Plankton food webs are characterized by complex interactions between lower trophic level groups, including viruses, prokaryotes, a diverse array of unicellular eukaryotes (including flagellates, ciliates, diatoms), microzooplankton and mesozooplankton. The responses of species and communities to environmental conditions set the framework for food web interactions that ultimately determine the transfer of energy to higher trophic levels. This project has the objective to advance understanding of lower trophic level interactions, to better inform ecosystem response to climate and anthropogenic driven shifts in ocean conditions.
This project will use the northeast Pacific as its experimental area. The Hakai Institute maintains an oceanographic observing program in the Strait of Georgia (British Columbia) that conducts year-round integrated measurements of the physical and chemical environment, and comprehensive sampling of lower trophic level biota. This program provides an ideal platform for detailed research of plankton food web linkages and interactions, including research labs, aquaria, and oceanographic sampling capabilities.
PDF position 1: Seasonal evolution and environmental controls of eukaryotic microbial plankton communities
The temporal and spatial dynamics of microbial communities is integral to understanding the function of planktonic food webs. Eukaryotic microorganisms, including the dominant phytoplankton (e.g., diatoms) and a diversity of mixotrophic and heterotrophic organisms. These organisms are typically understudied components of marine ecosystems, but serve a crucial role as the main prey of zooplankton and thus link lower and higher trophic levels of marine food webs. We seek a PDF to investigate the seasonal succession dynamics and interannual variability of marine eukaryotic microbes in response to bottom-up forcing (e.g., decreased nutrient availability, ocean acidification). This project will inform the response of eukarytotic microbes to environmental change in the northeast Pacific.
The PDF will have access to an ongoing sample collections, commenced in 2014, of the Hakai Institute’s Oceanographic Program in the Strait of Georgia. Samples are available to resolve eukaryotic microbial community dynamics using 18S rDNA amplicon sequencing, collected in conjunction with environmental data including nutrient concentrations, primary production rates, chlorophyll and other photosynthetic pigments via HPLC. The PDF will have the opportunity to explore eukarytic protists dynamics using tools including shotgun genomic or transcriptomic sequencing, experimental mesocosms, or other molecular or experimental approaches, as necessary.
PDF Position 2: Resolving zooplankton trophic pathways for enhanced prediction of food web response to a changing ocean
Understanding the response of zooplankton to changing ocean conditions requires detailed knowledge of their feeding biology, however, this knowledge has traditionally been extremely difficult to attain due to the challenges associated with identifying and quantifying zooplankton prey (e.g., small organism size, destruction of soft-bodied prey items in the gut, methods of limited taxonomic scope). DNA based methods, which can identify trace amounts of prey in zooplankton guts, circumvent these problems and offer to significantly improve understanding of lower trophic level interactions. We seek a PDF with expertise in either zooplankton or microbial ecology who is capable of applying high-throughput DNA sequencing approaches to resolve zooplankton feeding biology and food web linkages. This project will be supported by weekly to fortnightly field collections of plankton food web components (bacteria, protists and micro / mesozooplankton). To complement field and laboratory based research, facilities are also available for controlled feeding experiments. The findings of this project are expected to contribute directly to the development of lower trophic level food web models for the Strait of Georgia, British Columbia.
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