Wild Rice Studies in Minnesota
Rachel Walker  Barr Engineering
&
Edward Swain  Minnesota Pollution Control Agency
2013 Minnesota Wetlands Conference
January 30, 2013
Wild rice – natural history
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Two species in Minnesota – Zizania palustris and Zizania aquatica
Annual plant, germinates after spring thaw and matures in late August
Floating leaf stage in June – uses photosynthesis to make carbohydrates
needed for stalk/root development – vulnerable to fluctuations in water
level
Seeds ripen in late August/ early September, rice shatters and scatters in
water body or may be dispersed by wind/ herbivory/ humans
4-6 year boom/bust cycle with slow release of nutrients from decaying
straw
Potential effects on wild rice
populations in Minnesota
• Land use changes – late 1800s to present
-Very little peer – reviewed literature over multiple years
-Many gaps in understanding of factors that influence natural stand
populations
• Major state-wide changes (agriculture, development,
demographic changes)
-Changes to many key factors(annual and inter-annual): water levels,
wetlands (composition and distribution), sediments, herbivory, climate
Wild Rice Sulfate Standard
• Adopted in 1973 to protect wild
rice (natural and paddy-grown)
– 10 mg/L, applicable to water
used for production of wild rice
during periods when the rice may
be susceptible to damage by high
sulfate levels
• Three key elements:
– Where, What, When
John Moyle (MDNR)
found a correlation
between wild rice
waters and low sulfate
Moyle (1956) J Wildlife Management
Sulfate pattern
in lakes across
Minnesota
(Moyle 1956)
Moyle (1956) J Wildlife Management
Moyle’s sulfate
isopleths (red)
superimposed on
his western limit of
wild rice (green)
Moyle (1956) J Wildlife Management
General
distribution
of wild rice
in
Minnesota
Wild rice surveys requested by
MPCA – conducted by Barr Engineering
• Total number of clients for whom surveys have been
conducted – 10 surveys (1-4 years)
Wild rice locations, bed size, density (qualitative and quantitative
measures), plant biomass (in situ and ex situ), water quality, other habitat
characteristics
• Total shoreline surveyed for wild rice in northern MN
1600 miles over 4 years (~ 8 rivers, ~ 23 lakes, ~15 smaller
creeks)
• General observations
Begun in 2009 – some carried out 4 years
Wild rice stands grow under many sediment, water quality, habitat conditions
Sulfate levels range from a few ppm to hundreds of ppm in natural stands
Wild Rice Legislation (2011)
• Wild Rice Rulemaking and Research
(Laws of MN 2011, 1st Spec. Sess., Ch. 2, Art. 4,
Sect. 32(c))
• $1.5 million for wild rice standards study
• MPCA must create an advisory group
and develop a study protocol
Wild Rice Standards Study
• Goal: obtain information that will be
useful in evaluating Minnesota’s current
standard
• Any modification of the standard would
be based on multiple data sources,
including:
– Experimental/study results
– Field data
– Historical information
– Relevant scientific literature
Standard is for sulfate, but:
any effect on wild rice is probably indirect
• Sulfate is a relatively benign chemical
• But in wetland sediments, bacteria can
convert sulfate to hydrogen sulfide, which is
reactive.
• Hydrogen sulfide might be directly toxic to
plant roots, or wild rice might be affected by
other effects of sulfide production.
Possible sulfate interactions in wetland
sediments that might affect wild rice growth
Study Components
• Study protocol identified the following areas
of potential study:
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Hydroponic growth experiments, comparing
sulfate to sulfide
Sulfate additions to mesocosms (pots) with
lake sediment
Intensive field study of natural wild rice stands
Additional field surveys
Study Process
• Finalize study protocol
• RFP based on protocol
– Closed January 12, 2012
– Received 3 proposals (2 U of MN)
– Contracted with U of MN
Protocol--May 2011
(preliminary survey 2011)
RFP (Jan 2012)
• Work underway in spring 2012:
– Field survey by Amy Myrbo (Mpls)
– Hydroponic dose-response
experiments by John Pastor
(Duluth)
– Mesocosm experiments by Nate
Johnson (Duluth)
Studies
(2012-2013)
Standard ReEvaluation/Rulemaking
(start early 2014)
Study Process, cont.
