New findings on new invadersThe latest on starry stonewort spread
and hybrid watermilfoil behavior
Dan Larkin & Wes GlissonSeptember 12, 2018
Photo: Dave Hansen
Starry stonewort (Nitellopsis obtusa)
• Green macroalga• Native to Eur. & Asia• Rare species in native
range• First found in North
America in 1974• Minnesota in 2015
(Karol & Sleith 2017, Larkin et al. 2018)
Photo: Scott Brown
Invasion history
Larkin et al. 2018
Current known distribution
Larkin et al. 2018
Robin Sleith
Our research and extensionSpread
Where’s it going to end up?
ImpactsWhat’s it going to do when it
gets there?
ManagementHow can we support rapid and
effective responses?
ThreatCarli WagnerPoster: Seasonal growth, impacts
Megan Weber1:15: AIS Detectors & Starry Trek
Rafael Contreras-RangelPoster: algaecide trials
Nick Phelps11:15: AIS risk for MN lakes
Where’s it going to end up?Where can it survive in
the world?CLIMATE
Which lakes provide suitable habitat? WATER CHEMISTRY
Which lakes can it get to? BOATER MOVEMENT +
DESICCATION TOLERANCE
Potential distribution based on climate
Escobar et al. 2016. Scientific Reports Nick Phelps Luis Escobar
Potential distribution based on climate
Escobar et al. 2016. Scientific Reports Nick Phelps Luis Escobar
Potential distribution based on climate
Escobar et al. 2016. Scientific Reports Nick Phelps Luis Escobar
• High potential for spread based on climate• But need to incorporate habitat suitability• Need lake-level predictions
Scaling down to lake level
Chemistry of SSW lakes• High pH• High conductivity (Ca, Mg)
• Wide trophic-state ranges (N, P)
Based on data from NY (Sleith) and Europe (Boissezon et al.)
Dr. Ranjan Muthukrishnan (Postdoc)
Scaling down to lake level
What lakes is it found in now?
What are environmental conditions of these lakes?
Which MN & WI lakes overlap with these conditions?
Chemistry of SSW lakes• High pH• High conductivity (Ca, Mg)
• Wide trophic-state ranges (N, P)
Based on data from NY (Sleith) and Europe (Boissezon et al.)
Regional risk map
Low risk High risk
Regional risk map
Low risk High risk
Consensus high risk
Overland transport
Where to?• Boater movement
Nick Phelps Grand
CassTurtle
Upper Red
WinnibigoshishMoose
Rice
Sylvia
MinnewaskaKoronis/Mud
Wolf
PleasantMedicine
Overland transport
Can it survive?• Desiccation tolerance
Photo: NYS DEC
Desiccation experiments
Bulbils and clumps• Single fragments• Small clumps• Large clumps
Wes Glisson (Research Fellow)
Desiccation experiments
Treatments• Out of water for 15
mins. to 5 days• Negative controls
(wet, never dried)• Positive controls
(dried to constant mass)
Desiccation experiments
Returned to water, viability tested by:• Sprouting (bulbils)• Rehydration
(fragments)
Desiccation experiments
• Bulbils viable for ~4 hours
Desiccation experiments
• Fragments/clumps viable for ~2 – 72 hours • Strong size effect
0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4Time (h)
Pro
porti
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ass
lost
Fragments
Desiccation experiments
• Fragments/clumps viable for ~2 – 72 hours • Strong size effect
0
0.2
0.4
0.6
0.8
1.0
0 2 4 6 12 24 48Time (h)
Pro
porti
on m
ass
lost
Small clumps
Desiccation experiments
• Fragments/clumps viable for ~2 – 72 hours • Strong size effect
0
0.2
0.4
0.6
0.8
1.0
0 6 12 24 48 72 120Time (h)
Pro
porti
on m
ass
lost
Large clumps
Implications for spread
• Reasonable effort will prevent spread
Photo: CA DFW
Zebra mussel veliger
Implications for spread
• Reasonable effort will prevent spread
• Risk is from non-compliance
Photo: NYS DEC
Implications for spread
• Reasonable effort will prevent spread
• Risk is from non-compliance
• And conditions that retain moisture
Photo: Blaine Barkley
Photo: Megan Weber
Get involved• Learn how to ID starry stonewort and other AIS• Participate in Starry Trek (August)• Enroll in AIS Detectors (spring)
Help in the field and lab• Noah Berg• Rafael Contreras-Rangel• Carolyn Kalinoswki
• Ranjan Muthukrishnan• Mike Verhoeven• Carli Wagner
References for spread risk• Escobar, L. E., H. Qiao, N. B. D. Phelps, C. K. Wagner, and D. J. Larkin. 2016. Realized
niche shift associated with the Eurasian charophyte Nitellopsis obtusa becoming invasive in North America. Scientific Reports 6:29037. DOI: 10.1038/srep29037
• Romero-Alvarez, D., L. E. Escobar, S. Varela, D. J. Larkin, and N. B. D. Phelps. 2017. Forecasting distributions of an aquatic invasive species (Nitellopsis obtusa) under future climate scenarios. PLoS ONE 12(7): e0180930.
• Larkin, D. J., A. K. Monfils, A. Boissezon, R. S. Sleith, P. M. Skawinski, C. H. Welling, B. Cahill, and K. G. Karol. 2018. Biology, ecology, and management of starry stonewort (Nitellopsis obtusa; Characeae): A Red-listed Eurasian green alga invasive in North America. Aquatic Botany 148:15–24.
• Muthukrishnan, R., R. S Sleith, K. G. Karol, and D. J. Larkin. 2018. Prediction of starry stonewort (Nitellopsis obtusa) invasion risk in upper Midwest lakes using ecological niche models. Aquatic Botany 151:43–50.
• Escobar, L. E., D. Romero-Alvarez, D. J. Larkin, and N. B. D. Phelps. In press. A note on lake connectivity to inform Nitellopsis obtusa spread in Minnesota. Journal of Oceanology and Limnology.