an extraordinary organism - massachusetts-rhode island...

Didymosphenia geminata …

an extraordinary organism

Cathy Kilroy NIWA, Christchurch, New Zealand International Didymo Conference

Providence, Rhode Island 12-13 March 2013

• First blooms 2004

• Almost immediately recognised as non-indigenous, invasive

• Intensive government-funded research in New Zealand http://www.biosecurity.govt.nz/pests/didymo

• As of 2004, at least 12 published

papers dedicated to didymo

• Average ~10 papers per y since 2008 (25% each NZ and USA)

The blooms in New Zealand put didymo on the world map

• NZ overview and update

• Didymo biology – cells vs. stalks

• A non-indigenous species in NZ?

• The role of phosphorus: research in NZ

• Explaining distributions: models and data

Topics

Talk outline






Topics

Lower Waiau River 15 October 2004

First point of Didymo infestation in NZ Mararoa River @ Kiwiburn Bridge Sometime pre-Oct 2004

Data from Didymo samples database: https://www.didymosamplesdb.org.nz/ MAP SOURCE: Kilroy C, Unwin M. 2011. Aquatic Invasions 6: 249-262.

https://www.didymosamplesdb.org.nz/�



sites surveyed in 2009, but didymo not found

rivers/lakes with didymo –

No didymo detected in

the North Island

NZ update (2012)

* *

2012

Dg in New Zealand

sites surveyed in 2009, but didymo not found

rivers/lakes with didymo –

rivers/lakes with known blooms

D. geminata blooms

2012

NZ update (2012)

Irrigation New Zealand Newsletter. June 2007

…but no major adverse effects to hydroelectric schemes in NZ

Meridian Energy fortnightly monitoring sites

…nor to hydro-canal salmon farms

Effects on: • periphyton communities • invertebrate communities Effects on fish still unclear

Lower Waiau River – pre-didymo, early 2004

Lower Waiau River 2012

Lower Waiau River

Waitaki River

Ohau River

Mararoa River

Opuha River Opuha River

Trial flushing flow, Opuha-Opihi River, 13 February 2013

Test to show if spill tackled didymo A good test that 'didn't quite go to plan' Last updated 05:00 14/02/2013 JOHN BISSET/Fairfax NZ WATER RELEASE: Opuha Water hopes yesterday’s controlled release from the dam will give it a better indication of how to solve water quality issues. The company behind the Opuha Dam said yesterday's release of water was an "interesting test", but is not sure whether it has solved the build-up of didymo. Yesterday, it had planned to release up to 40 cumecs, about four times the Opihi River's average flow, but Opuha Water chief executive Tony McCormick said it had only got up to 32 cumecs. "It didn't quite go to plan, but it was still a very good test of our systems," Mr McCormick said. "From a visual point of view, you can see the difference it made in the water colour, but we're waiting for the reports to see how truly effective it was." Opuha Water collaborated with Environment Canterbury and the National Institute of Water and Atmospheric Research (Niwa) on the controlled release. Recently there have been complaints about the level of didymo in the system just below the dam, while public health officials have advised people not to swim near the extensive toxic algal growths observed in the Opihi River. Mr McCormick acknowledged the release was not large enough to address the toxic algal growth, but hoped it would have cleared some of the didymo. "To really roll the rocks over, as it were, you need a proper flood of about 200 cumecs," he said. Mr McCormick said Niwa would assess the Opuha section of the river in a few days.

Trial flushing flow, Opuha-Opihi River, 13 February 2013

Removed up to 30% of biomass (measured as a visual index), but re-grew after 2 weeks.





