Friday, September 7, 2012

Let’s Talk Science! Field scientist studies biocontrols in lake systems

by Joye Redfield-Wilder, communications manager, Central Regional Office

Aquatic plant specialist Jenifer Parsons has a unique position in Ecology. Jenifer’s interest in science sent her on a path to receive a bachelor’s degree is in biology from Boise State and a master’s in environmental science with an emphasis in aquatic ecology from Western Washington University. Aquatic plants and aquatic bugs were the focus of her studies, so with good timing and good luck her field of study landed her the perfect job at Ecology.

Her summers are spent monitoring aquatic plant populations in the state's lakes and large rivers, conducting research on the effectiveness of various aquatic weed control methods. During the fall and winter she compiles, digests, and summarizes her findings. Her position is funded through license tab fees for boats and recreational watercraft.

Weeds are the bane of our state's lakes. Not only does the prolific growth of non-native plants choke out other useful native species, their growth is a nuisance interfering with recreational activities such as swimming, fishing and boating across the state.

Jenifer has been pursuing one such pesky plant, Eurasian watermilfoil, for the better part of a decade. She’s been working to employ Mother Nature to battle the invading species that can quickly dominate a water body and put it out of balance.

Biocontrols can beat back invaders

Introducing biological controls is an attempt to use natural defenses to beat back an invader and provide an opportunity for native plants to regain a foothold and restore the natural balance.

A weevilholdon snacking on milfoil
Biological controls haven’t always been the best solution for an invasive problem. There were some notable disasters in the early days of this practice – think of the 1930s release of Central American cane toads in Australia. Instead of eating the beetles destroying the local cane crop, the toads proliferated with no known predators and devastated local biodiversity.

“Since then biocontrol has come under much tighter restrictions. In the U.S., insects or diseases must undergo stringent testing overseen by the U.S. Department of Agriculture to ensure they only survive and reproduce on the one weed that is being targeted. This ensures what is introduced will not then become a pest itself," Jenifer said.

Watermilfoil is a problem in Washington, much of the U.S. and southern Canada. But it isn't a problem everywhere. This phenomenon was first noticed in the Northwest in the 1980s in the Okanagan Lakes of British Columbia. Studies showed several plant eating insects were causing milfoil declines.

In Washington, Jenifer has been studying native "bugs" as prospective deterrents to the spread of milfoil – the milfoil midge being one found in the Okanagan Lakes. They have proven difficult to rear for introduction elsewhere. Among others were the larvae of the caddisfly, moth larvae, and beetles.

In combination these predators can keep milfoil at bay. But only if there is an abundant population of bugs, she found. Unfortunately, in Washington the panfish, such as pumkinseed and bluegill, prey on the weevils and larvae, reducing their chances to be successful as a biocontrol where these predators thrive.

Caddisfly larva feast on milfoil plants.

Many factors affect controls

Native insects are controlling Eurasian milfoil in some lakes in the central part of the state where they are prolific and predators are few. However, there are times when the herbivores don't thrive and milfoil resurges. Predators play a role, but so does severe weather, water quality conditions and plant quality.

Jenifer also notes that aquatic plants are at the bottom of the food web – insects eating those plants are food for the small fish that may be eaten by the bigger fish or fish-eating bird. Plant-eating swans and geese also are a part of the chain influencing aquatic plant growth.

Ultimately, lake managers like Jenifer see this information as a valuable step toward reducing invasive plant growth. Plant-eating insects and other invertebrates may someday be enlisted along with nutrient reduction and support of the natural food chain to sustain healthy lakes.

You can read her full report online

More information on the lake efforts nationally

What you can do

Prevent the spread of aquatic invasive species while boating:
  • Rinse anchors and anchor chains during retrieval to remove organisms and sediments at their place of origin.
  • Remove fouling organisms from hull, piping, and tanks on a regular basis and dispose of any removed substances in accordance with local, state and federal regulations.
  • Do not dump bait and live well water. Those both pose significant threats.
  • Clean all watercraft and fishing equipment. Even the kayaker or jet skier should clean their watercraft to stop the spread of invasive species.
If you think you have spotted an invasive species you can report sightings:

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