Biological oceanography

Event Date: 
Wednesday, September 30, 2015 - 18:15 - 18:30
Institution: 
UTS
Title: 

Divergence in temperature stress management between coastal and East Australian current (EAC) phytoplankton populations.

Abstract: 

In June 2015, 27 scientists took part in a 3 week ocean voyage aboard the brand new Australian research vessel, the RV Investigator. The main objective of the expedition was to study sub-mesoscale processes - billows and eddies - along the productive shelf influenced by the East Australian Current. Dr Olivier Laczka is presenting the results obtained for one of the multiple projects conducted during this voyage. Microbial communities from the EAC and a coastal site (north of Smokey Cape) were incubated along a temperature gradient (spanning 32 to 15.5 °C) to examine their capacity to deal with departures from in situ temperature (~22 °C). Intracellular stress within picoeukaryote populations was examined using a fluorescent stain targeting Reactive Oxygen Species (ROS). Stained samples were examined with a flow cytometer (excitation wavelength 488 nm). The goal of this study was to assess whether EAC microbial communities are more thermally tolerant than coastal microbial communities and determine whether general oxidative stress patterns could be used as a signature of water mass origins.

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, March 27, 2013 - 19:15 - 20:00
Institution: 
Alfred Wegener Instute for Polar and Marine Research
Title: 

Alexandrium: Evolutionary and ecological insights into the most prominent toxigenic dinoflagellate

Abstract: 

Dinoflagellates are a major cause of harmful algal blooms, with consequences for coastal marine ecosystem functioning and services.  Representatives of Alexandrium tamarense species complex are of the most abundant and widespread toxigenic species, and produces paralytic shellfish poisoning toxins as well as allelochemical substances.  This species complex consists of four to five species. The debate of the separation of this complex into real species in long on going and here a concept for the divorce of this group will be proposed.  Problems with identification of a toxic member of this species complex in November 2012, which led to the accidental export of toxic mussels to Japan, has now led to severe restrictions on Australian shellfish exports to Japan for a year, and resulting losses of many million $. Furthermore, population genetic insight and adaptive strategies in species interaction processes will be presented. Allelochemical mediated intra-population facilitation, may explain at least partly the high genotypic and phenotypic diversity of Alexandrium populations. Consequently, multiple traits within a population potentially allow mutual facilitation, and may promote the success of microbial planktonic populations.

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.

Event Date: 
Wednesday, October 26, 2011 - 18:00 - 18:15
Institution: 
Macquarie University
Title: 

Marine Synechococcus: genomics, genetics and ecology of a ubiquitous primary producer

Abstract: 

Although life in the oceans presents some of the most amazing and colourful spectacles, from whales to tropical reefs, the molecular age has led us to a deeper understanding of the diversity and activity of the microorganisms that have a profound influence on our climate. Up until the late 1970s the smallest and most abundant phytoplankton in the oceans had remained undiscovered. These organisms have since been characterised as Synechococcus and Prochlorococcus which are responsible for 2/3 of all marine CO2 fixation. For more than a decade we have been exploring the molecular ecology, physiology, and genomes of these prokaryotic primary producers. Molecular approaches have led to an understanding that genome diversity and plasticity underpin their global distribution and lead us to a pathway from genes, the fundamental units of selection, to a better understanding of the activity of microorganisms that drive geochemical cycles.

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