Scientists discover tiny new species on Outer Island

Diatom

You’ll never see it without a microscope but a newly-documented species calls Outer Island home. And it’s named for a retired water quality specialist from the Great Lakes Inventory and Monitoring Network division of the National Park Service.

We’re talking about a microscopic species of algae, Semiorbis eliasiae, named after Joan Elias, of the Great Lakes Network. These diatoms have ornate cell walls made of opaline silica, or biologically-produced glass. When the diatoms die, these skeleton-like fragments settle to the bottom of shallow lagoons, including a lagoon on Outer Island, in the Apostle Islands National Lakeshore.

Diatom
Live diatom colony – images courtesy Mark Edlund, St. Croix Watershed Research Station

Aquatic biology scientist Mark Edlund at the St. Croix Watershed Research Station identified the new diatoms, found in a sediment core collected in 2007 from the Outer Island lagoon. 

Joan Elias, for whom the diatoms are named, later collected live samples from the lagoon in 2011. That’s according to a scientific journal article documenting the discovery, published in March of this year.

To determine that this is indeed a new species, scientists compared the diatoms discovered on Outer Island with other diatoms found in Florida, New Jersey, Norway and Canada.

In the NPS newsletter, The Current, Edlund said, “The genus Semiorbis is really uncommon. I’ve been collecting diatoms since 1987 and have only found it twice. Outer Island is one of those places.”

Outer Island – Jeff Rennicke photo

A core sample taken from Outer Island indicates that Semiorbis eliasiae lived in the lagoon as early as the 1950s. The future of these rare diatoms is uncertain, given the ever-changing size and shape of the lagoon and Lake Superior’s impact on it. A large storm opened the lagoon to the lake in September of 2014. By July of 2020, a smaller lagoon was re-isolated from the lake as the sand barrier reformed. As of May, 2021 there are two lagoons cut off from the lake.

Lagoon on the southwest end of Outer Island- Google Map image

The pandemic stopped diatom sampling in 2020. Scientists expect to resume collecting them this summer.

Samples of Semiorbis eliasiae are permanently preserved in diatom collections at the Science Museum of Minnesota, the Academy of Natural Sciences in Philadelphia and the Canadian Museum of Nature.

You can read the scientific journal article documenting the discovery here.

Why it matters

Different algae species need different conditions of temperature, light, water acidity and oxygen levels to thrive and survive. Sediment samples taken from lakes and rivers can reveal how those populations have changed over hundreds of years. Scientists believe that knowing how these diatoms responded to environmental changes in the past may help them to predict how lakes will respond to future climate changes.