Monitoring, Educating and Slowing the Spread of Invasives

Carol Warden, our aquatic invasive species specialist up at Trout Lake Station sent in this note about her work “up north” this summer.

With summer well underway, aquatic invasive species (AIS) are once again a hot topic in the Northwoods. With things like rainbow smelt, Eurasian water milfoil and rusty crayfish moving in to Wisconsin’s inland lakes, there’s a lot to talk about.

Carol introduces visitors of Trout Lake Station's Annual Open House to local aquatic plants. Photo: A. Hinterthuer
Carol introduces visitors of Trout Lake Station’s Annual Open House to local aquatic plants. Photo: A. Hinterthuer

Education and monitoring are two important aspects to keeping invaders in check. Throughout the year I teach kids and adults alike about the importance of preventing AIS and not letting them hitch a ride with us from lake to lake.  I also illustrate every-day techniques that we can use to keep our boats, and therefore our lakes, free of AIS.
But during the summer is when things kick into high gear.  It’s nonstop sampling, monitoring and educating from May through September.  Most of this time is spent on beautiful northern lakes (tough gig, I know) and the rest of this time is spent either in the lab or in the classroom.

Two of my main monitoring responsibilities are aquatic plant surveys and spiny water flea monitoring.
Some people colloquially refer to aquatic plants as “seaweed” but my team and I like to keep it real with the less negative moniker of “aquatic plants.” (Or “macrophytes” if you want to get really fancy).
The spiny water flea is an invasive zooplankton that actually acts as a predator to native zooplankton.  These invasions have potential impacts on food webs as spiny water fleas eat what baby fish would eat but don’t really serve as a substitute diet.  They could also have negative implications on water clarity.  As they eat native zooplankton, there are fewer native species to eat up all the algae.

Using the long-poled metal rake, Carol collects macrophyte (aquatic plant) samples from a northern Wisconsin lake. Photo: Carol Warden
Using the long-poled metal rake, Carol collects macrophyte (aquatic plant) samples from a northern Wisconsin lake. Photo: C. Warden

For each aquatic plant survey, I gear up with some metal rakes, a few data sheets and a crew of three surveyors and head out to a number of regional lakes.  The lakes are matched up with a GPS grid so my crew can sample evenly spaced points throughout the entire lake.  From that, we determine what types of aquatic plants are present and how abundant they are.  This includes all native and any invasive species.  With this information we can calculate how healthy the lake is (some plants need really clear water and very little pollution to grow) and to what extent any invasive species may be taking over.
For spiny water flea sampling, I head out with a whole different set of tools including a large, cone-shaped net.  The top of the net is open, just like an ice cream cone, and the bottom of the net is affixed to a removable cup made of some PVC pipe with holes drilled on the side.  Mesh used of the same material as the net covers these holes.
From a boat, I drop the net to the depths of the lake and pulls it vertically through the water column.  The net allows water to drain out but catches any little critters that are hanging out in the water where I sample.  With this sample I can calculate abundance of native and invasive zooplankton and also determine if any changes in population are occurring within this microscopic community.
As a plankton net is pulled through the water, plankton are caught and washed into the canister at the bottom of the net, then collected for sampling and ID. Photo: Carol Warden.
As a plankton net is pulled through the water, plankton are caught and washed into the canister at the bottom of the net, then collected for sampling and ID. Photo: Carol Warden.

Equipped with all this information on the effects of an aquatic invasive species invasion, I then go to area classrooms and share everything I’ve learned.  Luckily, AIS seems to be something that grabs the attention and interest of just about everyone in the Northwoods.
So next time you see someone out on the lake who looks to be geared up with anything but traditional fishing gear, give them a shout and ask what they’re up to. You may learn all sorts of things about that lake and get to see a little limnology in action.
Thanks to Conserve School for producing and sharing the video. For more on Carol’s work, and other projects on station, go here.

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