Climate change is expected to produce warmer and wetter conditions in the Great Lakes region. This environmental shift may enable the proliferation of certain invasive species and potentially introduce new ones, leading to significant ecological disruptions. Below is a look at both existing and potential future invasive species, detailing their origins, current presence in the Great Lakes, potential threats under changing conditions, possible control measures, and the role of plankton:

1. Asian Carp (Bighead and Silver Carp): Originating from Eastern Asia, these carp species have yet to establish themselves in Lake Michigan but are prevalent in the Mississippi River Basin. Concerns are growing that increased river flows and elevated temperatures might facilitate their movement into the Great Lakes via connecting waterways. Control measures include the implementation of physical barriers like the existing electric barriers and biological controls, such as releasing sterilized males to curb their spread. Asian carp are filter feeders that consume massive quantities of phytoplankton and zooplankton, potentially disrupting the food web and depleting resources needed by native fish and other aquatic organisms.

2. Hydrilla (Hydrilla verticillata): A highly invasive aquatic plant from Southeast Asia, hydrilla has not invaded the Great Lakes but is present in several U.S. states. Its potential to form dense underwater mats could significantly impact Lake Michigan's ecosystems, especially as warmer temperatures could prolong its growing season. Control measures focus on early detection and rapid response strategies, including applying aquatic herbicides and mechanical removal to prevent establishment. Dense hydrilla growth can alter water flow and light penetration, affecting plankton dynamics and, consequently, the entire aquatic food web.

3. Quagga and Zebra Mussels (Dreissena bugensis and Dreissena polymorpha): Native to Eastern Europe, these mussels have firmly established themselves in the Great Lakes. They disrupt ecosystems by altering food webs and clogging water intake structures. Warmer waters may increase their reproductive success. Control measures involve chemical treatments, manual removal, and exploring the potential of introducing species-specific pathogens or parasites to manage populations. By filtering out large amounts of plankton, these mussels can significantly reduce the availability of primary food sources for native species.

4. Round Goby (Neogobius melanostomus): This benthic fish from Eastern Europe is already prolific in Lake Michigan and competes with native species for resources. Warmer waters might enhance its reproductive capabilities. Control measures include targeted fishing, habitat modifications to disrupt nesting, and educating the public about preventing the spread through ballast water and other means. Round gobies also disrupt the food web by preying on benthic invertebrates, which are crucial for nutrient cycling and plankton dynamics.

5. Water Chestnut (Trapa natans): Although not currently found in Lake Michigan, this plant from Eurasia and Africa could invade, particularly in nutrient-rich runoff areas. It forms dense floating mats that degrade water quality and disrupt aquatic life, potentially exacerbated by warmer, wetter conditions. Control measures include mechanical removal and controlled herbicide use if detected early. The dense canopy formed by water chestnut can lower oxygen levels and light availability, stifling plankton growth and affecting the entire aquatic ecosystem.

6. Sea Lamprey (Petromyzon marinus): These parasitic fish, originally from the Atlantic Ocean, have a longstanding presence in the Great Lakes. They significantly impact fish populations. Potential climate changes might extend their active periods and enhance reproduction. Control measures include using lampricides, installing barriers to prevent upstream migration, and trapping during spawning migrations. Sea lampreys reduce fish populations that are crucial consumers of zooplankton, thus potentially allowing plankton populations to increase unchecked, which can lead to imbalances in nutrient dynamics.

7. Eurasian Watermilfoil (Myriophyllum spicatum): This plant, native to Eurasia, forms dense underwater beds in the Great Lakes, displacing native vegetation and altering habitats. Warmer temperatures and increased nutrient runoff could facilitate its spread. Control measures involve the use of aquatic herbicides, introduction of milfoil-eating weevils, and mechanical harvesting. Dense growths of watermilfoil can decrease water flow and light, negatively impacting plankton populations and, by extension, the food web structure.

Potential New Invasive Species to Monitor:

- Golden Mussel (Limnoperna fortunei): Native to China and Southeast Asia, this mussel could become a new threat, similar to quagga and zebra mussels, capable of significantly disrupting ecosystems by filtering substantial amounts of plankton.

- Killer Shrimp (Dikerogammarus villosus): This predatory shrimp from Eastern Europe could dramatically change food web dynamics if it invades Lake Michigan, potentially affecting plankton populations by altering the populations of plankton consumers.

References:

- Great Lakes Environmental Research Laboratory. (2020). "Asian Carp and the Great Lakes Region." Environmental Impact Studies.

- National Oceanic and Atmospheric Administration. "Potential Impacts of Climate Change on Freshwater Invasions." Climate Research.

- Michigan State University Extension. "Hydrilla: A New Aquatic Invader to Watch." Aquatic Invasive Species Alert.

- Great Lakes Fishery Commission. "The Economic and Environmental Impact of Quagga and Zebra Mussels." Annual Report on Invasive Species.