Fisheries

Event Date: 
Wednesday, February 25, 2015 - 18:00 - 18:30
Institution: 
San Diego State University
Title: 

Integrating microbial community dynamics into kelp forest ecosystem models

Abstract: 

Metagenomics has enabled a greater understanding of microbial community dynamics than previously realized and now the challenge is to integrate microbial dynamics into ecological models. My lab takes an ‘omics approach mixed with classical microbiology to identify factors affecting microbial communities and how an altered microbial community will affect macro-organism health and ecosystem functioning. The key habitats are coral reefs and kelp forests. Within the kelp forest, we have started with a culturing approach that has identified novel genomes associated with the giant kelp Macrocystis pyrifera. Phenotypic assessments of these bacteria have identified increase in the microbe’s ability to tolerate copper and resist antibiotics with increasing human activities. We have tested the effects of altered microbial abundance and community composition on survival and development of M. pyrifera gametophytes. Decreasing microbial abundance enhanced M. pyrifera recruitment, increasing zoospore settlement and gametophyte development. Gametophytes reared in microbial communities sampled adjacent to the populated city showed lower survival and growth compared to gametophytes in microbial communities from a remote island. Metagenomics revealed a high abundance of phototrophic and oligotrophic microbes from the island, compared with an abundance of eutrophic microbes adjacent to the city. In addition, microbes adjacent to the city lacked genes that produce quorum signaling molecules, negatively influencing kelp spore settlement. Long term analyses of the microbial communities from the kelp forest have been initiated and we are currently investigating the microbes associated with the water column and kelp surface at two distinct depth. First, at 0.5 m depth where the water is warmer, highly oxygenated and receiving large amounts of carbon from photosynthesis and second, at 15 m depth where the water is under seasonal thermocline, colder, lower in oxygen, and can potentially be exposed to high partial pressure of carbon dioxide. Monthly sampling has revealed microbial number is lower at depth and pCO2 is higher. Metagenomic analysis of these samples is under way. Kelp feeds the ecosystem through degradation and we are currently investigating the effects of microbes on kelp degradation and subsequent nutritional value. We have shown altered microbial communities are detrimental to kelp recruitment and are identifying way of adding these data to ecosystem models.

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 - 19:15 - 20:00
Institution: 
University of Queensland
Title: 

Sizing up the symbiotic partnership: towards a single-cell view of nutrients uptake in cnidaria-dinoflagellate symbiosis

Abstract: 

Reefs based on scleractinian corals are among the most productive and biologically diverse ecosystems on Earth. At the heart of their success as the architects of coral reefs, is their symbiosis with dinoflagellate algae, which live within their tissues and provide corals with an enlarged metabolic repertoire. Thus corals are ‘polytrophic’, being able to acquire carbon-based nutrients from sunlight through their algal symbionts (‘autotrophic’), feeding on plankton (‘heterotrophic’), and absorbing dissolved nutrients from the surrounding water. These strategies increase the nutritional options of corals in an environment where planktonic food supplies and dissolved nutrients in seawater may be episodic.

The intertwined nature of coral-dinoflagellate endosymbiosis has made the relative quantification of host and symbiont contributions to metabolic activities extremely difficult so far. Consequently, whilst we now recognize the threats of human activity, future climate change and associated symptoms of stress on the reef, very little is known about the nutritional function of the cnidarian-dinoflagellate symbiosis that underpins and maintains reef health.

In this talk, I will explore how the development of new technologies combining isotopic labeling and high resolution imaging analysis opens a new interdisciplinary frontier in the study of such symbiotic interactions with direct implications for how these organisms will respond to environmental changes.

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