STARRY STONEWORT IS AN ALGA - AND AN INVASIVE SPECIES IN INLAND LAKES AND PONDS THAT CAN DRAMATICALLY ALTER AQUATIC ECOSYSTEMS.
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Its growth and expansion since the 1990’s throughout New England and Minnesota has served to destabilize critical ecosystem functions and impair recreational and utilitarian values. Invasive species, like starry stonewort, can reduce property values for the property owners in these riparian areas.
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The most significant characteristic of this species
is that it is predictably unpredictable.
It will bloom and decline without warning.
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Dr. Douglas Pullman, Sr. Aquatic Plant Scientist
Applied Biochemists |
Ecosystem ImpactsStarry stonewort reproduces rapidly, and is one of the most aggressive aquatic invasive species. It is able to outcompete other aquatic plant species, including all other non-native, noxious and invasive plants. However, there are several plant species that seem to thrive cohabitating in the presence of starry stonewort, such as rootless bladderworts, coontail and sometimes water lilies.
The visual impact starry stonewort has on water clarity is profound and water clarity is often excellent in lakes where it is dominant. However, it can also indirectly and adversely influence the plant and animal life beneath the water surface. Starry stonewort can spread quickly from lake to lake by producing specialized fragment and structures known as bulbils that are easily transferable on the fur of animals and on bird feathers. Plants and plant parts can get caught on boat trailers and are transferred by humans. It is an opportunistic species that can make a substantial and damaging impact on the surrounding ecosystems with its unforeseeable bloom and crash cycles that can happen at what seems to be random times throughout the year. Blooms extirpate desirable plants and compromise critical aquatic habitats. Crash events leave voids in in the plant community that can be rapidly filled by other weeds or trigger cyanobacteria blooms depending on the size of the crash event. |
Effect of starry stonewort on water clarity. Also note the smooth appearance of the mounds of starry stonewort, approximately 2’ below the water surface.
Specialized fragments that aid in dispersal of starry stonewort bulbils “stars”.
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Classification
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The charoid algae look like higher plants because they seem to have stems and branches, but they are indeed algae and members of the characea.
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The charoid algae look like higher plants because they seem to have stems and branches, but they are indeed algae and members of the characea. There are 6 extant (living – there are many fossil genera) genera in this family. They include:
There are dozens of charoid algae species in the Northern US, Chara being the most common genus. |
How to Identify Starry Stonewort
Starry stonewort can be difficult to identify because it may grow inconspicuously and intermingled with other similar charoid species.
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A Historical Account
And Lessons Learned
A mysterious form of “chara” seemed to have appeared for near shore property owners in an increasing number of southeastern Michigan lakes during the late 1990’s. Numerous reports of three-foot-tall “chara” that made dock access nearly impossible began to surface. During most of the 1990’s, these reports were largely ignored because the charoid algae were always considered to be a highly desirable part of typical Michigan inland lake floras. It was rarely targeted for treatment and its growth was usually encouraged. However, it had become such a significant problem that a charoid algae treatment was planned for a small portion of a SE Michigan inland lake in the midsummer
of 1999.
The objective of the treatment was to merely “burn the charoid algae back” to an acceptable height and provide reasonable access to the lake for the homeowners on that bay. Since the goal of any reasonably managed lake is always to protect or improve plant community diversity, it was also hoped that this treatment would relieve some of the excessive competitive pressure that the “mysterious” charoid algae were having on the few remaining desirable plants that were still present in the bay.
The applicator, only wanting to reduce the height of the algae, applied a “lower than normal” dose of algaecide to the areas in that bay where docks were located. The treatment was limited in scope despite the observation that the mysterious charoid algae had blanketed the bottom of all but the deepest parts of the bay. To the applicator’s surprise, all of the charoid algae died and collapsed throughout the entire bay within 48 hours of the treatment. Particularly unexpected since chara algae can be difficult to control.
