In 2024, the GLA’s use of aerial drone-guided underwater Remote Operating Vehicles (ROVs) revolutionized our surveillance program and allowed aquatic vegetation mapping of the bottomlands of the Glen Lake/Crystal River (GL/CR) Watershed for the first time.
While the first goal of using the ROVs was to discover and document outbreaks of Eurasian watermilfoil (EWM) in Little Glen Lake, another major goal was to find plant/animal associations that align with EWM. In other words, we wanted to learn what aquatic plants grow and what aquatic animals are present around EWM colonies. Using optical data gathered from 65 locations around the GL/CR Watershed, a biological map of unprecedented detail was generated that showcases all macroscopic plants (flora) and selected animals (fauna), such as freshwater sponges, bryozoans, and a variety of fish species. This baseline data significantly increases our ability to successfully search for EWM and other invasive species in the coming decade.
After a massive amount of underwater digital imagery was accumulated during July-September 2024, a follow-up biological analysis was conducted. Questions were raised about learning more about species richness, spatial distribution, and biological community structure. With the improved knowledge of the spatial distribution of aquatic flora and fauna at the bottom of the waters in the GL/CR Watershed, we can better predict how to locate and track initial outbreaks of important invasive species such as EWM.
After frame-by-frame reviews of the video files, a total of 536 aquatic species observations for the 65 survey sites were assigned specific GPS coordinates. Once all the 65 survey sites were reviewed and evaluated for the presence or absence of EWM, the same digital footage was further evaluated for species richness (i.e., the number of species) of macrophytes (aquatic plants large enough to be seen by the naked eye) and aquatic fauna including sponges, bryozoans, and fishes. In addition, all species were georeferenced and viewed in Google Earth Pro based on GPS coordinates for each underwater camera deployment.
In addition to locating EWM in the central Little Glen Lake basin, this baseline study revealed a total of 38 aquatic species in our watershed (22 macrophyte species and 16 species of sponges, bryozoans, fishes and turtles). This demonstrates the diversity of aquatic plant communities that provide important habitat and food web support for fishes and other aquatic animals and generally points to the health of our lakes. Furthermore, occurrences of 12 species of fauna were observed, including specific georeferencing to determine spatial distribution.
The information gleaned from geolocated optical digital videos has allowed confident identification and has provided a link of each species in this study to exact GPS coordinates. The methodology employed in this study will be particularly useful in the future to track changes in the distribution and abundance of both native and invasive plant and animal species. Now that this baseline has been established, additional studies in future years will set the stage for trendlines to emerge.
The results revealed that all four EWM sites share the following plant associations that were found together: Chara, Water Celery, Sago Pondweed, and Flat-stem Pondweed.
In addition, all EWM sites shared the following species of fishes: Bluegill, Pumpkinseed, Largemouth Bass, Smallmouth Bass, Rock Bass, and Yellow Perch.
The expert, novel data gathering of this study would not have been possible without the leadership and skill set of GLA Watershed Biologist Rob Karner, Zero Gravity, LLC owner Dennis Wiand, and Wiand’s ROV pilot Sean Courson. Ron Reimink’s experience and wisdom in guiding this study was appreciated. Helpful edits were offered by Dr. Stephen Hamilton, retired Michigan State University Professor. Special thanks to GLA staff Laura Wiesen and Joe Blondia and intern Suha Augenstein for their help in collecting underwater digital video of the added survey sites of Big Glen Lake, Fisher Lake, and the Crystal River. Finally, special thanks to Victoria Velting for making the extra effort to be observant of the shoreline adjacent to the boat ramp and investigating the washed up EWM and communicating her findings in a prompt manner.
