Fig. 1 Starry stonewort with bulbil (asexual reproductive structure). Algal biomass and bulbils were monitored for this study.

Fig. 2 AIS Detectors sorting biomass samples and looking for bulbils. Rake used to collect spun-rake biomass also pictured.

Fig. 3 Starry stonewort under the ice. Not all biomass died back after the growing season (Fig. 4) and some remained green during the winter.

Why study phenology? Phenology can inform management and early detection strategies.

Moose

Koronis

• Lake Koronis (Stearns Co.)• Moose Lake (Beltrami Co.)

Where, When, What

• May 2017 – Sept 2018 on Koronis.• March 2018 – Sept 2018 on Moose.• Sampled most frequently (~monthly) during

summer and 1-2 times in the winter.

We revisited 5 locations in each lake and measured:• Biomass using the spun-rake method (Fig. 2;3)

* weight taken after removing excess water.

• Bulbil counts* counted on spun-rake vegetation in year 1 and

via sediment cores in year 2.

• 3-4 replicate samples taken per location.

New phenology insights – a year in the life of starry stonewort (Nitellopsis obtusa)

Results

Fig. 4 Patterns of starry stonewort abundance in Koronis and Moose Lake. Koronis was sampled for consecutive years and Moose was added this year. Each data point shows the average biomass across all five sampled locations per lake at each time point. Error bars show standard error of sample average.

Fig. 5 Patterns of starry stonewort bulbil production in Koronis and Moose Lake. Same legend as Fig. 4. Note: methods changed from 2017 to ‘18. Error bars show standard errors.

• Growing season is ~ late June - October.

• Maximum average biomass and bulbils occurred during September in both years and lakes.

• Phenology in both lakes fairly consistent, despite differences in latitude.

• Late spring/early summer management may be able to pre-empt high biomass and bulbil production.

• Biomass present year-round, but detectability of new populations likely highest in late summer.

Carli Wagner, Wesley Glisson & Daniel Larkin

Starry stonewort has been known in MN since 2015, but much of its biology and ecology is still unknown.

So what is this invasive alga up to in Minnesota lakes?

To investigate this, we tracked its annual growth and reproduction patterns – otherwise known as phenology.

Our research is the first to document trends in starry stonewort biomass and bulbil production – two metrics important to population maintenance/spread.

Research Gist