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 • • • • • 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: – – – – 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 • Based on DNR data: – SO4 – aquatic vegetation • Lakes, rivers, paddies with wild rice or suitable wild rice habitat • Spread across state • Range of SO4 values • 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?