• Explaining distribution: models and data

Topics

Didymosphenia geminata (Lyngbye) M. Schmidt

D. geminata : stalk formation

Stalk composition

Didymo stalks: composed of polysaccharides (Extracellular Polymeric Substances, EPS) “sulfated polysaccharides with significant uronic acid, and protein” (Gretz, 2008)

Processes in “bloom” formation

Attachment and stalk stained with Methylene Blue

Cell ̶ stalk attachment

Surface suitable for attachment

Didymo cell

D. geminata cells at the surface of the mat

D. geminata cells at the surface of the mat

~30 mm

Communities within the mat

Achnanthidium minutissimum attached to didymo stalk

Communities within the mat

Didymo mats harbour many other algal taxa

Cell size reduction in didymo

Vegetative cell division in diatoms: size restoration occurs though auxosporulation (sexual reproduction)

Cell size reduction in diatoms

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Cell size (arbitrary units)

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After 11 cell divisions, mean

size 6.5 units

After 2 cell divisions mean size 12 units

Start with a cell 12.5 units long, with 0.5 unit size reduction per division

Cell size reduction in diatoms

Cell size distribution: NZ populations

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Didymo cell lengths in samples collected from Lower Waiau River where blooms first observed






Topics

Didymo’s global distribution:

SOURCE: Whitton BA, Ellwood NTW, Kawecka B. 2009. Biology of the freshwater diatom Didymosphenia: a review. Hydrobiologia 630: 1-37.

The only record of didymo in NZ before 2004 … Mather, MW 1928. Freshwater Algae of the Hutt Valley. MSc Thesis held at Victoria University, Wellington.

D. geminata: a non-indigenous species in NZ?

It was almost recorded in a second stream …



Illustrations from: Hustedt, F. 1930. Die Susswasser-Flora Mitteleuropas. Heft. 10. Bacillariophyta (Diatomeae). Gustav Fischer.

Modern map

D. geminata: an invasive, non-indigenous species in NZ?

Could the stream be located today???

Lower Waiau River – surveys, including taxonomic analyses of periphyton samples since 1997 Many other collections, including from paleo studies.


Data from Didymo samples database: https://www.didymosamplesdb.org.nz/ MAP SOURCE: Kilroy C, Unwin M. 2011. Aquatic Invasions 6: 249-262.










Topics

Research in NZ: streamside channels

The river water supply was from this braid

mean DRP 1-2 ppb mean TDP 1-2 ppb mean NO3-N 4-15 ppb

Bothwell ML, Kilroy C. 2011. Phosphorus limitation of the freshwater benthic diatom Didymosphenia geminata determined by the frequency of dividing cells. Freshwater Biology 56: 565-578.

Research in NZ

Development of the FDC technique

Research in NZ

Channel experiments: Didymo cell division rates were limited by P in Waitaki River water

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Target added PO4-P (ppb)

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) Expt 2. Apr 09 Expt 3. Nov 09 ambient DRP 1 ppb NO3-N 4.5 ppb

ambient DRP 1 ppb NO3-N 7.6 ppb

Bothwell ML, Kilroy C. 2011. Freshwater Biology 56: 565-578.

Research in NZ

Channel experiments: Stalks grew longer when nutrient (P) concentrations were low

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Expt 2. Apr 09 Expt 3. Nov 09 ambient DRP 1 ppb NO3-N 4.5 ppb

ambient DRP 1 ppb NO3-N 7.6 ppb

Kilroy C, Bothwell M. 2011. Journal of Phycology 47: 981-989.

Title

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Channel experiments: combined results of three experiments: stalk length decreased as FDC increased

R2 = 0.74

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Frequency of dividing cells (%)

Research in NZ

Research in NZ

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Field surveys: we found higher cell division rates in didymo populations as mean DRP increased …

Kilroy C, Bothwell ML. 2012. Freshwater Biology 57: 641-653.

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Research in NZ

Standing crop index (% cover * thickness in mm)

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Survey of 31 South Island river sites, Jan-Feb 2011

2 mg m-3: Approx. limit for didymo blooms

… and no blooms when mean DRP greater than about 2 ppb

Selwyn River, Canterbury • Sporadic cover • Mean DRP = 2.5 ppb • Frequency of dividing cells >10%

Ohau River, Canterbury • Persistent blooms • Mean DRP = < 1 ppb • Frequency of dividing cells <2%

Research in NZ

Low P appears to promote stalk (EPS) production (blooms) in didymo.

