Update on Didymo research

Philippe Gerbeaux, Technical Advisor (Freshwater)(Prepared for MPI Freshwater Pest Partnership

meeting Wellington (13 May 2013)

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Outline

• Outcome of Didymo conference (Providence, March 2013)

• Outcome of science providers meetings

• Future priorities

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New Zealand represented by a strong delegation :Cathy Kilroy (NIWA)

Jeannie Kuhacek (Cawthron Institute)Craig Cary (video)John Sanson (MPI)

Philippe Gerbeaux (DOC)International collaborators (M. Bothwell, P. Zarnetske)

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An opportunity to show case NZ’s collaborative spirit and resulting successes

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Some potentially key results were presented by Cathy Kilroy …

• Didymo proliferations occur because of low phosphorus levels rather than in spite of low P (2ppt?)

• Some convincing examples were presented by Cathy (eg Southland)

• Elevated P linked to absence

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…and Max Bothwell

• Increased extracellular polysaccharide stalk production under P starvation provides a possible mechanism for bloom formation

• There are known mechanisms reducing P concentrations in rivers

• Atmospheric N deposition can lead to P deficiency in pristine waters

• So can direct anthropogenic enrichment with nitrogen of agricultural landscapes

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Other highlights from a NZ perspective

• Other presentations related to the NZ work (Jeannie, Phoebe, Craig)

• Many of the conference attendees were impressed by what we have achieved:

- collaborative (national and international) research

- coordinated national programme - a strong Check Clean Dry brand presence, and - the strength of our relationships

• The moment Jeannie stood up to let the attendees know about the recent success with the cultures (following a comment that a US scientist was going to have a crack at getting clean cells through doing….. what Cawthron had already done!).

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There were a number of other interesting presentations from the US and others too!

• Michael Gretz (on stalk structure, development and degradation)

• Brad Taylor (on the negative impacts of blooms on salmonids)

• Sarah Spalding (on the existence of blooms as long as 10,000 ys ago)

• Vivian Montecino ( from Chile - on niche requirements and potential habitats)

• Check book of abstracts and soon the special issue of Diatom Research Journal

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Research meetings

• 2 meetings with science providers (NIWA and Cawthron)

• 15/01/2013 at the Cawthron Institute in Nelson

• 20/02/2013 by phone conference

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Current results and linkages

• Ohau river work: Cathy has been doing trials to see the influence of slow release of P on blooms and whether  future trials are viable.

• The results from the culturing experiments are very interesting and exciting, especially in relation to stalk attachment and the ability to do some fundamental controlled testing of things such as temperature and UV effects on growth, as well as nutrients.

•  If there is potential to have a joined up approach between lab and field experiments, it seems that this would be very beneficial (whether occurring concurrently or in series).

• The conference (and side talks as well) gave us a better picture of where the linkages and gaps are, i.e. Craig Cary’s population genetics research looking at the question of a single introduction or multiple introductions.

• Some work is being done by Phil Novis at Landcare Research

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Options for future research

• Investment in optimising the synthetic media to continue manipulations of didymo growth and attachment;

• Traditional algal studies in the lab– such as the effect of temperature and UV;

• The effect of phosphorus and nitrogen, as well as the effects of calcium and magnesium for stalk production;

• Further development of the biofilm work; • Distribution; • Temperature variability either through long term

temperature/seasonal pattern study using datasets from National water quality monitoring, and/or lab studies;

• Research into Cathy, Max and Cawthron stalk-attachment theories – field and lab;

• Flow manipulation; • Long term viability of the population dependent on sexual

reproduction and its triggers; • Environmental changes that may have assisted the invasion of

didymo.

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Future priorities

• Our priorities are for research that will help focus our management in a cost effective manner. We want to fill the management gaps and target our actions based on sound science. As mentioned in the teleconference, understanding what conditions are most favourable for didymo establishment and/or growth will help guide our management decisions.