Tiny invasive organism a big threat to our lakes

Even though there are signs at public boat launches warning of invasive species including the spiny water flea it is hard to appreciate the damage this tiny organism can do until you comprehend its impact on the ecosystems of our lakes. Anyone who appreciates the sparkling clear lakes of the Haliburton Highlands needs to know about this intruder and how to limit its spread.

Because of their voracious appetites their lack of predators and their ability to survive extreme conditions a few of these tiny non-native organisms can overturn the native plankton population the backbone of the aquatic food chain. The good news is they can’t survive five to six hours of thorough drying in sunlight.

Dr. Norman Yan a highly regarded biologist who spoke at the AGM of Environment Haliburton this spring has studied spiny water fleas extensively. He states that they “are the greatest threat to the biodiversity and structure of native zooplankton communities in lakes on the Canadian Shield since acid rain.”

Bythotrephes longimanus or spiny water flea is native to freshwaters of northern Europe and Asia and was accidentally introduced into the Great Lakes through ballast waters of ocean-going ships in the early 1980s. It has spread to other lakes in North America including 150 inland lakes in Ontario at least two being in the Haliburton Highlands. This accidental spread is attributed to boaters and fishermen. The Spiny Water Flea gets caught up in fishing lines downriggers nets and other equipment such as anchors and ropes and appear as gelatinous globs on equipment. They can also be unintentionally transported in bilge water bait buckets or live wells.

“They have a huge impact on the diversity and size structure of the animal plankton and can drive several species to apparent extinction in our lakes” Yan says. Not only does this mean that small fish have less native plankon to eat but they also can’t eat the spiny water flea because of the barbs on the long spiny tail. Large fish that do eat it have difficulty passing the organism and can have their stomach linings and intestines punctured by the spines. Unless you are a fisherman you may not be aware of the spiny water flea as it tends to spend daylight hours in the deeper cooler areas of the lake and rises to the surface at night.

The spiny water flea can survive chlorination salination heat and freezing. However Yan says that the spiny water flea dies within approximately five to six hours of desiccation in sunlight and therefore this is the most important means of controlling it. The world’s leading authority on the spiny water flea is Dr. D. K. Branstrator who states that if people limit their usage of lakes to one lake a day and that they dry their equipment thoroughly during intervening periods this should help limit range expansion of the organism.

In addition to drying equipment thoroughly the Ontario government website www.invadingspecies.com suggests that fishermen and boaters learn how to identify the spiny water flea and how to avoid spreading them.

Some tips:

-Inspect your boat trailer and equipment after each use

-Remove all plants animals and mud before moving to a new water body

-Drain water from your motor live well bilge and transom wells while on land.

-To be sure that you don’t introduce any invasive species from lake to lake rinse all recreational equipment with high pressure (>250 psi) or hot (50 C/122F) or let dry in sun for at least five days.

-If you see an invasive water flea or other invasive species in the wild contact the toll free Invading Species hotline at 1-800-563-7711 or visit www.invadingspecies.com to report a sighting.

Thank you to Dr. Norman Yan for his help with this article.

Submitted by Susan Hay a member of Environment Haliburton Haliburton Highlands Field Naturalists and Miskwabi Area Cottager’s Association.