by Lon Nordeen, MLSA Secretary; Rusty Gowland, Black Lake Preservation Society; and Kyle Chapman, Bass Lake Improvement Board
It is that time of year when people want to swim, wade, boat, and play in Michigan’s 10,000+ inland lakes. However, it is also the time when lake residents, boaters, and fishermen can detect greenish material along the shore or in the lakes they are trying to enjoy. Is this green material floating in the water a Harmful Algae Bloom (HAB)? Residents and boaters fear the answer might be yes, and then the lake team, local government, and health department might shut down use of part of the lake.
Every lake has unique conditions and approaches concerning HABs. Here are two perspectives from Michigan lake teams and what they are doing to identify and try and reduce HABs. At the end are recommendations from MI EGLE and the State Health Department on HABs.
Gary Kohlhepp, Chief of the Lake Michigan Unit of MI EGLE, says, “EGLE, as a state agency, responds to reports of harmful algal blooms on inland lakes as resources allow. It works with local health departments to perform testing to confirm local outbreaks of HABs. EGLE also works with the Department of Health and Human Services and local health departments to inform the public of results to keep our state waters safe for people, pets, wildlife, and farm animals. EGLE staff were at the Western Lake Erie Basin conference last week, where algal blooms, nutrient loading, and actions to improve water quality were discussed. EGLE appreciates the Michigan Lakes and Streams Association, other groups, and educational institutions that help educate Michigan residents on water issues and long-term water protection.”
Rusty Gowland commented:
Black Lake is a natural and well-preserved lake, so it was a big surprise to us when we started having reports of toxic algae blooms (HABs). Our prior knowledge of HABs came from reading about the summer of 2014 HAB blooms in Lake Erie that caused a “Do Not Drink” advisory for the city of Toledo, Ohio. These blooms were caused by very high nutrient loads coming from upstream and the shoreline from industry, agriculture, and urbanization. Certainly not something we needed to worry about, or so we thought.
We first noted blooms on our lake under cool temps, sunny skies, and calm winds in the fall of 2019, and we’ve had confirmed toxic blooms during the fall of most years since then. Initially, we addressed the basics of nutrient reduction in community outreach measures: Have a healthy septic, Avoid fertilizers, Build a shoreline buffer, and Self-assess your property with the Shoreland Stewards Self-Assessment Survey. The next thing we did was to execute a “mass balance” of phosphorus sources with the help of Kieser & Associates, LLC in Kalamazoo, Michigan. K&A demonstrated that we had normal to low loads of this critical nutrient from tributaries, the atmosphere, and stormwater, but an abnormal load from aging septic systems. This was demonstrated through groundwater testing between the drain fields of older systems and the lake shoreline. Furthermore, we learned that this load was showing up at the end of the summer and into the fall. Cottages had been in use for the summer, and leachate had been moving through our sandy soils and pulsing into the lake beginning in late August and continuing through mid-December. Fall winds can then mix the phosphorus beyond the shoreline. This peak load was timed with the late summer slowdown of our second biggest source, our tributaries, so it became pretty clear what was feeding our fall blooms.
The phosphorus “mass balance” proved a phosphorus spike in the fall from aging septic systems, and that was a good piece of information. But even with the spike, our phosphorus measures were low. Low enough that we are classified as an oligotrophic lake, so there was more to understand. K&A referred us to the work of Professor Mark Luttenton of the GVSU Annis Water Resources Institute (AWRI) to gain insights about the role of invasive mussels. We now believe that as these mussels filter out the “good algae” (ie, the green algae) through the growing season, it creates a great deal of space for cyanobacteria to utilize more of the available phosphorus to develop into large blooms. If the cyanobacteria in a lake have in their DNA the propensity to release toxins (as we do in Black Lake), the blooms will be Harmful Algae Blooms (HABs). Together, the pulse from aging septic systems plus zebra mussels explains how our oligotrophic lake could have blooms on cool, sunny, still fall days.
We have since shifted our focus from eliminating as much phosphorus as possible (not a practical goal when phosphorus is critical to the base of the food chain) to minimizing the fall pulse of phosphorus. Dr. Luttenton speaks of measures of “biomass” that explain how invasive mussels put in motion a set of complex interactions that cause many undesirable outcomes, not just HABs (e.g., weed expansion, crusty lake bottom sands, lake bottom algae and decaying organic matter, reduced fish survival, and DO depletion). These nuisance conditions manifest while delivering positive trophic status impacts! We are presently formulating our response to these ongoing changes as part of a Watershed Management Plan led by the Tip of the Mitt Watershed Council.
Kyle Chapman discussed an overview and review of his team’s HAB Responses:
Bass Lake is a multi-recreational 524-acre lake located primarily in Mason County. It is fed by three streams and multiple springs with one outlet to Lake Michigan controlled by a low-head weir. The resident community is engaged and vibrant. The Bass Lake Property Owners Association recently published a book that documents the lake’s history. This Is Bass Lake: A Destination for Generations mentions struggles with aquatic vegetation management from the early 1900s. The book is available on Amazon.
