and to underpin understanding of abundance and diversity trends.

Qualifications: Applicants must have completed a thesis as part of a BSc Honours or MSc degree (preferred), and achieved excellent grades A strong background in experimental soft-sediment ecology and biostatistics. Familiarity with stable isotope techniques and analyses would be an advantage.

2. PhD: Isotopic Food Web Analysis
After diversion of the wastewater from the Avon-Heathcote Estuary, estuary nutrient sources will be driven by rivers and oceanic inputs and by the legacy of the wastewater inputs arising from sediments. The successful applicant for this project will use stable isotope tracing of carbon and nitrogen nutrient source pools through the ecosystem to separate the source pools and trace how they change with time after diversion, and thereby control estuary water quality and uptake of nutrients by the ecosystem. The work will involve ionic diffusion techniques to assay aqueous isotope sources (rivers, ocean, sediment porewater) and biotic sources (particulate matter, plants and animals) of the estuary. Results will be analysed and interpreted using isotopic mixing models to isolate the important contributors of carbon and nitrogen to the ecosystem, and how they change with estuarine remediation from eutrophication. The position will work within, and in partnership with, a large well- funded research programme covering all major ecosystem components.

Qualifications: Applicants must have completed a thesis as part of a BSc Honours or MSc degree (preferred), and achieved excellent grades A background in the theory and practice of isotopic analysis of ecosystems including modelling is a strong advantage.

One MSc Position in Soft-Sediment Ecology
Date Posted: 30 September 2009

3. MSc: Macroalgal dynamics in a recovering estuary
A reduction in algal biomass, particularly of Ulva and Gracilaria, should occur soon after diversion of the outfall in late 2009. This project will use total tissue-N and C content, and more recently developed measures of free amino acids, as well as the ratio of C:N, to evaluate intracellular N-indices. Responses to nutrient reduction will be tested in seasonal experiments, run concurrently with seasonally-based field sampling of the N-index through the post-diversion period (to remove seasonal effects), accompanied by PAM and oxygen-based productivity experiments to understand macro-algal responses in this and other NZ estuaries where N abatement may be undertaken. These techniques are known to be viable and will reveal growth-nutrient kinetics after diversion. Algal stable isotopes to isolate their nutrient source pools.

Qualifications: An understanding of relevant macroalgal ecophysiology, with some appreciation of biochemical techniques and working in the laboratory environment, is essential. An understanding of the application of stable isotopes would also be an advantage. Only New Zealand students.

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