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

on m

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

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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.