Plankton

Event Date: 
Wednesday, March 26, 2014 - 19:00 - 20:00
Institution: 
UTS, Australia
Title: 

Feeling Hot Hot Hot: Insights on thermal regulation of microbial carbon fixation and metabolism in a warming ocean

Abstract: 

Ocean warming is expected to affect marine microbial phototrophs directly by influencing their metabolism and capacity for photosynthesis as well as indirectly through altering the supply of resources needed for growth. In turn, changes in phototrophic community composition, biomass and size structure are expected to have cascading impacts on export production, food web dynamics and fisheries yields, as well as the biogeochemical cycling of carbon and other elements. As a result, temperature is a critical parameter in coupled climate-ocean models because it influences not only the magnitude, but also the direction of future ocean productivity.
 
This seminar presents data from several recent oceanographic voyages to suggest that the statistically significant relationships found between temperature and carbon fixation of contemporary ocean microbes is confounded by the availability of co-varying light and nutrient resources, and challenges the notion that satellite-derived sea surface temperature is a suitable proxy for tracking changes in upper ocean biogeochemical function. It will also present laboratory data which demonstrates that thermal selection of photosynthetic microbes (over >100 generations) results in phenotypic trait evolution and shifts in photosynthesis:respiration. Collectively, these data show non-linearity in metabolism of photosynthetic microbes in a warming ocean, pointing to increased variability of responses and potentially less predictability in models.

Event Date: 
Wednesday, July 31, 2013 - 18:15 - 18:30
Institution: 
University of Technology Sydney
Title: 

The Sydney Harbour microbiome: bacterioplankton diversity and dynamics

Abstract: 

Sydney Harbour and its surrounding coast is an iconic habitat that supports a diverse ecosystem however the composition and dynamics of bacterioplankton in the system remain a major knowledge gap. The harbour and coast also provide a model system for investigating the spatiotemporal distribution of microorganisms across multiple physicochemical gradients and their response to anthropogenic input. Using next-generation DNA sequencing, we provide a comprehensive profile of microbial communities from a range of habitats inside the harbour and show strong biogeographic patterns in taxonomic composition.  Using network analysis to visualize correlations between community structure and environmental variables we have identified the key drivers of community partitioning. Combined these results lead to a more detailed understanding of the diversity and roles of bacterioplankton in Sydney Harbour and its surrounds, and provide insight into marine microbial ecology generally. 

Event Date: 
Wednesday, October 31, 2012 - 06:00 - 06:15
Institution: 
UTS
Title: 

Sulfur scent for a harmful algae killer

Abstract: 

 
Marine harmful algal blooms (HABs) are dense ephemeral proliferations typically of dinoflagellates, cyanobacteria or diatoms. These HABs can cause illness and death in humans and marine life, or ecosystem alterations affecting food provision and recreational activities. Despite being recognised as a major environmental challenge, little is known about what makes HABs thrive and vanish. For dinoflagellates, which account for 75% of HAB-forming phytoplankton species, bottom-up factors (including: eutrophication, climate change and species dispersal) are common triggers, yet the causes of bloom termination remain obscure.
Parasitoids have been identified as a major cause of termination of coastal harmful algal blooms, but the mechanisms and strategies they have evolved to efficiently infect ephemeral blooms are largely unknown. This study investigated the potential cues for parasite infection by the generalist dinoflagellate parasitoid Parvilucifera sinerae (Perkinsozoa, Alveolata). It showed that P. sinerae was activated from dormancy by Alexandrium minutum cells. Further investigation identified the algal metabolite dimethylsulphide (DMS) as the density-dependent chemical cue for the presence of potential host cells. The presence of DMS allowed the parasitoid to alternate between a sporangium-hosted dormant state and a chemically activated, free-living virulent state. DMS-rich exudates from infection-resistant dinoflagellate species also induced parasitoid activation, which can be interpreted as an example of a co-evolutionary arms race between parasitoid and host. These results further expand the involvement of dimethylated sulphur compounds in marine chemical ecology, where they have been described as foraging cues and chemoattractants for mammals, birds, fish, invertebrates and plankton microbes.

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