The Starry Stonewort Collaborative

Starry stonewort (SSW) is a macroalgae from the family Characeae that closely resembles a vascular plant. It originated in Eurasia, where it is considered to be an endangered, beneficial species. Although we can't determine an exact date for when it came to North America, the oldest record of it on the continent is dated back to 1974, suggesting it arrived around that time. It invades lakes, ponds, and slow moving water bodies where it attaches to the sediment and grows up to 2 meters in length (Larkin et al. 2018).

SSW's body is comprised of a chain of nodes and internodal segments, which functions as its stem. Whorls of 5-7 branchlets extend from each node, with bract cells growing off of branchlets, giving them a forked appearance. These branchlets are also longer than SSW's native look-a-likes, giving it a wider appearance.

Color varies depending on the time of year, starting as a bright green and changing to a greenish-brown as the season progresses.

SSW has both male and female individuals. As such, they produce unique reproductive organs, dependent on the individual's sex, at branchlet nodes. For males, this means orange antheridia, while for females it means bright red to light green oogonia. However, only males have been found in North America thus far.

In the invaded range, SSW reproduces asexually from fragments of the macrophyte or bulbils produced beneath the sediment. Since fragments and bulbils can be rather small, this allows SSW to spread and reproduce easily.

In order to anchor themselves to the sediment, SSW uses clear, root-like rhizoids. From the nodes of these rhizoids, white, star-shaped bulbils are produced. It is from these bulbils that the name "starry" stonewort is derived.

The star-shaped bulbils are also a distinguishing trait, as no native macroalgae has them. Additionally, SSW lacks the smell of similar looking macroalgae from the family Characae, also known as muskgrasses.

In its native range, SSW has actually been known to have a few positive effects. For example, it has been known to provide habitat, shelter, and food for animals, such as the red-crested pochard which preferentially grazes on it. In addition, some research suggests that SSW can increase water quality by acting as phosphorus sink, increasing the competition for the nutrient and limiting the amount that other species would otherwise get. Other research describes how SSW can increase water clarity by slowing down water movement and decreasing sediment suspension. The effect of SSW on native habitats is large enough that, in some cases, the return of dense mats of charophytes, including SSW, has proved to be the critical element in restoring waterbodies to clear water states.

However, in the invaded range these positive attributes are replaced by negative ones. First, while dense mats of SSW may be beneficial in the native range, studies indicate that they crowd and outcompete the native plants in the invaded range. Able to consume more nutrients and light, SSW kills and forces out the other plants, reducing biodiversity. Additionally, research suggests animals are also being pushed out by the invading plant. Due to the loss of familiar native plants, most fish are unable to find refuge or places to breed.

The macroalgae also has a negative effect on recreational activities. In addition to forming dense mats that cover the bottom of waterbodies, SSW fills the water column vertically. As a result, it pushes out swimmers and boaters by clogging up the spaces they would normally use.

Thankfully, SSW is not without control options. Research suggests that several strategies appear to be effective at reducing plant biomass, including physical and chemical methods. On the physical side, options include diver assisted suction harvesting, mechanical harvesters, and physical barriers like benthic mats. For chemicals, herbicide and algaecides have been demonstrated with good effect, specifically those that use endothall, flumioxazin, or chelated copper.

But, all of these treatments are in their infancy for being tested against SSW and, while research indicates that all may reduce biomass, there have been some mixed results and none have been shown to eradicate the problem with ease. Most methods only take care of the biomass above the sediment, allowing the bulbils to remain and germinate afterwards, repopulating the area. As a result, these have been colloquially referred to as "haircut" treatments.

Only the physical removal methods, specifically hand pulling or diver assisted harvesting, address the bulbils and therefore have the potential to eliminate the infestation. Mechanical harvesters only remove the biomass above the sediment. However, for even the manual options to be completely effective, they must be painstakingly executed in order to ensure that no bulbils are left behind, lest the problem return after the treatment ends. Other possibly effective treatments include water drawdowns and benthic mats, but these need more testing.

The most effective method though, is prevention. Like any invasive species, SSW is easier and cheaper to prevent rather than control. While removing the macrophyte involves multiple rounds of treatments and may not completely solve the problem, preventive measures, as cheap and simple as making sure no bits of it are attached to boat trailers, can stop SSW before it ever becomes established. The is especially effective due to the fact that SSW is primarily spread by humans, not animals. The macroalgae has been highly correlated to human activity, most frequently being found at close to boat launches and marinas. Network analysis of boat movements also shows a link between boat travel between lakes and the spread of SSW. As such, any reduction in human transportation of SSW will greatly reduce movement of this invader. Therefore, prevention is an invaluable and highly effective tool for stopping SSW in its tracks.

Prior to the creation of the Starry Stonewort Collaborative, not much focus had been placed on the eponymous macroalgae. Although some experts had taken notice and have been studying it for over a decade, it was not under the intense public scrutiny that other invaders, such as zebra mussels, had received. A review of scientific literature found that as of early 2018, only 12 papers examined SSW as an invasive species, 8 of which occurred after 2014. Concerned, the Finger Lakes Institute applied for and received a grant in 2017 to create the Collaborative. By bringing together and increasing the capacity of experts, resource managers and citizen scientists to manage starry stonewort across the Great Lakes basin, we hoped we would be able to more effectively research, monitor, and control the invasive species.

