an extraordinary organism - massachusetts-rhode island...
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Didymosphenia geminata …
an extraordinary organism
Cathy Kilroy NIWA, Christchurch, New Zealand International Didymo Conference
Providence, Rhode Island 12-13 March 2013
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• 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
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• 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
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• 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
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Lower Waiau River 15 October 2004
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First point of Didymo infestation in NZ Mararoa River @ Kiwiburn Bridge Sometime pre-Oct 2004
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Data from Didymo samples database: https://www.didymosamplesdb.org.nz/ MAP SOURCE: Kilroy C, Unwin M. 2011. Aquatic Invasions 6: 249-262.
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sites surveyed in 2009, but didymo not found
rivers/lakes with didymo –
No didymo detected in
the North Island
NZ update (2012)
* *
2012
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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)
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Irrigation New Zealand Newsletter. June 2007
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…but no major adverse effects to hydroelectric schemes in NZ
Meridian Energy fortnightly monitoring sites
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…nor to hydro-canal salmon farms
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Effects on: • periphyton communities • invertebrate communities Effects on fish still unclear
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Lower Waiau River – pre-didymo, early 2004
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Lower Waiau River 2012
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Lower Waiau River
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Waitaki River
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Ohau River
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Mararoa River
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Opuha River Opuha River
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2009
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Trial flushing flow, Opuha-Opihi River, 13 February 2013
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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.
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• NZ overview and update
• Didymo biology – cells vs. stalks
• A non-indigenous species in NZ?
• The role of phosphorus: research in NZ
• Explaining distribution: models and data
Topics
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Didymosphenia geminata (Lyngbye) M. Schmidt
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Didymosphenia geminata (Lyngbye) M. Schmidt
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Didymosphenia geminata (Lyngbye) M. Schmidt
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D. geminata : stalk formation
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Stalk composition
Didymo stalks: composed of polysaccharides (Extracellular Polymeric Substances, EPS) “sulfated polysaccharides with significant uronic acid, and protein” (Gretz, 2008)
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Processes in “bloom” formation
Attachment and stalk stained with Methylene Blue
Cell ̶ stalk attachment
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Surface suitable for attachment
Didymo cell
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D. geminata cells at the surface of the mat
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D. geminata cells at the surface of the mat
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D. geminata cells at the surface of the mat
~30 mm
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Communities within the mat
Achnanthidium minutissimum attached to didymo stalk
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Communities within the mat
Didymo mats harbour many other algal taxa
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Cell size reduction in didymo
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Vegetative cell division in diatoms: size restoration occurs though auxosporulation (sexual reproduction)
Cell size reduction in diatoms
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0
50
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1 2 3 4 5 6 7 8 9 10 11 12
Cell size (arbitrary units)
Coun
t of c
ells
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
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Cell size distribution: NZ populations
80 90 100 110 120 130 140 150 160LENGTH
0.0
0.2
0.4
0.6
0.8
1.0
Proportion per Bar
0
10
20
30
40
Coun
t
oct_04
80 90 100 110 120 130 140 150 160LENGTH
0.0
0.1
0.2
0.3
0.4
Proportion per Bar
0
10
20
30
40
Coun
t
april_05
Didymo cell lengths in samples collected from Lower Waiau River where blooms first observed
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• NZ overview and update
• Didymo biology – cells vs. stalks
• A non-indigenous species in NZ?
• The role of phosphorus: research in NZ
• Explaining distribution: models and data
Topics
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Didymo’s global distribution:
SOURCE: Whitton BA, Ellwood NTW, Kawecka B. 2009. Biology of the freshwater diatom Didymosphenia: a review. Hydrobiologia 630: 1-37.
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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?
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It was almost recorded in a second stream …
D. geminata: a non-indigenous species in NZ?
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D. geminata: a non-indigenous species in NZ?
Illustrations from: Hustedt, F. 1930. Die Susswasser-Flora Mitteleuropas. Heft. 10. Bacillariophyta (Diatomeae). Gustav Fischer.
