Research Brief: Understanding Aquatic Invasive Species Characteristics and Impacts in the Great Lakes

The Laurentian Great Lakes are one of the most invaded aquatic systems in the world, supporting about 188 documented aquatic nonindigenous species (ANS). While some of the ANS are invasive, meaning that they are harmful to native species, others are benign or even beneficial. 

Historically, the ANS’ likelihood to become harmful and invasive has been associated with the invader’s life histories, behavioral factors, and their impacts on the environment. However, there’s a lack of data that analyzes invasive species together to specifically examine their shared characteristics. 

A 2024 study published in the Journal of Great Lakes Research identified and quantitatively ranked ANS in the Great Lakes from highest to lowest impacts by analyzing previously collected data and using an organism impact assessment (OIA) tool developed by the Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS).¹

The goal of the study was to figure out which ANS are most harmful to environmental and socio-economic health in order to create an archetype invader, prioritize limited restoration resources, and predict future invasive species to prevent their continual spread. 

Methods 

Researchers began by analyzing and reformulating GLANSIS’ list of ANS using the OIA tool and previous research to create a list ranking ANS from greatest to least negative impacts. Once they found the top ten most harmful invasive species, they examined various pieces of research literature to assess the specific magnitude of each invasive species’ impact.

Detecting 12 primary impact categories, researchers split them into two sections–environmental and socio-economic–in order to quantitatively score invaders’ effects against one another. 

The environmental impacts affect biotic and abiotic components of the ecosystem after invasion, including:

1. Environmental health
2. Competition
3. Predator-prey relationships 
4. Genetics
5. Environmental water quality 
6. Physical ecosystem 

The socio-economic impacts affect individual or societal values after invasion, including:

1. Human health
2. Infrastructure
3. Water quality for human use
4. Economy
5. Recreation
6. Aesthetics 

Each species was scored and given an impact level of none (0), moderate (1), high (6), or unknown (U). Scores were then summed up in each of the 12 impact categories, giving all species a total impact count. Species with a score of 2 and above were considered invasive. 

Invaders were then examined based on common characteristics such as taxonomic groupings, continent of origin, and form of introduction using chi-square analysis to determine if all the Great Lake’s invaders could be represented by the top ten invaders’ qualities or not. 

Results 

Results show that out of the 188 detected ANS in the Great Lakes region, 78 nonindigenous species were considered invasive, and the top ten invaders all had strong impacts in multiple categories with scores greater than 20.

The study determined that Laurentian Great Lakes’ top ten most invasive species are: zebra mussels, quagga mussels, alewife, sea lamprey, Japanese stiltgrass, grass carp, water chestnuts, common reed, round goby, and white perch.¹

The analysis suggests that only one characteristic represents the top ten invaders, and the lower-ranking invaders showed no clear similarities in characteristics or impacts. Each invader affected the 12 impact categories differently. 

The top ten invaders’ common characteristics don’t represent the majority of invasive species. The only similar characteristic was the continent of origin, showing that most invaders came from Eurasia. 

Out of the top ten invaders, all altered predatory-prey relationships; nine affected environmental health, competition, recreation, the economy, and aesthetics; six affected the physical ecosystem; five affected water quality for human use; four affected environmental water quality and human health; three affected infrastructure, and two affected genetics.  

Taxonomic groupings differed because the top ten invaders were primarily fish, and a majority of all invasive species were plants. The forms of introduction were different because the top ten invaders mostly traveled by ballast water, while the majority of other invaders were introduced through deliberate release. 

With unanticipated results, researchers cannot predict if a new species will become invasive, nor were they able to create an archetypal invader. However, the objective quantitative cross-taxa ranking can still be a reference point for educators, communicators, and managers to find more effective conservation and restoration efforts in the Great Lakes. 

Although the research reflects most previously published literature, researchers suggest taking a closer look at ANS’ behavior and the history of their past impacts.

Sources

1. Lower, E., Sturtevant, R., Iott, S., Martinez, F., Rutherford, E., Mason, D. M., Redinger, J., & Elgin, A. K. (2024). The Great Lakes’ most unwanted: Characterizing the impacts of the top ten Great Lakes aquatic invasive species. Journal of Great Lakes Research (Vol. 50, Issue 4, p. 102365). Elsevier BV. https://doi.org/10.1016/j.jglr.2024.102365