Over the years, the volunteer-based Bass Lake Property Owners Association used multiple avenues to try and manage the excessive vegetation growth, even to the point of purchasing their own harvester for the princely sum of $670 in 1928. By 2004, it was evident that due to the introduction of fast-growing invasive species, ever-changing State regulations, and rising costs, a more structured process was needed. In 2006, the Property Owners and Summit Township formed a Lake Improvement Board.
The lake is shallow, and the perimeter of the lake (Tier 3) is largely characterized by unproductive sands. The deeper portions of the lake, extending to the center of the lake (Tiers 4 and 5), are highly macrophyte productive. Cyanobacteria (blue-green algae) bloom conditions have been present in Bass Lake during many growing seasons over the past several decades. Harmful algal blooms (HABs) were not common in many Great Lakes Region inland lakes, but they were particularly conspicuous in Bass Lake in 2011. Bass Lake was among nearly a dozen LakeScan™-monitored lakes where a novel algaecide treatment strategy was deployed that could be conducted within the confines of the general permit restrictions placed on the use of all algaecides by the MI DEQ (now, MI EGLE). Only a portion of the lake water column was treated with a copper algaecide, where the intent was to increase the proportion of desirable over the predominant and potentially toxic cyanobacteria. Although this novel strategy provided immediate satisfactory results in other lakes, the significantly greater plankton biomass that was present in Bass Lake, relative to the allowed treatment area, was too great to achieve a successful treatment outcome. The plankton community was monitored and analyzed using LakeScan™ methods from 2011 to 2014, and these studies revealed that the cyanobacteria dominated the Bass Lake flora during this time.
Fortunately, obvious bloom conditions and the relative abundance of potentially toxin-forming cyanobacteria had diminished, and in 2014, sampling was curtailed. This was also a time when the density of bottom-dwelling, mat-forming (i.e., ground cover) large plant species (macrophytes) such as chara and coontail came to dominate the nutrient-rich sediments located in the central basin (Tiers 4 and 5) of the lake. Unremarkable conditions dominated the lake until 2019, when unusually high water levels in the Great Lakes and flooding deepened the lake to the point that macrophyte coverage of the bottom of the lake declined.
Previous water column nutrient level monitoring did not seem to indicate that the water column provided the resources for cyanobacteria blooms. Strongly suggesting that the sediments were the primary contributor of the nutrients that fueled the noxious blooms of cyanobacteria. When the macrophyte bottom cover declined in 2019, the production of sediment-associated, toxin-forming cyanobacteria exploded, resulting in high toxin concentrations in the northern part of the lake.
The Bass Lake Improvement Board elected to take action given the public health implications associated with the new USEPA guidelines. MI EGLE assisted with cyanobacteria toxin testing. Several treatment strategies were used to suppress the bloom conditions until a peroxide-based algaecide was injected at depth, resulting in a cessation of bloom conditions in August. This large-scale peroxide treatment was expedited and permitted by amendment by the MI EGLE, and, notably, the use of peroxide was more consistent with standard policies that were placed on the use of copper-based algaecides. This peroxide treatment, while very effective, came with significant costs, nearly doubling our typical annual expenditure.
Sporadic blooms have been present in the following years, but restricted to only narrow bands of floating cells that accumulate on leeward shores because of the wind. These can form and then dissipate very quickly. It appears that the recurrence and magnitude of the HABs are inversely related to the establishment of “ground-cover-like” macrophyte growth in the middle areas of the lake. Plant and chara growth in the central basin of the lake seems to restrict the amount of exposed sediment that can serve as a “nursery” to produce nuisance cyanobacteria blooms. Supporting evidence for this claim is provided by alarmingly high concentrations of cyanobacteria and cyanotoxins observed in mid-October 2021, when coontail and wild celery had commenced or completed the expected end-of-season decline.
Plant management efforts are focused on the preservation and expansion of chara and other desirable species in the Bass Lake central basin to prevent recurrent cyanobacteria blooms from forming and producing cyanotoxins. Surface mat-forming species, such as curly leaf pondweed and Eurasian watermilfoil, and watermilfoil hybrids that shade out lower-growing plant species while exposing sediments to produce PTOX benthic cyanobacteria are aggressively managed. LakeScan™ monitoring is used to document the biodiversity of the plant community and the percent of cover in the central basin of the lake.
As new information is revealed regarding the effectiveness of creating a barrier to the transfer of nutrients from the sediments to sediment nutrients dependent benthic algae, the Bass Lake Improvement Board has engaged Kieser and Associates (Kalamazoo) to complete a study of nutrient dynamics in the lake before considering one of these relatively new technologies. The goal of the LakeScan™ directed management program will still be to create a vibrant, stable, and diverse plant community that provides critical cover of lake sediments. However, the use of sediment nutrient interception will be considered for those areas in the lake where plant cover is sparse or growth is irregular. The study findings will be reviewed during the winter of 2025/2026.
Several members of the Bass Lake Improvement Board attend each of the Property Owners’ Association meetings to provide updates and field questions. The most common concern we hear in June is the presence of a light green coating along the shore, which is usually pollen concentrations. We’re glad they ask because it means our strongest saying for everyone, “If in doubt, stay out”, has been heard.