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D. geminata: a non-indigenous species in NZ?
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Modern map
D. geminata: an invasive, non-indigenous species in NZ?
Could the stream be located today???
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Lower Waiau River – surveys, including taxonomic analyses of periphyton samples since 1997 Many other collections, including from paleo studies.
D. geminata: a non-indigenous species in NZ?
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Data from Didymo samples database: https://www.didymosamplesdb.org.nz/ MAP SOURCE: Kilroy C, Unwin M. 2011. Aquatic Invasions 6: 249-262.
D. geminata: a non-indigenous species in NZ?
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• NZ overview and update
• Didymo biology – cells vs. stalks
• A non-indigenous species in NZ?
• The role of phosphorus: research in NZ
• Explaining distribution: models and data
Topics
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Research in NZ: streamside channels
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The river water supply was from this braid
mean DRP 1-2 ppb mean TDP 1-2 ppb mean NO3-N 4-15 ppb
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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
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Research in NZ
Channel experiments: Didymo cell division rates were limited by P in Waitaki River water
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ambient DRP 1 ppb NO3-N 7.6 ppb
Bothwell ML, Kilroy C. 2011. Freshwater Biology 56: 565-578.
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Research in NZ
Channel experiments: Stalks grew longer when nutrient (P) concentrations were low
0 5 500
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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.
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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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Research in NZ
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Research in NZ
1 100
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lls (%
) R2 = 0.54
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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-3)
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
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Selwyn River, Canterbury • Sporadic cover • Mean DRP = 2.5 ppb • Frequency of dividing cells >10%
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Ohau River, Canterbury • Persistent blooms • Mean DRP = < 1 ppb • Frequency of dividing cells <2%
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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.
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• 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
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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
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Why hasn’t didymo been recorded in the North Island?
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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
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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)
Explaining distributions: Long-term dataset
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Buller @ Longford: persistent didymo blooms since October 2005
Running geometric means – 12 months
Explaining distributions: Long-term dataset m
ean
DRP
(ppb
)
2 ppb DRP: limit for prolific stalks?
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Hurunui at Mandamus: persistent blooms since April 2007
mea
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pb)
Explaining distributions: Long-term dataset
2 ppb DRP: limit for prolific stalks?
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Waitaki @ Kurow: persistent blooms since January 2006
mea
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Explaining distributions: Long-term dataset
2 ppb DRP: limit for prolific stalks?
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Clutha @ Luggate Bridge: persistent large blooms since September 2005
mea
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2 ppb DRP: limit for prolific stalks?
Explaining distributions: Long-term dataset
These rivers were already perfect for didymo “blooms”
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Buller at Te Kuha: occasional low didymo cover since 2006,
mea
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Explaining distributions: Long-term dataset
2 ppb DRP: limit for prolific stalks?
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Hurunui @ SH1 bridge: occasional low didymo cover since November 2007
Explaining distributions: Long-term dataset m
ean
DRP
(ppb
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2 ppb DRP: limit for prolific stalks?
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Opihi @ Rockwood: didymo never observed at this site.
Explaining distributions: Long-term dataset m
ean
DRP
(ppb
)
2 ppb DRP: limit for prolific stalks?
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Motueka @ Gorge: didymo never observed at this site
Explaining distributions: Long-term dataset m
ean
DRP
(ppb
)
2 ppb DRP: limit for prolific stalks?
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Motueka at Woodstock: blooms in 2007, but not observed since then
Explaining distributions: Long-term dataset m
ean
DRP
(ppb
)
2 ppb DRP: limit for prolific stalks?
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Oreti @ Lumsden: blooms in 2005-6, but not observed since then
Explaining distributions: Long-term dataset m
ean
DRP
(ppb
)
2 ppb DRP: limit for prolific stalks?
Negative surveys 2011, 2012 Why complete absence?
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• 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 ….
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January 2013, South Island
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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.