From the SLA: HABs and the impact of invasive species

From the SLA: HABs and the impact of invasive species

Submitted by Paul Torrisi and Charles Driscoll, Ph.D.

In a recent publication (May 2021) of Ecosphere, a scientific journal of the Ecological Society of America, the clear causal link between zebra/quagga mussels (mussels) and toxic algal blooms, also known as harmful algal blooms (HABs) was reviewed, emphasized, and confirmed.

In this special feature article on Forecasting Earth’s Ecosystems with Long-Term Ecological Research, scientists from Michigan State University discussed how the changing climate affects the relationship between zebra/quagga mussels (one of many aquatic invasive species that have invaded regional fresh waterbodies in recent years) and the proliferation of blooms of cyanobacteria (Microcystis), one of the microorganisms causing HABs.

This study was initiated after the arrival of zebra/quagga mussels in Gull Lake, Michigan, in the early 1990s, around the same time they were discovered in abundance in Skaneateles Lake, locally. Both lakes are characterized by very low water column nutrient concentrations. Soon after mussel arrival on Gull Lake, a surprising number of summer blooms of toxic cyanobacteria were observed. HABs are often associated with more nutrient-rich waterbodies. However, observations in Gull Lake prompted researchers to subsequently examine whether the introduction of mussels might have caused a shift in algal (microscopic photosynthetic organisms) composition toward this undesirable species.

A series of experiments were conducted over many years that firmly established a clear causal link between invasion by zebra/quagga mussels and an increase in the late summer phytoplankton community dominated by Microcystis. Interestingly, the researchers also demonstrated that this link is strongest in lakes with low phosphorus concentrations such as Skaneateles, and therefore with normally low concern for Microcystis. Additionally, the scientists found that the concentration of toxin, or microcystin, produced by the Microcystis increased in lakes colonized by mussels, particularly when nitrogen is abundant, whether derived from farm fields, residential septic systems, lawn fertilizers, or even atmospheric deposition.

Since zebra/quagga mussels are firmly established throughout the sediments of Skaneateles Lake and there is no effective way currently to remove them, what approaches could be applied to control HABs?

Once an invasive is introduced and established in a lake, it’s virtually impossible to eradicate. Prevention of introductions is the best option. The Skaneateles Lake Association (SLA) sponsors a Watercraft Stewardship/inspection Program at all boat launches.  This program needs to be supported and even intensified to keep additional mussels and hundreds of other invasive species (including the “monster” hydrilla) from entering Skaneateles Lake from neighboring waterbodies and the Great Lakes/Barge Canal system.

The highly successful SLA annual control of Milfoil is now in its 15th year.  The occurrence of milfoil (and mussels) demonstrates the costs and impacts of invasives.  The Milfoil program needs to continue, not only to keep Skaneateles Lake aesthetically clear and beautiful, which helps to maintain the economic integrity of the region, but also lessen these nutrient-rich plants from proliferating and dying in the lake, potentially increasing rich sources of nutrients for the HAB -causing cyanobacteria.

Finally, everyone living in the communities surrounding the lake needs to “step up their game” in preventing nutrients from entering our water supply. Households need to take a close look at what they (or hired services) are applying to their lawns and gardens, what goes down their drains (wastewater and storm), and how their septic systems are functioning and maintained. Folks should consider planting more trees and shrubs and think twice before removing any healthy ones.  Less lawn and more beds planted with native species should be advocated and admired.

Municipalities need to prevent contamination from the sanitary sewer system from entering their storm drainage during storm events. Road ditches and culverts should be meticulously maintained to prevent nutrients and salt from flowing directly into the lake or its feeder tributaries.

We urge that farmers participate in the SLWAP (Skaneateles Lake Watershed Agricultural Program) by implementing BMPs (Best Management Practices) supported by the City of Syracuse and from grants awarded to the Onondaga County SWCD (Soil and Water Conservation District).

Even though mussels and milfoil are destined to remain in the lake, we can certainly do much to control and diminish their impact on HABs now and into the near future. It’s up to all of us living in the watershed, and from folks and institutions in the entire CNY region to support the efforts of the SLA, other non-profit organizations, and governmental institutions, with all these endeavors to help keep the lake “clear and pure.”

SLA programs like Milfoil Control and Watercraft Stewardship are expensive, costing hundreds of thousands of dollars annually. However, they are  well worth the sacrifice of the many who join and contribute as members every year to keep them going.

Please check the active member/donor list on the SLA website, SkaneatelesLake.org, to be sure you’re active and included. If not, please consider joining or rejoining at SLA, P.O. Box 862, Skaneateles, NY 13152 or online at SkaneatelesLake.org.