N.B. Consistent with studies on EPS in estuarine/marine diatoms: General pattern of highest EPS production under P-limitation, when

photosynthetic rates are high (i.e., suitable light conditions)

For example: Myklestad & Haug 1972. J. Exp. Mar. Biol. Ecol. 9: 125-136; Myklestad 1995. Sci. Total Envir.: 155-164; Staats et al. 2000. Mar. Ecol. Prog. Ser. 193: 261-269; Alcoverro et al. 2000. J. Phycol . 36: 1087-1095.






Topics

2005 Estimate of didymo preferred habitat from current knowledge Best Worst

2008 Predictions of % cover, using survey data

>60% 25-60 10-25 1-10 0-1

Explaining distributions: models

Why hasn’t didymo been recorded in the North Island?

Explaining distributions: Long-term dataset

https://secure.niwa.co.nz/wqis/index.do National River

water quality monitoring network Monthly WQ at 77 sites since 1989

https://secure.niwa.co.nz/wqis/index.do�

https://secure.niwa.co.nz/wqis/index.do�

WQ sites. Area of circle indicates relative mean DRP concentration

Sites with visible D. geminata

Nationwide DRP

Data from the National River water quality monitoring network (NIWA). Monthly data, 2005-2011 Geometric mean of dissolved reactive P

Range of mean DRP 67.7 ppb (Tarawera @ Awakaponga) to 0.6 ppb (Monowai @ Gates) (shown with arrows)

Tarawera (d/s), Highest DRP

Monowai, Lowest DRP (no didymo)


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Buller @ Longford: persistent didymo blooms since October 2005

Running geometric means – 12 months

Explaining distributions: Long-term dataset m

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DRP

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2 ppb DRP: limit for prolific stalks?

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Hurunui at Mandamus: persistent blooms since April 2007

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Waitaki @ Kurow: persistent blooms since January 2006

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Clutha @ Luggate Bridge: persistent large blooms since September 2005

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These rivers were already perfect for didymo “blooms”

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Buller at Te Kuha: occasional low didymo cover since 2006,

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Hurunui @ SH1 bridge: occasional low didymo cover since November 2007


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Opihi @ Rockwood: didymo never observed at this site.


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Motueka @ Gorge: didymo never observed at this site


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Motueka at Woodstock: blooms in 2007, but not observed since then


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Oreti @ Lumsden: blooms in 2005-6, but not observed since then


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Negative surveys 2011, 2012 Why complete absence?

• Didymo is remarkable for massive biomass in rivers with extremely low nutrient levels: these “blooms” have persisted since 2004 in some South Island, New Zealand, rivers.

• Didymo is still considered a problem, and is still subject to management actions in NZ.

• Experiments and surveys indicate that the massive biomass is caused by low levels of available phosphorus.

• Long term DRP data consistent with blooms only occurring when mean DRP concentration is less than about 2 ppb – over time as well as space

• Some rivers with blooms have had continuous low DRP – perfect for didymo blooms – since 1990.

• This supports the belief that didymo was new in New Zealand around 2004. Expansion in the Northern Hemisphere had greatly increased the chances of it reaching NZ.

A quick summary ….

January 2013, South Island

Acknowledgements

Funding:

• New Zealand Foundation for Research Science and Technology (NIWA Capability Fund, and contract C01X0308) (now MBIE);

• NZ Fish & Game Ltd.,

• Department of Conservation,

• Meridian Energy Ltd.,

• Environment Canada,

• Ministry for Primary Industries.

Too many people to mention! NIWA, DOC, MPI, Fish & Game; landowners, supporters …

NRWQN: NIWA Water Quality Laboratory, Hamilton, NZ.

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