After its founding, the Collaborative established three main areas of focus:

• Ecology – sharing of ongoing field work and laboratory research and analysis for better understanding of Nitellopsis obtusa characteristics and life cycles
• Outreach – providing insights into the best outreach and education strategies for community involvement in Starry Stonewort identification and reporting
• Control – assisting in gathering and sharing best management practices and techniques from all areas of the Great Lakes basin

With these areas of focus in minds, we then established our goals:

• To establish extensive community-level volunteer engagement and training across the basin. By having more people involved in the efforts to monitor and control the spread of SSW, these endeavors become easier thanks to increased information collection and an increase in man-power.
• Basin-wide sharing of information and experiences in the control of SSW. Through this, efforts can be more productive by ensuring everyone has the best information available and by preventing retreading of ideas when unnecessary.
• The creation and sharing of best management practices and fact sheets describing SSW throughout the region. Similar to the previous goal, this allows people to be more informed in their efforts to fight SSW.
• The implementation of prevention strategies and rapid assessment and response plans. These reduce the likelihood of SSW invading a water body and allow for faster action if it does.

In order to accomplish these, the Collaborative first established a network of more than 20 collaborators from around the Great Lakes Basin, including scientists, stakeholders, and resource managers. These would serve as the eyes and ears of the Collaborative, providing local perspectives and resources while assisting with efforts for outreach, resource exchanges, and training. In addition, an expert panel of 8 knowledgeable people, some of which had studied SSW for more than a decade, was established to help guide the project, assist with the peer review of papers, overview best management practices, aid with outreach, and conduct informational webinars. The Collaborative is managed and coordinated through the staff at the Finger Lakes Institute, who also provide funding and resources of their own.

The most important part of the Collaborative, however, is the Citizen Scientists. The largest piece of the organization, these represent everyday citizens who want to make a difference both to their community and scientific research. These volunteers form the foundation that allows the Collaborative to accomplish its goals. Without their efforts, we would not be able to have the reach nor the manpower needed to be effective.

As such, the Collaborative is best represented conceptually by an upside down pyramid. It represents the numbers of people that are engaged in the project at each level, but also the importance of the top level and largest group, the Citizen Scientists.

The Starry Stonewort Collaborative works towards accomplishing its goals through several methods. First, we use the expert panel and other team members to help conduct and guide research efforts. By coordinating, they can ensure that they aren't wasting resources by overlapping study topics. In addition, the sharing of research, made simple through the use of a library on the Collaborative's website, allows members to conduct more informed research, inspiring new ideas and allowing for more robust experiments. On top of that, by sharing and examining previous work, they can determine which aspects of SSW require the most research and which already have a general consensus.

Second, members of the Collaborative go out and sample for SSW. Whether it be on a boat, in a kayak, or from the shore, members hunt for SSW to help increase our knowledge on the spread of the invasive species thus far. Through both longer term surveys that may examine the extent throughout a whole lake or more exploratory probes to determine if SSW has entered the area yet, members take it on themselves to get actively involved in the process.

Third, the Collaborative works to inform the public through several outreach efforts. For example, members regularly attend relevant public events such as boating and outdoor recreation conferences. While there, we can communicate with those who are most likely to be affected by SSW, providing them with reference material for facts and identification and explaining the danger of the invasive species. Another outreach method is with boat launch stewards. By monitoring launches, stewards are brought into direct contact with the people potentially spreading the macroalgae. This gives us the opportunity to both actively help stop the spread and to teach others how to prevent spreading it. Additionally, the Collaborative members attend scientific conferences and present on both their findings and on the threat of starry stonewort, increasing awareness within the scientific community.

Finally, the Collaborative readily pursues the training and engagement of citizen scientists throughout the region. Staff members regularly meet with lake associations and other groups of citizen scientists to teach them how to monitor for SSW. Attendees are taught how to conduct and analyze rake tosses, how to identify starry stonewort, and how to best report their findings. In addition, the Collaborative assists the citizen scientists in utilizing what they've learned by supplying them with resources such as training materials and field kits. For those unable to meet in person or without a local collaborator able to perform the training, webinars can also be held to teach the same skills remotely.

References:

1. Karol KG, Sleith RS. 2017. Discovery of the oldest record of Nitellopsis obtusa (Charophyceae, Charophyta) in North America. Wood M, editor. J Phycol. 53(5):1106–1108. doi: 10.1111/jpy.12557 .
2. Larkin D, Monfils A, Boissezon A, Sleith R, Skawinski P, Welling C, Cahill B, Karol K. 2018. Biology, ecology, and management of starry stonewort ( Nitellopsis obtusa ; Characeae): A Red-listed Eurasian green alga invasive in North America. Aquatic Botany. 148. doi: 10.1016/j.aquabot.2018.04.003 .
3. Hackett R, Cahill B, Monfils A. 2017. State of Michigan’s Status and Strategy for Starry Stonewort (Nitellopsis obtusa (Desv. in Loisel.) J. Groves) Management.