• Periodic review of study results;
adjust approach as needed
– Mid-project review: 2/28-3/1, 2013
• Studies completed: Dec. 2013
• Rulemaking, as warranted
Stakeholder Meetings and
Communication Efforts
 Protocol development
 Tribal Consultation (March 2011)
 Individual Meetings with
• Minnesota Environmental Partnership
• Minnesota Cultivated Wild Rice Council
• Minnesota Chamber of Commerce
 May 9, 2011, Meeting of Technical Experts
 Wild Rice Standards Study Advisory Committee
 Rulemaking input
 Web page and e-mail GovDelivery list:
pca.state.mn.us/ktgh1083
2011 Preliminary Field Survey
• Survey of about 50 sites
– Led by Amy Myrbo, Limnological Research
Center, U of MN, with co-investigators:
• Nate Johnson, UM-Duluth
• Dan Engstrom, Science Museum of Minnesota
– August-September 2011
– Characterization of wild rice habitat:
• Surface water, sediment, porewater
• Associated plant species
2011
Sample
Sites
Use of a Rhizon®
artificial root to
obtain a sample of
porewater
Significant positive correlations
(2011 dataset)
 Sulfate
in surface water with: sediment AVS (acid
volatile sulfide)
 Porewater:
• sulfide, total nitrogen, and ammonia
• phosphorus and nitrogen
Significant negative correlations
(2011 dataset)
 Porewater
total nitrogen and ammonia with: wild
rice density
 Porewater:
sulfide and iron
In 2012, sites with no rice were sampled.
But where to core sediment?
• Rice can co-occur
with lily plants, so
field crews sampled
near lilies if they
couldn’t find rice.
2012 Wild Rice Study Task: Field Data
110 sites in 2012
Surface water
Na, K, Mg, Ca, Fe
SO4, Cl
Alkalinity, pH, conductivity, Total P, Total N,
Ammonia, Nitrate + Nitrite, transparency
Bulk Sediment Chemistry
Acid-Volatile Sulfide
Total carbon, phosphorus, nitrogen, sulfur
Phosphorus fractionation
Simultaneously-Extracted Metals:
Fe, Cu, Zn, Co, Ni, Mn, Mo, Se, As, B
Porewater
Other Sediment Properties
Water
organic matter
carbonate content
Organic grain size
Wild rice phytolith presence/absence
Sulfide
Na, K, Mg, Ca,
SO4, Cl
Total P, Total N, Silica
Ammonia, Nitrate + Nitrite
DOC (dissolved organic carbon)
Fe, Cu, Zn, Co, Ni, Mn, Mo, Se, As, B
Site selection
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Based on DNR data:
–
SO4
–
aquatic vegetation
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Lakes, rivers, paddies with wild rice
or suitable wild rice habitat
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Spread across state
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Range of SO4 values
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Coordinated with Red Lake, White
Earth, and Fond du Lac bands;
paddy owners, landowners, State
parks, State Wildlife Management
Areas
Sites sampled
2011 Preliminary Field Survey
2012 Field Survey
Professor John Pastor and his
experimental wild rice mesocosms
2012-2013 Wild Rice Study Task:
Hydroponic Experiments
No effect
Limiting nutrient
Growth
Relative to Control
Toxic
Nutrient/Toxic
Concentration in hydroponic growth medium
(Sulfate, sulfide, iron, copper, zinc….)
Examples of test chambers used for performing the germination tests, where many
seeds are incubated in each jar.
Post- germination test.
Post-germination test initiation with sprouting wild rice seed in a Kimax test tube.
Post-germination test showing final growth after approximately 10 days . This method
development test was performed to examine effects of different concentrations of growth
solutions (Hoagland’s solution).
Relationship of Wild Rice Study Tasks
Increased understanding of
the effect of elevated sulfate on wild rice
growth, to inform re-evaluation of the
current sulfate standard.
Exposure Assessment
(Porewater concentrations
in the field)
Low
Sulfate
No effect
Growth Relative
to Control
High
Sulfate
Toxicity Assessment
(Hydroponic Experiments)
Limiting nutrient
Toxic
Nutrient/Toxic
Concentration in hydroponic growth medium
(Sulfate, sulfide, iron, copper, zinc….)
(range observed in porewater)
Sulfate Additions to Mesocosms
(sulfate gradually penetrates
sediment where it can be
converted to sulfide)
• Observe time-course of
sulfate penetration.
• Measure sulfide
concentrations.
• Observe production of metal
sulfides.
• Compare effect of different
temperatures.
• Effect of elevated sulfate on
wild rice growth.
Thank You!
Questions?