Later, they discovered that the algae was not your typical Chara, but starry stonewort. An algae that appeared extremely sensitive to aquatic pesticides. The discovery of starry stonewort and positive identification of the plant in 2006 should serve as an important lesson to everyone who shares a concern with the spread of invasive species in all lakes, that it is critically important to pay attention to the reports of lay persons and lake management practitioners, even when the reports seem to contradict long held beliefs.
of 1999.
The objective of the treatment was to merely “burn the charoid algae back” to an acceptable height and provide reasonable access to the lake for the homeowners on that bay. Since the goal of any reasonably managed lake is always to protect or improve plant community diversity, it was also hoped that this treatment would relieve some of the excessive competitive pressure that the “mysterious” charoid algae were having on the few remaining desirable plants that were still present in the bay.
The applicator, only wanting to reduce the height of the algae, applied a “lower than normal” dose of algaecide to the areas in that bay where docks were located. The treatment was limited in scope despite the observation that the mysterious charoid algae had blanketed the bottom of all but the deepest parts of the bay. To the applicator’s surprise, all of the charoid algae died and collapsed throughout the entire bay within 48 hours of the treatment. Particularly unexpected since chara algae can be difficult to control.
Later, they discovered that the algae was not your typical Chara, but starry stonewort. An algae that appeared extremely sensitive to aquatic pesticides. The discovery of starry stonewort and positive identification of the plant in 2006 should serve as an important lesson to everyone who shares a concern with the spread of invasive species in all lakes, that it is critically important to pay attention to the reports of lay persons and lake management practitioners, even when the reports seem to contradict long held beliefs.
Ways to Control Starry Stonewort
Aquatic vegetation management programs should plan to preserve, protect and possibly improve the diversity of macrophytes communities. A well planned program serves to preserve and improve the recreational and aesthetic qualities of managed lakes. Choosing lake management tools that provide the most species specific control should be a focus.
Starry stonewort grows to form extremely dense carpets completely covering the bottom of lakes, making control difficult.
Mechanical methods are generally not able to keep up with the rapid growth of starry stonewort when it is in bloom phase. Desirable plants are also damaged when areas are mechanically harvested. Starry stonewort, being an opportunistic weed, can capitalize on this mechanical disturbance and dominate at even higher levels. Mechanical harvesting can also serve to spread propagules to other parts of the lake that are not already infested.
Hand harvesting creates a mechanical disturbance of surrounding areas that will favor starry stonewort production. It will not be beneficial for more desirable and ecologically conservative species. Hand harvesting is also dependent upon visual location of the plant. Because starry stonewort can grow undetected amongst other charoid algae, it would seem unwise to depend on this strategy as a viable method to protect the biological diversity of submersed plant communities.
Chemical control allows for selectively targeting with algaecides, maintaining biological diversity. This can allow infected water bodies to be preserved and in some cases, improved.
Starry stonewort grows to form extremely dense carpets completely covering the bottom of lakes, making control difficult.
Mechanical methods are generally not able to keep up with the rapid growth of starry stonewort when it is in bloom phase. Desirable plants are also damaged when areas are mechanically harvested. Starry stonewort, being an opportunistic weed, can capitalize on this mechanical disturbance and dominate at even higher levels. Mechanical harvesting can also serve to spread propagules to other parts of the lake that are not already infested.
Hand harvesting creates a mechanical disturbance of surrounding areas that will favor starry stonewort production. It will not be beneficial for more desirable and ecologically conservative species. Hand harvesting is also dependent upon visual location of the plant. Because starry stonewort can grow undetected amongst other charoid algae, it would seem unwise to depend on this strategy as a viable method to protect the biological diversity of submersed plant communities.
Chemical control allows for selectively targeting with algaecides, maintaining biological diversity. This can allow infected water bodies to be preserved and in some cases, improved.
Starry stonewort grows to form extremely dense mats making mechanical control difficult.
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Starry stonewort reproductive structure called an antheridia.
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Starry stonewort thallus (stem) that has been partially emptied of cellular contents. Note the appearance of the empty cell parts.
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Application Tips for Starry Stonewort
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Cutrine® Ultra has been shown
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